What size hole saw do I use?

[[email protected]]

I need to cut a panel to mount one 3.125" and one 2.25" What size hole
saws do I use? Do I use smaller sizes, say 2.125" for 2.25" and 3" for
3.125"? Thanks.

[Orval Fairbairn]

In article . com>,
" > wrote:

> I need to cut a panel to mount one 3.125" and one 2.25" What size hole
> saws do I use? Do I use smaller sizes, say 2.125" for 2.25" and 3" for
> 3.125"? Thanks.


I use a fly cutter sized to each hole size and then finish off the holes
with a "slapper wheel" sanding wheel. I have tried the hole punches and
hole saws, but prefer the fly cutter, in a drill press set to the lowest
speed. That way, I have the best control over the hole-making process.

--
Remove _'s from email address to talk to me.

[W P Dixon]

Hey,
Your best bet is to use one of the adjustable hole cutters, I have never
seen a hole saw that actually cut the diameter that was written on the side.
I guess the wobble factor , etc. If you use a 2 1/4" hole saw you may well
end up with a 2 1/2 " hole depending on thickness of material.

Patrick
student SPL
aircraft structural mech


> wrote in message
oups.com...
>I need to cut a panel to mount one 3.125" and one 2.25" What size hole
> saws do I use? Do I use smaller sizes, say 2.125" for 2.25" and 3" for
> 3.125"? Thanks.
>

[Bob Kuykendall]

Earlier, wrote:

> I need to cut a panel to mount one 3.125" and one 2.25" What size hole
> saws do I use? Do I use smaller sizes, say 2.125" for 2.25" and 3" for
> 3.125"? Thanks.

YMMV, but I've had good luck making 3-1/8" instrument holes with a
3-1/8" hole saw, likewise with the 2-1/4" saw. The hard part is finding
them in those sizes; you might have to order-in from www.mcmaster.com
or some such. The holes did tend to come out .020" or so oversize, but
the instruments I was mounting tended to be on the large size anyways.
If it's for something important, try it on scrap aluminum of the
correct thickness first.

These days I use a single-point suicide cutter as others mention.

Thanks, and best regards to all

Bob K.
http://www.hpaircraft.com

[Morgans]

"Bob Kuykendall" > wrote >
> These days I use a single-point suicide cutter as others mention.
>
> Thanks, and best regards to all

I haven't seen anyone mention the importance of being safe, with a fly
cutter.

If you have never used one, on something like a panel, clamp it down to the
drill press table, like you never have clamped anything before. Then double
the clamps.
--
Jim in NC

[Bill Daniels]

> wrote in message
oups.com...
> I need to cut a panel to mount one 3.125" and one 2.25" What size hole
> saws do I use? Do I use smaller sizes, say 2.125" for 2.25" and 3" for
> 3.125"? Thanks.
>

I have done this several ways. Hole saws - messy, fly cutters - dangerous
if not clamped VERY well and still messy, and milling machines - neat but
hard to get access.

The best way is to get the whole panel laser cut and then anodized black
after test fitting the instruments. Not all instruments are exactly 2.250
or 3.125 so specify the holes a few thou oversize. I did it this way for my
new glider panel. The results were very neat and not expensive at all.

If you really want to cut the metal yourself, make a tool/fixture out of
high density composite particle board - I think it's called MDX or something
like that. Forstner bits cut very neat 2.250 and 3.125 holes in the MDX
tooling. Mount the panel blank to the tool and rout the panel with tungsten
router bits with ball bearing guides. Cut undersize instrument holes in the
panel with a hole saw or fly cutter and finish with the router. Make or buy
a drill guide for the instrument screw holes.

BTW, I've never had countersunk instrument screw holes all come out
perfectly. At least a couple were slightly out of alignment putting stress
on the instrument cases. The last time around I used black button head
Allen screws in oversize holes which look as nice as the countersunk variety
and allowed for some misalignment.

Bill Daniels

Do a neat job - after all, you are going to be looking at the thing for a
long time.

Bill Daniels

[John T]

Using a laser cutter changes the temper of the aluminum along the edges
of the cut. Perhaps not a big deal in a instrument panel, if it isn't
structural, but it is on a wing rib or other structural part.

A waterjet cutter can do the same thing, but you don't have to worry
about the temper. It will leave a slight burr, but nothing that can't be
dealed with simply.

John

[RST Engineering]

I prefer not to anodize anything on the airplane. Anodizing forms a VERY
hard insulating film that you have to spot-face down to the aluminum to make
an electrical connection. I prefer to powder coat, which is nearly as tough
under operating conditions but not nearly as difficult to get an electrical
connection.

Jim


> The best way is to get the whole panel laser cut and then anodized black
> after test fitting the instruments.

[LCT Paintball]

> The best way is to get the whole panel laser cut and then anodized black


Most laser machines don't like aluminum. It's too shinny, and can reflect
back into the lens. Look into water jet instead.

[GeorgeB]

On Mon, 11 Jul 2005 08:55:14 -0700, "RST Engineering"
> wrote:

>I prefer not to anodize anything on the airplane. Anodizing forms a VERY
>hard insulating film that you have to spot-face down to the aluminum to make
>an electrical connection. I prefer to powder coat, which is nearly as tough
>under operating conditions but not nearly as difficult to get an electrical
>connection.
>
>Jim

Another point against anodizing is that it increases the notch
sensitivity of already notch sensitive aluminum. This is far more
significant with hard anodizing than with decorative, but that
aluminum oxide will crack then concentrate the stress in the crack.

Powder coat has its problems too, and they are aluminum grade, product
and process dependent. All the processes I know actually "melt" a
powder on the surface. The temperatures of some powder processes are
above safe operating (change of properties) temperatures of some heat
treated aluminum alloys. I use "some" because I don't know details.

>> The best way is to get the whole panel laser cut and then anodized black
>> after test fitting the instruments.

George

[Roger]

On Mon, 11 Jul 2005 02:11:41 GMT, Orval Fairbairn
> wrote:

>In article . com>,
> " > wrote:
>
>> I need to cut a panel to mount one 3.125" and one 2.25" What size hole
>> saws do I use? Do I use smaller sizes, say 2.125" for 2.25" and 3" for
>> 3.125"? Thanks.
>
>
>I use a fly cutter sized to each hole size and then finish off the holes
>with a "slapper wheel" sanding wheel. I have tried the hole punches and
>hole saws, but prefer the fly cutter, in a drill press set to the lowest
>speed. That way, I have the best control over the hole-making process.

Your drill press must run much slower than mine<:-)) Even at the
slowest speed mine is far too fast for a fly-cutter of larger hole
saws. I prefer to use the fly-cutter chucked up in a good quality
floor mill.

A fly-cutter, at least in my experience will give the best finish to
the holes of just about any method including knock-out punches which
tend to roll the edges slightly. It's also easier to get all the
holes right where you want them which can sometimes be difficult with
the larger knockout punches. OTOH it takes a bit more skill to
sharpen the bit and to set up a fly cutter, but you can get a hole
that only requires breaking the edges to finish them up.

Hole saws tend to give a rather ragged edge and want to creep although
that can be minimized. A really sharp hole saw will do a pretty good
job but you have to be careful about it grabbing.

As for the size of a hole saw to use I go with one just as close to
the proper size I can get, while still staying under sized. I then
finish out the hole using a sanding drum. The larger ones take less
skill (and work) to keep the hole edges circular.

No matter which method is used, clamping the piece down with the
proper clamps and wood blocks (to protect the metal) is very important
from both the finished result and safety.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

[Roger]

On Mon, 11 Jul 2005 08:34:50 -0500, John T
> wrote:

>Using a laser cutter changes the temper of the aluminum along the edges
>of the cut. Perhaps not a big deal in a instrument panel, if it isn't
>structural, but it is on a wing rib or other structural part.
>
>A waterjet cutter can do the same thing, but you don't have to worry
>about the temper. It will leave a slight burr, but nothing that can't be
>dealed with simply.

A plasma torch properly set up can cut a hole in thin metal without
scorching the adjacent paint, but it takes a good set up and lots of
practice. They are fast. this would not be my choice for a first
timer.

I've cut sheets of white painted "barn metal" with a smaller self
contained unit. After being used to a torch (not on barn metal), it
took a bit of practice to get used to the speed (moving fast enough)
to do a good job. If the paint started to feather, or discolor along
the edge of the cut I knew I was moving too slow.

On a panel you'd want to build a fixture to move the tip in a circle,
or use a wood template. Wood works just fine as the plasma will, or
should be at least a quarter to half inch away from it.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com
>
>John

[Bill Daniels]

"LCT Paintball" > wrote in message
news:7ExAe.145539$x96.83501@attbi_s72...
> > The best way is to get the whole panel laser cut and then anodized black
>
>
> Most laser machines don't like aluminum. It's too shinny, and can reflect
> back into the lens. Look into water jet instead.
>

My panel was .125" 6061 and I got it laser cut for $70 including material.
I never use the panel for an electrical ground, running ground wires to each
electrical device instead so decorative black anodize worked out
beautifully.

Bill Daniels

[Dan, U.S. Air Force, retired]

Morgans wrote:
> "Bob Kuykendall" > wrote >
>
>>These days I use a single-point suicide cutter as others mention.
>>
>>Thanks, and best regards to all
>
>
> I haven't seen anyone mention the importance of being safe, with a fly
> cutter.
>
> If you have never used one, on something like a panel, clamp it down to the
> drill press table, like you never have clamped anything before. Then double
> the clamps.

Excellent point. Sounds like I am not the only one who learned the hard way.

Dan, U.S. Air Force, retired

[Roger]

On Sun, 10 Jul 2005 22:42:32 -0400, "Morgans"
> wrote:

>
>"Bob Kuykendall" > wrote >
>> These days I use a single-point suicide cutter as others mention.
>>
>> Thanks, and best regards to all
>
>I haven't seen anyone mention the importance of being safe, with a fly
>cutter.
>
>If you have never used one, on something like a panel, clamp it down to the
>drill press table, like you never have clamped anything before. Then double
>the clamps.

I would suggest that the safety issue of clamping applies equally to
using hole saws as well as fly cutters. I once had a half inch drill
bit hang up in a 4" X 12" piece of soft Aluminum 1/4" thick. When I
looked around after getting that sucker stopped all you could see were
eyeballs peaking over the tops of the work benches out in the shop. At
the first "clang" every one dove for cover. Man, but it was quiet in
there! Nobody wanted to look as they were afraid of what they were
going to see.

I never knew a good 1/2" drill bit could spring that far without
bending or breaking.

Of course the fly cutter has the added danger of getting caught on
clothing or tender body parts.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

[Smitty]

When I get to my panel, which isn't going to be soon, I'll probably do
it on the mill. But for those who don't have access to a machine shop, I
wonder why you're talking about hole saws and fly cutters. Don't the
Greenlee type punches work pretty well? You only need a small pilot hole
and a couple of wrenches.

[Roger]

On Thu, 14 Jul 2005 08:23:48 -0700, Smitty >
wrote:

>
>
>When I get to my panel, which isn't going to be soon, I'll probably do
>it on the mill. But for those who don't have access to a machine shop, I
>wonder why you're talking about hole saws and fly cutters. Don't the
>Greenlee type punches work pretty well? You only need a small pilot hole
>and a couple of wrenches.

They cut a pretty good hole with cleaner edges than the hole saw and
are physically easier to use than a fly-cutter and safer than both,
but they do have some short comings.

Good hole saws can do a reasonably good job if the piece is firmly
clamped, the drill press, or mill is running very slow, and you use a
good cutting lubricant. Apply a very light pressure when starting the
cut although the saw will probably still grab. You should be able to
cut a nice round hole with out the saw wandering. The edges of the
hole will be a tad rough though.

With a fly-cutter, firm clamping is equally important. In addition
the bit needs to be properly shaped and sharpened as well as set at
the proper angle.

BTW, The quality of the hole with either the hole saw or fly cutter
depends highly on how well the piece is clamped in addition to the
safety issue.

The punches have to be in good shape other wise the edges of the hole
(usually by the points) can roll in and they oft times have a small
lip on the inside. This *usually* isn't much of a problem, however
the pilot hole needs to be a slip fit for the bolt and it needs to be
round if you expect close tolerances in positioning. That brings me
to the next one which is the larger punches. They require a pilot
hole punched with a smaller punch which needs to be a good fit to the
larger bolt. This can either give the user a chance to even out any
misplacement with the first hole, or accidentally add the
displacements to the point of where they are noticeably out-of-line.
I'd probably use a lot of Aluminum <sigh> and I've punched a *lot* of
holes using both the mechanical and hydraulic operated ones.

One final point. This type of punch is *EXPENSIVE*. Good quality
ones large enough for instruments will run well over a $100 and you
need a smaller one for the pilot. Over all it'd probably take about 5
different punches to do a panel with the punches ranging from about
$65 to $150 if they are real Greenlee punches. (Now if you know some
one with a set that's in good shape... <G>)

I was going to purchase a set and came away with a real case of
"sticker shock". I'm still keeping my eyes open for a used set in
good condition though.

Having said all of that, like any of the methods, skill plays a part
from the user and I've seen some very nice panels cut using all three
methods and I've seen some of the rejects too. <:-))

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

[RST Engineering]

Most community colleges have a voc ed program where sheetmetal is one of the
classes offered. Most of them have Greenlee punches up through 5". Your
"class project" could certainly be an instrument panel AND most of them have
CNC machines available also.

Your tax dollars at work; you might as well take advantage of it.

Jim



> One final point. This type of punch is *EXPENSIVE*. Good quality
> ones large enough for instruments will run well over a $100 and you
> need a smaller one for the pilot. Over all it'd probably take about 5
> different punches to do a panel with the punches ranging from about
> $65 to $150 if they are real Greenlee punches. (Now if you know some
> one with a set that's in good shape... <G>)
>
> I was going to purchase a set and came away with a real case of
> "sticker shock". I'm still keeping my eyes open for a used set in
> good condition though.
>
> Having said all of that, like any of the methods, skill plays a part
> from the user and I've seen some very nice panels cut using all three
> methods and I've seen some of the rejects too. <:-))
>
> Roger Halstead (K8RI & ARRL life member)
> (N833R, S# CD-2 Worlds oldest Debonair)
> www.rogerhalstead.com

[Dan, U.S. Air Force, retired]

Roger wrote:
> On Thu, 14 Jul 2005 08:23:48 -0700, Smitty >
> wrote:
>
>
<snip>
>
> The punches have to be in good shape other wise the edges of the hole
> (usually by the points) can roll in and they oft times have a small
> lip on the inside. This *usually* isn't much of a problem, however
> the pilot hole needs to be a slip fit for the bolt and it needs to be
> round if you expect close tolerances in positioning. That brings me
> to the next one which is the larger punches. They require a pilot
> hole punched with a smaller punch which needs to be a good fit to the
> larger bolt. This can either give the user a chance to even out any
> misplacement with the first hole, or accidentally add the
> displacements to the point of where they are noticeably out-of-line.
> I'd probably use a lot of Aluminum <sigh> and I've punched a *lot* of
> holes using both the mechanical and hydraulic operated ones.
>
> One final point. This type of punch is *EXPENSIVE*. Good quality
> ones large enough for instruments will run well over a $100 and you
> need a smaller one for the pilot. Over all it'd probably take about 5
> different punches to do a panel with the punches ranging from about
> $65 to $150 if they are real Greenlee punches. (Now if you know some
> one with a set that's in good shape... <G>)
>
> I was going to purchase a set and came away with a real case of
> "sticker shock". I'm still keeping my eyes open for a used set in
> good condition though.

I have bought several Greenlee hole punches from e-bay relatively
cheaply. My 3 1/8" cost me $100 plus shipping. Two things must be taken
into consideration: first most are used and need to be sharpened and
second conduit punches run 3/8" larger than the given size, e.g. a 2"
conduit punch is 2 3/8" actual. Sharpening is easy with either a medium
grit wheel (you use the side of the wheel) or a good, flat medium grit
whet stone. Punches listed as radio chassis punches are acual size.

Dan, U.S. Air Force, retired

[Orval Fairbairn]

In article >,
Smitty > wrote:

> When I get to my panel, which isn't going to be soon, I'll probably do
> it on the mill. But for those who don't have access to a machine shop, I
> wonder why you're talking about hole saws and fly cutters. Don't the
> Greenlee type punches work pretty well? You only need a small pilot hole
> and a couple of wrenches.

I much prefer the fly cutter, as the Greenlee punches take a lot of
torque and may leave the panel warped in places.

If you turn the fly cutter slow enough and use a good aluminum cutting
fluid, it works well and safely.

--
Remove _'s from email address to talk to me.

[Dan, U.S. Air Force, retired]

Orval Fairbairn wrote:

> In article >,
> Smitty > wrote:
>
>
>>When I get to my panel, which isn't going to be soon, I'll probably do
>>it on the mill. But for those who don't have access to a machine shop, I
>>wonder why you're talking about hole saws and fly cutters. Don't the
>>Greenlee type punches work pretty well? You only need a small pilot hole
>>and a couple of wrenches.
>
>
> I much prefer the fly cutter, as the Greenlee punches take a lot of
> torque and may leave the panel warped in places.


It depends on how sharp the punch is, how thin the metal is and how close
it is to another opening or edge. You can also use them with the panel
insalled in the aircraft.
>

> If you turn the fly cutter slow enough and use a good aluminum cutting
> fluid, it works well and safely.

I would also add the fly cutter MUST be sharp and not fed too fast.

If I were going to start a new instrument panel from scratch I would
take a sheet of 1/2" plywood and bolt the panel blank (cut oversize) to
it. I would use a few of the instrument mounting screw holes as well as
holes along the perimeter of the blank. I would use a fly cutter to cut
the holes. When finished I would cut the panel to size.

This would reduce chatter and make clamping of the entire set up easier.

Dan, U.S. Air Force, retired

[LCT Paintball]

> clamped, the drill press, or mill is running very slow, and you use a
> good cutting lubricant.

One of the best lubes for cutting aluminum is WD-40. I've heard ATF works
well too, but I've never tried it.

[Roger]

On Thu, 14 Jul 2005 20:49:54 -0500, "Dan, U.S. Air Force, retired"
> wrote:

>Orval Fairbairn wrote:
>
>> In article >,
>> Smitty > wrote:
>>
>>
>>>When I get to my panel, which isn't going to be soon, I'll probably do
>>>it on the mill. But for those who don't have access to a machine shop, I
>>>wonder why you're talking about hole saws and fly cutters. Don't the
>>>Greenlee type punches work pretty well? You only need a small pilot hole
>>>and a couple of wrenches.
>>
>>
>> I much prefer the fly cutter, as the Greenlee punches take a lot of
>> torque and may leave the panel warped in places.
>
>
>It depends on how sharp the punch is, how thin the metal is and how close
>it is to another opening or edge. You can also use them with the panel
>insalled in the aircraft.
>>
>
>> If you turn the fly cutter slow enough and use a good aluminum cutting
>> fluid, it works well and safely.
>
>I would also add the fly cutter MUST be sharp and not fed too fast.
>
>If I were going to start a new instrument panel from scratch I would
>take a sheet of 1/2" plywood and bolt the panel blank (cut oversize) to

A very good suggestion.
I keep partial sheets of 1/2" and 3/4" around for for backing and
never even thought to mention using it.

That's what I get for typing at near 3:30 AM.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com
>it. I would use a few of the instrument mounting screw holes as well as
>holes along the perimeter of the blank. I would use a fly cutter to cut
>the holes. When finished I would cut the panel to size.
>
>This would reduce chatter and make clamping of the entire set up easier.
>
>Dan, U.S. Air Force, retired