What is the purpose of a reamer in machining?

A reamer is specifically designed to enlarge and finish holes to a precise diameter while also enhancing the surface quality of the machined hole. This tool is used after initial drilling to achieve tighter tolerances and a smoother finish that may not be possible with a standard drill bit. The reaming process allows for increased accuracy in the size of the hole, which is critical in applications where components need to fit together precisely, such as in assemblies or when inserting pins and bushings.

While drilling is used to create holes in a workpiece, it does not typically deliver the same level of precision or surface finish that reaming offers. Therefore, using a reamer serves a distinct purpose that goes beyond just enlarging a hole—it ensures that the hole meets specific dimensions and surface quality required for subsequent processes or assembly.