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. However, if the collet stretches too far, it cannot secure the instrument properly and may lose shape.

Collets Vs Jaw Chucks. Collets and chucks are two common types of mechanism used to hold spindle tooling or workpieces. Technically speaking, a collet is a type of chuck, but the two terms are usually used exclusively. A 'chuck' usually refers to any type of work holder which is not a collet.

However, the collet is most often used in routers to hold the cutting bits in place. The collet is secured to the tool using a hexagonal collet nut, allowing it to be tightened or loosened to the motor arbor.

Never use tools with homemade, hand-ground flats in a side lock end mill holder. From a low-speed specialist to high, collet chucks work best at elevated rpm. This makes them excellent for delicate and precise work like drilling, reaming and finish milling.