Carol Jean

Change the needle to make sure there is not a bur on it. Rethread your machine all over again making sure it is going into your tension disc. Make sure you clean out where the shuttle, race and bobbin case is. Try different types of threads to see which works the best. My kenmore machines use both kinds. When adjusting the screw on the bobbin case make sure the bobbin is in it and threaded correctly . Pull the thread out about 5 inches then give it a slight jilt. The bobbin case should move down just a iittle but not much. This is how you know you have the screw adjusted correctly on the bobbin case. To loosen adjust screw very little to the left and to tighten adjust to the right very slightly. I keep a lint brush beside my machine and clean out the bobbin area constantly. Always adjust your needle size with the type of fabric along with stitch length. Heavier fabric will require a 3.0 length whereas cotton will require a 2.5 length or a little shorter. Always hold both bobbin and needle thread when starting to sew. Oil the machine pretty often making sure you put a small drop of oil on the race. Good luck.