The reamer uses side edge cutting to ream the hole drilled by the drill bit with low dimensional accuracy and low hole wall smoothness, so that the accuracy and flatness of the hole meet the requirements.

Bit: it is composed of drill tip, cutting edge and chip removal groove (spiral or straight groove), and is mainly used to process workpiece holes without pre-cast holes, and the processed holes are generally poor in cylindricity and roughness;

Reaming drill: it is composed of cutting edge and chip removal groove (welding edge reaming drill), which is mainly used for reaming pre-cast holes or bottom holes to improve cylindricity and roughness, but the holes at this time still cannot be used as pin holes;

Reamer: it is composed of cutting edge and chip removal groove (generally solid cemented carbide), which is mainly used to improve the cylindricity and roughness of the bottom hole;

As can be seen from the above, they are different in structure and machining accuracy.