Model 575 FA .. Haven't had it open in a long

Look carefully for thread caught around and under the knob. If you can't get it to turn and find no reason why it won't, you can probably delay fixing it until the next time it's due for its yearly "tuneup" (COA, clean/oil/lubricate) by taking the needle out before you wind a bobbin.

slacken the small stop screw and remove the centre free motion knob. the balance wheel should now be free to turn independent of the shaft. you will have exposed the friction washer. clean all surfaces and relocate the washer with the two locating lugs facing outwards into the two slots in the shaft and refit the knob and screw. if the screw bottoms on the friction washer remove knob and turn the friction through 180 degrees and try it again

That is what was needed...they can bind over years of inactivity

What are you calling a stop motion knob? Are you trying to stop the needle from moving while winding a bobbin?

I would suggest that the machine needs to be serviced to find out why it not responding the way it should.

It is the bit that rotates the bobbin case back and forth in a "shuttle" motion.
It sounds like it would be worth exploring the idea that it is time for a service !!

I could not think of another way then free-motion sewing.
Drop the feed dogs, and put a spring loaded needle on.

There is cluch on the handwheel that connect motion,try to tighen this If negative,There are two small bevel gear (hard PVC )connecting to the upper crankshaft where the handwheel was connected.This transmit motion when motor run, most commonly the vertical rod where one bevel gear was connected maybe broken or viceversa at the upper crankshafting that holding the bevel drive gear is broken try to check this.

Actually you should have a "set screw" in the hand wheel. The set screw is usally locked down tight to keep the hand wheel from spinning freely. I f you can run the machine slowly and hold the hand wheel in one place but the machine continues running, then you do need to replace the "set screw". If you replace it you will find that you can offset some of the machines vibration by where you lock the wheel down. Trial and error is the only way to achive this adjustment, kind of like balancing the tires on your car.

Dear Jim,
I'm sure you have a pair of Channel lock pliers around.Place a fairly thick piece of fabric around the inner knob to keep from scratching it. Grasp it with the pliers while holding the handwheel and turn it to the left. IF you can't hold the wheel to keep it from slipping, place a screwdriver or something else under the needle set screw area, turn the wheel until the set screw is resting against the set screw and then turn the inner knob with the pliers.
sewman7