How to Choose the Right Set of Hex Keys

If you have ever purchased a piece of RTA (ready to assemble) furniture or have done work on a bicycle or motorcycle, you have either directly or indirectly become involved with a hex key. These are handy and efficient tools with a lot more to their history and use than meets the eye.

As it implies, a hex key has a shaft with 6 equal sides that form a hexagon. When comparing a hex head fastener to a standard Phillips or slot screw head arrangement, it is pretty clear to see that a screw head with a 6 sided (hex) socket is going to allow the application of more torque with consistent force than either the slotted or Phillips type screw. In addition, the hex key lends itself for use with socket head cap hex screws, which can be seated flush with the surface of the work to provide a smooth uninterrupted surface.

You might think hex keys are a recent development, but in actuality they were first patented by William G. Allen about 1910. Allen clearly recognized the benefits of this type of arrangement, and as a consequence, hex keys are also commonly referred to as Allen wrenches. Hex keys are defined in both metric and SAE (Society of Automotive Engineers) / Inch sizes. Common inch sizes are 5/64, 3/32, 7/64, 1/8, 9/64, 5/32, 3/16, 7/32, and ¼ inch. Metric sizes are most commonly 1.5, 2.0, 2.5, 3.0, 4.0, 5.0, 6.0, and 8.0mm. You would probably find that the 4.0, 5.0, and 6.0mm sizes are the most common.

Just to diverge a moment, torx is an alternate socket style fastener configuration that was originally developed by manufacturers to make their products tamper proof, but this has worked its way into the mainstream, and now torx fasteners and the necessary tools to work with them are common. Similar to a Phillips, which has 4 points, torx has 6 points which allows for uniform distribution of torque. In addition, since the socket has a flat bottom and the torx tool has a flat tip, the tool can be inserted 100% of the way into the socket to provide maximum application of force with a minimum threat of coming out. This is a huge advantage in applications that require significant torque/tightening force.


Hex keys commonly supplied with ready to assemble furniture are, generally speaking, modest affairs made from carbon steel that are intended to last little more than the time it takes to assemble the piece of furniture. Good quality hex key sets are made from alloy tool steel and are going to last a long time. Typical hex keys are an L shaped affair, and depending on the application and manufacturer, come in various sizes all with legs of uneven length. This gives you the opportunity to maximize leverage by using the longer leg, but also to maximize speed by using the shorter leg to apply force.

Other variants that use similar principles are a T shaped arrangement with a rubber or plastic grip that has a long leg of the hex extending like a screw driver blade, and the short leg extending through the T. These are handy and are usually sold in sets with an indexing device. People doing bench top work like gunsmithing find this type of hex wrench useful. The other common, and extremely useful, variant is the type of hex key set that folds into an integral storage device in a manner similar to a folding pocket knife. When the key is pivoted out of its storage holder and held at 90°, the handle is able to apply leverage for both removing and tightening fasteners.

Hex key sets are available online through many outlets and available through many retailers such as Home Depot, Lowes, Menards, and specialty tool manufacturers such as Kennedy, Snap-On, Dewalt, Stanley #STHT71839, Ryobi, Klein 70591, Husky, Kobalt, Tekton #25152, Bondhus, and Tech Team Products. The hex key set that we were most impressed with is the model 717 manufactured by Tech Team Products under the brand name Tech This is one of those clever items with a function representative of a folding pocket knife. It has all of the above mentioned sizes in metric in one holder with color coded comfortable TPR grips, SAE/ Inch in the another holder, and in addition it includes a set of Torx keys in the following sizes: T9, T10, T15, T20, T25, T27, T30, and T40.


To properly use one of these insert/socket head fastener and tool arrangements, you need to follow several steps.

  • First, determine the screw head configuration and the correct size and configuration of the tool to make the proper fit. Using an under sized tool will invariably result in stripping the screw head and an unsatisfactory result. Therefore, careful examination of the screw head and applying the tool to make certain that the fit is snug and tight is absolutely essential.
  • The next step is to position the tool so that it is inserted to full depth into the socket of the screw head in order to avoid coming out, which basically is allowing the tool to twist upwards and out of the screw head and in the process damage the socket. Next, determine the rotation. This is where you pay attention to the old and trite expression “righty tighty, lefty loosey”. Generally speaking, with right handed threads tightening is accomplished by turning in a clockwise direction. Correspondingly, loosening is accomplished by turning in a counter-clockwise direction.
  • Next, always attempt to apply force in a uniform, even, and consistent manner without jerking. Sudden surges in force can damage the socket in the screw head or actually twist the screw head off.
  • Finally, if there are multiple fasteners, you need to work in successive stages so that the parts being joined together have uniform contact. In other words, start at the center and work your way towards the edges screw by screw, tighten each one to marginally snug, and then repeat the process gradually applying more force until everything is snugged down sufficiently. You need to pay close attention to this when using a power drill or power hex key driver.