If you include all the hand stitches, sewing machine utility stitches, sewing machine decorative stitches, serger stitches, and industrial manufacturing stitches, you have a bunch of stitches. On a moderately priced home sewing machine you will find twenty to two hundred different stitches plus variations in stitch length and stitch width as well as stretch factors. A top quality home sewing machine will have eight hundred to a thousand different stitches.
There are several distinctly different types of sewing machines and each type uses slightly different systems to select and form stitches. 96 Mechanical sewing machines are the least expensive sewing machines and use the most primitive technologies. An AC electric motor turns a belt which turns the upper sewing machine shaft. The upper shaft transfers the mechanical energy along the shaft past the cam system to the needle system.
A lever on a parabola connection transfers the mechanical movement down to the lower sewing machine shaft which may be split into a dual lower shaft one to drive the hook and a second to drive the feed dogs. Stitches are formed in a mechanical machine by aligning cam trackers (levers that rub against a cam gear with bumps and shallows) with the cam gear so that when the cam gear moved the tracker lever will bounce back and forth.
This movement is then transferred by lever to the needle assembly moving the needle bar back and forth and up and down to form the desired stitches. The alignment of the cam trackers is achieved by use of levers, buttons, or dials protruding on the top or face of the sewing machine. The user moves the stitch selector to the proper position, and the trackers line up to form that stitch. Additional dials or levers are used to adjust the stitch length and stitch width.