Tegheim - Home made 4 rotor Wolvo 142

[RICE RACING]

Cause the parts are not round perfectly and the three jaws tighten on a common scroll/worm what happens is it stresses these, its basic theory, this is why on black steel you never use a three jaw chuck. Every workshop I have ever been in has been the same.

I agree with you and your boss though I basically never myself use anything but a 3 jaw regardless of it being black or bright bar