Usually an overlock sewing machine will cut the edges of the cloth as they are fed through (such machines are called ‘sergers’ – An overlock stitch sews over the edge of one or two pieces of cloth for edging, hemming or seaming), though some are made without cutters. The inclusion of automated cutters allows overlock machines to make finished seams easily and quickly.

Overlock sewing machines differ from a lockstitch sewing machines in that it uses loopers fed by multiple thread cones rather than a bobbin. Loopers serve to make thread loops that pass from the needle thread to the edges of the fabric so that the edges of the fabric are contained within the seam. Overlock sewing machines usually run at high speeds, from 1000 to 9000 rpm, and most are used in industry for edging, hemming and seaming a variety of fabrics and products. Overlock stitches are extremely versatile, as they can be used for embellishment, fortification, or construction.

Overlocking is also referred to as “overedging”, “merrowing” or “serging”. Though “serging” technically refers to overlocking with cutters, in practice the four terms are used interchangeably.

Following the enhancement of the manufacturing overlock sewing machine, many companies started competing for the home market. In 1964, several engineers and middle managers at a Japanese manufacturing company believed that they could redesign the manufacturing serger they were currently manufacturing to be smaller and lighter.

Their company rejected the concept, but the team was so committed to their thought that they quit their job and formed their own company. They wanted to build a smaller “baby” serger for home sewers that was capable of producing an overlock stitch. This was the birth of a machine called Baby Lock.

Today Baby Lock is known worldwide for advancements in sergers – above all the patented Jet-Air Threading technology that threads an entire serger reluctantly.

The enhancement and formation of the stitch are similar to the manufacturing models with some noteworthy exceptions.