Choosing the correct thread thickness is a fundamental condition for high-quality sewing equipment. Many beginners and even experienced craftsmen often underestimate the influence of this parameter on the result, relying solely on the strength of the material. However, incorrectly selected thread thickness for sewing machines inevitably leads to breaks, skipped stitches, and even breakdown of the shuttle mechanism.
When operating the equipment, it is important to understand that thread density must match not only the fabric, but also the size of the needle. Ignoring this rule turns sewing into a struggle with equipment rather than a creative process. In this article, we will take a detailed look at the numbering system, quality control methods, and technical nuances that will help you avoid common mistakes.
The modern market offers a huge range of sewing accessories, from the finest silk to the strongest technical fibers. It is almost impossible to understand this diversity without a clear understanding of the physical properties of the thread. This is why knowing the markings and knowing how to select the appropriate needle is a key skill for anyone who works with textiles.
Numbering systems and thread markings
The first thing a user encounters when buying a reel is the mysterious numbers on the label. In the world of textiles, there are several systems for designating thickness, which often causes confusion. The most common is the metric system (Nm), where the thread number indicates the length in meters contained in one gram of weight.
The higher the metric number, the finer the thread itself. For example, Nm 40 thinner than Nm 20. This is logical: from one gram of raw material you can pull out more meters of thin thread than thick one. However, you can often find other designations on reels, such as Tex or Denier, which work on the opposite principle or use different units of measurement.
On American reels, double markings are often found, for example, 40/2. Here the first number indicates the thickness of a single thread, and the second number indicates the number of threads twisted together. For household sewing machines, the most universal option is the thickness 40-50 in the metric system, which is suitable for most standard operations.
⚠️ Attention: Never use threads marked “For hand sewing” in a sewing machine. They have a fleecy surface and insufficient tensile strength at high speeds, which will lead to constant breaks and clogging of the shuttle.
What do the colored dots on the reels mean?
Colored dots or circles at the end of the spool (green, yellow, red) indicate the color fastness of the thread to various influences: washing, boiling or dry cleaning. This has nothing to do with thickness, but is important for the durability of the product.
Correspondence of thread thickness and needle size
The golden rule of sewing is: the thickness of the thread should correspond to the size of the needle. If the needle is too thin, the thread will not be able to pass freely through the eye, causing tension and breaks. Otherwise, when using a thick needle with a thin thread, there will be too large a hole in the fabric, and the stitching will look sloppy.
To make the correct selection, you must rely on standard correspondence tables. For example, for threads with a thickness of 40-50, needles of sizes 75-90 (according to the European system) are optimally suited. For denser materials and threads number 30, 100-110 needles will be required. Thin fabrics with 60-80 thread are sewn with 60-70 needles.
It is important to consider that eye of the needle should be wide enough so that the thread fits into it without effort, but does not dangle. As the thread passes through the fabric, it heats up due to friction, and if the gap between the needle and the thread is minimal, this can lead to the synthetic fibers melting.
☑️ Checking needle and thread compatibility
Below is a detailed table that helps you quickly navigate the choice of a needle-thread pair for various types of work.
| Type of fabric / Work | Thread thickness (Nm) | Needle size (EU) | Recommended needle type |
|---|---|---|---|
| Silk, chiffon, organza | 60-80 | 60-70 | Sharp |
| Cotton, linen, blouse fabrics | 40-50 | 75-90 | Universal |
| Jeans, suit fabric | 30-40 | 90-100 | Jeans |
| Leather, thick drape | 20-30 | 100-110 | With rounded point |
The influence of thickness on stitch quality
Why is accurate calibration so important? If the thread is too thick for the machine and fabric, it will get stuck in the needle plate. This causes sharp jerks in the fabric, displacement of the rack teeth and, as a result, a violation of the stitch length. The machine begins to “chew” the material, and a characteristic “beard” of tangled loops forms on the underside.
On the other hand, an excessively thin thread cannot provide the required density of the layers. The stitching turns out weak, easily rips apart and is visually lost on thick fabric. In addition, a thin thread paired with a thick needle does not fill the puncture, leaving the fabric vulnerable to further destruction of the fibers along the seam.
Check the upper thread tension after changing the thread thickness. Even with the correct needle, the tension adjuster may need to be adjusted for the new thread diameter.
Particular attention should be paid shuttle mechanism. In modern machines with a horizontal shuttle, the gap between the nose of the shuttle and the needle is minimal. Using threads of increased thickness (for example, decorative threads) in such machines without changing the needle and presser foot often leads to the shuttle hitting the needle, which can lead to expensive repairs.
Specifics of working with decorative and thick threads
Decorative seams, embroidery and finishing work require the use of threads that are much thicker than standard ones. These can be floss threads, iris threads or special decorative polyester threads. You cannot sew with them with a regular needle - they simply will not fit into the eyelet or will tear on its edges.
For such purposes, there are special needles with an enlarged eye and a special groove, which allows the thick thread to sink better into the fabric without forming a loop on top. Often when working with such materials, the top thread is not threaded into the needle at all in the standard way, but a special thimble is used or a thicker carrier thread is threaded into the needle.
- 🧵 Use needles marked "Embroidery" or "Metallic" to work with decorative threads.
- 🧵 Loosen the upper thread tension to a minimum to avoid breaks and knots being pulled.
- 🧵 Reduce your sewing speed as thick thread requires a smoother passage through the fabric.
Otherwise, the “thread in a thread” method is used, when a thin thread is threaded into the eye, and a thick thread is tied to it and pulled through.
Problems and their solutions in case of incorrect selection
How can you tell if the thickness of sewing machine thread is chosen incorrectly? The machine itself will tell you this through the nature of the sounds and the appearance of the seam. If you hear a thud or squeaking sound in the hook area, this is a sure sign that the thread is stuck. Visually, this manifests itself in the form of loops on the underside of the fabric or frequent breaks of the upper thread.
Another common problem is skipping stitches. This occurs when a needle with a thick thread cannot form a loop in time to be picked up by the shuttle due to the resistance of the material. In such cases, it is necessary to either reduce the thickness of the thread, or increase the needle size, or change the type of point.
⚠️ Attention: If the thread constantly breaks with a characteristic “pop”, check whether the edge of the hole in the needle plate is burred. The thick thread could have damaged the metal in a previous jam.
To troubleshoot problems, try the following steps: replace the needle with a new one (a dull needle breaks any thread), blow out dust and fuzz from the shuttle compartment, and also check the thread path for burrs on metal parts. Sometimes the problem lies in the poor quality of the thread itself - uneven thickness along the length also causes failures.
Thread material and its influence on the choice of thickness
Thickness is not the only parameter. The thread material (cotton, polyester, silk, viscose) dictates its conditions. Synthetic threads (polyester), with the same thickness, are stronger than natural ones and have some elasticity. Therefore, synthetic thread No. 40 can be used in a wider range of fabrics than cotton thread of the same numbering.
Cotton threads are less elastic and can break under strong tension if the fabric stretches during wear. For knitwear and elastic fabrics, it is better to use threads with the addition of lycra or completely synthetic ones, choosing them so that they do not pull the seam. Not only thickness is critical here, but also stretch factor.
For elastic fabrics (knits, stretch), always choose threads with added elastane or all-polyester, even if their number is the same as their cotton counterparts.
When working with viscose embroidery threads, be aware of their low tensile strength compared to polyester. They cannot be stretched too much, so thickness selection is often skewed towards denser options to compensate for the softness of the material, but this requires very careful machine tuning.
Frequently asked questions (FAQ)
Can I use #10 thread on my sewing machine?
Thread No. 10 (very thick, "Iris" or darning type) is intended mainly for hand sewing, embroidery or knitting. It is not recommended to thread them into a standard household sewing machine, as they can get stuck in the mechanism, damage the hook or break the needle. There are special thick threads for machines, but their use requires specific settings.
Why should the bottom thread be thinner than the top thread?
In a classic sewing pattern, the bottom (shuttle) thread is often taken thinner than the top thread so that the weave knot is hidden inside the fabric and does not protrude onto the front side. However, when using modern elastic fabrics and quality machines, this rule is not absolute, and the thicknesses may be the same.
How to determine the thread number if the label is lost?
It is difficult to visually determine the exact number, but it can be compared with a known standard. Thread the thread into the needle: if it enters with difficulty and requires pushing, it is too thick for this needle. If it dangles, it’s too thin. The best way is to weigh a piece of known length and calculate the metric number, but in everyday life it is easier to use needle correspondence tables.
Does the color of the thread affect its thickness?
The dye itself does not affect the physical thickness of the thread. However, different paint batches may have minimal differences in diameter due to the paint application technique. More importantly, cheap dyed threads may be less durable and have fluff, which makes them appear thicker in the eye of the needle.