jillaine - I just remembered how I unstuck another frozen wheel and it was even easier. I cut a piece of leather about 1/2" wide and maybe 3" long to wrap around the stuck knob. I put powdered rosin on it first, then slipped a metal radiator hose clamp over it (available from auto parts stores) and tightened it real tight, The clamp has a hex/slotted screw head used to tighten the clamp. With the clamp as tight as I could get it, I used a screwdriver and a hammer to tap the clamp screw head sharply and break the knob loose. It worked great.

I'm in Fredericksburg, Virginia