Cutting tool wear

Illustration of Cutting tool wear

The cutting tool wears out during machining for a number of different reasons, which adversely affects the cutting result

Cutting tool wear
The edge of a cutting tool wears down during machining which impairs the ability to achieve the desired tolerances and consistent quality.

The cause of tool wear can be divided into the following types, that individually or in combination, will inevitably require a tool change.

A. Crater wear
Crater-shaped wear on the cutting edge of the insert.
Caused by mechanical abrasion when hard particles in the chip, eg oxides or carbides, meet the cutting surface.
Diffusion between the material and the insert accelerates the formation of the crater wear.

B. Flank wear
Smooth wear on the flank of the insert
Caused by mechanical abrasion which, similar to pit wear, occurs due to wear from hard particles.

C. Notch wear
Streaked wear on the bottom of the edge
Caused by mechanical abrasion from harder workpieces which, in the same way as crater wear, occurs due to hard particle diffusion. If a larger notch occurs among the smaller ones, it is probably due to the surface deformation from a previous pass. The notches can also appear on the rake side of the insert.

D. Comb cracks 
Small cracks across the edge
Caused by repeated thermal changes that cause the material to expand and contract, which leads to cracks and subsequent chipping.

E. Plastic deformation 
Deformation at the edge
Caused by weakening of the cutting tool due to overheating, which reduces its resistance to external impact.

Cutting forces
The wear is strongly associated with the cutting forces that a cutting insert is subjected to, which are a result of the tool's design, the angle of the tool holder, the cutting speeds, the choice of material, vibrations etc. Real cutting forces are thus very difficult to calculate.