A cold-working process in which a stream of hardened shot strikes the tooth surfaces, especially the root fillets, plastically stretching a thin surface layer and leaving it in compression. The compressive stress resists crack initiation and can raise bending fatigue strength substantially. It is controlled by Almen strip intensity and coverage checks, and is commonly specified on carburized gears after heat treatment.
Spec calls for shot peening the roots after carburize, so mask the bore and send a set of Almen strips with the job.
Also heard as
- peening
- shot peen
Related terms
Tooth breakage
A gear tooth cracking off, most often by bending fatigue starting in the root fillet on the loaded side.
Bending stress
The tensile stress in the root fillet of a loaded tooth, which decides whether teeth break off.
Carburizing
A heat treatment that diffuses carbon into the surface of low-carbon steel gears, then quenches for a hard case.