Overlocker weirdism

So one thing about overlockers is that most of them come with a feature called differential feed. This lets you vary the ratio between the rate at which fabric is fed in and out of the area under the presser foot and needles. It is supposed to be a magical fix for tricky fabrics where seams won’t lie flat. If the seam is stretching out you make the inward feed faster than the outward feed, and if it gathers or puckers you make it slower.

This sounds great in theory and you can find loads of blog posts explaining it. It’s also what my machine’s manual suggests to do to correct stretched or gathered seams. But it never really works for me. I can see a small difference when I adjust the feed, but I often find I get gathered edges on lightweight fabric even with the differential feed down at the minimum. This sample is a case in point: three thread overlock seam finish on a lightweight fabric with the differential feed at 0.7 and everything else at the default settings. Awful.

Puckered overlocker edge

The problem seems to come from the needle thread; the loopers look fine. Reduce the needle thread tension, and suddenly all is well.

Flat overlocker edge

Does this happen to anyone else or is it just that my machine has overenthusiastic tension?

19 thoughts on “Overlocker weirdism

  1. I haven’t really fiddled with my differential feed. Most tension problems I have had, have come from the needle tension and just tweeking that seems to solve any problems.

  2. What make and model is your overlocker. Just about to purchase one and not sure which to get. Any advice?

    1. Hi Lynne, mine is a Frister and Rossman Knitlock 2-3-4-DP. It’s the only overlocker I have ever used so I can’t say how it compares to others, but it does everything I want for garment sewing right now (and quite a lot I don’t: I’ve never felt the need to use the two thread overlock feature) and it’s never gone wrong. It took me a while to learn how to thread it reliably but it isn’t difficult, just took a bit of practice and patience. Good luck with your search!

  3. My overlocker has settings for the differential feed, but also for the thread tension to use with different kinds of fabric. The differential feed is always the last thing I change.

  4. It may just be that finer fabrics need less tension – that’s normal. Fine fabric has less structure to hold the stitches apart, so the fabric will collapse between stitches if the tension is too high.

    That said it’s worth checking if its consistently like this – if you pull everything out (including loopers) and rethread from scratch, does it behave the same. Also check that the needle thread rolling off the cone freely and isn’t snagging anywhere. If you pull on the needle threads by hand, do they seem to be running through ok.

    I haven’t used my overlocker for a while, but from memory differential feed would give more of an even gathered effect, than the puckering you’ve got there. I only use it on knits to prevent the seams going wavy. It makes a huge difference there.

  5. Oh how interesting… I have definitely had the same sort of tension issues, and normally adjust my differential feed to either the lowest (0.6) or 2nd lowest (0.8) setting. In fact I can only remember one occasion where the default (1.0 or “normal”) setting to be right for my fabric. I’ve never even thought of adjusting the needle thread tension though – I will have to look into it!

  6. I’ve seen this issue as well. I’ve also discovered that sometimes adjusting the presser foot pressure helps as well, especially on especially thick/thin/stretchy fabrics. The differential feed dial definitely doesn’t fix everything.

  7. Still learning how to use my serger, but have noticed this. I found tweaking tension works for me most of the time. Haven’t tried a super light weight fabric yet.

  8. I have had puckering at the bottom of the side seam on 2 knit dresses recently and I was not able to solve the problem despite unpicking and playing with the diff feed on my Elna 745 (not a cheap overlocker). Now I wonder if needle tension may have been the issue and the long side seams exentuated the problem compared to the other seams. I don’t usually need to play with the tensions on my overlocker to get a balanced stitch. However, I never considered tension with respect to puckering – I’d just always alter the differential feed with mixed results. Thanks for this info I’ll be sure to try it next time I encounter a problem. PS love your blog and unique style.

  9. May I offer this link to a YouTube video? I found it very informative and I hope that you will find it helpful. There may even a be a specific video for your machine, too.

    Kind regards,


    1. Thanks Clare, that was interesting! I don’t have air threading on mine and I’d always wondered what it looked like. They do also have a video specifically for my model.

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