Lathe chuck consists of a body with inserted workholding jaws that slide radially in slots and are actuated by various mechanisms such as screws,scrolls,levers,and cams,alone and in a variety of combinations.The number of jaws varies.Chucks in which all the jaws move together are self centering and are used primarily for round work.Two-jaw chucks operate somewhat like avise,and may be used for round and for irregular shaped workpieces by the use of suitably shaped jaws or jaw inserts.
The accuracy of a chuck deteriorates with usage owing to wear,dirt,and deformation caused by excessive tightening.Independent jaw chucks permit each jaw to move independently for chucking irregular-shaped workpieces or to center a round workpiece.