b_y_m, I thought of the screw extractor things, but I figure it broke because it was rustind in there and would not turn.
Or someone over tightened it, ya never know.
Get yourself some cobalt alloy drill bits before you start.
I've been looking for a set of those for a while, they are going on my christmas wish list
Those cobalt bits are on my Christmas list too.
I use a reversable drill motor and left hand drill bits, usually spins out in the drilling process. First time the bit hangs up it usually spins out.