Prior to grinding, a number of stages are involved in gear manufacturing:
Hobbing is a roughing operation which produces a gear profile
with stock remaining for a final grinding process (see figure 1).
Hardening/Heat-Treating is a group of processes used to
alter the physical, and sometimes chemical, properties of a material.
Treatment involves the use of heating or chilling, normally to extreme
temperatures, to achieve to desired result such as hardening or
softening of a material. Heat-treatment techniques include annealing,
case hardening, precipitation strengthening (age hardening),
tempering and quenching.
Grinding produces a high quality surface finish, correcting any
distortion following heat treating, establishes profile dimensional
accuracy. In some cases, grinding can be utilized to grind gears from
solid eliminating the hobbing process.