Torx is trademarked for a type of screw head characterised by a six-point star-shape pattern. It was developed by Camcar Textron to resist cam-out. Cam-out occurs when a screw is over-tightened. The reason for the need of a better cam-out-resistant tool was the development of better torque-limiting screwdrivers used in factories. The cam-out-resistant tools enhance tool life. Torx screws are found in vehicles and consumer electronics.
Torx specification sizing is designated by a capital "T" followed by a number. The size refers to the diameter of the Torx screw it will fit. The smaller the number, the smaller the point dimension. Common Torx sizes include T10, T15 and T25. The Torx threads are designated in English and metric units. The dual designation reduces the number of screwdrivers and socket wrenches necessary. The external variant of Torx head size is designated using a capital "E" followed by a number. Like the "T" series, the smaller the number, the smaller the point dimension.
Security Torx screws contains a pin in the middle of the screw head that prevents a standard Torx driver or a straight or Phillips screwdriver from being inserted and removing the screw. The external Torx is a screw head that has the shape of the standard Torx, but a special Torx socket wrench is required to insert it. Automobile manufactures use the external Torx screw for most applications. The Torx Plus was designed to allow greater torque and minimise wear. The Torx plus is a patented tool but is licensed to several tool manufacturers. Torx drivers can be used to fit standard Torx screws but do not fit snug enough to allow full torque. There is a vandal-resistant version of Torx Plus that has five points rather than six and a solid pin in the centre. Drivers for this type of Torx are difficult to obtain.
There are a number of Torx drivers available, including straight handle, T Handle, offset, short-arm L-shape, long-arm L-shape and ball end. The drivers come in 4-, 6-, 8- and 10-inch blades. There are also a variety of handle types for the drivers. They include the soft grip, standard grip, magic spring grip, nonslip and nonslip premium and insulated for electrical work. Torx also comes in bit style for use with a power drill or socket wrench applications. Lengths vary from 2 to 6 inches to accommodate different applications. The sizes are designated in English and metric sizing to eliminate the need for multiple socket wrench or drill sets.