I was recently visiting with an old gunsmith and he told me a story from his first day on the job as a welder/machinist apprentice that might be helpful to some. His boss sent him and two others up the hill to remove the bolts from a rusty dozer track. They worked all morning beating on a long wrench with no success. Just before lunch the two other boys left becuse the work was miserable and not making progress. After lunch the boss sent him back and he worked a couple of more hours but to no avail. At about 2:00 the boss came by to see how he was doing. He said not very well. The boss sent him up to the shop to get a rosebud torch and a bucket of water. He told him to heat the nut up cherry red and then pour cold water on in. He did what he was told and then the nut came off easily. He said the thermal shock did the trick. He asked his boss why he didn't tell them this at first, and he said he accomplished two things by not telling them. He ran off two boys who wouldn't make it and he taught the him a lesson he would never forget. I tried this myself last week on some rusted nuts and it worked great. If have tried just the heating before and it sometimes works, but the heating and then cooling seemed to work more consistently.