An operation in which a drill enters the workpiece axially and cuts a hole with a diameter equal to that of the tool. On a milling machine, an end milling operation is required to produce a hole with a tool smaller than the hole diameter. A drilling operation typically produces a blind hole, which extends to some depth inside the workpiece, measured to the point made by the tool or to the end of the full diameter portion. On a milling machine, a hole that extends completely through the workpiece (through hole) can also be drilled.