Sewing Knit Fabric on a Regular Machine Without Popped Seams

The first knit T shirt I sewed looked fine on the table. Then I pulled it over my head and heard three seams pop at once. The fabric was fine and the machine was fine. I had used a straight stitch and a universal needle on a fabric that stretches 50 percent across the grain, and the thread simply had nowhere to go.

Sewing knit fabric on a regular machine is completely doable, and you do not need a serger to get there. You need the right needle, a stitch that can stretch, a little less pressure on the foot and a few habits that stop the fabric from rippling. I have taught these to dozens of beginners, and the same five or six changes fix almost every problem.

Why Knits Behave Differently Under the Needle

Woven fabric is a grid of threads crossing at right angles. Knit fabric is a chain of interlocking loops, more like a sweater in miniature. Those loops let it stretch and recover, but they also slide apart when a sharp needle pushes through, and they stretch out of shape when the feed dogs pull the bottom layer faster than the top.

That gives you three typical problems: skipped stitches, popped seams and wavy, lettuce edged seams. Each one has a specific cause, which means each one has a specific fix.

Pick the Right Needle Before Anything Else

A universal needle has a slightly rounded point that works on many fabrics, but on knits it often pierces a loop instead of slipping between them. The result is skipped stitches or tiny holes along the seam a few washes later.

Ballpoint or jersey needle, size 75/11 or 80/12 for cotton jersey, interlock and most T shirt weights.
Stretch needle, size 75/11 or 90/14 for fabrics with spandex, such as leggings fabric, swimwear and ribbing. Its special eye and scarf help stop skipped stitches on very elastic fabric.
Polyester all purpose thread rather than cotton, because it has a little give of its own.

Change the needle every project or two. A dull ballpoint causes more trouble on knits than a fresh universal does on wovens. If you want a fuller chart, see our guide to choosing the right needle and thread weight for a fabric.

Stitches That Stretch on a Basic Machine

Nearly every home machine made in the last forty years has at least a zigzag, and that is enough. Here is what I set on a typical machine.

Stitch	Width	Length	Best for
Narrow zigzag	0.5 to 1.0 mm	2.5 to 3.0 mm	Side and shoulder seams
Lightning or stretch stitch	Preset	Preset	Seams on fitted garments
Three step zigzag	4.0 to 5.0 mm	1.0 to 1.5 mm	Attaching elastic, finishing edges
Wide zigzag	3.0 to 4.0 mm	2.0 mm	Overcasting raw edges

The narrow zigzag is my default. It looks almost straight from the outside but stretches enough for a T shirt. The lightning stitch is stronger, but it is slow to unpick, so test fit with a narrow zigzag first. Sew a 15 cm sample on a doubled scrap of the actual fabric every time you start a new knit, because two jerseys from the same shop can behave completely differently.

Stopping Wavy Seams

Wavy seams happen when the fabric stretches as it feeds. The fix is to reduce the forces doing the stretching.

Lower the presser foot pressure. If your machine has a dial, turn it down a step or two. Heavy pressure squeezes the knit and drags it.
Use a walking foot if you have one. It feeds the top layer at the same rate as the bottom.
Do not pull or push. Let the feed dogs do the work, and support the fabric behind and in front of the foot so its weight does not hang off the table.
Lengthen the stitch slightly. Going from 2.5 to 3.0 mm often removes a mild ripple on its own.

Steam can rescue a small ripple. Hover the iron over the seam and let it shrink back before pressing, rather than sliding the iron along it.

Where the Usual Advice Goes Wrong

The most common advice I hear is that you cannot sew knits properly without a serger. I disagree. A serger is faster and gives a professional looking finish inside, but knit fabric does not fray, so raw seam allowances are perfectly fine left as they are. Most of my everyday T shirts have a narrow zigzag seam trimmed to 6 mm and nothing else.

The second piece of advice I push back on is to stretch the fabric slightly as you sew, so the seam will stretch later. That builds the ripple right into the garment. Use a stitch that stretches, and leave the fabric relaxed. The only time you stretch while sewing is when you attach a band or elastic that is deliberately shorter than the opening.

Hems, Shoulders and the Finishing Details

Twin needle hems

A twin needle gives two neat rows on the outside and a zigzag underneath that stretches. A 4.0 mm twin stretch needle works well on jersey. If the fabric tunnels into a ridge between the rows, loosen the upper tension a little, or wind the bobbin with a stretchy textured nylon thread.

Stabilize shoulder seams

Shoulders carry the weight of the garment and stretch out over time. Sew a strip of clear elastic or a narrow twill tape into the seam. It keeps the shoulder line in place without stopping the rest of the garment from moving.

Prewash the knit first

Cotton jersey can shrink 5 to 8 percent in length. Wash and dry it the way you will treat the finished garment, as explained in our post on prewashing fabric before sewing.

FAQ

Why does my machine skip stitches only on the stretchiest parts?

Fabrics with spandex flex as the needle goes in, so the hook misses the thread loop. Switch to a stretch needle, slow down, and try a strip of tissue paper under the seam, which tears away after sewing.

Can I use a straight stitch on knits at all?

Yes, for areas that do not need to stretch, such as a pocket or a waistband channel. For anything that goes around the body or over the head, use a stitch that stretches.

My tension looks wrong on knits only. Is the machine faulty?

Almost never. Uneven feeding and the wrong needle cause most of it. Our article on why a sewing machine tension problem is rarely the machine walks through the checks.

Your First Knit Project

Buy one metre of medium weight cotton jersey with about 25 percent stretch, not a slinky spandex blend. Put in a fresh 75/11 ballpoint needle, set a narrow zigzag at 0.8 mm wide and 2.8 mm long, lower the presser foot pressure and sew a few test seams on scraps. Pull each one hard. When the seam stretches without popping and lies flat afterward, you have your settings. Write them on a card and tape it to the machine.