Properties of Tool Material

The desirable properties of tool material are following:

Wear Resistance

Wear resistance must be as high as possible. Wear of tool is caused by adhesion, abrasion and diffusion. Wear resistance is ability of tool material to retain its sharpness and shape for longer duration whereas machining is continued.

Hot Hardness

It is the measurement of the ability of tool material to keep its hardness at high temperature. Hot hardness must be as high as possible especially at high temperature.

Toughness

It is the ability of material to absorb energy and plastically deform before failure and fracture. Tougher material has more ability to withstand external load, impact and intermittent cuts. Therefore, toughness should be as high as possible.

Coefficient of Thermal Expansion

Coefficient of thermal expansion estimates the influence of thermal stresses and thermal shocks on a material. It must be as low as possible so that tool does not get distorted after heat treatment, and remains simple to regrind and also simple to weld to the tool holder. Carbide contain lower coefficient of thermal expansion than high speed steel and they build lower thermal stress but are more sensitive to thermal shock due to their brittleness.

Hardness

This is the ability of material to resist the, scratching, penetration, abrasion or cutting. Hardness of tool material must be as high as possible. In general it should be higher than workpiece.

Thermal Conductivity

It must be as high as possible with a view to eliminate the heat quickly from chip tool interface.