Industry Technologies
by Dr.Trevor Little, Professor Emeritus NC State University Introduction This is the first article in a series on "Sewing with Threads". In this article, we cover the basics of thread construction and what is involved in selecting a thread. Also, in this first article, we explore the consumption of thread from a practical perspective which will depend on the type of stitch used. Having said that, we have to familiarize the reader with stitch types and the variety of elements involved.
A threadIn everyday language, a thread is a yarn that has more twist (turns per inch) than yarn that is used for knitting or weaving. Yarns can be made with an 's' or 'z' twist. It is common to combine yarns, either 's' or 'z', and twist them together. Twisting should be done in the same direction 's' or 'z' to prevent the unraveling of the thread.
Yarn structures have changed over the years as have yarn or thread numbering systems. So let’s get up to date. In older technology, the threads were spun. Cotton threads were very popular to control needle heat. More recent technology has placed a core thread, usually of polyester, and wrapped it with cotton fibers, to provide the advantage of fewer thread breaks during sewing. Now the thread manufacturers can spin synthetic yarn and add twist. Also, spun synthetic threads have become very popular. A manufacturer may also encounter filament threads for use, primarily, in over-the-edge stitches.
Basically, 100% cotton threads can be weak and can frequently break during sewing. However, 100% cotton thread is a must for garment dyeing. Sewing machines that are used must be set up correctly to minimize thread breakage while providing a good appearance of the sewn stitch.
So, the preferred direction of twist on traditional threads is ‘z’ as the final twist. This helps in throwing the loop that is caught by the hook on traditional lockstitch machines.
When we have two-needle lockstitch machines, it is necessary to use corespun threads to avoid one side of the seam appearing different from the other. The reason is that both bobbins rotate in the same direction and one bobbin will untwist while the other twists or maintains the twist.
When we talk about threads and procuring threads it is essential that the factory knows the end use of the thread and how to distribute it to each machine. This is one reason for the rise in core threads popularity as well as cost.
The size of the thread
The size of the thread is probably one of the least understood subjects. For direct thread numbering systems thicker threads have increasing numbers (Tex, Denier, etc.) while increasing numbers on the indirect yarn numbering systems produce finer threads (Ne, Metric, etc.) Sometimes these are referred to as Length and Weight numbering systems. Essentially, the Length numbering is length/weight while the Weight numbering is weight/length.
Example: Nm of 80 is equivalent to Tex 40.
That is Nm = 80 kilometers/1 kg = 1000 meters/40 grams
Threads can come in all forms from spun to continuous filament. Continuous filament threads are commonly used on loopers and are usually numbered according to the Denier system. Denier is the weight in grams of 9000 meters of thread. The number on the package is usually Denier plus a 10% contraction factor. That means 150 denier may appear on the package as 165 denier to accommodate the contraction factor for twisting the 150 denier yarn to become thread.
Today, there is a tendency to mark all threads with the Tex number which is the weight in grams of 1000 meters of thread. However, the construction of the thread is important to give a satisfactory seam.
With spun threads, it is common to twist two or more plies together and then twist them. Plied threads can be numbered on the Cotton system (Ne) which is the number of 840 yards in one pound (453.6 grams). Although Tex is more commonly used today. While I know it can be confusing initially, just remember that in the length/weight system, the smaller the number the coarser the thread while for weight/length, the smaller the weight number, the finer the thread. Sometimes, these are called Indirect and Direct systems of thread numbering, respectively.
Thread labelsThe label on threads today may show the Tex number and the Ticket Number. The Ticket Number is the former way of describing a thread size. Usually, a Number is on the Ne (cotton) system but Ticket Numbers on filament threads may be different.
Mercerized or UnmercerizedThe mercerizing process involves the use of caustic soda and cotton thread to impart a shine to the thread and to make it stronger. Unmercerized cotton threads may be Labeled Soft and more like natural cotton.
Thread PliesThe most common are 2-ply and 3-ply threads. Plying thread is practiced giving a smoother and stronger thread and removing irregularity from the spinning process. Any thread that is spun usually has several plies.
The NeedleWhy is the needle important? So, forming and setting the stitch depends on how the sewing machine is configured. It is necessary to understand the stitch type being produced.
For a basic lockstitch (301 stitch) the thread may pass through the eye of the needle some 70 – 100 times before forming a stitch. If the eye of the needle is not polished, there can be a lot of thread abrasion and a weaker seam. Thread manufacturers give the thread strength not the seam strength.
In theory, the seam should break before the fabric breaks. That way, the seam can be repaired. However, most seams are stronger than the fabric making repairs a challenge.
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Dr. Trevor Little
Thread ConsumptionMost manufacturers must know the consumption of thread in a garment. It is necessary for costing as well as purchasing the correct amount of thread. Basically, the amount of thread can be found in several ways. Unravel the length of thread, or calculate the amount of thread.
To calculate the consumption of thread, get a copy of the Union Special Thread Consumption tables (shown here) and find the stitch type in ISO 4915 standard. Thread manufacturers also prepare charts to assist thread purchasing areas. You may download a copy at: https://www.dropbox.com/s/ctr7zgr9fmn2zop/Thread%20Consumption%20Book.pdf?dl=0.
Some thread manufacturers also have the amount of thread needed to make a garment. However, the stitch type often determines the number of thread packages, and getting Thread Consumption accurate is always a challenge.
Thread ColorThread color can often interfere with Thread Consumption calculations. It is common to have color charts that list 200 or 1154 colors of thread. A new system for dyeing colors is available called Twine which is available in the US through Henderson Sewing Machine Company.
Thread color must match the fabric color and color creates challenges in the Thread business as colors can change quickly and the color palette may drop or add colors making thread consumption calculations a challenge for garment producers.
Apparel ThreadApparel thread usually begins around Tex 20 and goes to Tex 350 (or thereabouts) but the most common are the Tex 24-27 and Tex 40-50. When calculating consumption, the number of stitches must be considered. A rule of thumb is 10-12 stitches per inch for apparel seams. Sewing machines start and stop so the stitches per inch will vary according to the speed of the machine.
For topstitching, it is common to have a lot more stitches (18-22) with a lockstitch (301 stitch) to make the item more appealing to the customer.
Most garments are made so that seams do not show. However, with stitch types like 301, 406, and lapped seams, the thread will be visible on the outside of the garment and colors must match.
Sewn products thread.
Most thread used for non-apparel sewn products shows on the outside. Products like towels, signage, boats, tents, upholstery, quilting, etc. will use threads made for that application. Typically, they are stronger to withstand the abrasion forces that can be a part of the use of these types of products.
In the next article, we will consider specific products and the threads made for these non-apparel sewn products applications.