Torx
From Wikipedia, the free encyclopedia
| Part of the series on | |
|---|---|
| Screw draw types | |
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Slotted |
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Phillips |
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Pozidriv |
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Torx |
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Hex |
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Robertson |
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Tri-Wing |
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Torq-Set |
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Spanner Head |
TORX, developed by Textron Fastening Systems (formerly Camcar Textron), is the trademark for a type of screw head 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 Standardization as ISO 10664.
By design, TORX head screws resist cam-out better than Phillips head or slot head 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 consistently achieve a desired torque. Textron claims this can increase tool bit life by ten times or more.
TORX screws are commonly found on automobiles, computer systems (T15 screws are used almost exclusively on Compaq systems) and consumer electronics, but are also becoming increasingly popular in construction. Do-it-yourself mechanics will often 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, rather than carrying several different sizes of TORX screwdrivers or bits.
[edit] Sizing
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 T5, T10, T15 and T25, although they reach as high as T100. Only the proper driver can drive a specific head size without risking the ruin of 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.
[edit] Variants
- A version known as Security TORX or Tamper Resistant TORX (often shortened by Torx TR) contains a post in the center of the head that prevents a standard TORX driver from being inserted. Additionally, while a standard TORX screw may if necessary be used with a slotted screwdriver of appropriate size, this is not possible with a Security TORX.
- 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. 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.
