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How to Adjust Sewing Machine Tension for Perfect Stitches

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In order to create the perfect stitch, you need to know how to adjust your sewing machine tension.

Why?  Because poorly adjusted tension can ruin any sewing project.  You might end up with huge loops of thread on the bottom of the fabric or find the lower bobbin thread pulled to the top of the fabric.  The stitches may be too loose, or they may be too tight, causing the fabric to pucker.

As a beginner sewist, I remember being mystified about the idea of tension.  For the first little while, my sewing machine remained stuck on a “4” because I was so afraid I’d ruin the machine if I adjusted the tension.  All was great until I decided to change to a thick fabric sewing project with a heavyweight thread.   After troubleshooting forever to find my problem, I fearfully decided it was time to touch the tension dial to address my tension issues.  Turns out, fixing tension is a lot easier than I thought it would be!

If you, too, are afraid of sewing tension, have no fear! This sewing machine tension guide will give you an idea of what sewing machine tension is and when to adjust it, what other issues may be causing your stitching problems, and finally, how to adjust your sewing machine’s tension to achieve the best results.

how to adjust sewing machine tension

But first, what is sewing machine tension?

Sewing machine tension, or stitch tension, is the pressure on the threads as they pass through the sewing machine.  There are two threads that form every stitch: the top thread, which goes through the needle, and the bottom thread, which is from the bobbin.

A perfect stitch depends on the balance between the two sources of tension on the stitch (as well as other factors.)  Ideally, the top thread and bobbin thread are drawn equally into the fabric, forming a link in the middle of the fabric layers.  The stitches should look the same on the top and bottom of the fabric, and the knot should be hidden within the fabric.

Too much tension on the top thread (or too little on the bottom) means not enough top thread gets into the stitch, causing puckering and the bobbin thread to show on the top of the fabric.  Too low of top thread tension (or too high of the bottom) means too much thread is drawn into the stitch, causing a loose stitch and the presence of the top thread on the bottom of the fabric.

Sewing tension issues, because they are caused by an imbalance between the pressure on the two pieces of thread, can be caused by inappropriate top or bottom thread tension.

How does top tension work?

In most cases, there are two metal discs on the top of the sewing machine that provide the top thread tension.  A spring regulates the pressure to the thread on one side of the metal discs.  This spring is then controlled by a dial (or a computer with computerized machines.)  Increasing the number on the dial will increase the tension, or pressure, on the thread.  Some machines will have tension that automatically adjusts, but often you will have to adjust it yourself.

Your sewing machine tension dial could be located on the top, front, or left side of your sewing machine.  The tension numbers commonly range from 0-9 or even 1-10 usually.

When the presser foot is raised, the tension discs separate, allowing the top thread to slip in between them.  When the foot is lowered to begin stitching, the discs come back together and apply the selected tension to the thread.  This is why you should not thread your machine with the presser foot down.  Since the top thread does not enter the discs, there is no tension.  As a result, the top thread is pulled to the back of the fabric and can create loops.

How does the bottom (bobbin) tension work?

This tension of the lower string, or bobbin string, is usually controlled by a screw on the bobbin case.  Most bobbin cases will also have a small tension spring on them that you’ll need to pull the thread into when setting up your sewing machine.

As a beginner sewist, adjusting the bobbin tension should be one of your last resorts when troubleshooting stitching issues.

Situations Requiring Tension Adjustment

There are several situations where you may need to readjust your tension before starting to sew.  Many of these are when the top thread is changed drastically.  Examples include:

  • Changing the thread weight (heavyweight to lightweight or vice versa)
  • Switching to a different material thread
  • Changing to a different brand of thread

Troubleshooting Before Adjusting the Tension

When troubleshooting a problem with your sewing machine’s stitching, here are some questions you want to ask yourself first before fiddling with tension.  Because, honestly, a lot of the time when I’m not sure what’s going on with poor stitching, it turns out to be something else than the tension.

  • Is your sewing machine threaded properly?  First, make sure the thread from the spool follows all the thread guides as directed in your sewing machine manual.  Also, make sure you remembered to thread the sewing machine with the presser foot up.   If in doubt, just rethread.  It doesn’t take too long and is great to rule out.
  • Is the bobbin wound and installed correctly?  Make sure the bobbin is in the correct orientation and that’s it’s not wound too loosely, tightly, or unevenly.  Also, while you’re looking at your bobbin, check to make sure this area of your sewing workspace is clean and lint-free.  If it’s not, clean it out. I remember the first time I opened this area my workspace and found a ton of dust bunnies I had no idea were down there!
  • Are you using the correct needle size for your fabric, and is the needle still good?  Choosing a correct needle size really does matter!  Also, using a bent or dull needle can cause stitching issues as well.  (Check out my exhaustive list of sewing machine needle types and sizes to make sure you’ve picked a compatible needle for your project.)
  • Do you have a thread weight that’s compatible with your needle size and fabric?  Also, in most cases, the top and bottom thread should be identical, so ensure this is the case if you’re having unexpected issues.
  • Have you picked a compatible type of stitch (and adjusted the length and width, if applicable?)  Certain stitches are just not made to be compatible with all fabrics.

Ideally, this will take care of your issues, but if not, you may need to move on to fixing your sewing machine’s tension.

How to Adjust the Tension on Your Sewing Machine

As I mentioned earlier, both the top tension and bobbin tension are adjustable.  When in doubt, start with adjusting the top tension.

How To Adjust Sewing Machine Top Tension

Every sewing machine will have a default value for top tension.  You should be able to find this value or at least a range of suggested sewing machine tension settings in your manual.  If you’re having tension problems, first try stitching with the suggested value.

I sew primarily on the Brother CS6000i sewing machine, and here’s where my tension dial is located.  For most Brother sewing machines, even the Brother Project Runway sewing machines, your sewing machine’s tension dial will be in a similar location or at least very easy to locate.

To adjust the tension, first do a test stitch.  You ideally want to be using both the fabric and thread that you’re planning to use for your project.  If you have difficulty seeing the stitches, switch to a contrasting fabric with the same characteristics.

After sewing, examine the stitches.  You want the knot where the stitches cross to be in the middle of the fabric and for both sides of the fabric to have even stitches.  Meaning no loose stitches and no puckering.

If the knot is too far into the bottom of the fabric, you’ll need to increase the top sewing tension to pull the knot up.  Remember, a higher number on the tension dial means a higher tension.  

If the knot lies too close to the top of the fabric, the tension needs to be decreased so the top thread doesn’t pull the stitch up as much.  You will want to pick a smaller number on the tension dial.

Pictures of Incorrect Sewing Machine Tension

Here’s what tension looks like from the front of the fabric when it’s too tight and too loose.  Notice the tight looking stitches and the fabric puckering when the tension is too high.

Here’s what too tight of tension will look like (up close) on the front of the fabric.  See how the knot forms closer to the top of the fabric.

Here’s what the bottom of the fabric looks like when the tension is out of whack.

Up close, this back of the fabric picture shows too loose of tension will cause the knot to be closer to the wrong side of the fabric.

When you go to adjust the tension, don’t change the dial too drastically.  Go maybe one or two numbers to the right or left and then stitch again.

Keep doing test stitches until you find that your stitches are balanced.

How to Adjust Bobbin Tension

Unless you know what you’re doing, adjust the bobbin tension as the last resort.  Most sewing machine tension problems are related to the top thread or one of the other possible errors described above.

Should you need to adjust bobbin tension, though, first remove your bobbin from the bobbin case.  Using a screwdriver, you can then turn the small screw on the bobbin case.  Only turn the screw a small amount using minimal force and being careful not to damage the bobbin case.

Turning the screw clockwise will tighten bobbin tension; turning counterclockwise loosens the tension.

Here’s where I adjust bobbin tension on my Brother sewing machine:

See the tiny screw on the bobbin case of my CS6000i sewing machine.  I’ve removed the bobbin first and pulled the case out from my workspace.

where to adjust bobbin tension on Brother CS6000i

Hopefully, this tutorial will help solve your stitching issues!  However, if you’re still having problems after troubleshooting with all these suggestions, it might be time to take your sewing machine in to be examined by a professional.

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8 Comments

  1. I am grateful for this post! I couldn’t figure out what’s was happening with my stitches, but your post really helped! Thank you!

  2. I have this same exact machine. I am having SERIOUS tension problems. The top tension is too low. I have it turned all the way up to 9.
    There are TWO screws on the bobbin case; the regular straight screw off to the left, and the phillips head screw (cross) on the right. Which one gets turned for tension? I cannot turn the phillips head screw no matter what. The flat head screw has green goo all over it. Is that what I turn? Or try to?

  3. I have another question about this machine. Every time I replace the bobbin, like when it gets empty, I refill the same exact bobbin with the same exact thread. Yes it is the right bobbin, the 11.5-mm one. Yes it is set properly in the right direction. Yes the top thread is threaded properly. I had been stitching my project and it was fine. The bobbin emptied, I refilled it, and replaced it in the machine…. and I get a total rat’s nest of bobbin thread when I stitch. I have changed nothing. No matter what I do, rat’s nest!!! That’s when the bobbin thread is not getting caught up on the metal beneath the feed plate.
    I don’t get it. I’m ready to chuck this machine.
    I am a VERY experienced sewist… been stitching on all sorts of machines for >40 years. No machine has ever given me the grief this one does.
    Can you offer any ideas? Thanks.

    1. My father (RIP) who repaired sewing machines gave me very good advise when I too had similar problems; when you rewind the same bobbin or different bobbin put the through a brief cleaning. Take the throat plate off, I use a small paint brush, clean the bobbin casing, feed dog, the teeth, around the bobbin down inside, the needle shaft, and thread guide. Just briefly run it over the machine. Cleaning the tiny dust particles off. Another item about the bobbin, check for gouges in it from the needle, sometimes it brushes against it and put a slight mark on it. He also stated to run the machine really slow watching the action of the needle thread going down and around the bobbin casing, insuring that it is actually going around the bobbin casing properly. I hope this helps.

  4. Hi, I am a new sewing machine user on a Brother GX37 and am trying to follow the Operation Manual to find correct stitch length and stitch width for a zigzag stitch.
    The chart in their manual says, stitch name -Zigzag Stitch
    Pattern – 3
    Stitch Length [mm (inch)] Stitch Width [mm (inch)]
    F-4 0-5
    (1/64-3/16) (0-3/16)

    I don’t know how that relates to the dials for pattern width and length. Would appreciate any help figuring it out. I seem to spend more time reading and watching videos than sewing.

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