This is difficult. Try a fresh bobbin. New needle, in correctly, sometimes mine is backwards! Rethread the machine. Make sure the walking foot is installed correctly, with the little arm over the screw thing. LOWER YOUR PRESSURE FOOT. Take a deep breath, and go slowly. And if that doesn't work, hand tie the dern thing and try again on something when you have lots of time. Most of my problems come when I try to rush things.! :?