I have sewing machines that use metal bobbins and I have sewing machines that use plastic bobbins. I use metal bobbins in the machines that came with metal bobbins and I use plastic bobbins in the machines that came with plastic bobbins. I do NOT use metal in the machines that came with plastic bobbins and I do not plastic in the machines that came with metal bobbins. I would go back to the metal bobbins if it were me.