What size hole saw do I use?

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.

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

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

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

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.

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.

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

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