Sewing with Knit and Jersey Fabrics, A Beginner's Guide

Knit fabric is where a lot of new sewists hit a wall. You’ve made a couple of cotton skirts, you feel confident, and then you buy a lovely soft jersey to make a t-shirt, and the machine eats it, skips stitches, and leaves a hem so wavy it looks like the sea. You start to wonder if you need an expensive overlocker just to make a basic top.

You don’t. You can sew beautiful knit garments on an ordinary sewing machine once you understand why knits behave differently and make a few small changes. I made jersey tops for years before I owned an overlocker, and most of my everyday wardrobe still comes off a regular machine.

Why knits are different from wovens

A woven fabric (like cotton poplin or linen) is made of threads crossing at right angles. It doesn’t stretch much, and it frays at a cut edge. A knit fabric is made of loops of yarn, like a hand-knitted jumper but much finer. Those loops let it stretch, and they mean it doesn’t fray, because there are no cut threads to unravel sideways.

This changes two things. First, your seams need to stretch, or they’ll snap the first time you pull the garment over your head. A normal straight stitch has no give, so it pops. Second, because knits don’t fray, you don’t have to finish raw edges the way you do with wovens, which is actually less work, once you stop fighting it.

The needle is the first fix

Ninety percent of skipped stitches on knits come down to the wrong needle. A standard sharp needle pierces through the loops of a knit and can split the yarn, causing little holes and missed stitches. You need a ballpoint or jersey needle, its rounded tip slips between the loops instead of through them.

For very stretchy or slippery fabrics like activewear, a stretch needle goes one step further with a specially shaped scarf that helps the machine form each stitch reliably. If you take one thing from this guide: buy a packet of jersey needles before you buy anything else. They cost a couple of pounds and solve most knit problems instantly.

Stitches that stretch (on a normal machine)

You have a few options, and you don’t need anything fancy:

• The narrow zigzag: the simplest stretch seam. Set a short, narrow zigzag (width around 0.5–1mm, length around 2.5mm). Because the stitch zigzags slightly side to side, it can open out when the seam is stretched, so the thread doesn’t snap. This works on every machine ever made.
• The lightning stitch: many modern machines have a stitch that looks like a stretched-out lightning bolt or a wobbly straight line. It’s purpose-built for knit seams and looks almost like a straight stitch from the right side. If your machine has it, use it.
• The triple stretch stitch: the machine sews forward-back-forward over each stitch. Very strong, good for crotch and shoulder seams that take strain, but it’s slow and hard to unpick, so save it for seams that matter.

Avoid a plain straight stitch on any seam that needs to stretch. The only place a straight stitch belongs on a knit is somewhere that won’t be stretched, like attaching a label.

Stopping the wavy hem

The wavy, rippled hem is the classic knit problem, and it’s caused by the fabric stretching as it feeds under the presser foot. The fabric goes in slightly stretched, gets stitched, and then relaxes back, leaving the stitching too long for the fabric, which ripples.

Fixes, roughly in order of how much they help:

• Don’t pull the fabric. Let the feed dogs move it. Guide it gently and that’s all.
• Use a walking foot. This attachment feeds the top layer at the same rate as the bottom, which stops stretching better than anything else. If you sew a lot of knits, it’s the best £20 you’ll spend.
• Stabilise the hem. A strip of fusible knit stabiliser (or a product like Vilene Bias Tape) ironed onto the hem allowance before sewing keeps it from stretching while still allowing a little give.
• Use a twin needle for the hem. A twin needle sews two parallel lines on top with a zigzag of bobbin thread underneath, which keeps the stretch. It gives that professional double-stitched t-shirt hem and looks shop-bought.

Cutting and handling knit fabric

Knits move around while you cut, which makes accuracy harder. A few habits help:

• Let the fabric rest flat before cutting. If it’s been folded on a bolt, the stretch can be uneven. Lay it out and let it relax for an hour.
• Cut on a single layer if it’s very stretchy, so the top layer doesn’t shift against the bottom one.
• Use pattern weights and a rotary cutter rather than dragging fabric onto pins. Pins distort stretchy fabric.
• Note the direction of greatest stretch. On most garments the most stretch should go around the body, not up and down. Patterns will tell you which way to lay the pieces.

Pressing, not ironing

Press knit seams gently with the iron lifted up and down, rather than dragging it across, which can stretch the fabric out of shape. Use a medium heat and check a scrap first, synthetic jerseys can melt or go shiny under a hot iron. A press cloth between the iron and the fabric is cheap insurance.

A good first knit project

Don’t start with slinky activewear. Start with a medium-weight cotton jersey. It has a stable, slightly grippy surface that’s far more forgiving than a thin viscose or a four-way stretch sports knit. A simple t-shirt or a relaxed dress with a stretchy cotton-elastane jersey will teach you everything without punishing every mistake.

Once you’ve made one top that doesn’t ripple and doesn’t pop at the shoulder, knits stop being scary and start being the fastest, comfiest things you can sew. There’s no fraying to finish, no buttonholes, and often no zip, a jersey dress can be a two-hour make.

Different, not harder

Knits aren’t harder than wovens, they’re just different, and almost every problem traces back to two things: the wrong needle and pulling the fabric. Fit a jersey needle, pick a stitch with stretch in it, keep your hands off the fabric, and you’ll wonder why you ever needed convincing. An overlocker makes knits faster and tidier, but it has never been the thing standing between you and a good t-shirt.