Allen wrench is also called Allen wrench. Common English names are "Allen key (or Allen wrench)" and "Hex key" (or Hexwrench). The "wrench" in the name means the action of "twisting", which embodies the most important difference between the Allen key and other common tools (such as: flat-blade screwdriver and Phillips screwdriver), which applies force to the screw through torque, Greatly reduces the user's strength. It can be said that among the installation tools involved in the modern furniture industry, the Allen wrench is not the most commonly used, but it is the best.

history
When it comes to the origin of the Allen wrench, we must start with the Allen screws. In some non-English-speaking countries in Europe, people call "Allen key" "Unbrako key". This "Unbrako" is actually the earliest brand of hexagon socket screws, founded by SPS (Standard Pressed Steel Company) in the United States around 1911. SPS company imported a kind of socket head screw from the United Kingdom earlier, but the price is very expensive. In order to save costs, SPS company decided to produce it by itself. H. T. Hallowell, founder of SPS, said in his memoir: "We started trying to make some screws with square holes like in the UK, but soon found out that this kind of screws would not be accepted in the US. So we decided to add six screws to the screws. Angular hole." Hallowell's explanation of this history is vague, but it is speculated that SPS was modified to avoid patent disputes with socket head screws. In short, the SPS company began to produce this new hexagon socket head screw, and registered a trademark called "Unbrako", taken from the homonym of "unbreakable", which means "unbreakable". Later, the socket head cap screws gradually replaced the socket head cap screws and became the new industry standard, and are widely used in the manufacturing industries such as automobiles, aircraft, machinery and furniture.

The origin of "Allen key"
As soon as the socket head cap screw appears, a matching wrench is required. In the years when the "Unbrako" socket head cap screw was popular in the United States, a variety of wrenches were made, but they did not have a uniform name.
advantage
The Allen wrench has been passed down to this day and has become an indispensable tool in industrial manufacturing. The key lies in its own advantages:
    1. It is simple and lightweight.
    2. There are six contact surfaces between the hexagon socket head cap screw and the wrench, which are fully stressed and not easily damaged.
    3. It can be used to screw the screws in deep holes.
    4. The diameter and length of the wrench determine its torque.
    5, can be used to screw very small screws.
    6. Easy to manufacture and low cost.
    7. Both ends of the wrench can be used.