x2 on the patience aspect. I bought a Florence Treadle (posts later) that had the bobbin winder so gunked up nothing would move.
Kriol, tap gently, wait a day, Kriol, wiggle a little, wait a day, Kriol, wiggle a lot, wait a day, Kriol, Spun free!!! now that it has released, I am in the process of getting out the residual rust that was not binding it.