17 Tension – what is it and what to do when it’s off

What affects tension?

Tension is how the top and bobbin thread interact with each other. Tension is perfect when the top and the underneath of the stitching looks identical and the fabric and stitching feel the same.

If your tension is off you may see loops at either side of the fabric, you may get knots under your fabric, the thread may snap or your fabric may appear to gather.

Tension on modern machines should be on 4 ish and you should not really have to adjust this usually. If it suddenly goes weird follow the sequence below to identify what may have happened.

Needle	Tension will go shonky if your needle is blunt or damaged. Changing the needle will fix this! Incorrectly inserted needles or needles that aren’t high quality or sharp are the number one cause of “bad” tension. Use a good quality needle, insert it with the flat bit to the back of th machine and insert it all the wy as far up as it will go.
Thread	Thicker than normal thread may well see you needing to adjust the tension (down, from say 4 to 2), rough thread such as metallic thread will need a similar adjustment. Most threads won’t need a tension adjustment though.
Threading up	Is your bobbin threaded up properly? Is the bobbin damaged? Is your top thread caught somewhere or has it come out of a disc or loop? Are you using the correct bobbin for your machine?
Fabric	Only when fabric is really odd, sticky or stretchy may the tension need to be adjusted. But try using say a microtex needle first
Bobbin tension	After a lot of heavy use your bobbin tension screw may have moved. If nothing you have done has solved the tension issue try the bobbin screw (see video below)