wayne, you're not kidding about that sprocket. mine was an old Bendix, the kind that look like cheap grey metal. i started out with a brand new pilot bit, went right through it. then wouldn't dent the other hole. kept changing out bits, wore out at least 5, and it took me about an hour to drill two stupid holes. that's some crazy strong steel. funny thing though, if you notice, it's a skip tooth sprocket i made myself. snapped off every other tooth with a crescent wrench, then grinded it smooth. the teeth came off with very little force. so it's impossible to drill, but brittle enough to snap. and you're right about the shimano's. i sat there studying that old thread, and looking at my hub, and realized i didn't need to do anything but make the levers.