What Is An Allen Wrench
Hex Key or Allen Wrench?
A hex key is also known as Allen key and Allen wrench. A hex key is a simple driver for screws that have heads with internal hexagonal recesses (socket screws).
While often used in generic terms for "hex key", the "Allen" name is a registered trademark (circa 1910) of the Allen Manufacturing Company (now Apex Tool Group) of Hartford, Connecticut; as such, "Allen key" and "Allen wrench" are not generic trademarks.
How Hex Keys Are Made:
Hex keys are made from a single piece of hard steel hexagonal rod having blunt ends that fit snugly into similarly-shaped screw sockets. The rods are bent to 90º, forming two arms of unequal length resembling an "L". The tool is usually held and twisted by its long arm, creating a relatively large torque at the tip of the short arm; it can also be held by its short arm to access screws in difficult-to-reach locations and to turn screws faster at the expense of torque.
Hex keys are designated with a socket size and are manufactured with tight tolerances. Hex keys are commonly sold in kits that include a variety of sizes. Key length typically increases with size, but not necessarily proportionally so.
Variants on this design have the short end inserted in a transverse handle, which may contain multiple keys of varying sizes that can be folded into the handle when not in use.