Collets

A collet clamps a tool or workpiece by squeezing evenly around its circumference, which gives better concentricity and repeatability than a three-jaw chuck — the trade-off is that a collet only grips a narrow range of diameters, so the system you pick has to match both the taper on your machine and the size of what you're holding.

ER collets are the most common toolholding system, running ER8 to ER40 in metric and imperial, and fitting standard ER collet chucks and toolholders. 5C collets are the equivalent for workholding on a lathe or in a collet block — they clamp on the spindle taper itself rather than sitting in a separate chuck.

OZ, GSK and DMC collets are manufacturer-specific toolholding systems used with matching collet chucks — check your chuck's system before ordering, since these aren't interchangeable with ER or each other. For a full explanation of which system fits which job, see our collet buying guide.