To add cutting ability
To develop high hardness
To remove stress and strain
To increase wear resistance
Annealing
Tempering
Hardening
Normalising
To soften the steel
To refine the grain structure of the steel
Protect work surface
Raise the head width
Provide leak proof joint
Provide access for tools
Check the hole with perfect
Check the inside threaded dia
Check tapered hole with perfect fit
Check the taper accuracy of outside dia