My manual conical burr mill gave up the ghost. The plastic bushing/drive nut cracked in half. There's room in the back of the ceramic burr for 4 wings on the bushing, so I added more. The original only had two.
MakerGeek (eek!) PLA
210C Nozzle, 60 Degree Bed, Bed made of 1mm thick, fine sanded PEI
I reccomend a 0.4 mm diameter or smaller nozzle, wtih 200 micron layer thickness. Make it solid, since it's a mechanical part.