Originally Posted by Kathie S.
The plastic is so light that it unwinds differently (beacuse of FYI: The metal bobbins don't work n the plastic machines either. Don't ask how I know that.
Just to add to this conversation. I've had great luck in finding ebay auctions for very little... that have boxes of bobbins/parts.
On the 66 class metal bobbins here's what I have personally noticed. I have my grandmother's 66-6 with all her bits, including the original bobbins. I also have several batches of 66 class bobbins that I've either bought or found at garage sales. I've found that if I hold the bobbin horizontally and look at the edges of the flanges... the older bobbins are slightly rounded towards the thread channel. The newer (like ones from Joanne's) 66 metal bobbins at first glance look the same. But if you hold them up the same way and look... they are straight or straighter flanges. My 66-6 is super finicky. "Billie" (my grandmother's use name) only likes the old bobbins and will not sew a clean stitch without the old ones. Now maybe this is just me? Maybe not. Anyone else notice the tiny difference in flange edges?
P.S. I've heard over and over again: use plastic bobbins in plastic machine/plastic bobbin cases. Use metal bobbins in all metal machines/metal bobbin cases. You don't want metal and plastic constantly rubbing each other. The hard metal will wear the surface of the plastic. So don't use a metal bobbin in a plastic bobbin race, or you'll eventually wear out the race and have to replace it. Etc...