Every hardened gear leaves the furnace slightly different from how it entered. Case carburizing adds carbon, quenching adds stress, and together they add distortion — typically 20 to 60 microns of it. For a pump gear that may not matter. For a robot joint or an aerospace actuator, it absolutely does.

Continuous-generation grinding is the answer. A dressed threaded wheel meshes with the hardened gear like a worm drive, shaving flanks in a constant rolling contact. Because the process mimics the way the gear will actually mesh in service, it corrects lead, profile, and pitch simultaneously rather than tooth by tooth.

The payoff shows up on the analyzer chart: profile deviations inside 3 µm, lead inside 4 µm, and pitch variation you need a logarithmic scale to see. That is AGMA 12 territory — the difference between a gearbox that hums and one you can hear across the shop.

When your application is torque-dense, quiet, or safety-critical, specify ground flanks and ask for the analytics chart with the shipment. If your supplier can’t produce one, that tells you something too.