Collet Nuts

Every ER collet needs a matching nut to convert clamping torque into holding force, and a worn or mismatched nut is one of the most common – and cheapest to fix – sources of tool runout on a CNC spindle. HS Spindles stocks ER8 through ER40 collet nuts in standard and low-profile mini-nut styles, machined to hold tolerance across repeated tool changes. Choosing the right nut means matching the ER size stamped on your collet (ER16, ER25, ER32, ER40, etc.) to the nut, and matching the nut style – standard, slotted, or mini-nut – to the clearance available in your tool holder or spindle nose. If you run compact HSK32E or ISO20 tool holders, the Mini Nuts subcategory covers the low-profile nuts built for those tighter envelopes. Every nut ships with the wrench flats or slots needed for a castle wrench, E-style wrench, or hook spanner, so you can pair it with the correct tightening tool from our Wrenches category. Browse by ER size below, or check Mini Nuts for compact-clearance applications.