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.