Can you identify this collet ?

[Jon. B]

Hi, have acquired a boring bar holder (and a good number of boring bars) that uses a collet system that is not identifiable by myself or the local machinery suppliers.
In the collection are a few 1/2 inch bars but unfortunately no 1/2 inch bore collet

Quick sketch is attached. Wondering if anyone with some more wisdom can identify the collet system
Measurements are digi caliper accuracy and thread pitch looks to be 26 TPI

If anyone has some ideas we can remeasure to a higher degree of accuracy if required.

Thanks in advance

 

[Jon. B]

Hmm, sorry about the crappy image placement in the post....it didn't look like that when i was composing it...honest..

 

[wachuko]

So not a 3C…

 

[Technical Ted]

Attached is a list with various collet brands/dimensions.

Ted

 

[Jon. B]

So not a 3C…

View attachment 416271

No, not a 3C. That's everyone's first guess, then they realise the length of the taper is much longer

 

[Jon. B]

Attached is a list with various collet brands/dimensions.

Ted

There are a couple of odd ones in that list that look close. I'll do some further research and see what i can find.
Thanks Ted

 

[brino]

One of the best references I have seen was from Daryl (@Uglydog) in this post:

https://www.hobby-machinist.com/threads/is-there-a-definitive-article-on-collets.36227/post-313640

Good Luck!
Brian

 

[Jon. B]

Thanks to all who have responded. So far nothing looks even close. If a collet is shown as long enough, it's too big diameter-wise etc.....
If all else fails, i could get on and build a tool-post grinder and slightly reduce the bar shanks to 7/16, lots of options !

 

[extropic]

Please post some pictures of the boring bar holder. I'm interested to see what type of boring bar holder uses collets.

 

[Jon. B]

Here you go extropic

"Loaded" and "unloaded"