Gear hobbing, shaping, and grinding are three common methods for producing custom gears, each suited to different precision and volume requirements. Hobbing uses a rotating helical cutter (hob) to generate teeth progressively. It is fast, economical for medium-to-high volumes (100+ pieces), and works well for spur and helical gears up to AGMA Q10–11.
However, hobbing cannot cut internal gears or gears with adjacent shoulders. Gear shaping uses a reciprocating cutter that mimics a mating gear. It can produce internal gears, splines, and gears with close shoulders, but it is slower than hobbing and typically achieves AGMA Q9–10.
Gear grinding removes material from hardened gears using an abrasive wheel. It achieves the highest precision (AGMA Q12–15, DIN 2–4) and excellent surface finish, making it essential for high-speed, high-load applications like aerospace transmissions and electric vehicle drivetrains. Grinding is expensive and slow, often reserved for gears that require post-heat-treat finishing. In practice, many custom shops hob or shape gears in the soft state, heat treat them (e.g., carburize to 60 HRC), then grind the critical profiles to correct distortion. Choose hobbing for cost-effective production, shaping for internal or obstructed geometries, and grinding for maximum accuracy and durability.