for all who drilled instruments holes one day... panel holes to big

[Bob Axsom]

Aircraft Spruce sells a template for locating the mounting holes. Since you already cut the big hole getting concentricity is a little more tricky but not too bad. By the way, I cut my panel holes with hole saws, hack saws, fly cutters and punch tools. I like the hole saws best.

Bob Axsom

[Rick6a]

CNC is precision and hi-tech but is it really required? Not in my experience. In addition, after generating a few test holes with the brand new tool, I sold the high dollar instrument hole punch when I decided the holes it produced by shearing action could not match the quality I routinely produce using a flywheel cutter and a drill press. That is because there are slight differences in standard hole sizes between one instrument manufacturer and another. I can easily reset the flywheel cutter to compensate for that. The key to attaining that kind of accuracy lies in drilling a test hole or two on scrap before turning it loose on the instrument panel blank. An instrument hole punch is certainly acceptable but it is a one-size-fits-all deal. Add a layer of paint and suddenly an instrument might not fit into its assigned hole without rework. I haven't seen an instrument hole yet....and I've produced two instrument panels containing all manner of square and round holes....that I could not precisely fashion using a simple fly wheel cutter, cut off wheel, rotary tool, and assortment of files.

[dedgemon]

Kay,
I have a instrument hole jig, that will let you drill the 4 corner holes (for both 3.125 and 2.25 instruments). Your welcome to borrow it. I'll try to bring it Thursday if you like.

[KayS]

@ Dave:

sounds cool. what would i do without you guys? :-) i go to germany on wednesday so i can't be at Chris house on thursday. but i give you a call next week when i'm back.

Kay

[longranger]

Originally Posted by KayS

..the holes look great but are slightly larger then the nessecary diameter for the instruments, 1/32...1/16.

Have you measured the hole saws with a caliper? I also used Home Depot hole saws to fabricate a new panel for my Cessna 170 and they came out right on. A couple of things that might cause them to cut slightly larger would be a bent quill on your drill press, or the arbor hole in a cheap hole saw being slightly off center. You might want to check the runout with the saw chucked up.

[rvbldr3170]

you can use, is to make a panel overlay the same size as the panel blank out of .016 aluminum, and be more careful when you drill, punch, poke, the holes through it. You can rivet the overlay to the base panel around the circumference of the orignal panel and across the bottom and it will look great.
Ask me how I know...

[rzbill]

Kay,
If Dave Edgemon's jig has a center hole in it, you may be able to make an allignment plate to fit your sawn holes and work with his jig. This could be lathe turned of course with center hole and OD of proper size.

If lathe is not available, the minimum you need is a triangle with the tips at the right diameter and the center hole in the right spot and size to fit his jig. This could be made via accurate layout with a compass, drill press and hand tools.

You could opt for a square or a pointed cross. Any of the three shapes could be carefully worked to the right dimensions with hand files. Keep the 3 or 4 contact points small, like 1/8" wide or less so the panel hole curvature is less of an issue.

Given these ideas, you might use Dave's jigs to 100% fabricate jigs of your own by adding a larger plate with the 4 screw hole positions.

Good Luck, I hope this helps.

BTW, when I use hole saws on aluminum, I usually grind off the tooth "set" on the OD of the hole saw so the OD is completely smooth and closer to desired dimension. I get reasonable holes with a wobbly Harbor Freight saw set. I didn't use them for instruments though, I used a fly cutter and did test cuts to get the diameters spot on.

[hydroguy2]

Here's a pic of the cub panel Yakdriver built recently. Nicely done

[Airhead]

I plan on getting my panel cut by a CNC with a cheap test panel laser cut out of plastic. A friend (also a builder) of mine located at Spruce Creek, Florida (Laser-logic.com) has a small business doing panels for the local builders. He has both a CNC and a large bed laser. The typical process is to cut the first edition panel out of 1/8? plastic and let the builder do a test fit before cutting the final product on the CNC. For RV?s he has the blank templates so he only needs the instrument/switch locations and sizes (he also has templates for most commonly available avionics and instruments). The machines work with CAD drawing but if you have a dimensioned drawing he can create the CAD dwg. He practically insists on the test panel because he finds the builders 90% of the time find out they want to change something when they put the test panel in place, or a switch or other panel component does not exactly fit in the cutout. The cost is very reasonable, but if you want to spend more he can paint and engrave the panel markings, or add plastic panel overlays.