1) Check Cutter Sharpness Place a single strand of thread between the two blades. Turn the Handwheel by hand, and see if the thread is cut cleanly. If the thread is not cut cleanly, adjust, sharpen, or replace the Cutters. .
2) Feed Dogs Set too Low The Feed Dogs should be set so that the bottom point of the Feed Dog tooth is even with the top of the Needle Plate when the Feed Dogs are at their highest point of travel.
3) Too Little Presser Foot Pressure Loosen the lock screw, and turn the adjustment screw clockwise a few turns. Retighten the Lock Screw.
4) Feed Dogs Worn The points on the Feed Dog teeth are no longer sharp. They appear shiny and polished over. Replace the worn part.
5) Presser Foot Worn The Presser Foot has channels or railroad-like tracks worn into its bottom surface. Replace the worn part.
6) Feed Dog Tilt On certain fabrics it may be desirable to tilt the Feed Mechanism.