my machine sews fine for a while but then jams with cotton in the bobbin section and it would seem that the bottom tension is not working. It is an empisal 516 super sewing machine

Jeannie, March 2010

Hello Jeannie,
On the bobbin case there is a large screw, to tighten the thread so it pulls the thread down turn the screw about a quarter of a turn at a time clockwise and test sew, to loosen the thread turn the screw the other way but onbly a quarter of a turn at a time then test sew.
Ken

drivewithken, March 2010