This replaces the insert for the ceramic burr in your Java Presse coffee grinder. The original piece on ours cracked and stripped out the notches that the metal shaft grabs to spin the ceramic burr.
The original is nylon. I highly recommend printing it with nylon. I used Taulman 3D Nylon Alloy 910. Alloy 910 is an FDA approved material for direct food contact.
This version of the part fits the metal shaft a little tight. The advantage of it being tight is that it is less likely to strip out the notches than if it is loose. The disadvantage is that it wont slide freely on the shaft, so you have to give the burr a little help when you loosen the adjustment knob by pushing the shaft with your finger. I provided a step file, in case anyone wants to adjust dimensions to get a looser fit.
Nylon 910 is very low warp compared to other Nylons. I have no more trouble with it than ABS. I upgraded my printer to have a PEI print surface. All you have to do to print Nylon on PEI is put a light layer of PVA (Elmer's purple glue stick is what i use) down on the bed and heat to 60C. The film of PVA will wash off the bed and the part with water.
Be sure to wash the part with water before use. Nylon Alloy 910 is approved for direct food contact. But, if you used Elmers glue for bed adhesion, you will want to get it off the bottom of the part before grinding coffee. Elmer's glue is non-toxic, but I still don't want it in my coffee.