Air Drills

I have read that the optimium speed for drilling small holes in thin
aluminium is something on the order of 30k rpm which is well beyond what any
of the drills that I have seen are capable of. There is a 15,000 rpm drill
made by US Industrial availible as well as 4500rpm models. If I get the
15,000 rpm model, will it have enough torque for my needs or will I want a
second air drill (I have numerous electric and cordless drills)? What do
you guys use and recommend? Which drills have the best trigger control? I
will be building a Moose.

Mike
MU-2

In k.net Mike
Rapoport wrote:
I have read that the optimium speed for drilling small holes in thin
aluminium is something on the order of 30k rpm which is well beyond
what any of the drills that I have seen are capable of. There is a 15,
000 rpm drill made by US Industrial availible as well as 4500rpm
models. If I get the 15,000 rpm model, will it have enough torque for
my needs or will I want a second air drill (I have numerous electric
and cordless drills)? What do you guys use and recommend? Which
drills have the best trigger control? I will be building a Moose.

Sioux makes a 6000rpm model which I own and highly recommend for sheet
metal work.

----------------------------------------------------
Del Rawlins-
Remove _kills_spammers_ to reply via email.
Unofficial Bearhawk FAQ website:
http://www.rawlinsbrothers.org/bhfaq/

I have read that the optimium speed for drilling small holes in thin
aluminium is something on the order of 30k rpm

----------------------------------------------------

Dear Mike,

That may be true but the key is the definition of 'small' and 'thin.' (30k is
more in the realm of CNC, carbide cutters and so forth. If wer'e talking
rivets the smallest standard size is an AN2 -- 1/16" nominal diameter, in which
case the optimum drill bit rpm is about 6000, usually only obtainable with one
of those special 'needle drills.' (ie, in-line air-drill, generally used for
making the holes for data plates and the like)

AN3's need about 4000rpm, AN4's about 3000.

You can work all this out for yourself. The equation is: SFM / (.2618 x drill
diameter) = RPM.

SFM is 'Surface Feet per Minute;' a constant reflecting the type of material
being drilled. Aluminum is 100, cast iron 70, mild steel 60, alloy steel 40...
it's in all the manuals. (Or usta be :-)

---------------------------------------------------

With your drill-motor running at the proper tool speed (or close to it)
aluminum is virtually transparent to the tool bit -- it takes only an instant
to drill the hole, which comes out nice and round and with square sides because
you haven't stood there pushing on the thing for five minutes, which you DO if
you're using one of those 1200 rpm drills from K-mart or, heaven forbid, that
wunnerful 560 rpm, 12v portable drill from Harbor Freight.

You'll find all this poop and more in the 'RIVETING 101' folder, in the Basic
Sheet Metal folder, in the files archive over on the Fly5kfiles Group. That's
not a real Group, by the way -- nobody swapping stories -- it's just an
overflow archive they opened up after we filled the archival space of the other
common homebuilder Groups (AirVW and Fly5k).

-R.S.Hoover

"Veeduber" wrote in message
...
I have read that the optimium speed for drilling small holes in thin
aluminium is something on the order of 30k rpm

----------------------------------------------------

Dear Mike,

That may be true but the key is the definition of 'small' and 'thin.' (30k
is
more in the realm of CNC, carbide cutters and so forth. If wer'e talking
rivets the smallest standard size is an AN2 -- 1/16" nominal diameter, in
which
case the optimum drill bit rpm is about 6000, usually only obtainable with
one
of those special 'needle drills.' (ie, in-line air-drill, generally used
for
making the holes for data plates and the like)

AN3's need about 4000rpm, AN4's about 3000.

You can work all this out for yourself. The equation is: SFM / (.2618 x
drill
diameter) = RPM.

SFM is 'Surface Feet per Minute;' a constant reflecting the type of
material
being drilled. Aluminum is 100, cast iron 70, mild steel 60, alloy steel
40...
it's in all the manuals. (Or usta be :-)

---------------------------------------------------

With your drill-motor running at the proper tool speed (or close to it)
aluminum is virtually transparent to the tool bit -- it takes only an
instant
to drill the hole, which comes out nice and round and with square sides
because
you haven't stood there pushing on the thing for five minutes, which you
DO if
you're using one of those 1200 rpm drills from K-mart or, heaven forbid,
that
wunnerful 560 rpm, 12v portable drill from Harbor Freight.

You'll find all this poop and more in the 'RIVETING 101' folder, in the
Basic
Sheet Metal folder, in the files archive over on the Fly5kfiles Group.
That's
not a real Group, by the way -- nobody swapping stories -- it's just an
overflow archive they opened up after we filled the archival space of the
other
common homebuilder Groups (AirVW and Fly5k).

-R.S.Hoover

Thanks! How do I get to "Fly5kfiles Group"?

Mike

Mike Rapoport wrote:

"Veeduber" wrote in message
...

I have read that the optimium speed for drilling small holes in thin
aluminium is something on the order of 30k rpm

----------------------------------------------------

Dear Mike,

That may be true but the key is the definition of 'small' and 'thin.' (30k

is

more in the realm of CNC, carbide cutters and so forth. If wer'e talking
rivets the smallest standard size is an AN2 -- 1/16" nominal diameter, in

which

case the optimum drill bit rpm is about 6000, usually only obtainable with

one

of those special 'needle drills.' (ie, in-line air-drill, generally used

for

making the holes for data plates and the like)

AN3's need about 4000rpm, AN4's about 3000.

You can work all this out for yourself. The equation is: SFM / (.2618 x

drill

diameter) = RPM.

SFM is 'Surface Feet per Minute;' a constant reflecting the type of

material

being drilled. Aluminum is 100, cast iron 70, mild steel 60, alloy steel

40...

it's in all the manuals. (Or usta be :-)

---------------------------------------------------

With your drill-motor running at the proper tool speed (or close to it)
aluminum is virtually transparent to the tool bit -- it takes only an

instant

to drill the hole, which comes out nice and round and with square sides

because

you haven't stood there pushing on the thing for five minutes, which you

DO if

you're using one of those 1200 rpm drills from K-mart or, heaven forbid,

that

wunnerful 560 rpm, 12v portable drill from Harbor Freight.

You'll find all this poop and more in the 'RIVETING 101' folder, in the

Basic

Sheet Metal folder, in the files archive over on the Fly5kfiles Group.

That's

not a real Group, by the way -- nobody swapping stories -- it's just an
overflow archive they opened up after we filled the archival space of the

other

common homebuilder Groups (AirVW and Fly5k).

-R.S.Hoover


Thanks! How do I get to "Fly5kfiles Group"?

Mike


http://groups.yahoo.com/group/Fly5kfiles/

WW

In Veeduber wrote:

AN3's need about 4000rpm, AN4's about 3000.

You can work all this out for yourself. The equation is: SFM / (.
2618 x drill diameter) = RPM.

SFM is 'Surface Feet per Minute;' a constant reflecting the type of
material being drilled. Aluminum is 100, cast iron 70, mild steel 60,
alloy steel 40... it's in all the manuals. (Or usta be :-)

I don't claim to have anything close to your experience, but in A&P
school I was taught to use up to 300fpm for aluminum with hss bits,
depending on the alloy used. Out in the garage I have a copy of a speed
chart which seems to justify this. With a plain carbon steel bit your
numbers make a lot more sense so that is probably their basis, but I
think most builders are probably using hss bits if not something better
like cobalt. I do know that my 6000rpm air drill works slicker than
snot for drilling #30 and #40 holes in aluminum. Drilled around 1500 #
40 holes in my wing ribs last weekend using it. The standard 2700-
2800rpm air drills work OK for aluminum but that is the slowest I would
want to use. I'm thinking of picking up a 3600rpm motor for
countersinking, but that isn't a huge priority just yet.

----------------------------------------------------
Del Rawlins-
Remove _kills_spammers_ to reply via email.
Unofficial Bearhawk FAQ website:
http://www.rawlinsbrothers.org/bhfaq/

in A&P
school I was taught to use up to 300fpm for aluminum with hss bits,
depending on the alloy used.

--------------------------------------------------------

Dear Del (and the Group),

I got most of my basic aviation metalsmith training from my uncle Sam between
1956 & 1960. You'll find the figures I've cited in any of the manuals from
that era for any of the services. I happened to be Navy but the basic stuff is
the same in the Air Force manuals (AF Manual 52-11, etc.) which were reprinted
by the EAA.

The figures are for carbon-steel drill bits having an included angle of 90
degrees (ie, standard issue 'aviation' drill bits, at that time) and used dry
(ie, no lubricant).

Drawing from the same sources (ie, military training manuals) you will find 300
SFM listed for lathe & milling operations using HSS bits and cutting fluid.

Other cutting tools (and drill bits) such as 5% Cobolt, carbide or steels
treated with titanium-nitride vapor depostion may be operated at speeds higher
than those listed but their use departs from the issue at hand about which I
think there are three points that need to be made.

The first point is that the typical homebuilder has no idea in the blue-eyed
world as to the relationship between tool-speed and producing an accurately
drilled hole. They are using tools inappropriate to the task and no one
bothers to explain why their eighth-inch drill bit turning only 1200rpm in
their K-mart 1/4" drill-motor keeps skittering across the surface, other than
to tell them they need an air-drill.

Secondly, offering them an equation or a printed table that links rpm to drill
diameter should give them some idea that the two are related, especially if
some stress is placed on the fact that skinny drills must spin faster than
fatter drills. The hope here is they'll pick up the idea that they are dealing
with a CUTTING TOOL rather than some kind of rotary punch, where
one-speed-suits-all and you simply have to PUSH HARDER when making a bigger
hole.

The third point has to do with the Conventional Wisdomites who, having learned
that Faster is Better, run around repeating the highest number they've heard
with regard to drilling, confusing airplanes with dentistry. (If 3000 rpm is
good then 30,000 rpm must be GREAT, right?)

The truth is, most homebuilders are using dull drills, having the wrong angle,
chucked into a K-Mart Blue-Light special turning maybe 1200rpm. I've no idea
if they are using plain carbon steel or nitrided cobalt -- and neither do they.
But I do know that if they are making bad holes the SFM formula I cited will
PROBABLY help them make better ones.

As for the rest of it, as in who has the biggest SFM equation or the longest
drill -- it's difficult to address the matter in a cogent fashion without
getting into the specifics of alloy, temper, drill-type production rate and so
forth. Fortunately, I don't think we have to. The SFM equation I cited may be
the lowest common denominator when it comes to riveting but it will at least
allow the builder to produce good holes, usually with better accuracy and less
effort than they're presently getting with their 1100 rpm Makita and a packet
of 1/8" double-enders from Harbor Freight. There's nothing in the rules that
sez you can't ADD to that by offering other equations specific to particular
alloys or drill bits.

-R.S.Hoover

In Veeduber wrote:

The truth is, most homebuilders are using dull drills, having the
wrong angle, chucked into a K-Mart Blue-Light special turning maybe
1200rpm. I've no idea if they are using plain carbon steel or
nitrided cobalt -- and neither do they. But I do know that if they
are making bad holes the SFM formula I cited will PROBABLY help them
make better ones.

I guess I just associate with a higher class of homebuilders over on the
Bearhawk list. 8^) We don't typically get into drill speed formulas
but for the most part we all use decent tools. Then again, there are
enough holes to drill in the BH wing that using the K-mart special would
almost certainly drive the user completely insane in short order.

----------------------------------------------------
Del Rawlins-
Remove _kills_spammers_ to reply via email.
Unofficial Bearhawk FAQ website:
http://www.rawlinsbrothers.org/bhfaq/

I love my Sioux drill. Great trigger. Mine only goes 2600 RPM. Seems
to do just fine at that speed.

Scott
RV-4 project


Mike Rapoport wrote:

I have read that the optimium speed for drilling small holes in thin
aluminium is something on the order of 30k rpm which is well beyond what any
of the drills that I have seen are capable of. There is a 15,000 rpm drill
made by US Industrial availible as well as 4500rpm models. If I get the
15,000 rpm model, will it have enough torque for my needs or will I want a
second air drill (I have numerous electric and cordless drills)? What do
you guys use and recommend? Which drills have the best trigger control? I
will be building a Moose.

Mike
MU-2

I love my Sioux drill. Great trigger. Mine only goes 2600 RPM. Seems
to do just fine at that speed.

-------------------------------------------------

Dear Scott,

I don' t want to bust up your romance but I suggest you borrow a drill-motor
that turns at a higher speed and shoot a few holes. You really don't know what
you're missing.

I usta have a B&D 'aviation' drill motor, turned something like 4000 rpm. Wore
it out. Had it rebuilt. Twenty years later it needed another rebuild but the
bull-gear was not available at a price I could afford. Since then I've been
using those cheap Chinee imports that turn 3600 rpm, last just about long
enough for one airplane's-worth of holes, throw it away when it gets noisy.
Air tools are nice but compressing air to drive a drill puts you on the wrong
side of the economic equation here in southern California.

That's a point a lot of newbies miss. Pneumatic drill is a real air hog; takes
a pretty good compresser to keep you working. (On the other hand, pneumatic
riveting hammers or squeezers don't use much air.) If a guy doesn't already
have a big compressor, when you add the acquisition cost to the operating cost
and divide by the number of holes, it represents a significant increase in cost
when compared to using throw-away electric drill motors.

-R.S.Hoover