Sergers

Coverstitch, Explained

Have you wondered why a home-sewn knit hem looks different from a store-bought one, even when the seam itself is clean? The coverstitch is usually the missing piece.

What a coverstitch actually is

A coverstitch is a hemming stitch for stretchy fabric. You see two or three parallel rows of stitches on the right side. Underneath, a wider zigzag joins them, so the hem stretches with the fabric instead of popping. You will find it on the hem of nearly every store-bought t-shirt. Once you know what to look for, you will spot it on almost all knit clothing in shops.

What it's for

You use a coverstitch to hem and to sew flat seams. You don't use it for the main seams of a garment, or to finish raw edges the way an overlock stitch does. It is the last step, and it works on a folded edge, the hem, not a raw one. Some sewists also use it on flat sportswear seams, or to topstitch the binding on a knit neckline. The stitch stretches and lies flat, so it suits those jobs too.

Coverstitch machine vs. serger

Two kinds of machine make a coverstitch: a coverstitch-only machine or a combo serger and coverstitch machine. A standard 3 and 4-thread serger with no coverstitch mode can't make it. See Coverstitch Machine for what a coverstitch-only machine offers. See Coverstitch vs. Overlock for how the two stitches and machines differ.

What the stitch looks like on the wrong side

Flip a coverstitched hem over and you will see what gives it stretch. A wide zigzag of looper thread links the two or three needle lines on the front. This pattern lets the hem flex as you wear and wash it without the stitches breaking. That is the main reason a coverstitch beats a straight-stitched hem on knit clothes.

Do you need one

If you mostly sew wovens, you likely won't need a coverstitch machine for a while. Quilts, home decor and most beginner patterns fall in that group. The twin-needle or stretch stitch on a sewing machine gets close enough for the odd knit hem. A coverstitch machine is worth adding once you sew knit clothes often. That is when you want a store-bought hem every time, not a workaround now and then.

How a coverstitch is actually formed

A coverstitch machine uses two or three needles set close together. Each needle carries its own thread. A looper thread underneath zigzags between the needle lines as the fabric feeds through. There is no knife, unlike on a serger, since you have already folded the edge under.

That is also why a coverstitch machine can't finish a raw edge alone. With no blade, it can't trim fabric. It can only stitch through fabric you have already folded and pressed.

Coverstitch on projects beyond hemming

Hemming is the main use, but a coverstitch shows up in a few other spots on knit clothes. You can attach a neckline binding flat instead of folding it inside. You can topstitch a flat seam for a sportswear look. Some patterns also use rows of coverstitch just for looks.

In each case the appeal is the same. You get a flat, neat stitch with several rows that flexes with the fabric. It adds none of the bulk of a folded hem sewn with a straight stitch.

A quick way to check if a garment was coverstitched

Look at any hem on a t-shirt or knit top you own. You will see two parallel lines of stitches on the outside. Stretch the hem gently. It should flex, and no stitches should pop or break.

That flex is the tell. A straight-stitched hem on the same fabric would often pucker or break under that same gentle test. A coverstitch exists to avoid exactly that on knit clothes.