S4 Repair Tip

I had an S4 lamp base with a stuck x-y knob. The nut was locked up on the threaded end of the index hub. All my gentle persuasion, graphite, and machine oil would not help. I even tried locking pliers but could not get a good grip on the x-y knob and risked damaging it. I finally tried my air duster, upside down so the liquid spayed out, and cooled the index hub with a couple of seconds of cold. This shrunk the  index hub enough that I was able to remove the nut by hand.