FW takes a certain bobbin. It looks almost like the average meatl bobbin but it isn't the same at all. It is flatter and thinner. Also the featherweight sews better with the Singer needles. Singer needles are a teeny tiny bit longer from what I have read about them. Also the thread goes in the needle right to left. The flat of the needle goes to the left. There is a notch under the faceplate that the bobbin case has to be in perfect position to. Really there is not much that can't be fixed on a FW unless it's physically broken. Give the seller a very bad feedback and enjoy your machine, it can be fixed to sew perfectly.