A serger sews a seam, trims the edge and wraps it in thread in one pass; it works along the edge of the fabric and is the machine for seams on knits and for finishing seam allowances. A coverstitch machine makes the stitch you see on the hem of every ready-to-wear T-shirt: two or three parallel rows of straight stitching on top and a looper thread zigzagging between them underneath, which stretches, has no knife and can sew anywhere on the fabric. The serger is the one to buy first; a coverstitch is a specialist machine for hemming and topstitching knits that a twin needle on your sewing machine can approximate.
| Feature | Serger (overlocker) | Coverstitch machine |
|---|---|---|
| Main job | Seams on knits; finishing raw edges | Hems and topstitching on knits; binding and elastic |
| Threads | 3 or 4 (needles and two loopers) | 2 to 4 (1–3 needles and one looper) |
| Knife | Yes, trims the edge ahead of the needles | No |
| Where it sews | Along an edge only | Anywhere, including the middle of a piece |
| Top of the stitch | Thread wrapped over the edge | 1, 2 or 3 straight rows of stitching |
| Underside | Looper threads interlocked over the edge | A looper thread covering the gap between rows |
| Can it sew a seam? | Yes, its main purpose | Only a chain stitch with one needle, no overcasting |
| Can it hem? | A rolled hem on the edge | Yes, a flat stretchy hem of the kind on bought knits |
| Price tier | Entry-level upward | Mid-range; rarely sold at the entry level |
What does a serger do?
A serger stitches with one or two needles while two loopers, hooked arms under and above the needle plate, carry thread over the fabric edge that the knife has trimmed. The overlock stitch that results holds the seam, stops fraying and stretches with knits. It is the seam inside your bought T-shirts and the finish on the seam allowances of your bought trousers.
In garment sewing, a serger is used for:
- 4-thread seams on knits: T-shirts, leggings, sweatshirts, knit dresses,
- 3-thread finishing on the seam allowances of wovens, before or after sewing the seam on the sewing machine,
- rolled hems on fine or sheer fabrics,
- gathering, with the differential feed set high, on lightweight fabrics.
It cannot sew a hem in the middle of the fabric, because the knife and the loopers need the edge.
What does a coverstitch machine do?
A coverstitch machine looks like a serger without the knife and the upper looper. One, two or three needles make straight rows on top, and a single looper underneath runs its thread back and forth between the needle threads. Pull the hem and the looper thread zigzags open, so the stitch stretches as far as the fabric does, then recovers. That is why bought knit hems do not pop when you pull a T-shirt over your head, and why a straight stitch on a sewing machine does.
Because there is no knife and the needles are on a flat bed, the coverstitch sews anywhere on the fabric. The typical jobs:
- hems on T-shirts, leggings, sweatshirts and knit dresses, folded up and stitched from the right side with the two needle rows, the looper covering the raw edge underneath,
- topstitching on knit necklines and cuffs,
- attaching elastic, fold-over elastic and knit binding with a binder attachment,
- the chain stitch, with one needle: a stretchy seam used for the inseams of jeans and for basting, since it unravels easily from the end.
The underside of the coverstitch, with its looper thread, is decorative on its own and is often used as the visible side on sportswear.
Can a serger do a coverstitch?
A plain serger cannot. The coverstitch needs the needle threads to form loops below the fabric with no edge to wrap around, which the serger's upper looper and knife prevent. What a serger does for hems is a rolled hem on the edge, or you can use the serger to finish the raw edge and then hem with a twin needle on the sewing machine.
Some machines combine both. Serger/coverstitch combination machines, such as the Juki MO-735, the Brother 2340CV's stablemate combos, the Bernette b48 and the Baby Lock Ovation and Triumph at the time of writing (October 2026), switch between overlock and coverstitch. The switch takes a few minutes on the mechanical ones: disengaging the knife, changing the needle plate or the foot, rethreading. The high-end Baby Lock models change over with less rethreading, at a correspondingly higher price. If you hem knits often, a separate coverstitch machine saves the changeover; if you hem knits once a month, a combo saves space and money.
How does a twin needle compare to a coverstitch?
A twin needle on a regular sewing machine produces two parallel rows on top and a bobbin thread zigzagging between them underneath, which looks like a coverstitch from the right side and stretches somewhat. It costs the price of a needle and takes a second spool of thread. For most home sewists it is enough for T-shirt hems, and the sewing knits guide explains the settings.
The differences:
- Stretch. A twin-needle hem stretches less than a coverstitch, because the bobbin thread is a lockstitch, not a chain. On leggings and fitted cuffs it can snap when stretched hard; on a T-shirt hem it is fine.
- Tunneling. The fabric between the two needle rows can ridge up. Lower the needle thread tension, lengthen the stitch to 3 mm and put a strip of wash-away stabilizer under the hem, and the ridge mostly disappears. A coverstitch does not tunnel when set correctly.
- Appearance. A coverstitch is flatter and more even and covers the raw edge underneath; a twin needle leaves the raw edge showing on the inside unless you serge or zigzag it first.
The hemming knits comparison weighs the three methods on real garments.
Which machines are common at home?
At the time of writing (October 2026), the Brother 2340CV is the long-standing entry to coverstitch machines, with 2- and 3-needle coverstitch and a chain stitch. The Janome CoverPro 1000CPX and 2000CPX, with their larger flat bed and free arm, are the most often recommended dedicated coverstitch machines, and the Juki MCS-1500 and the Bernette b42 sit alongside them. All are mid-range machines; none is as cheap as an entry-level serger. Their binder and hemming attachments are sold separately and are what make the machine fast to use.
Which should you choose?
- You own a sewing machine and sew some knits: a serger first. It makes the seams and finishes the edges; a twin needle on your sewing machine does the hems.
- You sew wovens and almost no knits: a serger, if anything. A coverstitch machine has little to do on woven garments beyond decorative topstitching and the chain stitch.
- You sew a lot of knits and want hems that look bought: a serger and a coverstitch, as two machines if you have the room, or a combination machine if you do not.
- You sew activewear, swimwear or children's clothes in knits: the coverstitch earns its place for binding, elastic and hems; buy it after the serger, before a fancier sewing machine.
- You want one machine for everything knit: a combination machine, accepting the changeover time.
A fitted T-shirt from the T-shirt pattern is a good test of the setup: serge the shoulders, sleeves and sides with a 4-thread overlock, then hem the sleeves and body with a twin needle or a coverstitch and compare the results.