How To Adjust Serger Tension – Troubleshooting for Beginners

How to adjust serger tension. No matter what kind of overlocker you have you should learn how to adjust needle and looper tensions for a perfect finish.

Hey y’all, today we’re going to be talking about serger tension and how to troubleshoot it. Sewing machine tension in general can be a difficult concept, and when you multiply it by the 4 threads in an overlocker, it can get more frustrating. So today I’m hoping to take some of the mystery and frustration away and help you understand your thread tension on your serger.

As a review, tension between threads needs to be in balance in order to form proper stitches. Take a look at this post about regular sewing machine tension if you don’t have a firm grasp on that concept; I’m told the demonstration in the video has helped a lot of people understand. To summarize, think of it kind of like an equally matched tug of war. Each side is putting the same amount of pressure on the rope (thread) so none of it gets pulled out of balance.

I discuss thread tension in the video below, which you can also watch on YouTube here if it won’t load below for some reason.

Balanced Tension

Below is an example of what balanced stitch with correct serger tension looks like. I threaded my machine with 4 different colors of thread to make it easier to see which thread is doing what. The left needle is yellow, the right is red, the upper looper is green and the lower looper is light blue.

When your tension is balanced, you should see the upper looper threads and lower looper threads meeting at the edge of the fabric and not extending beyond it, or pulling on the edge of the fabric and creating puckers. The needle threads should look like straight lines on the right side, and like small dots on the wrong side. Zooming in to this image I could probably tighten my left needle (yellow) thread just a teeny bit as the dots on the wrong side are a tiny bit bigger than the red ones. However I couldn’t see this with my eyes in person, it’s only evident to me on the close up.

Practice On Scrap Fabric

Now that you know what balanced tension looks like, know that some overlockers can be very particular about tension. And it can need to be tweaked for every new fabric or type of thread. So I strongly recommend using scraps of your actual fabric and as many layers of fabric as you will be sewing to check your tension before you start sewing your project. That way you can tweak any settings that need to be adjusted before you make a mess.

If your scrap fabric test reveals unbalanced tension, and you don’t know what to do to fix it, I suggest taking the following steps to make tension adjustments :

1. Rethread your machine with different colored threads. Make sure you do this in the correct order, and that you release the tension as you are threading.
2. Set all your tension dials to the midpoint of the suggested tension range. For example, if your machine suggests tension between 3-5, set all the dials at 4.
3. Stitch your scrap fabric.
4. Evaluate thread tension in the same order that you threaded. So on my machine I would begin with the upper looper, then lower looper, then right needle, then left. Adjust one dial at a time as needed and sew another line of stitching on scrap fabric after each adjustment.

Changing the Looper Tension

So as mentioned above, we’ll start with the upper looper as that’s the first thread on my machine. Here’s what the upper looper looks like when the tension is too loose. Notice how the green threads extend beyond the edge of the fabric, but the blue ones don’t. It is possible to have both the upper and lower looper thread too loose (or too tight) but again, work on one thread at a time. So in this case I’d tighten the upper looper, or move it to a higher number.

Conversely, if you tighten too much, your fabric would look like the image below. Notice how we can now barely see the thread loops of green thread. Also notice that the blue lower looper thread is pulled onto the right side of the fabric. To fix this you’d need to loosen the upper looper tension, or move it to a lower number.

And as we move to the lower looper, below is what it looks like when the tension is too loose. Notice the lower looper thread visible on the right side on the fabric and extending past the raw edge.

When the lower loop is too tight, it looks like the image below. In this case it’s so tight you can barely see it, even on the wrong side. It’s also pulling the upper looper thread around to the wrong side of the fabric.

Adjusting Needle Tension

Balanced loopers make it easier to see unbalanced needle threads, which is why I suggest getting the looper tension right first. Once that is done, you can see below what it looks like when the right needle tension is too loose. It’s hard to tell on the front side, but flip it to the wrong side and you can clearly see how loose the red thread is.

And when it’s too tight, as in the image below, it first pulls the lower looper thread onto the right side, and then stops catching the lower looper thread at all. You can see the blue looper thread between the red stitches on the right side and then the red thread pulls.

Similar things happen with the left needle when it’s too loose, but it’s more visible on the right side. ON the wrong side the yellow loops are all over the place.

And seen here, the left needle tension is too tight and, like the right needle, eventually stops catching the looper thread on the seam.

So in summary, here are the steps to troubleshooting serger tension:

• Re-thread your machine with different colored threads, making sure to do it in the correct order. This eliminates improper threading as the issue.
• Look for the thread where it doesn’t belong. For example, if lower looper thread is visible on the right side, it’s too loose. Threads visible where they shouldn’t be usually indicates tension that is too loose.
• Look for thread not visible where it should be. For example, a too tight needle thread might not be visible at all on the wrong side of the fabric, when you should be able to see dots of the right needle thread. Thread not visible where it should be usually indicates too tight tension.