Need to remove lock cylinder screws

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My 2004 Nissan Sentra is in need of a newer ignition switch and lock cylinder. The two screws holding the part to the steering column have breakaway heads as a security precaution, they say. I was able to use a cobalt drill bit to drill into the screw, and use an extractor bit to remove it. When I tried the same with the second screw, the cobalt bit broke off inside the screw, complicating my repair job. I tried a number of fixes, to no avail. I'm thinking I have two good options left. One is to use a hacksaw to saw off one of the thick clamps holding the part to the column, and the other is to try to use a harder bit to drill through the cobalt bit. Any suggestions would be much appreciated Thanks so much! Doug