Can you take a snap shot of the crank gear and paste the image to a response? If we can see what you are up against we might be able to direct you more effectively with some real world experiences.

IMHO-cobalt bits are one of the best bits to use; however you do need to keep in mind that when a drill bit spins too fast all it will do is burn the cutting edge. When drilling you want to see curly cues of steel being removed, if you do not see them than you are spinning the bit too fast..........