A
chuck is a specialized type of
clamp used to hold an object, usually an object with
radial symmetry, especially a
cylindrical object. It is most commonly used to hold a rotating tool (such as the
drill bit in a
power tool) or a rotating workpiece (such as the
bar or blank in the headstock
spindle of a
lathe). Some chucks can also hold irregularly shaped objects (ones that lack radial symmetry). In some applications, the tool or workpiece being held by the chuck remains stationary while another tool or workpiece rotates (for example, a drill bit in the tailstock spindle of a lathe, or a round workpiece being milled by a
milling cutter).