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Using Woolly Nylon Thread


I go against tradition when I serge bra seams. The “rules” are to either press the seams open and leave raw (if the fabric doesn’t fray), press the seams to one side and topstitch (again, if the fabric doesn’t fray), or to cover the seam allowances with a tape like 15 denier nylon bias-cut (scroll halfway down the page). Unless it’s a design detail like reverse hong kong binding, I don’t like raw raw edges on the inside or the outside of a garment. So, I wasn’t a fan of rule number one or two. Even on a straight seam, it can be difficult to sew an even length away from the seam. Can you imagine the difficultly of trying to attach tape neatly over a cross cup seam? Sure, with some practice and glue (to hold the tape in place), I’d get the hang of it over time. It’s the finish most commonly used in RTW. But if there’s an easier method, why not save myself the trouble? Enter the overlock stitch, or serge. Because of my cup size, an A or a B, I don’t stabilize the cups with a non stretch fabric like tricot. I usually lined cups with a classic or light weight power net or micro mesh. So an overlock stitch, which naturally stretches, makes it suitable as well as easy finish for my bras.

Normally, I use 100% polyester cone threads for serging. I choose it over 100% cotton because it has more give. I haven’t had a problem, but I’ve read that woolly nylon thread is a better choice for stretch fabrics. As the name suggests, woolly nylon is made from nylon fibers, which results in a thread that stretches and recovers, provides more coverage and has a softer touch. The increased coverage also makes it ideal for for rolled hems. It’s usually used in one or both loopers, but can be used in all four. Being more expensive than regular thread, I wondered if the extra money was worth it. Does woolly nylon thread really make a difference? Here’s what I found.

First, I’ll clarify that I’m using a 3 thread overlock using YLI woolly nylon. This is the type of stitch I use to both sew and finish lingerie seams. Also, my serger is a Juki MO-654DE.

woolly nylon-1


100% Polyester:

My standard serge for lingerie. The differential feed is set to normal, and the stitch length is set between 1 and 2. I reduce the stitch length to provide more coverage. I have found this to help prevent lace from “poking out” of the serge. All tensions are set to 4. I apologize that the serge is slightly messy. My Juki was acting up.

woolly nylon-2

Wooly Nylon in Lower Looper:

Woolly nylon can be difficult to thread because it separate easily. It’s very similar to knitting yarns. To make threading easier, I tied off the woolly nylon with the polyester thread and pulled through. I had to adjust/loosen the tension of the lower looper to 3 in order to get a balanced stitch. The differential feed, stitch length, and other tensions stayed the same as in the 100% polyester.  Do you also notice how the woolly nylon looks “fuzzy” compared to the 100% polyester?

woolly nylon-3woolly nylon-5

Wooly nylon in Both Loopers:

Again, to avoid a threading fight with the Juki, I tied off the woolly nylon with the polyester thread and pulled through. Just like the lower looper, I had to adjust/loosen the tension to 3 in order to get a balanced stitch. The differential feed, stitch length, and other tensions stayed the same as in the 100% polyester. 

woolly nylon-4


Is it worth the extra money? Will I be using woolly nylon in the future? Totally, but not for the same reason as other sewers. Many claim that they use woolly nylon because of its hand; that it’s softer against the skin. IMOH, I wouldn’t notice a difference. I would use it for its coverage. I have a problem with the lace “poking out” of the overlock, which is why I reduce the stitch length when using polyester thead. With is increased coverage, woolly nylon encases the lace edges inside the serge, making for a clean finish. I love pretty seam allowances, don’t you?


Because wooly nylon is more expensive than your average thread, finding an inexpensive resource online with low shipping rates is your best bet. Buy in bulk to save on paying multiple shipping fees. This is assuming you don’t have a local vendor that stocks it.
YLI Wooly Nylon Thread via Amazon – $4.99
Fleishmans in Philadelphia – $5.90
Wawak – 1+ $4.10 / 4+ $3.99
Thread Art – $2.99 (not sure about quality)

Have you used woolly nylon thread? If so, then what was your experience? Do you have any tips?


  1. Reply

    Roseana Auten

    Sometimes I have found YLI Wooly Nylon to be a little scratchier, much to my surprise.

    • Reply


      Interesting! Thanks for sharing!

  2. Reply


    Your serger on a bad day sews better than mine at its best – I can’t get mine to behave at all on bra fabric! I’m currently saving up for a new serger, and I have my eye on the Juki MO-654DE. Do you recommend it?

    • Reply


      I highly recommend the Juki serger. When I bought it, I didn’t have enough money to spend $1000+. I read several reviews online and this model seemed like a workhorse despite the price. It has proved to be one. I’ve never had an issue!

  3. Reply


    My tip: don’t iron a woolly nylon seam…. I’ve found it has a very low melting point!
    I disagree that woolly nylon is anything like “knitting yarns.” First of all woolly nylon is barely spun, and even single ply yarns are spun with a slight twist. Most knitting yarns are made up of 2 or more plies and the variety of the fibers and spinning methods would negate them being lumped together in comparison.
    I think the tension on your swatches looks pretty great… perhaps my Brother is due for a tune-up (or replacement).
    Oh, and I was wondering about your use of the word “serge” as a noun… I’ve always used it as a verb to describe the type of seam finish, not as a replacement for the word “seam”. Terminology differs across the industry (and the world) so I’m curious about that.

    • Reply


      Noted about the low melting point! I hope you’re not speaking out of personal experience : )

      When I wrote that woolly nylon is like knitting yarns, I didn’t mean that their production processes were the same. I meant that when compared to polyester thread, it has a fuzzier texture.

      When I worked in the industry, we used the terms serge and overlock interchangeably as both a noun and a verb. Good question!

      • Reply


        I’m also in the industry and we use “merrow” most frequently as a verb in place of “overlock”. I believe a “merrow” machine is actually a brand name that… as is a “Serger.”

  4. Reply

    Natasha Estrada

    I don’t use the knife on my serger much anymore I swivel it out of the way and pretrim my seams and I’ve found for me I get better results. Though not sure I would calling serging the cup seams rule breaking but I don’t acknowledge the rules to begin with.

    • Reply


      Hmmm… I wonder why you get a better serge when there is no knife. What are your thoughts?

  5. Reply


    Wooly nylon is also fantastic for firmer knits or woven fabrics with a slight stretch- you can sew using a straight stitch, and you don’t need to worry about popping seams.

    • Reply


      Thanks for the tip!

  6. Reply

    Anna Katherine

    I’ve used it multiple times to sew leotards. Every joining seam in a leotard (even the ones at the Olympics) is held together by 4-stitch woolly nylon thread (and other seams turned and finished with a coverstitch of woolly nylon). It can be a pain – I recommend allowing for some excess fabric to be cut off as you serge, to get the nylon to ‘grip’ the fabric better. But it’s strong stuff!

    • Reply


      Interesting the way woolly nylon is used for the Olympics. Thanks for sharing that info!

  7. Reply


    I used it wooly nylon when making my first Watson last week. I used it in the upper and lower loopers on a 4 thread overlock stitch – it worked great!

    • Reply


      That’s how I used it and I agree that it works and looks great!

  8. Reply


    I noticed that you did not use the wooly nylon in only upper and lower looper. So, definitely don’t use it in the needles? Or have you found that it will work in them as well? I am trying it and can’t seem to get the right tension. This is my first time sewing with wooly nylon.

    • Reply


      *only used in upper and lower.
      But not the needles.

      • Reply


        Sorry, I was really tired when I wrote this and now I need to clarify. Thead the wooly nylon only in the upper and lower looper and not in the needles? Thanks 🙂

  9. Reply



    Wooly nylon is perfect when using in rolled hem. Try to use it on upper looper, tighten tension on lower looper, and stitch lenght set to little above 1 – you will have perfectly coverd roll hem by the thread – very nice end finish.

    Greetings from Juki team !

    • Reply


      Thanks for the tip Adam! Tell the team I say hi!

  10. Reply


    I use wolly nylon in swimwear but only in the upper looper. I also use it in the bobbin.

  11. Reply

    Roseann Chase

    Woolly nylon can be purchased at http://www.uncommonthread for 20% off retail every day

  12. Reply

    Mary K

    I use the woolly nylon to finish baby receiving blankets … makes a nice, soft edging. Also, I did try the Thread Art version of this … not nearly as good as the YLI, IMO.

  13. Reply

    Catherine Elhoffer

    Omg I love seeing Wooly Nylon getting some love!!!!

    So I have a babylock overlock/coverstitch combo and I used wooly nylon in both needles and loopers. When making anything with spandex blends, using it in all four spots for overlock makes it REALLY hard to break the seams, due to all the stretch. I make leggings, skater dresses, and more. I started using it in all four spots after looking at Black Milk’s clothing (they make pricier spandex clothing, but they fit like a glove), and they use black wooly nylon on everything, including all three parts of the coverstitch. My clothing is so much nicer now and I never get popped seams. I make a lot of my own clothing, and I’ve worn one skater dress easily 50 times, washing it every time, and it’s held up phenomenally.

    Using it can be a pain sometimes, as threading machines can be frustrating. I’d recommend investing in a Looper Thread to help with your looper threading (shocking), and for the needles a Machine Needle Inserter and Threader pushes wooly nylon through brilliantly. Invest in those tools and you’ll be flying through clothing. And I recently started using it in my rolled hem, and holy cow it looks like a rolled satin stitch.

    (My babylock auto adjusts and I’ve never had any issue with that machine. But she’s like $8k so I know a lot of people can’t invest in her!)

    • Reply

      Jeanie Cutler

      Hi Catherine,
      Great to see your comments about using Wooly Nylon in all 4. I have done it with great success in the past but then I started having tension issues, so after searching for hours on the web I could only find posts saying to only use wooly nylon in the loopers (but I’m still having tension issues). What would you suggest for the settings on tension discs, stitch length & differential feed please? I don’t have the same machine as you do but anything might help. I have a Janome Magnolia serger and Janome CoverPro 1000cpx coverstitch machine. I’m trying to make a swimsuit. (Emphasis on the trying).

  14. Reply


    This is exactly the resource I was looking for, thank you!

    It sounds like you used wooly nylon on both loopers — so did you use standard polyester server thread on one or both needles?

  15. Reply


    Hi there, great post. I’m a beginner though, and have no experience whatsoever with sergers. I was wondering what kind of machine you’d advise me to buy as a first? Specifically for lingerie because it’s all I really ‘try’ to make.

  16. Reply

    Susan Care

    Hi, I’m having problems hemming stretch lining fabric on a skirt and came across your advice. Do you have any tips for this sort of hemming? When I’ve done a rolled or narrow hem with my serger and then pulled the fabric to test it, the resulting effect is that it does that lettuce edge thing, not what I want!! Love your website by the way!

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