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History
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The Name in Your Toolbox: Unfastening the True History of the Allen Wrench
Ever wondered why it's called an Allen wrench? The name comes from the Allen Manufacturing Company's 1910 patent for safety screws with a hexagonal socket. But this humble tool's origin is a global story of competing patents, industrial safety, and a name that simply stuck.
If you’ve ever wrestled with assembling a piece of flat-pack furniture, you’re intimately familiar with a small, L-shaped piece of metal. It’s the unsung hero of countless bookcases, bed frames, and desks. We call it an Allen wrench, a name so common it has become the generic term for any hex key. But like Kleenex or Band-Aid, the name that has defined the tool for over a century began as a specific brand, born from a need for safety in the hazardous factories of the Industrial Revolution.
A Safer Screw for a Dangerous Time
Imagine the factory floor in the early 1900s. It was a forest of whirling belts, spinning shafts, and exposed machinery. A significant and often gruesome hazard was the traditional set screw. These were the fasteners used to hold pulleys and gears onto shafts, and their raised, square heads could easily snag a worker’s loose clothing, leading to horrific injuries or death. The clear solution was a “safety screw,” one that could be tightened flush with or even below the surface of the surrounding machinery. The challenge was figuring out how to turn it without a protruding head.
The Hartford Connection
Enter William G. Allen and the Allen Manufacturing Company of Hartford, Connecticut. While the idea of an internal-wrenching screw had been floating around for decades, Allen’s breakthrough was in the manufacturing process. In 1910, he was granted a patent for a method of cold-drawing and heading a screw to create a clean, strong hexagonal socket. This process made the production of these safety screws commercially viable on a mass scale. The Allen Manufacturing Company marketed these new “Allen safety set screws” aggressively, and with them, the L-shaped “Allen key” needed to turn them. The name stuck, at least in North America.
A Tale of Competing Claims
The story of the hex key is not a simple one-man invention. History is rarely so neat. Around the very same time, the Standard Pressed Steel Company (SPS) of Pennsylvania was developing its own version of the socket-head screw. Led by H.T. Hallowell, Sr., SPS began producing its own line, which it trademarked as “Unbrako,” a name still prominent in the industrial fastener world today. While Allen may have secured the patent first, SPS was a formidable competitor that also played a crucial role in popularizing the design.
The story gets even more international. In Germany, the company Bauer & Schaurte patented a similar system in 1936. Their brand name, “Inbus” (a contraction of Innensechskantschraube Bauer und Schaurte), became so dominant that in Germany and many other European countries, an Allen key is simply called an “Inbus key.”
Why 'Allen' Won the Name Game
So why did “Allen” become the go-to term in the United States? It’s a classic case of a brand becoming a genericized trademark. The Allen Manufacturing Company was an early and effective marketer of a revolutionary solution to a widespread safety problem. By the time competitors ramped up, the name “Allen screw” was already embedding itself in the language of mechanics, engineers, and factory workers. It was a simple, memorable name tied to the first commercially successful product of its kind that many people encountered.
The next time you pull that simple tool out of a plastic bag to assemble a new chair, you’re holding a piece of industrial history. It’s a testament to a time when a simple change in a screw’s design could save lives, and a reminder that even the most common objects in our lives have a surprisingly complex and contested story behind them.