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If you could take apart a sewing machine and look at its internal components, you would see a series of connecting wheels, belts, levers and shafts and probably wonder how such an appliance could possibly be used to sew material together. But they do, and they do it well.

Whether it's mechanical, electronic, or even computerized, all sewing machines form a stitch by looping the thread in the needle around a separate thread that comes from the bobbin. The cloth or material is moved along with little tugs from something called a feed dog (no apparent relation to the four-legged kind) which has ridges that go up and down at the same time as the needle. The foot control (like the accelerator on a car) makes it all go faster or slower, and on some units, also serves as an off or on switch.

Mechanical models
On this type of machine, an AC motor drives the aforementioned series of wheels, belts, levers and shafts. These, in turn, move the needle up and down. The width, length and tension of the stitch are set manually with dials.

Electronic models
This type of machine is very similar to the mechanical one except that they incorporate a circuit board that allows for many more features, such as steady power at all speeds and a greater range of fancier stitches.

Computerized models
This type is unlike the others in that it is driven by a DC step motorand it employs much more advanced electronic circuitry that can automatically execute particular stitch patterns. However, just like the personal computer on your desk, the electronic circuitry in this model is subject to power surges, and also like the PC, stored data can be erased. If you have this type, be sure to use a surge protector.