In this article, you will learn the truth about sewing machine tension; why you should probably leave well enough alone; the three keys to balanced tension; how to troubleshoot tension; and how to adjust it if you must.
Can I be frank with you?!
I think that we sewists may be making too much ado about tension.
I could probably end this article right here with this ONE recommendation:
Step away from the thread tension dial! Leave it set where it was out of the box, usually four (4).
Okay, now that I’ve said that. You should know that proper tension is absolutely key to a lovely stitching line.
In this article, we’ll cover what tension is; why it is important; and how to adjust it when needed (which won’t be often).
Are you ready?! Then, let’s begin…
Rules of Sewing Machine Tension
Rule #1: Leave well enough alone. Keep tension regulator set to four (4), which is where it usually is from most home sewing machines out of the box!
Rule #2: If you absolutely must adjust your tension, you always want to adjust the tension in HALF increments!
How a Stitch is Made
This video shows exactly how a lovely lockstitch, or stitch, is made.
The pink bar and the gray bar represent two layers of fabric.
See how the needle thread dips down, picks up the bobbin thread, and the two threads intertwine like soul mates between the two layers of fabric to create the beautiful lockstitch.
It always amazes me that such a simple action can allow us to create and express ourselves in so many infinite ways!
Three Keys to Balanced Tension
Tension is simple. When tension is balanced, three things occur:
- The needle or spool thread is visible only on top.
- The bobbin thread is visible only on the bottom.
- And where they interlock is hidden between the two layers of fabric.
Or, here’s another way of looking at it…
The stitching line will look the same on the top side and on the bottom side.
When all of the above occurs, you end up with a lovely lockstitch!
And another thing you should know about balanced tension…
When tension is balanced, the stitching line has a bit of give, which means that your seams won’t snap, crackle, and pop when you’re flaunting your makes!
Sew easy tip: Apparently, you get a prettier zigzag when the needle thread appears ever so slightly on the bobbin side.
Correct Tension Depends On
When we talk about tension we are almost, always referring to the tension of the needle or the top thread.
And there are two things that play a part in producing a lovely, balanced stitching line. They are…
- Fabric type
- Thread weight
Sew easy tip: It is also critical that you choose the correct needle type and size for the fabric and thread you are sewing with.
Default Tension Setting
On home machines, the range for normal tension is between three (3) and five (5). Most home sewing machines are preset out of the box at four (4).
This default setting will produce a balanced stitching line when using all-purpose medium-weight 50/3 thread.
A thread labeled 50/3 means that the thread weight is 50, and it is comprised of three yarns.
As I stated at the beginning of this article, there should be few instances that require you to change the default factory setting for tension!
Four Components of Proper Sewing Machine Tension
There are four components of your sewing machine that play a role in controlling tension:
- Thread guides (the pathway through which you thread your spool thread)
- Tension disc (located inside the machine)
- Thread tension dial
- Bobbin case spring
Troubleshooting Sewing Machine Tension Problems
If your machine is not producing a lovely lockstitch, then one of the following could be the problem:
- Cheap, low-quality thread
- An old sewing machine needle that is dull or has a bent tip
- The wrong sewing machine needle type and/or size for your fabric
- The wrong stitch length for the fabric you are sewing
- An improperly threaded machine
- An unevenly wound bobbin
- Using threads of different weights for spool or needle thread and bobbin thread
So before you start playing around with the tension dial on your sewing machine, make it easy on yourself and make sure none of the above apply!
How to Test Sewing Machine Tension
Like I’ve stated previously, proper tension is the key to a lovely stitching line.
So it is worthwhile to test your tension of the sewing machine at the start of each project.
And testing your machine tension is quite easy…
- Prepare fabric scraps from your project. If interfacing is to be used, make sure to prepare the scrap as you would for construction.
- First, choose two threads that are the SAME brand and weight but in TWO different colours so that you have one for the colour in the top or needle thread and a contrasting colour in the bobbin thread.
- Next, set your stitch length to the stitch length appropriate for the fabric you are sewing, somewhere between 2.0 to 3.0mm.
- Then, take two layers of fabric scraps and stitch them together as if you were constructing a seam.
- Now, look at the stitching line produced. Use a magnifying glass if needed.
Look closely at the END of each stitch at the knots or loops.
If the tension is balanced, the spool or needle thread will only be visible on the top side. And, conversely, the bobbin thread will only be visible on the bottom.
Sew easy tip #1: However, if your fabric is very thin or lightweight, both threads will probably show on both sides even if the tension is balanced!
Sew easy tip #2: According to my Janome sewing machine manual, the tension for a zigzag stitch is perfect when the bobbin thread has the good sense to stay on the underside and the needle thread peeks through ever so slightly to the underside.
Tension Too Tight
If you can see the bobbin thread on the needle side of your fabric and/or your fabric is puckering, the needle or top thread is too TIGHT.
Tension Too Loose
However, if you can see the needle thread on the bobbin side of the fabric, the needle or top thread is too LOOSE.
How to Adjust Sewing Machine Tension
When you are ready to adjust your tension…
- Get your sewing machine manual and turn to the page on adjusting tension!
- Thread your sewing machine.
- Then, lower your presser foot. You have to lower your presser foot in order to engage the tension discs.
- Now, adjust the thread tension dial in HALF increments.
When it comes to which direction loosens or tightens tension, you have to refer to your sewing machine manual. And very often you will see stupid instructions like “turn the dial to a higher number” to loosen or “turn the dial to a lower number” to tighten.
I don’t know about you. But in my opinion, vague references to higher and lower numbers are absolutely worthless!
I’ve read different manuals for different sewing machines by different sewing machine manufacturers. And I’ve watched too many YouTube videos.
And you know what my research has revealed?!
For the love of sewing, why can’t sewing machine manufacturers do away with numbers entirely on the tension dial and just help a sewist out with plus and minus symbols?! Plus to increase or tighten tension and minus to decrease or loosen tension.
But until they catch a clue, what are we to do?
Well, first, remember that for 90% of all sewing, a tension setting between 3 and 5 will be sufficient enough to produce a pretty stitching line. The default is usually 4.
On my Babylock Presto II sewing machine…
- If upper thread tension is too TIGHT, LOOSEN the tension by turning the thread tension dial in HALF increments towards #9. And then, I retest.
- If upper thread tension is toot LOOSE, TIGHTEN the tension by turning the thread tension dial in HALF increments towards #0. And then, I retest.
Which, of course, is contrary to much of the advice I’ve viewed on YouTube!
So I recommend your test your sewing machine and figure which is which on it. To do so…
First, use one thread colour for the needle thread and a second colour for the bobbin thread.
Then, grab yourself two layers of scrap fabric, right sides together (RST), and do the following three tests:
- Set the tension to zero (0) and stitch a stitching line. Is the needle thread too loose or too tight?
- Set the tension to nine (9) and stitch a stitching line. Is the needle thread too loose or too tight?
- Set the tension to four (4). It should be balanced.
This is the best advice I can offer.
Tension is critical to creating a balanced and lovely stitching line.
However, BEFORE you change your tension from the default of 4, you should be able to say YES to all of the following:
- Have you chosen the correct high-quality thread for the fabric?
- Are you using the same brand and weight sewing thread for both the spool and bobbin thread?
- Are you using the appropriate needle type and size for the fabric you are sewing?
- Are you using a new needle or a needle free of defects?
- Are you using the correct stitch length for your fabric?
- Is the machine properly threaded?
- Have you tried rethreading the machine?
Because if the answer is YES to all of the above, it is unlikely that you will have sewing machine tension headaches.
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