Turning

Turning is a machining process in which a cutting tool is held nearly stationary to cut a rotating workpiece. The cutting tool can be slowly moved back-and-forth and in-and-out to cut cylindrical shapes and flat surfaces on the workpiece. Turning is usually done with a lathe. Usually the term "turning" is used for cutting external surfaces, and "boring" for internal surfaces, or holes. Thus the phrase "turning and boring" categorizes the larger family of processes known as lathing. Additionally, "facing" is cutting the ends of the workpiece, to create flat faces. Turning is typically done with either a manual or computer numerical control (CNC) lathe. With a manual lathe, an operator turns cranks to move the cutting tool. On a CNC lathe, the cutting tool is moved by a computer, controlling electric motors to follow a pre-programmed path. Early manual lathes could be used to produce complex geometric figures, even the platonic solids, though this is now usually done with CNC machines. Different turning processes are typically carried out on a lathe, such as straight turning, taper turning, profiling or external grooving. Those types of turning processes can produce various shapes of materials such as straight, conical, curved, or grooved workpieces. In general, turning uses simple single-point cutting tools. The waste metal cut off the workpiece from turning operations are known as chips in North America, or swarf in Britain. In some areas they may be known as turnings. A component that is made by turning is often called a turned part.