Broken Ring Gear bolt
MUCH MUCH easier way than drillin it out. Get a mig welder, or somebody that can mig good. Take a nut about the size of the broken bolt and have them or you hold it right over the broken bolt against the ring gear. Start a bead on the center of the broken bolt and build it up until the nut is welded to the remains of the bolt from the inside. Let it cool and then back that joker right on out.