So, I finally got around to making the rollers. Here's how I did it:

1. cut the head off an m6 bolt

2. put the bolt in the chuck of my drill press

3. clamp the shortest, stubbiest drill bit I could find in a little clamping mount

4. hold the mount down on the table so that the drill stays vertical but can move around laterally

5. drill a small divot in the end of the bolt

6. take the bolt out of the chuck and put two nuts on the end, tightened against each other. This makes a flat surface to sit on the drill press table while holding the bolt upright.

7. use progressively larger drills to make a hole in the center

This was after several attempts at other strategies, all of which failed. The two major things were:

- just drilling and hoping it would be close enough

- probing the part with a CNC router, then using that to drill the center

But there were a ton of smaller things I tried as well that ended up not working. Anyway, the rollers are finally finished. I'm going to assemble and test it as soon as I can!

Here's how it turned out. It fits great on the 1/8" shaft. The roller is much shorter than this; I need to cut it down still. And yes, I know I need a proper macro lens.