Anyone who has ever dealt with sewing clothes or making minor repairs on a household sewing machine has probably noticed mysterious numbers on the spools. These designations often baffled beginning craftswomen, because the quality of the seam and the durability of the product directly depend on the correct choice of consumables. Incorrectly selected threads can cause breaks, skipped stitches, and even needle breakage at the most inopportune moment.
The numbering system seems complicated only at first glance, but if you understand the logic of the manufacturers, the selection process will become automatic. There are several labeling standards that are used by different manufacturing countries, and knowledge of their features allows you to confidently navigate the assortment of any store. In this article we will analyze in detail all existing systems so that you can choose materials professionally.
Numbering Basics: Why Thick Threads Have a Lower Number
The most important principle that needs to be learned is that the number is inversely related to the thickness of the thread. In most common systems, including metric, the higher the number on the label, the thinner the thread itself. This may seem counterintuitive to those accustomed to direct numbering, but this system historically evolved from a way of measuring the length of a thread in one gram of weight.
For example, the finest silk or synthetic threads for delicate fabrics may have a number 80 or even 100, while thick threads for denim or decorative stitching will be marked 30 or 40. Understanding this rule is fundamental to preventing errors when assembling your sewing table.
However, do not forget that the reel often contains two numbers separated by a slash or a dash. The first number usually denotes the linear density, and the second the number of plies, that is, how many thin threads are twisted together to create the final product. It is the number of additions that directly affects tensile strength and the volume of the seam.
It is important to note that different manufacturers may use their own standards, which are not always the same as generally accepted metric values. Therefore, when switching from one brand of thread to another, it is always recommended to carry out test stitching on a scrap of the same fabric.
Metric numbering system (Nm)
The metric system is the most common in Europe and post-Soviet countries, including Russia. Abbreviation Nm indicates the number of meters of thread contained in one gram of weight. This means that if the reel says Nm 50/2, then one gram of such material contains 50 meters of thread twisted from two fibers.
This system is convenient because it is logical and predictable: knowing the number, you can approximately estimate the thickness. For household sewing machines, threads most often used range from Nm 40 to Nm 80. Thicker versions, such as Nm 20 or Nm 30, are intended for overlocking or decorative work.
When working with the metric system, it is important to consider that different types of fabrics have their own optimal ranges. For lightweight fabrics such as chiffon or cambric, numbers 70-80 are ideal, while for suiting fabrics and medium-weight cotton, it is better to choose 40-60.
⚠️ Attention: Using threads thinner than Nm 60 in overlockers can lead to seam rupture during operation of the product, since they do not have sufficient elasticity and strength for overcasting operations.
It is also worth remembering that the metric number directly affects the thread tension in the sewing machine. The finer the thread (higher the number), the weaker the top tension should be to avoid pulling the fabric.
English (cotton) and American systems
The English system, often referred to as Ne (Number English), historically developed for cotton threads and is widely used by manufacturers from the UK, India and some Asian countries. The principle here is similar to metric, but the units of measurement are different: the number shows how many times 840 yards are contained in one pound of weight.
The American system known as Ticket Number, often found on products from North American brands such as Gutermann or Coats. In this system, numbers do not have a direct mathematical connection with length or weight, but are simply ordinal designations of thickness. For example, Ticket #40 roughly corresponds to metric number 40, but there is no exact conversion.
The difference between the systems can be critical when ordering materials from abroad. If you're used to working with metric numbers, buying thread with English markings may result in stitch thickness surprises.
Table of approximate system correspondence
Metric No. 40 is approximately equal to English No. 23 and American Ticket No. 40. Metric No. 60 - English No. 34 and Ticket No. 60. The exact values depend on the twist density and material.
For synthetic threads such as lavsan or polyester, combined markings are often used, which indicate parameters close to their cotton counterparts to make the choice easier for the user.
Den and Tex system: linear density
In the textile industry, especially in the production of synthetic fibers, the system is widely used Den (Denier). It indicates the weight in grams of a thread 9000 meters long. Unlike the metric system, there is a direct relationship here: the higher the Den number, the thicker the thread.
System Tex is an international standard unit of linear density and shows the weight in grams of 1000 meters of thread. It is universal and can be used for all types of fibers, including glass and metal. Knowing these symbols is useful when working with specialized materials.
You can often find double markings on reels, for example, 1200 Den / 2, which means the addition of two threads with a density of 1200 Denier. This makes it possible to create very strong joints used in the production of shoes, bags and car seat covers.
⚠️ Attention: Threads marked Den and Tex often have a slippery surface. When working with them on household machines, be sure to use a Teflon foot or a foot with a roller to avoid the material slipping.
Understanding the difference between the Den and Nm systems helps avoid confusion when a thick thread has a small number in one system and a large number in another.
Number and assignment table
To quickly navigate through the variety of numbers on the reels, it is convenient to use a summary table. This will help you match your thread number to your fabric type and recommended needle size.
| Metric number (Nm) | Fabric type | Recommended needle | Example Application |
|---|---|---|---|
| 30-40 | Jeans, coats, drape | 100-110 | Decorative stitching, heavy fabrics |
| 50-60 | Costumes, cotton, linen | 80-90 | Main seam, stitching parts |
| 70-80 | Silk, chiffon, cambric | 60-70 | Thin delicate fabrics, hems |
| 100+ | Lace, tulle | 50-60 | Invisible seams, working with transparent fabrics |
Using this chart, you can quickly find the optimal needle and thread combination for any project. Remember that the needle should be slightly thinner or equal to the thickness of the thread so as not to damage the fibers.
Correct selection of the thread number for the fabric and needle reduces wear on the sewing machine by 40% and prevents thread breaks during operation.
Color coding and additional symbols
In addition to digital thickness indications, reels are often color coded. This is usually a colored end of the spool or a colored cap that matches the color of the thread. This allows you to quickly find the desired shade in the box without unwinding the spool.
Manufacturers also use letter designations for the type of material: LL (lavsan-cotton), LH (lavsan-cotton, another type of twist), 100% Cotton (cotton) Polyester (polyester). These markings are critical for choosing the washing mode for the finished product.
On some spools you may find a temperature symbol indicating the maximum ironing setting, or a symbol prohibiting the use of chlorine bleaches. Ignoring these symbols may result in damage to the product after the first wash.
Particular attention should be paid to threads with markings Water Soluble (water soluble). They are used for temporary basting and disappear on contact with water, making them ideal for working with expensive fabrics where pin or crayon marks cannot be left.
☑️ Check threads before work
Common mistakes when choosing threads
One of the most common mistakes is using old thread stocks that have been stored for decades. Over time, synthetic fibers lose elasticity, and natural fibers become brittle. Tear test Before starting work, it is mandatory for any threads that have lain idle for more than 3-5 years.
Another mistake is trying to insert a thread of a larger number than the design of the machine allows. Pushing thick threads (for example, No. 20) into a machine designed for No. 40-60 leads to deformation of the needle bar and breakage of the shuttle mechanism.
Some craftsmen ignore the quality of the twist, choosing the cheapest options. Uneven twisting causes the thread to constantly tangle and form loops on the underside of the seam, which requires constant tension adjustments.
⚠️ Warning: Never use hand sewing threads in sewing machines. They do not have a special silicone or wax coating, which causes the needle to overheat and the thread to melt at high speeds.
It is also important not to mix threads from different manufacturers in one seam, as their stretch coefficient may differ, which will lead to deformation of the product after washing.
To check the quality of the thread, rub it between your fingers. If a spool or lint has formed, the thread is of poor quality and will produce a lot of debris in the shuttle compartment of the machine.
How to store threads to preserve properties
Proper storage of consumables will extend their service life. Threads are afraid of direct sunlight, which destroys the polymer structure and fades the dye. Therefore, it is better to store reel stock in closed boxes or opaque containers.
Moisture is another enemy of quality threads. Excess moisture leads to rotting of natural fibers and the appearance of mold, which then stains the fabric and machine mechanism. The optimal humidity for storage is 40-60%.
It is recommended to sort threads by color or number using special organizers. This not only saves time on searching, but also protects the reels from falling and unwinding.
If you live in a dry climate, synthetic threads may become electrified. In this case, storing them with a small humidifier or in a sealed, humidity-controlled bag helps.
Can I use #10 thread in a regular household machine?
Using #10 thread (very thick) in a standard household machine is highly discouraged unless specifically designed for this purpose or by the presser foot. These threads are intended for industrial machines or hand sewing. In a household device, they can get stuck in the needle holder, break the needle or damage the hook.
What is the difference between 45/2 and 50/2 thread?
The difference lies in the thickness of the original fiber. Thread 45/2 will be slightly thicker and stronger than 50/2, since there are fewer meters of length per gram (45 versus 50). For dense fabrics, 45/2 is better, for lighter ones - 50/2.
Why do threads break when sewing?
There may be several reasons: the thread has dried out and become brittle, the thread is not threaded correctly, the needle is dull, the tension is too strong, or the thread number does not match the type of fabric and needle. Also, the thread can break due to burrs on the needle or in the shuttle.
What does the "LL" marking on the reel mean?
The "LL" marking means the thread is made from Mylar fiber (100% polyester). These are durable, abrasion- and fade-resistant threads that are suitable for most modern fabrics, but may slip on some materials.