My Hario Skerton grinder got wobbly after a bit of use due to the single plastic point of contact for the shaft, so I designed this bearing to hold the shaft in place.
This is a symmetric piece -- you will need to print two. Then take the grinder apart and insert them around the shaft.
I measured the grinder using calipers, then modeled this part in Fusion 360. The F3D file is attached if you would like to modify the source.
Unscrew the grinder and remove the ceramic bits & shaft. Place the two printed parts around the smooth part of the shaft and hold in place. Insert back into the grinder body, aligning the five ribs with those in the grinder body.