It’s probably happened to you: skipped stitches, breaking thread, puckering fabric around your sewing line, or even thread nests on the back of your fabric. As diverse as these problems might seem, they all come down to thread tension. Do you know how to adjust tension on a sewing machine? It’s easy, and it can save you a lot of aggravation.
Why Sewing Machine Tension is Important
Your sewing machine has two threads: a top thread and a bottom, or bobbin thread. When you sew, your machine interlocks these two threads to form a chain.
Your sewing machine holds each of these threads taut as it pulls them through the machine. This helps them to work together to form tight, even, consistent stitches. But if the tension of either thread is off, it can cause problems with your stitching.
When it comes to tension problems, the top thread is usually, though not always, to blame. But many sewing machines allow you to adjust the tension of both threads. We’ll show you how to do that in a little while.
Some sewing machines have an automatic thread tension feature. This feature sets the tension for the type of sewing you’re doing at any given time. However, there will be times when you want to do that fine tuning yourself. Specifically, certain fabrics and thread types may require a bit of manual adjustment to get your stitches just right.
Fabric Type and Thread Tension
The thickness, texture, and fibre composition of a fabric give that fabric its specific qualities. They determine how a fabric feels to the touch, how it drapes, whether it stretches, and how it moves through the sewing machine. They also determine how a given fabric will interact with the thread. Different fabrics, therefore, will work best with different thread tensions.
In general, lightweight fabrics will require finer threads and tighter tension. Conversely, you’ll need to sew heavier fabrics with thicker thread, using looser tension.
Thread Type and Thread Tension
Many kinds of thread are made to work at a variety of tensions. The important thing, however, is matching.
Always match your top thread and bottom thread in terms of weight and fibre composition. Use polyester thread with polyester thread, cotton with cotton, lightweight with lightweight, and so forth.
Likewise, match your thread to your fabric. Lightweight fabric needs lightweight thread; heavier fabric needs heavier thread. Also, sew synthetic fabrics with synthetic thread and match natural to natural.
Also, please note that poor quality thread can damage your sewing machine’s tension disks in a number of ways. It can leave dust and debris on your disks. It can also knot in the tension mechanism and cause wear and tear on your disks.
A Few Words About Needles
The wrong needle can cause problems with your sewing machine tension.
Well, the needle pokes a hole in the fabric then guides the thread through. If the needle is too large, the hole it creates will be too large to hold the thread optimally. This, in turn, can affect the top thread tension. It may cause puckering or other problems related to unbalanced stitches.
To Sum Up
- Use only high quality thread
- Use the same thread for top and bottom
- Match your thread to your fabric type
- Use the right needle
- Lighter fabrics require tighter tension; heavier fabrics need looser tension
What Number Should the Tension Be on a Sewing Machine?
There’s no one-size-fits-all answer to this question. First, different types of sewing require different tension settings. Also, not every sewing machine manufacturer follows the same labeling convention for its tension adjustment mechanisms.
However, there are a few guidelines that may help.
Most sewing machine tension dials will be numbered 0 to 9 or 1 to 10. As you might guess, lower numbers mean lower tension. Likewise, a number in the middle, like 5, means a medium tension, which is a good, general-purpose tension setting.
If your tension dial has an “A,”, that’s the automatic setting. This can mean a few different things.
Higher end sewing machines have sensors that measure your fabric thickness and other variables so that your machine can select the correct tension.
Other machines may adjust the thread tension to fit the stitch type. These adjustments don’t take into account fabric type or thickness, however, so you may still need to make manual adjustments.
Mechanical and lower-end computerized machines may have one universal or “automatic” tension that works well for a variety of different kinds of sewing. But again, you may still have to adjust for fabric type and thickness.
When in doubt, do a series of test stitches. If your fabric puckers, the tension is too high. If the stitches are loose, the tension is too low.
Incorrect tension can cause other problems, too, and we’ll discuss them in detail in our troubleshooting guide. Because knowing how to fix sewing machine tension can eliminate a whole range of problems.
How to Adjust Upper Thread Tension
If you’re having problems with thread tension, most of the time, the problem will be with the top thread. Fortunately, most sewing machines make adjusting the top thread tension easy.
First, check to see that your tension mechanism is working correctly. Lower your presser foot and give the upper thread a gentle tug. If the thread is tight, the mechanism is doing its job. If not, then it may be time to consult a sewing machine repair professional.
Next, determine whether your problem is stemming from too much tension or too little.
Now, use your sewing machine’s dial or knob to adjust the tension. Remember: the larger the number, the higher the tension.
Sew a few test stitches after each adjustment to gauge whether further adjustments are needed.
Your stitches should be even, with no looping or nesting on either side. There should be no puckering around your line of stitches. The bottom thread should not show through on top, nor vice versa.
How to Adjust Bobbin Tension
As we said before, the majority of tension problems will come from the upper thread. Even when the problem appears to be with the lower thread, such as loops on the fabric surface or the bottom thread showing through on top, the problem may not be the bobbin thread, but the relative tightness of the threads to one another.
The top thread is easier to adjust, so start there. Also make sure that:
- Your bobbin is wound correctly
- You have threaded your sewing machine the right way
- The tension mechanism is clean and free of debris
- You’re using the right needle for your thread and fabric
- The thread matches both the fabric and the bobbin thread
If you’ve determined that the lower thread really does need to be adjusted, here’s how to adjust tension on a sewing machine bobbin.
How to Adjust Tension on a Side-Loading Bobbin
Remove the bobbin case. You will find a small screw on the side. With the bobbin still in the case, tighten or loosen the screw very gradually. Start with a quarter-turn at a time.
How to Adjust Tension on a Drop-In Bobbin
The bobbin case on a drop-in bobbin sewing machine looks a bit different from the metal bobbin case of a side-loading bobbin. However, this is also the place where you’ll be making the adjustment.
Take the bobbin case out of your sewing machine. With the bobbin removed from the case, find the screw. It will be in the front, near the spring that holds the thread. Adjust slowly and gradually, between one quarter-turn and one half-turn at a time.
Are Tension Adjustments the Same for Every Make and Model?
Unfortunately, no. Different sewing machine makes and models will often have slight differences when it comes to thread tension regulation. However, the general principles are the same. And if you understand these general principles, then you’ll be able to understand how to adjust thread tension for your sewing machine.
The top thread of everysewing machine travels along a path of obstacles from spool to needle. The path is different for different sewing machines. However, the purpose is always the same: to keep your upper thread from tangling, and to regulate that thread’s tension.
Most sewing machines mark the path between thread guides with arrows and numbers. If you’re having tension-related issues, double check your thread diagram to make sure you’ve followed the thread guides properly.
Your sewing machine’s tension assembly consists of tension disks and a tension regulator.
Tension disks are small metal disks through which the thread passes before coming to the needle. The disks squeeze the thread to create tension. The tension regulator controls the amount of pressure that the disks exert on the thread. You can adjust this pressure using your sewing machine’s tension knob or dial.
The principle is the same for all sewing machines, though some machines may have a knob for adjustments, while others have a dial. Also, the numbering may differ on the knob or dial. And some sewing machines may also have an automatic or universal setting that others lack.
If you’re experiencing tension problems, first make sure that your regulator is set to the correct number for the type of sewing you’re doing. Also, check your disks, and, if necessary clean out any dust or debris.
Sewing Machine Tension Troubleshooting
Now that you understand a bit about thread tension and how your sewing machine regulates it, it’s time to consider specific tension-related problems.
First, Make Sure That Tension Really Is the Problem
Before you reach for the tension dial, it’s worth considering whether the problem really lies with thread tension regulation. Thread and stitches can go wrong for a number of other reasons. So consider a few of these first.
Sewing Machine Needle
You should always start every new project with a new needle of the appropriate size and type. Make sure that your needle is not bent or damaged in any way, and that you have installed it correctly. Several problems can stem from a bent, damaged, inappropriate, or wrongly-installed needle, including:
- Broken threads
- Loose stitches
- Uneven stitches
- Fabric damage
- Skipped stitches
- Thread shredding
Check Your Thread
Are you using the appropriate weight thread for your project? Are you matching synthetic thread with synthetic fabric, and natural thread with natural fabric? Do the upper and bobbin threads match? And, importantly, are you using a high quality thread? If not, then you might experience problems like these:
- Broken threads
- Fabric puckering
- Fabric damage
Double Check Your Threading Diagram
Have you threaded your machine correctly? Are you sure? Go back and check. We’ll wait. If you’ve missed out one of your thread guides, not threaded the tension disks correctly, or mixed up the threading steps (it happens!) you might see the following problems:
- Breaking threads
- Thread bunching
- Machine jamming
- Loose stitches
What About Your Bobbin Thread?
If your bobbin thread isn’t drawing, it’s possible that the bobbin is sitting incorrectly in the case. Have a look and re-insert your bobbin if necessary.
An incorrectly wound bobbin can also cause problems, such as fabric puckering.
Check the Spool Cap
The spool cap holds your thread on the spool pin. If it’s too tight, it may cause your thread to jam or break. If it’s too loose, that can cause problems, too.
Is Your Presser Foot Down?
We all forget to lower the presser foot from time to time. The presser foot activates the tension disks, so you can imagine what will happen if you try to sew with it up. That’s right: no upper thread tension. This is what it looks like.
Is Your Machine Clean?
Over time lint, dust, and grease can gather in parts of your machine, including the tension disks and tension regulator. This can impede the flow of thread through your tension assembly. If the thread isn’t feeding correctly, give your tension assembly a good cleaning. Here’s how.
If you’ve gone through these steps and nothing has helped, now it’s worth looking at the thread tension.
Diagnosing Tension Related Problems
So, you’re certain that tension is causing your difficulties. It’s time to narrow that diagnosis down.
Is it the Top Thread or the Bobbin Thread?
Once you’ve figured out that your problem is tension-related, it’s time to decide if the problem lies with the upper thread or the lower one.
Generally speaking, the problem will appear on the opposite side of the fabric from the problem thread. So if the symptom appears on the fabric surface, the bottom thread may be to blame. Likewise, if you see an issue on the underside of the fabric, the cause probably lies with the top thread.
Again, most of the time the top thread will be the culprit. Even when it looks like the lower thread is to blame, it’s worth checking to see if you can remedy the situation by adjusting the tension of the upper thread relative to that of the lower.
Too Tight or Too Loose?
Thread tension requires a Goldilocks solution: not too tight and not too loose. Here’s how to tell which adjustment to make.
Signs that one or both threads are too tight:
- Bottom thread coming through to the surface (top thread too tight)
- Top thread pulling through to the underside (bottom thread too tight)
- Fabric bunching
- Fabric puckering
- Broken thread
- Stitches breaking when stretched
- Machine jamming
If your top thread is too tight, for example, your bottom stitches may look like this:
Signs that one or both threads are too loose:
- Gaps in the seam
- Skipped stitches
- Uneven stitches
If your top thread is too loose, for example, your stitches may turn out this way.
10 Sewing Machine Problems and What They Might Mean
A quick guide to common symptoms and what might be causing them.
Top or bottom thread tension too tight, thread mismatched to fabric, incorrectly wound bobbin
Broken Threads or Stitches
Damaged, incorrect, or incorrectly installed needle, top or bottom thread too tight, machine not threaded correctly, dirty tension assembly, poor quality thread, spool cap too tight
Top or bottom thread too loose, spool cap too loose, machine not threaded correctly, presser foot up; wrong, damaged, or incorrectly installed sewing machine needle
Top or bottom thread too loose; wrong, incorrectly installed, or damaged sewing machine needle, sewing machine not threaded correctly
Gaps in the Seam
Top or bottom thread too loose, spool cap too loose
Loops and Nests
Top or bottom thread too loose, spool cap too loose, sewing machine not threaded correctly, presser foot up
Bottom Thread Showing on the Surface
Top thread tension too tight, or too tight relative to bottom thread
Top Thread Showing on the Bottom
Bottom thread tension too tight, or too tight relative to top thread
Top Thread Not Feeding
Incorrectly threaded sewing machine, dirty tension assembly, spool cap too tight; wrong, incorrectly installed, or damaged sewing machine needle, top thread tension too tight
Lower Thread Not Feeding
Bobbin thread tension too tight, bobbin incorrectly wound, bobbin sitting incorrectly in bobbin case
Does Your Thread Tension Need Attention?
Thread tension problems can be the bane of any project. And once you understand how thread tension works, it can be easy to fix, or even prevent them.
At the same time, lots of things can cause issues that look like tension problems but aren’t. And many tension problems aren’t caused by — or cured by — the tension regulator.
Before reaching for that dial, consider other factors that may affect tension:
- Are you using a new, undamaged sewing machine needle that’s gauged for your project?
- Have you matched your top and bottom threads to the fabric and to each other?
- Is your machine threaded correctly?
- And is your tension assembly clean and free of debris?
Most true tension problems come down to the upper thread. However, sometimes the bobbin thread is to blame. Fortunately, neither one is complicated to adjust.
Do you have a tension tip or trick you’d like to share? We’d love to hear about it in the comments!