Speaking of the origin of Allen key, we must start with Allen key. In some non-English-speaking countries in Europe, people call "Allen key" "Unbrako key", which is actually the earliest brand of hexagon socket head screws. It was founded by American SPS Company around 19 1 1. SPS Company imported an inner quadrangular screw from England earlier, but the price was very expensive. In order to save money, SPS decided to produce it by itself. H·t· Hallowell, the founder of SPS, said in his memoirs: "We started to try to make some square-hole screws similar to 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 history is vague, but later generations speculated that SPS was modified to avoid the patent dispute of internal quadrangular screws. In a word, SPS Company began to produce this new type of hexagon socket head screws and registered the trademark "Unbrako", which is taken from the homonym of "unbreakable" and means "unbreakable". Later, hexagon socket head screws gradually replaced internal four-corner screws and became a new industry standard, which was widely used in automobile, airplane, machinery, furniture and other manufacturing industries.
The origin of "Allen wrench"
As soon as the hexagon socket head screw appears, it needs a matching wrench. In those years when "Unbrako" socket head cap screws were popular in the United States, various wrenches were made, but there was no unified name.