If you’ve ever dealt with frayed seams, snapped thread mid-project, or bulky overlocked edges, you know that learning how to choose overlocker thread is just as important as picking the right fabric. Overlockers (also called sergers) work at high speeds and put more stress on thread than standard sewing machines, so using the wrong spool can ruin hours of work. Whether you’re hemming activewear, finishing delicate silk, or sewing heavy canvas tote bags, the right thread makes all the difference for professional-looking results. For a full breakdown of how overlockers differ from other sewing machines, check out our guide to serger vs overlock vs coverstitch distinctions.
Key Factors to Consider When Choosing Overlocker Thread
1. Thread Weight
Thread weight is the single most important factor when picking overlocker thread. Most overlocker thread is labeled with a weight number: the higher the number, the finer the thread. For example, 80wt thread is ultra-fine, while 40wt is thick and sturdy. The vast majority of home overlockers work best with 120d/2 or 40wt thread – these are balanced to handle high speeds without snapping or leaving bulky seams.
Using thread that’s too thick will jam your overlocker’s loopers and create puckered seams. Thread that’s too fine will break under tension, especially when sewing heavy fabrics like denim or canvas. If you’re unsure what weight your overlocker supports, check your manual – most brands list compatible thread weights in the specifications section.
In my 12 years of sewing with overlockers for everything from baby clothes to heavy canvas bags, I’ve found that 40wt polyester thread works for 90% of my projects. I’ve wasted money on cheap, thin thread that snapped every time I sewed a thick seam, and expensive metallic thread that jammed my loopers – stick to the basics first, and experiment later.
2. Fiber Content
Fiber content determines how well your thread holds up to washing, stretching, and daily wear. Polyester is the most popular choice for overlocker thread: it’s strong, colorfast, and works with almost every fabric type, from stretch knits to heavy woven canvas. Cotton thread is better for natural fiber projects like quilting or 100% cotton garments, as it shrinks at the same rate as cotton fabric to prevent puckered seams.
Avoid 100% nylon thread for most projects: it melts under high heat from irons, which can ruin finished garments. Wooly nylon is a specialty fiber with a fluffy, textured finish – it’s ideal for rolled hems on stretch fabrics, as it stretches with the fabric instead of snapping. For outdoor projects or items that will be washed frequently, look for UV-resistant polyester thread to prevent fading and breakage.
3. Twist and Finish
Thread twist refers to how tightly the fibers are spun together. Overlocker thread has a tighter twist than regular sewing thread to withstand the high tension and speed of sergers. A loose twist will fray and break more easily, leading to frequent rethreading (a headache every overlocker user wants to avoid).
Finish matters too. Mercerized thread has a smooth, shiny finish that glides through loopers easily, reducing lint buildup. Glazed thread has a waxy coating that prevents tangling, but avoid this for delicate fabrics – the coating can leave residue on lightweight silks or chiffons. For most projects, a matte, mercerized polyester thread is the safest pick.
4. Color Matching and Quantity
Overlockers use 2 to 4 cones of thread at once, depending on the stitch type. For basic overlocking (3-thread overlock), you’ll need 3 cones; for a 4-thread overlock or coverstitch, you’ll need 4. Buying thread in multi-packs is almost always cheaper than buying single cones, and ensures you have matching thread for future projects.
Color matching doesn’t have to be exact for overlocked seams, since they’re usually hidden inside the garment. Match the thread to your fabric’s dominant color, or pick a neutral like black, white, or beige that works with most fabrics. If you’re sewing a sheer fabric, pick a thread that matches the fabric exactly to avoid visible seams.
5. Brand Reliability
Cheap, no-name overlocker thread is tempting for budget sewers, but it almost always costs more in the long run. Low-quality thread produces excess lint that clogs your overlocker’s tension discs and loopers, leading to frequent jams and costly repairs. It also breaks more easily, wasting time and thread mid-project.
Stick to trusted brands like Coats & Clark, Gutermann, or Mettler for consistent quality. These brands test their thread for tensile strength, colorfastness, and lint production, so you know exactly what you’re getting. If you’re looking for all-purpose sewing thread options beyond overlockers, our guide to the best thread for sewing breaks down top picks for every project.
Common Overlocker Thread Types and Their Uses
All-Purpose Polyester Thread
This is the workhorse of overlocker thread, and the best choice for 90% of projects. It works with knits, wovens, stretch fabrics, and heavy materials like denim. It’s colorfast, shrink-resistant, and strong enough to handle high-speed overlocking without breaking. Keep a stash of black, white, and navy on hand for quick projects.
Wooly Nylon
Wooly nylon has a textured, stretchy finish that makes it ideal for rolled hems on t-shirts, activewear, and swimwear. It stretches up to 30% without snapping, so it moves with stretch fabrics instead of creating stiff, puckered seams. Use it in the upper looper of your overlocker for rolled hems, or in both loopers for super-stretchy seams on knit garments.
Cotton Overlocker Thread
Cotton thread is best for natural fiber projects where you want the thread to age and wash the same way as the fabric. It’s ideal for quilting, 100% cotton garments, and kitchen textiles like tea towels. Avoid cotton thread for stretch fabrics or items that will be washed in hot water, as it shrinks more than polyester.
Specialty Threads
Metallic overlocker thread adds sparkle to evening wear and crafts, but it’s more prone to breaking than polyester. Elastic thread is used for shirring and gathered seams, but only in the bobbin or upper looper (never in the lower looper, as it can jam the machine). Water-soluble thread is useful for basting, but it dissolves in water, so never use it for permanent seams.
Mistakes to Avoid When Buying Overlocker Thread
- Using regular sewing thread: Regular sewing thread comes on small spools with a looser twist, which will tangle and break in high-speed overlockers. It also produces more lint, which clogs your machine over time.
- Buying based on price alone: Cheap thread costs more in the long run due to lint buildup, breakage, and machine repairs. Spend a little more on trusted brands to save time and money later.
- Mismatching thread weight to fabric: Thick thread on delicate chiffon will create bulky, visible seams. Fine thread on heavy canvas will break under tension, ruining your project.
- Buying single cones instead of multi-packs: Overlockers use multiple cones at once, so buying single cones is more expensive and leaves you without matching thread for future projects.
- Ignoring your overlocker’s manual: Every overlocker has specific thread weight and type recommendations. Ignoring these can void your warranty or damage your machine’s tension system.
How to Match Overlocker Thread to Your Project
Matching thread to your project is easier than it sounds. For stretch knits like t-shirts and activewear, use all-purpose polyester thread in the lower looper and wooly nylon in the upper looper for stretchy, durable seams. For heavy wovens like denim or canvas, use 40wt polyester thread to handle the thick fabric without breaking.
For delicate fabrics like silk, chiffon, or lingerie, use extra-fine 80wt polyester thread to avoid bulky seams. Match the thread color exactly to the fabric, since delicate seams are more visible. For quilting or 100% cotton garments, use cotton thread to match the fabric’s shrinkage rate and prevent puckered seams after washing.
If you’re sewing sheer fabrics like organza, pick a thread that matches the fabric exactly, or use invisible nylon thread for truly undetectable seams. For outdoor projects like patio cushions or tote bags, use UV-resistant polyester thread to prevent fading and breakage from sun exposure.
Frequently Asked Questions About Overlocker Thread
Can I use regular sewing thread in my overlocker?
It’s not recommended. Regular sewing thread has a looser twist and comes on smaller spools that don’t fit overlocker spool pins. It will tangle, break, and produce excess lint that clogs your machine. Stick to cones of overlocker-specific thread for best results.
How many cones of thread do I need for an overlocker?
Most basic overlocking uses 3 cones (2 for loopers, 1 for the needle). If you use 4-thread overlock or coverstitch functions, you’ll need 4 cones. Check your overlocker’s manual to confirm how many cones your model requires.
What weight overlocker thread is best for beginners?
40wt (or 120d/2) polyester thread is the best choice for beginners. It works with almost every fabric type, is easy to find, and handles high speeds without breaking. Once you get more experience, you can experiment with finer or specialty threads.
Does overlocker thread color need to match my fabric exactly?
For most projects, no. Overlocked seams are hidden inside the garment, so a close match or neutral color works fine. For sheer, delicate, or visible seams (like on a rolled hem), match the thread exactly to the fabric to avoid visible lines.
How do I store overlocker thread to make it last longer?
Store thread in a cool, dry place away from direct sunlight to prevent fading and weakening. Keep cones upright on a thread rack to prevent tangling, and avoid storing thread in humid areas like bathrooms or basements, which can cause mold or fiber rot.
Final Tips for Choosing Overlocker Thread
Choosing the right overlocker thread doesn’t have to be complicated. Start with a stash of 40wt polyester thread in neutral colors, and add specialty threads like wooly nylon as you take on new projects. Always check your overlocker’s manual for compatible thread weights, and avoid cheap no-name brands to save time and machine repairs.
Remember: the thread you use is just as important as the fabric and the machine itself. Investing in high-quality, compatible thread will give you smoother stitches, more durable seams, and professional-looking results every time you use your overlocker.
