YES!
All R8 collets have a 7/16-20 thread, that is what makes them "R8 Industry Standard"
My Bridgeport mill is a clone from China, and it uses standard R8 collets!
The same holds trut for 5C collets!
However, some of the cheezy Chinese machine parts and accessories may not have a perfect thread to accept the world standards, I have had that happen to me on a 5C Collet Closer for my new lathe! The thread in the draw-bar was not made right, and none othe collets would screw in to it!
Eric
www.widgitmaster.com
It's not what you take away, it's what you are left with that counts!