Hex key

A hex key (also hex wrench, Allen key, Allen wrench) is a simple driver for bolts or screws that have heads with internal hexagonal recesses (sockets). Hex keys are generally formed from a single rod of hard hexagonal steel, having blunt ends that fit snugly into similarly shaped screw sockets. The rod is bent to 90°, forming two arms of unequal length resembling an "L" shape. 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. As such, they are usually 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 can contain multiple keys of varying sizes that can be folded into the handle when not in use. While often used generically, the "Allen" name is a registered trademark (circa 1910) of the Allen Manufacturing Company (now Apex Tool Group) of Hartford, Connecticut.

A hex key (also hex wrench, Allen key, Allen wrench) is a simple driver for bolts or screws that have heads with internal hexagonal recesses (sockets). Hex keys are generally formed from a single rod of hard hexagonal steel, having blunt ends that fit snugly into similarly shaped screw sockets. The rod is bent to 90°, forming two arms of unequal length resembling an "L" shape. 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. As such, they are usually 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 can contain multiple keys of varying sizes that can be folded into the handle when not in use. While often used generically, the "Allen" name is a registered trademark (circa 1910) of the Allen Manufacturing Company (now Apex Tool Group) of Hartford, Connecticut. ===Variants=== Tamper-resistant hex screws have a protruding pin in the center of the hex recess that prevents insertion of standard hex keys; as such, they can only be fastened and removed with a special key that has a recess for the pin. A similar "center pin reject" security feature is also used on torx screws. Some hex keys have a rounded end, allowing them to be used at an angle off-axis to the screw. This type of hex key was invented in 1964 by the Bondhus Corporation and is manufactured by several companies. While providing access to otherwise inaccessible screws, thinning of the tool shaft to create the rounded shape renders it weaker than the straight-shaft version, limiting the torque that can be applied; in addition, the rounded end only makes point contact with the screw as opposed to the line contact made by straight-shaft keys. ==Manufacturing methods== Hex socket screw heads are usually made by stamping the head with a die, plastically deforming the metal. Other ways to generate the hex socket include linear broaching and rotary broaching. Broaching the heads with a linear broach is essentially the metalworking analog of mortising wood with a mortising machine; a hole is drilled and then the corners are broached out. This operation often leaves little telltale curled chips still attached at the bottom of the socket. These are negligible for most applications. Hex keys are made by imparting the hexagon cross-section to steel wire (for example, with a drawing die), then bending and shearing. ==External links== Hex Keys (Allen Keys) and Bits Sockets Dimensions

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