How a sewing machine works

In short: A sewing machine joins two layers of fabric by interlocking the upper and lower thread in every stitch. This so-called lockstitch results from the interplay of needle, bobbin, and hook.

In more detail: The needle carries the upper thread down through the fabric, where a rotating or oscillating hook loops the lower thread from the bobbin case around it.

In detail

• Needle and upper thread: The needle pierces the fabric with the upper thread, forming a small thread loop.
• Hook and lower thread: A hook catches this loop and interlocks it with the lower thread from the bobbin.
• Feed dogs: Small teeth under the needle plate push the fabric forward a bit after each stitch.
• Thread tension: Upper and lower thread tension must be balanced so the stitch sits evenly in the middle of the fabric.
• Stitch patterns: Electronic machines can create zigzag and decorative stitches via a cam disk or a motor.
• Needle size: The thicker the fabric, the thicker the needle and coarser the thread should be.
• Maintenance: Regularly removing thread lint and oiling moving parts significantly extends the machine’s lifespan (buegeleisen-und-daempfer-funktionsweise).