I picked up an old, 80's, Schwinn 10speed that has a heavily rusted frame. I'm trying to remove the fork and found, not suprizingly, it is frozen to the stem. I searched the forum and tried the following, I removed the center bolt and sprayed liquid wrench into the tube, then I inverted the bike and sprayed the tube from the bottom, then waited one day. I backed out the center bolt about 1/4 inch and hit it with a rubber mallet to break the quill loose. The threads promptly stripped so the center bolt has no purchase at all. I've loosened the nut at the top of the head so the fork and stem, together, are loose within the frame, but there is no separating the two. Short of taking a saw to the stem, is there anything else I can do to separate these two and salvage the fork?