When working with stretch fabrics, the stitches also have to be elastic. If you use a regular straight stitch, the seam might easily break, as it won't handle the pull of the garment.
Different sewing machines offer different stitches for stretch fabric. These are a few of the stitches you might find on your household machine.
Triple straight stitch (1) looks like a thicker version of regular straight seam. It is elastic because the needle goes back and forth while stitching one stitch three times, which also makes the seam very strong. It's a good choice for sewing hems and on tight stretch garments.
Zigzag (2 and 3) stitch is available on most household machines and it is a safe choice for most elastic fabrics, as you can adjust the width and sometimes the length of the stitches. It is suitable for finishing raw edges, but can also be used for hems and attaching elastic bands. However, it is not as strong as the three-step zigzag.
Three-step zigzag (4) stitch might look like a regular zigzag at first glance, but each diagonal stitch consists of three tiny straight stitches in a row. This makes it a strong zigzag stitch. It is flatter than a regular zigzag stitch, as it doesn't get the "tunnel-effect" that the regular zigzag stitch might cause when it moves from side to side, pulling the fabric together.
Triple zigzag (5 ) might be confused with a three-step zigzag. It is a triple version of a regular zigzag, but it is much stronger.
Lightening stitch (6) is a narrow and long version of zigzag stitches, and can function as an elastic straight stitch.
Overlock/overedge stitch (7) is a combination of a straight stitch and zigzag stitch in one stitch. That means that you can sew two pieces of fabric together and finish the raw edges at the same time, as you can with a serger. Some machines have an overlock foot that makes it easier to get a neat finish, but it is possible to get a good result without it as well.
Twin needle is a double needle that can be used on most sewing machines. It sews an elastic seam that gives any garment a nice finish, with two parallel straight seams on the right side, and a zigzag seam on the back side. To thread the needles, use two threads and thread them through the machine as usual, as if they were one. Separate them before threading them into the needles, one thread in each needle. Choose a regular straight stitch when you are sewing with a twin needle. A wider seam (ie zigzag) might cause the needles to break, as the seam will be twice as wide with two needles.
Ballpoint needle or jersey needle is a sewing machine needle specialized to sew knitted fabric. The difference between a ballpoint needle and a regular needle, is that the ballpoint needle has a more rounded point that separates the threads of the fabric instead of cutting it, as a sharper needle would.
Clear elastic can be used to stabilize the seams and to create shape. When working with heavy-weight jersey with a lot of drape or stretch (ie rayon/viscose), the seams might easily pull downwards. By placing a clear elastic band on the fabric while sewing, the seams will withstand more pulling and use.
When you work with stretchy fabrics, it is important not to pull the fabric as you sew, as the seam will look wavy and slightly expanded when it's finished. Rather "feed" the fabric towards the pressing foot. On some machines, it is possible to adjust the tension of the pressing foot. A lighter pressure might help.
Sew in stretch
When working with stretch fabrics, it is important that the seams are also elastic. If you use a regular straight stitch on an elastic garment, the seams may break when you take the garment on and off or move around in it.
Different sewing machines have different stretch stitches. These are some of the most common stretch stitches you will find on a normal sewing machine.
Three step straight stitch (1) looks like a thicker version of regular straight stitch. It is elastic because the needle goes back and forth and sews each stitch three times. It also means that the seam can withstand a lot. Triple straight stitching is well suited to visible seams, such as lining up the bottom of a garment. It is also great to use for tight stretch garments that stretch a lot.
Zigzag stitch (2 and 3) is available on the vast majority of sewing machines and is a safe choice for most elastic fabrics, as it is mostly possible to adjust the width, and sometimes the length, of the stitches. It can be used to throw over raw edges, for decorative seams for a set-up edge or to sew tight knitwear. Although the zigzag stitch is flexible, it is not as strong as three-stitch zigzag.
Multi-stitch zigzag stitch (4) may look like a regular zigzag stitch at first glance. The difference is that each diagonal line consists of three small straight stitches in a row. This makes it stronger, but also flatter. Regular zigzag stitches can pull the fabric together and create a small tunnel as the needle moves from side to side. This is avoided by using three-stitch zigzag. It is a versatile seam, which is widely used for underwear, among other things.
Triple zigzag stitch (5) can be confused with multi-stitch zigzag stitch, but is not as widely used. It is a triple version of the regular zigzag stitch and is therefore extra strong.
Extra elastic stitch (6) is actually a long and narrow variant of zigzag stitch. It is used as an elastic straight stitch.
Overlock stitch (7) is a straight stitch and zigzag stitch in one stitch. This means that you sew the fabrics together and cast over the edge of the fabric at the same time, as on an overlock machine. It comes with a separate overlock foot for some machines. It can be a nice aid, but is absolutely not necessary to achieve a good result.
A twin needle is a double sewing machine needle that sews two completely parallel seams. This is called a twin seam, which is a neat finish to garments in elastic fabrics. When sewing a twin stitch, you need two spools of thread for the upper thread. Thread the machine in the same way as usual, but with both threads at the same time, one thread in each needle. When you sew a regular straight stitch with the twin needle, you will get two straight stitches on the right side of the garment, and the bobbin thread will zigzag between the two threads on the wrong side. This makes the seam elastic.
A ballpoint or jersey needle is a sewing machine needle that is specially designed for sewing in knitted fabrics. The needle has a rounded tip, which means that it does not cut across the threads in the fabric, as a normal sewing machine needle can do, but rather pushes them out to the sides.
Angel knit is a narrow, transparent knit that is used to stabilize or give shape to elastic seams. When working with a heavy stretch fabric (eg viscose) the seams can easily be stretched out of shape when sewing or when the garment is in use. If you put an elastic band together with the fabric while sewing, the elastic band will make the seams more solid. It can also be used to create wrinkles, if you stretch the elastic slightly while sewing.
When sewing in elastic fabrics, it is important not to stretch the fabric while sewing. The seam will then curl and expand. Instead, try to "feed" the fabric towards the presser foot. On some machines it is possible to reduce the pressure on the presser foot, but very many machines lack that function. Now that you sew with a lighter pressure on the presser foot, the fabric will slide through more easily without stretching too much.