It might just be jammed tight by someone strong arming it. Maybe try a jar opener or a glove so you can get a better grip. If that doesn't work a large pair of pliers and some leather to protect the knob should do it. The other possibility is it's already turned but not disengaging the machine. If that's the case back out the little screw in the knob, turn the knob counter clockwise until it comes off and take the wheel off. Clean and oil everything and re-assemble.
I hope this helps,
Rodney
Last edited by Rodney; 12-20-2014 at 07:43 PM.
Reason: fat fingered typist