Industry shorthand for case-hardened gears, usually carburized and then ground to finish. Hard gearing carries far more load per unit size than through-hardened gearing, which is cut after heat treatment to around 300 to 400 HB and finished without grinding. Through-hardened sets are cheaper, easier to repair and run in more forgivingly, so large slow drives use them.
Replacement reducer is hard gearing, half the size of the old through-hardened box for the same torque.
Also heard as
- hardened and ground
- case-hardened gearing
Related terms
Carburizing
A heat treatment that diffuses carbon into the surface of low-carbon steel gears, then quenches for a hard case.
Gear grinding
Finishing hardened gear teeth with abrasive wheels to correct heat treat distortion and reach high accuracy.
Green
Shop word for a gear in its soft, machined state before heat treatment, as in cut green, finish hard.
Run-in
Operating new gears at reduced load at first so surface high spots wear smooth before full duty.