Perfect curved hems on knit garments

Curved hems on tops and dresses are fun to wear. Convex curves at the back provide more modesty, while concave curves at the sides make the leg look longer.

Curved hem on the Mimosa t-shirt (Jalie 3890)

As much as people love them, hemming a curve can be intimidating for some and we have often read about people deciding to cut the fabric straight across instead, sacrificing design to make hemming easier.

Jalie 3245 tunic in kids size

Today, we will show you how to make perfect curved hems using your differential dial, which is a feature on every Janome serger and Cover-Hem machine. It is an adjustment setting that many overlook but one which can make a huge difference in how easy (or difficult) your curved edge will be to hem.

Jalie 3352 dolman top in adult size

What makes a curved edge difficult to hem?

For those of you who remember their math classes, you will remember that the greater the radius, the greater the circumference. In garment making, this means that the outer edge (the raw edge) will always be longer; always be bigger than the inner edge (the hem fold line).

Convex (outward) curve – the raw edge creates ripples when you fold it to the wrong side.
Concave (inward) curve – the raw edge is shorter, which makes it difficult to press flat.
  • The wider the hem, the bigger the difference.
    That is why facings are often used to finished wide curved hems. Anything narrower than 2 cm (3/4”) can be easily hemmed, no problem.
  • The sharper the curve, the greater the difference too.
    If hemming curves is a challenge for you, look for softer curves at the beginning.
  • Convex (outward) curve = the raw edge is longer than the fold.
    When pressing your hem, you end up with extra fabric and ripples that are difficult to keep flat.
  • Concave (inward) curve = the raw edge is shorter than the fold.
    When pressing your hem, the raw edge stretches out and can distorts the hem.

How the differential feed can help

The differential feed dial on your serger can either gather the fabric or stretch it out. This means that it allows you to control the length of your raw edge. See where I’m going with the idea? 🙂

Serging the edge using various differential settings makes pressing a curved hem to the wrong side much easier.

On a convex curve, you want to shorten the outer curve. This means that you need to turn up the dial to “gather” slightly. Not to the point that your fabric looks like a shower cap though, lol! You want to turn the dial up to a higher number just enough to make the edge curl up a bit. For the example above, we turned the differential feed dial to 1.75 (between 1.5 and 2). The standard is 1.0.

On the Janome AT2000D Air Thread serger, the Stitch Length dial and Differential Feed Dial are integrated but adjust separately. The Differential Feed dial is the smaller outer dial. Other Janome sergers have separate dials for each function, so all Janome sergers can be adjusted in the same manner.

On a concave curve (think sides of a dress shirt for example), you want to lengthen the outer curve. Turn down the dial so that the edges stretch a bit.

After the raw edge is serged, press your hem to the wrong side of the fabric at the width indicated in the pattern instructions. No more pinching/pleats! Everything presses nicely in shape, and you are ready to topstitch.

Now that you’re a pro at stitching curved hems, our most popular patterns with curved hems are:

Special thanks to Brightside Fabric Co for sponsoring the fabric for this post.

Janome Canada Artisan Jalie Patterns
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