The tool life is an important factor in a cutting tool performance since considerable amount of time is lost whenever the tool is ground and reset. A tool cannot cut for unlimited period. It has a definite life. A blunt tool will cause chatter in machining, poor surface finish, increase in cutting forces and power consumption, overheating of the tool. Tool wear:

a) Wear on the flank of the tool:

Flank wear is a flat portion worn behind the cutting edge which eliminates aome clearance or relief. Flank takes place when machining brittle materials like CI or when feed is less than 0.15mm/rev. Increased wear on the flank will cause excessive temperature due to additional frictional heat at the cutting point. It will rapidly loose its hardness and failure of the tool will be imminent.

b) Wear on the tool chip interface:

It occurs in the form of depression or crater. This is caused by the pressure of the chip as it slides up the face of the cutting tool. This occurs when the feed is above 0.15mm/rev. Actually a limited amount of crater improves the cutting action. When the crater size increases some material that supports the cutting edge will be removed which will eventually lead to the breaking of the cutting edge.

c) Loss of hardness:

Because of excessive heat but under cutting conditions when the temperature and stresses are high, plastic deformations may cause loss of form stability. I.e. cutting ability of the tool. Various
tool material can withstand various heating temperatures before they lose the required hardness.

d) Fracture:

When the cutting force is very large or by developing fatigue cracks under the chatter conditions the tool may fail by fracture.