Originally Posted by joeyoz
You really need to use the bobbins made for your machine. Throw the metal ones out. I learned that lesson the hard way.
Were they the same class bobbin? You do need to use the specific size of bobbin made for your machine as there are subtle differences in shapes and tolerances among bobbin types. In other words, you can't just use a bobbin that looks okay. But I thought plastic and metal bobbins of the same type were interchangeable.