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Understanding Thread Tension

Learn how to use the tension devices on your sewing machine and how to thread for proper tension.
Learn how to use the tension devices on your sewing machine and how to thread for proper tension.

Learn how to use the tension devices on your sewing machine and how to thread for proper tension.

Photo: Karen Meyer

by Claire Shaeffer
excerpted from Threads #78, pp. 39-41

Many sewers avoid the tension dials on their machines like the plague, certain they'll only make matters worse if they make adjustments. In fact, there's nothing very mysterious about setting and adjusting thread tensions on your sewing machine, whatever its make and model. What's potentially more confusing is that many apparently tension-related problems are caused by factors other than misadjusted tension dials. Let's look closely at how to identify and correct "tension" problems, both with and without touching the tension settings.

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Tension devices and proper threading

Tension devices and proper threading
  Click to Enlarge
You can't get proper tension without correct threading. All machines have basically the four tension devices shown here- thread guides, tension discs, tension regulator for upper thread, and bobbin-case spring for bobbin thread- which ensure that the same amount of thread flows simultaneously from the needle and the bobbin, producing a symmetrical stitch.

Meet your tension tools
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. This is accomplished by running the threads through various tension devices, including the thread guides, tension discs, and tension regulator on the machine head for the upper thread(s), and the bobbin-case spring for the bobbin thread (see "Tension devices and proper threading"-right). Some machines also include a small hole in the bobbin-case finger, through which to feed the bobbin thread to increase the tension for improved stitch definition when topstitching, satin-stitching, and embroidering, without touching your tension settings.

The tension discs and tension regulator together are called the tension assembly. The tension discs squeeze the thread as it passes between them, while the tension regulator controls the amount of pressure on the discs. On older ma- chines there are only two tension discs, controlled by a screw or knob. On newer models there are three discs controlled by a dial or key pad on the front of the machine, which can regulate two threads at once.

In either case, the tension regulator is elementary: When adjusted to a higher number (turned clockwise), the discs move closer together, increasing the amount of pressure. Turned to a lower number (counterclockwise), the discs move apart, decreasing the pressure. Using a thicker thread without resetting the dial will increase the pressure and cause the upper thread flow to decrease, unless you've got a newer machine that makes automatic upper-tension adjustments. Since the bobbin tension is not self-adjusting, the lower tension may need to be adjusted manually to match.

In addition to guiding the thread along its path, each thread guide exerts a small amount of resistance on the thread, adding to the tension from the discs to achieve balanced tension. Bottom line: Always make sure all guides are threaded before stitching.

The flat bobbin-case spring exerts pressure on the thread as it comes out of the bobbin case. The amount of pressure is regulated by a small screw at the rear of the spring. Both the spring and screw are easy to locate when the machine has a separate bobbin case. When the machine has a drop-in bobbin with a built-in bobbin case, locating the tension screw can be more challenging. Both types are shown in the drawings below. In either case, to increase the resistance, use a small screwdriver to turn the screw clockwise (to a higher number) or counterclockwise (to a lower number). Turn the screw in small increments and never more than a quarter-turn between tests. This helps you keep track of how much you're changing your settings and reduces the risk of losing this very small screw.

Bobbin cases
The bobbin-spring screw regulates bobbin-thread tension, whether your bobbin is a separate, drop-in unit (left) or is built into the machine (right).

As with the tension dials, the amount of pressure will be increased when thicker threads are run under the bobbin spring. To eliminate the need to fiddle with the bobbin-case screw, many sewers (myself included) have two bobbin cases: one set for general sewing and the other for adjusting to less frequently used threads.

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Comments (30)

Lemanczas Lemanczas writes: Great!
Posted: 5:45 am on September 5th

vlbknl2 vlbknl2 writes: Thanks for this great information.
I also recently bought a document, it was very good on this issue :
Posted: 12:40 am on March 18th

quecome quecome writes: There's a good video explaining this...
Posted: 7:11 am on September 22nd

JennyRichards1 JennyRichards1 writes: Brilliant job of explaining how tension works. Thank you.
Posted: 2:51 am on May 16th

ThomasGops ThomasGops writes: In diet continue with the protein rich diet and foods like cereals, lentils, tofu, peas, fresh cheese , soya ,sugar and rice. Here's an example of how the timing approach works:. So her diet would include 1219 calories (using example #1) or 1380 (using example #2) + an additional 40%. Spiropent is a brand name for the chemical Clenbuterol Hydrochloride or Clenbuterol HCL. Need not stick to 8 hours as you might not need that long to feel great.
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Posted: 11:18 pm on May 5th

daniellacin daniellacin writes: I remember how I use to "play" with my mother's sewing machine settings and then she would get annoyed when she would notice her thread tension went haywire. Now I totally understand why! Thank you for sharing!
Posted: 9:13 am on February 18th

user-3436137 user-3436137 writes:
Posted: 2:14 am on May 23rd

Alekxechka Alekxechka writes:
Posted: 3:20 pm on December 22nd

user-2698071 user-2698071 writes: I had a problem with top threads breaking.
Solution: My machine held the spool horizontally (not vertically) and when I used a larger spool, the end cap that held the spool in place was too small. It allowed the thread to catch in the little slash on the rim of the spool and everything stopped.
When I used the larger end cap (supplied with the machine)the problem was solved.

Posted: 10:10 am on December 13th

TTAntone TTAntone writes:
Posted: 10:33 am on October 3rd

TTAntone TTAntone writes:
Posted: 6:20 am on October 3rd

Riccarsewer Riccarsewer writes: Attention to all,
I am need of some assistance. Some many years ago I purchased for my wife a Riccar 800 sewing machine. she has been trying to use it lately and the bobbin will not thread. The needle thread will catch the tip of the shuttle hook and the tip of the shuttle race holder. HELP! Can someone out there please assist me?
Posted: 10:02 am on July 29th

dsantil71 dsantil71 writes: I learned about using the right size needles for specific fabric, right type of thread for specific fabric such as polyester for polyester fabric & cotton for cotton fabric, not to use old or cheap thread not just color, even how to hold the fabric as it goes thru the machine matters but I could never get the tension right. I even learned about maintaining it regularly, using a new needle for every project but this is the first time I have learned this much about tension! I don't understand what you mean about how to "floss" between the tension discs. I'm not even sure where they are exactly and how to get to them. Can you give me for information on that please?
Posted: 1:48 pm on June 2nd

rshirt rshirt writes: My problem doesn't really seem to be thread tension. My foot sits too firmly on the fabric, I think! I have a skirt with one side shorter than the other because of the foot's movement or lack thereof on the slick fabric--any suggestions on how to deal with that?
Posted: 12:29 pm on March 15th

Sunshineliz Sunshineliz writes: Thank you so much! My machine has been driving me crazy and finally I have fixed the tension. Thank you for the tips on the bobbin tension.
Posted: 1:00 am on December 28th

mlssfshn mlssfshn writes: If both tensions are to loose and the stitch looks perfect how is the seam compromised?
Posted: 7:36 am on May 7th

nalax nalax writes: Thank you!! Excellent information!

Posted: 7:38 am on December 1st

cocoon_bobbins cocoon_bobbins writes: Interesting read about a little discussed topic on web blogs. I was not familiar with "thread tension" and so just learned some valuable information, thanks.
Posted: 3:34 am on November 7th

Grandytoon Grandytoon writes: How timely! Tomorrow, I will be teaching a homeschool sewing class of 12 and 13 year olds the parts of a sewing machine and how to use them. Thanks so much. I found this on Pinterest this evening and will use it during my class.
Posted: 5:40 pm on September 28th

SouthPawArtistry SouthPawArtistry writes: Thank you so much for this post on tightening the bobbin case screw. You made my day. I have been trying to fix my sewing machine for awhile. I kept reading the same info over and over, until I read this. Yay I'm so's fixed!
Posted: 6:03 am on August 23rd

SewingTina SewingTina writes: This article was perfect and exactly what I needed. I saved this as one of my favorites for future reference. Thanks.
Posted: 10:10 pm on January 8th

happy273 happy273 writes: I have a 1662 singer sewing machine and i can not get the bobbin thread to thread to top thread. I have cleaned machine. reread manual to make sure bobbin is thread correct and also that machine is threaded correctly. All are correct I loaded the bobbin it will not catch when i rotate the needle. It always did before now it just does nothing what i notice is the case doesn't rotate any more. It is a plastic case.

Please help
Posted: 11:34 pm on December 9th

AnotherSewingSue AnotherSewingSue writes: For the other Sue...

It sounds like your machine's timing is off - I had that problem with one of my antique Singers, it didn't matter what I did, it broke thread or knotted severely.

Not willing to throw my 1924 model 66 in the trash, or send it to Goodwill where I rescued it from, I looked around until I found a shop that would work on it. it turns out... one of the lower arms bearings were loose, which made the bobbin case run just slightly out of time.

Now, your babylock (I hope!!!) isn't as abused or old as this machine, but if you can't get the tension to tense right (after following the instructions on this page) it might be worth spending a few $$$ to have someone go thru it, and make sure it's timed right.

If you're lucky, you'll find a repair guy who will let you watch what he does. Not likely your machine breaks again, but if it does, yo'll know what he did to fix it. IF you're handy with tools (and can find the repair book for the machine) you'll remember what he did, and better, keep your machine running like the techs!!! ;)
Posted: 4:31 pm on October 28th

sew4sue sew4sue writes: This article is very well written and I want to thank you for it. I will print this and post it by my machine.
I have a Baby Lock Quilter's Choice Professional on a New Joy Gold Standard frame. I have always experienced alot of thread breakage and I get so frustrated with it and will walk away from it for days. I have 6 shirt quilts to quilt and Im not looking forward to it. I was experiencing my top thread showing on back, but I finally got that balances out. Now my bobbin thread is showing on top. Ugh! I will work on balance that tonight. back to the thread breaking. I have tried different thread, different needles. I have threaded, unthreaded and rethreaded to no avail. I keep having the same issue. Im almost convinced now, it may be the way the thread is on the spindle. I noticed that when I have the presser foot up and I pull the thread thru, that it is smooth until more thread comes off the spool, then it almost jerk and releases smooth again. Any thoughts?? If you can help solve my ongoing problem, you will have a friend for life!! THANKS SO MUCH!!
Posted: 2:47 pm on October 15th

sewingtime sewingtime writes: Hi there kaylaesq. I was having the same problems, and my instruction book didn't mention this problem, either. I thought maybe it was the thread I was using. I had a coated thread on both the upper thread and the bobbin. I think all the coating affected how the threads gripped one another. Changing the type of thread on at least one of them fixed this for me.
Posted: 6:04 pm on August 7th

ccfranco ccfranco writes: The upper thread keeps on breaking. I have cleaned and oiled the machine and I have changed the needles and the thread. I have a strong feeling that it has something to do with the tension disc and the tension dial. Though I have it on the lowest and loosest setting, it still seems like there's a lot of tension on the thread. I'm thinking this is why the upper thread is breaking. Is that possible? If so, what should I do? thanks.
Posted: 2:36 pm on July 18th

kaylaesq kaylaesq writes: I don't know if my problem is tension-related or not: when I start to sew, the stop motion knob spins free and when I lift the presser foot & remove the fabric, I find several threads @ 3 inches long looped on the bottom of the fabric instead of just a single bobbin thread. The troubleshooting list at the back of my sewing machine book does not address this problem. Could you at least identify the problem for me? If possible, I would also appreciate an explanation of how to solve the problem.
Posted: 5:07 pm on June 25th

uluky uluky writes: thanx for nice detail and clear info...i required it for my begginer usage of the machine...had funy things goin on with wound up thread appearing on the wrong side of da now gonna check list the possible problem using the exact list u gave above...wud be very interesting to try it out.thanx for guidance on dis ...will get back by Gods grace.bless ya'll
Posted: 5:33 pm on April 22nd

DjSar DjSar writes: I am so glad I came on this site. With your information on bobbin tension I have been able to fix my sewing problems!
Posted: 5:04 am on July 22nd

vasantha vasantha writes: hi i have singer 8280 machine. my problem is when i stitching the cloth in backside the thread is loose then i use tension they will correct in 8 number but in manual book say 4 or 5 is correct for stitch wat can i do plzs help me
Posted: 3:20 am on May 14th

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