Otherwise the holders would be identified as being "NBTB 30" instead of QC
That said, some nmtb holders may fit up okay depending on who it was made
them and when....
Recalling there being outer nut with a pair of inner tangs on the qc
series--and if the flange is too thick or thin then its just not gonna work.
Anyhow, below is a couple of links that might apply :
Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here.
All logos and trade names are the property of their respective owners.