Mistakes & fixes

Dots of bobbin-colored thread on the fabric's right side mean top tension is too tight relative to the bobbin, pulling bobbin thread up through the fabric. Loosen the top tension and test on a scrap.

Skipped stitches on a coverstitch hem, especially at the seam start, usually come from an unstabilized layer or fabric not feeding evenly under both needles. Use a stabilizer strip and start on a fabric leader.

Visible loops sitting proud of the seam point to unbalanced tension, most often a bobbin thread with too little resistance. Rethread top and bobbin, adjust tension gradually, and test on scrap first.

Stitches that sit slack and don't lock into the fabric come from top tension set too low. Increase the top tension gradually and test until stitches lock in the middle of the fabric.

A seam that gathers or ripples along its length is caused by tension set too tight, a stitch length wrong for the fabric, or sewing fine fabric without stabilizing. Loosen tension and stabilize lightweight fabrics.

Loose loops hanging off a serged edge, or an edge that curls and puckers, points to the tension dials being out of balance for the thread and fabric. Adjust one dial at a time on a scrap.

The bobbin thread breaking mid-seam, leaving only top stitches, often means the bobbin was wound unevenly, inserted backward, or lint has jammed the case. Rewind the bobbin evenly, reinsert correctly, and clean the case.

Thread that snaps repeatedly while sewing is usually old or low-quality thread, a burred needle eye, or tension set too tight for the thread weight. Use fresh quality thread, replace the needle, and ease the tension.

A tangled clump of thread on the fabric underside, jamming the feed, comes from unbalanced tension or starting a seam without holding the thread tails. Rethread fully, check tension, and hold tails taut when starting.

Thread fraying into fuzz or snapping into short pieces usually means it's catching on a burred needle eye or thread guide, or is old and brittle. Replace the needle, check guides for nicks, use fresh thread.

Stitches that pucker the fabric or feel stiff usually mean tension is set too high, pulling both threads too taut. Lower the top tension and check the bobbin isn't wound too firmly.

Loops of top-color thread on the fabric's wrong side signal top tension that's too loose, or a bobbin wound or threaded incorrectly. Tighten the top tension and rewind the bobbin evenly.

A raised ridge forming along a line of stitching on stretch fabric happens when tension is too tight or the stitch is too dense for the fabric's give. Loosen tension and use a walking foot with a stabilizer.

Stitches that vary in size along a seam usually come from inconsistent feeding, a dull needle snagging the weave, or pulling fabric by hand instead of letting the feed dogs work. Let the machine feed naturally.