Chuck is a mechanical device used to clamp workpiece on a machine tool. The workpiece is clamped and positioned by radial movement of movable claw distributed on the chuck body.

Chuck generally consists of chuck body, movable claw and claw drive mechanism 3 parts.

The minimum diameter of the chuck body is 65 mm, up to 1500 mm, the central hole, so as to pass through the workpiece or pipe; The back of a cylindrical or short conical structure, directly or through the flange and machine tool spindle end connected.

Chucks are usually installed in lathes, cylindrical grinder and internal grinder, but also with a variety of indexing devices, used in milling and drilling machines.