As the speed of sewing machine used in modern garment industry is over 5000 rpm, the quality requirement of thread is even higher.

The main qualities that sewing thread must possess are: 

(1) smooth surface, uniform color and luster, seamless; 

(2) certain fastness and wear resistance; 

(3) small shrinkage rate. 

As the speed of sewing machine used in modern garment industry is over 5000 rpm, the quality requirement of thread is even higher. Synthetic fiber thread has many advantages, such as high strength, wear resistance, corrosion resistance and small shrinkage. It has replaced cotton thread to a great extent. When sewing elastic fabrics, low elasticity polyester threads (see deformed fibers) are often used to keep the stitches and fabrics flexible. In order to avoid the difficulty of color matching between sewing thread and fabric, transparent synthetic filament yarn can be selected. Because of its transparent quality, it is suitable for sewing various color fabrics.

The single yarn count of sewing yarn  ranges from 9 to 80. 

Most of the combined strands are 3 strands, and there are also 2 strands, 4 strands and more than 6 strands, up to 12 strands. More than six strands of thread are generally used in leather, canvas and shoemaking industries. In the era of manual sewing, twisted cotton threads and silk threads were the main types of wrapping of sewing threads. With the use of sewing machine, wooden yarn balls appeared again, that is, waxed cotton  thread was wound around the wood core, and then paper core (or plastic core) thread, paper plate thread, thread ball, pagoda thread and so on. The capacity of various packages varies according to civil and industrial use. Civil sewing thread, such as wood yarn, paper core thread, cardboard thread and thread ball, is 50-1000 meters in length; industrial sewing thread is wrapped in a length of 1000-11000 meters, which is usually wrapped on conical or side tube, called pagoda thread or plywood tube thread.

The models of sewing thread are 202, 203, 402, 403, 602, 603 and so on.

The thread is usually twisted and twisted side by side by several strands of yarn thread. The number of yarns thread in front of the sewing yarn type refers to the number of yarns thread. The number of yarns can be simply understood as the yarn's thickness. The higher the number of yarns thread, the thinner the thread. The number of 2 and 3 behind the model refers to the number of yarns . thread twisted and twisted by several strands of yarns.

Thread thickness comparison: 203 > 202 > 403 > 402 > 603 > 602 603 and 402 threads are basically universal and are the most common sewing threads, which can be used for general fabrics, such as cotton, linen, polyester, viscose and other common fabrics; 403 threads are used for thicker fabrics, such as woolen fabrics;

202 and 203 thread can also be called jeans thread. The thread is thicker and stronger. It is mostly used for jeans, bags and other sewing.

The main types of synthetic thermoplastic fibers used for sewing are filament twisting and core-spun yarn thread, such as nylon and polyester, which have high toughness and wear resistance. They can be used together with cotton fibers to make better sewing threads. The larger ductility and lower moisture absorption of nylon and polyester make the  threads stronger and have lower melting point. Make the sewing thread sensitive to the heat change of the machine needle.

Filament twisting

The single yarn is spun from various regenerated staple fibers and twisted into a sewing thread from 2-6 strands of single  thread. The most commonly used yarn thread is polyester, which has high strength, elasticity and wear resistance. However, due to the thermal effect of the machine needle, the price is much lower than that of the core-spun yarn.