Which are the collets that uses the Klaiber WS2 tool grinder? I found the answer few days ago while looking at ebay.de. A seller was offering a Klaiber grinder.  In the machine pictures there was this one:

It is a 6mm collet for the klaiber. The picture has the answer!! Klaiber collets are of type 317E. It was a non usual collet size. I have not found any provider offering it. If somebody knows the nominal dimensions for this standard, I will be happy to hear about it ;-).