hope this helps..
http://www.contour.org/forums/ultimatebb.php?ubb=get_topic;f=3;t=006405
I was hitting the disks with a sledgehammer and all I managed to do was break bits off. When we used the propane torch, we go them hot enough so they smoked a little, then we still had to wail on them to get them to budge.
Good luck.