We may have found other answers which could help you.
Click here for Sewing Machine Needle Threadhow to get the tension right on my machine?
Presser foot is loose?
Singer zigzag 457 Stylist not threading bobbin/making stitch?
Need a service manual for a Singer Treadle Sewing Machine Model 66-1?
Singer 507?
My CG 500/550 Singer Sewing Machine's bobbin isn't working?