Spun polyester sewing thread is an essential material for creating durable and high-quality seams across various fabric types. If you’ve ever wondered about thread grades, their applications, and how to make the best choice for different projects, this guide will provide clarity. When working with sewing thread manufacturers  or sewing thread suppliers, understanding grades such as 20S, 30S, 40S, and 50S will help you select the right product for your needs. Table of contents： Understanding 20S, 30S, 40S, and 50S Thread Grades Choosing the Right Thread Thickness for Knits, Wovens, and Leather How Thread Structure Affects Tension, Stitching, and Breakage Common Thread Defects and How to Avoid Them in Bulk Orders   Understanding 20S, 30S, 40S, and 50S Thread Grades  The grades 20S, 30S, 40S, and 50S refer to the thickness and strength of spun polyester threads. The "S" stands for single-ply, while the numbers indicate the weight or size of the thread. A lower ...