Hobbing fixture for mill
Milling teeth for a filament drive gives a better "bite" than hobbing with a tap and ensures that the drive is perfectly round and concentric with the shaft. The fixture allows for 24 perfectly spaced teeth.
I used a 2 mm end mill, you could also try a .070" mill for an even closer fit. mctinfo.net is a good source for small carbide end mills. I set the z height about 20 degrees above shaft center for a good tooth angle, you could go as high as 45 degrees.