Basics

Sewing curves together: line on line, not edge on edge

An outward and an inward curve never match at the cut edge. What matters is the stitching line. Here's how to sew curves together without little tucks.

Top: an outward-curved and an inward-curved piece with a dashed stitching line. Below, the lines straightened out: both stitching lines are the same length, the cut edges are not

Some seams join two edges that curve in opposite directions: one outwards (convex), one inwards (concave). On the Liv shorty that's the gusset, and the same goes for sleeve caps, round pockets and inserts. On trousers like Hanne, the crotch seam joins two edges that curve the same way, but there too it's the stitching line that counts, not the edge. How to put the legs together for it is explained in Sewing trouser legs together.

The typical mistake: you line up the cut edges and wonder why they don't match. Once you understand why, curves become much more relaxed.

What you need

Your cut pieces with all notches and marks
Chalk or a disappearing marker and a ruler
Small, sharp scissors
Fine pins (better than clips here)
For jersey: a jersey needle and a stretch stitch

Step 1

Why the edges aren't the same length

Two pieces that belong together along a curve have stitching lines of the same length. That's how the pattern is drafted. But the seam allowance always sits outside the stitching line:

On the outward curve (convex), the cut edge lies on a bigger arc. It's longer than the stitching line.
On the inward curve (concave), the cut edge lies on a smaller arc. It's shorter.

So if you match edge to edge, it can't fit. If you match line to line, it fits exactly.

Step 2

Transfer stitching lines and match points

An outward- and an inward-curved piece, both with the stitching line drawn in and coloured match points in the same order at the same places

Because the stitching line is what counts, you should be able to see it. Draw it on the wrong side of both pieces with chalk, at least along the curve. To do this, measure the seam allowance from the instructions in from the edge at lots of points and join them up.

Also transfer all match points from the pattern, as a notch in the seam allowance or a dot on the stitching line. They show you which spot belongs to which. If a long curve only has a few points, add your own: lay the paper pieces stitching line on stitching line and put a few extra marks on both at the same places.

Step 3

Relieve the inward-curved allowance

Close-up of the inward curve: a staystitch line in the allowance, straight clips stop just short of the dashed stitching line, on the right the allowance fans open

The concave edge is about to be laid against a longer edge. For that, its seam allowance needs some give:

First sew a staystitch in the seam allowance, 2–3 mm from the stitching line. It stops the edge from stretching out while you handle it.
Then clip into the allowance at right angles, up to just short of that stitching, so 2–3 mm from the stitching line. Never through it.

The allowance now fans out and can be laid against the curved edge. In tight curves place the clips closer together, in gentle ones a few are enough.

Step 4

Pin the match points first, then in between

The inward-curved piece lies wrong side up on the curved piece, the clips have fanned open, pins with yellow heads at the match points and more pins in between

Place the pieces right sides together. At each match point, push a pin exactly through the stitching line of the top layer and check underneath that it comes out on the line there too. Only once all match points are in place do you pin in between, always line on line and fairly close together.

Keep your eyes on the lines, not the edges. The clipped allowance is allowed to fan out.

For sewing, the concave piece goes on top. That way you can see the clips and notice straight away if fabric bunches up anywhere.

Step 5

Sew slowly and pivot

Presser foot on the curve, the needle is down in the fabric, a curved arrow shows the fabric being turned around the needle

Sew slowly and always on the stitching line of the top piece. Pull the pins out just before the presser foot reaches them.

On the curve, sew only a few stitches at a time. Then:

Leave the needle down in the fabric.
Lift the presser foot.
Turn the fabric a little until the line runs straight in front of the foot again. Smooth the bottom layer as you go.
Lower the foot and keep sewing.

Don't pull the fabric or push it along. The machine feeds, you just steer.

Step 6

Check from the right side and press

Left: a curved seam from the right side with a small tuck sewn in, a seam ripper next to it, crossed out. Right: the same seam smooth, ticked

Open the pieces out and look at the seam from the right side. Can you see a little tuck sewn in? Then unpick just that spot, a few centimetres, redistribute the fabric and sew it again. Leave the rest of the seam as it is.

Press the seam allowance towards the convex side, into the outward-curved piece. It usually falls that way on its own, so don't force it the other way. Press with the tip of the iron and only along the seam, so the curve doesn't get distorted.