Grinding the heads off was easy, but wasn't enough. I found drilling works best for me. I started a tap hole, and gradually increased drill bit size until the heads came off. Drilling through past the frame for the smaller bits, and just to the bottom of the heads with larger bits. Then pound them out with hammer and punch. I got some new 1/8" drill bits, a drop light, center punch, and chuck key. Why I even tried without those basics?
