I have a Pfaff... and it will not even on pain of death... work with invisible thread in the bobbin....so it may be your thread....or your needle... you need to match the correct type and size of needle to your thread. If you sew 50, 60 weight thread...an 80 (Size 12) will work fine. If you use heavier weight thread... 40, 30,... you will need a larger needle... a 90 or even 100. If you have 60 weight in both top and bobbin..you can use a 70 needle. Hope this helps... and good luck. :mrgreen: :lol: :mrgreen: