ER is the collet system most shops already own, which is why the choice is rarely the collet — it is the nut and the nose diameter. Mongtec builds ER11 through ER50 to DIN 6499 on BT and BBT tapers, in four nut styles, because the same ER32 chuck can be the right answer or the wrong one depending on what is standing next to the cut.
| ER11 | 1 – 7 mm |
|---|---|
| ER16 | 1 – 10 mm |
| ER20 | 1 – 13 mm |
| ER25 | 2 – 16 mm |
| ER32 | 2 – 20 mm |
| ER40 | 3 – 26 mm |
| ER50 | 6 – 34 mm |
| UM nut | The main range. Balanced nut, better runout and higher speed than a hex nut |
|---|---|
| Hex nut | Tightened with an open spanner. Lower cost, G6.3/15000 |
| Mini nut | Smaller nose diameter — use it when the nut, not the tool, is what hits the workpiece |
| GER nut | Sealed style for coolant-through work |
| Short body | Where Z clearance is the constraint |
BT30 / BT40 / BT50 · BBT40 / BBT50
70 / 100 / 160 / 200 / 250 / 300 mm
If the operation needs better runout than a collet can give, the same ER interface exists as a shrink fit ER collet chuck and a shrink ER extension. Shrink fit tool holders →
Body diameters (D, D1), gauge lengths (L2, L1) and the set-screw thread (G) are in the printed catalogue and are supplied with the quotation.