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What is an Allen Wrench?

These are dark allen wrenches in various sizes in a ring.
  • An Allen wrench is known as one of the simplest and most common hand tools you should have in your tool box. 
  • It has a variety of uses, from fixing your motorcycle to putting together assemble yourself furniture. 
  • You can buy Allen wrenches as individual pieces or in complete sets, which are more affordable and less likely to get lost. 

An Allen wrench is not a complicated tool, but it has many different uses. You simply hold it in your hand and produce a large amount of torque to turn another object, typically a screw. An Allen wrench is also called a hex key or a hex key wrench.

No matter which term is used, the tool remains the same. You absolutely need a set of Allen wrenches in your toolbox. So, if you are still asking what is an Allen wrench; keep on reading to find the answers to all your questions. 

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What is an Allen Wrench?  

This is a single steel allen wrench on a white surface.

An Allen wrench is a tool that can be held in your hand and is powered by your hand. It is not an electric tool. One or both ends of an Allen wrench have a hexagonal cross-section to fit in many different screws with recessed holes of the hexagonal screws. An Allen wrench has six points of contact to help prevent stripping screws like other screwdrivers have a tendency to do.

Allen wrenches are available in the metric size and SAE fractional inch sizes. You can buy them separately or in a set. The sets include the most popular sizes and are the most cost-effective options. They are available in sizes from 1.5 mm to 10 mm. 

What Does an Allen Wrench Look Like?

An Allen wrench is an L-shaped tool that has arms that are of unequal lengths. It has blunt ends that are hexagonally shaped, which means it has six sides to fit into screws and bolts with a hexagonal-shaped socket in the head. An Allen wrench is usually forged of one piece of hard steel that creates a right angle. 

Some Allen wrenches come as part of a folding set. All of the wrenches are in a housing that keeps them compact and all in one place. Unfortunately, they are attached to the housing and cannot be removed, which may make it difficult to use them in a tight space. 

Each Allen wrench is a different size, and the larger the hex size, the longer the arms tend to be. However, there are some standard sizes you can expect to find. 

These include:

Hex size = 1/16 inch

Long Arm = 91 mm (3.58 inches)

Short Arm = 15mm (.59 inches)

Hex size = 5/64 inch

Long Arm = 100 mm (3.93 inches)

Short Arm = 16 mm (.63 inches)

Hex size = 3/32 inch

Long Arm = 112 mm (4.41 inches)

Short Arm = 18 mm (.71 inches)

Hex size = 7/64 inch

Long Arm = 199 mm (7.83 inches)

Short Arm = 19 mm (.75 inches)

How Can I Use an Allen Wrench?

An Allen wrench has a very specific shape, so it can only be used for specific items. This tool is ideal for furniture that you assemble yourself, bike repairs, motorcycle engines, and any other item that uses an Allen bolt also known as a hex bolt or Allen screw with a set in a hexagonal shape. These tools are light and small and allow you to get into hard-to-reach and small spaces. 

Typically, when you use an Allen wrench, you put the short end in the bolt head and press down on the longer side to turn the bolt. This gives you the most leverage. However, when you are working in a small space, you may need to put the shorter side of the Allen wrench in the bolt, which helps you fit in the space but will not give you as much torque to move a hex socket screw. 

An Allen wrench set works like a typical wrench or screwdriver, but with some minor differences. You place the Allen wrench in a hexagonal socket. You turn the wrench to move the hex fasteners in the direction you want.

If you move the Allen key in a clockwise direction, it will tighten the set screw. If you turn it counterclockwise it loosens and removes the fastener. 

Who Invented the Allen Wrench?

Allen Wrenches have a long history, and it is difficult to know exactly who the first inventor was of the Allen wrench. It was patented as early as 1860 under various names. There were 30 patents filed at the same time for the Allen wrench, so it is tough to say who was first.

However, the first person to produce it was William G Allen of the Allen Manufacturing Company out of Connecticut. This was 1910 and when it officially was called the Allen wrench even though there were many other torque wrench options. 

Why is it Called an Allen Wrench?

The technical name for an Allen wrench is actually a hex socket key or hex key. The Allen Manufacturing Company was the first to manufacture a version of a hex key that they called the Allen wrench.

A hex key is a commonplace tool that many have always referred to as an Allen wrench. There are many different manufacturers of hex keys.

Materials Used in an Allen Wrench

This is a side view of a single dark allen wrench.

You can expect to find that just about any Allen wrench you buy is made of some type of steel. The steel in the Allen wrench may be alloyed with one of several different materials. There will be anywhere from 50 to 90 percent steel in your Allen wrench.

The other material could be chrome vanadium, stainless steel, high tensile steel, chrome vanadium steel, protanium, or chrome vanadium molybdenum (CVM).

Variations of an Allen Wrench

Ball End Wrench

These are the ball end tips of Allen wrenches in various sizes.

Most of the Allen wrench options you see have a flat end on both sides; however, there are some that have a ball end. These ball-end hex keys are a type of Allen wrench that is intended to fasten a nut at an angle. This is ideal for tight spaces. 

Long Arm Wrench

A long arm Allen wrench is one that has a longer vertical length. All of these wrenches have a more extended arm on the vertical side, but the long arm versions have an even longer vertical side. 

T-Handle Wrench

These are T-Handle allen wrenches in various sizes.

The T handle hex key wrench gives you more leverage and better reach. This tends to be a popular tool for machinists, mechanics, and motorsports. The handle allows you to spin the wrench fast while still giving you the leverage you need. 

Allen Screwdriver

This is a combination of a screwdriver and an Allen, or hex key, tip. This hex driver gives you little torque but allows you to work in a smaller space. This tool is ideal for adjusting levers. The most common sizes are 1.5 mm to 5 mm.

Key Ring Sets

These are various sizes of allen wrench held together with a key ring.

This is a basic set of L-shaped Allen Wrenches, or hex keys, that are mounted on a key ring. They have a spring retaining clip holding them on. The ring allows you to keep them together and put them in a convenient place in your house or car.

You can easily remove one of the Allen Wrenches by twisting and pulling. 

Ratcheting Drivers

These are ratcheting drivers and screw bits with rusty surfaces.

A ratchet driver gives you more significant speed over a more traditional Allen wrench. A ratcheting driver can also be more dynamic because it can be used with other bits, like those for a screwdriver or sockets.

The bits from a ratchet driver can also be used in an electric drill driver. It is ideal for those working with bolts for a rotor. 

Folding Allen Keys

This is a Swiss Army folding allen wrenches.

This is a set of Allen keys all contained in one place, which is the handle of the wrench. This way, you will not lose your Allen key and can always find it when you need it. The folding hex key is a set of Allen key options that fold out 90 degrees from the handle to provide you with the maximum amount of torque. 

Torx Key

It is possible to use a torx key instead of an Allen key, but it is not recommended. You should use a torx key solely for a torx screw. If you find yourself with no other options as an alternative to your hex wrench, and you are desperate, you can use a torx key.

You will want to keep in mind that it is possible to break your torx key on a hex screw. A T7 torx is close to a perfect fit for a 2 mm (5/64 inch) Allen wrench. A T9 is a great fit for a 2.5 mm. There are other close fits but keep in mind the tip of a torx key is fragile and can be easily broken. 

Adjustable Wrench

An adjustable wrench has many uses because you can adjust it to whatever your need is, no matter if it is fasteners that are metric or standard. An adjustable wrench has a jaw that can be moved and then fixed in place to fit perfectly on the fastener head. An adjustable wrench can be used to loosen or tighten angled screws or nuts.

Most often they come in three different sizes, which include 200 mm, 250 mm, and 300 mm. Adjustable wrenches are typically used by electricians and plumbers. They are used primarily for repairing cars and building furniture.

You chose the adjustable wrench based on the size of the nut, and it cannot be used in reverse. 

Crowfoot Allen Wrench

A crowfoot Allen wrench is close to an open-end wrench or a box end wrench. The major difference between them is they do not have a handle or a shaft. The back of the wrench’s mouth is open.

A crowfoot Allen wrench has a snug fit on a nut or bolt making them perfect for the smallest space. The crowfoot Allen wrench is ideal for valve adjustments, power steering, clutch, and brakes.

This is an ideal tool for use by mechanics, especially those in aviation because they use this type of wrench regularly. This tool is often used with torque wrenches and ratchets. 

Are There Alternatives to an Allen Wrench?

There truly are not many alternatives to an Allen wrench. You may be able to use other tools to get the job done, but they are not a true alternative. 

This is a close look at various screwdrivers in different sizes.

You may be able to use a small flathead screwdriver in place of an Allen wrench to get the screw head or bolt loose. If you can find two that are small enough, you can wedge them in the bolt to get it to turn without stripping it. 

You may be able to use items that you find around your house, like a butter knife, or tweezers, or even nail clippers that you might be able to wedge in the bolt to get it to loosen. If you can apply enough pressure or torque with these items, you should be able to loosen them. 

Pros and Cons of an Allen Wrench?


  • An Allen wrench is incredibly affordable.
  • They are easy to produce. 
  • They give you a large amount of torque.
  • Allen Wrenches are less likely to strip or damage screws. 


  • An Allen wrench does not work well in a very small space. 
  • You may not have fast engagement. 
  • They are easy to lose. 

Where to Buy an Allen Wrench

You can literally get an Allen wrench just about anywhere. You can go to your local hardware store to pick on up. You can go to Walmart or order them online at Amazon.

You can find them at Target and even on eBay. They range in price. You can find a single Allen wrench for just under $1. You can also find lovely sets of them for over $20. These are relatively inexpensive tools that you probably do not want to spend a lot of money on.