giving me a hard time. I could not apply too much force for fear of breaking the whole bolt, and I knew I could not use a torch to heat it. Here are some suggestions I found for loosening the threads.
Get as much of a sodium hydroxide solution as possible into the thread assembly and slowly loosen the nut. However, the solution is very corrosive and will cause alkali burns, so be careful.
Another suggestion is using a box-end wrench of the appropriate size and applying just enough force to put the bolt in tension. While the bolt is in tension, sharply tap the head of the bolt once or twice with a small 4-oz ball-peen hammer. Then stop, and apply tension in the opposite direction and sharply tap with the hammer again. Reverse this procedure several times until the bolt begins to thread out.
If space allows, soak the fastener in a penetrant, put a wrench on it and hang a sledgehammer or some other weight on the wrench to maintain tension. Let this setup sit for overnight, and the next morning the nut should be loose.