5C and 16C collets are made of high-strength spring steel.
The front end has 3–6 longitudinal slots to allow radial elasticity; the rear end has threads for tightening. The outside surface is tapered to fit the inner taper of the collet chuck.
Working principle of the collet: The collet is inserted into the collet chuck and pulled from the rear by a drawbar or hydraulic mechanism. The tapered surface is drawn into the chuck body, causing axial movement, radial contraction, and clamping of the workpiece.