Why Choose ER Collets? ER collets are slotted (alternately) from both ends and therefore compress onto the cutter along the whole length of the collet when tightened. This not only provides a better grip on the cutter shank but also allows some variation (typically 1mm) in shank sizes that may be used in a single collet. The smaller size collets are best used to hold cutters no more than 0.5mm below the nominal size. Inspecting the inside of our ER collet nuts reveals an internal flange that has been machined eccentric to the main axis of the nut. This is not a machining error but is designed that way to lock onto the groove of the collet and aid its release from the chuck body. For this feature to work properly, the collet must be mounted in the nut first before fitting the assembly into the chuck body. To mount the collet in the nut, insert it on an angle, turn slightly and push it into the nut until it clicks into place on the eccentric flange. The cutter may now be fitted and the assembly tightened hard into the chuck body. To remove the cutter, slacken and undo the nut until resistance is felt. Then, using a collet wrench, further undo the nut until the collet is released from the chuck body. Removal of the collet from the nut is the reverse of the mounting procedure. Item Code Nominal Size Clamping Range 020-021-25010 1.0mm 1.0 - 0.5mm 020-021-25015 1.5mm 1.5 - 1.0mm 020-021-25020 2.0mm 2.0 - 1.5mm 020-021-25025 2.5mm 2.5 - 2.0mm 020-021-25030 3.0mm 3.0 - 2.5mm 020-021-25040 4.0mm 4.0 - 3.5mm 020-021-25050 5.0mm 5.0 - 4.5mm 020-021-25060 6.0mm 6.0 - 5.5mm 020-021-25070 7.0mm 7.0 - 6.0mm 020-021-25080 8.0mm 8.0-7.0mm 020-021-25090 9.0mm 9.0-8.0mm 020-021-25100 10.0mm 10.0-9.0mm 020-021-25110 11.0mm 11.0-10.0mm 020-021-25120 12.0mm 12.0-11.0mm 020-021-25130 13.0mm 13.0-12.0mm 020-021-25140 14.0mm 14.0-13.0mm 020-021-25150 15.0mm 15.0-14.0mm 020-021-25160 16.0mm 16.0-15.0mm