Collets are used to hold a tool in a central position as it rotates. As the tool is inserted into the collet, the device expands and provides uniform pressure that holds the tool in place.

Compared with standard triple-jaw chucks with soft jaws, standard collets tend to be inexpensive and more accurate for gripping in the small-to-medium range. Conversely, three-jaw chucks are usually ineffective and cumbersome when used to grip items this small.

Hydraulic chuck The hydraulic membrane provides high clamping force and run-out accuracy. It is very simple to handle, without the need for separate equipment. Collets can be used, which reduces the number of chucks needed and allows coolant to be delivered through the tool (drilling) or through the collets (milling).

Collet fixtures are tools used in machining operations to hold and secure workpieces. As an example,the 5C collet system is a popular standard for holding round workpieces in a lathe, milling machine, or other machining equipment.