collets

Collets are a type of chuck used to hold tools or workpieces in machining and manufacturing. They consist of a cylindrical sleeve with a series of slots that, when compressed by a collet nut or drawbar, tightly grip the tool shank or workpiece. They are valued for precise concentricity, minimal runout, and quick changes between sizes, compared with three-jaw chucks or other grippers.

Construction and operation: A collet is placed inside a matching collet chuck or spindle tapered seat. The tool shank is inserted; tightening the drawbar or nut causes the collet to contract along the slots and grip the tool. The outer surface is typically conical to engage the spindle taper; the interface converts axial tightening force into radial compression.

Common types and standards: ER collets (ER11, ER16, ER20, ER40) are widely used in milling machines and CNC work; 5C collets are used with certain lathes and small milling operations; straight-slotted collets are used with drill presses and other machines that use dedicated collet chucks. Collets can hold end mills, drills, and other tools within the collet’s diameter range.

Material, maintenance, and safety: Collets are usually made from hardened steel. Use clean, burr-free tool shanks; keep the collet and spindle interface clean; lightly lubricate as recommended; avoid over-tightening and check for wear or cracks. Always ensure the tool is fully seated and use the correct collet size to prevent ejection.

See also: Collet chuck, Drawbar, Spindle.