Bobbin Thread Tension Troubleshooting Guide

Bobbin tension problems produce specific, recognizable symptoms — bobbin thread showing on the top surface of the design, or loose, loopy stitching on the underside — and once you learn to recognize these signs, diagnosing a bobbin tension issue rather than a top tension or stabilizer problem becomes much faster.

Bobbin thread visible on top means tension is too loose

If small loops or visible bobbin thread show up on the top surface of the design, the bobbin tension is typically too loose relative to the top thread tension — the bobbin thread isn't being pulled tightly enough into the fabric, letting it show through where it shouldn't.

Puckering or tight underside stitching means bobbin tension is too tight

Excessively tight bobbin tension pulls the top thread too far down into the fabric, which can contribute to puckering and an overly tight-looking underside — this is a less commonly recognized cause of puckering compared to stabilizer or hooping issues, but worth checking if those other causes have been ruled out.

The drop test is a simple, reliable check

Holding the bobbin case by its thread and gently bouncing it (a "drop test") gives a rough physical sense of tension — a properly tensioned bobbin case should descend slowly and steadily under a small tug, not fall freely (too loose) or barely move at all (too tight). This simple check is faster than guessing from stitched results alone.

Adjust in small increments and retest

Bobbin tension adjustments are typically small, incremental turns of a tension screw on the bobbin case, and overcorrecting in one large adjustment often overshoots into the opposite problem — small adjustments followed by a test stitch, repeated as needed, gets to the correct tension more reliably than one large guess.

Keep a dedicated, correctly-tensioned bobbin case if possible

Some shops keep one bobbin case tensioned and set aside specifically for a particular common thread and fabric combination, avoiding the need to constantly re-tension the same case for different jobs — this small habit reduces how often tension drifts out of adjustment from repeated changes.