Machinability and Machinability Index

The ease with which a given material may be worked with a cutting tool is machinability. The various factors affecting machinability are:

1. Chemical composition of work material

2. Micro-structure

3. Mechanical properties

4. Physical properties

5. Cutting conditions

To evaluate the machinability, the following criteria may be considered:

1. Tool life between grinds

2. Value of cutting forces

3. Quality of surface finish

4. Form and size of chips

5. Temperature of cutting

6. Rate of metal removal

The machinability of different metals to be machined may be compared by using the machnability index of each. It is defined as follows:

A free cutting steel which is machined relatively easily and machnability index of which is arbitarily fixed at 100 percent, is considered a standard steel.