Everything You Always Wanted to Know About Hex (But Were Afraid to Ask)

Everyone has one, but hardly anyone knows where they came from. The Allen key is one of those flash-in-the-pan inventions that just make life easier.

Hex-keysThe Allen brand of hand tools is owned by Apex Tool Group, Hartford, Connecticut, widely known for its eponymous hex key wrenches. Originally named the Allen Manufacturing Company, the business produces hexagonal set screws and wrenches to fasten them. A set screw secures an object within or against another object. It is usually headless. The terms “Allen wrench” and “Allen key” are derived from the Allen brand name and refer to the generic category of “hex keys”.

The idea of a hex socket screw drive (the system used to turn a screw) was probably conceived as early as the 1870s, but such screws were probably not manufactured until around 1910. Before that, the driving end of screws tended to protrude from machinery and create a safety hazard.

Allen-Safety-Screw-SetIn 1910, William G. Allen patented a method of cold-forming screw heads around a hexagonal die (U.S. Patent 960244 A). Soon afterwards the company began advertising its new product: the “Allen safety set screw”. Although it is unlikely that Allen was the first person to think up a hex socket drive, his patent for a manufacturing method and its product appears to be a first. In his Application for a Patent filed on 7 June 1910, Allen wrote:

“Be it known that I, WILLIAM G. ALLEN, a citizen of the United States, residing at West Hartford, in the county of Hartford and State of Connecticut, have invented a new and useful Improvement in Manufacture of Screws, of which the following is a specification: This invention relates more particularly to the manufacture of flush head set screws, that is, set screws so shaped and threaded that when put to use their heads are sunk even with the outer surfaces of the parts into which they are driven, although the invention is applicable to the manufacture of machine screws and set screws having projecting or fillister heads.”

In 2000 the Scottish-Canadian architect and writer Witold Rybczynski published One Good Turn: A Natural History of the Screwdriver and the Screw. Pursuing a commission by The New York Times Magazine, Rybczynski discovered that the screwdriver is a relatively new addition to the toolbox, an invention of the Late Middle Ages in Europe and the only major mechanical device not independently invented by the Chinese.

Rybczynski comments, “There are tools, such as the handsaw, that develop slowly and are refined over centuries. Others, such as the carpenter’s brace, are adaptations of a new scientific principle. Then there are those inventions that appear seemingly out of the blue.” Imagine DIY without hex screws and Allen keys.

Unsurprisingly, that master of invention Leonardo da Vinci was there at the start, designing a number of screw-cutting machines with interchangeable gears. But it took generations for the screw (and with it the screwdriver) to come into general use, and it was not until 1910 that a quantum leap in manufacturing screws took place. That is, until someone put a hex on them!

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