Workpiece will cut the lap

Accuracy can't be obtained

Lap will cut the workpiece

Lapping operation leaves high spots

Cast iron

Aluminium

Bronze or zinc

Copper or brass

To reduce cost

To reduce time

To keep close tolerance

To reduce maintenance cost

Refine the structure

Increase toughness

Increase cutting ability

Relieve stress and strain

Annealing

Hardening

Tempering

Normalizing