A lockstitch sewing machine binds cloth together with two spools of thread and a needle with the eye at its base. Distinct from a chain stitch machine, a lockstitch sewing machine makes strong, straight seams. It was the first kind of commercial sewing machine to secure a patent, enter manufacturing, and place automatic sewing in the hands of millions of households.
Most homes have a lockstitch sewing machine because their basic stitch can be used for a wide variety of applications. The machine works by interlocking two threads from two bobbins that cannot unravel easily, unlike a chain stitch. The length of the stitch, as well as tautness, can be controlled by dial.
The first spool sits on top of the machine. Its thread runs through a tension arm to feed it smoothly. Then it threads into a needle's eye, located at its base. The needle attaches to a foot that can press the fabric against a feed. The second thread, on another bobbin, is hidden in a compartment beneath the foot. This thread gets pulled on a shuttle to loop around the thread from above. The needle stitches up and down either by a manual foot treadle or a motor controlled by pedal.
Several different engineers, working in stages, took decades to perfect an automated lockstitch sewing machine that was easy to build, use, and repair. In 1846, Elias Howe thought of the basic idea of looping one thread through another, while the hand-cranked needle stitches back and forth. Even though he received a patent, he never engineered or marketed it successfully. In the 1850s, Isaac Singer improved upon Howe and built a machine where the needle moved up and down and the crank was controlled by foot, so hands could be free to feed the cloth. He also perfected the second shuttle that sits underneath to control the bobbin.
A modern lockstitch sewing machine has added convenience, strength, and flexibility, but it works by the same principles. Now they are electrified so the foot pedal powers the stitching with a motor. They are also outfitted with attachments or settings that allow you to hem, quilt, form buttonholes, embroider, and stitch other decorative seams, in addition to sewing straight seams. Their versatility supports different sized spools, fabric of various thickness, and many customized projects.