Carbide is great against hardened steel. SDS Masonry bits are amazing at it (Obviously, you don't want any impacts or hammer action, and also you'll struggle to find an SDS carbide bit small enough... Plus you will almost certainly want to use this on a pillar drill (which isn't really an issue with a chuck adapter or something that's atleast more precise than your hands.) The dewalt cobalt standard twist drills are another good option.

As you say, depending on what this gear is moving, Epoxy would probably work a treat.