Fixing overlocker tension

Change one tension dial at a time, sew a test and look: loops on the back mean the lower looper is loose; loops on the top mean the upper looper is loose; needle threads should sit flat.

Pinny's tip
Use four different thread colours for a test so you can see which thread is wrong.

What you'll need

• Four thread colours: to diagnose.
• Scrap of the project fabric: tension depends on fabric.

Step by step

1. Rethread completely first; most tension problems are threading problems.
2. Sew a test with four colours.
3. If a looper thread loops too much, tighten that dial a little; if it pulls over the edge, loosen it.
4. If a needle thread shows ladders when you pull the seam open, tighten that needle.
5. Change one dial at a time and re-test.
6. Note good settings for each fabric.

Common mistakes

• Changing several dials together. You can’t tell what fixed it.
• Ignoring threading. Rethread first.
• Testing on different fabric. Use the project fabric.

Watch it done

• How to Fix Overlocker Thread Tension Issues by Sew Essential on YouTube. Opens on YouTube; the video belongs to its creator.
• Serger Thread Tension: The Only Guide You’ll Ever Need, I Promise by Line of Selvage on YouTube. Opens on YouTube; the video belongs to its creator.
• How To Set The Tension On Any Overlocker by La Romi on YouTube. Opens on YouTube; the video belongs to its creator.

Sources

All checked 1 November 2026. We read these; we did not test the products ourselves.

1. Tilly and the Buttons: Troubleshooting Overlocker Stitches
2. Sew Essential: How to diagnose and fix overlocker tension issues
3. YouTube: How to Fix Overlocker Thread Tension Issues (Sew Essential)
4. YouTube: Serger Thread Tension: The Only Guide You'll Ever Need, I Promise (Line of Selvage)
5. YouTube: How To Set The Tension On Any Overlocker (La Romi)