How does a sewing machine work?

How does a sewing machine work? — RD, APO

A sewing machine uses a spinning shaft to push a needle up and down through fabric. The rod that controls the needle’s height is attached to the spinning shaft away from the shaft’s axis of rotation so that as the shaft spins, the rod and needle move up and down. This motion resembles that of a child on a tricycle: as the front wheel turns, the child’s legs move up and down.

Thread from a spool held above the fabric passes through an eye in the needle’s tip, so that as the needle pierces the fabric, it carries the thread with it. A device beneath the fabric catches hold of this thread and pulls it rapidly around a smaller spool of thread (the bobbin). The thread from above the fabric thus fully encircles the thread from this bobbin and the two threads become permanently locked together. When the needle withdraws from the fabric, some of the thread that it carries remains behind, locked around the thread from the bobbin below. With each stroke of the needle, a new joint is created between the thread from above the fabric and the thread from below the fabric. If there are several pieces of fabric lying on top of one another, these pieces become locked together by the intertwined threads.

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