Sooner or later a part will need to be countersunk for a dimple. Fast metal airplanes have tons of them. The problem is getting the depth perfect for the various thicknesses of material and dimple sizes. Multiple countersink cages help. The most common sizes can be left preset, but it’s still a good idea to test and check fit. You could drill a hole in scrap, countersink, then hold it up against the dimpled part, but why not make life easier? Dimple tokens are the answer.
Cut tokens from scrap using the various thicknesses of aluminum on the airframe. Typical thicknesses are .016 inch, .025 inch, .032 inch and .040 inch (.040 inch is the thickest aluminum Van’s recommends be dimpled). I have six dimple dies: 3/32-inch standard, 3/32-inch tank, 3/32-inch substructure, 1/8-inch standard, #6 screw, and #8 screw. I cut six tokens of each thickness, for a total of 24. They can get mixed up easily, so work with one thickness at a time.
Stack up one set and clamp them together. I started by drilling three holes, all #40. One hole is for a hanger, one is a reference hole (same size as the dimple hole) and one is for the dimple. Next, enlarge the hanger hole in the stack to #30.
Remove the 1/8-inch tokens and drill the reference and dimple holes up to #30. Remove the #6 tokens and drill the two holes #29. Repeat the process using a #12 bit for the remaining #8 tokens. Deburr and dimple accordingly.
Next is identification. Markers wear quickly so scratch the thickness and dimple dimensions into the tokens.
Now you’re ready to check countersinks. Just select the appropriate token and every countersink will be perfect.