What size hole saw do I use?

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.

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.

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

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.

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

"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

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

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

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