3-jaw self-centering chuck, is a tool commonly used in lathes, milling machines, and other machining operatio. It is designed to hold and rotate cylindrical or symmetrical workpieces securely during machining.It has three jaws that move simultaneously and are connected to a spiral mechanism. This design allows the chuck to center the workpiece automatically, euring that it is perfectly aligned with the rotational axis of the lathe or machine tool.