Info : Another product from the Yamaha BR manufacturer, the Lijia, these sewing machines can make a great variety of plain or patterned stitches. Ignoring strictly decorative aspects, over three dozen distinct stitch formations are formally recognized by the ISO 4915:1991 standard, involving one to seven separate threads to form the stitch. Plain stitches fall into four general categories: lockstitch, chainstitch, overlock, and coverstitch.
Lockstitch is the familiar stitch performed by most household sewing machines and most industrial "single needle" sewing machines from two threads, one passed through a needle and one coming from a bobbin or shuttle. Each thread stays on the same side of the material being sewn, interlacing with the other thread at each needle hole by means of a bobbin driver. As a result, a lockstitch can be formed anywhere on the material being sewn; it does not need to be near an edge. Stitch making : The drive shaft has a vertical crank attached to it, going down under the base plate. Again, by a series of levers, this connects to a hook ring. The hook ring picks up the upper thread and guides it round the bobbin holding the lower thread. Using the up and down movement of the needle and the rotation of the hook ring the two threads are looped together to form the stitch.