Wrenches in the form of female sockets have existed for centuries. Early examples include the keys used to wind clocks since the Middle Ages. The heads and sockets were typically square; hex heads eventually became more common starting in the 20th century. The ratcheting socket wrench, with interchangeable sockets, was invented by an American, J.J. Richardson, of Woodstock, Vermont, USA. The tool was patented through the Scientific American Patent Agency on June 18, 1863. The first illustration of the tool appears on pg. 248 of the April 16, 1864 issue of Scientific American.
Square heads and sockets were the easiest to make in the era when hand filing was the typical method of manufacture. With the proliferation of modern manufacturing methods, such as milling, shaping, broaching, and advanced die forging, it became just as easy to make hex heads and sockets as square ones. The hex form allows easier wrenching in confined surroundings (where nearby obstacles obstruct the swing of the wrench), because fewer degrees of arc are needed on each swing before it is possible to reposition the wrench onto the next set of flats. Of course, ratchet wrenches further reduce this problem, as the wrench need only swing as many degrees as it takes for the ratchet pawl to catch the next tooth.
Read more about this topic: Socket Wrench
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