if you are modifying the crank, none of the carbide metal bits are strong enough, or sharp enough to modify a crank. you need to use a stone bit. (i use the green stone bits made by dremel. these are the hardest stone bits available. you need to use this.

ALSO ALWAYS USE PROTECTIVE EYEWEAR!! IF YOU DON'T HAVE IT, GO BUY SOME. NEVER DREMEL WITHOUT IT!

for eye wearl i use the full face masks, these are better, because when you use a wire brush to eventually polish the crank parts you moded the steel brush peices tend to fling of.

ALSO, USE AUTOSOL, OR ANY METAL POLISH FROM THE CAR SECTION TO POLISH THE CRANK AND BRASS SECTION OF THE SLEVE.