Twist by rotary cutting its relatively fixed axis of the workpiece to the hole drilling tools. Because chip flutes twist into a spiral shape and name. There are 2 slot spiral groove, 3-slot or more slots, but the two most common slot.

Limiting aperture diameter twist by spiral grooves make more detailed core drilling, drill rigidity is low; only two edge band guide, easily skewed axis hole; chisel difficult to make a centering axial resistance increases, drill easy swing. Therefore, drilled hole shape and position errors. Twist the rake face and flank are curved, each point along the main cutting edge rake angle, relief angle vary, the rake angle of the chisel edge up to -55 °. Cutting conditions are very poor; cutting along the cutting edge distribution unreasonable, the lowest intensity maximum cutting tip, so badly worn. Thus, the hole machining accuracy is low. Full drill main cutting edge to participate in cutting edge, the cutting speed of each point on the edge without equal, easy to form a spiral-shaped chip, chip removal difficult.

Therefore, chips and the hole wall friction extrusion, often scratching the hole wall, the surface roughness after machining is very low.