How do mechanical sewing machines form different stitches?
By definition, a mechanical sewing machine forms stitches using gears and levers.
The vast majority of these machines are called lockstitch because they use two threads.
One thread is drawn from above by a needle down through the material.
Below the needle plate, a hook picks up the upper thread and wraps it around the lower thread. The needle rises pulling the thread taught until a knot forms inside the fabric.