Why is my sewing machine knotting up underneath?
A: Looping on the underside, or back of the fabric, means the top tension is too loose compared to the bobbin tension, so the bobbin thread is pulling too much top thread underneath. By tightening the top tension, the loops will stop, but the added tension may cause breakage, especially with sensitive threads.
How do you fix bobbin tension?
Bobbin tension or bottom tension is fixed by adjusting a small screw next to your bobbin case’s thread opening.To adjust, use a tiny screwdriver and turn the tiny screw to the right for tighter tension or the left to loosen bobbin tension.
If your thread is pulled tight on the underside and not forming an even stitch then (counter-intuitively) it’s usually the top thread tension that’s wrong. Sometimes very lightweight fabrics such as sheers can get dragged down into the machine so it’s a good idea to use a straight stitch plate.