I'm not familiar with "cutting" gears? I imagine maybe it's referring to filing down some jagged edes. The gears in my '89 had burs on some edges so sharp they cut my fingers like a razor blade. And the hardening I think may be the use of cryogenics. From what vaque understanding of metalurgy I do have I believe freezing gears in sub zero temperatures for several hours will cure a component of atleast some manufacturer defects.