Reamers are rotary cutting tools used to enlarge an existing hole to an exact size and provide a smooth finish to the walls of the hole. Reaming may be done by hand or with a variety of machine tools. Note: When using a reamer, never rotate it in the reverse direction of the cut. This will ruin its accuracy. Machinechucking reamers are most often just called chucking reamers. They have round shanks and are used in drill presses, turret lathes, screw machines, and other machine tools. The cutting end of the reamer is ground with a 45 Degree chamfer angle for easy hole entry. High-Speed Steel Reamers are used on a wide variety of materials including tool steel, cast iron, and aluminum.