Sewing Machines

A sewing machine is a textile machine used to stitch fabric or other material together with thread. Sewing machines were invented during the first Industrial Revolution to decrease the amount of manual sewing work performed in clothing companies. Since the invention of the first working sewing machine, generally considered to have been the work of Englishman Thomas Saint in 1790, the sewing machine has vastly improved the efficiency and productivity of fabric and clothing industries.

The main stitch of most older sewing machines, chain stitch, has one major drawback – it is very weak and the stitch can easily be pulled apart. When the machines started being used, people realized a stitch more suited to machine production was needed, and it was found in the lock stitch. A lock stitch is created by two separate threads interlocking through the two layers of fabric, resulting in a sturdier stitch that looks the same from both sides of the fabric.

Chain stitch is less widely used than lockstitch, but it is preferred over lockstitch for applications like sealing bags of grain, garment seams likely to be altered, and as a "safety stitch" on serging machines. A chain stitch may be formed with either one or two distinct threads, one passed through a needle and the other, if used, manipulated by a looper, a device which moves back and forth but does not pass through the fabric. The needle thread is formed on both sides of the material being sewn, and on the bottom of the material either crosses through loops of itself (single thread) or loops of the second thread to prevent it from pulling back to the top of the material. Most household chainstitch machines are either very old, or toys intended for children. Industrial chainstitch machines are still heavily used in their application areas.

Overlock can only be formed at the edge itself, where one or more threads pass over the edge. Varieties of overlock stitch can be formed with one to four threads, one or two needles, and one or two loopers. Overlock sewing machines are usually equipped with knives that trim or create the edge immediately in front of the stitch formation. Household and industrial overlock machines are commonly used for garment seams in knit or stretchy fabrics, for garment seams where a clean finish is not required, and for protecting edges against ravelling. Machines using two to four threads are most common, and frequently one machine can be configured for several varieties of overlock stitch. Overlock machines with five or more threads usually make both a chainstitch with one needle and one looper, and an overlock stitch with the remaining needles and loopers. This combination is known as a "safety stitch".