I agree with Country quilter. I used to work at a shop that ad a repairmen come in once every other week. It was my job to check all machines before he came in. Heres' what I did (at least half the machines coming in for repair just needed one of these thing) Change the needle even if it's new (they bend easily especially with the knots of tread), try a diff. bobbin making sure you wound it correctly and have it in bobbin case correctly. Rethread the machine. Clean underneath as already said, also clean inside of te bobbin case it may have a lint build-up. good luck marie