Chuck is used for clamping workpieces on machine equipment. Used the radial movement distributed on the chuck body activity jaw , the workpiece clamping and positioning of the machine tool attachment. Generally speaking, chuck jaw diviide into body, activity and jaw driving mechanism . Chuck minimum diameter is 65 mm, maximum is 1500 mm, the central through hole, so that through the workpiece or bar; Back short cylindrical or conical structure, directly or through a flange with the spindle end phase. Chuck is usually installed on the machine, cylindrical grinder, internal grinder, can also be used with different indexing device, used for milling and drilling.