I am currently modeling a helical wear shoe that is supposed to fit over a large screw.  I created the general shape of the shoe by drawing the appropriate helix and sweeping a a rectangular profile over it.  The problem is that this shoe is going to be a casting and has a non uniform pattern cut into (not through) the helical surface that I generated.  Cutting this feature would be no problem if it were on a flat surface but I am having trouble getting it to work on a helical one.  If anybody can help I would apprecite it.