Needed a method to enlarge 2" and 2-1/8" auto gauge holes to fit 2-1/4" aircraft gauges. I have a hole saw but needed a way to center it in the existing hole. Came up with this jig.
1. Drill a hole in a hardwood block using a drill press, and drive a steel bushing or spacer into the hole. ID of the bushing should match the arbor bit on your hole saw. Hole should match the OD of the bushing.
2. Cut a groove about 1/4" deep into the block using the hole saw, using the bushing to guide the arbor bit. Chisel out about 1/8" of wood inside the groove.
3. Place a hole blank face down in the hole and use that as a template to mark and drill 4 corner holes. Flip over, enlarge the holes, and drive in T nuts.
4. Using a gauge hole blank or template, mark and drill corner holes in the panel.
4. Fasten the block to the panel face using instrument screws. Drill the new gauge hole on a drill press with the 2-1/4" hole saw, using the bushing to guide the arbor bit. Clamp the block to the drill press, go very slow, and use cutting oil or similar.
5. Debur and sand the hole.
1. Drill a hole in a hardwood block using a drill press, and drive a steel bushing or spacer into the hole. ID of the bushing should match the arbor bit on your hole saw. Hole should match the OD of the bushing.
2. Cut a groove about 1/4" deep into the block using the hole saw, using the bushing to guide the arbor bit. Chisel out about 1/8" of wood inside the groove.
3. Place a hole blank face down in the hole and use that as a template to mark and drill 4 corner holes. Flip over, enlarge the holes, and drive in T nuts.
4. Using a gauge hole blank or template, mark and drill corner holes in the panel.
4. Fasten the block to the panel face using instrument screws. Drill the new gauge hole on a drill press with the 2-1/4" hole saw, using the bushing to guide the arbor bit. Clamp the block to the drill press, go very slow, and use cutting oil or similar.
5. Debur and sand the hole.
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