An Allen wrench, also known as an Allen key or hex key, is a hexagonal metal piece that is used to provide torque for bolts and screws that have an internal wrenching hexagonal drive. This is usually found in the shape of an L and while other variations are available, it is the L shaped hexagonal tool that is associated with the name. The Allen wrench is different from other wrenches. Unlike the adjustable wrench or the socket wrench that provide torque for the outer portion of the bolt, the Allen wrench provides the torque from the center of the bolt or screw head. This makes it useful in cases where the force of the torque should be minimized or controlled such as in fastening wooden pieces or sensitive motor parts. Other forms of Allen wrenches have security pins and balls fasteners. The security pins prevent Allen wrenches other than those that have the matching socket from working while ball fasteners allow the Allen wrenches to be used at different angles.
Allen wrenches are available in various forms and sizes. A typical Allen wrench set is the Generic 30 piece Allen wrench set. It contains Allen wrenches for British or SAE sizes and metric sizes. These range from 0.35 inches to 3/8 inches for SAE sizes and 0.7 mm to 10 mm for metric sizes. A typical set like this costs approximately $12.
Higher end Allen wrenches are also available such as the 12 piece Ball Driver L Wrench Set from Bondhus Tools. The innovators of the original ball end Allen wrenches, Bondhus uses their design in this set. With sizes ranging from 5/64 inches to 1/4 inches, these have a wide range of uses. The ball end design that Bondhus is famous for allow these wrenches to be used at different angles, which is quite useful in tight spaces or awkwardly positioned screws and bolts. This set costs $13 dollars, making it competitive with even generic Allen wrench sets.
There are times when the L shaped design of Allen wrenches does not provide enough leverage for the job. For jobs such as those, the larger handle of fold up Allen wrench tools may help. These tools allow Allen wrenches of different sizes to be folded into a single casing, much like the Swiss Army Knife design. One such tool is the Fold Up Torx 7 Key Set from the Elkind Tool Company. Featuring the 7 most commonly used wrench sizes made from hardened alloy, this fold up set provides a convenient tool for the home. This is especially useful when differing sizes are need for a single job. This particular fold up set costs $15.50.