BT40 or BT40-ER11: which do I order?

Q: BT40 or BT40-ER11: which do I order?

Short answer: Order `BT40-ER11` when you already know the shank size you run (1–7 mm). Order a bare BT40 holder when you will change collet sizes between jobs. 7:24 taper, JIS B 6339, pull stud M16. Buying the assembled BT40-ER11 saves matching a nut and collet yourself.

Question

Accepted Answer

Short answer: Order `BT40-ER11` when you already know the shank size you run (1–7 mm). Order a bare BT40 holder when you will change collet sizes between jobs.

7:24 taper, JIS B 6339, pull stud M16. Buying the assembled BT40-ER11 saves matching a nut and collet yourself.