Very unfortunate with the facy Juki. That's one advantage with most vintage machines, get the hand wheel and clutch screw to turn smootly and it should not be much of a problem. Separate winders can be fast though, and less strain on the machine.

I don't buy pre wounds. For my embroidery machines they're about $25 a box. I buy a large cone of bobbin thread for $8 and can wind a lot of bobbins. I wind 10-20 at a time, it doesn't take that long because the winder on my machines are fast. I do have a separate winder for my long arm but it's for a size M bobbin so none of my other bobbins will fit it.

Cari