Despite seeming like a relative newcomer to the scene, the internal Torx (also known as “star”) design has been around for a relatively long time. These six-pointed, star-shaped bits were invented by Bernard F Reiland in 1967 and patented in 1971, while he was working for the Camcar Textron company. Reiland’s goal was to make a fastener head that could reliably drive at higher torque values without the dreaded “cam-out” or slipping that plagued Phillips and hex screws in a production environment. Reiland felt that with new tools that were much more controllable in their torque output, a design that gripped more tenaciously would allow for a longer tool life and less chance of damaging the fastener. So, the Torx (or officially the “hexalobular internal”) standard was born. It’s six-point, nearly straight head offered a much greater surface area, and thus grip, for users. Just witness how the construction industry has embraced the Torx standard for construction screws.
Not content with the design of the Torx system (or anticipating the eventual expiration of the Torx patent), the Torx Plus design was introduced in 1990, and while the two can look very similar, there are some subtle differences. Instead of a more pointed shape to ends of the “star”, the Torx Plus has more gently rounded lobes and vertical sides. The result is a greater engagement area between the bit and the fastener head. This means in practice that higher torque loads can be applied without cam-out, and results in an increase in the life of the drivers and fasteners. As many of us don’t often encounter Torx Plus very often, you might take comfort in knowing that standard Torx drivers and bits can be used on Torx Plus fasteners (though they might slip at very high torque ratings). Torx Plus tools on the other hand, cannot be used on standard Torx fasteners. One handy variation as well (looking at you, bicycle mechanics) is the ball-end torx driver, which is perfect for those who need to access torx fasteners from an angle.
A quick note on nomenclature and sizing. Both Torx and Torx Plus come in sizes from 1 to 100, and are typically labelled as T1, T2, etc. for Torx and IP1, IP2, etc. (“Internal Plus”) for Torx Plus.
Variations
Increasingly common, especially in the automotive sector, is External Torx and External Torx Plus. Think of it like you would hex: there are internal hex L-keys, drivers and bits, and there are external hex sockets and wrenches. The same holds true with Torx, but not being metric or standard, there is only one set. Instead of the “T” or “IP” prefix, external Torx uses the prefix “E” and Torx Plus “EP”. Sizes range from 2 - 24, but are not comparable to internal sizes, e.g. an E4 Torx socket fits a T20 head.
After the introduction of Torx, manufacturers realized that using Torx fasteners could offer a bit of security from folks trying to disassemble their products, because Torx drivers were still relatively rare. As Torx drivers started to be generally available, however, manufacturers who wanted to continue having that security feature adopted a new variation of Torx: Security Torx. Sizing is exactly the same as a regular Torx fastener; however, a small cylindrical pin sits in the center of the star on the fastener, making it impossible for a regular Torx driver to function. To get around this, a security Torx driver has a small hole bored out of the center, allowing that pin on the fastener to slip right in. Of course, there is also a security Torx Plus standard, with the same post and hole feature.
One more variation that is worth noting, is a five-lobed, or Pentalobe standard. First appearing widely on Apple products, these were the bane of hackers’ existence, until third-party manufacturers began offering drivers for these products. Usually produced in a Torx Plus profile, they are also available in a security or tamper-resistant version with a hole in the tip.
New standards continue to be introduced as well: the latest one to crop up is external Torx Plus Pentalobe. Adopted by many in the world of automated/robotic production, these types of fasteners have begun to crop up on cars and machines. And while none of KC Tool’s current vendors offer these yet, stay tuned, as they are certain to be available soon.
A last word on nomenclature, as many sizes, especially in the smaller range, are nearly indistinguishable, one often has to rely on the markings of the driver or bit to get a good idea of what size is in use. There are official naming conventions, but for some types, individual companies may use their own abbreviations.
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