Seized Yoke Knob

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.