The drill does not produce the correct hole size some time with good surface finish. A hole with precision size can be produced with a good finish off a pre-drilled hole using a reamer tool. The process of the enlarging hole is called reaming.
The reamer is commonly used to remove the minimum amount of metal (100 to 150 micron for rough reaming and 5 to 20 micron for fine reaming) from the hole. During reaming operations, the job should be properly supported and rigidly held. A stock wrench of appropriate size for holding the reamer is used. The reamer must be kept in its correct position about the job. It must be rotated slowly, and excessive feed must not be given. It should always be-be turned in the cutting direction. Sufficient amount of cutting fluid should also be used. When removing the reamer, it must be turned in the cutting direction. Reamers with blunt or chipped edges must not be used.