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in practical mechanics, a number of superimposed, tightly wound, helical coil springs wrapped around a centre wire, or mandrel. Because of its construction, the shaft can be bent, without fracture, to a much smaller radius than a solid shaft of the same outside diameter. The shaft is connected to the power source and the driven member by special fittings that are soldered or swaged on the ends of the shaft. For transmitting power around corners and for considerable distances, flexible shafts are usually cheaper and more convenient than belts, chains, or gears. Automobile speedometers are driven by flexible shafts, and such shafts are useful for portable tools such as sanders and grinders