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Sewing Lesson - How to Sew Curved Seams

Now that you have practiced sewing straight lines on your lunch tote project, it is time to learn how to handle curved seams. They require a bit more attention before and after sewing to ensure that the curved edge is smooth and rounded, but once you learn a few tricks, they are not at all difficult to sew. It is important to learn how to sew nice curves because they are used in many home decor projects as well as in garments.

There are two types of curves: concave and convex (see, geometry does come back to haunt us). If a curve "caves" into the fabric, this is a concave curve. A curve that bulges out away from the main piece of fabric is a convex curve. Both are sewn the same way, the main difference is how the seam allowances are treated after sewing, which we will discuss a bit later.
concave and convex curves

First, it is important to cut your curved edges smoothly and carefully. Curves can be a bit tricky at times to cut because of the angle of the curve, so it often works best to cut a curve half-way from one side and then cut the other half from the other direction.

Rotary cutters also work well for cutting curves because they are easy to rotate as you are cutting without catching on the fabric. I find that the smaller rotary cutter (28 mm) works best.

To follow along with this tutorial, cut two squares of fabric that are 7 1/2 inches. Place one on top of the other and align the edges as shown in the photo. To create the curved edge, use a large plate and place it over the corner so that it intersects the bottom and left edges at about the same distance from the bottom left corner. If you are using a rotary cutter, you can use that to cut around the edge of the plate; if you will be using scissors, use a marking tool to trace around the edge and then cut out.
cut curves

After cutting, your pieces should look like the ones in the photo to the right.

Prepare your machine for sewing by setting it for sewing a straight stitch and find the line on your sewing machine plate that matches your seam allowance (since most garment patterns use a 5/8 inch seam allowance, that is what we are going to use here in our example).
curves cut

Place your fabrics right sides together and match up all of the edges;pin in place. Remember not to pin within the seam allowance to avoid sewing over the pins.

On your first few test pieces, I recommend that you mark the seam allowance on the fabric so that you have a visual guide on the fabric itself instead of having to rely solely on the machine seam guide.

To mark the seam allowance accurately, use a sewing gauge like the one shown here. Move the blue slider to the 5/8 inch line and use it to mark the seam allowance around the curve.
mark seam

Put your matched up fabric pieces under the presser foot at the beginning of the seam so that the edge of the fabric is on the right side of the machine. Put your needle down and backstitch the beginning of the seam to secure it and then begin to sew forward into the curve. Sew slowly and use both hands to move the fabric gently to one side or the other so that you are following the curve with the needle, keeping the seam allowance a consistent width as you sew.

The trick with curved seams is to keep your focus on where the needle is penetrating the fabric because this is where the seam allowance needs to be gauged from (see red line in the photo). Most people tend to look toward the bottom of the sewing machine plate and guide the fabric based on that alignment which does not work with curves because the edge is not straight. If you look at the photo, you can see that the fabric does not line up with the blue line marking the seam allowance in between the needle and the bottom edge of the sewing machine plate. An open toe foot like the one I am using here, can make it easier to see how far the needle is from the edge of the fabric.

Tip: when sewing gentle curves, you can use your hands to move and guide the fabric through the machine, but sharper curves will look better if you stop sewing with the needle down, lift the presser foot, and move the fabric slightly to release the tension and change the angle of approach. When you reach the end of the seam, back stitch to lock it in place.
seam allowance

Click to read about Pressing and Clipping Curved Seams

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This content was written by Tamara Bostwick. If you wish to use this content in any manner, you need written permission. Contact Cheryl Ellex for details.

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