Machine tools are nonportable, power-driven tools used industrially for working metal components to tolerances far finer than those obtained manually. The fundamental processes used are cutting and grinding, individual machines being used boring, broaching, drilling , milling, planing, and sawing. Essentially a machine tool consists of a jig to hold both the cutting tool and the workpiece, and a mechanism to allow these to be moved relative to each other in a controlled fashion. A typical example is the lathe. Auxiliary functions facilitate the cooling and lubrication of of the tool and workpiece while work in in progress using a cutting fluid. The rate at which any piece can be worked depends on the material being worked and the composition of the cutting point. High-speed steel, tungsten carbide, and corundum are favored materials for cutting edges. Where several operations have to be performed on a single workpiece, time can be saved by using multiple-function tools such as the turret lathe, particularly if numerical rather than manually controlled.
Modern industry would be inconceivable without machine tools. It was only when these began to be developed in the late 18th century that it became possible to manufacture interchangeable parts and thus initiate mass production.
Advanced machine-tool processes include cutting by means of laser beams, high-pressure water jets, streams of plasma (ionized gas), and ultrasonics. Machine tools are now increasingly controlled by microprocessors, computers, and robots.