To sort bobbins I test run them on machines. You don't have to fill them with thread, just pop them on the winder (checks the shaft hole), then engage the little peg (checks the depth of the notch), then watch as they rotate (checks for run out). That's all it takes.
As for getting new Class 15 bobbins, the last ones I bought from Sew-Classic were the metal ones and they've been good. I haven't bought any in a long while but I have enough for us.
Most of our machines use the Class 66 bobbins and the metal ones I've gotten from Sew-Classic have been wonderful.
I also dislike plastic bobbins of any type, although I do use them if handy and already filled with thread. We usually keep them around for the machines that are supposed to use them.
As for getting rid of bobbins with machines that are re-homed, I give out two usually. Or if the machine came with a complete set of attachments and had it's original bobbins I send those out with it.
As for quality control, there isn't any. Especially if the product is made in China.
Joe
Last edited by J Miller; 11-11-2014 at 06:22 AM.