Illustrative situation
A brand’s first T-shirt samples have hems finished with a plain lockstitch. After a few wears the hem threads snap when the shirt is pulled over the head, while the factory’s other samples with a coverstitch hold up.
Main answer
A coverstitch hem has parallel rows of stitching on the top surface and a looper thread underneath, which lets it stretch with knit fabric and lie flat, so it is the standard hem for T-shirts, hoodies and activewear. Check the stitch density, thread type and recovery on the sample, because a plain lockstitch hem will snap when a knit stretches.
What it is
Coverstitch is a chain stitch that uses two or three needles and a looper. In ISO 4915, the 400 class covers multi-thread chain stitches and the 600 class covers covering chain stitches. Machines that sew these stitches are used for hems, necklines and bands on knits. The top shows parallel lines and the back shows a looped chain.
Why knits need it
Knit fabric stretches and recovers. A lockstitch uses two threads that interlock and does not stretch, so the threads break when the hem is pulled. The chain structure of a coverstitch can give with the fabric, and the looper thread underneath spreads the stress. That keeps hems flexible and flat.
Where it is used
Coverstitch is common on hems of T-shirts and sleeves, necklines, waistbands and cuffs, and on activewear seams where flat, stretchy joins are needed. It can also cover seams on the outside as decoration. Two-needle and three-needle versions give different looks and strengths.
Common hem faults
Typical faults are tunnelling between the rows, a wavy hem from stretched feeding, skipped stitches at joins and raw ends at the start and finish. Ask your factory how it controls these, and inspect hems on the first articles from each lot.
What to check
Look at the stitch density, the thread type and tension, since loose tension makes tunnels and tight tension makes puckering. Stretch the hem and see that it recovers. Check the start and finish of the stitching, and the ends of the hem. Ask for pull and wash tests. See T-shirt quality guide and wavy hems.
Fact, recommendation, uncertainty
- Established fact
- ISO 4915 classifies chain stitches, including multi-thread chain stitches in the 400 class and covering chain stitches in the 600 class.
- Recommendation
- Specify a coverstitch for hems on knits, with stitch density, thread and tension, and test stretch and recovery.
- Uncertainty
- Stitch performance depends on thread and machine setup, so inspect actual samples.
Sources and further reading
Sources checked on 24 October 2026. Standards bodies sell the full texts; we cite what their public pages state. General information, not legal or technical certification advice.
More perspectives from the team
Three further views on the same question, each by function. They add conditions and limits to the main answer; they are editorial notes, not customer reviews.
Sino Finetex Editorial Team Sourcing
Ask which coverstitch machines and thread the factory uses on knit hems. Limit: older machines may give uneven results. Ask whether the factory uses a differential feed or a hem guide for knit hems.
Sino Finetex Editorial Team Product selection
Choose a two-needle hem for a clean look and three-needle for a stronger hem. Limit: the extra needle adds cost and visible stitching. Choose a hem width that suits the fabric weight, wider on heavy knits and narrower on light.
Sino Finetex Editorial Team Quality & care
Stretch each hem sample and look for broken threads. Limit: test in the direction the hem is stretched during wear. Pull the hem across and check that no thread shows broken between the rows.
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