The balls are formed into rough spheres on cold heading, hot forging, or hot rolling machines.
The balls are ground under pressure between rotating grooved cast iron plates to improve sphericity.
|| Heat treatment:|
The balls are through hardened by heating to 840 ℃ and quenching.
They are then tempered to remove excess stresses.
|| Hard’ Grinding:|
The hardened balls are then ground under pressure between a rotating grinding wheel and a stationary cast iron plate.
|| Finish lapping: |
The balls are carefully lapped to their final dimensions between grooved cast iron plates, one rotating and one stationary.
Varies according to grade from 4% AQL for commercial grades to 100% electronic scan and crack detecting for high precision.