Put the nut on the re bar heat both till red then smash the nut. I don't think your getting the nut hot enough.
Ok thanks. I'll try that
It worked!!!
Thank you for your advice.
Question.... Do you smash it on all sides or just one? It seems like if I smashed it on all sides (because after smashing on one side it leaves air space on the other two sides) it might loosen up but maybe not.
I put the brass nuts on the rebar, put the rebar in a regular fire (not a forge), waited for 10-15 minutes, took it out and banged on it with a sledge hammer onto a railroad steel plate I had sitting on a log (although as you mentioned I'm sure a trap hammer would have worked as well). It took a few bangs but it worked. I also think drilling out the threads (which I did on some but not all) worked better since I made more room for it to crush.
Update: Note: The nuts won't necessarily look "red hot" but they will be. Take them into a dark room and you'll see them glowing red but the brass (or whatever coating is on them) I think shields that possibly. About 10-15 minutes in the fire you can bang on them. Use vice grips to position the nut, wear safety glasses, and hold on to the bottom of the rebar as it should be cool but wear gloves in case it bounces up or you trip (also why to wear goggles).
A couple of the nuts are still loose after smashing which is why I asked if I should smash on all sides of that could loosen it up? I'll try more this weekend to tighten it up.
Thank you for all your help everyone and The Beav!!!!!!!!!!!!!!!!!