Hi. The back gear stop screw on my South Bend 9 lathe seems like it's too short. The lever stop is non-functional unless the screw is all the way in, and then the lock nut won't screw on because too little of the set screw protrudes. The end of the set screw seems worn, with a flat on the side of the tip. The orientation is such that the screw end's cross section looks like a "D". This could be the problem, or the assembly may be missing a brass plug. Is anybody familiar with the arrangement?