We may have found other answers which could help you.
Click here for Machine Model PriceSinger zigzag 457 Stylist not threading bobbin/making stitch?
how to get the tension right on my machine?
My CG 500/550 Singer Sewing Machine's bobbin isn't working?
the thread is bunching on underside of fabric it looks like birdnest?
Presser foot is loose?
What size needles can I use for my Singer 39a3?