Pinewood Derby Wheel Runout Fixture

Requires two M3x30 (or 35) bolts and hex nuts and whatever hardware you want to use for attaching the dial indicator. Snug down on the pin just until it stays put but don't crank it down.

Options for the pin that the wheel rides on:

1. I used a 0.095" minor pin gauge (actual 0.0945") since the BSA wheels are usually no smaller than 0.096", 
2. A #41 drill bit which comes in at 0.096" but it might be just too large for some wheels.
3. A 3/32" drill bit is a tad smaller but super easy to get and works if you don't mind a little slop.
4. Get some 2.5mm brass or steel rod stock on Amazon, chuck some into a drill and sand or file it down to diameter.
5. Make your own if you are lucky enough to have a lathe.

If you use a drill bit, put the flute into the fixture and expose the shank.

Print as-is. No supports. Teach your scout how to use it!