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Are Allen Wrenches Hardened?

This is a table with various sizes of metal Allen wrenches.

An Allen wrench, also known as an Allen or hex key, is a very versatile and easy-to-use tool. I have used one to put together Ikea furniture, and it worked quite well. The one I used felt sturdy enough, and I had no problems with fastening things.

Today, many people use Allen wrenches for all sorts of things, and in most instances, the job requires the hex screw to be strong. This leads to the question, are Allen wrenches hardened? Let’s find out.

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What are Allen Wrenches?

To begin with, an Allen wrench is a small tool with a big purpose. Its defining characteristic is the L-shape that makes for a handy grip during many manual operations. There are also heads with the hexagon shape on both ends that can fit inside and loosen a fastener when turned counterclockwise or tighten them when turned clockwise.

Some Allen keys even come with a ball end, which makes the key easier to slide into fasteners.

The name Allen wrench is derived from its maker, William G. Allen, and the Allen Manufacturing Company later patented this great invention. Today, Allen wrenches are used all over the world and favored because they’re a ridiculously simple and inexpensive tool that allows for the easy installation and removal of fasteners without the need for power tools or a special bit. This is all thanks to the hex head that has a strong grip action when fitted into the matching hexagonal socket. 

This is a close look at a screw being screwed in with the right allen wrench.

Generally, consumers use Allen wrenches for the following tasks:

  • Repairs. Typically, hex keys are great for bicycle repairs, and they come in assorted sizes that you can carry around, so you can make repairs on the go.
  • Electronics. Allen wrenches are also one of the dominant tools for people that repair electronics. That’s because of their compact size that suits the compact nature of some electronics.
  • Furniture. This is one of the more popular uses of Allen wrenches. Typically when you buy furniture pieces, they’re often accompanied by an Allen wrench – the essential tool for putting everything together.
  • Vehicles. Allen wrenches also come in handy for car and motorcycle repairs. They can easily be used when trying to access those hard-to-reach areas, such as under the seat and behind the glove compartment, instead of using a screwdriver, which can be awkward to handle.
  • Tools. Some Allen wrenches are used to keep heavy tools and machinery in good condition. For instance, they’re used to replace blades in power saws.

Why Should Allen Wrenches Be Hardened?

This is a close look at various sizes of stainless steel Allen wrenches.

As you can see above, Allen wrenches need to be highly durable if their function involves things like car repairs. This may not be relevant for normal household use, but in any case, the last thing you need is to worry about the Allen wrench you’re using suddenly snapping off in your hands. 

The good news is there are many hardened Allen wrenches on the market. If you regularly use Allen wrenches for heavy-duty stuff, don’t trust those free ones that come with your furniture pieces. You need something more durable that won’t break, even if you apply a significant amount of pressure.

How Are Allen Wrenches Hardened?

Allen wrenches come in various qualities. The cheap ones are usually made from inexpensive steel grades. However, you can also find those made from hardened and high-quality steel grade.

Generally, steels are hardened during manufacture by first heating them to a temperature between 800-900°C. 

The steel is then rapidly cooled by immersing it in oil or water. Finally, it’s tempered to remove some of the brittleness caused by hardening and to make the steel tougher. The explanation behind this is when steel is cooled rapidly, its atoms become fixed in an unstable arrangement.

Although the steel has been hardened, it’s very brittle. However, tempering allows the metal’s atoms to rearrange in a more stable configuration, which reduces the likelihood of the material breaking or fracturing easily.

To temper the steel, it’s re-heated at a lower temperature, which improves the steel’s mechanical processes. Usually, any type of steel that contains more than 0.3% carbon will respond to this type of treatment. An example of high-carbon steel is chrome vanadium steel.

Allen wrenches made from this type of hardened and tempered steel are very durable and will maintain their surface integrity when performing tasks.

Can I Harden an Allen Wrench at Home?

This is a mechanic wearing red overall holding a large wrench.

Yes, it’s possible to harden a hex key at home, but generally, it should only be done by experts to avoid accidents and potential injuries. The process is the same one used in industrial and tempering of steel. 

Since Allen wrenches are pretty compact tools, the process will be faster. All you have to do is heat the key wrench until it’s red hot or until it stops attracting magnets, then quickly quench in oil or water. Sometimes the Allen key won’t harden when quenched in oil, so you’ll have to try with water or vice versa. 

Once the metal hardens, you can test it with a file. If the process has worked, the file will skate across the surface instead of biting in. 

After hardening, you’ll then have to polish and re-heat the metal until it’s a blue or straw color. With tempering done, you’re all good to go! While the process is short and simple, it might take a while to master.

So you might want to experiment with scarp Allen keys first until you’re confident you have the hang of it.

Where Do You Find Quality Hardened Allen Wrenches?

These are various sizes of steel allen wrenches.

As mentioned earlier, Allen wrenches are many from a wide range of steel grades and qualities. If hardness, stress relief, and stress treatment hasn’t been factored in during treatment, you’ll find that the Allen screw will have poor tensile strength, meaning it can snap easily. 

Ideally, you want something with a longer lifespan unless you usually use the wrench for low torque applications. Otherwise, you might end up dealing with the long-term costs of replacing your Allen wrenches regularly. 

So, if you’re in the market for some quality and durable Allen wrenches that are hardened, here are some tips to keep in mind:

  • Heat treatment. A good quality hex wrench is characterized by toughness, and that typically means it’s been heat treated to harden and tempered. Keep in mind this is what makes metal strong without being brittle, so your Allen wrench will offer a superior experience in high torque applications.
  • Rust resistant coating. It’s also good to look for an Allen wrench set that’s been treated with rust-resistant coating. Even if the wrenches are strong, you’ll still want them to maintain their pristine appearance on the surface level.
  • Carbon content. When steel has a higher carbon content, it responds better to hardening and tempering. Generally, it’s best to look for Allen wrenches made from steel that has a carbon content of at least 0.5%, for example, chrome vanadium steel.
  • Customer reviews. Don’t forget to also check online customer reviews to verify if the Allen wrench set you have your eye on offers value for your money. A great tip is to check if the smallest Allen key set has any complaints about having a short life span. The smallest ones are more likely to break, so they give a good indication of the overall quality of the rest of the hex key set.