Fragile Tension – Tension does not have to equal stress (Updated with a video)

Possibly the most common reason a machine ends up on my bench is for tension.  Usually bird’s nests.  The thing is easily 80% of the time, there’s nothing really wrong with the machine that a repair person needs to look at it.  Sometimes it’s basic maintenance, sometimes it’s because someone told you at some point “DON’T YOU TOUCH THAT! EVER!”

I’m sure that the people who’ve said that meant well, but today I’m going to show you how to manage that dial properly and what to do when it’s not proper.

I’m sure there are some of you out there who are thinking, “no no, she’s talking about that which shall not be touched”…. but it’s true.  That tension knob is meant to be adjusted by you!

Here are 3 clues to the truth of this statement:

  1. They talk about tension adjustment in the owner’s manual.  Many manuals even touch on both the upper and bobbin tensions.
  2. It’s within easy reach of you when you operate the machine.
  3. If it wasn’t meant to be user adjusted, it wouldn’t have numbers on it.  (Yes, I know that some of the older machines don’t have numbers, but for the sake of simplicity, for the moment, let’s pretend they do)  Your OSMG (Old Sewing Machine Guy, Gal or Glutton-for-punishment) has no need of numbers.  We use feeler gauges and fancy measuring tools like bags full of Kamut berries.

I find that tension problems can be broken up into 4 major groups.

  1. Something on the machine is assembled wrong, broken, or missing.  This is really common when a machine is used but new to you.  Often people have taken things apart, reassembled wrong, gotten frustrated and unloaded the source of their frustration on you.
  2. The sewist operating the machine has been taught to never adjust the tension on a machine – often this person will tell me too “my machine doesn’t like x thread (or x fabric), or it doesn’t like piecing (quilting, FMQ, jeans, light fabrics, heavy fabrics, etc)
  3. The sewist has never heard the above rule, but doesn’t understand tension, and just turns and turns until it works out right.  Sometimes this person will tell me the same things as #2, or say that they really have to fight to change fabric types (thread types, project types, etc)
  4. The machine is in need of some basic maintenance.

Note:  You may have noticed that I don’t call us sewers.  That’s because we’re not a bunch of pipes where shi…. crap and toilet paper collects.  Sewists reads better, even if my spell check doesn’t like it.

Note 2:  I’m not picking on anyone.  We’re all products of our learning, and some of us were taught to be terribly cautious, and some of us are tinkerers.  I fall into that second category.  I bet you’d never have guessed that though. 😉

Here’s a fundamental truth of sewing machine tension:

If the thread is fully seated in between the tension disks, and it’s threaded right using an appropriate thread and needle for the application, and the tension dial is somewhere between 3 and 5 (assuming a scale of 0-9), it should work, unless someone has messed with either the top or bottom thread tensions.

This is most applicable for “regular sewing”.  Let’s leave free motion and decorative stitches for the moment. I’ll address it later, I promise.

Tension doesn’t have to be difficult.  It doesn’t have to cause you stress.

If you’re experiencing some trouble with a machine, I’d like to walk you through a few little tests to see if we can pin point where the problem is.  In the next couple of articles, we’ll talk about the things that can go wrong, which symptoms point to which problem, and adjusting the things that need to be adjusted when something’s actually gone wrong.

First, make sure there are no obvious pieces of your upper tension assembly missing or broken.  No, I’m not suggesting that you disassemble it and count the parts. 🙂  If this is a new machine to you, try searching the Internet for a clear photo of the upper tension on your machine.  Going to Google, or Bing for instance and typing: Singer 401A Tension then clicking on Images gets me lots of great photos to compare with.

A photo like this can help you determine if your tensioner has all the pieces it’s supposed to have. This came off a model 27 from 1913, but will be similar to the tensioners on many machines from the same time frame.


  • For exposed tensioners, pay particular attention to the tension spring.  Often it’s mangled or broken off or in the wrong spot.
  • Another clue to a mis-assembled upper tensioner on an exposed tensioner is the dial should turn to 0 and stop.  If the nut that holds the thing together just turns til it falls off, this is wrong.  Don’t worry, it’s not ruined for good, it just needs to be reassembled correctly. The knob should also give you the full range, all the way from 0 – 9 and you should be able to feel the tension change between the disks.  Just going from 0 – 7 (for instance) indicates the tensioner is mis-assembled.

Next, let’s check how the upper tension is working.  To do this, use a 90/14 needle, it doesn’t matter what type of needle (denim, knit, etc) and thread using a 50wt thread. (Gutermann sew-all thread is unlabelled as to weight, but it’s typically about a 50wt thread, so it’s fine here.):

1.  With the presser foot up, turn the tension dial to 0, and with the machine threaded properly up to, but not through the needle, pull on the thread. Note how it feels when you pull the thread.

Now put the presser foot down. It should feel really close to the same, maybe a smidge tighter, turning the dial to 1 should put noticeable drag on the thread.

2.  With the presser foot still down, thread the needle.  Now start slowly turning the dial to raise the tension while pulling the end of the thread.  Pull the thread in the direction the thread would normally feed (ie. if you thread right to left – pull left, if you thread front to back, pull backwards)  By the time you reach 3 – 5, there should be enough tension on the thread that the thread should “deflect” the needle some (maybe about a 1/16″ – or about 1.5mm) before the thread starts to pull out further.

3.  Take note of the number where the deflection is about 1/16″.  This is where your tension will normally be “right” for the majority of your sewing.

Here’s a video of what I’m describing here:

Fast tension test – this works on most machines, not just vintage

If the tension doesn’t behave this way, then it likely has been / needs to be adjusted.  If that is all about right, and the tension problem still hasn’t gone away, I would say it’s time to look at the bottom tension.

If by the time you reach 3 -5, it hasn’t changed at all or only a tiny bit, chances are one of 2 things has happened:

  • There’s fluff, old oil, debris, or small kittens in the tension disks. Try running some dental floss through to clean out the garbage. I’ve also been known to turn the tension dial to 0 (or make sure the presser foot is up) and gently spread the disks and blow out any debris I see.  This is also good for a visual inspection after running the floss through.  This obviously works better for the exposed, external tensioners than the ones that are integrated.
  • The thread isn’t right into the tension disks – try this:
  1. Thread the machine up to the tension disks with the presser foot up.
  2. Thread through the disks, then drop the presser foot
  3. Grab the threads going into and out of the tension disks, and give them a gentle tug upwards.  This is right for most vintage machines.  If your tensioner isn’t exposed, try to push the thread in as far as possible. For instance, I will usually hold the thread before the tensioner, then pull the thread after it leaves the tensioner.  This usually has same effect as doing what I suggested above for exposed tensioners.  This will make sure that the thread is fully seated. I used to have a lot of weird tension issues with some machines before I started doing this.
  4. Raise the presser foot, and continue threading the machine.
  5. Do the tension tests above again and see if the result is different.

If the tension is really tight right from the get go, or the needle starts to deflect significantly between 0 and 3, one of 2 things has likely happened:

  1. Somewhere in the thread path, the thread has become caught on something that’s not letting it move freely.  Check and double check your routing and make sure the thread isn’t hung up on anything.
  2. Your tensioner has more than likely been adjusted incorrectly.  We’ll address this in a later article.  In the meantime, many vintage machine owners can benefit from this link on the “Tools for self-reliance” website – note, it’s a PDF file.
    This PDF addresses the Singer machines, but the clones (Many of the Made in Japan machines from the 50 – 70s) will work too, it just takes a little imagination to see how some of the parts were redesigned.  2016-10-21 The manuals from TFSR are offline at this time.  They can still be found at:

This is the simple test I do to machines first when someone complains of tension.  After that, I get more accurate.

Did this help?  Raise more questions than it answered?  Let me know below, we’ll get you sorted out.

Checking Bottom Tensions


16 thoughts on “Fragile Tension – Tension does not have to equal stress (Updated with a video)”

  1. Just want to say “Thank you” for your youtube about assembling the upper tension. I just bought a machine, they didn’t want it because the tension was always “messed up”. I turned it and wiggled it and it pretty much fell apart in my hands. I was scared when I found an extra piece in there that I haven’t got on my other machine – then there was your youtube – it showed me how to put together ALL the pieces. My machine still needs a bit of adjusting to be perfect, but at least it sews now. You are a wealth of knowledge and I thank you!

  2. Thanks for clear language & videos. I’m 63, been sewing since age 16 & ,only now beginning to not fear tension problems. I even threw machines in trash due to tension, gee. Please keep up the good work, much needed info.

  3. Thanks so much for all your vids about the singer slantomatics! The language used in the service manuals might as well be written in another langugage as far as I am concerned. Your vids saved me so much time and money 🙂

    1. Service manuals are written for technicians. There’s a lot of assumed knowledge and experience when they’re written. (Pfaff and Bernina manuals are some of the worst I’ve seen!) Which of course makes them a real pain for the rest of us!

      The vehicle service manuals that I’ve seen ( and owned) are pretty much the same. 😉 I’m glad the videos have been helpful.

    1. Hey Joe and Elaine! Realistically, a non-numbered top tension doesn’t have a “stop” either. you can twist and twist until the knob comes off or compresses the spring into a flat piece of wire. Because of that, there’s no true “adjustment” as far as what a technician would do. “0” would still be where there’s a barely perceptible tension on the thread as compared to with the presser foot up, but there’s no way to mark it, so it’s basically moot to do it.

  4. I am trying to figure out tension / stitching issues. My FW is a pre-war and the tension dial does not have the numbered cap. I’ve read some older ones didn’t have it. So I’m not sure when trying to do tension how you figure out when you are at a “4” tension etc. So then not sure when you reset it to zero and then try to redefine where it should be. I got it to make resemblance of stitches once – but tension still wasn’t correct. thanks in advance for any advice.

    1. Hi! There are 2 things you can do in this case:
      1. Set your bobbin tension first, and Replace the upper tensioner with the newer style, and set it like in this article. This is obviously not period correct, but may cause less frustration.
      2. Set your bobbin tension first. With a non-numbered dial, everything is “ball park” anyway. There’s almost no way to test the 4 or the 0, etc. That said, there’s no adjustment to be made to make it accurate or not, just the adjustment the “user” makes to compensate for the threads they’re using. What we’re doing with the numbered dials is setting the stops to reflect a good range of adjustment. There are no stops on the pre-war tensioners.

      You didn’t mention what was wrong about the tension. Thread it up with 2 different colors of thread and let me know what both are doing? Then I can give you a much better idea of what’s wrong.

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