I am trying to drill out a lug on my old Dakota pickup truck. The cap came off the lug nut. I tried a nut extractor which basically carved the bolt into a nice circle. My next option was to drill out the lug. I was using black oxide bits. The pilot hole went great. I moved up to the next size bit and about 30 seconds in “pow”. It snapped off in the hole. Absolutely no way to get hold of it. Is there a harder drill bit I can use with a hand drill? I can’t even drive the truck somewhere to get it fixed because the tire has separated. The reason this nightmare began. Will a cobalt drill bit cut through the black oxide?
Thanks to everyone for your input! Well I finally got the wheel off. After MULTIPLE cobolt bits I managed to drill down on three sides (triangle) around the broken bit and was finally able to break out the center part with the broken bit. Man I do not ever want to have to do that again. These lug nuts must have been hammered on by a 1000 pound gorilla using a 200 pound wrench...plus they have not been taken off in the last 17 years.
In theory you could try a solid carbide, perhaps even an diamond-tipped, drill bit. Attention: Those tips are probably more expensive than a tow truck to the garage, success is not sure, and need careful handling.
In practice it would be more viable, as Solar Mike commented, to remove the hub and replace it / send it to a garage.
For under $100 US Harbor Freight sells a locking lug nut removal tool set. It is a set of sockets that cut into the damaged nut and allow it to be removed. The advantage of the set over individual sockets is you can use progressively smaller sockets if the lug nut continues to round off.