Reaming

[Fortunat1[_12_]]

Another stupid question!

Been reaming holes in a few 4130 plates. The reamer worked fine for about
20 holes and then the holes started getting a bit smaller to the point the
bolts got a bit snug.
In my ignorance I thought this one hand reamer would pretty much last me
the whole project, but it's obvious I'm going to need a half a dozen of
them at least just to do the wing hardware.
I did a bit of searching on the net and found some info on reamers. All
hand reamers seem to be HSS which would put me back in the same boat I'm
already in so I was tempted by the carbide reamers I saw for sale.
So, my question is; can you use a carbide tipped reamer designed for use in
a lath in a simple drill press effectively? Or, for that matter, can you
use a reamer designed for use in a lathe as a hand reamer?
Or am I just barking up the wrong tree altogether?

By the way, just for info, the holes I've beenreaming are 5/16 and 1/4. The
material is .090 4130 and the holes were all laser cut about 1/64
undersize. I would ream the first hole in each plate and then clamp
together the plates in pairs to ensure accurate alignment of the holes in
each pair of plates.
Just in case it's not the reamer's fault at all!

[Orval Fairbairn]

In article >,
Fortunat1 > wrote:

> Another stupid question!
>
> Been reaming holes in a few 4130 plates. The reamer worked fine for about
> 20 holes and then the holes started getting a bit smaller to the point the
> bolts got a bit snug.
> In my ignorance I thought this one hand reamer would pretty much last me
> the whole project, but it's obvious I'm going to need a half a dozen of
> them at least just to do the wing hardware.
> I did a bit of searching on the net and found some info on reamers. All
> hand reamers seem to be HSS which would put me back in the same boat I'm
> already in so I was tempted by the carbide reamers I saw for sale.
> So, my question is; can you use a carbide tipped reamer designed for use in
> a lath in a simple drill press effectively? Or, for that matter, can you
> use a reamer designed for use in a lathe as a hand reamer?
> Or am I just barking up the wrong tree altogether?
>
> By the way, just for info, the holes I've beenreaming are 5/16 and 1/4. The
> material is .090 4130 and the holes were all laser cut about 1/64
> undersize. I would ream the first hole in each plate and then clamp
> together the plates in pairs to ensure accurate alignment of the holes in
> each pair of plates.
> Just in case it's not the reamer's fault at all!

Did you use cutting oil? Even plain old lubricating oil helps a lot and
keeps the tool cool.

[StanKap[_2_]]

The problem is hardening of the hole edge due to the heat of the laser or
plasmas cutting torch. The material you are reaming is slightly hardened.

Stan Kapushinski

"Orval Fairbairn" > wrote in message
...
> In article >,
> Fortunat1 > wrote:
>
>> Another stupid question!
>>
>> Been reaming holes in a few 4130 plates. The reamer worked fine for about
>> 20 holes and then the holes started getting a bit smaller to the point
>> the
>> bolts got a bit snug.
>> In my ignorance I thought this one hand reamer would pretty much last me
>> the whole project, but it's obvious I'm going to need a half a dozen of
>> them at least just to do the wing hardware.
>> I did a bit of searching on the net and found some info on reamers. All
>> hand reamers seem to be HSS which would put me back in the same boat I'm
>> already in so I was tempted by the carbide reamers I saw for sale.
>> So, my question is; can you use a carbide tipped reamer designed for use
>> in
>> a lath in a simple drill press effectively? Or, for that matter, can you
>> use a reamer designed for use in a lathe as a hand reamer?
>> Or am I just barking up the wrong tree altogether?
>>
>> By the way, just for info, the holes I've beenreaming are 5/16 and 1/4.
>> The
>> material is .090 4130 and the holes were all laser cut about 1/64
>> undersize. I would ream the first hole in each plate and then clamp
>> together the plates in pairs to ensure accurate alignment of the holes in
>> each pair of plates.
>> Just in case it's not the reamer's fault at all!
>
> Did you use cutting oil? Even plain old lubricating oil helps a lot and
> keeps the tool cool.

[Dale Scroggins]

"Fortunat1" > wrote in message
...
> Another stupid question!
>
> Been reaming holes in a few 4130 plates. The reamer worked fine for about
> 20 holes and then the holes started getting a bit smaller to the point the
> bolts got a bit snug.
> In my ignorance I thought this one hand reamer would pretty much last me
> the whole project, but it's obvious I'm going to need a half a dozen of
> them at least just to do the wing hardware.
> I did a bit of searching on the net and found some info on reamers. All
> hand reamers seem to be HSS which would put me back in the same boat I'm
> already in so I was tempted by the carbide reamers I saw for sale.
> So, my question is; can you use a carbide tipped reamer designed for use
> in
> a lath in a simple drill press effectively? Or, for that matter, can you
> use a reamer designed for use in a lathe as a hand reamer?
> Or am I just barking up the wrong tree altogether?
>
> By the way, just for info, the holes I've beenreaming are 5/16 and 1/4.
> The
> material is .090 4130 and the holes were all laser cut about 1/64
> undersize. I would ream the first hole in each plate and then clamp
> together the plates in pairs to ensure accurate alignment of the holes in
> each pair of plates.
> Just in case it's not the reamer's fault at all!

Hand reamers will develop burrs on the leading edges of the cutters as you
use them. I have used a small carborundum hand stone to remove the burrs on
larger reamers, used to ream engine valve guides. Yours are smaller, so it
might be harder to find a stone small enough or with the correct geometry to
deburr them. But if you can find a stone, use it along the radial flats on
the leading edges of the cutting edges, and the reamer will be good as new
for a while.

[Dan[_2_]]

Fortunat1 wrote:
> Another stupid question!
>
> Been reaming holes in a few 4130 plates. The reamer worked fine for about
> 20 holes and then the holes started getting a bit smaller to the point the
> bolts got a bit snug.
> In my ignorance I thought this one hand reamer would pretty much last me
> the whole project, but it's obvious I'm going to need a half a dozen of
> them at least just to do the wing hardware.
> I did a bit of searching on the net and found some info on reamers. All
> hand reamers seem to be HSS which would put me back in the same boat I'm
> already in so I was tempted by the carbide reamers I saw for sale.
> So, my question is; can you use a carbide tipped reamer designed for use in
> a lath in a simple drill press effectively? Or, for that matter, can you
> use a reamer designed for use in a lathe as a hand reamer?
> Or am I just barking up the wrong tree altogether?
>
> By the way, just for info, the holes I've beenreaming are 5/16 and 1/4. The
> material is .090 4130 and the holes were all laser cut about 1/64
> undersize. I would ream the first hole in each plate and then clamp
> together the plates in pairs to ensure accurate alignment of the holes in
> each pair of plates.
> Just in case it's not the reamer's fault at all!
>

As has already been mentioned laser cutting has hardened the metal
around the hole. if your drill press runs true go with the carbide
tipped. Avoid solid carbide since the average drill press doesn't run
true enough to prevent breakage. If you need a very smooth bore go with
a spiral reamer, if not go with straight. Depending on size and from
whom you purchase the difference in price can run from about a dollar to
slightly phenomenal. As has also been stated use cutting oil and debur
the reamer as needed.

Things that can reduce reamer life: rotating them backwards, wobbling
when used, spun too fast, not using cutting oil, poor storage practice,
using the wrong type for the material, not cleaning the reamer after
use, drilling too small a hole before reaming and throwing across the
room when you discover you were supposed to use an under size reamer
vice the over size one you just used (the most entertaining time for
this to happen is after you have spent hours getting to the point you
need to ream and you are almost finished). In short use common sense.

Having said all this I will add having an extra reamer in sizes you
will use a lot is handy.

I have also noticed plans for various projects I have worked on have
one thing in common: the more complicated the project the more likely
they will call for a size I don't have. This is why I have about 80
different sizes ranging from 0.0135 ( I don't even remember what I used
it on) to 1.5" which I have used for steam engine cylinders.

Good luck with your project.

Dan, U.S. Air Force, retired

[Fortunat1]

Orval Fairbairn > wrote in
:

> In article >,
> Fortunat1 > wrote:
>
>> Another stupid question!
>>
>> Been reaming holes in a few 4130 plates. The reamer worked fine for
>> about 20 holes and then the holes started getting a bit smaller to
>> the point the bolts got a bit snug.
>> In my ignorance I thought this one hand reamer would pretty much last
>> me the whole project, but it's obvious I'm going to need a half a
>> dozen of them at least just to do the wing hardware.
>> I did a bit of searching on the net and found some info on reamers.
>> All hand reamers seem to be HSS which would put me back in the same
>> boat I'm already in so I was tempted by the carbide reamers I saw for
>> sale. So, my question is; can you use a carbide tipped reamer
>> designed for use in a lath in a simple drill press effectively? Or,
>> for that matter, can you use a reamer designed for use in a lathe as
>> a hand reamer? Or am I just barking up the wrong tree altogether?
>>
>> By the way, just for info, the holes I've beenreaming are 5/16 and
>> 1/4. The material is .090 4130 and the holes were all laser cut about
>> 1/64 undersize. I would ream the first hole in each plate and then
>> clamp together the plates in pairs to ensure accurate alignment of
>> the holes in each pair of plates.
>> Just in case it's not the reamer's fault at all!
>
> Did you use cutting oil? Even plain old lubricating oil helps a lot
> and keeps the tool cool.

Just 3in1. It didn't seem to generate a lot of heat. I was only using a
hand drive on it. I'll try a good grade of cutting oil instead next time.

Thanks!

[Fortunat1[_13_]]

"StanKap" > wrote in
:

> The problem is hardening of the hole edge due to the heat of the laser
> or plasmas cutting torch. The material you are reaming is slightly
> hardened.
>

Yeah, I kind of figured that that might be a problem, though it was easy
enough to clean up the edges with a flapper wheel. Also I think the laser
might have been a little conservative cutting the holes 1/64 under making
it slightly hard work for the reamer. Towards the end, before it died, I
was gently knocking the edge off the burnt bit with a rat tail file. I
suspect the reamer might nt have been the best quality either.



Bertie

[Fortunat1[_14_]]

"Dale Scroggins" > wrote in
:

>
> "Fortunat1" > wrote in message
> ...
>> Another stupid question!
>>
>> Been reaming holes in a few 4130 plates. The reamer worked fine for
>> about 20 holes and then the holes started getting a bit smaller to
>> the point the bolts got a bit snug.
>> In my ignorance I thought this one hand reamer would pretty much last
>> me the whole project, but it's obvious I'm going to need a half a
>> dozen of them at least just to do the wing hardware.
>> I did a bit of searching on the net and found some info on reamers.
>> All hand reamers seem to be HSS which would put me back in the same
>> boat I'm already in so I was tempted by the carbide reamers I saw for
>> sale. So, my question is; can you use a carbide tipped reamer
>> designed for use in
>> a lath in a simple drill press effectively? Or, for that matter, can
>> you use a reamer designed for use in a lathe as a hand reamer?
>> Or am I just barking up the wrong tree altogether?
>>
>> By the way, just for info, the holes I've beenreaming are 5/16 and
>> 1/4. The
>> material is .090 4130 and the holes were all laser cut about 1/64
>> undersize. I would ream the first hole in each plate and then clamp
>> together the plates in pairs to ensure accurate alignment of the
>> holes in each pair of plates.
>> Just in case it's not the reamer's fault at all!
>
> Hand reamers will develop burrs on the leading edges of the cutters as
> you use them. I have used a small carborundum hand stone to remove
> the burrs on larger reamers, used to ream engine valve guides. Yours
> are smaller, so it might be harder to find a stone small enough or
> with the correct geometry to deburr them. But if you can find a
> stone, use it along the radial flats on the leading edges of the
> cutting edges, and the reamer will be good as new for a while.
>

Well, it's stil cutting but now the bolts don't fit into the holes, so
I'd say it's past it's sell by date now. i do have some good wet stones
for sharpening gouges that would probably do the job, so I might try
them on this ruined one to see if it puts he sparkle back on it's cut,
though.

[Fortunat1[_15_]]

Dan > wrote in :

> Fortunat1 wrote:
>> Another stupid question!
>>
>> Been reaming holes in a few 4130 plates. The reamer worked fine for
>> about 20 holes and then the holes started getting a bit smaller to
>> the point the bolts got a bit snug.
>> In my ignorance I thought this one hand reamer would pretty much last
>> me the whole project, but it's obvious I'm going to need a half a
>> dozen of them at least just to do the wing hardware.
>> I did a bit of searching on the net and found some info on reamers.
>> All hand reamers seem to be HSS which would put me back in the same
>> boat I'm already in so I was tempted by the carbide reamers I saw for
>> sale. So, my question is; can you use a carbide tipped reamer
>> designed for use in a lath in a simple drill press effectively? Or,
>> for that matter, can you use a reamer designed for use in a lathe as
>> a hand reamer? Or am I just barking up the wrong tree altogether?
>>
>> By the way, just for info, the holes I've beenreaming are 5/16 and
>> 1/4. The material is .090 4130 and the holes were all laser cut about
>> 1/64 undersize. I would ream the first hole in each plate and then
>> clamp together the plates in pairs to ensure accurate alignment of
>> the holes in each pair of plates.
>> Just in case it's not the reamer's fault at all!
>>
>
> As has already been mentioned laser cutting has hardened the metal
> around the hole. if your drill press runs true go with the carbide
> tipped. Avoid solid carbide since the average drill press doesn't run
> true enough to prevent breakage. If you need a very smooth bore go
> with a spiral reamer, if not go with straight. Depending on size and
> from whom you purchase the difference in price can run from about a
> dollar to slightly phenomenal. As has also been stated use cutting oil
> and debur the reamer as needed.
>
> Things that can reduce reamer life: rotating them backwards,
> wobbling
> when used, spun too fast, not using cutting oil, poor storage
> practice, using the wrong type for the material, not cleaning the
> reamer after use, drilling too small a hole before reaming and
> throwing across the room when you discover you were supposed to use an
> under size reamer vice the over size one you just used (the most
> entertaining time for this to happen is after you have spent hours
> getting to the point you need to ream and you are almost finished). In
> short use common sense.
>
> Having said all this I will add having an extra reamer in sizes you
> will use a lot is handy.
>
> I have also noticed plans for various projects I have worked on
> have
> one thing in common: the more complicated the project the more likely
> they will call for a size I don't have. This is why I have about 80
> different sizes ranging from 0.0135 ( I don't even remember what I
> used it on) to 1.5" which I have used for steam engine cylinders.
>
> Good luck with your project.
>

Thanks. Of the above, I did keep it clean, didn't turn it backwards
storage was good, oil might not have been perfect (3in1) but I did have
trouble keeping it dead straight.. I tried to keep it as steady as
possible, but I did chatter t from time to time. The reamer i used was a
spiral one.
You have me wondering now about the wisdom of using my drill press,
since it's only a cheapie. I did go out and try it using my now piece
of junk (pointless since it goes the wrong way round) but I did see that
it's not turning 100% true at the tip. I'll just have to get a good
quality reamer and prepare each hole carefully. I'll see if I can get a
drill bit that brings he holes a little closer to the final size.

[RST Engineering]

Orval, I ain't a tinbender and don't pretend that I am. However, if the
(for instance) 1/4" hole is a sixty-fourth undersize, it should come out
0.234". A letter-D drill will take it out to 0.246" (admittedly with some
triangularity) which should significantly cut into the laser hardened part
of the steel, then the reamer only has to take off the last four thou.

If you want to cut yourself some more leeway, a letter-C drill will take it
out to 0.242 and then you get to ream eight thou.

And for the rest of you, PLEASE SNIP EVERYTHING in the message you are
answering except a few pertinent lines.

Jim

--
"If you think you can, or think you can't, you're right."
--Henry Ford





"Orval Fairbairn" > wrote in message
...

>>
>> By the way, just for info, the holes I've beenreaming are 5/16 and 1/4.

>
> Did you use cutting oil? Even plain old lubricating oil helps a lot and
> keeps the tool cool.

[Rich S.[_1_]]

"Fortunat1" > wrote in message
.. .
> All hand reamers seem to be HSS which would put me back in the same
> boat I'm already in so I was tempted by the carbide reamers I saw for
> sale.

Suggest you ask someone in the Greater Seattle area to stop by Boeing
Surplus and buy a couple pounds of reamers for you. Last I remember they
were ~$3/lb.

Rich S.

[Fortunat1[_16_]]

"RST Engineering" > wrote in
:

> Orval, I ain't a tinbender and don't pretend that I am. However, if
> the (for instance) 1/4" hole is a sixty-fourth undersize, it should
> come out 0.234". A letter-D drill will take it out to 0.246"
> (admittedly with some triangularity) which should significantly cut
> into the laser hardened part of the steel, then the reamer only has to
> take off the last four thou.
>
> If you want to cut yourself some more leeway, a letter-C drill will
> take it out to 0.242 and then you get to ream eight thou.

OK. I did try to file out most of it. My drill supply wouldn't be all that
large and there aren't a lot of places wit a good suply handt to where I
live, but I will try that.

I did try and sharpen the one I have, but it didn't really work. Used a
little slip stone I have for gouges and it was OK for getting the burrs
off, but not so great for sharpening.
I think the quality of the reamer is probably the biggest prob I had.
Anyway, we worked through a few more holes today using the worn one to at
least get some of the harder stuff off and now it'll be relatively easy to
do those holes over when I get a new reamer.

[Dan[_2_]]

Fortunat1 wrote:
> "RST Engineering" > wrote in
> :
>
>> Orval, I ain't a tinbender and don't pretend that I am. However, if
>> the (for instance) 1/4" hole is a sixty-fourth undersize, it should
>> come out 0.234". A letter-D drill will take it out to 0.246"
>> (admittedly with some triangularity) which should significantly cut
>> into the laser hardened part of the steel, then the reamer only has to
>> take off the last four thou.
>>
>> If you want to cut yourself some more leeway, a letter-C drill will
>> take it out to 0.242 and then you get to ream eight thou.
>
> OK. I did try to file out most of it. My drill supply wouldn't be all that
> large and there aren't a lot of places wit a good suply handt to where I
> live, but I will try that.
>
> I did try and sharpen the one I have, but it didn't really work. Used a
> little slip stone I have for gouges and it was OK for getting the burrs
> off, but not so great for sharpening.
> I think the quality of the reamer is probably the biggest prob I had.
> Anyway, we worked through a few more holes today using the worn one to at
> least get some of the harder stuff off and now it'll be relatively easy to
> do those holes over when I get a new reamer.
>
Try Mcmaster.com, the prices aren't the greatest however the quality
and customer service are. I also tend to get next day service if I order
before they start business for the day and don't pay any more than basic
UPS.

Dan, U.S. Air Force, retired

[Fortunat1[_17_]]

Dan > wrote in :


>>
> Try Mcmaster.com, the prices aren't the greatest however the
> quality
> and customer service are. I also tend to get next day service if I
> order before they start business for the day and don't pay any more
> than basic UPS.

OK, thanks. I'll try 'em tomorrow.

[Cy Galley]

Slow speed as well.

"Orval Fairbairn" > wrote in message
...
> In article >,
> Fortunat1 > wrote:
>
>> Another stupid question!
>>
>> Been reaming holes in a few 4130 plates. The reamer worked fine for about
>> 20 holes and then the holes started getting a bit smaller to the point
>> the
>> bolts got a bit snug.
>> In my ignorance I thought this one hand reamer would pretty much last me
>> the whole project, but it's obvious I'm going to need a half a dozen of
>> them at least just to do the wing hardware.
>> I did a bit of searching on the net and found some info on reamers. All
>> hand reamers seem to be HSS which would put me back in the same boat I'm
>> already in so I was tempted by the carbide reamers I saw for sale.
>> So, my question is; can you use a carbide tipped reamer designed for use
>> in
>> a lath in a simple drill press effectively? Or, for that matter, can you
>> use a reamer designed for use in a lathe as a hand reamer?
>> Or am I just barking up the wrong tree altogether?
>>
>> By the way, just for info, the holes I've beenreaming are 5/16 and 1/4.
>> The
>> material is .090 4130 and the holes were all laser cut about 1/64
>> undersize. I would ream the first hole in each plate and then clamp
>> together the plates in pairs to ensure accurate alignment of the holes in
>> each pair of plates.
>> Just in case it's not the reamer's fault at all!
>
> Did you use cutting oil? Even plain old lubricating oil helps a lot and
> keeps the tool cool.

[Morgans[_2_]]

"Cy Galley" <> wrote

> Slow speed as well.

Exactly.

If people had ever seen some charts comparing varying cutting tool speed and
feed pressure, and the resulting wear on the tool, they would be amazed.

In summary, you run your tools too fast, and they go up in smoke in a hurry.

If you ever have to guess, guess on the side of slower tool speed and more
pressure.

Of course, getting a real chart with the tool, material, and the correct
tool speed and feed speed or pressure it the "best" way to go at it. <g>
--
Jim in NC

[Rich S.[_1_]]

"Morgans" > wrote in message
...
>
> If you ever have to guess, guess on the side of slower tool speed and more
> pressure.

Amen to that, Jim. Have you ever let a drill bit spin just for a second on
some stainless and work-harden the surface?

Sounds like he is using the reamer correctly, tho. It's just the lasered
skin that's dulling the tool.

Rich S.

[Morgans[_2_]]

"Rich S." wrote
>
> Amen to that, Jim. Have you ever let a drill bit spin just for a second on
> some stainless and work-harden the surface?

My downfall is always using a large diameter bit, in a drill press that will
not go slow enough, in thick steel.

It is amazing how you can take the temper out of a 21/32" bit, in just a
couple seconds. DAMHIKT !

Also, I found you can actually get a molten blob of glass on the end of a
regular HSS drill bit. You DO have to try quite hard to do that, tho!
Especially the part of not breaking the glass, in the process. :-o

> Sounds like he is using the reamer correctly, tho. It's just the lasered
> skin that's dulling the tool.

I guess the answer is probably pretty obvious, but would it be possible to
normalize the steel right around the small area of the hole? Too much loss
of strength?

It does sound like lowering the tool speed would be worth the try, once the
new reamers get there. It will be fairly obvious is the tool speed is too
low, once a few holes are attempted.
--
Jim in NC

[Dan[_2_]]

Morgans wrote:
> "Cy Galley" <> wrote
>
>> Slow speed as well.
>
> Exactly.
>
> If people had ever seen some charts comparing varying cutting tool speed and
> feed pressure, and the resulting wear on the tool, they would be amazed.
>
> In summary, you run your tools too fast, and they go up in smoke in a hurry.
>
> If you ever have to guess, guess on the side of slower tool speed and more
> pressure.
>
> Of course, getting a real chart with the tool, material, and the correct
> tool speed and feed speed or pressure it the "best" way to go at it. <g>

Of course misidentifying metals is always a gas. Storing hardened
tool steel in the same place as free machining stainless makes for some
rather interesting experiences. Not that I have ever done it or anything :)

Dan, U.S. Air Force, retired

[Fortunat1[_2_]]

"Morgans" > wrote in
:


>
> Of course, getting a real chart with the tool, material, and the
> correct tool speed and feed speed or pressure it the "best" way to
> go at it. <g>

OK, which brings me to another side of this, I guess. I'm hand reaming. By
that I mean I'm putting a tap handle on the reamer, sticking the work piece
in a vice and going at it by twisting the thing by hand. Needless to say
it's nearly impossible to keep the reamer absolutely straight. Am I doing
this right? One suggestion I got was to use my drill press by rigging
something up to hand turn the drill spindle (no way I can get it to turn
slowly enough for reaming) in order to get the reamer straight in.

Is this unneccesarily complicated? We're talking about .090 4130 here with
a 5/16" hole. Wing attach and strut brackets for mounting onto a wooden
spar for the most part..

[Rich S.[_1_]]

"Fortunat1" > wrote in message
.. .
>
> OK, which brings me to another side of this, I guess. I'm hand reaming. By
> that I mean I'm putting a tap handle on the reamer, sticking the work
> piece
> in a vice and going at it by twisting the thing by hand. Needless to say
> it's nearly impossible to keep the reamer absolutely straight. Am I doing
> this right? One suggestion I got was to use my drill press by rigging
> something up to hand turn the drill spindle (no way I can get it to turn
> slowly enough for reaming) in order to get the reamer straight in.

If you look at the top of your hand reamer, I'll bet you'll find a centering
hole. Chuck up a tapered center in the drill press and use it to steady the
top of the reamer.

Rich S.

[Fortunat1[_18_]]

"Rich S." > wrote in
:

> "Fortunat1" > wrote in message
> .. .
>>
>> OK, which brings me to another side of this, I guess. I'm hand
>> reaming. By that I mean I'm putting a tap handle on the reamer,
>> sticking the work piece
>> in a vice and going at it by twisting the thing by hand. Needless to
>> say it's nearly impossible to keep the reamer absolutely straight. Am
>> I doing this right? One suggestion I got was to use my drill press by
>> rigging something up to hand turn the drill spindle (no way I can get
>> it to turn slowly enough for reaming) in order to get the reamer
>> straight in.
>
> If you look at the top of your hand reamer, I'll bet you'll find a
> centering hole. Chuck up a tapered center in the drill press and use
> it to steady the top of the reamer.
>


Hmm, good one. I could alos use the press to regulate the pressure on the
tool easily enough that way..
>
>

[Scott[_1_]]

What's so hard about reaming? I get reamed at work every other day ;)


Scott
http://corbenflyer.tripod.com/
Gotta Fly or Gonna Die
Building RV-4 (Super Slow Build Version)

Fortunat1 wrote:
> "Morgans" > wrote in
> :
>
>
>
>>Of course, getting a real chart with the tool, material, and the
>>correct tool speed and feed speed or pressure it the "best" way to
>>go at it. <g>
>

>

--

[Ernest Christley]

Fortunat1 wrote:
> "Morgans" > wrote in
> :
>
>
>> Of course, getting a real chart with the tool, material, and the
>> correct tool speed and feed speed or pressure it the "best" way to
>> go at it. <g>
>
> OK, which brings me to another side of this, I guess. I'm hand reaming. By
> that I mean I'm putting a tap handle on the reamer, sticking the work piece
> in a vice and going at it by twisting the thing by hand. Needless to say
> it's nearly impossible to keep the reamer absolutely straight. Am I doing
> this right? One suggestion I got was to use my drill press by rigging
> something up to hand turn the drill spindle (no way I can get it to turn
> slowly enough for reaming) in order to get the reamer straight in.
>
> Is this unneccesarily complicated? We're talking about .090 4130 here with
> a 5/16" hole. Wing attach and strut brackets for mounting onto a wooden
> spar for the most part..
>

You could chuck the reamer, and use the chuck key to turn it. A piece
of 1/4" rod (cut threads off long bolt) also make a nice turning handle.



--
"Life is not a journey to the grave with the intention of arriving
safely in
a pretty and well preserved body, but rather to skid in broadside,
thoroughly used up, totally worn out, with chocolate in one hand and
wine in
the other, loudly proclaiming 'WOO HOO What a Ride!'"
--Unknown

[Stealth Pilot[_2_]]

On Tue, 14 Aug 2007 02:03:28 +0000, Scott >
wrote:

>What's so hard about reaming? I get reamed at work every other day ;)
>
>

I was waiting for that comment :-)

a very good use for an old large reamer...

clean it up and mount it in a varnished ornamental base.
tack on the side a plaque.
"for excellence in the field of motivation"

make a really neat job of it and present it to the office bully at the
next office occasion :-)

I still have the reamer and plaque of one presented to the boss many
years ago :-)
stopped him in his steps.

Stealth Pilot

[Fortunat1[_2_]]

Ernest Christley > wrote in
:


>>
>> Is this unneccesarily complicated? We're talking about .090 4130 here
>> with a 5/16" hole. Wing attach and strut brackets for mounting onto a
>> wooden spar for the most part..
>>
>
> You could chuck the reamer, and use the chuck key to turn it. A piece
> of 1/4" rod (cut threads off long bolt) also make a nice turning
> handle.
>

Excellent suggestion. In fact the end of my tap handle did the job
perfectly.
Interpolating all the suggestions here, here's what I did to improve my
reaming.
First, I got some bits to cut the holes a tad larger than they already
were. A 7.7 mm bit got me much closer to the final size. I found some
7.9 mm whcih were also undersize, but I was afraid it was a little too
close and that the drilled hole might leave the corners of the
triangular hole eating past the final reamed size.
Second I used proper cutting oil. I also used the drill press suggestion
which was perfect as it allowed me fine regulation of the pressure on
the reamer and also kept it nice and straight going in.
Now for the next stage. I have to install these on the spars. I have two
possible plans. One, I drill it on the press ensuring that everything is
as square as possible. the other that I use a made up drill guide which
clamps around the spar and "feels" the hole in the plate on the other
side. In either case I plan to use a bit of tubing with an OD the same
size as the ultimate size of the hole in order that it fits in the holes
on the plates so that after the first hole is drilled and I can slip a
bolt in there I can drill the others in precisely the right place using
the plate itself as a guide. In either case I'd drill out to a sixe
under the final dia and then use the reamer to cut the final bit of wood
away. Any pitfalls with this plan?

[Morgans[_2_]]

"Fortunat1" > wrote

> In either case I'd drill out to a sixe
> under the final dia and then use the reamer to cut the final bit of wood
> away. Any pitfalls with this plan?

Sounds to me like you are seriously splitting toadstools.

If you were to just drill the wood so the bolt fits, and then put some epoxy
or varnish or whatever you want to use to make sure the bolt and wood do not
interact, won't that fill the voids?

I always thought that the strength in a fitting like this was in the
squeezing of the fitting on the wood, not the sheer of the bolt against the
wood. Am I wrong?
--
Jim in NC

[Fortunat1]

"Morgans" > wrote in
:

>
> "Fortunat1" > wrote
>
>> In either case I'd drill out to a sixe
>> under the final dia and then use the reamer to cut the final bit of
>> wood away. Any pitfalls with this plan?
>
> Sounds to me like you are seriously splitting toadstools.
>
> If you were to just drill the wood so the bolt fits, and then put some
> epoxy or varnish or whatever you want to use to make sure the bolt and
> wood do not interact, won't that fill the voids?
>
> I always thought that the strength in a fitting like this was in the
> squeezing of the fitting on the wood, not the sheer of the bolt
> against the wood.


Not according to the info I have, anyway. I can't see the friction on the
plates giving much strength at all. One of the engineering manuals i have
is pretty specific about how the size of the bolt makes a large difference
in regards to how much material it's pulling (iow a small bolt will pull
through the wood more readily than a large one because it's applying the
same pressure over a smaller area) Same manual goes to pains to point out
that the hole should be as perfect as possible a fit in order to spread the
load as evenly as possible over the material it's resting against. Seems to
me I may have seen something similar in an old Sport Aviation and maybe one
of the Bengelis books.
But your question brings up a good point. How tight a fit do I want in the
wood and the steel? Too tight will mean I won't be able to fit the bolts
through the steel after painting. I wouldn't be as worried about the wood
as the pourousness of the wood would allow for some retention.

[Morgans[_2_]]

"Fortunat1" > wrote
>
> Not according to the info I have, anyway. I can't see the friction on the
> plates giving much strength at all. One of the engineering manuals i have
> is pretty specific about how the size of the bolt makes a large difference
> in regards to how much material it's pulling (iow a small bolt will pull
> through the wood more readily than a large one because it's applying the
> same pressure over a smaller area) Same manual goes to pains to point out
> that the hole should be as perfect as possible a fit in order to spread
> the
> load as evenly as possible over the material it's resting against. Seems
> to
> me I may have seen something similar in an old Sport Aviation and maybe
> one
> of the Bengelis books.

Is your engineering manual wood aircraft specific?

I am NOT sure of how this applies to your situation, but I KNOW that with
wood propellors, the amount of torque (squeeze) is critical in not having
the prop slip. If the torque is not maintainted, it will allow the prop to
slip around until it bears against the bolts and failure occurs. Anyone
else?

It would seem like the way I have heard that many people do it, is to fill
the space between the bolt and the wood with epoxy. It spreads the loads,
and prevents wood to steel contact, which is critical to prevent corrosion
and decay.

> But your question brings up a good point. How tight a fit do I want in the
> wood and the steel? Too tight will mean I won't be able to fit the bolts
> through the steel after painting. I wouldn't be as worried about the wood
> as the pourousness of the wood would allow for some retention.

[Charles Vincent]

Morgans wrote:
> "Fortunat1" > wrote
>> Not according to the info I have, anyway. I can't see the friction on the
>> plates giving much strength at all. One of the engineering manuals i have
>> is pretty specific about how the size of the bolt makes a large difference
>> in regards to how much material it's pulling (iow a small bolt will pull
>> through the wood more readily than a large one because it's applying the
>> same pressure over a smaller area) Same manual goes to pains to point out
>> that the hole should be as perfect as possible a fit in order to spread
>> the
>> load as evenly as possible over the material it's resting against. Seems
>> to
>> me I may have seen something similar in an old Sport Aviation and maybe
>> one
>> of the Bengelis books.
>
> Is your engineering manual wood aircraft specific?
>
If you read the literature, I think you will find that tearout is an
issue for bolted wood connections on aircraft, so the bearing stress is
important(and is equally applicable to metals as well). If the hole is
oversize the bearing stress goes up. If the bolt size and hole size
are reduced, the bearing stress goes up. So the bolts are generally
sized based on the bearing stress on the wood, not the shear stress of
the bolt. There was even some experimentation with aluminum and hollow
steel bolts at one point.

As to the importance of fit...from an older ANC and FPL study on bolted
wood joints for aircraft.....

"1) bolt holes with visibly smooth side walls have bolt-bearing
properties far superior to those with visibly rough side walls;
2) in order to produce a smooth hole, the drill must be well sharpened
and the rate of feed in drilling must be slow enough to enable the drill
to cut rather than tear its way through the piece; and
3) in the materials used in this study, Douglas-fir plywood and Sitka
spruce, the twist drill produces a smoother hole than does a machine bit.

Because the area of wood in actual contact with the bolt is reduced, a
bolt hole with its wall visibly scored or with material torn or
otherwise removed beyond the true cutting line of the drill will be more
seriously deformed at loads less than the proportional limit, will have
a lower load at proportional limit and a reduced ultimate load, and will
be more seriously deformed at the ultimate load than a hole with a
smooth, truly drilled wall. "

Further findings of the study were that machine sharpened bits were
superior to hand sharpened bits, a slow feed was critical to getting the
best hole quality ala one inch per minute with a twist drill was best.
Also, it mentioned that the drill should be producing shavings, not
small chips or granules, these latter being evidence the bit was tearing
and not cutting the wood.


Charles

[Fortunat1]

"Morgans" > wrote in
:

>
> "Fortunat1" > wrote
>>
>> Not according to the info I have, anyway. I can't see the friction on
>> the plates giving much strength at all. One of the engineering
>> manuals i have is pretty specific about how the size of the bolt
>> makes a large difference in regards to how much material it's pulling
>> (iow a small bolt will pull through the wood more readily than a
>> large one because it's applying the same pressure over a smaller
>> area) Same manual goes to pains to point out that the hole should be
>> as perfect as possible a fit in order to spread the
>> load as evenly as possible over the material it's resting against.
>> Seems to
>> me I may have seen something similar in an old Sport Aviation and
>> maybe one
>> of the Bengelis books.
>
> Is your engineering manual wood aircraft specific?

Yes, and also Tony's book shows wood.

>
> I am NOT sure of how this applies to your situation, but I KNOW that
> with wood propellors, the amount of torque (squeeze) is critical in
> not having the prop slip. If the torque is not maintainted, it will
> allow the prop to slip around until it bears against the bolts and
> failure occurs. Anyone else?

Well, the load situation in a wood prop is a differnet kettle of fish as
far as load goes. The load is delivered in pulses and in both directions
at thousands of times a minute.
The hub is much thicker and much more rigid than the plates I have in my
wing (which are just .090 4130) and it's not hard to imagine that the
plates wouldn't be applying that much pressure between the bolts.
Also, some of them aren't all that big ( a couple of the plates attached
to the drag and anti drag wires only have about 2 sq inches of area) so
I can't see them doing al that much to keep the wing from sweeping
itself in a dive from friction alone.
>
> It would seem like the way I have heard that many people do it, is to
> fill the space between the bolt and the wood with epoxy. It spreads
> the loads, and prevents wood to steel contact, which is critical to
> prevent corrosion and decay.

Well, obviously I'd protect it, but I'm not going to rely on epoxy to
bear a load. If I can't get the holes 100% I'll bush them.



>
>> But your question brings up a good point. How tight a fit do I want
>> in the wood and the steel? Too tight will mean I won't be able to fit
>> the bolts through the steel after painting. I wouldn't be as worried
>> about the wood as the pourousness of the wood would allow for some
>> retention.
>
>
>

[Rich S.[_1_]]

"Fortunat1" > wrote in message
.. .
> Well, obviously I'd protect it, but I'm not going to rely on epoxy to
> bear a load. If I can't get the holes 100% I'll bush them.

Micarta bushings are the most preferred way to install a steel bolt through
wood, especially in a spar. My three-piece Emeraude spar would have required
54 bushings which, given my budget at the time, was way beyond the pale.
Carefully drilled holes and varnish were the order of the day.

Rich S.

[Fortunat1[_2_]]

"Rich S." > wrote in
:

> "Fortunat1" > wrote in message
> .. .
>> Well, obviously I'd protect it, but I'm not going to rely on epoxy to
>> bear a load. If I can't get the holes 100% I'll bush them.
>
> Micarta bushings are the most preferred way to install a steel bolt
> through wood, especially in a spar. My three-piece Emeraude spar would
> have required 54 bushings which, given my budget at the time, was way
> beyond the pale. Carefully drilled holes and varnish were the order of
> the day.
>

Hmm. Well, the plans don't call for bushings. All of the high stress areas
have ply doublers and I'm using Birch instead of mahogony, so they should
be tough enough. Off the top of my head, I'd need about 80 bushings for the
Hatz. So I guess I'l just be as careful as I can cutting the holes. Just
looking through Bengelis' book, I see he recommends using a twist drill to
cut the holes, presumably to their final size, wheras I'd planned on
reaming using the plates themselves as a guide. I figured I'd get the
cleanest hole this way.

[Morgans[_2_]]

"Fortunat1" > wrote

> Hmm. Well, the plans don't call for bushings. All of the high stress areas
> have ply doublers and I'm using Birch instead of mahogony, so they should
> be tough enough. Off the top of my head, I'd need about 80 bushings for
> the
> Hatz. So I guess I'l just be as careful as I can cutting the holes. Just
> looking through Bengelis' book, I see he recommends using a twist drill to
> cut the holes, presumably to their final size, wheras I'd planned on
> reaming using the plates themselves as a guide. I figured I'd get the
> cleanest hole this way.

Yep, you could spend time reaming 80 holes, or be on the way to having the
whole thing done by doing something else.

IMHO, reaming in wood is taking it one step further than needed. How much
would the strength be improved by reaming? Not more than a couple percent,
at best, I'll bet.

On the using epoxy as a hole filler and wood protector; I did not mean to
imply to do a sloppy job drilling, but that epoxy does fill any
irregularities. It probably has a higher crush strength than the wood, too,
so it would spread the load evenly to the wood very nicely.

All the above is worth what the price for it was. Right? ;-)
--
Jim in NC

[Charles Vincent]

Fortunat1 wrote:
> "Rich S." > wrote in
> :
>
>> "Fortunat1" > wrote in message
>> .. .
>>> Well, obviously I'd protect it, but I'm not going to rely on epoxy to
>>> bear a load. If I can't get the holes 100% I'll bush them.
>> Micarta bushings are the most preferred way to install a steel bolt
>> through wood, especially in a spar. My three-piece Emeraude spar would
>> have required 54 bushings which, given my budget at the time, was way
>> beyond the pale. Carefully drilled holes and varnish were the order of
>> the day.
>>
>
> Hmm. Well, the plans don't call for bushings. All of the high stress areas
> have ply doublers and I'm using Birch instead of mahogony, so they should
> be tough enough. Off the top of my head, I'd need about 80 bushings for the
> Hatz. So I guess I'l just be as careful as I can cutting the holes. Just
> looking through Bengelis' book, I see he recommends using a twist drill to
> cut the holes, presumably to their final size, wheras I'd planned on
> reaming using the plates themselves as a guide. I figured I'd get the
> cleanest hole this way.

I would test that theory first. Reamers may or may not give a good
finish on wood. That was one of the reasons I quoted the study I did.
The twist drill gave the best hole finish.

Charles

[Fortunat1[_2_]]

Charles Vincent > wrote in
:

> Fortunat1 wrote:
>> "Rich S." > wrote in
>> :
>>
>>> "Fortunat1" > wrote in message
>>> .. .
>>>> Well, obviously I'd protect it, but I'm not going to rely on epoxy
>>>> to bear a load. If I can't get the holes 100% I'll bush them.
>>> Micarta bushings are the most preferred way to install a steel bolt
>>> through wood, especially in a spar. My three-piece Emeraude spar
>>> would have required 54 bushings which, given my budget at the time,
>>> was way beyond the pale. Carefully drilled holes and varnish were
>>> the order of the day.
>>>
>>
>> Hmm. Well, the plans don't call for bushings. All of the high stress
>> areas have ply doublers and I'm using Birch instead of mahogony, so
>> they should be tough enough. Off the top of my head, I'd need about
>> 80 bushings for the Hatz. So I guess I'l just be as careful as I can
>> cutting the holes. Just looking through Bengelis' book, I see he
>> recommends using a twist drill to cut the holes, presumably to their
>> final size, wheras I'd planned on reaming using the plates themselves
>> as a guide. I figured I'd get the cleanest hole this way.
>
> I would test that theory first. Reamers may or may not give a good
> finish on wood. That was one of the reasons I quoted the study I did.
> The twist drill gave the best hole finish.


OK, I went out and tried both. The nice fresh twist dril gave an
excellent hole as did a slightly enlarged hole using a reamer. I found I
had to feed the twist drill at a very steady pace to get the best
finish, but it definitely does the job. Whagt I'm still having trouble
with is getting the hole absolutely concentric with the steel plates on
either side. Clamping the plate and using it as a guide to ream the wood
seems to be a bad idea. the steel steers the reamer and the reamer
starts to wander. Drilling the wood through the already finished steel
plates seems like a very bad idea, so now I'm at a loss. What I've
already tried is getting a piece of tubing, grinding the O.D. to the
size of the finished hole and sticking it into the hole in the steel
plate. I then use a bit that's the same as the I.D. of the tubing and
drill an undersized hole. then, without moving the work, I drill a
second, larger hole just a couple thou under the required finished dia..
Tehn I reamed. Obviously, since there's about 4 or five holes in each
plate, I'm going to need to repeatedly drill accurate holes in the wood
Suggestions?

[[email protected]]

I'm going to need to repeatedly drill accurate holes in the wood
> Suggestions?- Hide quoted text -
>

Me thinks you are making this way too complex............IMHO

Unfortunatly, you alreay reamed the holes in your fittings. The easy
way is to drill the holes 1/64 undersize, clamp the fittings where
they need to go and drill both fittings and the spar at the same
time. Use either a drill press or a hand drill with one of the home
made jigs to find the hole on the back side. If you want, put some
cheap hardware grade bolts in each hole as you drill to keep things
together (you can even drill the spar by hand one full size smaller
and use cheap bolts to hold the assembly aligned for the drilling)

Take the whole thing apart, ream the holes to final size, treat/paint
the fittings and assemble with a bit of West System in the holes. Add
some flox if you really made a mess of the holes.

As long as the bolts fit nice and snug in the metal the wood can be
pretty sloppy and the West will fill in the assembly will be as strong
or stronger than one with a perfectly fit wood to bolt hole. The only
down side is that it is a more or less permanant joint............but
then how often does one need to remove metal spar fittings?
===============
Leon McAtee

[Fortunat1[_19_]]

" > wrote in
oups.com:

> I'm going to need to repeatedly drill accurate holes in the wood
>> Suggestions?- Hide quoted text -
>>
>
> Me thinks you are making this way too complex............IMHO
>
> Unfortunatly, you alreay reamed the holes in your fittings. The easy
> way is to drill the holes 1/64 undersize, clamp the fittings where
> they need to go and drill both fittings and the spar at the same
> time. Use either a drill press or a hand drill with one of the home
> made jigs to find the hole on the back side. If you want, put some
> cheap hardware grade bolts in each hole as you drill to keep things
> together (you can even drill the spar by hand one full size smaller
> and use cheap bolts to hold the assembly aligned for the drilling)
>
> Take the whole thing apart, ream the holes to final size, treat/paint
> the fittings and assemble with a bit of West System in the holes. Add
> some flox if you really made a mess of the holes.
>
> As long as the bolts fit nice and snug in the metal the wood can be
> pretty sloppy and the West will fill in the assembly will be as strong
> or stronger than one with a perfectly fit wood to bolt hole. The only
> down side is that it is a more or less permanant joint............but
> then how often does one need to remove metal spar fittings?


Well, too late now but I tried this and dismissed it early on. At least
I couldn't get it to work.
I found the hole on the back side fitting wasn't as accurate as I'd
like. Also, I'd rather not resort to filler if I can help it at all. In
fact, I think I'd discard a spar first and use it for something else.
I've been experimenting this afternoon. and discovered that if I place
the spar, with one fitting correctly positioned on top absolutely square
in the dril press and then carefully brought the drill bit down into the
hole and turned it by hand until it bites a bit.When the bit is in far
enough I switch on and go right through. Worked perfectly and the holes
line up on both sides perfectly with nice snug holes all around.

[[email protected]]

On Aug 16, 10:44 am, Fortunat1 > wrote:
> "Morgans" > wrote :
>
>
>
>
>
>
>
> > "Fortunat1" > wrote
>
> >> In either case I'd drill out to a sixe
> >> under the final dia and then use the reamer to cut the final bit of
> >> wood away. Any pitfalls with this plan?
>
> > Sounds to me like you are seriously splitting toadstools.
>
> > If you were to just drill the wood so the bolt fits, and then put some
> > epoxy or varnish or whatever you want to use to make sure the bolt and
> > wood do not interact, won't that fill the voids?
>
> > I always thought that the strength in a fitting like this was in the
> > squeezing of the fitting on the wood, not the sheer of the bolt
> > against the wood.
>
> Not according to the info I have, anyway. I can't see the friction on the
> plates giving much strength at all. One of the engineering manuals i have
> is pretty specific about how the size of the bolt makes a large difference
> in regards to how much material it's pulling (iow a small bolt will pull
> through the wood more readily than a large one because it's applying the
> same pressure over a smaller area) Same manual goes to pains to point out
> that the hole should be as perfect as possible a fit in order to spread the
> load as evenly as possible over the material it's resting against. Seems to
> me I may have seen something similar in an old Sport Aviation and maybe one
> of the Bengelis books.
> But your question brings up a good point. How tight a fit do I want in the
> wood and the steel? Too tight will mean I won't be able to fit the bolts
> through the steel after painting. I wouldn't be as worried about the wood
> as the pourousness of the wood would allow for some retention.- Hide quoted text -
>
> - Show quoted text -

"FRICTION is FICTION", or so it says in my engineering textbook.

I think I should add my experience with wood spars. On the wood
winged homebuilt I constructed ( a Coot, designed by Molt Taylor who
also designed and built several experimental aircraft including the
Aerocar), the 4130 wing attachment plates were attached with 1/4" AN
bolts. The bolts went all the way through the spar and plates on each
side. The spruce spars were drilled with 5/8" holes that had 5/8" 2024
aluminum bushings with 1/4" holes epoxied into the spruce spar caps.
Micarta would work fine for the bushings also, you just need something
stronger than the wood. This is the proper way to attach highly loaded
metal plates to wood. The safety of the joint depends on how much
bearing stress the wood has to support. The Coot was a cantlever wing
that had very high bending loads at the attachment. Anything less than
the approach taken by Mr. Taylor would have been unacceptable. The
5/16" hole through the wood you are dealing with has a specific amount
of load that it can safely carry. Trust me, it is nowhere near what
any metal will support. The strongest wood there is (Hickory) has a
tensile strength of about 1400 to 1500 psi. It's bearing strength is
only slightly higher.
The information you have that says don't rely on clamping
pressure to carry the load is correct. The adage of "Friction is
Fiction" is one structural engineers use to explain that carrying a
load using friction is not an acceptable way of constructing a
structural joint, period. No argument.
What aircraft are you building? Whether or not the 1/4 and 5/16"
holes you have will be sufficient depends on how much load they must
carry, period. A 1/4" hole in wood will not carry much. If it is a
strut type wing (ala Cessna Skyhawk) that will be a big help. I can't
imagine a cantilevered wing where 1/4" holes would be OK at the wing
attachment. The Coot had I believe, 18 seperate 5/8" bushings in the
root of the main wing spar. As for getting proper clamping pressure
for wooden props, this is important because without it, the wood would
deform too much if allowed to by not holding it in place with
pressure, thereby weakening the joint. Friction exists and carries
load for sure, but it can easily change over time and then what are
you left with? Friction is never counted on to carry load. If the
shear or tensile or bearing strength is not sufficient, then you are
just asking for trouble.
Epoxying the bolts in place is a good idea also. Getting the
holes straight, smooth sided, properly aligned, and especially, the
correct diameter is an even better one.


Regards,
Bud

[Fortunat1[_12_]]

wrote in
ps.com:

> On Aug 16, 10:44 am, Fortunat1 > wrote:
>> "Morgans" > wrote
>> :
>>
>>
>>
>>
>>
>>
>>
>> > "Fortunat1" > wrote
>>
>> >> In either case I'd drill out to a sixe
>> >> under the final dia and then use the reamer to cut the final bit
>> >> of wood away. Any pitfalls with this plan?
>>
>> > Sounds to me like you are seriously splitting toadstools.
>>
>> > If you were to just drill the wood so the bolt fits, and then put
>> > some epoxy or varnish or whatever you want to use to make sure the
>> > bolt and wood do not interact, won't that fill the voids?
>>
>> > I always thought that the strength in a fitting like this was in
>> > the squeezing of the fitting on the wood, not the sheer of the bolt
>> > against the wood.
>>
>> Not according to the info I have, anyway. I can't see the friction on
>> the plates giving much strength at all. One of the engineering
>> manuals i have is pretty specific about how the size of the bolt
>> makes a large difference in regards to how much material it's pulling
>> (iow a small bolt will pull through the wood more readily than a
>> large one because it's applying the same pressure over a smaller
>> area) Same manual goes to pains to point out that the hole should be
>> as perfect as possible a fit in order to spread the load as evenly as
>> possible over the material it's resting against. Seems to me I may
>> have seen something similar in an old Sport Aviation and maybe one
>> of the Bengelis books.
>> But your question brings up a good point. How tight a fit do I want
>> in the wood and the steel? Too tight will mean I won't be able to fit
>> the bolts through the steel after painting. I wouldn't be as worried
>> about the wood as the pourousness of the wood would allow for some
>> retention.- Hide quoted text -
>>
>> - Show quoted text -
>
> "FRICTION is FICTION", or so it says in my engineering textbook.
>
> I think I should add my experience with wood spars. On the wood
> winged homebuilt I constructed ( a Coot, designed by Molt Taylor who
> also designed and built several experimental aircraft including the
> Aerocar), the 4130 wing attachment plates were attached with 1/4" AN
> bolts. The bolts went all the way through the spar and plates on each
> side. The spruce spars were drilled with 5/8" holes that had 5/8" 2024
> aluminum bushings with 1/4" holes epoxied into the spruce spar caps.
> Micarta would work fine for the bushings also, you just need something
> stronger than the wood. This is the proper way to attach highly loaded
> metal plates to wood. The safety of the joint depends on how much
> bearing stress the wood has to support. The Coot was a cantlever wing
> that had very high bending loads at the attachment. Anything less than
> the approach taken by Mr. Taylor would have been unacceptable. The
> 5/16" hole through the wood you are dealing with has a specific amount
> of load that it can safely carry. Trust me, it is nowhere near what
> any metal will support. The strongest wood there is (Hickory) has a
> tensile strength of about 1400 to 1500 psi. It's bearing strength is
> only slightly higher.
> The information you have that says don't rely on clamping
> pressure to carry the load is correct. The adage of "Friction is
> Fiction" is one structural engineers use to explain that carrying a
> load using friction is not an acceptable way of constructing a
> structural joint, period. No argument.
> What aircraft are you building? Whether or not the 1/4 and 5/16"
> holes you have will be sufficient depends on how much load they must
> carry, period. A 1/4" hole in wood will not carry much. If it is a
> strut type wing (ala Cessna Skyhawk) that will be a big help. I can't
> imagine a cantilevered wing where 1/4" holes would be OK at the wing
> attachment. The Coot had I believe, 18 seperate 5/8" bushings in the
> root of the main wing spar. As for getting proper clamping pressure
> for wooden props, this is important because without it, the wood would
> deform too much if allowed to by not holding it in place with
> pressure, thereby weakening the joint. Friction exists and carries
> load for sure, but it can easily change over time and then what are
> you left with? Friction is never counted on to carry load. If the
> shear or tensile or bearing strength is not sufficient, then you are
> just asking for trouble.
> Epoxying the bolts in place is a good idea also. Getting the
> holes straight, smooth sided, properly aligned, and especially, the
> correct diameter is an even better one.
>

Thanks, even more good info!

It's a Hatz. As far as I know nobody who's built one of these has done
anything but drill unbushed holes through the wood. There are ply
doublers at the wing root and strut attach points, but the majority of
the load is carried through the cellule by the wires, fuselage and
struts, leaving the spars to take up the loads at these points. In other
words, there's nowhere near the loads put on these fittings that would
be put on them by a similar fitting taking a cantilever wing's load or
even that of a stutted monoplane. As far as I know no hatz has had an
inflight failure, though a related design, the Kelly D, has. If I
understand it correctly, the Kelly D's spars are much shallower than the
Hatz's and the airplane in question did not have one of it's ply spar
doublers glued on correctly which has certainly motivated me to get this
right.
The bolts holding the plates to the spars are all 5/16 as are the bolts
hinging the wings to the fuse and ceter section. The struts are all 1/4
bolts.

[Morgans[_2_]]

> wrote

> As for getting proper clamping pressure
> for wooden props, this is important because without it, the wood would
> deform too much if allowed to by not holding it in place with
> pressure, thereby weakening the joint. Friction exists and carries
> load for sure, but it can easily change over time and then what are
> you left with? Friction is never counted on to carry load. If the
> shear or tensile or bearing strength is not sufficient, then you are
> just asking for trouble.

But that is exactly what is taking place with a wood prop, right? Friction
alone? There is no shear strength applied to the prop bolts, and if there
is, the hole in the prop will elongate in the wood and cause failure. It is
also why sometimes spring type washers (what is the name of those, belview,
or something? ) are used to hold the same clamping pressure though changes
in the props dimension, due to humidity and temperature changes.

At least, that is what everything I have read says about wood props. That
is also why wood props are to be re torqued periodicaly, and whenever there
is a major change in humidity and temperature situations, such as the
changes in a season. Is that not what you have been taught about wood
props?

So, while there is much about your post I agree with, and goes along with
what I have been taught, parts of it confused me.

Would you be willing to try again, for slow learners, like me? <g>
--
Jim in NC

[Morgans[_2_]]

"Fortunat1" > wrote > It's a Hatz. As far as I know nobody who's
built one of these has done
> anything but drill unbushed holes through the wood. There are ply
> doublers at the wing root and strut attach points, but the majority of
> the load is carried through the cellule by the wires, fuselage and
> struts, leaving the spars to take up the loads at these points. In other
> words, there's nowhere near the loads put on these fittings that would
> be put on them by a similar fitting taking a cantilever wing's load or
> even that of a stutted monoplane. As far as I know no hatz has had an
> inflight failure

> The bolts holding the plates to the spars are all 5/16 as are the bolts
> hinging the wings to the fuse and ceter section. The struts are all 1/4
> bolt.

I have a big sneaking suspicion that the design has a very generous over
design factor built into it, (as it should have in such a critical area) if
there have been no failures. No doubt, that many people have done sloppy
jobs of drilling these holes, and some of those people even exceeded the
loads on their airplane (both weight and G wise) that it was designed for,
and did not die, or even fail the wing.

If most just do a good or average job of installing the wing and braces, it
has a healthy safety factor.

I guess you will do as you want, for the desire to do the very best you can
do. That is part of the reason people build a home-made flying machine,
right? <g>

Nothing wrong with than, but don't obsess with it. I have a feeling what
ever you come up with will be way above average, and perhaps 1 or 2 percent
stronger. :-)

One other possibility for you to consider if you go with drilling the wood
using the plate as a guide, you could dull the sides of the bit's spirals
with a dremmel tool, to prevent it from cutting into the sides of the plate
as you are drilling through it.
--
Jim in NC

[[email protected]]

On Aug 17, 9:23 pm, Fortunat1 > wrote:
> wrote oups.com:
>
>
>
>
>
> > On Aug 16, 10:44 am, Fortunat1 > wrote:
> >> "Morgans" > wrote
> >> :
>
> >> > "Fortunat1" > wrote
>
> >> >> In either case I'd drill out to a sixe
> >> >> under the final dia and then use the reamer to cut the final bit
> >> >> of wood away. Any pitfalls with this plan?
>
> >> > Sounds to me like you are seriously splitting toadstools.
>
> >> > If you were to just drill the wood so the bolt fits, and then put
> >> > some epoxy or varnish or whatever you want to use to make sure the
> >> > bolt and wood do not interact, won't that fill the voids?
>
> >> > I always thought that the strength in a fitting like this was in
> >> > the squeezing of the fitting on the wood, not the sheer of the bolt
> >> > against the wood.
>
> >> Not according to the info I have, anyway. I can't see the friction on
> >> the plates giving much strength at all. One of the engineering
> >> manuals i have is pretty specific about how the size of the bolt
> >> makes a large difference in regards to how much material it's pulling
> >> (iow a small bolt will pull through the wood more readily than a
> >> large one because it's applying the same pressure over a smaller
> >> area) Same manual goes to pains to point out that the hole should be
> >> as perfect as possible a fit in order to spread the load as evenly as
> >> possible over the material it's resting against. Seems to me I may
> >> have seen something similar in an old Sport Aviation and maybe one
> >> of the Bengelis books.
> >> But your question brings up a good point. How tight a fit do I want
> >> in the wood and the steel? Too tight will mean I won't be able to fit
> >> the bolts through the steel after painting. I wouldn't be as worried
> >> about the wood as the pourousness of the wood would allow for some
> >> retention.- Hide quoted text -
>
> >> - Show quoted text -
>
> > "FRICTION is FICTION", or so it says in my engineering textbook.
>
> > I think I should add my experience with wood spars. On the wood
> > winged homebuilt I constructed ( a Coot, designed by Molt Taylor who
> > also designed and built several experimental aircraft including the
> > Aerocar), the 4130 wing attachment plates were attached with 1/4" AN
> > bolts. The bolts went all the way through the spar and plates on each
> > side. The spruce spars were drilled with 5/8" holes that had 5/8" 2024
> > aluminum bushings with 1/4" holes epoxied into the spruce spar caps.
> > Micarta would work fine for the bushings also, you just need something
> > stronger than the wood. This is the proper way to attach highly loaded
> > metal plates to wood. The safety of the joint depends on how much
> > bearing stress the wood has to support. The Coot was a cantlever wing
> > that had very high bending loads at the attachment. Anything less than
> > the approach taken by Mr. Taylor would have been unacceptable. The
> > 5/16" hole through the wood you are dealing with has a specific amount
> > of load that it can safely carry. Trust me, it is nowhere near what
> > any metal will support. The strongest wood there is (Hickory) has a
> > tensile strength of about 1400 to 1500 psi. It's bearing strength is
> > only slightly higher.
> > The information you have that says don't rely on clamping
> > pressure to carry the load is correct. The adage of "Friction is
> > Fiction" is one structural engineers use to explain that carrying a
> > load using friction is not an acceptable way of constructing a
> > structural joint, period. No argument.
> > What aircraft are you building? Whether or not the 1/4 and 5/16"
> > holes you have will be sufficient depends on how much load they must
> > carry, period. A 1/4" hole in wood will not carry much. If it is a
> > strut type wing (ala Cessna Skyhawk) that will be a big help. I can't
> > imagine a cantilevered wing where 1/4" holes would be OK at the wing
> > attachment. The Coot had I believe, 18 seperate 5/8" bushings in the
> > root of the main wing spar. As for getting proper clamping pressure
> > for wooden props, this is important because without it, the wood would
> > deform too much if allowed to by not holding it in place with
> > pressure, thereby weakening the joint. Friction exists and carries
> > load for sure, but it can easily change over time and then what are
> > you left with? Friction is never counted on to carry load. If the
> > shear or tensile or bearing strength is not sufficient, then you are
> > just asking for trouble.
> > Epoxying the bolts in place is a good idea also. Getting the
> > holes straight, smooth sided, properly aligned, and especially, the
> > correct diameter is an even better one.
>
> Thanks, even more good info!
>
> It's a Hatz. As far as I know nobody who's built one of these has done
> anything but drill unbushed holes through the wood. There are ply
> doublers at the wing root and strut attach points, but the majority of
> the load is carried through the cellule by the wires, fuselage and
> struts, leaving the spars to take up the loads at these points. In other
> words, there's nowhere near the loads put on these fittings that would
> be put on them by a similar fitting taking a cantilever wing's load or
> even that of a stutted monoplane. As far as I know no hatz has had an
> inflight failure, though a related design, the Kelly D, has. If I
> understand it correctly, the Kelly D's spars are much shallower than the
> Hatz's and the airplane in question did not have one of it's ply spar
> doublers glued on correctly which has certainly motivated me to get this
> right.
> The bolts holding the plates to the spars are all 5/16 as are the bolts
> hinging the wings to the fuse and ceter section. The struts are all 1/4
> bolts. - Hide quoted text -
>
> - Show quoted text -

I took a look at the Hatz and it looks cool. All open cockpit biplanes
are. Yes, you are correct that a biplane does not have as much stress
at the wing attachments as even a strutted monoplane. There is little
if any bending load there, and that is what causes the highest
stresses in monoplane designs, especially full cantlevered ones. So
just putting a 5/16" bolt straight through the spar and cover plates
should work OK. the tighter the fit the better, in the plates AND the
wood. Again, I recommend epoxying everything in place. I don't know if
the plans call for installing metal or other bushings in the spar
caps, however I know that I would try and install some if it were
mine. If you were to drill a 3/8" hole, install an aluminum bushing
with a 1/4" hole and epoxy them in the spar caps, you will restore
most of the strength removed by drilling the holes through the wood.
If you just slide a bolt through the hole, you won't restore any
strength. I know it is more work, but I recommend it. Epoxying the
bolts will do about the same thing. Using bushings allows you to
remove the bolts, do repairs, etc. It's the way to go.
Post some pictures when you are done.

Regards,
Bud

[Cy Galley]

Props are cyclically loaded and depend on friction to do the driving. Many
cases of the drive lugs tearing out, the bolts break and then the prop
departs. All this WILL happen if the bolts loose their tension. When the
bolts loose their tension, the prop begins to "work" or slide between the
two clamping faces. Some catch it before failure from the squeaking of the
prop movement or the smell of burning wood.

One can NOT compare this constant loading un-loading with the strut
fittings. An entirely different!

--
Cy Galley - Chair,
AirVenture Emergency Aircraft Repair
A 46 Year Service Project of Chapter 75
EAA Safety Programs Editor - TC
EAA Sport Pilot


"Morgans" > wrote in message
...
>
> > wrote
>
>> As for getting proper clamping pressure
>> for wooden props, this is important because without it, the wood would
>> deform too much if allowed to by not holding it in place with
>> pressure, thereby weakening the joint. Friction exists and carries
>> load for sure, but it can easily change over time and then what are
>> you left with? Friction is never counted on to carry load. If the
>> shear or tensile or bearing strength is not sufficient, then you are
>> just asking for trouble.
>
> But that is exactly what is taking place with a wood prop, right?
> Friction alone? There is no shear strength applied to the prop bolts, and
> if there is, the hole in the prop will elongate in the wood and cause
> failure. It is also why sometimes spring type washers (what is the name
> of those, belview, or something? ) are used to hold the same clamping
> pressure though changes in the props dimension, due to humidity and
> temperature changes.
>
> At least, that is what everything I have read says about wood props. That
> is also why wood props are to be re torqued periodicaly, and whenever
> there is a major change in humidity and temperature situations, such as
> the changes in a season. Is that not what you have been taught about wood
> props?
>
> So, while there is much about your post I agree with, and goes along with
> what I have been taught, parts of it confused me.
>
> Would you be willing to try again, for slow learners, like me? <g>
> --
> Jim in NC
>

[Morgans[_2_]]

"Cy Galley" > wrote

> One can NOT compare this constant loading un-loading with the strut
> fittings. An entirely different!

So, the strut fittings to spar connection depends on the _shear_ loading of
the bolts, only?

Where do you stand on the current discussion of reaming vs. drilling the
wood spar for the bolts? How close do they need to be fitted. How about
the use of epoxy to spread the load in the holes, and fill _small_
irregularities?
--
Jim in NC

[Cy Galley]

I am in the bushing camp. The compressive forces need to be spread over a
larger area in the wood than in the steel fittings. I'd use a "forstner"
type bit for the wood portion. Wants to be a snug fit.

Reamers are designed to shear non-grained metal not wood as the cutting
angles are different. It always helps to use the tool designed to do the
job correctly. Metal reamers are not for wood.



"Morgans" > wrote in message
...
>
> "Cy Galley" > wrote
>
>> One can NOT compare this constant loading un-loading with the strut
>> fittings. An entirely different!
>
> So, the strut fittings to spar connection depends on the _shear_ loading
> of the bolts, only?
>
> Where do you stand on the current discussion of reaming vs. drilling the
> wood spar for the bolts? How close do they need to be fitted. How about
> the use of epoxy to spread the load in the holes, and fill _small_
> irregularities?
> --
> Jim in NC
>

[[email protected]]

On Aug 18, 12:44 am, "Morgans" > wrote:
> > wrote
>
> > As for getting proper clamping pressure
> > for wooden props, this is important because without it, the wood would
> > deform too much if allowed to by not holding it in place with
> > pressure, thereby weakening the joint. Friction exists and carries
> > load for sure, but it can easily change over time and then what are
> > you left with? Friction is never counted on to carry load. If the
> > shear or tensile or bearing strength is not sufficient, then you are
> > just asking for trouble.
>
> But that is exactly what is taking place with a wood prop, right? Friction
> alone? There is no shear strength applied to the prop bolts, and if there
> is, the hole in the prop will elongate in the wood and cause failure. It is
> also why sometimes spring type washers (what is the name of those, belview,
> or something? ) are used to hold the same clamping pressure though changes
> in the props dimension, due to humidity and temperature changes.
>
> At least, that is what everything I have read says about wood props. That
> is also why wood props are to be re torqued periodicaly, and whenever there
> is a major change in humidity and temperature situations, such as the
> changes in a season. Is that not what you have been taught about wood
> props?
>
> So, while there is much about your post I agree with, and goes along with
> what I have been taught, parts of it confused me.
>
> Would you be willing to try again, for slow learners, like me? <g>
> --
> Jim in NC

> Would you be willing to try again, for slow learners, like me? <g>

Be glad to.

>So, while there is much about your post I agree with, parts of it confused me<

I'm not sure what parts confused you, but I'll give it a shot.

>But that is exactly what is taking place with a wood prop, right?
Friction
> alone? There is no shear strength applied to the prop bolts,<

>From this statement, I assume you think there is no shear load on the
prop bolts. To answer whether there is or not, one must know the exact
design of the propellar hub. If you go to the Sensenich Wooden
Propellars website

http://www.sensenichprop.com/sen_html/aircraft_cet/install/cf-a.pdf

and go to page 2 of the document there, you will read the
following....

PROPELLER MAINTENANCE (BOLT TORQUE):
Maintaining proper bolt torque is the most
important maintenance item for a wooden propeller.
Loss of proper bolt torque will result in the decrease
or loss of hub compression and thus the loss of drive
friction between the propeller mounting hub face and
the engine or spool drive flange. At this point the
torque is transferred only by the engine flange drive
bushings and attaching bolts, which will begin to
elongate the bolt holes and counterbores in the rear
face of the wooden propeller. This can eventually
cause cracking in the hub and/or failure of the
attaching bolts and possible separation of the
propeller from the aircraft.

>From this it is obvious that they are warning about losing the
friction between the prop hub and engine flange, and then being left
with only the drive bushings installed in the hub to transfer the
torque. Continued operation in such a situation they say eventually
leads to cracking and elongation of the bolt holes. Eventually. So
this means that the prop has the engine torque delivered through both
friction between the faces, and the bolts and drive bushings installed
in the back of the hub, and you can fly for a long time having only
the drive bushings driving the prop. The fact that they are called
drive bushings pretty much says what their function is. Wooden
propellars are as old as aircraft, and have been designed and modified
pretty much by experience, and not by analysis. They rely on both
friction and bearing to transmit the torque from the engine. As far as
I know, this is the only place where major loads on aircraft are
counted on to be transferred by friction, and this because it helps
extend the life of the expensive propellars, by distributing the load
over a larger area. Using friction here has sort of been grandfathered
in.
If you read all of the article, you will see that prop bolt
torque must be checked every 50 hrs of operation. This is not possible
for attachment hardware inside a wing, even if you had enough access
covers to do so. Having enough bearing strength in the spar joint is
the only acceptable method.
As a final note about guidelines used by structural engineers,
friction is never used to help show a structure good. You only include
friction in structural analysis when it works against you. The reason
is exactly what has been stated. Friction is too dependent on surface
condition, pressure between the faces, etc., all of which changes or
even disappears over time, leaving you with what?
So you are correct that friction is used in tranferring torque in
wooden props. They also use counterbored drive bushings to transfer
the torque. I'd be willing to bet that the bushings transfer most of
it, but that is only a guess.

regards,
Bud

[Morgans[_2_]]

> wrote

> So you are correct that friction is used in tranferring torque in
> wooden props. They also use counterbored drive bushings to transfer
> the torque. I'd be willing to bet that the bushings transfer most of
> it, but that is only a guess.

Thanks.
--
Jim in NC

[Morgans[_2_]]

"Cy Galley" > wrote

> Reamers are designed to shear non-grained metal not wood as the cutting
> angles are different. It always helps to use the tool designed to do the
> job correctly. Metal reamers are not for wood.

Thanks, Cy. I can always count on you to set me straight! ;-)
--
Jim in NC

[[email protected]]

On Aug 20, 2:44 am, "Morgans" > wrote:
> > wrote
>
> > So you are correct that friction is used in tranferring torque in
> > wooden props. They also use counterbored drive bushings to transfer
> > the torque. I'd be willing to bet that the bushings transfer most of
> > it, but that is only a guess.
>
> Thanks.
> --
> Jim in NC

I spent some time talking today at lunch with some friends who are
structural engineers, about this issue of friction delivering torque
to the prop. They said that if the strength of the attachment of the
prop to the flange had been determined through experience, then
eliminating the friction load path for the engine torque to be
tranmitted to the prop could result in failure of the junction of the
flange and prop, but that it wasn't likely. Analyzing the torque
capacity of of the junction would involve using the bearing strength
of counterbored bushings.only. The reason that wooden props crack and
separate when the bolt torque is not maintained, is because of the
loss of preload stress that reduces the cyclic loading of the prop and
the bolts. Bolts that are highly preloaded have much better fatigue
resistance than ones that are not. The same is true of the prop hub.
Preloading the bolts and hub greatly improves the fatigue life of
both, and that is why reduced bolt torque reduces the fatigue strength
of the parts. Metal that is loaded in a cyclic manner from tension and
then compresion and back and forth, have a much lower time to failure
than metal that is loaded only in tension or compression, even when
the maximum load for the different scenarios is the same. Propellars
and engine parts have this problem big time, more than most anything I
can think of. So it is the loss of preload in the material, not the
loss of friction that causes the props to "eventually" fail, when
proper bolt torque is not maintained.

Regards,
Bud

[Morgans[_2_]]

<>> > So you are correct that friction is used in tranferring torque in
>> > wooden props. They also use counterbored drive bushings to transfer
>> > the torque. I'd be willing to bet that the bushings transfer most of
>> > it, but that is only a guess.
>>
>> Thanks.
>> --
>> Jim in NC
>
> I spent some time talking today at lunch with some friends who are
> structural engineers, about this issue of friction delivering torque
> to the prop. They said that if the strength of the attachment of the
> prop to the flange had been determined through experience, then
> eliminating the friction load path for the engine torque to be
> tranmitted to the prop could result in failure of the junction of the
> flange and prop, but that it wasn't likely.

I'll bet that you structural engineer friends are not experienced with wood
props, and their failure modes. It seems to be their own unique circumstance.
It has been found that the props fail, not the bolts.
--
Jim in NC

[Cy Galley]

The big reason for the "drive lugs" is to remove the nuts from the airstream
in back of the prop and reduce the drag the produce. If they are the only
drive mechanism, the recessed holes will quickly be beat out. If they did
do the job, you could have one center bolt. Many props such as used on A-65
don't even have drive lugs but use bolts straight thru.


--
Cy Galley - Chair,
AirVenture Emergency Aircraft Repair
A 46 Year Service Project of Chapter 75
EAA Safety Programs Editor - TC
EAA Sport Pilot


"Morgans" > wrote in message
...
>
> <>> > So you are correct that friction is used in tranferring torque
> in
>>> > wooden props. They also use counterbored drive bushings to transfer
>>> > the torque. I'd be willing to bet that the bushings transfer most of
>>> > it, but that is only a guess.
>>>
>>> Thanks.
>>> --
>>> Jim in NC
>>
>> I spent some time talking today at lunch with some friends who are
>> structural engineers, about this issue of friction delivering torque
>> to the prop. They said that if the strength of the attachment of the
>> prop to the flange had been determined through experience, then
>> eliminating the friction load path for the engine torque to be
>> tranmitted to the prop could result in failure of the junction of the
>> flange and prop, but that it wasn't likely.
>
> I'll bet that you structural engineer friends are not experienced with
> wood props, and their failure modes. It seems to be their own unique
> circumstance. It has been found that the props fail, not the bolts.
> --
> Jim in NC

[[email protected]]

On Aug 22, 4:21 pm, "Cy Galley" > wrote:
> The big reason for the "drive lugs" is to remove the nuts from the airstream
> in back of the prop and reduce the drag the produce. If they are the only
> drive mechanism, the recessed holes will quickly be beat out. If they did
> do the job, you could have one center bolt. Many props such as used on A-65
> don't even have drive lugs but use bolts straight thru.
>
> --
> Cy Galley - Chair,
> AirVenture Emergency Aircraft Repair
> A 46 Year Service Project of Chapter 75
> EAA Safety Programs Editor - TC
> EAA Sport Pilot
>
> "Morgans" > wrote in message
>
> ...
>
>
>
>
>
> > <>> > So you are correct that friction is used in tranferring torque
> > in
> >>> > wooden props. They also use counterbored drive bushings to transfer
> >>> > the torque. I'd be willing to bet that the bushings transfer most of
> >>> > it, but that is only a guess.
>
> >>> Thanks.
> >>> --
> >>> Jim in NC
>
> >> I spent some time talking today at lunch with some friends who are
> >> structural engineers, about this issue of friction delivering torque
> >> to the prop. They said that if the strength of the attachment of the
> >> prop to the flange had been determined through experience, then
> >> eliminating the friction load path for the engine torque to be
> >> tranmitted to the prop could result in failure of the junction of the
> >> flange and prop, but that it wasn't likely.
>
> > I'll bet that you structural engineer friends are not experienced with
> > wood props, and their failure modes. It seems to be their own unique
> > circumstance. It has been found that the props fail, not the bolts.
> > --
> > Jim in NC- Hide quoted text -
>
> - Show quoted text -

I talked some more to my structures friends. They said that wood
reacts to cyclic stress in much the same manner as metal. It is also
an elastic material (unless overloaded) and it also will fatigue more
quickly when cycled back and forth from tension to compression than it
will from repeated tension or compression alone. So the same
preloading to improve the fatigue life applies to wood as it does to
metal. Lower preload results in a lower fatigue life.
So the "drive" lugs are really low drag lugs? I doubt it very
much. I've read alot about airplanes, and this is the first I've heard
on that one. The most highly stressed part on the whole airplane is
the propellar attachment. Any design utilized here must take care of
that issue first and foremost. The drive lugs are better than plain
nuts and bolts for at least two reasons. First, counterboring the back
of the wooden prop hub to allow the insertion of the lugs results in a
larger diameter hole in the wood, therefore a larger bearing surface
which improves the load capacity. Second, it utilizes the fact that
for elastic materials, the bearing strength is usually about 3 times
as much as the shear strength, and the drive lugs use the bearing
strength and any friction between the crankshaft flange and the back
face of the prop will test the shear strength of the wood. A
crankshaft flange 6" in diameter will have a little more than 28 sq in
of contact area. For a prop this size, the hub should be at least 4 in
thick. with a 3/4" dia drive lug, this will give you about 18 to 20 sq
in of bearing area. Given that the only place where friction will be
great due to bolt tension will be close to the bolts, as the slight
warping of both flange and wood, comparing the two scenarios easily
shows that using the bearing strength of the wood with the drive
bushings is far stronger, and much more reliable.
As to some props such as C-65 cont having no drive lugs, this is
not surprising on old, low powered engines. I have installed a prop on
an old Cub, and one of the things that you had to be careful about,
was making sure the bolts had a slight drive fit to them through the
wood. This is really the same setup as as bushings, just that the
bolts bear against the wood instead of the bushings. More modern
designs with higher horsepower (Katana, etc) use drive bushings to
make the holes larger and and a more precise fit. All higher
horsepower modern props use drive bushings. There is a reason for
that. It is because it is a better way of doing a very critical joint.
One of the people I talked to is a Boeing Technical Fellow, the
highest level an engineer can achieve there. He said that in all his
years, he has only heard of one instance where friction was used to
qualify a structural joint. It was for some trivial thing like an
adjustment slot for a secondary structure part (like the slot for
adjusting the belt tension on some alternators).
I hope that homebuilders that read RAH seeking help will take
Fortunat1's advice from the building manuals he quoted, and realize
that thinking that you can rely on friction to hold the wing joint
together may get you killed. This is even more true of propellars,
where the cyclic loads are severe and constant.

Regards,
Bud

[Fred the Red Shirt]

On Aug 12, 11:09 am, Fortunat1 > wrote:
> ...
> I'll just have to get a good
> quality reamer and prepare each hole carefully. I'll see if I can get a
> drill bit that brings he holes a little closer to the final size.

May I suggest you get more than one drill bit, for the same
reason you need more than one reamer?

..What is the annealing temperature for 4130? You can drill through
a bandsaw blade by spot annealing it, that is you chuck a blunt rod
like a nail with the point ground off into a drill press bring that to
bear
on the spot to be drilled until it gets good and hot, then let it
cool
slowly. Now the spot is annealed and a hole can be drilled with
an ordinary bit.

So I wonder if re-drilling the holes will heat them to the annealing
temperature? Or would it be feasible to spin a rod in the holes
to heat them by friction to soften them? Or would that just
work-harden the surface....

---

FF

[Fred the Red Shirt]

On Aug 17, 2:50 am, Charles Vincent > wrote:
> Fortunat1 wrote:
> > "Rich S." > wrote in
> :
>
> >> "Fortunat1" > wrote in message
> .. .
> >>> Well, obviously I'd protect it, but I'm not going to rely on epoxy to
> >>> bear a load. If I can't get the holes 100% I'll bush them....
>
>...So I guess I'l just be as careful as I can cutting the holes. Just
> > looking through Bengelis' book, I see he recommends using a twist drill to
> > cut the holes, presumably to their final size,...
>
> I would test that theory first. Reamers may or may not give a good
> finish on wood. That was one of the reasons I quoted the study I did.
> The twist drill gave the best hole finish.
>

Bits made for wood, high quality brad-point or forstner bits,
may give you a cleaner hole than a twist drill made for metal.
Cheap bits are crap-they'll burn their way through the wood.

As a rule of thumb, when working wood, use tools made for
woodworking. Duh!

Wood expands and contracts with changes in humidity and
it does so anisotropically. E.g. a flat-sawn board will
have the highest expansion rate accross it's width, less through
its thickness, and minimal along it's length. Quarter sawn or
vertically grained wood, which is what you usually want for
a spar cap, will have those first two rates reversed.

What this means is that if you drill a perfectly circular hole
in a piece of wood, as soon as the humidity changes it
becomes an oval hole. The same is true of a wooden dowel.

Wood finishes slow the rate at which wood absorbs or
releases moisture to the air so as to prevent moisture
gradients through the interior of the wood, which minimizes
e warpage. But all wood finishes are permeable to some
degree to water vapor.

So don't get too crazy about making the hole perfect. I think
the epoxy approach is a good idea.

--

FF

[Gunny]

On Aug 22, 2:55 am, "Morgans" > wrote:
>
> I'll bet that you structural engineer friends are not experienced with wood
> props, and their failure modes. It seems to be their own unique circumstance.
> It has been found that the props fail, not the bolts.
> --
> Jim in NC

Jim,

I share your skepticism. As a structural engineer, I am also curious
about the statement that friction is only considered when it works
against you. It's not clear to me whether these were aircraft
structural engineers or otherwise, so I'll have to give Bud the
benefit of the doubt. However, Chris Heintz, designer of the Zenith
aircraft, that has stated that the reason fatigue isn't much of a
problem for the rivets in the aircraft skin is because the friction
between the joined surfaces typically carries the cyclic loads from
engine vibration (See "Riveted Joints", Chris Heintz, P.E.). I won't
speak to use in aircraft, but in general construction friction is
often considered a working part of the structure.

In fact, there are many instances in steel structures where service
loads are transmitted purely by static friction - moment connections,
end restraints for slender columns, connections with slotted/oversized
holes to facilitate assembly. Bearing/shear of the bolts is obviously
checked, but day-to-day the loads in those structures are transmitted
via static friction between the members. By design. AISC references
these as slip-critical connections. HSFG (High Strength Friction Grip)
is another term. Due to construction methods and tolerances, those
connections may only have one bolt out of the whole group that is
technically "bearing", maybe none. My point is that friction as a
mechanism for transferring loads to a wood prop is not really all that
unique or unusual as an engineering concept.

To address an earlier part of the thread, however, I wouldn't count on
friction for a wood-spar attach fitting. The fittings are often made
from thin material. Out-of-plane bending prevents the fitting from
developing much friction away from the bolt holes. And you have
humidity changes constantly modifying your wood dimensions. Tried-and-
true phenolic bushings, match drilled and reamed to the fittings, cost
about a dollar per hole. In the plane I'm building, that is less than
$50, so it was an easy choice to make.

Another statement that doesn't sit well was the reasoning that a pre-
tensioned bolt has better fatigue characteristics because metal
fatigues less when the stress cycle is all in tension as compared to
stress reversal. This is a clear misunderstanding of the factors in
play. Study the S-N diagrams of these materials and you will see that
increasing the mean stress decreases the fatigue life for a given
stress cycle amplitude. The reason some pre-tensioned bolted
connections (esp. shear) have better fatigue characteristics is
because the cyclic portion of the load is transfered via friction. The
bolt actually experiences a drastically reduced or eliminated cyclic
stress, thereby extending it's fatigue life even though the mean
stress of the bolt is much higher. Tension connections see improvement
through a different mechanism, but the result is the same - reduced
cyclic stress in the bolt and increased fatigue life.

Matt, P.E.

[Morgans[_2_]]

"Gunny" < wrote
>
> To address an earlier part of the thread, however, I wouldn't count on
> friction for a wood-spar attach fitting. The fittings are often made
> from thin material. Out-of-plane bending prevents the fitting from
> developing much friction away from the bolt holes. And you have
> humidity changes constantly modifying your wood dimensions. Tried-and-
> true phenolic bushings, match drilled and reamed to the fittings, cost
> about a dollar per hole. In the plane I'm building, that is less than
> $50, so it was an easy choice to make.


Oh, I've becomne a believer in that part of the tale. It does make perfect
sense that the plates are not ridgid enough to develop any significant
friction.

There are too many conflicts with what I have read from people who's word I
trust, that props are driven mainly from shear loading.

I remember a few months back, that one of the guys on the group
(occasionally) that works at Scaled Composite in an important capacity,
threw the prop on his (vary-easy ?) There were warning signs, as I recall,
that were missed before it flew off.

A top Boeing engineer is not likely to have enough experience with wood
props to make his word more valid than the local guy at the airport that has
been flying wood props all of his life.

I really don't have a dog in this fight. I'll attempt to let it lay, and
let those out there with a dog in the fight make up there own minds. I
could be all wet, but if I am, I have badly misunderstood some reading I
have done.
--
Jim in NC

[[email protected]]

On Aug 24, 1:38 pm, Gunny > wrote:
> On Aug 22, 2:55 am, "Morgans" > wrote:
>
>
>
> > I'll bet that you structural engineer friends are not experienced with wood
> > props, and their failure modes. It seems to be their own unique circumstance.
> > It has been found that the props fail, not the bolts.
> > --
> > Jim in NC
>
> Jim,
>
> I share your skepticism. As a structural engineer, I am also curious
> about the statement that friction is only considered when it works
> against you. It's not clear to me whether these were aircraft
> structural engineers or otherwise, so I'll have to give Bud the
> benefit of the doubt. However, Chris Heintz, designer of the Zenith
> aircraft, that has stated that the reason fatigue isn't much of a
> problem for the rivets in the aircraft skin is because the friction
> between the joined surfaces typically carries the cyclic loads from
> engine vibration (See "Riveted Joints", Chris Heintz, P.E.). I won't
> speak to use in aircraft, but in general construction friction is
> often considered a working part of the structure.
>
> In fact, there are many instances in steel structures where service
> loads are transmitted purely by static friction - moment connections,
> end restraints for slender columns, connections with slotted/oversized
> holes to facilitate assembly. Bearing/shear of the bolts is obviously
> checked, but day-to-day the loads in those structures are transmitted
> via static friction between the members. By design. AISC references
> these as slip-critical connections. HSFG (High Strength Friction Grip)
> is another term. Due to construction methods and tolerances, those
> connections may only have one bolt out of the whole group that is
> technically "bearing", maybe none. My point is that friction as a
> mechanism for transferring loads to a wood prop is not really all that
> unique or unusual as an engineering concept.
>
> To address an earlier part of the thread, however, I wouldn't count on
> friction for a wood-spar attach fitting. The fittings are often made
> from thin material. Out-of-plane bending prevents the fitting from
> developing much friction away from the bolt holes. And you have
> humidity changes constantly modifying your wood dimensions. Tried-and-
> true phenolic bushings, match drilled and reamed to the fittings, cost
> about a dollar per hole. In the plane I'm building, that is less than
> $50, so it was an easy choice to make.
>
> Another statement that doesn't sit well was the reasoning that a pre-
> tensioned bolt has better fatigue characteristics because metal
> fatigues less when the stress cycle is all in tension as compared to
> stress reversal. This is a clear misunderstanding of the factors in
> play. Study the S-N diagrams of these materials and you will see that
> increasing the mean stress decreases the fatigue life for a given
> stress cycle amplitude. The reason some pre-tensioned bolted
> connections (esp. shear) have better fatigue characteristics is
> because the cyclic portion of the load is transfered via friction. The
> bolt actually experiences a drastically reduced or eliminated cyclic
> stress, thereby extending it's fatigue life even though the mean
> stress of the bolt is much higher. Tension connections see improvement
> through a different mechanism, but the result is the same - reduced
> cyclic stress in the bolt and increased fatigue life.
>
> Matt, P.E.

Thanks for your comments, and before I put my comments on this
thread to bed, I want to say that the OP asked a question or two that
have been answered very well, and that is what this group is for. Even
I have learned things about working with wood. Anyone reading this
thread looking for info will find the correct way to construct a wing
joint.
As to whether or not the engineers I talked to were aircraft
engineers, most definately they are.
As to some of your comments, I need to clarify some things. If
you are a civil engineer that deals with steel structures, and you
have design and analysis standards that use friction to qualify
structure, then that is your way to do it. I don't recall seeing a
major building , bridge, etc, that wasn't either riveted or welded
together, but I don't know for sure. So I will take your word for it.
I stated in my first post that friction existed and carried load, but
simply that for aerospace structures it is never counted on to carry
load. You only consider friction when it works against you. That I
know is true. In your statements about why using friction in the wood
spar joint is not a good idea, I think you have begun to uncover some
of the reasons why it is true. Since most airframes are thin shell
material, most of these reasons apply just as well to metal as wood.
As to the statement that I clearly don't understand the factors
involved, you clearly do not understand what I said, the nature of
preloaded bolts, or even the S-n curves themselves. Improved fatigue
life due to preloading has nothing to do with friction. Friction may
improve fatigue life in the real world by spreading load over a larger
area, but the benefit of preloading on fatigue life is due primarily
to an effect that exists even if no friction is present at all. Why
you think I need it pointed out that higher stress levels result in
shorter fatigue life is puzzling. Of course the higher the load you
place on a structure, the fewer cycles it will survive before failure.
What is hard to understand about that? What you apparently don't
understand is what constitutes a load cycle, how much is the load, and
what preload does to that. Preloading the bolt reduces the cyclic load
that it sees, since the load in a preloaded bolt only increases about
10% until the applied load exceeds the preload. When the prop bolts
are allowed to lose their preload, the full applied load becomes the
amount of cyclic load that causes fatigue. This is best demonstrated
by giving an example. Take two identical bolts, having a breaking
strength of 5,000 lbs each, and preload one to 2000 lbs, and none to
the other. If we now begin to subject both bolts to the same cyclic
loading of 1500 lbs, where the applied load is increased from 0 up to
1500 and then reduced to zero again, the bolt with the 2000 lb preload
will see a cyclic load of only about 150 lbs, whereas the un-preloaded
bolt will see a cyclic load of 1500 lbs, and will obviously fail much
sooner. Same bolts, same loads. The meaning of this is that if you
keep the prop bolts properly preloaded or torqued as it is, then BOTH
the bolts and the prop hub see a much smaller cyclic fatigue load than
if you allow them to become loose, thereby greatly increasing the
cyclic load that they see, and increasing likelyhood of failure.
As for S-n curves, there are more than one type. The one
relating to what I am talking about are the ones that show S vs N for
different stress ratios. The stress ratio is the fraction equivalent
of the maximum to minimum load. For example, something that is loaded
in tension to 25000 psi, followed by being loaded in compression to
25000 psi back and forth, will have a ratio of -1.0 ( +25000 tension/
-25000 compression). Something loaded to 25000 psi tension that is
reduced to 10000 psi tension and back and forth will have a stress
ratio of .4 (10000 tension/ 25000 tension). The S-n curves show that
the amount of cyclic load that structure loaded with a ratio of -1
will fail far sooner than one with a ratio of .4, even though the
maximum stress level is the same. You can look in Mil-Hnbk-5 or
elsewhere for S-n curves to verify that.
The best book to explain all this is "Mechanical Engineering
Design" by Joseph Edward Shigley, Professor at the University of
Michigan, chapter 8, "Design of Screws, Fasteners, and Connections".
It is THE most widely used text on the subject in the top engineering
schools of the country, and has been for many years.

Regards,
Bud
M.S. Aerospace Engineering

[[email protected]]

On Aug 24, 1:38 pm, Gunny > wrote:
> On Aug 22, 2:55 am, "Morgans" > wrote:
>
>
>
> > I'll bet that you structural engineer friends are not experienced with wood
> > props, and their failure modes. It seems to be their own unique circumstance.
> > It has been found that the props fail, not the bolts.
> > --
> > Jim in NC
>
> Jim,
>
> I share your skepticism. As a structural engineer, I am also curious
> about the statement that friction is only considered when it works
> against you. It's not clear to me whether these were aircraft
> structural engineers or otherwise, so I'll have to give Bud the
> benefit of the doubt. However, Chris Heintz, designer of the Zenith
> aircraft, that has stated that the reason fatigue isn't much of a
> problem for the rivets in the aircraft skin is because the friction
> between the joined surfaces typically carries the cyclic loads from
> engine vibration (See "Riveted Joints", Chris Heintz, P.E.). I won't
> speak to use in aircraft, but in general construction friction is
> often considered a working part of the structure.
>
> In fact, there are many instances in steel structures where service
> loads are transmitted purely by static friction - moment connections,
> end restraints for slender columns, connections with slotted/oversized
> holes to facilitate assembly. Bearing/shear of the bolts is obviously
> checked, but day-to-day the loads in those structures are transmitted
> via static friction between the members. By design. AISC references
> these as slip-critical connections. HSFG (High Strength Friction Grip)
> is another term. Due to construction methods and tolerances, those
> connections may only have one bolt out of the whole group that is
> technically "bearing", maybe none. My point is that friction as a
> mechanism for transferring loads to a wood prop is not really all that
> unique or unusual as an engineering concept.
>
> To address an earlier part of the thread, however, I wouldn't count on
> friction for a wood-spar attach fitting. The fittings are often made
> from thin material. Out-of-plane bending prevents the fitting from
> developing much friction away from the bolt holes. And you have
> humidity changes constantly modifying your wood dimensions. Tried-and-
> true phenolic bushings, match drilled and reamed to the fittings, cost
> about a dollar per hole. In the plane I'm building, that is less than
> $50, so it was an easy choice to make.
>
> Another statement that doesn't sit well was the reasoning that a pre-
> tensioned bolt has better fatigue characteristics because metal
> fatigues less when the stress cycle is all in tension as compared to
> stress reversal. This is a clear misunderstanding of the factors in
> play. Study the S-N diagrams of these materials and you will see that
> increasing the mean stress decreases the fatigue life for a given
> stress cycle amplitude. The reason some pre-tensioned bolted
> connections (esp. shear) have better fatigue characteristics is
> because the cyclic portion of the load is transfered via friction. The
> bolt actually experiences a drastically reduced or eliminated cyclic
> stress, thereby extending it's fatigue life even though the mean
> stress of the bolt is much higher. Tension connections see improvement
> through a different mechanism, but the result is the same - reduced
> cyclic stress in the bolt and increased fatigue life.
>
> Matt, P.E.

Thanks for your comments, and before I put my comments on this
thread to bed, I want to say that the OP asked a question or two that
have been answered very well, and that is what this group is for. Even
I have learned things about working with wood. Anyone reading this
thread looking for info will find the correct way to construct a wing
joint.
As to whether or not the engineers I talked to were aircraft
engineers, most definately they are.
As to some of your comments, I need to clarify some things. If
you are a civil engineer that deals with steel structures, and you
have design and analysis standards that use friction to qualify
structure, then that is your way to do it. I don't recall seeing a
major building , bridge, etc, that wasn't either riveted or welded
together, but I don't know for sure. So I will take your word for it.
I stated in my first post that friction existed and carried load, but
simply that for aerospace structures it is never counted on to carry
load. You only consider friction when it works against you. That I
know is true. In your statements about why using friction in the wood
spar joint is not a good idea, I think you have begun to uncover some
of the reasons why it is true. Since most airframes are thin shell
material, most of these reasons apply just as well to metal as wood.
As to the statement that I clearly don't understand the factors
involved, you clearly do not understand what I said, the nature of
preloaded bolts, or even the S-n curves themselves. Improved fatigue
life due to preloading has nothing to do with friction. Friction may
improve fatigue life in the real world by spreading load over a larger
area, but the benefit of preloading on fatigue life is due primarily
to an effect that exists even if no friction is present at all. Why
you think I need it pointed out that higher stress levels result in
shorter fatigue life is puzzling. Of course the higher the load you
place on a structure, the fewer cycles it will survive before failure.
What is hard to understand about that? What you apparently don't
understand is what constitutes a load cycle, how much is the load, and
what preload does to that. Preloading the bolt reduces the cyclic load
that it sees, since the load in a preloaded bolt only increases about
10% until the applied load exceeds the preload. When the prop bolts
are allowed to lose their preload, the full applied load becomes the
amount of cyclic load that causes fatigue. This is best demonstrated
by giving an example. Take two identical bolts, having a breaking
strength of 5,000 lbs each, and preload one to 2000 lbs, and none to
the other. If we now begin to subject both bolts to the same cyclic
loading of 1500 lbs, where the applied load is increased from 0 up to
1500 and then reduced to zero again, the bolt with the 2000 lb preload
will see a cyclic load of only about 150 lbs, whereas the un-preloaded
bolt will see a cyclic load of 1500 lbs, and will obviously fail much
sooner. Same bolts, same loads. The meaning of this is that if you
keep the prop bolts properly preloaded or torqued as it is, then BOTH
the bolts and the prop hub see a much smaller cyclic fatigue load than
if you allow them to become loose, thereby greatly increasing the
cyclic load that they see, and increasing likelyhood of failure.
As for S-n curves, there are more than one type. The one
relating to what I am talking about are the ones that show S vs N for
different stress ratios. The stress ratio is the fraction equivalent
of the maximum to minimum load. For example, something that is loaded
in tension to 25000 psi, followed by being loaded in compression to
25000 psi back and forth, will have a ratio of -1.0 ( +25000 tension/
-25000 compression). Something loaded to 25000 psi tension that is
reduced to 10000 psi tension and back and forth will have a stress
ratio of .4 (10000 tension/ 25000 tension). The S-n curves show that
the amount of cyclic load that structure loaded with a ratio of -1
will fail far sooner than one with a ratio of .4, even though the
maximum stress level is the same. You can look in Mil-Hnbk-5 or
elsewhere for S-n curves to verify that.
The best book to explain all this is "Mechanical Engineering
Design" by Joseph Edward Shigley, Professor at the University of
Michigan, chapter 8, "Design of Screws, Fasteners, and Connections".
It is THE most widely used text on the subject in the top engineering
schools of the country, and has been for many years.

Regards,
Bud
M.S. Aerospace Engineering

[Morgans[_2_]]

> wrote

> The best book to explain all this is "Mechanical Engineering
> Design" by Joseph Edward Shigley, Professor at the University of
> Michigan, chapter 8, "Design of Screws, Fasteners, and Connections".
> It is THE most widely used text on the subject in the top engineering
> schools of the country, and has been for many years.

Hell, that explains it, when I see what your source material is from! <BFG>
--
Jim in NC

Ohio State University Alum, and former 5 year marching band member.

Go Bucks!

[Morgans[_2_]]

> Hell, that explains it, when I see what your source material is from!
> <BFG>
> --
> Jim in NC
>
> Ohio State University Alum, and former 5 year marching band member.
>
> Go Bucks!

Oh, and I forgot to add, "Muck Fichigan! "

[[email protected]]

On Aug 25, 1:17 pm, "Morgans" > wrote:
> > Hell, that explains it, when I see what your source material is from!
> > <BFG>
> > --
> > Jim in NC
>
> > Ohio State University Alum, and former 5 year marching band member.
>
> > Go Bucks!
>
> Oh, and I forgot to add, "Muck Fichigan! "

I didn't attend Michigan, its just a great book ;).

Bud

[Fortunat1[_18_]]

Fred the Red Shirt > wrote in
ups.com:

> On Aug 17, 2:50 am, Charles Vincent > wrote:
>> Fortunat1 wrote:
>> > "Rich S." > wrote in
>> :
>>
>> >> "Fortunat1" > wrote in message
>> .. .
>> >>> Well, obviously I'd protect it, but I'm not going to rely on
>> >>> epoxy to bear a load. If I can't get the holes 100% I'll bush
>> >>> them....
>>
>>...So I guess I'l just be as careful as I can cutting the holes. Just
>> > looking through Bengelis' book, I see he recommends using a twist
>> > drill to cut the holes, presumably to their final size,...
>>
>> I would test that theory first. Reamers may or may not give a good
>> finish on wood. That was one of the reasons I quoted the study I
>> did. The twist drill gave the best hole finish.
>>
>
> Bits made for wood, high quality brad-point or forstner bits,
> may give you a cleaner hole than a twist drill made for metal.
> Cheap bits are crap-they'll burn their way through the wood.
>

Actauly, having tried each on some scrap pieces of spruce, the twist
drill gave the best finished hole and the roundest hole by a long shot.
The 5/16th bolt was a perfect fit after having used a an 8mm twist
drill.


> As a rule of thumb, when working wood, use tools made for
> woodworking. Duh!

Yes, mostly I do, but in this case, I'll use what works best! I found
the woood bit went a bit eccentric as it went through giving a slightly
tapered bore as it went through.
>
> Wood expands and contracts with changes in humidity and
> it does so anisotropically. E.g. a flat-sawn board will
> have the highest expansion rate accross it's width, less through
> its thickness, and minimal along it's length. Quarter sawn or
> vertically grained wood, which is what you usually want for
> a spar cap, will have those first two rates reversed.
>
> What this means is that if you drill a perfectly circular hole
> in a piece of wood, as soon as the humidity changes it
> becomes an oval hole. The same is true of a wooden dowel.
>
> Wood finishes slow the rate at which wood absorbs or
> releases moisture to the air so as to prevent moisture
> gradients through the interior of the wood, which minimizes
> e warpage. But all wood finishes are permeable to some
> degree to water vapor.
>
> So don't get too crazy about making the hole perfect. I think
> the epoxy approach is a good idea.
>

'Kay,. but did the bipes of the thirties have the holes filled in any
way? Lots of them are still flying wth their original spars.
>

[Gunny]

On Aug 25, 7:28 am, wrote:
> As to whether or not the engineers I talked to were aircraft
> engineers, most definately they are.

Like I said, giving you the benefit of the doubt. If they had been
building engineers or bridge engineers I doubt they would have said
that friction isn't a oft used mechanism.

> I stated in my first post that friction existed and carried load, but
> simply that for aerospace structures it is never counted on to carry
> load. You only consider friction when it works against you. That I
> know is true. In your statements about why using friction in the wood
> spar joint is not a good idea, I think you have begun to uncover some
> of the reasons why it is true. Since most airframes are thin shell
> material, most of these reasons apply just as well to metal as wood.

Yes, I was agreeing with you.

> As to the statement that I clearly don't understand the factors
> involved, you clearly do not understand what I said, the nature of
> preloaded bolts, or even the S-n curves themselves. Improved fatigue
> life due to preloading has nothing to do with friction. Friction may
> improve fatigue life in the real world by spreading load over a larger
> area, but the benefit of preloading on fatigue life is due primarily
> to an effect that exists even if no friction is present at all.

That is true in tension splices, but not in shear splices.

> Why
> you think I need it pointed out that higher stress levels result in
> shorter fatigue life is puzzling. Of course the higher the load you
> place on a structure, the fewer cycles it will survive before failure.
> What is hard to understand about that? What you apparently don't
> understand is what constitutes a load cycle, how much is the load, and
> what preload does to that. Preloading the bolt reduces the cyclic load
> that it sees, since the load in a preloaded bolt only increases about
> 10% until the applied load exceeds the preload.

You said:

"It is also an elastic material (unless overloaded) and it also
will fatigue
more quickly when cycled back and forth from tension to
compression
than it will from repeated tension or compression alone."

Bud, that statement is wrong in so many cases that it had to be
pointed out. A member experiencing a 60 ksi swing from from -30 ksi to
30 ksi axial force vs a member experiencing a swing from 0 to 60 ksi
would meet the parameters laid out in your sentence. Both are
experiencing a 60 ksi cyclic load. However, the member all in tension
is due to fail first, completely contrary to what your statement says.

It sounded suspiciously like the guys who neglect to do fatigue checks
on a member because there wasn't a stress reversal. That's why I
jumped on it. If you had qualified that statement better, I could have
accepted it.

Depending on the elasticity and thicknesses of the materials being
fastened, my experience is that reduction to 10% of the original cycle
is not a given and would typically be very optimistic. This can be
especially true of a wood member clamped with a steel bolt.

> When the prop bolts
> are allowed to lose their preload, the full applied load becomes the
> amount of cyclic load that causes fatigue. This is best demonstrated
> by giving an example. Take two identical bolts, having a breaking
> strength of 5,000 lbs each, and preload one to 2000 lbs, and none to
> the other. If we now begin to subject both bolts to the same cyclic
> loading of 1500 lbs, where the applied load is increased from 0 up to
> 1500 and then reduced to zero again, the bolt with the 2000 lb preload
> will see a cyclic load of only about 150 lbs, whereas the un-preloaded
> bolt will see a cyclic load of 1500 lbs, and will obviously fail much
> sooner. Same bolts, same loads. The meaning of this is that if you
> keep the prop bolts properly preloaded or torqued as it is, then BOTH
> the bolts and the prop hub see a much smaller cyclic fatigue load than
> if you allow them to become loose, thereby greatly increasing the
> cyclic load that they see, and increasing likelyhood of failure.

You've described the preload mechanism behind a typical tension
splice. As I said above, the reduction in cyclic stress is dependent
on elasticity and thickness of the members being bolted together. I
alluded to that mechanism in my previous post. I didn't elaborate on
it, because I'm not convinced that it any bearing in a wood propeller
attachment, where the shear between prop and the hub faces is what is
causing the failure. If you ignore friction, then how else does pre-
loading the bolt help? The force in the bolt is effectively
perpendicular to the shear, until which time the bolt has bent over
substantially.

> As for S-n curves, there are more than one type. The one
> relating to what I am talking about are the ones that show S vs N for
> different stress ratios. The stress ratio is the fraction equivalent
> of the maximum to minimum load. For example, something that is loaded
> in tension to 25000 psi, followed by being loaded in compression to
> 25000 psi back and forth, will have a ratio of -1.0 ( +25000 tension/
> -25000 compression). Something loaded to 25000 psi tension that is
> reduced to 10000 psi tension and back and forth will have a stress
> ratio of .4 (10000 tension/ 25000 tension). The S-n curves show that
> the amount of cyclic load that structure loaded with a ratio of -1
> will fail far sooner than one with a ratio of .4, even though the
> maximum stress level is the same. You can look in Mil-Hnbk-5 or
> elsewhere for S-n curves to verify that.

These are precisely the diagrams to which I am referring. Your example
seems somewhat contrived, however. How would a bolt achieve a stress
ratio of -1 in axial loading (ie, as specified in your example above)?
It is also a stretch to say that the maximum stress would remain the
same. Both variables change, and maybe only one time in ten would pre-
load push it outside the gamut of acceptable values, but that is
enough to void any blanket statement such as above.

If your argument is that you were discussing +/- shear, then how
exactly does the axial pre-load (substantially) affect the cyclic
shear loading? We have frictionless mating surfaces in your examples
remember, and the pre-tensioning is perpendicular to the developed
shear.

> The best book to explain all this is "Mechanical Engineering
> Design" by Joseph Edward Shigley, Professor at the University of
> Michigan, chapter 8, "Design of Screws, Fasteners, and Connections".
> It is THE most widely used text on the subject in the top engineering
> schools of the country, and has been for many years.

MTU alum. Got it.

> Regards,
> Bud
> M.S. Aerospace Engineering

[Fred the Red Shirt]

On Aug 26, 12:59 am, Fortunat1 > wrote:
> Fred the Red Shirt > wrote roups.com:
>
> ...
>
> > Bits made for wood, high quality brad-point or forstner bits,
> > may give you a cleaner hole than a twist drill made for metal.
> > Cheap bits are crap-they'll burn their way through the wood.
>
> Actauly, having tried each on some scrap pieces of spruce, the twist
> drill gave the best finished hole and the roundest hole by a long shot.
> The 5/16th bolt was a perfect fit after having used a an 8mm twist
> drill.
>
> > As a rule of thumb, when working wood, use tools made for
> > woodworking. Duh!
>
> Yes, mostly I do, but in this case, I'll use what works best! I found
> the woood bit went a bit eccentric as it went through giving a slightly
> tapered bore as it went through.
>
>

Was that with a forstner bit or a brad point bit?

>
> > So don't get too crazy about making the hole perfect. I think
> > the epoxy approach is a good idea.
>
> 'Kay,. but did the bipes of the thirties have the holes filled in any
> way? Lots of them are still flying wth their original spars.
>

I doubt if they did. OTOH, they didn't HAVE epoxy, else they
would have used it.

--

FF

[Fred the Red Shirt]

....

Note that stress is the distribution of force in a material.
This discussion requires that one address the stress in
the materials, not just the applied force. 'Load' usually
refers to force, but may also refer to the stress in the
material that results from that force. I have tried to
use the terms force and stress properly, but may have
slipped up. If so, I apologize in advance.

Some of the previous discussion has addressed fastening
thin materials, like sheet metal while other parts have
addressed thicker sections like the joint of a prop to
a prop hub.

Some of the preceding folks have stated perfectly valid
examples, but of mechanically different structures.

On Aug 25, 12:28 pm, wrote:
> On Aug 24, 1:38 pm, Gunny > wrote:
>
> ...
>
> > ... t the reason fatigue isn't much of a
> > problem for the rivets in the aircraft skin is because the friction
> > between the joined surfaces typically carries the cyclic loads from
> > engine vibration (See "Riveted Joints", Chris Heintz, P.E.). I won't
> > speak to use in aircraft, but in general construction friction is
> > often considered a working part of the structure.
>
> > In fact, there are many instances in steel structures where service
> > loads are transmitted purely by static friction - moment connections,
> > end restraints for slender columns, connections with slotted/oversized
> > holes to facilitate assembly. Bearing/shear of the bolts is obviously
> > checked, but day-to-day the loads in those structures are transmitted
> > via static friction between the members. By design. AISC references
> > these as slip-critical connections. HSFG (High Strength Friction Grip)
> > is another term. Due to construction methods and tolerances, those
> > connections may only have one bolt out of the whole group that is
> > technically "bearing", maybe none. My point is that friction as a
> > mechanism for transferring loads to a wood prop is not really all that
> > unique or unusual as an engineering concept.
>
> > To address an earlier part of the thread, however, I wouldn't count on
> > friction for a wood-spar attach fitting. The fittings are often made
> > from thin material. Out-of-plane bending prevents the fitting from
> > developing much friction away from the bolt holes. And you have
> > humidity changes constantly modifying your wood dimensions. Tried-and-
> > true phenolic bushings, match drilled and reamed to the fittings, cost
> > about a dollar per hole. In the plane I'm building, that is less than
> > $50, so it was an easy choice to make.
>

Perhaps one should also check the bolt tension frequently.

> > Another statement that doesn't sit well was the reasoning that a pre-
> > tensioned bolt has better fatigue characteristics because metal
> > fatigues less when the stress cycle is all in tension as compared to
> > stress reversal. This is a clear misunderstanding of the factors in
> > play. Study the S-N diagrams of these materials and you will see that
> > increasing the mean stress decreases the fatigue life for a given
> > stress cycle amplitude. The reason some pre-tensioned bolted
> > connections (esp. shear) have better fatigue characteristics is
> > because the cyclic portion of the load is transfered via friction. The
> > bolt actually experiences a drastically reduced or eliminated cyclic
> > stress, thereby extending it's fatigue life even though the mean
> > stress of the bolt is much higher. Tension connections see improvement
> > through a different mechanism, but the result is the same - reduced
> > cyclic stress in the bolt and increased fatigue life.
>

Correct me if I am mistaken but here Matt is giving us an example
of a bolt that is preloaded in tension and then stressed (cyclically)
in tension.

That is different from a bolt that is pre-loaded in tension to fasten
two surfaces and then subject to shear, right?

>
> ... Anyone reading this
> thread looking for info will find the correct way to construct a wing
> joint.
> As to whether or not the engineers I talked to were aircraft
> engineers, most definately they are.

Then I submit that there is a discontinuity in communication in
the loop from here to your friends and back to here. We are not
all discussing exactly the same things.

> As to some of your comments, I need to clarify some things. If
> you are a civil engineer that deals with steel structures, and you
> have design and analysis standards that use friction to qualify
> structure, then that is your way to do it. I don't recall seeing a
> major building , bridge, etc, that wasn't either riveted or welded
> together, but I don't know for sure.

Matt made it clear that bolted and riveted structures typically rely
on friction from the clamping force of the fasteners so that the
fasteners themselves typically see very little shear. I believe that
is correct. In particular, and Matt alluded to this problem, imagine
the precision required to evenly distribute the transverse shear
stress over many fasteners over a large surface, and then to
maintain that distribution over changing loads, thermal expansion,
etc.

> So I will take your word for it.
> I stated in my first post that friction existed and carried load, but
> simply that for aerospace structures it is never counted on to carry
> load. You only consider friction when it works against you. That I
> know is true. In your statements about why using friction in the wood
> spar joint is not a good idea, I think you have begun to uncover some
> of the reasons why it is true.

I suggest that relying on the bolts to carry the entire load
without ANY load being carried by friction between the wing
attachment fittings and the wood will concentrate the stress
at the locations of the fasteners. This may well locally stress
the wood to failure, e.g. it may split. The clamping force of
the fitting distributes that load over a larger area reducing the
stress concentrations.

While it is essential that the fasteners be sized to safely carry
the entire load, flying with wing attachment fittings that are so
loosely clamped that they actually DO carry the load is a
likely route to inclusion in an NTSB report.

Wood is anisotropic in its properties. Whatever their other
merits, woods commonly used in aircraft construction for the
most part do not include those with interlocking grain, meaning
that they split easily. To avoid splitting, you want to minimize
tensile across or shear stress along a grain boundary. If you
drill a hole in a piece of wood and apply a load to something
sitting loosely in that hole has much the opposite effect.

> Since most airframes are thin shell
> material, most of these reasons apply just as well to metal as wood.

It is precisely BECAUSE most airframes are thin shell material that
rivets and bolts seldom carry all of the shear at a typical joint.

Imagine two long flat strips of sheet metal laid end-to-
end, but overlapped at their ends. Now drill (and ream!) through
both and bolt or rivet them together. Now pull on the ends.
Simple stress analysis assumes infinite stiffness, that is
it assumes that deformation of the part does not redistribute
the applied loads. For thin materials like aircraft that assumption
is often inapplicable (e.g. bucking is important). But for
this example we assume the sheet metal strips do not bend.

So, the sheet metal strips are both loaded in pure tension.
Does the bolt or rivet now carry the entire load in shear?
Not if it is properly installed! The bolt or rivet clamps the two
pieces of sheet metal together so that the friction between
them does not allow them to move relative to each other.
Since they do not slide accross each other, they carry
some of the load. The shear stress in the joint is equal
to the force in tension divided by the area of overlap.

Now as we increase the tension in the sheet metal from
zero to some higher value, the shear accross the bolt
increases, from zero to some higher value,
but only slightly because much of that load is carried
in the sheet metal. If the cross-sectional area of the
bolt is only one-tenth of the area of overlap, then the
bolt only carries one tenth of the shear stress.

Now if we relax the assumption of infinite stiffness then
the clamping force the fastener applies to the sheet
metal is maximum under the bolt head and rapidly drops
off away from the bolt. But the bolt will still share quite
a bit of the shear with the material being clamped. The
sheet metal will also bend (buckle) near the bolt putting
some additional tension on it but let's continue to ignore
that.

Now, let's also relax the pre-loading in the bolt :-)

The bolt now carries the entire shear load.
The sheet metal will also bend (buckle) near the bolt
putting some tension on it but let's continue to ignore that.

The bearing stress on the inside of the hole in either
piece of sheer metal is zero over 180 degrees of its
cirrcumfrence, and rises to a maximum at a point
centered opposite the unstressed arc. Since this is
thin sheet metal it is easy to see that the force needed
to raise that bearing stress above yield is small relative
to the force needed to yield any part of the properly
fastened joint. IOW, if the bolt is not tight enough,
the hole will become elongated. Not good. A hole
drilled in a thicker but softer material would also
elongate.

Using bushings in a hole drilled in wood helps to reduce
that elongation by spreading that bearing stress over
a larger area in the wood, and is a lighter approach than
simply using a larger bolt. But it is still not a substitute
for maintaining the proper tension in the bolts.

I am far from clear on what constitutes 'proper' for
a metal piece bolted to wood. If the wood is clamped
too tightly, an increase is humidity may overstress it
causing it to split. If too loose, a decrease in humidity
may cause the joint to loosen too much.

> As to the statement that I clearly don't understand the factors
> involved, you clearly do not understand what I said, the nature of
> preloaded bolts, or even the S-n curves themselves. Improved fatigue
> life due to preloading has nothing to do with friction. Friction may
> improve fatigue life in the real world by spreading load over a larger
> area, but the benefit of preloading on fatigue life is due primarily
> to an effect that exists even if no friction is present at all.

Could you please elaborate on the theory of that effect?
E.g. is this a result of the superposition of stresses?

It has been twenty years since I did any serious stress analysis
so I'm not about to elaborate on the superposition problem but
I will point out that as a purely practical matter any properly
torqued bolt will share shear loading with at lest the material
clamped between the bolt head and the nut, and if that material
is not strong enough to bear a significant load then it will
fail before the bolt does.

> Why
> you think I need it pointed out that higher stress levels result in
> shorter fatigue life is puzzling. Of course the higher the load you
> place on a structure, the fewer cycles it will survive before failure.
> What is hard to understand about that? What you apparently don't
> understand is what constitutes a load cycle, how much is the load, and
> what preload does to that. Preloading the bolt reduces the cyclic load
> that it sees, since the load in a preloaded bolt only increases about
> 10% until the applied load exceeds the preload. When the prop bolts
> are allowed to lose their preload, the full applied load becomes the
> amount of cyclic load that causes fatigue. This is best demonstrated
> by giving an example. Take two identical bolts, having a breaking
> strength of 5,000 lbs each, and preload one to 2000 lbs, and none to
> the other.

Here I presume the preload to which you refer is 2,000 lbs of axial
tension in the bolts. If these are 1/4" bolts that imposes a stress
of about 41,000 psi, implying that their ultimate strength is about
100,000 psi which, IIRC, is in the achievable range for high strength
steel.

> If we now begin to subject both bolts to the same cyclic
> loading of 1500 lbs, where the applied load is increased from 0 up to
> 1500 and then reduced to zero again, the bolt with the 2000 lb preload
> will see a cyclic load of only about 150 lbs, whereas the un-preloaded
> bolt will see a cyclic load of 1500 lbs, and will obviously fail much
> sooner.

Here you temporarily lost me because you have not told us
HOW the bolt is loaded. If the load consists of additional
tension, then plainly the bolt will see cyclical stress over the
range of 3500 lb to 2000. That is clearly the type of loading Matt
was discussing. If I make the unremarkable assumption that y
ou are familiar with addition then clearly you are NOT assuming
that the load is applied in the form of additional tension.

However, the clamping force will still cause the shear to be
distributed over the surface area being clamped and not just
through the bolts. The superposition of stresses is not
the total story.

> Same bolts, same loads. The meaning of this is that if you
> keep the prop bolts properly preloaded or torqued as it is, then BOTH
> the bolts and the prop hub see a much smaller cyclic fatigue load than
> if you allow them to become loose, thereby greatly increasing the
> cyclic load that they see, and increasing likelyhood of failure.

If the bolts are allowed to become loose, then all of the shear is
carried by the bolts. If they clamp the prop to the hub, then
almost all of the shear is carried by the friction between the
prop and the hub. A tractor will add a small about of tension
to the bolts, since it pulls in that direction. A pusher will
actually reduce the pre-loading in the bolts by a small amount,
but increase the clamping force between the prop and
the hub. IN neither case do I suppose that the friction between
the prop and the hub makes an insignificant contribution to
the integrity of the joint.

Now. please consider two examples, neither of which is a good way to
make something, but which do allow us to isolate the phenomenum
to pure superpositon of stress.

Lets assume nice thick stiff bars fastened like the sheet metal strips
together as in the first example. But in this case the bars are so
thick and strong that it is the bolt that will fail. Again, we apply
a cyclic
load to the bars, alternately pulling on them and relaxing.

In the first case, the bolt is slipped into the hole and not
tightened.
As the bolt is not tightened, all of the cyclic stress in the bolt
is transverse shear.

In the second case, we coat the underside of the bolt head with
a lubricant and turn the nut up against the head pre-loading the bolt
in pure tension with no material at all clamped in between the nut
and the head. Now we enlarge the hole in the bars so that the
nut nd head will fit inside and align them so that the nut bears
on one bar and the head on the other. ALL of the shear is being
carried by the pre-loaded shank of the bolt.

If a cyclic force is applied to those bars, which bolt fails
first?

> As for S-n curves, there are more than one type. The one
> relating to what I am talking about are the ones that show S vs N for
> different stress ratios. The stress ratio is the fraction equivalent
> of the maximum to minimum load. For example, something that is loaded
> in tension to 25000 psi, followed by being loaded in compression to
> 25000 psi back and forth, will have a ratio of -1.0 ( +25000 tension/
> -25000 compression). Something loaded to 25000 psi tension that is
> reduced to 10000 psi tension and back and forth will have a stress
> ratio of .4 (10000 tension/ 25000 tension). The S-n curves show that
> the amount of cyclic load that structure loaded with a ratio of -1
> will fail far sooner than one with a ratio of .4, even though the
> maximum stress level is the same. You can look in Mil-Hnbk-5 or
> elsewhere for S-n curves to verify that.

The peak-to-peak stress difference in the first case, (ratio -1)
is 5,000psi, for the second case (.4) it is 1500 psi. So it is
no surprise that the first case fails earlier!

Now suppose two cases in which the magnitudes of
the stress cycles are equal:

In the first case the bolt is pre-loaded to 2500 psi then
subjected to an alternating load of an additional +/- 1500 psi,
(e.g. from 4000 to 1000 both in tension) while a second,
otherwise identical but not prestressed bolt is cycled
from 1500 psi in tension to 1500 psi in compression.
Both bolts see the same peak-to-peak stress difference.
The ration in the first case (preloaded bolt) is 4, in the
second case it is -1. Which bolt fails first?

> The best book to explain all this is "Mechanical Engineering
> Design" by Joseph Edward Shigley, Professor at the University of
> Michigan, chapter 8, "Design of Screws, Fasteners, and Connections".
> It is THE most widely used text on the subject in the top engineering
> schools of the country, and has been for many years.
>

Barring misprints I am confident that any engineering test used
in US engineering schools will correctly address the subject.

--

FF

[[email protected]]

On Aug 25, 7:59 pm, Fortunat1 > wrote:
> Fred the Red Shirt > wrote roups.com:
>
>
>
>
>
> > On Aug 17, 2:50 am, Charles Vincent > wrote:
> >> Fortunat1 wrote:
> >> > "Rich S." > wrote in
> >> :
>
> >> >> "Fortunat1" > wrote in message
> >> .. .
> >> >>> Well, obviously I'd protect it, but I'm not going to rely on
> >> >>> epoxy to bear a load. If I can't get the holes 100% I'll bush
> >> >>> them....
>
> >>...So I guess I'l just be as careful as I can cutting the holes. Just
> >> > looking through Bengelis' book, I see he recommends using a twist
> >> > drill to cut the holes, presumably to their final size,...
>
> >> I would test that theory first. Reamers may or may not give a good
> >> finish on wood. That was one of the reasons I quoted the study I
> >> did. The twist drill gave the best hole finish.
>
> > Bits made for wood, high quality brad-point or forstner bits,
> > may give you a cleaner hole than a twist drill made for metal.
> > Cheap bits are crap-they'll burn their way through the wood.
>
> Actauly, having tried each on some scrap pieces of spruce, the twist
> drill gave the best finished hole and the roundest hole by a long shot.
> The 5/16th bolt was a perfect fit after having used a an 8mm twist
> drill.
>
> > As a rule of thumb, when working wood, use tools made for
> > woodworking. Duh!
>
> Yes, mostly I do, but in this case, I'll use what works best! I found
> the woood bit went a bit eccentric as it went through giving a slightly
> tapered bore as it went through.
>
>
>
>
>
>
>
> > Wood expands and contracts with changes in humidity and
> > it does so anisotropically. E.g. a flat-sawn board will
> > have the highest expansion rate accross it's width, less through
> > its thickness, and minimal along it's length. Quarter sawn or
> > vertically grained wood, which is what you usually want for
> > a spar cap, will have those first two rates reversed.
>
> > What this means is that if you drill a perfectly circular hole
> > in a piece of wood, as soon as the humidity changes it
> > becomes an oval hole. The same is true of a wooden dowel.
>
> > Wood finishes slow the rate at which wood absorbs or
> > releases moisture to the air so as to prevent moisture
> > gradients through the interior of the wood, which minimizes
> > e warpage. But all wood finishes are permeable to some
> > degree to water vapor.
>
> > So don't get too crazy about making the hole perfect. I think
> > the epoxy approach is a good idea.
>
> 'Kay,. but did the bipes of the thirties have the holes filled in any
> way? Lots of them are still flying wth their original spars.
>
>
>
> - Hide quoted text -
>
> - Show quoted text -- Hide quoted text -
>
> - Show quoted text -- Hide quoted text -
>
> - Show quoted text -

It's interesting to hear of your results on hole quality. I have
also found that a good, sharp HS twist drill works great in metal or
wood. I think the place where the special wood bits like the Forstner
( a fancy hole saw) are used is in drilling large holes. For 1/2" dia
holes or so and smaller, the twist drill is the way to go. If you need
a 2" or 3" hole or so, well a twist drill that size is a huge chunk of
metal, hard to find locally and expensive to boot. Hole saws do OK in
wood ( and even metal if you are carefull) up to 6" dia or so and are
what I use for large holes.

Regards,
Bud

[Fred the Red Shirt]

On Aug 26, 2:09 am, wrote:
> On Aug 25, 7:59 pm, Fortunat1 > wrote:
>
>
>
> > Fred the Red Shirt > wrote roups.com:
>
> > > On Aug 17, 2:50 am, Charles Vincent > wrote:
> > >> Fortunat1 wrote:
> > >> > "Rich S." > wrote in
> > >> :
>
> > >> >> "Fortunat1" > wrote in message
> > >> .. .
> > >> >>> Well, obviously I'd protect it, but I'm not going to rely on
> > >> >>> epoxy to bear a load. If I can't get the holes 100% I'll bush
> > >> >>> them....
>
> > >>...So I guess I'l just be as careful as I can cutting the holes. Just
> > >> > looking through Bengelis' book, I see he recommends using a twist
> > >> > drill to cut the holes, presumably to their final size,...
>
> > >> I would test that theory first. Reamers may or may not give a good
> > >> finish on wood. That was one of the reasons I quoted the study I
> > >> did. The twist drill gave the best hole finish.
>
> > > Bits made for wood, high quality brad-point or forstner bits,
> > > may give you a cleaner hole than a twist drill made for metal.
> > > Cheap bits are crap-they'll burn their way through the wood.
>
> > Actauly, having tried each on some scrap pieces of spruce, the twist
> > drill gave the best finished hole and the roundest hole by a long shot.
> > The 5/16th bolt was a perfect fit after having used a an 8mm twist
> > drill.
>
> > > As a rule of thumb, when working wood, use tools made for
> > > woodworking. Duh!
>
> > Yes, mostly I do, but in this case, I'll use what works best! I found
> > the woood bit went a bit eccentric as it went through giving a slightly
> > tapered bore as it went through.
>
> > > Wood expands and contracts with changes in humidity and
> > > it does so anisotropically. E.g. a flat-sawn board will
> > > have the highest expansion rate accross it's width, less through
> > > its thickness, and minimal along it's length. Quarter sawn or
> > > vertically grained wood, which is what you usually want for
> > > a spar cap, will have those first two rates reversed.
>
> > > What this means is that if you drill a perfectly circular hole
> > > in a piece of wood, as soon as the humidity changes it
> > > becomes an oval hole. The same is true of a wooden dowel.
>
> > > Wood finishes slow the rate at which wood absorbs or
> > > releases moisture to the air so as to prevent moisture
> > > gradients through the interior of the wood, which minimizes
> > > e warpage. But all wood finishes are permeable to some
> > > degree to water vapor.
>
> > > So don't get too crazy about making the hole perfect. I think
> > > the epoxy approach is a good idea.
>
> > 'Kay,. but did the bipes of the thirties have the holes filled in any
> > way? Lots of them are still flying wth their original spars.
>
> > - Hide quoted text -
>
> > - Show quoted text -- Hide quoted text -
>
> > - Show quoted text -- Hide quoted text -
>
> > - Show quoted text -
>
> It's interesting to hear of your results on hole quality. I have
> also found that a good, sharp HS twist drill works great in metal or
> wood. I think the place where the special wood bits like the Forstner
> ( a fancy hole saw) are used is in drilling large holes. For 1/2" dia
> holes or so and smaller, the twist drill is the way to go. If you need
> a 2" or 3" hole or so, well a twist drill that size is a huge chunk of
> metal, hard to find locally and expensive to boot. Hole saws do OK in
> wood ( and even metal if you are carefull) up to 6" dia or so and are
> what I use for large holes.
>

I'm still surprised that a good quality brad-point would not
make a neater hole than an ordinary twist dirill. At the
very least it will make a neater hole at the entrance and
exit.

--

FF

[Gunny]

> > On Aug 24, 1:38 pm, Gunny > wrote:
> > > stress cycle amplitude. The reason some pre-tensioned bolted
> > > connections (esp. shear) have better fatigue characteristics is
> > > because the cyclic portion of the load is transfered via friction. The
> > > bolt actually experiences a drastically reduced or eliminated cyclic
> > > stress, thereby extending it's fatigue life even though the mean
> > > stress of the bolt is much higher. Tension connections see improvement
> > > through a different mechanism, but the result is the same - reduced
> > > cyclic stress in the bolt and increased fatigue life.
>
> Correct me if I am mistaken but here Matt is giving us an example
> of a bolt that is preloaded in tension and then stressed (cyclically)
> in tension.
>

Yes. Actually I touched on both situations - bolted plates that slide
past one another, and bolted plates that are pulling apart. They are
different with regard to how preload helps. I only brushed over the
different mechanism for tension connections because I anticipated the
direction the argument was going.

> That is different from a bolt that is pre-loaded in tension to fasten
> two surfaces and then subject to shear, right?
>

Yes.

>
> Matt made it clear that bolted and riveted structures typically rely
> on friction from the clamping force of the fasteners so that the
> fasteners themselves typically see very little shear. I believe that
> is correct. In particular, and Matt alluded to this problem, imagine
> the precision required to evenly distribute the transverse shear
> stress over many fasteners over a large surface, and then to
> maintain that distribution over changing loads, thermal expansion,
> etc.
>

Mmmm..details... In buildings, rivets are generally assumed to _not_
develop pretension, therefore a riveted (building) joint would not
have considered friction in its design. In practice, as the hot-driven
rivet shrank it would induce clamping in the joint. A little padding
of the safety factor sure didn't hurt. Only for certain bolted joints,
where we have good control over the important parameters and we
actually require the fixity of the joint, do we consider friction. My
only comment on rivets was to reference Chris Heintz's body of work.

> I suggest that relying on the bolts to carry the entire load
> without ANY load being carried by friction between the wing
> attachment fittings and the wood will concentrate the stress
> at the locations of the fasteners. This may well locally stress
> the wood to failure, e.g. it may split. The clamping force of
> the fitting distributes that load over a larger area reducing the
> stress concentrations.

Well, this isn't anything that I disagree with Bud about. It is
definitely more conservative to assume that friction doesn't help you
out. I can certainly believe that aero designers don't normally factor
it in. It just doesn't make sense to me for a wood propeller due to
the body of research I've read, and the materials and magnitudes of
stresses involved.

> I am far from clear on what constitutes 'proper' for
> a metal piece bolted to wood. If the wood is clamped
> too tightly, an increase is humidity may overstress it
> causing it to split. If too loose, a decrease in humidity
> may cause the joint to loosen too much.

Marc Zeitlin and Paul Lipps have posted some of their results in
Contact and on the web for using Belleville washers to combat that
problem as it applies to wood propellers. It's a great read.

[Charles Vincent]

wrote:
>>> As a rule of thumb, when working wood, use tools made for
>>> woodworking. Duh!
>> Yes, mostly I do, but in this case, I'll use what works best! I found
>> the woood bit went a bit eccentric as it went through giving a slightly
>> tapered bore as it went through.
>>

>
> It's interesting to hear of your results on hole quality. I have
> also found that a good, sharp HS twist drill works great in metal or
> wood. I think the place where the special wood bits like the Forstner
> ( a fancy hole saw) are used is in drilling large holes. For 1/2" dia
> holes or so and smaller, the twist drill is the way to go. If you need
> a 2" or 3" hole or so, well a twist drill that size is a huge chunk of
> metal, hard to find locally and expensive to boot. Hole saws do OK in
> wood ( and even metal if you are carefull) up to 6" dia or so and are
> what I use for large holes.
>
> Regards,
> Bud
>

People will always believe what they want to, but our government
actually spent a lot of time and money finding the answer to this one.
The whole reason the study I mentioned earlier was done was because they
found significant variations in their testing of bolted connections in
wood for aircraft. They found the proportional limit for a poorly
drilled hole may be as low as one-third of the allowable limit load from
the old ANC design manuals. In the joint study done by FPL and ANC for
aircraft structures, they compared the Forstner, Twist drill and machine
bit(what they are calling a machine bit looks to be what we would now
call a brad point with a center spur). The twist drill made a better
hole. From the report:

"In drilling the experimental holes to establish drilling technique,
the 120° (probably actually 118 0 ) twist drill appeared to produce the
smoothest hole. The 60° twist drill was about equally effective, but
offered no apparent advantages over the more common 120° drill. A hole
drilled with a machine bit with a slow spiral did not appear to differ
materially from one drilled with a machine bit with a fast spiral, or
from one drilled with a Foerstner bit."

and

"The machine bit and the Forstner bit had a tendency to produce
large chips which sometimes wedged underneath the horizontal cutting
edge. Some of the chips were complete washers in form, the full diameter
of the drill in size, up to 1/32 inch thick, and strong enough to remain
intact when the bit was withdrawn. In a few cases a chip became wedged
between the side of the bit and the wall of the hole and scored the wall."

Charles

[Gunny]

On Aug 25, 8:35 pm, Fred the Red Shirt >
wrote:
> > As to the statement that I clearly don't understand the factors
> > involved, you clearly do not understand what I said, the nature of
> > preloaded bolts, or even the S-n curves themselves. Improved fatigue
> > life due to preloading has nothing to do with friction. Friction may
> > improve fatigue life in the real world by spreading load over a larger
> > area, but the benefit of preloading on fatigue life is due primarily
> > to an effect that exists even if no friction is present at all.
>
> Could you please elaborate on the theory of that effect?
> E.g. is this a result of the superposition of stresses?
>

....and...

> > If we now begin to subject both bolts to the same cyclic
> > loading of 1500 lbs, where the applied load is increased from 0 up to
> > 1500 and then reduced to zero again, the bolt with the 2000 lb preload
> > will see a cyclic load of only about 150 lbs, whereas the un-preloaded
> > bolt will see a cyclic load of 1500 lbs, and will obviously fail much
> > sooner.
>
> Here you temporarily lost me because you have not told us
> HOW the bolt is loaded. If the load consists of additional
> tension, then plainly the bolt will see cyclical stress over the
> range of 3500 lb to 2000. That is clearly the type of loading Matt
> was discussing. If I make the unremarkable assumption that y
> ou are familiar with addition then clearly you are NOT assuming
> that the load is applied in the form of additional tension.

When a joint is pre-loaded, two important things happen. The bolt
stretches. AND The plates or whatever are being fastened are
compressed. When you add load that induces additional axial tensile
stress in the bolt, you have to consider that the compression in the
plates is being relaxed at the same time. So the stress increase is
not a 1:1 correlation to the additional applied load. The slope will
actually be something less than 1:1 until the point where all the
compression has been removed, after which it will be 1:1. As you can
imagine, the actual slope to the left of the knee is a function of the
modulus of elasticity of the bolts, the MoE of the plates, and the
effective area being compressed (where thickness comes into play).

> However, the clamping force will still cause the shear to be
> distributed over the surface area being clamped and not just
> through the bolts. The superposition of stresses is not
> the total story.

That is a completely separate effect and loading situation than what
Bud is talking about. My understanding has always been that what Bud
is talking about is only effective for additional tensile loading of
the fastener. But I agree with you, the clamping can be very important
for shear of the bolt, even if we ignore that effect in practice.

> > As for S-n curves, there are more than one type. The one
> > relating to what I am talking about are the ones that show S vs N for
> > different stress ratios. The stress ratio is the fraction equivalent
> > of the maximum to minimum load. For example, something that is loaded
> > in tension to 25000 psi, followed by being loaded in compression to
> > 25000 psi back and forth, will have a ratio of -1.0 ( +25000 tension/
> > -25000 compression). Something loaded to 25000 psi tension that is
> > reduced to 10000 psi tension and back and forth will have a stress
> > ratio of .4 (10000 tension/ 25000 tension). The S-n curves show that
> > the amount of cyclic load that structure loaded with a ratio of -1
> > will fail far sooner than one with a ratio of .4, even though the
> > maximum stress level is the same. You can look in Mil-Hnbk-5 or
> > elsewhere for S-n curves to verify that.
>
> The peak-to-peak stress difference in the first case, (ratio -1)
> is 5,000psi, for the second case (.4) it is 1500 psi. So it is
> no surprise that the first case fails earlier!
>
> Now suppose two cases in which the magnitudes of
> the stress cycles are equal:

Yes, that is exactly what I'm talking about.

> In the first case the bolt is pre-loaded to 2500 psi then
> subjected to an alternating load of an additional +/- 1500 psi,
> (e.g. from 4000 to 1000 both in tension) while a second,
> otherwise identical but not prestressed bolt is cycled
> from 1500 psi in tension to 1500 psi in compression.
> Both bolts see the same peak-to-peak stress difference.
> The ration in the first case (preloaded bolt) is 4, in the
> second case it is -1. Which bolt fails first?

Actually case 1 R=0.25, but otherwise your example illustrates my
point pretty well.

Cheers,
Matt

[Fortunat1[_20_]]

Fred the Red Shirt > wrote in
oups.com:

> On Aug 26, 2:09 am, wrote:
>> On Aug 25, 7:59 pm, Fortunat1 > wrote:
>>
>>
>>
>> > Fred the Red Shirt > wrote
>> > roups.com:
>>
>> > > On Aug 17, 2:50 am, Charles Vincent > wrote:
>> > >> Fortunat1 wrote:
>> > >> > "Rich S." > wrote in
>> > >> :
>>
>> > >> >> "Fortunat1" > wrote in message
>> > >> .. .
>> > >> >>> Well, obviously I'd protect it, but I'm not going to rely on
>> > >> >>> epoxy to bear a load. If I can't get the holes 100% I'll
>> > >> >>> bush them....
>>
>> > >>...So I guess I'l just be as careful as I can cutting the holes.
>> > >>Just
>> > >> > looking through Bengelis' book, I see he recommends using a
>> > >> > twist drill to cut the holes, presumably to their final
>> > >> > size,...
>>
>> > >> I would test that theory first. Reamers may or may not give a
>> > >> good finish on wood. That was one of the reasons I quoted the
>> > >> study I did. The twist drill gave the best hole finish.
>>
>> > > Bits made for wood, high quality brad-point or forstner bits,
>> > > may give you a cleaner hole than a twist drill made for metal.
>> > > Cheap bits are crap-they'll burn their way through the wood.
>>
>> > Actauly, having tried each on some scrap pieces of spruce, the
>> > twist drill gave the best finished hole and the roundest hole by a
>> > long shot. The 5/16th bolt was a perfect fit after having used a an
>> > 8mm twist drill.
>>
>> > > As a rule of thumb, when working wood, use tools made for
>> > > woodworking. Duh!
>>
>> > Yes, mostly I do, but in this case, I'll use what works best! I
>> > found the woood bit went a bit eccentric as it went through giving
>> > a slightly tapered bore as it went through.
>>
>> > > Wood expands and contracts with changes in humidity and
>> > > it does so anisotropically. E.g. a flat-sawn board will
>> > > have the highest expansion rate accross it's width, less through
>> > > its thickness, and minimal along it's length. Quarter sawn or
>> > > vertically grained wood, which is what you usually want for
>> > > a spar cap, will have those first two rates reversed.
>>
>> > > What this means is that if you drill a perfectly circular hole
>> > > in a piece of wood, as soon as the humidity changes it
>> > > becomes an oval hole. The same is true of a wooden dowel.
>>
>> > > Wood finishes slow the rate at which wood absorbs or
>> > > releases moisture to the air so as to prevent moisture
>> > > gradients through the interior of the wood, which minimizes
>> > > e warpage. But all wood finishes are permeable to some
>> > > degree to water vapor.
>>
>> > > So don't get too crazy about making the hole perfect. I think
>> > > the epoxy approach is a good idea.
>>
>> > 'Kay,. but did the bipes of the thirties have the holes filled in
>> > any way? Lots of them are still flying wth their original spars.
>>
>> > - Hide quoted text -
>>
>> > - Show quoted text -- Hide quoted text -
>>
>> > - Show quoted text -- Hide quoted text -
>>
>> > - Show quoted text -
>>
>> It's interesting to hear of your results on hole quality. I have
>> also found that a good, sharp HS twist drill works great in metal or
>> wood. I think the place where the special wood bits like the Forstner
>> ( a fancy hole saw) are used is in drilling large holes. For 1/2" dia
>> holes or so and smaller, the twist drill is the way to go. If you
>> need a 2" or 3" hole or so, well a twist drill that size is a huge
>> chunk of metal, hard to find locally and expensive to boot. Hole saws
>> do OK in wood ( and even metal if you are carefull) up to 6" dia or
>> so and are what I use for large holes.
>>
>
> I'm still surprised that a good quality brad-point would not
> make a neater hole than an ordinary twist dirill. At the
> very least it will make a neater hole at the entrance and
> exit.

It didn't and the brad point is a very good quality bit. One of the
books I have somewhere recommends a twist bit for the wood. Might be the
Bengelis book but IIRC it says to use as sharp a bit as possible and to
feed it at a reate that makes smal shavings, which is what I id and it
worked a treat. I did some practice pieces using some scrap steel parts.
I located the first hole as accurately as I could, then drilled the rest
using the steel part as a guide. I started each cut by hand just turning
the chuck until it was in a bit and then turned the power on. The
resulting hole was about as good as it gets with zero tearaway. The bolt
fit perfectly with the fit just enough friction to hold the bolt in by
itself.

[RST Engineering]

Have you taken the Snipping 101 class yet?

Jim

--
"If you think you can, or think you can't, you're right."
--Henry Ford


"Fortunat1" > wrote in message
.. .


> It didn't and the brad point is a very good quality bit. One of the
> books I have somewhere recommends a twist bit for the wood.

[Fred the Red Shirt]

On Aug 26, 1:35 am, Fred the Red Shirt >
wrote:
> ...
>
>
> Using bushings in a hole drilled in wood helps to reduce
> that elongation by spreading that bearing stress over
> a larger area in the wood, and is a lighter approach than
> simply using a larger bolt. But it is still not a substitute
> for maintaining the proper tension in the bolts.
>

I hasten to correct this. It is right if the bushing is merely
pressed into the hole. If the bushing is well-bonded to the
wood then it will distribute the stress better.

--

FF

[Fred the Red Shirt]

On Aug 26, 11:22 am, Fortunat1 > wrote:
>
> ...
> I did some practice pieces using some scrap steel parts.
> I located the first hole as accurately as I could, then drilled the rest
> using the steel part as a guide. I started each cut by hand just turning
> the chuck until it was in a bit and then turned the power on. The
> resulting hole was about as good as it gets with zero tearaway. The bolt
> fit perfectly with the fit just enough friction to hold the bolt in by
> itself.

It sounds like your workmanship illustrates the difference between
a builder and a craftsman.

--

FF

[Fortunat1]

"RST Engineering" > wrote in news:13d39pmtl6ru7c7
@news.supernews.com:

> Have you taken the Snipping 101 class yet?
>
> Jim
>

No, and I have no intention of doing so so you can stop wasting bandwidth
netkkkopping

[Fortunat1]

Fred the Red Shirt > wrote in
ups.com:

> On Aug 26, 11:22 am, Fortunat1 > wrote:
>>
>> ...
>> I did some practice pieces using some scrap steel parts.
>> I located the first hole as accurately as I could, then drilled the rest
>> using the steel part as a guide. I started each cut by hand just turning
>> the chuck until it was in a bit and then turned the power on. The
>> resulting hole was about as good as it gets with zero tearaway. The bolt
>> fit perfectly with the fit just enough friction to hold the bolt in by
>> itself.
>
> It sounds like your workmanship illustrates the difference between
> a builder and a craftsman.

Thanks, but I'm afraid my results aren't reflecting that!
I suppose my interest in making the airplane as straight and safe as
possible is more related to my uncertainty about what's safe to let slide
than any desire to make a Grand Champion. I simply don't know enough about
the things to say "yeah, that's good enough"
Having said that, I do enjoy the thrill of holding a nicely made piece in
my hands. Hopefully more of them will be like that than not when I'm done!

[Matt Whiting]

Fortunat1 wrote:
> "RST Engineering" > wrote in news:13d39pmtl6ru7c7
> @news.supernews.com:
>
>> Have you taken the Snipping 101 class yet?
>>
>> Jim
>>
>
> No, and I have no intention of doing so so you can stop wasting bandwidth
> netkkkopping

Ah, failed the class...

Matt

[Fortunat1]

Matt Whiting > wrote in
:

> Fortunat1 wrote:
>> "RST Engineering" > wrote in
>> news:13d39pmtl6ru7c7 @news.supernews.com:
>>
>>> Have you taken the Snipping 101 class yet?
>>>
>>> Jim
>>>
>>
>> No, and I have no intention of doing so so you can stop wasting
>> bandwidth netkkkopping
>
> Ah, failed the class...
>
> Matt
>

Nice try..

[[email protected]]

On Aug 26, 1:42 pm, Fred the Red Shirt >
wrote:
> On Aug 26, 1:35 am, Fred the Red Shirt >
> wrote:
>
> > ...
>
> > Using bushings in a hole drilled in wood helps to reduce
> > that elongation by spreading that bearing stress over
> > a larger area in the wood, and is a lighter approach than
> > simply using a larger bolt. But it is still not a substitute
> > for maintaining the proper tension in the bolts.
>
> I hasten to correct this. It is right if the bushing is merely
> pressed into the hole. If the bushing is well-bonded to the
> wood then it will distribute the stress better.
>
> --
>
> FF

Excellent question! The plane I built called for 2024-T4 aluminum
bushings to be epoxied in the cap. As I pointed out, using this
approach not only has a larger bearing area against the wood, which is
the weakest material in the load path, but it actually restores much
if not all of the strength that was lost when the hole was drilled in
the spar cap. If you have gone to the trouble of using bushings,
epoxying them in place is fairly simple and cheap as hell. Adds very
little work.

Regards,
Bud

[Fortunat1[_2_]]

Charles Vincent > wrote in
t:


>
> "In drilling the experimental holes to establish drilling technique,
> the 120° (probably actually 118 0 ) twist drill appeared to produce
> the smoothest hole. The 60° twist drill was about equally effective,
> but offered no apparent advantages over the more common 120° drill. A
> hole drilled with a machine bit with a slow spiral did not appear to
> differ materially from one drilled with a machine bit with a fast
> spiral, or from one drilled with a Foerstner bit."
>
> and
>
> "The machine bit and the Forstner bit had a tendency to produce
> large chips which sometimes wedged underneath the horizontal cutting
> edge. Some of the chips were complete washers in form, the full
> diameter of the drill in size, up to 1/32 inch thick, and strong
> enough to remain intact when the bit was withdrawn. In a few cases a
> chip became wedged between the side of the bit and the wall of the
> hole and scored the wall."
>

Thanks, this is exactly what I discovered. It's good to know I'm going
down the correct path.


Couple of things I'm still uncertain of, though. The steel parts have
quite a tight fit on the bolts. Obviously any paint on the inside of
these holes is simply going to be forced out when I push a bolt through.
this is normal?
Also, there's a small ridge formed on the edge of each hole. I figure
it's OK to leave the excess material there for a couple of reasons, one,
it provides more material for the bolt to rest against, and two it
won'ts interfere with tightening the bolts down since there will only be
a washer up against the hole anyway.
If it is poor practice to leave the ridge on the edge, what's the best
method for getting rid of it? Aside from a special machien, I thought of
carefully cutting it down with a large dril bit, but I'd be afraid of
doing some damage to the part.
Any suggestions?

[Fred the Red Shirt]

On Aug 28, 1:30 pm, Fortunat1 > wrote:
> Charles Vincent > wrote . net:
>
>
> ...
>
>
> Couple of things I'm still uncertain of, though. The steel parts have
> quite a tight fit on the bolts. Obviously any paint on the inside of
> these holes is simply going to be forced out when I push a bolt through.
> this is normal?

Others may have a better answer, like they did about the drill bits,
but I would mask off the inside of the holes so as to not get paint
on them and use never seize on the bolt shaft. A little dab will do
ya.

There are some places where never seize should not be used. A
fellow I know used it on his spark plugs on his Stinson. Normally
that's OK (I think) but his heads had been rethreaded with helicoils
and the helicoils backed out when the engine was running.

> Also, there's a small ridge formed on the edge of each hole.

I think that's called a burr--sometimes called a wire-edge.
It is metal that has been cold-rolled around the corner
on the edge during drilling. Usually it is much bigger on the
exit side than on the entrance side. If drilling down a pilot hole,
that effect can be minimized by drilling part-way through from
each sides. Without a pilot hole alignment is too difficult.


> I figure
> it's OK to leave the excess material there for a couple of reasons, one,
> it provides more material for the bolt to rest against, and two it
> won'ts interfere with tightening the bolts down since there will only be
> a washer up against the hole anyway.

I don't follow you here. Doesn't the burr stick up above the flat
surface?
Won't that interfere with proper seating of the washer?

> If it is poor practice to leave the ridge on the edge, what's the best
> method for getting rid of it? Aside from a special machien, I thought of
> carefully cutting it down with a large dril bit, but I'd be afraid of
> doing some damage to the part.
> Any suggestions?

Draw filing is a technique wherein the file is held with both hands,
one
on the handle and one on the tip and drawn across a flat surface as
if slicing with a drawknife, to remove high spots. I've never gotten
the hang of it myself. The parts could also be lapped on wet/dry
sandpaper on a very flat surface like a one-foot square marble
tile, or a good quality table-saw or jointer table. Of you could
use a fine rat-tail, cylindrical or half-round file, through the
hole.
A hand grinder,even a dremel, used very carefully would do the
trick too. A conical stone would do a nice job.

Using a very large countersink bit would do it too, a very large
drill bit would do the same but is more likely to grab and tear.

I don't think that slightly chamfering the holes would hurt at
all. The sharp edge or wire is a stress riser that is relieved by
chamfering, though in this case I don't think it is a serious
issue.

If you practice on scrap, you won't have to practice on your
project!

--

FF

[Charles Vincent]

Fortunat1 wrote:

> Thanks, this is exactly what I discovered. It's good to know I'm going
> down the correct path.

You are drilling the cleanest hole, but still may not be going down the
right path. The report I quoted was written before the invention of
modern epoxies. I think that coating oversize holes in the wood with
epoxy will give you a stronger structure by further reducing the bearing
stress on the wood, but that is just my opinion.


> Also, there's a small ridge formed on the edge of each hole. I figure
> it's OK to leave the excess material there for a couple of reasons, one,
> it provides more material for the bolt to rest against, and two it
> won'ts interfere with tightening the bolts down since there will only be
> a washer up against the hole anyway.

Assuming it is not just an ordinary burr, it sounds like one of the
following things is happening:

A)Your drill bit is dull, particularly on the edges of the flutes and
you are applying too much pressure to the drill to make it cut, causing
the hole to pucker.
B)The reamer you are using is dull, or the drilled hole is too small for
that reamer and the reamer is cold working the hole rather than cutting.
In my experience, this will create the pucker you are describing.
The cold worked hole will also close up slightly when the reamer is
removed, creating the tight fit you are describing.

> If it is poor practice to leave the ridge on the edge, what's the best
> method for getting rid of it? Aside from a special machien, I thought of
> carefully cutting it down with a large dril bit, but I'd be afraid of
> doing some damage to the part.
> Any suggestions?

I personally would not be comfortable leaving the ridge, particularly
since I do not know what it looks like. If it is an ordinary burr, I
would use a deburring tool.

Charles

[Fortunat1[_2_]]

Charles Vincent > wrote in
:

> Fortunat1 wrote:
>
>> Thanks, this is exactly what I discovered. It's good to know I'm
>> going down the correct path.
>
> You are drilling the cleanest hole, but still may not be going down
> the right path. The report I quoted was written before the invention
> of modern epoxies. I think that coating oversize holes in the wood
> with epoxy will give you a stronger structure by further reducing the
> bearing stress on the wood, but that is just my opinion.
>


You're probably right, but the way I see it is that airplanes just like
this have been flying wth their original spars since the flood, so if it
was ood enough for them it's god enough for me. Also, this is a plank
spar, not a capped spar, so there iis plenty of meat there. I'll
certainly keep the epoxy thing in mind in case I screw up some of the
holes when drilling them out for fittings, though. Nice to know there is
a fix for any mistakes.

Yes, pucker is a better word for it. the drills are nice and sharp and
I'm getting a good cut there. I've been cutting them out to 7.7 mm and
then reaming to 5/16th. You're right, some of the holes are cut pretty
clean, but the reamer soon produces the rounded pucker as you so aptl
put it.
>
>> If it is poor practice to leave the ridge on the edge, what's the
>> best method for getting rid of it? Aside from a special machien, I
>> thought of carefully cutting it down with a large dril bit, but I'd
>> be afraid of doing some damage to the part.
>> Any suggestions?
>
> I personally would not be comfortable leaving the ridge, particularly
> since I do not know what it looks like. If it is an ordinary burr, I
> would use a deburring tool.
>

OK, it's not a burr, it's more the pucker you describe. does this mean
the part is trash, or can I leave it or should i try a deburring tool on
it? The reamers are new and seem nice and sharp, I am getting swarf, but
not as much maybe as you would expect..

[Charles Vincent]

Fortunat1 wrote:

> Yes, pucker is a better word for it. the drills are nice and sharp and
> I'm getting a good cut there. I've been cutting them out to 7.7 mm and
> then reaming to 5/16th. You're right, some of the holes are cut pretty
> clean, but the reamer soon produces the rounded pucker as you so aptl
> put it.

You are using the reamer to cut .009 inches of material. Generally, I
don't try to do more than .002 to .003. As far as correcting the parts,
you need guidance from someone else. With the metal cold worked like
that, I personally would look closely(with a magnifying glass or an
industrial microscope since I have one) at the edges to see if there are
any tiny cracks. I expect there are.

Charles

[Fortunat1]

Charles Vincent > wrote in news:yX0Bi.47964$Um6.15150
@newssvr12.news.prodigy.net:

> Fortunat1 wrote:
>
>> Yes, pucker is a better word for it. the drills are nice and sharp and
>> I'm getting a good cut there. I've been cutting them out to 7.7 mm and
>> then reaming to 5/16th. You're right, some of the holes are cut pretty
>> clean, but the reamer soon produces the rounded pucker as you so aptl
>> put it.
>
> You are using the reamer to cut .009 inches of material. Generally, I
> don't try to do more than .002 to .003. As far as correcting the parts,
> you need guidance from someone else. With the metal cold worked like
> that, I personally would look closely(with a magnifying glass or an
> industrial microscope since I have one) at the edges to see if there are
> any tiny cracks. I expect there are.

Oh dear, which means I've just wrecked a whole lot of parts. I'll have a
looksee with a magnifying glass. I did try to cut them out to 7.9 mm, but I
was afraid it might be too deep a cut and that the triangular hole cut by
the drill might leave it's remains around the edges.

[Charles Vincent]

Fortunat1 wrote:

>
> Oh dear, which means I've just wrecked a whole lot of parts. I'll have a
> looksee with a magnifying glass. I did try to cut them out to 7.9 mm, but I
> was afraid it might be too deep a cut and that the triangular hole cut by
> the drill might leave it's remains around the edges.

Don't make any assumptions based on my comments. I am unfamiliar with
the plane you are building, I do not know the metal variety you are
working with and have not seen the parts. Finally, I do not have
experience building enough airplanes to rely on experience when
answering you. Metalworking I do know about, so I could make a pretty
good guess as to what your problem was and the probable ramifications. I
suggest you talk to the designer of your airplane or another builder of
it.

Charles

[Fortunat1]

Charles Vincent > wrote in
:

> Fortunat1 wrote:
>
>>
>> Oh dear, which means I've just wrecked a whole lot of parts. I'll
>> have a looksee with a magnifying glass. I did try to cut them out to
>> 7.9 mm, but I was afraid it might be too deep a cut and that the
>> triangular hole cut by the drill might leave it's remains around the
>> edges.
>
> Don't make any assumptions based on my comments. I am unfamiliar with
> the plane you are building, I do not know the metal variety you are
> working with and have not seen the parts. Finally, I do not have
> experience building enough airplanes to rely on experience when
> answering you. Metalworking I do know about, so I could make a
> pretty good guess as to what your problem was and the probable
> ramifications. I suggest you talk to the designer of your airplane or
> another builder of it.
>

Well, both the guys who had a hand designing this thing are dead, so
that's going to be a bit difficult! (Neither in a Hatz, BTW)
The material is 4130 steel which is a relativley high carbon steel if
you're not familiar with it.
Seems to me you've hit the problem on the head first time out. Your
experience is obvious!

I had a look with a not too powerful magnifying glass and couldn't see
any obvious cracks. There's the occasional scratch in the holes in the
direction of the cut, presumably from a bit of swarf getting caught in
the reamer. The ridge around the edges mostly stand up about .002 or so,
and maybe a little less than that in thickness. They're more regular in
appearance and much thicker than you'd see from drilling, for instance,
but they're still not so perfect around their edge you could tell a
crack from just an irregularity.At least I couldn't.
I do have someone who can look at them here, though, so that's what I'll
have to do to be sure.
Thanks for the heads up on that! They say you make two airplanes when
you make your first one, the one you fly and the one you throw away..
;(

[Fortunat1[_21_]]

Fred the Red Shirt > wrote in
oups.com:

> On Aug 12, 11:09 am, Fortunat1 > wrote:
>> ...
>> I'll just have to get a good
>> quality reamer and prepare each hole carefully. I'll see if I can get
a
>> drill bit that brings he holes a little closer to the final size.
>
> May I suggest you get more than one drill bit, for the same
> reason you need more than one reamer?
>
> .What is the annealing temperature for 4130? You can drill through
> a bandsaw blade by spot annealing it, that is you chuck a blunt rod
> like a nail with the point ground off into a drill press bring that to
> bear
> on the spot to be drilled until it gets good and hot, then let it
> cool
> slowly. Now the spot is annealed and a hole can be drilled with
> an ordinary bit.
>
> So I wonder if re-drilling the holes will heat them to the annealing
> temperature? Or would it be feasible to spin a rod in the holes
> to heat them by friction to soften them? Or would that just
> work-harden the surface....

Don't know the answer to any of these questions, but since any sort of
heat treating, whether it be normalising or tempering, is well beyond
what I'm able to do in the shop just by eyeballing the color of the
steel.

One thing I don't underdstand is that I work hardened a small part by
getting a little over enthusiastic with a drill bit. I tried heating the
same part up to red hot and then let it cool slowly thinking it would
bring it back to the normalised state, but it seemed just as hard to
drill as it was before I cherried it.

[Fortunat1[_22_]]

Charles Vincent > wrote in news:yX0Bi.47964$Um6.15150
@newssvr12.news.prodigy.net:

> Fortunat1 wrote:
>
>> Yes, pucker is a better word for it. the drills are nice and sharp and
>> I'm getting a good cut there. I've been cutting them out to 7.7 mm and
>> then reaming to 5/16th. You're right, some of the holes are cut pretty
>> clean, but the reamer soon produces the rounded pucker as you so aptl
>> put it.
>
> You are using the reamer to cut .009 inches of material. Generally, I
> don't try to do more than .002 to .003. As far as correcting the parts,
> you need guidance from someone else. With the metal cold worked like
> that, I personally would look closely(with a magnifying glass or an
> industrial microscope since I have one) at the edges to see if there are
> any tiny cracks. I expect there are.

OK, looked at the holes using s 10X microscope and they're not exactly
mirror finished, but they don't look too bad for the most part. I didn't
find any cracks, but I did find some microscopic chatter marks, scrapes and
chips along the edges. Also found a couple of gouges that ran across the
holes from edge to edge that could best be described as a "step".
None of these imperfections were deeper than say, .002, if even that deep.
I do have my "guy" comong over to have a look, but from my description on
the phone he thinks they're probably OK.
It's all learning, eh?