Filament Riveting Tool

For my last project (https://www.thingiverse.com/thing:2754147) I used a short piece of filament for the pins in the hinges. To keep them in, I used a hot air gun to heat up the blade of a knife. Then, I pressed the side of the blade to the end of the filament and melted it until the diameter was about 50% larger than the original O.D. This was functional, but I didn't like the flat end and the sharp edge that it made.

So, I decided to make a tool who's sole purpose is to form a button, or rivet head, on the end of 1.75mm filament. I started with a long #10-32 bolt -- the kind with the blank shoulder area. Typically, screws longer than 2" have 1" of threads and the rest is non-threaded shoulder. A #10 screw has a body diameter of 0.188".

I cut off the head and drilled into the blank end with a 0.110" drill, about 0.020" deep. So, the cavity is a cylinder made by the drill that is 0.110" diameter by 0.020" long PLUS the point of the drill. See picture 2.

Then I drilled