Torx is a type of screw head characterized by a 6-point star-shaped pattern. The official generic name, standardized by the International Organization for Standardization as ISO 10664, is hexalobular internal. Torx screws are commonly found on automobiles, motorcycles, bicycle brake systems (disc brakes), hard disk drives, computer systems and consumer electronics. Initially, they were sometimes used in applications requiring tamper resistance, since the drive systems and screwdrivers were not widely available; as drivers became more common, tamper-resistant variants, as described below, were developed. Torx screws are also becoming increasingly popular in construction industries.
By design, Torx head screws resist cam-out better than Phillips head or slot head screws. Whereas the tendency of Phillips drivers to cam out under excessive torque has been listed as a feature preventing damage to the screw-head or driver, Torx heads were designed to prevent cam-out. The development of better torque-limiting automatic screwdrivers for use in factories allowed this change. Rather than rely on the tool to slip out of the screw head when a desired torque level is reached (which risks damage to the driver tip, screw head, and/or workpiece), torque-limiting driver designs achieve a desired torque consistently.
