MIZZZZZEREEEEE!!!
Danged screws have been heat treated. Even a Cobalt drill meets it's match with a screw that has had its point and threads hardened to around C60.
The only was I was able to remove screws from Quicksilver was by grinding broken off stud flat, even though I had to grind a few thousandths of frame metal to do it. I used an excellent quality center-punch (and had to grind the point every third screw), then I used a 1/16" carbide pilot drill then a #10 follow-up carbide drill on 1/4" self-tapping screws. Drill RPMs are critical. I over-sped things a couple of times, and my wallet got slapped around. Lucky lucky me. Had I broken-off a carbide drill in the screw, the show would have been over.
Best of luck and fortune to you! My episode really tried my patience, and I still smart from it almost 20-years later.
