Why is my thread bunching 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 tighten thread tension?
Changing Bobbin Tension
You should see a small screw on the flat/closed side of the bobbin case. Turning the screw a tiny bit counterclockwise will loosen the bobbin tension; turning it clockwise will tighten the tension.
What is the normal tension for a Singer sewing machine?
The target figure should be around 30 to 40g. (1-1/4 to 1-1/2 oz) but it does not have to be too precise. However most people don’t have a spring balance handy, so alternatively you can tie a weight of the correct amount onto the thread and then jerk the bobbin gently upwards.
What tension should I use for thin fabric?
Use size 70/10 for really thin cotton like voile, size 80/12 for light to medium weight cotton, and 90/14 for thick cotton like denim.