Collets are holding devices that apply a clamping force to hold a tool or workpiece. The tool or workpieces fits inside the cylindrical inner surface of the collet. The collet's inner diameter is reduced slightly when a force is applied, usually through a tapered outer collar. This reduction clamps the collet to the workpiece.
Collets are generally classified by size. Each collet is designed to a specific size and shape to fit a certain size tool or workpiece.
Two types of collet designs include spring collets and collets that use tapered blocks. Spring collets are designed with one or more cuts along its length, allowing for expansion and contraction. Collets can also be designed with several tapered steel blocks held in circular position by a flexible binding medium (usually synthetic or natural rubber).
Comparison of Collets to Other Tool and Work Holders
When compared to other tool and work holding clamping methods, collets usually are limited to a narrow clamping range. Consequently, many collets are required for projects with materials of varying sizes, which can become expensive.
Advantages of collets, however, make them ideal for repetitive processes. They boast system simplicity, resulting in high process speed; the ability to self-center; strong clamping force; resistance to loosening; and high precision centering.
Applications of Collets
Collets are used in a number of different industries. The most common industry is metalworking, where there exist hundreds of collet designs for different types of projects. In woodworking, collets are used on wood routers to hold the bit in place. Collets are also used in semiconductor work, on internal combustion engines, and for various types of consumer crafts.