Taper shank twist drill is the most widely used hole processing tool, usually in the range of 0.25 to 80 mm in diameter, and it is mainly composed of a working part and a shank. The working part has two spiral grooves, which resemble twists, hence the name. Unlike straight shank twist drills, taper shank twist drills have a taper shank. Twist drills of different specifications have different Morse taper.