Pfaff 645F Owner's Manual - Page 45

5. LOWER THREAD BREAKS • bobbin case threaded incorrectly • bobbin case inserted incorrectly in machine • bobbin wound unevenly • bobbin wound too full • bobbin tension too tight • needle plate hole has sharp edges • bent bobbin • poor quality thread 6. FABRIC PUCKERS • bent or blunt needle • upper thread tension too tight • both upper and lower tensions too tight • using two different sizes or kinds of thread • fabric too sheer or soft (use tissue paper underlay) 7. MACHINE DOES NOT FEED FABRIC • stitch length knob set at 0 • fabric feed on ( ) • presser foot not down completely • thread knotted under fabric 8. BUNCHING OF THREAD UNDER FABRIC • upper and lower threads not drawn back under presser foot • fabric feed on ( ) 9. BOBBIN DOES NOT WIND PROPERLY • incorrect threading for winding • thread guide not properly adjusted • bobbin spindle not positioned correctly • bobbin winder stop not positioned correctly 10. MACHINE RUNS SLUGGISHLY • dirt or lint between teeth of fabric feed • dirt or lint in shuttle • machine needs oiling • stop motion knob not tightened 11. MACHINE WILL NOT SEW • cord not plugged into outlet • cord not plugged into "Motor" socket in cabinet or case • stop motion knob not tightened • motor belt too loose or broken 43 - -