Turning is a machining operation, in which excess material is removed from a rotating workpiece. This distinguishes it from milling and drilling, where the workpiece remains stationary and the tool bit rotates. In turning operations, a workpiece is held in place by a chuck mounted on a rotating spindle or tailstock driven by a motor. The cutting edge of the tool bit - which may be made of various materials depending on the machining operation - is fed into the workpiece, thus cutting away the unwanted material in the form of chips (also known as swarf)