Who invented the Allen Wrench?

The Allen wrench, also known as a hex key or hex wrench, was invented by William G. Allen in 1910. Allen, a machinist from Hartford, Connecticut, patented his design for a "wrench for setting up machine tools" on November 4, 1910. His invention featured a hexagonal-shaped head and a tapered shaft, which allowed it to be used in tight spaces. Allen originally manufactured his wrenches in his home workshop, but he later founded the Allen Manufacturing Company to mass-produce them. Today, Allen wrenches are still commonly used in a variety of industries for tasks such as tightening bolts and screws.