This is not my field but, knowing that Tubal Cain's Handbook has a section on this, I looked it up and was baffled not to be able to see a Boley collet with 15mm shank listed. He does list a collet whose "MAXIMUM" DIA is 15mm and 1mm pitch thread, however, which I suppose may be functionally similar to yours.

Edited By ega on 24/06/2022 17:13:34

Is this any help, vic ?

**LINK**

https://www.furniturenmarkt.de/Spannzangen-BOLEY

… aside from making you feel fortunate.

MichaelG.

Surely you can measure the diameter of the thread on your collets and confirm it's 13mm?

Ah, well, the Boxford/Sarf Bend nose thread dichotomy is well known. Usual fix is a tap from Tracy Tools of the relevant UN or BS form, depending on which way you are swinging to clean up the female thread flanks to the relevant standard.

Boley though, being German is most likely Metric thread with 60 degree thread form.

But Crawford, being British, are most likely some BS 55-degree thread form if they are older. Maybe even 1/2" x 26tpi which is pretty close and might screw on for a thread or two or vice versa with the Boley Metric thread. (1mm pitch = 25.4 TPI. 1/2" = 12.7mm) Careful measurment and inspection might show which it is.

Of if the Crawfords are newer, could even be metric too. Rotagrip still sell Crawford collets etc so might be able to help you there.

To add to the complication, some collets have left hand threads, which might start to feel like they are screwing into a right but then bind up pretty much straight away, depending on the relevant sizes.

So one tap/die set to do both may not be do-able. But they only cost a tenner or so.

Edited By Hopper on 25/06/2022 11:15:55

Edited By Hopper on 25/06/2022 11:16:44