If you’ve noticed your stitches are a little, well, off, it’s likely you went straight for the tension. But the truth is there could be a myriad of culprits behind your screwed-up stitches. You could be using an old needle, for starters, or you may even have the wrong one for the job. You could’ve set your machine’s stitch length and width to the wrong setting. Or, like you thought, the machine’s tension may need some tweaking.
If that’s the case, the good news is there’s an easy fix. Every machine has a tension dial, and behind that dial are metal discs. The higher the number, the more pressure the discs place on your thread, meaning less of it is fed into the machine (and vice versa). Most machines have the dial set to “auto” or the middle number. But when you change to thicker or thinner fabrics, tweaking the tension to fit the change in weight can make a world of difference.
It helps to get a sense of what a clean stitch looks like, and what happens to your stitches when the tension is too tight or too loose. So check out these examples of the three most common stitches — straight, zigzag and serger — then scoop up our top tips for making sure your stitches come out clean.
Good to Know: We’re not talking about the bobbin here — just thread. The bobbin has its own tension dial, but it’s super easy to throw off the alignment if you fiddle with it. Take it to a repair pro if you think the bobbin’s tension needs to be adjusted.
Here’s an example of what straight stitches look like with varying tensions. When it’s just right, your stitch will look like the one in the middle. The one on the left is too tight, causing the fabric to pucker, while the one on the right is too loose, making the stitches loopy.
Here’s the same stitch on the underside of the fabric. The middle stitch still looks ideal, but the puckering is even worse with the stitch on the far left. And those giant loose loops on the right not only look bad, but they also won’t hold the seam in place.
The differences are a little less obvious on the top layer with zigzag stitches. In the middle, we again have the stitch done with the perfect amount of tension. The stitch on the left had too much tension, so it pulled the fibers of the fabric together and caused a small lump between zigzag points. The stitch on the far right is too loose from point to point, causing a bit of shadowing under the stitch itself.
Much like the straight stitch, the real problem shows up on the underside. The stitch on the far right has loops where there should be points, which is what happens when the upper threads are too loose. On the left, the actual zigzag is narrower than it should be, as it’s pulling too tightly from point to point.
With a serger stitch, there are four threads to consider: two straight stitches, along with the upper and lower looper stitches. You need to test your stitch for all four threads each time you use your serger.
If you don’t, notice what happens when the tension is too low (on the right). Even though it’s correct for the straight stitches, the looper threads show the loosey-goosey effects. And on the left, the tension dial is turned all the way up, making the straight stitches so tight they’re nearly invisible, and pulling the looper stitches past the center point.
On the underside, you can see the middle stitch is nicely balanced between the threads and loopers. But on the right, the lack of tension created a mess, as the threads couldn’t pull the loopers correctly. And on the far left, the balance is off so the stitch isn’t quite right.
How to Nail the Just-Right Stitch
You could guesstimate how much to turn or lower the dial, but why waste time and fabric? Instead, cut a scrap of exactly what you need to sew — same fabric, interfacing and number of layers — and try out all the stitches you want to sew on the scrap first. Stitch on both the crossgrain and the length of grain, as well as on a curve or bias if those figure in to your project. That way, you can get a clear image of what your stitches will really look like as you sew your finished project.