Serger thread is finer than regular sewing machine thread, in order to avoid bulky seams. It must be smooth and consistent in diameter since it passes through so many guides in a serger. Serger thread should not leave a lot of lint, so that it does not clog the serger. Serger thread is sold on a large spool, called a cone, and generally has a length of 3000 yards. Serger thread can be made of cotton, polyester, nylon, or wooly nylon. When choosing thread, select colors that blend with your fabric.
Sergers use multiple strands of thread to form a zigzag pattern across the edge of your fabric to keep it from fraying. This makes it ideal when working with lighter weight fabrics such as knits and formal materials. Sergers also form a cleaner and more professional edge quickly. You will notice that a serged edge looks very similar to the edges you will find on storebought clothing.
Serger thread is needed when using a serger because it is made for the interlocking motions of the serger. It will glide quickly and easily through the machine as well as prevent thick knots from forming along the edges. Serger thread is also specially wound so that it will not tangle on itself, also preventing knots from forming.