A collet (pronounced ) is a holding device—specifically, a subtype of chuck—that forms a collar around the object to be held and exerts a strong clamping force on the object when it is tightened via a tapered outer collar. It may be used to hold a workpiece or a tool.
Nomenclature variations
Generally, a collet chuck, considered as a unit, consists of a tapered receiving sleeve (often integral with the machine spindle), the collet proper (usually made of spring steel), which is inserted into the receiving sleeve, and (often) a cap that screws over the collet, clamping it via another taper.
Usually in shop-floor terminology, the terms collet and chuck are used in contradistinction; users speak of holding a workpiece or tool with either a collet or a chuck. This usage refers to the same distinction as does speaking of using either a collet chuck or another type of chuck (scroll chuck, independent-jaw chuck, etc.); the two usages are different ways of saying the same thing. The difference lies in how one thinks of the overall chain of connection between the machine spindle and the thing being attached to it (workpiece or tool). In general terms, the overall system of holding constitutes a chuck, but practically, the receiving sleeve for a collet is often integral with the machine spindle, and from the point of view of naming the parts that are added on to the spindle, they are either a collet (± cap) or a chuck (such as a scroll chuck).[citation needed]
