a metalcutting machine tool that performs thread-finishing operations with grinding wheels.
During thread grinding, the part and the tool perform several types of motion relative to one another. The tool rotates about its axis (principal motion); the part rotates (circular feed); the wheel or part moves during each rotation in a straight line a distance equal to the thread pitch (traverse feed); and the wheel moves laterally relative to the part (lateral feed). Thread-grinding machines use single-thread wheels that operate in one direction (the most precise method but one that is not very productive) or in both directions (with forward and reverse strokes). They also use multithread wheels that employ the throughfeed mode (a more productive method) or the infeed mode with cross feed (the most productive method).
Thread-grinding machines may be of the universal (for threading over a great length), semiautomatic, or special type. Universal thread-grinding machines are the most common. They are used for grinding straight and taper threads of thread gages (threaded plugs and rings) and thread-manufacturing tools (taps, round threading dies, and thread-milling cutters), as well as for machining hobs, precision hobs, and screws. Thread-grinding machines are usually equipped with automatic devices for adjustment of the grinding wheels. Thread grinding at a pitch of up to 2 mm is performed directly on a smooth blank, and grinding at a pitch of more than 2 mm is performed after a preliminary cut.
A. A. SHISHKIN