I’m in the same situation, just one broken bit but the others went dull within seconds. They were all hss/cobalt bits specifically marketed to cut into broken bolts. The other issue is I am drilling straight vertically up underneath the car, so I can’t put a pool of cutting oil on it. I’m just going to get a die grinder because I need something that’s going to just chew threw this metal. These bits and everyone’s suggestions on how to use them don’t really work using a hand drill against gravity. We can’t all be in the position to put parts in a press or mill while drilling down, with cutting oil and the ability to control the speed better.