Go to the hardware store and ask for an "Easy out" with the proper drill bit. I was able to get stubborn Phillips head screws out of a motor head once this way. The Easy out looks like a screw with its threads running the opposite direction. You first start with a hole you make with the drill bit so that the Easy out has something to grip into. Then turn the easy out into the hole counterclockwise using a pliers or a vise grip. The farther it goes in, the better the grip it will have. Just don't drill so deep the head of the screw breaks off. These have never failed me. Good luck.