I can see where that would work also. I ground down to the squared portion and stopped there. Because I kept it concentric and treaded to the very end, it matched perfectly right up to the new knob edges with no overhang. Granted I did have slightly less then the recommended .6" threading but not an issue. Plus when I am done putting the rifle together, I will be cerakoting the entire action/barrel/bolt to contrast and match the chassis system I go with.I have freehand ground down four bolt knobs then threaded them. Not for the mechanically challenged.
I saw an alternative: cut off round knob. Drill and tap shank to epoxy in a threaded stud. Knob threads on to the stud.
I make my own knobs and prefer to counter bore near the opening, so a thin tapered section of the bolt knob blends into the handle with a more pleasing effect.