A sewing machine for knits needs three things: adjustable presser foot pressure, a stretch stitch (a narrow zigzag or the lightning stitch) and a walking foot or built-in dual feed. Together they stop the wavy, stretched-out seams that make jersey frustrating. Useful extras are twin-needle capability with a second spool pin for hems, an overcasting stitch with its foot, and a free arm for neckbands and cuffs. You do not need a serger to sew knits well; it makes the work faster, not possible.
| Feature | Why it matters for knits | What to look for |
|---|---|---|
| Presser foot pressure | Too much pressure stretches the top layer as it feeds | A dial or screen setting that goes low |
| Stretch stitch | A straight stitch pops when the seam stretches | Narrow zigzag, lightning stitch or triple straight stitch |
| Walking foot or dual feed | Moves both layers together, no rippling | Accessory walking foot, or built-in dual feed |
| Twin needle | Hems that stretch without a coverstitch | Two spool pins and a zigzag needle plate |
| Overcasting stitch and foot | Seams that stretch and are finished in one pass | Overcasting stitch plus the matching foot |
| Free arm | Neckbands, cuffs and sleeve hems in the round | Removable accessory tray |
| Needle system | Ballpoint and stretch needles in 70/10 to 90/14 | Standard 130/705 H |
Why do knits stretch out on a regular sewing machine?
A knit fabric is a chain of loops rather than crossed threads, so it stretches in every direction. On the machine, the presser foot pushes down on the top layer while the feed dogs pull the bottom layer along. Under enough pressure the top layer is dragged forward and stretched before it reaches the needle. The stitches lock that stretch in, and the seam comes out rippled like a lettuce leaf.
Three things cure it: less pressure on the foot, a foot that feeds the top layer, and sewing without pulling the fabric toward you. The sewing knit fabrics on a regular machine guide walks through the technique; this post is about the machine.
Which stitches do you need for knits?
Four, and most machines with a zigzag have at least two of them:
- Narrow zigzag: 0.5 to 1 mm wide, 2.5 to 3 mm long. It looks almost straight on the right side and stretches with the seam. This is the workhorse for T-shirt side seams and shoulder seams.
- Lightning stitch (stretch stitch): a tiny zigzag with a slanted shape, usually about 1 mm wide. Stronger and flatter than a zigzag, and it unpicks more easily than the triple stitch.
- Triple straight stitch: each stitch is sewn forward, back and forward again. Very strong and very stretchy, but slow, bulky and nearly impossible to unpick. Keep it for crotch seams on leggings.
- Overcasting stitch: a straight line with a zigzag that wraps the edge, sewn with the overcasting foot, which has a small pin the thread wraps around. It stitches and finishes in one pass, like a basic serger seam.
A machine with 200 stitches has no advantage over one with 15 if those four are among them. Decorative stitches are a bonus, not a reason to choose a machine for knits.
Does presser foot pressure matter for jersey?
It is the single most useful feature, and the one most often missing on entry-level machines. A dial on the top left of the head, or a setting on the screen, lets you back the pressure off from its default. On lightweight jersey, dropping it to a third or half of the default removes most of the rippling on its own.
If your machine has a fixed spring, you can still sew knits with a walking foot and a lighter hand, and a layer of tissue paper under the foot on very thin fabrics. But if you are buying a new machine for knits, treat adjustable pressure as non-negotiable.
Walking foot or built-in dual feed?
An accessory walking foot clamps onto the presser bar and has its own set of feed dogs that grip the top layer. It fits almost every machine for a modest price and transforms knit sewing; it also matches stripes and feeds plaid. Its drawbacks are noise, a boxy shape that hides the needle, and the fact that it comes off whenever you need another foot.
Built-in dual feed does the same job with a small arm behind the foot that engages when you need it and folds away when you do not. Pfaff has built it into most of its machines for decades under the IDT name; Janome's AcuFeed and Bernina's dual feed appear on some of their mid-range and high-end models at the time of writing (October 2026). It is a strong reason to choose a given model if you sew knits every week, and a luxury otherwise.
Which needles and thread for stretch fabrics?
A ballpoint (jersey) needle pushes the loops aside instead of cutting them, which prevents the little holes and runs a sharp needle leaves in jersey. Use 70/10 for fine jersey, 80/12 for cotton jersey and French terry, 90/14 for sweatshirt fleece and ponte. For fabrics with elastane such as swim, activewear and anything with more than 20 % spandex, a stretch needle has a deeper scarf that stops skipped stitches.
Polyester all-purpose thread is the right choice: it stretches a little, unlike cotton. For the bobbin on hems, some people use a textured nylon thread that stretches more, but it is optional.
Can you hem knits without a coverstitch machine?
Yes, with a twin needle. Two needles on one shank sew two parallel rows on the right side while the bobbin thread zigzags between them underneath, so the hem stretches. You need a second spool pin (most machines have one in the accessory box) and a needle plate with a wide hole. A 4 mm stretch twin needle in size 75/11 or 90/14 is the usual choice.
The twin needle hem tunnels on some fabrics, where the fabric between the two rows ridges up; lowering the needle tension and backing off the foot pressure fixes most of it. The twin needle vs coverstitch vs zigzag hem post compares the three options.
Do you need a serger for knits?
A serger sews the seam, trims the edge and overcasts it in one pass at high speed, and its differential feed can gather or stretch the fabric deliberately, which eliminates rippling on even the lightest jersey. For someone who makes T-shirts and leggings every week it is a worthwhile second machine. It is not a replacement for the sewing machine: you still need one for hems, topstitching and anything woven. The serger vs sewing machine comparison goes into the details.
Knit patterns usually come with a narrower allowance, 1 cm (3/8 in) rather than 1.5 cm, because the edge is finished within the seam; Sewly's T-shirt and sweatshirt patterns use that 1 cm default on knits and let you change it if you prefer sewing at 1.5 cm and trimming on the serger.
Which should you choose?
- You already own a machine and want to sew T-shirts. Buy a walking foot, a pack of 80/12 ballpoint needles and a 4 mm stretch twin needle. Set a narrow zigzag and lower the foot pressure if you can. That is enough for a first T-shirt.
- You are buying a new machine and knits are a priority. Look for adjustable presser foot pressure, a lightning stitch, an overcasting foot in the box and a free arm. Built-in dual feed is the feature to pay extra for; an automatic thread cutter is not.
- You sew activewear, swimwear or leggings regularly. Add a serger with differential feed, and keep stretch needles in stock. A coverstitch machine for hems comes later, when twin-needle hems stop being good enough.
- You sew mostly wovens with the occasional knit. Do not change machines. A walking foot and the narrow zigzag cover the occasional sweatshirt.
The best machine for knits is often the one you have, with a different foot and needle, and the right stitch selected.