This might be an old trick, but, I just figured it out. I had some bolts broken off on my brothers tractor. Broken off flush and really rusted. Sprayed and left them sit for 3 days, spraying every time one of us walked by. Then drilled and started with an easy-out. I have never had much luck with easy-outs and not this time either. The (^%#@) easy-out broke off. Looking at it I could see that the one we were working on was completely broken off flush. One of the other ones had about a 16th of thread sticking out. Knowing it wouldn't work, I sit a burr on the top to see if I could grab a thread. Nope. While sitting back and looking at the nut sitting there, it hit me. I left the nut sitting on top of the stud and got the wire-feed welder out. I welded inside the nut and attached it to the stud bolt. The combination of the spray, heat, tapping on the top of the stud and all the swearing worked. Put the vise grips on the nut and started to wiggle it. Tapping on the top, wiggle and spray and wiggle and spray. I got them all out this way.