A parts carrier assembly for a grinding machine includes an annular parts carrier and a bearing insert. The annular parts carrier includes an upper surface, a lower surface, an inner edge, an outer edge, and a plurality of loading apertures. The inner edge is configured to engage a driving wheel of the grinding machine. The driving wheel rotates about a central axis resulting in rotation of the parts carrier about an offset axis, which is offset from the central axis. The loading apertures are configured to receive parts to be ground by the grinding machine. The bearing insert includes an inner bearing surface complementary in shape to the outer edge of the parts carrier. The outer surface the parts carrier bears against the inner bearing surface of the bearing insert as the parts carrier rotates about the offset axis.