Overlock Sewing Yarn: Your Ultimate Guide to Choosing the Right Thread

If you’ve recently ventured into the world of sergers, you’ve likely discovered that they operate quite differently from your standard sewing machine. One of the most common questions from new (and even experienced) serger users is about thread. What is overlock sewing yarn? Is it different from regular thread? And how do you choose the right one for your projects? Understanding the answers to these questions is the key to unlocking the full, professional potential of your overlock machine.

This guide will demystify overlock thread, explaining its purpose, the different types available, and how to select the perfect one for any fabric, ensuring your finished seams are both beautiful and durable.

Why Sergers Need Specialized Thread

First, let’s clarify the term “yarn.” In the context of serger thread, it doesn’t refer to the thick yarn used for knitting. Instead, it denotes a specific type of long-staple, high-sheen thread that is engineered for high-speed sewing. Your domestic sewing machine might use one needle thread and one bobbin thread. A serger, however, uses multiple threads simultaneously—often three, four, or five. This high consumption rate means the thread needs to be smoother and finer to prevent jamming and to feed evenly from the cone.

Using standard sewing thread on a serger can lead to a host of problems: excessive lint, thread breaks, uneven seams, and unnecessary wear on your machine. Overlock sewing yarn is designed to be lightweight, strong, and produce minimal lint, making it the ideal choice for the fast-paced, precise work of an overlocker.

Types of Overlock Thread: A Breakdown

Not all serger threads are created equal. The best choice depends entirely on your project. Here are the most common types you’ll encounter:

1. polyester Serger Thread
This is the workhorse of the serger world and arguably the most versatile serger thread available. Polyester thread offers excellent strength and a slight stretch, making it perfect for seaming modern knit fabrics like jersey, interlock, and ponte. It is also colorfast and resistant to shrinking, ensuring your seams remain intact and vibrant after washing. For most everyday sewing, from garment construction to finishing woven edges, a good quality polyester overlock thread is a perfect and economical choice.

2. Nylon Overlock Thread
Nylon thread is known for its incredible strength and thinness. It’s often used for overlocking sheer and delicate fabrics like chiffon or organza because it creates a less bulky, almost invisible seam. It’s also the go-to thread for sewing with elastic materials like lycra or spandex, as its stretch recovery is superior. A word of caution: some nylon threads can be sensitive to high heat from irons, so always test-press a scrap first.

3. Wooly Nylon Thread
This is a unique and fantastic type of serger yarn. Wooly nylon is a lightweight, fluffy, and highly stretchable thread that is typically used in the loopers rather than the needles. Its primary benefits are creating a soft, bulky, and incredibly stretchy seam finish. It’s ideal for:

• Finishing the edges of knit fabrics: It covers the raw edge beautifully and moves with the fabric without snapping.
• Creating decorative rolled hems: The fluffy nature of the thread fills out the hem, giving it a professional, clean look.
• Sewing swimwear and activewear: Its massive stretch factor makes it perfect for areas that need maximum flexibility.

4. Cotton Overlock Thread
While less common than polyester, cotton serger thread is available for purists working with 100% natural fibers. It’s excellent for finishing the edges of quilting cotton, linen, or other woven natural fabrics where you want the entire project, including the thread, to be natural. Be mindful that cotton thread has less give than polyester and can break more easily under high-speed serging if not handled correctly.

How to Choose the Right Overlock Sewing Yarn

Selecting the right thread isn’t just about fiber content. Keep these key factors in mind:

• Weight Matters: Thread weight can be confusing. For sergers, the most common and useful weights are:

  • 40-weight: A good all-purpose weight for standard seaming and finishing on mid-weight fabrics.
  • 60-weight to 100-weight: These are very fine threads. They are excellent for delicate fabrics, creating less bulky seams, and are often used for blind hemming or with sheer materials.
  • 30-weight: A heavier thread, best used for decorative serging or working with very heavy-duty fabrics like denim or upholstery.

• Color Matching: Because sergers use multiple threads, buying every color can become expensive and take up significant space. A great strategy is to serge with a neutral color in the loopers (which form the stitch on the edge of the fabric) and match your needle thread to your project. For example, use grey or white in the loopers and a matching blue in the needles when sewing blue denim. The edge will look professionally finished without requiring a perfect color match for all four threads.

• The Cone Size: Serger thread is almost always sold on large cones, not small spools. This is practical because sergers consume thread so quickly. Ensure the cones you purchase fit your machine’s spool pins. Most modern sergers accommodate large cones without a problem, but some older models might require a cone holder or a separate stand.

Pro Tips for Trouble-Free Serging

• Don’t Skimp on Quality: Cheap, low-quality thread produces more lint, which can clog your serger’s tension discs and loopers, leading to malfunctions and requiring more frequent cleaning. Investing in good quality thread saves you time and frustration in the long run.
• Keep it Clean: Regardless of the thread you use, regularly cleaning lint out of your serger is non-negotiable for maintaining perfect overlock stitches.
• Test First: Always test your stitch on a scrap of your project fabric. This allows you to perfect the tension and ensure the thread and stitch length work harmoniously with your material.

Conclusion: The Foundation of a Professional Finish

Understanding and choosing the right overlock sewing yarn is not a minor detail—it’s fundamental to achieving those coveted professional, durable, and clean finishes on your homemade garments and projects. By matching the thread type and weight to your fabric, you empower your serger to perform at its best. Ditch the regular sewing spools, embrace the cone, and you’ll immediately notice a dramatic improvement in the quality of your stitches and the reliability of your machine. Happy serging