2 things I found when winding bobbins on my 7700: 1) when starting, feed the thread through the small hole on the disc part of the bobbin from inside to outside, then feed it down through the center hole. When you then put it on the winding post, it will be anchored better. Be sure to cut this little tail off after threading. 2) my machine winds better at max speed, with the foot pedal unplugged. NOt sure why that makes a difference, but it seems to. Probably because there are no subtle speed variations that you might get from your foot being unsteady.