Chuck (engineering)
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![Self-centering three-jaw chuck and key with one jaw removed and inverted showing the teeth that engage in the scroll plate. The scroll plate is rotated within the chuck body by the key, the scroll engages the teeth on the underside of the jaws which moves the three jaws in unison, to tighten or release the workpiece.](/Images/godic/202501/23/ThreeJawChuckKey4946.jpg")
![Top: an assembled keyless chuck. This type of chuck is tightened by twisting the body using firm hand pressure only. While convenient, this feature can cause the chuck to loosen if too much torque is applied. Bottom: the widely used keyed type of drill chuck with its key. The arbor is shown separately to the right. These chucks require a toothed key to provide the necessary torque to tighten and loosen the jaws. When the key is turned its teeth mate with teeth on the chuck, turning an internal screw which in turn moves the threaded jaws in or out along a tapered surface. The taper allows the jaws to clamp drill shanks of a range of diameters. The end view shows the three small jaws that slide within the body.](/Images/godic/202501/23/ChuckDrillKeyedKeylessArbor4946.jpg")
![Two pin chucks. The top one is assembled, the lower one shows the body and nose cap assembled with the collet piece below it.](/Images/godic/202501/23/PinChucks4946.jpg")
A chuck is a specialized type of clamp. It is used to hold an object with radial symmetry, especially a cylinder. In drills and mills it holds the rotating tool whereas in lathes it holds the rotating workpiece. On a lathe the chuck is mounted on the spindle which rotates within the headstock. For some purposes (such as drilling) an additional chuck may be mounted on the non-rotating tailstock.