Seized Yoke Knob

I have several S4 fixtures where the yoke knob is completely seized up on the bolt.  Anybody have any recommendations on the best way to get it free, short of bashing on it with a hammer?  Thanks!

  • Channel lock pliers or vice grips? I doubt there is room to get any penetrating oil in there. I've had to break the plastic and cut the bolt on a couple. Now I put dri slide on the knobs every year during maintenance.
  • Big pair of pliers. If the knob is not so badly buggered, clean up the threads with a 5/16th bottoming tap. Clean up the threads on the bolt with a threading die. Preventive maintainace is to annually remove the knob, blow out all the brass dust. Touch up the threads if itdoes not turn easily or is squeaking. A little bit of graphite on the threads when reassembling works. Just scrape a carpenters pencil across the threads of the bolt leaves enough.