Home » Workshop » What is Allen Wrench? Types, Sizes, Uses [Pictures & PDF]

What is Allen Wrench? Types, Sizes, Uses [Pictures & PDF]

In this article, you will learn what are the different types of Allen wrench? How to use them? and its sizes, advantages, and disadvantages. You can also download the PDF file at the bottom of the article.

What is Allen Wrench?

An Allen wrench is a driver tool used for turning bolts or screws that have internal hexagonal sockets.

They are usually made of hardened steel hexagonal rods with blunt ends that fit into equally sized screw sockets. These hexagonal rods are bent to 90º, forming two sides of unequal length, like the alphabet letter “L”.

The tool is rotated by holding it with its long handle, producing a greater torque at the tip of the shorter handle. Allen wrenches are designed according to the size of the socket and are manufactured with very tight tolerances. These tools are commonly used to fasten hex-type screws to wood, metal, and even plastic.

Types of Allen Wrenches

Following are the types of Allen wrenches:

  1. L-style allen wrench
  2. T-handle allen wrench
  3. P-handle allen wrench
  4. Flolding hex
  5. Ratcheting hex
  6. Torque wrench
  7. Allen screwdriver
  8. Ball hex
  9. Adjustable allen wrench
  10. Combination allen wrench
  11. Open-end allen wrench
  12. Socket allen wrench
  13. Crowfoot allen wrench

Read Also: The List of 30 Different Types of Pliers: How To Use Them? [PDF]

1. L-style Allen Wrench

L-style Allen Wrench

These are the standard type of Allen wrenches, readily available online or at a local hardware store. This Allen wrench is shaped like an L, so it can reach into tight spots and provide control when needed.

If you are looking for a set, this would be a perfect choice. While there are many options available on the market, there is a 1.5-10mm L size Allen wrench perfect for all needs.

2. T-handle Allen Wrench

T-handle Allen Wrench

The T-handle Allen wrench provides you to spin the wrench in an instant, introducing enough support in normal use. T-handle wrenches are one of the most popular in bike mechanics and are widely used in the motorsport industry.

3. P-handle Allen Wrench

P-handle Allen Wrench

The P-handle Allen wrench is a modified version of the L-style Allen wrench with a comfortable grip on the bend that gives it the same advantages as the T-handle. These types of Allen wrench are very commonly seen in professional workshops.

4. Folding Hex

Folding Hex

The folding hex has short arm keys that fold into a storage handle. This folding hex storage handle can be made of metal or plastic as per the requirement. Folding keys are typically used to apply maximum torque to work by folding 90 degrees from the storage handle.

However, one main advantage it gives you is that the folding keys will fold in 180 degrees or more, giving you access to hard-to-reach fasteners or replacing the fastener more quickly. They are growing in popularity among motorbike riders and cyclists.

5. Ratcheting Hex

Ratcheting Hex

Ratcheting hex counterparts offer superior movement and are available with either a folding handle design or a T-handle. They will often come with screwdriver bits. The bits are held onto the handle with the help of a magnetic bit holder, which houses the entire mechanism.

Ratching hex wrench bits are useful in electric drill drivers. Therefore, this makes them perfect for those handling rotor bolts.

6. Torque Wrench

Torque Wrench

This type of Allen wrench is used to apply a specific torque to a fastener such as a nut, bolt, or lag screw. This is similar to a socket wrench with a special internal mechanism. These are used where the tightness of the screws and bolts is critical.

It is an essential tool of any workshop, especially when working with sensitive components. However, this torque wrench is not a substitute for the hex counterparts.

7. Allen Screwdriver

These types of Allen wrench are used when your project involves tighter clearance and less torque. They look just like a screwdriver, except they have either a hex or Torx-shaped profile on the tip.

Spinner handles typically have a hexagonal cross-sectional shape that runs the entire length of the Allen wrench. An Allen screwdriver set is perfect for accommodating disc brakes and other types of levers. The most common sizes of Allen screwdrivers you’ll find range from 1.5mm to 5mm.

8. Ball Hex

Ball Hex

A ball hex is a simple tool used to turn bolts and screws with hexagonal socket heads. These are consist of ball molded heads with tight edges. The ball end of the Allen wrench makes it easy to slide the key into the receiving slot.

This allows the user to reach an offset 30-degree angle so you can get to the position you need very quickly. It’s great for getting into tight spaces that are out of reach for L-shaped counterparts.

9. Adjustable Allen Wrench

Adjustable Allen Wrench

Adjustable Allen wrenches have a movable jaw to adjust the size of the wrench and a fixed jaw point that is positioned at the top of the wrench. This is a handy tool also known as a network wrench. These Allen wrenches are available in sizes of 200mm, 300mm, and 250mm.

These tools are perfect for loosening or tightening angled nuts or screws. In addition, also used in applications such as plumbing, electric, self-assembly furniture, and car repair. If you want to have an adjustable Allen wrench then you will need to select according to the size of the wrench.

10. Combination Allen Wrench

The combination Allen wrench is designed with double-ends that is one side has a box end and the other side has an open end. The box-end Allen wrench is available with a closing ring for various diameters depending on the size.

They are often referred to as multi-purpose tools because the open end of the Allen wrench is used to loosen and tighten bolts and nuts in small spaces, while the box-end provides a firm grip around them. These are mostly found in bicycle repair applications.

11. Open-end Allen Wrench

These are the types of Allen wrench, designed to be used as a beneficial tool for narrow project areas that are usually difficult to thicker or larger wrenches. Typically, they are built with various sized openings in order to fit the required nuts or bolts. This Allen wrench has a U-shaped opening at each end that provides a firm grip for objects.

12. Socket Allen Wrench

Socket Allen Wrench

These types of Allen wrench consist of a hollow cylinder that is firmly attached to the handle end and is fitted to the bolts to loosen or tighten. Socket wrenches are considered a useful tool to use in objects of various sizes.

Since they can provide unmatched efficiency and speed, they are useful at myriad angles. They are often called ratchet wrenches.

13. Crowfoot Allen Wrench

Crowfoot Allen Wrench

Crowfoot Allen wrench tools are similar to box-end or open-end wrenches, with the only difference being that the tool does not have a handle and has an opening at the back of the face of the wrench.

These types of Allen wrench can fit into the side of a bolt or nut, as you’ve probably seen in socket counterparts. They are ideal for tight spaces and are useful in various fittings such as valve adjustment, clutch or brake, power steering, and some abs modulators.

Common Sizes of Allen Wrench

The sizes of Allen wrenches are considered based on an inch or metrics.

1. Standard size Allen wrench: The inch-based Allen wrenches are considered the standard in the industry. It will have a wide range of sizes in all kinds of sets.

2. European size Allen wrench: Metric sizes are used as the standard in Europe. This includes the typical size of an Allen wrench in mm.

Inch-based SizesMetric Sizes
1/8 inch2.5 mm
3/32 inch3 mm
7/64 inch4 mm
5/32 inch5 mm
3/16 inch6 mm
1/4 inch8 mm
7/32 inch10 mm

Advantages of Allen Wrench

  1. Allen wrenches are easier to manufacture and are more economical.
  2. The lever arch mechanism of the Allen wrench can provide increased tightening torque.
  3. The key does not run the risk of slipping, so as not to damage the surfaces around the screws.
  4. Allen keys prevent accidental separation of fasteners.
  5. Since they are used with hexagonal fasteners, they will hold the fasteners better than screwdrivers and wrenches.
  6. They have a strong gripping action that keeps the fasteners from snagging during installation or removal.

Disadvantages of Allen Wrench

  1. When most of the force applied to the edges at shallow depths, it will cause wear of the Allen wrench.
  2. If you are using your Allen wrench regularly, the tip of the Allen wrench may break. To avoid this, pay attention to the condition of the tips.

Closing It Up

As I already said above, the Allen wrench is a small tool used for turning bolts. The design is user-friendly and the price is also important when you consider that you are buying one. Allen Wrench also offers a lifetime guarantee, making it an even better value for the cost.


So for now, I hope that you have learned about the “Types of Allen Wrench“. If you have any questions or doubts about this article, feel free to ask in the comments. If you got this article helpful, please share it with your friends.

Want free PDFs directly to your inbox? Then subscribe to our newsletter.

Download PDF of this article:

About Saif M

Saif M. is a Mechanical Engineer by profession. He completed his engineering studies in 2014 and is currently working in a large firm as Mechanical Engineer. He is also an author and editor at www.theengineerspost.com

Leave a Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.