I’ve heard many times that I should never adjust the bobbin tension on my sewing machine. Is that true? What if I need to sew with heavy thick threads? What if I often sew with a twin needle and can’t get the stitches to look right? What if I want to try different techniques that require some bobbin tension adjustment?
So, in this tutorial, I want to tell you everything I know about the bobbin tension.
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What is the bobbin tension?
Bobbin tension (as I understand it) is a small amount of pressure on the thread in the bobbin case created between the 2 parts of the case. One of these parts is a small flat bobbin case spring/plate/disk (I don’t know the name of the other part though).
When a sewing machine is working the moving thread is “squeezed” between these 2 parts and the amount of pressure on the thread is controlled by a small screw.
If you move these 2 parts closer together by tightening the screw the amount of pressure will increase, if you move them further apart by loosening the screw the amount of pressure will decrease.
If you wonder where the bobbin tension disks/plates are on a sewing machine (Brother, Singer, Janome) you can see them in the video below.
This small metal plate/spring is attached to the bobbin case with a screw. This is what gives the bobbin thread its tension. The screw is tightened and when the thread is going between this plate and the bobbin case there is some pressure applied to the thread. This tension spring assembly is set at the factory.
Perhaps it is useful to talk a little first about the bobbin thread.
✅ Related article: Bobbin Thread 101: Answers to Your Frequently Asked Questions
How to get the bobbin tension right
Now let’s see how to get the bobbin thread tension right. Correct tension is important if you want strong, durable, and beautiful seams.
The first thing we have to know – there are 2 types of bobbins: front-loading and drop-in.
Most modern computerized home sewing and embroidery machines have drop-in bobbins – they are plastic, you just drop the threaded bobbin in – and you are ready to go.
Front-loading bobbins – they have metal bobbin cases. Older sewing machines have them, but some new machines have them too. For example, I have only a few years old Janome machine (New Home 2212) with a front-loading bobbin.
These machines can’t sew with very big speed but on the other hand, they are usually very solid and can sew heavy-weight fabrics with ease. Modern longarm machines are also equipped with front-loading metal bobbin cases.
The bobbin tension is only a part of the sewing machine tension and must work in conjunction with the needle tension.
To obtain the correct tension setting make a test with the fabric and thread you plan to use for your project so that you can adjust the tension properly.
Bobbin thread showing on top
If the bobbin thread is showing on the top side of the fabric it means that the bobbin thread tension is too loose. You can see small loops of the bobbin thread on the right side of the fabric. I used different colors of the same type of thread in the needle and in the bobbin so it’s easy to determine if the tension is off. To adjust the bobbin tension it’s enough to adjust needle thread tension only. Decrease the needle thread tension – turn the dial to a lower number.
Needle thread showing on the underside
Below is an example where the bobbin thread tension is too tight. See – the needle thread can be seen on the wrong side of the fabric. The bobbin thread is pulling too much needle thread on the underside. Increase the needle thread tension – turn the tension dial to a higher number.
If the tension is correct the needle and bobbin threads interlock between the fabric layers. Well, kind of. If the fabric is very fine there is no space between the fabric layers for threads to interlock, actually.
In most cases, changing the needle tension is enough to get a perfect stitch. But sometimes the added tension is too big for the thread you are using and may cause thread breakage or skipped stitches. In this case, it might be necessary to change the bobbin tension also.
Older machines or machines with front-loading bobbins may need bobbin tension adjustment.
Bobbin tension test
If you want to find out if your bobbin tension is right for the fabric and thread you are using for the project you can perform a simple bobbin tension test.
The test is fun but not really very helpful. I heard about how to do the bobbin tension test a long time ago when I was just learning to sew.
Hang the bobbin case by the thread.
If the bobbin case doesn’t move at all when you jerk it the tension is too tight and you need to decrease the tension for sewing with this thread.
If the bobbin case drops quickly the tension is too loose and you need to increase the tension.
So, when is the tension correct? If you jerk the thread slightly – the case should drop a little and then stop. The thread should have a little resistance.
Well, my bobbin was jumping out of the bobbin case all the time so it seems to me this test is useless. Maybe it would work better with a metal bobbin, I don’t know.
If you want to check the bobbin tension properly use special tools made for this purpose.
Bobbin tension gauge
There are special gauges now so you can check your bobbin tension easily.
First, let me mention a bobbin tension gauge. It’s used mostly for longarm and mid-arm sewing machines. The tool is helpful if you regularly change the type and weight of your quilting thread.
There is also an interesting bobbin tension meter – check it out here (see the image below). The Featherweight Shop has it for sale and the tool can be used to measure the bobbin tension on any household sewing machine with a front-loading bobbin case.
But I don’t know any tool for measuring bobbin tension for the drop-in bobbins. I guess you have to figure it out for your machine – and test it with different fabrics, threads and needles.
So, the question is – can I change the bobbin tension?
Well, it depends.
Modern machines are coming from manufacturers with adjusted bobbin tension – you don’t change it usually even if you sew with different fabrics and different threads. Tension adjustments are mostly done just for the needle thread by turning the tension dial or knob on a sewing machine. Modern computerized machines may have an electric tension control.
Bobbin thread tension has been correctly set at the factory.
But this initial setting can change slightly if you use your sewing machine a lot for a few years. The bobbin tension can become looser even if you haven’t changed the setting yourself.
Sometimes it’s still necessary to loosen or tighten the bobbin tension.
You can change the front loading bobbin tension easily. But with drop-in bobbins – it’s not so easy.
When to adjust the bobbin tension?
Bobbin thread tension requires adjustment less frequently than the needle thread tension.
There are a few reasons for having to reset your bobbin tension. The required tension depends upon the thickness of the fabric, the stiffness of the fabric, the number of fabric layers being sewn, and the type of stitches and sewing techniques you are using. Also, there are many different thread weights. If you can’t get the stitch right by changing the needle tension adjust the bobbin tension a little.
You may need to change the bobbin tension in the following cases.
1. When you are sewing with very fine or very thick thread and it’s not good enough to change only upper thread tension for the stitches to look right.
2. When you change sewing thread from the regular weight (I think the regular weight is considered from 30 to 60) to some unusual one (like 12 weight threads for example, or if you use metallic threads). Different threads work better with different bobbin tensions.
3. When you’re using a twin needle. I have a detailed tutorial on how to use twin/double needles also, check it out.
4. When you’re using elastic thread in the bobbin for shirring.
5. When your bobbin thread keeps breaking and you keep getting skipped stitches but you can’t find any reason for that.
6. When free motion or ruler quilting, tension can be a real issue.
7. When you are doing stippling work.
But there are some other reasons also. When I bought my first Janome sewing machine many years ago (it was a brand new Janome Magnolia) I started to have tension issues from the beginning: I had to keep my needle tension at 1 or 2 instead of 4 (which is the normal setting) for any fabric and thread I tried to use.
I deduced something must be off with the bobbin tension. So I went back to the dealer in a few days and the technician told me that he had to reset the bobbin tension because it was not set correctly at the factory. This can happen also. After that my machine was working perfectly for many years.
Proper bobbin tension is also essential to good embroidery. If the bobbin tension is not set correctly for your embroidery machine you might experience frequent thread breaks which are not only annoying but also a big waste of time.
I had this unfortunate experience when I was embroidering with rayon threads – no matter what I did with my needle tension the thread was breaking every 5 minutes. But as soon as I adjusted my bobbin thread tension everything was fine.
It may take some persistence to figure out what works best for different fabrics and threads you are using for your projects. But once you figure out what tension works best, you will be able to reproduce it next time.
But before changing the bobbin tension make sure everything else is in the correct order. If your stitch is not perfect you shouldn’t think right away that the bobbin tension is at fault. There are many other reasons for getting bad results.
Check if you threaded the machine properly and if the thread is between tension disks. By the way, if you want to know how to thread a bobbin correctly check out my tutorial How to thread/wind a bobbin.
Check if the bobbin is wound correctly. I also have a tutorial on bobbin problems Sewing machine bobbin problems and solutions.
If the bobbin is wound loosely or the threads crisscross the tension might become uneven resulting in jamming the thread and causing it to break.
If you hand wind the bobbin with elastic or woolly nylon thread try to wind them evenly with uniform tension.
Check if the thread weight and the needle type and size are correct for the fabric you are using.
Check if the thread is a good quality thread.
Check for lint build-up in the bobbin case and make sure your tension mechanism is clean also.
It is quite common to have a piece of thread or lint lodged in between the tension assembly on the bobbin case. This prevents the normal tension applied to the thread and results in little or no bobbin thread tension. Even the smallest amount of lint can create big tension issues.
Check if your bobbin case is not damaged. Check for snags on the throat plate.
The bobbin case might get bent and need replacing.
Check if your needle tension assembly is worn out and needs replacing (if your sewing machine is old).
How to adjust the bobbin tension
So, let me show you now how to adjust the bobbin thread tension for front-loading bobbin cases.
You can see a screw-on this bobbin case from my Janome machine. Turn it to adjust the bobbin tension.
Sometimes front loading bobbin cases have 2 screws. One which is smaller is a holding screw that holds the tension plate in place. You should never touch this screw. And the second one is an adjusting screw which can be tightened or loosened to adjust the tension.
Before turning the screw, use a permanent marker and mark a starting point on the bobbin case where the tension was set at the factory. If you do this you’ll not forget how much you turned the screw and maybe you’ll want to turn it back if you need to use the regular thread again.
To increase the bobbin tension – tighten the screw by turning it to the right (clockwise).
To decrease the bobbin tension – loosen the screw by turning it to the left (counterclockwise).
Move the screw only a quarter-turn or even less at a time.
Test your adjustments on a piece of fabric you are going to use for the project and remember – a little turn of the screw can have a big impact on the tension.
And now let me show you a drop-in bobbin case. To take it out from the machine – remove the throat plate.
There are 2 screws on this bobbin case. One is a holding screw that holds the tension plate in place. Don’t move it. And another one is an adjusting screw which can be tightened or loosened to adjust the tension. Sometimes this screw is sealed with paint.
I’ve heard that if your sewing machine is still under warranty you can’t adjust the bobbin tension yourself on the drop-in bobbin case if the screw is sealed. I am not sure if this is true but it’s possible.
Have in mind that the information in this guide is quite general and I am not a technician – there are so many different sewing and embroidery machines now! Therefore consult your manual for specific instructions on adjusting the bobbin tension.
My screw is black and because of this I have a problem – I can’t use my black marker to mark the initial position of the screw. I guess gold or silver markers would work but I don’t have them right now. So I am not going to move it. But you see it’s possible to adjust the bobbin tension even on this bobbin case.
I think maybe it’s better to have additional bobbin cases for your sewing machine if you have the drop-in bobbins. It’s a very good solution to have an additional case with a low tension setting if you sew a lot with twin needles for example.
Or you can have one case for regular sewing and the other case can be adjusted when you need it.
If you recently bought a new sewing machine you might already have multiple bobbin cases in your accessories box.
Is your sewing machine acting up? I created the ultimate troubleshooting guide to help you out and compiled a detailed list of solutions to common sewing machine problems. Many of these problems can be solved with some basic troubleshooting or maintenance. Is your thread getting tangled or breaking? I’ll walk you through the steps to fix it. Are you struggling with tension settings, broken needles, or jammed threads? I have tips for that too. Don’t let sewing mishaps get in the way of your creative flow. Check my guide and show your sewing machine who is the boss – Troubleshooting Common Sewing Machine Problems (+ Solutions)
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