10 Different Types of Allen Keys

Different Types of Allen Keys
Photo by Mika Baumeister

Allen or hex keys are essential in any mechanic’s toolkit. Not just for working on bikes but also for furniture and appliances.

These appliances often require a hex key to tighten screws and bolts. Several different types of Allen keys are available, each with a special purpose and unique design.

This article will explain some of the most common uses for these different types of Allen keys. This is so you can choose the one that best fits your needs!

1. Spline Drive Wrenches

The first type of key we will be looking at on our list of different types of Allen keys is the spline drive wrench. This key is often found when a bolt can’t be reached from either end.

Also, if there’s some obstruction preventing you from getting to it from one side. These wrenches come in different sizes with holes on either end for holding screwdrivers, ratchets, etc.  

2. Key Ring Sets

key ring sets are basic L-shaped Hex or Toque keys mounted on a key ring with a spring retaining clip, allowing them to be removed and replaced easily.

These different types of Allen keys have a distinctive ‘T’ handle grip. This makes them easier to hold than those without handles. 

Also, they come in sets of six to 10 tools which are color coded so their purpose can quickly identify them. For example, one type may be yellow for cutting pipes and another blue for removing screws or nails.

Steel quality determines how well it will resist corrosion due to moisture exposure. Stainless steel resists corrosion better than chrome vanadium or carbon steel Allen keys.

Though not as well as high carbon stainless steel keys which cost more but last longer if properly cared for.

3. Hex (or six-sided) Wrenches

A hex (or six-sided) wrench is typically used on a bolt that is inside a hex-shaped hole. These wrenches are among the different types of all keys that are easy to use.

This is because the pressure from turning them tightens down the bolt and creates a strong seal. If you’ve ever fixed anything around your house with hex-shaped bolts, then you’ve probably seen one of these tools.

An Allen key set consists of anywhere from 1 – 15 Allen keys in varying sizes, depending on the type. When using an Allen key set, you would usually start with the smallest size first to ensure it fits, then move up to larger sizes if it doesn’t fit.

4. L-shaped Hex key Sets

There are many different sizes available for L-shaped hex wrenches. The standard size is a 6mm hex key set which is handy for working on bikes, motor vehicles, furniture, gardening tools, and many other household items. 

The most popular size that you’ll find in your local hardware store is the 5mm hex key. This can be used for power tool accessories and eyeglass frames.

Other commonly found sizes include 3/16, 1/4, 5/16, 3/8, and 7/16 Those larger than 8mm may require an electric drill to get them started. 

Due to its L-shape, it can reach into tight spots a screwdriver cannot reach. This makes it perfect for projects like repairing eyeglasses and assembling IKEA furniture.  

5. Square Bit Allen Key

If you have a screw that is difficult to access, try using a triple square bit to remove it. This is among the different types of Allen keys with the square on one end with two crossed bolts on the other.

This tool allows you to reach down into tight places you couldn’t before. Also, remove screws in areas like a motorcycle wheel or hidden behind a dashboard. 

A square Allen key bit looks like a long, thin box with three bolts sticking out at each corner. It’s best used for recessed bolt heads or removing screws without any space around them to get the driver or ratchet in place. 

6. Double-Sided Hex Keys

One of the types of  Allen keys that many people commonly use is the double-sided hex key. This tool can be used on both a right-hand threaded screw and a left-hand threaded screw. This makes it an extremely versatile tool for any job that you are working on. 

Also, it is referred to as an Allen wrench since these types of keys were invented by John W. Holt, who was from Iowa City.

This key works well for smaller screws but not so well for larger screws or bolts, which will require something much more heavy-duty.

7. Socket Adapters

A socket adapter is a wrench with a hexagonal head that is screwed into a socket so it can attach to an object. The shape of the hexagonal head allows for adjustable contact pressure.

It means that it works for both metrics as well as standard sizing. This makes it a versatile tool that can be used on many different types of objects. 

The most common use for these tools is on bicycle pedals, but they also come in handy when assembling furniture or other household items. Some adapters have the wrenches integrated into them, while others are separate from the socket holder.

8. Triple Square Bits

If you have a bolt head that is out of reach, a triple square bit is among the different types of Allen keys that can be inserted into the bolt head from the side.

This is usually done with an Allen key wrench on one end and torque for added grip on the other end. To loosen, just reverse the process in reverse order. Many old screws require an Allen key for removal as well.  

9. Ratcheting Drivers

The ratcheting drivers can be used in tighter places or restricted access. The handles on ratcheting drivers also have a lot of grips, so they will not slip out like other different types of Allen keys.

They also make it easy to take wrenches off by providing a quick release button. These buttons allow you to rotate away from each other instead of pulling them off, which could cause damage to either tool or surface. 

With ratcheting drivers, you have better control when fastening screws. This is because the handles only rotate in one direction when closed. It’s easier for people with arthritis to use them as well.

10. P-handle

The P-handle is next on our list of different types of Allen keys. P-handle comes in handy when you need to make small adjustments.

They work better for projects that require more torque, where the 1/4 square drive head is necessary for hard-to-reach bolts. 1/4 drives are also great for getting into tight spaces because they are slim enough to fit inside most vehicle connections.

Uses of Allen keys

  • Fixing loose bolts: Used as an alternative to tightening a bolt if the bolt cannot be tightened sufficiently. Softer material allows it to hold fasteners, while round heads help with tough-to-reach areas. 
  • Removing tight bolts: When a bolt is difficult to remove or thread, the threads may be worn out. A hex head will not slip off the head, giving you a better grip. 
  • Loosening stuck nuts: If you need to get a nut off that is too tight, an Allen key should fit nicely into the recess around the nut for your screwdriver’s purchase. This can be handy for tiny screws as well. Sometimes you’ll see those little screws that are next to impossible to reach without some sort of lever. This is what an Allen key is perfect for!  
  • Prying open fittings: Allens come in many shapes and sizes, so there’s bound to be one just right for your project.  
  • Used to loosen or tighten various bolts. Some different types of Allen keys allow excess dirt and grime to build up in them to fall away during use. The best choice when loosening bolts is because it won’t ruin the threads on either side, making removal easier later.

Tips to Take Care of Allen Keys

Here are tips to take care of the different types of  Allen keys: 

  • Always store them in a cool, dry place when not in use, so they don’t get rusty. 
  • Use your fingers instead of pliers to turn the tool when removing it from the bolt or screw head. This will prevent any stripping or damage. 
  • Use penetrating oil on stubborn bolts and screws before trying to loosen them with an Allen key; this often does the trick.
  • Use only as much pressure as necessary when turning. Too much pressure could lead to breaking off teeth or stripping out threads inside the tool.
  • If you want to remove rust from an Allen key, scrub it down with steel wool and wipe away the residue. You’ll want to do this outside or over a sink since it might create some dust. 
  • Be careful about making contact with the raw metal parts, though, since there may still be enough moisture left on the tool for the steel wool to create sparks. 
  • You can also purchase Allen key polish, which may make things easier if you’re having trouble finding one that has been lost or misplaced.


Allen keys are used to turn screws with hexagonal sockets in them. They’re commonly used by electricians, plumbers, hobbyists, and automotive technicians (to name just a few). So knowing how to use them correctly is important if you work in any of these industries. 

There are many different types of Allen keys (and quite possibly even more different types of screws). This article has helped you to break down the most common ones you’ll encounter.

Also, to help you understand how to use them effectively. You can now choose the one that best fits your project.

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