How to find perfect serger tension

julijadauc
16 minutes ago
3 min read

Finding perfect serger thread tension can be tricky - there are 4 threads, and knowing how to set each one of them can be a challenge (it surely was for me!). In this post, I want to share a tip that finally helped me understand serger thread tension - and it might be even easier than you think!

This post is created in partnership with Brother and all samples are sewn using Brother Airflow3000 overlocker. As the name suggests, this serger has air threading system, which makes threading looper threads as simple as a push of a button.

Brother Airflow 3000 overlocker with air-threading system

Now let's discuss how to find that perfect serger thread tension:

How to find perfect serger tension

To find perfect serger thread tension, try using what I call the 'Opposites rule'. This rule sounds like this:

High tension -> less thread in the seam
Low tension -> more thread in the seam

To help understand this Opposites rule, let's do a few visual examples. In this example, let's set tension in first needle thread to lowest setting - tension 0. With tension 0, tension discs are loose and not tensing the thread, so a lot of thread can flow into the seam. Because a lot of thread goes into the seam, the seam does not lay flat on fabric and we can see big loops.

First needle thread set to 0 tension - seam does not lay flat, visible loops

Applying 'Opposites rule': if you're seeing loops and/or seam does not lay flat on fabric, this shows there's too much thread in the seam, tension is too low, and to fix this you need to increase tension.

Fix loops (top seam) by increasing tension (bottom seam)

Now let's do the opposite example and set tension in first needle thread to setting 9 - highest tension setting. With tension setting 9, tension discs are very tight and they are tensing thread a lot, resulting in less thread in the seam. Because less thread goes into the seam, the seam is puckering or looks gathered.

First needle set to tension 9 - seam is puckering

4th thread (looper thread) set to tension 9 - seam is gathered

Applying 'Opposites rule': if you're seeing puckering, waviness or gathers, this shows that there's too little thread in the seam, tension is too high, and to fix this you need to lower tension.

With most fabrics that I sew, I typically sew using thread tension 4 in all threads (this is medium tension setting in Brother Airflow 3000 serger) - this tension setting works great with most medium weight fabrics (both woven and knit).

Brother Airflow 3000 serger set to medium tension 4 setting in all threads

However, if I'm working with very lightweight or very heavyweight fabrics, I will do adjustments based on 'Opposites rule' to fine-tune seam settings for specific fabric, typically staying within medium tension range, indicated on tension discs: