Last month I wrote a post about using interfacing when you paint with thread (aka free-motion embroidery). This month I want to share some information about thread tension when doing free-motion sewing. This information is appropriate for thread painting and free-motion quilting.
When I was younger, I remember a sewing machine technician strongly telling me and my dad that we should “never touch the tension dial!” I adhered to that rule and it so intimidated me … until I started quilting.
Thread tension is the the point 
where the thread coming from the spool (top of the machine) has a balanced pull with the thread in the bobbin (bottom of the machine). Think of it as a tug of war between the two (see image). If the top tension is too tight, it will pull up the bobbin thread and you’ll see little pop-ups of that thread on the top of your work.
If the top tension is too loose, it will get pulled to the back of the work by the bobbin thread.
The tension dial on the front of your machine controls the tension of the top thread and is helpful in balancing the tug of war.
- There’s also a way to adjust the bobbin tension, but most of the time top tension adjustments are all we need. So to keep things simple and easier I’ll only discuss the top tension. If necessary, you can learn more about adjusting the bobbin tension by referring to your sewing machine’s manual.
Tension balance is affected when we sew different materials, think of the difference in thicknesses between quilts, fine fabrics, heavy denim, quilters cotton, etc. The tension has to be adjusted to accommodate each because the thickness of the layers is different.
When you sew, always do some test stitching with the materials you plan to use. I check when I first start sewing, every time I change the top or bobbin thread (stuff happens), and any time I use different stitches (e.g., straight vs zig-zag). Look at the stitches on the front and the back of the work. Do you see an in-balance in the tug of war?
When sewing machine mechanics service our machines, they adjust the tension to accommodate straight stitching on light weight cotton fabric with the tension dial set mid-way. My tension dial has ten numbers (0-9). In this set-up, the mid point is 5. So the mechanic set my machine to have a good balance on cotton at #5. This is good to know…because if things get wonky, we can go back to the middle setting and start over. Also remember to set your machine back to that setting when you straight sew.
If your sample stitching indicates an adjustment is needed, you can refer to the chart on this page which indicates what you do for each scenario (feel free to right-click on the image and save it to your computer). Make minor adjustments at a time and check your stitching again. Check both front and back of your work because it’s possible to over compensate. Did you solve the issue? If not, make some more adjustments.
It’s not so intimidating when you get comfortable with the concept. When your stitches don’t look their best, you can be confident it setting them right. It’s good to know how your machine works and how to improve your stitching.