This is what I use for a stop, M6x1 setscrew in a hinge up guide bar, in this case it allows the part to extend out of the jaws so the corners can be radiused, i end done ready to turn around for the other end.
Usually I set the left end of the rear vice jaw as X=0 and the face of the rear jaw as Y=0, top most surface of the work is Z=0
Mainly only making small aluminium parts (see my Album) so vice jaws are only lightly closed, but enough to hold the workpiece.
In the picture below the stop has been swung back clear after setting the part in the jaws, the end of the work is set to the OD of the tool rubbing before moving to radius both corners.
Emgee

Edited By Emgee on 27/10/2019 18:49:29