A reamer is a rotating tool with one or more teeth used to remove a thin layer of metal from the surface of a machined hole, and a reamer is a rotating finishing tool with a straight or helical edge used for reaming or repairing holes. Reamers usually have higher machining accuracy requirements than drills due to the small amount of cutting. They can be operated manually or installed on a drilling machine.

Reamers used to process cylindrical holes are more commonly used. The reamer used to process tapered holes is a tapered reamer, which is relatively rare. According to the use situation, there are hand reamers and machine reamers, and machine reamers can be divided into straight shank reamers and tapered shank reamers. Hands are of straight handle type.

The number of teeth of the reamer and the number of teeth of the alveolar reamer affect the reaming accuracy, surface roughness, chip space and tooth strength. Its value is generally determined according to the diameter of the reamer and the material of the workpiece. When the diameter of the reamer is large, more teeth can be selected; when processing tough materials, the number of teeth should be less; when processing brittle materials, the number of teeth should be more. In order to facilitate the measurement of the reamer diameter, the number of teeth should be an even number. In the range of commonly used diameter do=8~40mm, the number of teeth is generally taken as 4~8. The teeth of the reamer can be distributed at equal or unequal pitches along the circumference. In order to facilitate manufacturing, reamers are generally distributed at equal pitches.