The conventional electric sewing machine parts are a fascinating piece of sewing machine If you were to take the outer casing off, you would see a mass of copper sleeve gears, cams, cranks, wheel bolt and belts, all driven by a single electric motor. The exact configuration of these elements varies a good deal from machine to machine, but they all work on a similar idea.
The thread runs from a spool on the top of the machine, through the tightening arm and through a tension disc assembly. By turning the disc assembly, the sewer can tighten the thread feeding into the needle. The tension must be tighter when sewing thinner fabric and looser when sewing thicker fabric.
The first element along the shaft is a simple belt that turns a lower drive shaft. The end of the lower drive shaft is connected to a set of bevel gears that rotates the shuttle assembly. Since both are connected to the same drive shaft, the shuttle assembly and the needle assembly always move in unison.
