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What Is An Allen Wrench?

What Is An Allen Wrench

Sometimes referred to as "Allen wrenches" or "hex keys," Allen keys are one of the more handy tools in both a professional and DIY environment. 

Being relatively simple in appearance, they probably don't look like the most ingenious of tools, but they have revolutionized how we deal with screws, bolts, and various other fixtures, and no toolbox should be without one. 

Instantly recognizable owing to their L-shaped (or T-handle) appearance, Allen keys provide a rather clever way of accessing and tightening screws which are usually recessed, or when other tools may be more 'awkward' to use.

If you have ever been frustrated with slotted screwdrivers slipping out of screw slots or a tough Philips screwdriver stripping out a fragile screw head, you will understand the problem (which is annoying, to say the least). 

This was a headache that Allen Keys solved instantly and the main reason why they have become so widespread over the last few decades: they don't let you down.


Coming in a range of sizes (from basic metric to SAE) and known for being heavy-duty, tough, and durable, Allen Keys are made of hard metals and alloys like heat-treated chrome vanadium steel. They are built to last, and as such, Allen Keys are not usually the type of tool you tend to replace (unless you lose them, of course!).

Allen keys are frequently used for a huge number of jobs like assembling furniture, putting up shelves, or servicing a bicycle, to give just three of many examples. With the Allen key's ability to grip, tighten, and loosen almost effortlessly, it is a pretty essential tool in everyone's toolkit, from pro tradesmen working on-site to factory workers on an assembly line (or homeowners tinkering around the house).

Interestingly, Allen Keys - or hex keys, as they are also known - were viewed with mild suspicion when they were first introduced to the market but are now considered a basic essential in any toolkit. This growth in popularity has led to further innovations way beyond the 'basic' Allen Key, with a range of different options now available.

Through this article, we will look into the world of the Allen key. Starting with a quick look at the history of this handy little tool, we shall then consider the various types available and the range of applications that hex keys are useful for.

Frankly, it's about time! This humble little tool deserves a thorough write-up, and that is what we have for you right here. The Fastenere guide to all things related to the Allen wrench, Allen Key, Hex keys, Hex Wrench (or whatever you choose to call them).

But first, who is this mysterious 'Allen' figure, anyway? It turns out that this versatile tool owes its name to a gentleman by the name of W.G. Allen, to be precise. Let's take a little look at its history.

Short History of the Allen Key

The early years of the Allen key go back to the start of the 20th century, with the first patent dating back to 1909. Now, there is some contention as to who the exact inventor was - apparently, it was something of a team effort rather than a solo endeavor - but the patent is indeed owned by W.G. Allen of the Allen Manufacturing Company in Hartford, Connecticut. 

Hex keys were born, and "Allen wrench" became a casual name for the tool that basically stuck until the terms "Allen key" and “Hex Keys” were more widely used.

Hex Keys were an eventual hit because of their clever design that proved far more efficient than traditional tools (such as screwdrivers) when it came to fixing socket screws. As socket screws gained traction in the manufacturing industries, the demand for the Allen key skyrocketed.

Over the years, as machinery and products became more complicated, the Hex Keys evolved to meet these demands. Originally made from iron, the introduction of a metric Hex Key set, along with more wrench sizes and materials like heat-treated chrome vanadium steel, saw the first variations.

Varying length options became available soon after (from short arm to long arm), making it adaptable to a broader range of uses. Further design improvements - such as the ball end design, for example - allowed for angling the Allen key wrench.

As industries grew and manufacturing requirements changed, Hex Keys not only adapted but became far more widely appreciated, becoming a firm part of modern construction and assembly.

The Allen Key is now 'officially' produced by The Apex Tool Group, but with an original patent that has now long expired, there are thousands of different companies worldwide manufacturing and retailing the Allen Key.

Types of Allen Keys Available

You would be forgiven for thinking that the Allen Key is a fairly straightforward tool, and for the most part, it is. With a hex-shaped end and an L-shaped appearance, they are uncomplicated in nature. However, there are quite a few variations available, with multiple types created for specific tasks or even preferences.

Spoilt for choice might be the operative phrase when it comes to Hex Keys, with each design and style offering a different set of benefits. As with most hand tools, certain types of Allen wrenches are more suitable for specific jobs than others. Let's take a look at these variations in more detail.

Standard vs. Metric Allen Keys

For the most part, Allen keys are available in two main sizing standards known as metric and SAE, whether bought as single Allen Wrenches or full Allen Wrench sets. Metric sizes are offered in millimeters (and tend to cater to the global market), while SAE sizes, which are usually noted in inches, are standard in the U.S. 

One common issue with global variation in sizing is that a mismatch can cause stripped screws and damaged keys. While that might sound quite obvious, you would probably be surprised how commonly that mistake is made, so be careful!

T-handle vs. L-shaped Design

The L-shaped design is the traditional shape most people recognize with Allen keys, with a design simplicity that offers easy storage and quick access. The T-handle variant is becoming more popular over recent years, providing a stronger and more ergonomic grip, with more leverage available when loosening or tightening screws. 

This is especially useful for tasks requiring longer periods of wrenching, reducing hand fatigue and providing a more comfortable experience when using the Hex Key. If you need a little extra firepower, the T-handle should do the job nicely.

Long Arm vs. Short Arm Hex Keys

Allen wrenches come in lots of different lengths, including short-arm and long-arm variations. The long arms can reach recessed screws more easily, giving the additional advantage of more overall torque and leverage. By the same token, the short-arm Allen Wrench is probably better for tight spaces (where a long arm might be slightly cumbersome).

Ball End Allen Wrenches

Ever noticed how small ideas sometimes lead to the biggest innovations? The Ball End Allen Wrench definitely fits into that category, being a small idea that firmly ticked the innovation box, so to speak. Ball End wrenches have a rounded tip, which rather cleverly allows users to fit the wrench into a screw at more of an angle. 

This design is incredibly handy in situations where a straight approach is blocked or a pain to access. Ball Ends allow users up to a 25-degree angle of entry, making tightening or loosening screws in tight spots quite effortless.

Materials & Finish

The construction material of an Allen key is an important factor because of its durability. As soon as you pick up an Allen Wrench, you will notice a really sturdy, satisfying weight. They just feel reliable in some strange way. Chrome vanadium steel is always a popular choice with any tool, as it is known for its general toughness and resistance to wear.

On top of that, there is usually a black oxide finish on Allen Wrench sets that gives it a nice appearance while also providing an added layer of protection against corrosion and wear over the years. In most cases, you can use an Allen Wrench for decades, and it will still look new.

While the main function of an Allen Wrench is always the same (to fix hexagonal sockets, screws, and bolts), the wide range of types available ensures you can find the perfect tool for every job. 

Whether you are assembling a flat-pack cabinet, fixing the height of a bicycle seat, or even working on expensive, delicate machinery, there will be an Allen Wrench suited to the job at hand.

Features to Look for in Allen Wrench Sets

We probably shouldn't overcomplicate things too much - the Allen Wrench is, after all, quite a simple (but ingenious) tool. That said, choosing the right Allen key needs a little more thought than just grabbing any old Hex Key or Allen Wrench Set off the shelf.

Most of the larger stores offer a large range of Hex Key options. Knowing what to look for can mean the difference between a tool that lasts decades and one that doesn't quite meet the standard. 

Cheaper, poorly made Hex Wrenches will only lead to disappointment. Before making a purchase, you should think about the key features that make an Allen wrench unique. Let's take a look at what they are.

1. Material & Construction

The quality of an Allen wrench depends largely on the materials used when it is forged. Chrome vanadium steel is easily the best choice because of its tough durability. When forged and heat treated (as any good Hex Key should be), this material will ensure your Hex Key sticks around in your toolbox for a decent length of time. 

This type of steel also tends to withstand high torque without deforming, so if you are expecting tougher jobs, this must be your go-to material.

Something else worth looking out for is Hex Wrenches which come with a black oxide finish, which gives good protection against rust and allows a better grip with screws. Most Hex Wrenches these days are indeed made with this finish, but if it isn't, you might want to avoid it. 

Also, avoid shiny chrome finishing if you can: that type of Hex Key is usually synonymous with cheaper, poorly made tools.

2. Size Variety

A good Allen wrench set usually includes both metric and SAE size options, which will determine the right tool for the task. Most people in America use metric sizes, but SAE sizes are also used by many. With that in mind, it probably makes sense to choose a Hex Key that offers both.

3. Design Variations

Depending on the task, having both long-arm and short-arm Allen keys in your toolbox is always a good thing. Generally speaking, a long arm offers more leverage and greater reach, while a short arm is mostly better for those tighter and more awkward spaces. 

In the same respect, T-handle designs tend to provide more leverage and comfort during constant use. A Hex Key will not be a particularly expensive purchase, so just go ahead and grab both.

4. Ball End Design

With their rounded tips, Ball End Wrenches allow for angling, making them useful in situations where a straight-on approach is tricky. Again, the same rule applies when it comes to the material: make sure the ball end design is precision-engineered and will fit snugly into screws without slipping or stripping.

5. Ergonomic Features

As many of you reading this will attest, using any tool for extended periods can strain the hands, but with a Hex Key, even more so. The angled design can sometimes feel a little uncomfortable in the hand if used for longer periods of time. Ergonomic features - like cushioned grips or T-handle designs - can provide a more comfortable experience, reducing fatigue and enhancing grip.

6. Portability & Storage

Try to look for sets that come with storage cases if you don't mind spending that little extra. Not only do these cases keep your keys organized, but they also protect them from potential damage and make transportation more straightforward. 

A toolbox that rattles with loose Hex Wrenches is never ideal. So, avoid this by purchasing an Allen Wrench set that comes complete with a lovely, organized, neat box.

Better still, many Allen Keys these days come in an extendable 'pop out' tool format, almost like a Swiss Army Knife. The idea is to pull out the Hex Key you need, leaving the others neatly folded away. Quite handy, actually.

7. Versatility

Many Allen keys come with features that offer better versatility. Like those, for example, that have a 'T-handle' that can be attached to a torque wrench. This allows for a more precise torque delivery and can be really useful for tasks requiring more brutal torque.

8. Clearly Marked Sizes

Any good tradesman will tell you that time is of the essence when working on various projects. You might be surprised how much time is spent each day straining to look at poorly engraved tool sizes. 

A Hex Key with a clearly marked size - either stamped, engraved, or laser-etched - enables quicker identification and selection, streamlining the work process. Now, this might sound like an unnecessary consideration, but these small details always add up to make your day a little easier!

Common Hex Key Uses

If you think the Hex Key is only useful for throwing up a few shelves, building a flat-pack coffee table, or fixing a bicycle, think again! The Hex Key is an invaluable tool with a whole range of use cases in various industries and day-to-day life.

Let's take a look at a few examples - starting with (arguably) the two most common - those shelves and bicycles we just mentioned.

Furniture Assembly

One of the most common uses of Allen Wrenches is in furniture assembly. These days, most flat-pack furniture items (from popular brands like Ikea, for example) come with their own 'miniature' Allen Wrenches, used to tighten and loosen screws that keep the pieces of furniture securely attached. 

We would suggest discarding the tools after use, though. A full Allen Wrench set is far better to keep at home than a poorly made Ikea Hex Key, designed to put a table together in a hurry!


Most cyclists and bicycle mechanics keep a Hex Key (or full Allen Wrench set) in their bicycle toolbox. From adjusting the height of a seat to securing handlebars or fixing accessories onto the frame, Allen keys of various sizes are probably the most common bicycle tool.

Electronic Devices

You might have noticed that electronic tools are becoming far smaller these days. However, the trend towards smaller electronics hasn't reduced the need for Allen Keys, which are frequently used in computer builds, adjusting electronic devices, and electronic repair/service jobs.

Automotive Work

Obviously, wrenches and sockets are the most common automotive repair tools, with the vast majority of mechanical jobs involving the wrench and socket combination. Allen keys also play a pretty big role, however, especially in places where space is limited. 

The tightening and loosening of specific screws and bolts under the hood (or within the car's interior) will usually involve the use of an Allen Wrench set in some way.

Musical Instruments

Most people probably wouldn't imagine Allen Keys as having a place among musical instruments, but they are becoming increasingly more used. Guitarists and drummers are certainly no strangers to using a Wrench Set, as they are constantly used to adjust guitar truss rods or maybe tune the occasional drum set-up.

Machinery & Industrial Settings

In factories and workshops, machinery such as lathes needs adjusting and maintaining regularly. Hex keys are essential in this regard, ensuring that machine parts fit comfortably and precisely. Allen Keys helps in adjusting tool holders, locking down parts, and general day-to-day maintenance tasks. 

Ever wondered how a machine component is fine-tuned? Nope, neither have we, but either way, the hex key has usually had a role in that adjustment somewhere along the line.

Home Repairs

For the DIY enthusiast working on home projects, an Allen wrench set is worth its weight in gold. Whether it's installing a new door handle, fixing a loose cabinet hinge, or putting up shelves, these keys offer the grip and torque needed and are a blessing to have around the home. 

Sporting Equipment

Again, most people would not associate Allen Keys with sporting equipment, but they actually play quite a big part in the servicing of them. From common gym equipment to more quirky items such as archery bows (of all things), the Allen Key is one of the go-to tools for a wide range of sporting goods.

Wrap Up

The good old Allen key is a much-trusted tool that has proven its worth time and time again, from simple home projects to more detailed mechanical tasks. If you are purchasing an Allen key, always focus on quality over price to ensure a nice long life in your toolbox and a good fit that won't strip out your fixings.

But while the right tool is important, the materials you're working with play a huge part as well, and a strong fastening system is just as important as the Hex Key that bolts it together. It's pointless having a quality Allen key if you are using a cheap and unreliable fastening that is liable to strip.

If you're thinking of using an Allen key, the chances are you are securing nuts, bolts, or screws, and when it comes to the quality of these fasteners, don't compromise! A quality fastener is just as important as the quality Allen Key that is locking it down.

So, whether you need durable Machine Screws, tough Wood Screws for carpentry, or top quality Socket Drive Screws for mechanical tasks, Fastenere has got you fully covered with the best range of fasteners you are likely to find anywhere.

Find the perfect fixing to your trusted Allen key in our massive range of budget screws, nuts & bolts, rivets, washers, and everything in between, right here in our online store!

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