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How To Deal With Thread Tension?
- An Kesenne
Even though thread tension is a mystery for a lot of people who sew and it gets the blame for a lot of sewing problems, most issues are caused by other things than tension related problems. Did you know that incorrect threading is responsible for more tension problems than any other factor? A better understanding of thread tension and knowing how to get correct sewing machine tension is a sewing basic for every sewing machine owner. If you want to learn more about the thread tension, how to adjust the tension, and the different factors that have an influence on your thread tension, this article is for you!
A balanced stitch
Making nice and even stitches is what we all want, right? To make a correctly-formed stitch, a sewing machine needs a top and bottom thread. In order to form a row of stitches that looks the same on both sides of the fabric, the same amount of thread needs to flow from the spool and the bobbin simultaneously. These threads need to work in harmony with each other. If there is an imbalance, then one will pull the other through to the other side of the fabric. This will cause a poor quality stitch that may not hold.
What is thread tension?
Thread tension is the amount of thread that passes through the machine to create a stitch. The more thread in the stitch, the looser the stitch. The less thread, the tighter the stitch.
The bobbin thread tension is usually factory-set on a household sewing machine and you normally don’t have to touch this. So I’ll focus on the top thread tension in this article since that’s where most of you will make adjustments and will be able to solve tension issues. If you do want to make changes to the bobbin tension, check your machine's manual first. In most cases you’ll need to remove the needle plate, and when you take out the bobbin case, you’ll have access to the bobbin tension screw. If your machine uses a separate bobbin case, the little screw is built in on the spring of the case.
What controls the thread tension on your machine?
Threading a machine correctly is vital. Every thread guide on your machine puts pressure on the thread. A correctly placed bobbin and spool are also part of the balance. The most important part are the tension discs that control the top thread. They are commonly hidden in the right slit where you guide your thread down before it goes up in the thread take-up. On older machines they can be visible, as you can see in the photos below.
Old or new machine, the thread has to sit correctly between the tension discs when you’re threading your machine. If it doesn’t, then the machine won’t be able to sew properly. When your presser foot is up, the tension discs are open and there is no tension on the top thread. That’s why you get lots of loops when you try to sew with the presser foot up.
On most sewing machines the top thread tension can be adjusted with a little wheel close to the thread take-up. It is usually referred to as the tension regulator or tension control. This wheel controls the amount of pressure on the discs and thus the top thread tension. The settings run mostly from 0-9, 4 or 4.5 being the default position for a straight stitch and most fabrics. Some machines, like my Pfaff, only have a + and - indication. Tension settings vary slightly between machines. When adjusted to a higher number, the discs move closer together, increasing the amount of tension. When the tension is turned to a lower number, the discs move apart, decreasing the tension. Some new machines can even adjust the upper tension automatically.
What other factors have an impact on thread tension?
Many things affect thread tension and stitch balance, such as the thickness of the threads and weight of the fabric you are using.
- Densely woven fabrics will expose the top thread to a greater degree of friction.
- Batting adds drag on the top thread.
- Cotton threads tend to have more grab to the fabric compared to a smooth filament polyester thread, for example.
Different stitches require a different tension as well.
- A zig-zag stitch, or any other stitch that has width, can pull the bobbin thread through to the top more easily than a straight stitch.
There are no general rules and predefined settings for different threads, fabrics, stitches. You will have to test every time. Don’t be afraid to experiment and find the setting that’s best for your specific project.
Troubleshooting? Check this first!
As I said at the start of this article, most issues on sewing machines are caused by factors other than purely tension related problems. So when you have problems with the thread tension, go through this checklist first before you start turning the tension regulator.
Is your machine threaded correctly?
- Did you pass through all the thread guides?
- Never thread a machine with the presser foot down. The tension discs should be open to fully grab the thread. So put the presser foot UP when you thread.
- Is thread unwinding freely from the spool? If it is catching somewhere, it will lead to a very tight top thread
- Is the thread string coming from behind the spool?
- Is the bobbin inserted into the bobbin case correctly? On front loading machines, make sure the thread is going clockwise as you drop it into the bobbin case. On a top loading sewing machine, check the bobbin thread has tension on it. If not, take it out and pop it in again, following the directions indicated.
3. Is the presser foot lowered? You don't want to know how many times this happens, especially if you are working with thick layers.
4. Is your bobbin evenly wound? Remove any thread from the outside of the bobbin. Messy bobbin = messy stitch!
5. Clean your machine! Check for lint and thread ends between the tension discs, under the needle plate, around the bobbin case and bobbin.
6. Check for damaged machine parts. Change your needle. The smallest damage on a needle or bobbin can distort the tension.
How to test thread tension?
If you want to test or troubleshoot your thread tension, take a piece of fabric, thread your machine and use 2 different threads for the top and the bottom thread. This makes it easier to diagnose problems, so you can see where the trouble is coming from.
Now start with a thread tension of 4.5 and sew a row of stitches.
There are 3 scenarios that you can come across:
- The top tension is too loose. You can see the top thread underneath. You can pull out the bottom thread easily. Put the thread regulator a little higher, on 5 for example, and test again. If it is still showing, put the tension on 5.5 and test again. Repeat these steps, adapting in little increments, until you don’t see the top thread underneath any more.
- The top tension is too tight. The bobbin thread is showing on top. Put the thread regulator a little lower, on 4 for example, and test again. If it is still showing, put the tension on 3.5 and test again. Repeat these steps, adapting in little increments, until you don’t see the bobbin thread any more on top. Repeat this until you don’t see the top thread any more.
- You have a perfect tension. What you see is a beautiful symmetrical stitch, a row of stitches that looks the same on both sides of the fabric.
If you’re sewing on really thin or lightweight fabrics, both threads may show on both sides when the tension is balanced, simply because the fabric is so thin.
You have to know that getting the tension right is a trial and error process with your specific sewing machine, your fabric, your thread, your stitches. You will have to figure out what tension works best for you.
I hope this little introduction gives you a better understanding of thread tension and will help you fix some common issues with bad stitches all by yourself!
Questions? Don’t hesitate to leave a comment or send me an email! firstname.lastname@example.org. I’ll try to help you the best I can!
Writing and making videos about sewing for MadamSew.com