For twist drills I use the 1 inch boring bar holder that comes with the Dorian set (P/N: D35CXA-4) with a jacobs arbor mounted in it with a Jabcobs ball bearing chuck p/n: 14N. The arbor is a common straight 1" shank to 3JT. Gotta have the ball bearing chuck.
The biggest drill I have pushed is a 1"spade (1" shank,mounted directly in holder)in stainless 316 and have not had a trouble with post holder turning, but I do use a 16" closed end wrench to tighten her down, I think this is the key. I have overloaded and alarmed Z axis several times and no post turning.
For quick aligment of the post mount a 12" long-1" bar in the holder leaving 6" sticking out towards chuck,tighten bar in holder,lock holder on post,loosen toolpost main nut so tool post can move freely,move carriage so the holder is all the way against face of open chuck inserting bar into chuck,tighten chuck down on bar. Now you can jog the X axis to make the machine Z center some easy number to remember (eg;X:11.500" in my case). Now tighten that 1-1/4" main tool post nut down.  |