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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