Allen Wrenches
Posted on 25. Jan, 2012 by Chris in Tools, Wrenches
Is it an Allen wrench, hex key, or Allen key?
All three names are used for the same tool. Allen wrenches may also be called Unbrako keys or Inbus wrenches.
The hex bolt head was invented in 1911 by Standard Pressed Steel Company, now SPS Technologies. At first they wanted to make their own screws to replace the expensive square-drive screws they were importing from England. Originally square, SPS switched to a hex design to avoid complications with P. L. Robertson’s own square slot patent. The Canadian inventor had previously refused to allow Ford Motor Company to reproduce his design; SPS’s management felt that an agreement with a smaller company like themselves would be highly unlikely. These new hex bolts and tools were marketed under the “Unbrako” brand.
“Inbus” comes from Germany’s Bauer und Schaurte company. They independently developed their own hex wrench which came to market in 1936. Their tools were marketed under the acronym INBUS for “INnensechskantschraube Bauer Und Schaurte.” “Inbus wrench” is still a common name for the tool in much of Europe.
By World War II Unbrako bolts were a mainstay of industrial production, particularly airplanes. SPS was unable to keep up with demand for their wrenches. Seeing a market opening, Allen Manufacturing Company released their own Unbrako-compatible tools in 1943. The spread of hex bolts outside specialty manufacturing meant that the first hex wrench most people saw was an “Allen” wrench.
How are Allen wrench sizes measured?
Allen wrench sizes are determined “across flats,” the width of the tool between two opposite flat sides of the head. Wrenches are manufactured both in S.A.E. and metric sizes.
Where are Allen bolts used?
Allen bolts don’t have a protruding head; They can be used in areas where a smooth surface is required. These are most commonly seen on motorcycles and bicycles where an exposed bolt could catch on clothing or moving parts.
Allen wrenches are very inexpensive to produce which makes them popular in flat-pack furniture and other products that are assembled at home. A cheap wrench can be included in the packaging giving the user everything they need to put a product together.
What types of Allen wrenches are there?
L wrench: This is a hexagonal bar that has been bent into an “L” shape. Either end of the wrench will fit a hex bolt.
T wrench: This uses the same metal bar as the L wrench, except the metal is either bent into a flat “G” shape at the end or attached to the center of a handle. These Allen wrenches most closely resembles a corkscrew.
Allen wrench set: Often these come packaged in a folding handle similar to a Swiss Army knife. The individual wrenches have a hook-shaped end through which a bolt is passed through to hold them in the handle. This bolt can be removed so that the wrench can be used by itself in tight spaces.
Allen socket: This is a small piece of hexagonal bar mounted in a socket. The short length requires stronger metal than the other wrench sets increasing the price; a single high-quality socket can cost as much as an entire set.