Tool life is the time a tool will operate satisfactorily until it is dulled. A blunt tool cause chatter in machining, poor surface finish, increase in cutting forces and power consumption and over heating of the tool.
The various factors that affect the tool life are:
1. Cutting Parameters- Cutting speed, feed and depth of cut
2. Tool geometry
3. Tool material & work material
4. Cutting fluid
5. Rigidity of the machine
The cutting speed has the greatest influence on tool life. As the cutting speed increases, too life decreases. Obviously, if a very low cutting speed is used, the tool last a long life. But In case of carbide tools very low cutting speed, usually below 30m/min. may reduce tool life.
The tool life is influenced by feed rate and depth of cut. the tool life decrease with increase in feed and depth of cut. Depth of cut has the least effect on tool life.
The geometry of cutting edge formed by rake angle, relief angle and cutting edge angle influence tool life. The large rake and relief angles provide keen cutting edge to reduce the cutting force and increased tool life. But as the cutting edge is weak, it may cause the tip break easily. The nose radius improve tool life and surface finish.
The physical and chemical properties of material of tool and work influence the tool life by affecting form stability and rate of wear of the tool.
The cutting fluid affect tool life to a great extent. A cutting fluid does not only carry away the heat generated, but reduces the co-efficient of friction at the tool chip interface and increases the tool life.
Higher is the rigidity of machine higher will be the tool life. Lower the rigidity of the machine, higher is the chance of tool failure, by vibration of tool or work piece. Rigidity is the prime requirement in case of intermittent cutting specially when brittle tools are used.
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