ER Collets

ER collets are the most widely used tool-holding system in CNC machining. The ER system runs from ER8 through to ER40, each size covering a range of shank diameters in 1mm increments and fitting the same spindle nose as standard ER collet chucks and toolholders. All 657 collets in this range are held in UK stock across four grades: standard precision, ultra precision, standard coolant sealed and ultra precision coolant sealed.

Standard precision ER collets offer runout of 0.010mm TIR and are the workhorse choice for general CNC production machining. Available across ER8, ER11, ER16, ER20, ER25, ER32 and ER40 in metric and imperial shank sizes, covering the full range of common milling, drilling and tapping applications.

Ultra precision ER collets are ground to tighter tolerances — typically 0.005mm TIR or better — for applications where tool runout affects surface finish or tool life. These include high-speed spindle work, finish milling and thread milling where concentricity is critical.

Coolant sealed ER collets incorporate a seal ring that maintains through-spindle coolant pressure to the cutting zone. Available in both standard and ultra precision grades, they are suited to high-speed machining and deep-hole drilling where conventional flood coolant falls short.

Not sure which size or grade you need? See our ER collet sizing guide, or the full collet buying guide covering 5C, OZ, GSK and DMC alternatives.