What size hole saw do I use?

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.

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wrote in message
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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

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

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

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.

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

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.

"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