My friend's FTN lost its wind crank (how?!?) while in my possession. I'm now tasked with acquiring a new one, and I'm having great trouble finding a source. Buying a whole new FTN is out of the question, but any crank that fits is acceptable.
If the rewind "cap" loosens on the rewind shaft, tension goes off the spring that holds the rewind crank in place in the "cap". Put a strip of wood (or something) through the slot in the inner end of the rewind shaft to loosen/tighten the shaft in the "cap".
Because very few have the tools and skills to do it properly. I just spent two evenings doing a complete CLA on a Pentax H1a, dividing the time it took into $105 means I 'paid" myself around $18/Hr for the work. I wouldn't hire myself out for this type of work for thrice that amount, and the camera isn't worth it.