Sergers

Coverstitch vs. Overlock

Coverstitch vs overlock trips up a lot of beginners. These two stitches do most of the work on knit clothes, and people often mention them together. Some sewing groups use the terms loosely, as if they meant the same thing.

They don't. They are two different techniques, done on two different machines. Once you see the difference, a lot of the confusion goes away.

Coverstitch vs overlock: two different jobs

People mention overlock and coverstitch together because some combo machines do both. But they solve different problems:

• Overlock trims a raw fabric edge and wraps thread around it so it can't fray, used on seam allowances.
• Coverstitch stitches a folded edge (a hem) flat with a stretchy, parallel-row finish, used on hems, not raw seam allowances.

Most knit clothes use both. Overlock stitches hold the seams together. A coverstitch finishes the hem. The two work as a team, not as rivals. That is why combo machines exist, and why so many garment sewists end up wanting both.

Coverstitch vs overlock, side by side

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How they work together on a real garment

A knit t-shirt shows how the two stitches split the work. The shoulder seams, side seams and sleeves are usually overlocked. That joins the pieces and finishes the raw edge in one pass. Then the bottom hem and sleeve cuffs get a coverstitch.

The raw edge folds under, and a stretchy stitch holds it flat as the wearer moves. You can use an overlock stitch on a hem instead. But the result is bulkier and less flexible than a true coverstitch hem.

A closer look at how each stitch handles stretch

Both stitches stretch with knit fabric, but in different ways. An overlock stitch gets its stretch from the loops of thread that wrap the edge. That gives the seam some give without much stretch in the fabric itself. A coverstitch gets its stretch from the looper thread that locks under the rows of needle stitches.

That thread stretches and springs back as the hem flexes. Because they work so differently, swapping one for the other's job gives a worse result. An overlock on a hem, or a coverstitch on a seam edge, won't look or wear as well.

What each stitch looks like from the outside

An overlocked edge hides inside the finished piece. It sits in the seam, where no one is meant to see it. A coverstitch is the opposite.

It shows on the outside of the hem as two or three neat rows of stitches. That is why coverstitch machines offer needle spacing choices, and why some sewists pick decorative thread for them. On a coverstitch, the stitch is part of the look, not just part of the build.

Learning both stitches as a beginner

If both stitches are new to you, learn them one at a time. Overlock is the more useful skill at first. You finish seams in almost every garment, whatever the fabric. Coverstitch is a narrower skill, used mainly to hem knits.

A common path is to get at ease with threading a serger and setting its tension first. Then add coverstitch once you make knit clothes often. That way you are not learning two new machines and two new stitches at the same time.

Why patterns specify one, the other, or both

A pattern's steps usually tell you which stitch to use, even when they don't name it. "Finish the seam allowance" or "overlock the raw edges" means overlock. "Hem using a twin needle or coverstitch" means coverstitch.

If the pattern names no finish, use overlock, or a sewing machine's stand-in, on seam edges. Use a coverstitch or twin needle on a knit hem. A plain straight stitch on a stretchy hem tends to pop when you wear it.

Buying decision

If you are choosing one machine to start, a plain overlock serger covers more day-to-day sewing. It finishes any seam on any fabric that frays or stretches. See What Is a Serger? for that case. See Coverstitch Machine for when it is worth adding hems, with a combo machine or a second machine.

Most sewists don't regret starting with overlock only and adding coverstitch later. A twin-needle hem on a sewing machine works fine for a while. But with no way to finish edges, you feel the gap on almost every project.