Allen wrench


After the industrial revolution, different types of screws and wrenches have been created that specialize in a specific job. Among these, the use of the famous Allen key stands out .


What is an Allen key?

In mechanics and construction, the Allen key is a type of manual tool intended for handling socket head screws. These screws are used above all in contexts where you want to do without conventional screws. The latter are commonly pieces that protrude from the machinery, which is why the Allen designs were made.

  • Allen key features
  • History
  • Who Invented the Allen Key
  • What is it for
  • Measures
  • Advantages of the Allen key
  • Disadvantages
  • How to make a homemade Allen key
  • How it differs from the Bristol key
  • Importance

Allen key features

To support any construction, sometimes it is necessary to apply screws . Today, it is difficult to find some type of device that does not have these elements under its belt. The safest thing is that the device you use to read this article is an example of this.


But, although a screw is such an important element, it is not a secret that there is not just one type of screws, nor is there a single type of tools to manipulate them. There are protruding screws, which can be seen above the surface of an object . And there are also screws that don’t, that are “a little more subtle.”

By the latter, we mean Allen screws .

These have a very interesting history , which we will talk about in a little more detail later.

With all this, the first thing we must understand is that along with every screw and nut that we talk about, there will always be an instrument to manipulate it. One of them is the famous Allen key , and we will talk about it today.

Let’s see some of its main features:

  • This is a hand instrument made to manipulate six-sided, six-corner hollow screws .
  • It is usually a steel bar of different sizes or measures.
  • It has its origins in 1910, under the Allen Manufacturing Company patent . Hartford, Connecticut. United States .
  • Its operation varies depending on its type. But, usually , it involves the insertion of a male wrench into a hollow screw or nut.


The creation of the Allen keys is parallel to the creation of screws of the same type. One must understand that, at that time, at the beginning of the 20th century, accidents were a daily occurrence . Everyday, yes, but extremely expensive for the company, which lost a lot of dollars in medical expenses and in lost labor. One of the most common accidents were those caused by clothing jamming with a protruding nut or bolt. To solve this, a company , which we will talk about later, was in charge of patenting a type of screw or nut that would dispense with this difficulty. We could say that this was the beginning of the screws and Allen keys.

Who Invented the Allen Key

As such, the patent for this invention was held by a Connecticut company in 1910. The reasons, as is known, come from industrial safety, but little by little it spread to other areas. The name of this company is Allen Manufacturing Company . This company, by the way, still exists; it is in the hands of another larger company called Apex Tool Group . The latter, therefore, are the ones who own the patent for the product.

What is it for

The usefulness of the Allen key is that it allows you to manipulate nuts and bolts. More specifically, hexagonal hollow nuts and bolts. They are tools that can be used for screwing or unscrewing watches, electronic equipment and devices, among many others.


In relation to its measurements , one could say that they encompass the following:

  • 1.5 m / m.
  • 2 m / m.
  • 2.5 m / m.
  • 3 m / m.
  • 4 m / m.
  • 5 m / m.
  • 6 m / m.
  • 8 m / m.
  • 10 m / m.

Advantages of the Allen key

Among the advantages that we could name of this type of keys , we have the following:

  • Its design exudes simplicity . It is light and does not take up much space.
  • The keys fit perfectly on the screw angles . These, in turn, are protected from damage from the outside .
  • The torque has the quality of being redistributed throughout the wrench.
  • They can be applied to screws of various dimensions or sizes . There are keys, in this regard, of very varied dimensions.
  • By making correct use of it, the screw will not suffer injuries or deterioration .
  • Its manufacture is simple , and does not require many costs .


Among the main disadvantages that the Allen key presents, we can say that it is the care it requires at the level of use that is given to it. It is important that the correct wrench is used together with the correct screw. Otherwise, you run the risk of damaging the screw or the key itself.

How to make a homemade Allen key

As their composition is simple, they can be built as long as you have the appropriate materials for this purpose. A recommendation is to take a piece of iron filing or a graphite pencil, and sand one of its ends in such a way that it has the desired hexagonal shape. At this point, a knife or other filing can be used for this purpose. It is important to understand that, before doing this homemade work, the dimensions of the screw to be adjusted or loosened must be well known .

How it differs from the Bristol key

One of the disadvantages of Allen keys is their tendency to “go over the top” . As previously stated, there is a risk that the wrong key may result in damage or deterioration of the grooves. The Bristol keys are a variant of the previous ones named. They have special grooves that, by their own design, allow all the torsion weight to remain at the level of these grooves. Bristol keys are generally used in aviation, cameras, and construction machinery.


The  importance  of the Allen key lies in the ease with which it allows the adjustment or loosening of the most suitable screws for many products. Be these cameras, aviation equipment, construction, among many others.

Leave a Comment