Before adjusting anything: re-thread the machine with the presser foot up, change the needle, and check the bobbin is the right class and wound evenly. Those three fix the large majority of what gets called a tension problem. If the stitch is still unbalanced after that, sew a test seam with contrasting threads and adjust the top tension a half-number at a time. Leave the bobbin case screw alone unless you know why you are turning it — it is the last resort, not the first.
Questions people actually ask
Loops underneath — is that top or bobbin tension?
Top, almost always, and usually because the thread is not seated in the tension discs. Re-thread with the presser foot UP before you adjust anything. Loops on the underside mean the top thread is being pulled through too freely.
What should a balanced stitch look like?
Identical from both sides, with the two threads locking in the middle of the fabric layers. Sew a test seam in contrasting top and bobbin colours — the fault becomes obvious immediately.
Last reviewed 2026-08-11