Oh I see you found out about the 66 and the bobbins..... :mrgreen:
Some Model 66's are finicky about what bobbin you use on it and only a Singer brand will work on them. I have at least 5 cases of bobbins that are Singer brand just for that reason. But the way to tell is the bobbin winder, if it will not wind it worth a hoot then it will not like the bobbins.
Billy