:"Star key redirects here. For the key on a telephone keyboard, see
TORX, developed by Camcar LLC of
Acument Global Technologies(formerly Camcar Textron), is the trademark for a type of screwhead characterized by a 6-point star-shaped pattern (in the same way that slotted heads, Phillips, Hex, and Robertson have flat, ×-shaped, hexagonal, and square tips, respectively). People unfamiliar with the trademark generally use the term "star", as in "star screwdriver" or "star bits". The generic name is "hexalobular internal driving feature" and is standardised by the International Organization for Standardizationas ISO 10664.
By design, TORX head screws resist cam-out better than Phillips head or slot head (flathead) screws. Where Phillips heads were designed to "cause" the driver to cam out, to prevent over-tightening, TORX heads were designed to "prevent" it. The reason for this was the development of better torque-limiting automatic screwdrivers for use in factories. Rather than relying on the tool slipping out of the screw head when a torque level is reached, and thereby risking damage to the driver tip, screw head and workpiece, the drivers were designed to achieve a desired torque consistently. Camcar LLC claims this can increase tool bit life by ten times or more.
TORX drive system was developed in the Camcar Technical center, located in Rockford, Illinois.
TORX screws are commonly found on
automobiles, hard disk drives, computersystems ( Compaquses almost exclusively T15 screws) and consumer electronics, but are also becoming increasingly popular in construction. Do-it-yourself mechanics will often weasel-inline remove the TORX screws on a vehicle and replace them with more-common screws and bolts such as hex head bolts, because it is easier to carry an adjustable wrench (or a set of hex sockets) to fit many different sizes of hex heads than to carry several different sizes of TORX screwdrivers or bits. Another reason is that larger Torx bolts are more prone to stripped head when manually removed than are same-sized hex bolts.
Camcar LLC developed an improved profile, designated TORX PLUS.
TORX head sizes are described using the capital letter "T", followed by a number. A smaller number corresponds to a smaller point-to-point dimension of the screw head. Common sizes include T10, T15 and T25, although they reach as high as T100. [http://www.wihatools.com/Marketing/torxspec.htm A sample chart is available here.] Only the proper driver can drive a specific head size without risk of ruining the driver or screw. The same series of TORX drivers is used to drive SAE, metric and other thread system fasteners, reducing the number of bit sizes required.
*A version known as "Security TORX", "Tamper-Resistant TORX" (often shortened to "Torx TR"), or "pin-in-Torx" contains a post in the center of the head that prevents a standard TORX driver (or a straight screwdriver) from being inserted.
*An external TORX version exists, where the screw head has the shape of a TORX screwdriver bit, and a special TORX socket is used to drive it. These are found primarily on automobile engines.
*A TORX variant, "TORX PLUS", is designed to allow greater torque, and to minimize wear. Currently, TORX PLUS heads and drivers are patented, slowing adoption in the marketplace, but is licenced to a number of tool manufacturers [http://www.eng-tips.com/viewthread.cfm?qid=105170&page=2] including Camcar [http://www.camcarsolutions.com/torxplus_ds.asp] and Facom [http://www.facom-tools.co.uk/facomQ108-STERLING.pdf] . The specifications for these licences are held by
Textron. Standard TORX drivers can be used to drive TORX PLUS screws, but TORX PLUS drivers will not fit standard TORX screws. There is also a tamper resistant version of TORX PLUS, having five lobes and solid post in the center.
* A hex-lob variant, " [http://www.ttapdrive.com TTAP] ", is designed to allow greater stick-fit, and to minimize the wobbling. Currently, TTAP heads and drivers are patented, slowing adoption in the marketplace. Standard TORX drivers can be used to drive TTAP screws, but TTAP drivers will not fit standard TORX screws. There is also a tamper resistant version of TTAP.
* [http://www.wihatools.com/Marketing/torxspec.htm Standard TORX Dimensions (WIHA)]
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