Cast iron is commonly used for machinery housings or base due to its damping characteristics. It is also known for holding its shape when it is subjected to contraction and expansion due to temperature fluctuations. Hence lathe bed is usually made up of cast iron.

Revolving Centres are Frictionless. Used for supporting heavy jobs and jobs revolving with high speeds. A high-speed steel inserted centre is supported by two bearings housed in a body. It is also called the revolving dead centre.

The grade of file tool is listed below
1. Rough
2. Bastard
3. Second Cut
4. Smooth
5. Dead Smooth

1) Rough File : A rough file is used for removing rapidly a larger quantity of metal. It is mostly used for trimming the rough edges of soft metal castings.

2) Bastard File: A bastard file is used in cases where there is a heavy reduction of material.

3) Second Cut File: A second cut file is used to give a good finish on metals. It is excellent to file hard metals. It is useful for bringing the jobs close to the finishing size.

4) Somooth File: A smooth file is used to remove small quantity of material and to give a good finish.

5) Dead Smooth File: A dead smooth file is used to bring the material to accurate size with a high degree of finish.