When it comes to the origin of the Allen wrench, we must first start with the Allen screw. In some non English speaking countries in Europe, "Allen key" is called "UNBRAKO key". This "UNBRAKO" is actually the earliest hexagon socket screw brand, founded by the American SPS company (standard pressed steel company) around 1911. SPS company imported a kind of socket head screw from Britain earlier, but the price is very expensive. In order to save costs, SPS company decided to produce it by itself. H T. Hallowell said in his memoirs: "we began to try to make screws with square holes like those in Britain, but soon found that such screws would not be accepted in the United States. So we decided to add hexagonal holes to the screws." Hallowell's explanation of this period of history is ambiguous, but according to later generations, SPS was modified to avoid patent disputes over internal four corner screws. In short, SPS began to produce this new hexagon socket screw and registered a trademark called "UNBRAKO", which is taken from the homophony of "unbreakable", meaning "unbreakable". After that, hexagon socket screws gradually replaced hexagon socket screws and became a new industry standard, which was widely used in automobile, aircraft, machinery, furniture and other manufacturing industries. Origin of "Allen key" As soon as the hexagon socket head screw appears, it needs a matching wrench. In the years when "UNBRAKO" socket head screws were popular in the United States, various wrenches were made, but they did not have a uniform name.
