A gear specification touches five decisions: type, module, quality grade, material and heat treatment. Miss any one and the drive vibrates, runs hot or wears out prematurely. This guide walks through the checklist procurement engineers use to specify industrial gears with confidence.
SEC. 01
Choose the gear type
- Spur — parallel shafts, low speed, quiet duty; the default and cheapest.
- Helical — parallel shafts, higher speed and load, quieter than spur.
- Bevel — intersecting shafts (usually 90°), power take-off duty.
- Worm — perpendicular shafts, high ratio and self-locking, lower efficiency.
SEC. 02
Quality grade to DIN 3960 / AGMA 2015
DIN quality 8 is standard for general industrial drives, DIN 6 is precision-machined and ground for higher speeds, DIN 4 is aerospace-grade. Every step up roughly doubles the price — specify only what the duty needs.
SEC. 03
Material and hardening
- C45 — soft general-purpose gear, HB 200–230.
- 40Cr / 42CrMo — alloy steel, induction-hardened teeth to HRC 50–55.
- 20CrMnTi — case-hardened, ground gear teeth for heavy shock loading.
- Ductile iron GGG50 — economical, damps vibration, moderate loads.
Key Takeaways
- Type first (spur/helical/bevel/worm), then quality grade, then material.
- DIN 8 covers most industrial drives — upgrade only for speed or noise reasons.
- Induction- or case-hardening on the tooth flanks is standard for wear duty.
- Always specify balancing grade for gears running above 1,500 RPM.