While most people are familiar with slotted and Phillips screwdrivers, the TORX® screwdriver is not that well know because it is used mainly to assemble highly engineered products such as consumer electronics, computer components and cell phones. It is usually not needed around the house unless of course you work on these type of devices. Since the TORX® screw was designed for automated assembly it now showing up in many places including automobiles. It is even becoming popular in the construction industries.
The TORX® (rhymes with “forks”) fastening system was developed by Acument Global Technologies’ Camcar LLC group (formerly Camcar Textron) and is the trademark for a type of screw head characterized by a 6-point star-shaped pattern. People are often not aware of the trademark ‘TORX’ (which is always capitalized) and often refer to such a driver as a star screwdriver.
The generic name is hexalobular (hex-lob) internal driving feature and is known as ISO 10664 by the International Organization for Standardization.
One of the primary advantages of a TORX® fastener is the elimination of cam out. Cam out is when the screwdriver slips out of the screw head once a certain torque is exceeded.
In the earlier days of manufacturing, the Phillips screwdriver replaced the slotted driver. It was self centering which allowed for automated assembly. The Phillips head screw and screwdriver system was designed to cam out to prevent over-tightening. This was before torque-sensing automatic screwdrivers existed. These properties were used to speed up production although camming out damages the screw and also the screwdriver.
As torque-limiting automatic screwdrivers became available, the TORX® system was invented. By design, TORX® head screws do not cam out. When the desired torque is reached the driver stops applying torque. This pretty much prevents damage to the driver tip, screw head and workpiece. It also allows for the torque to be consistently applied.
The TORX® system is known as ‘Torx T’ and has the following features:
• Straight sidewalls prevent cam out
• Allows high torque transmission
• Circular geometry increases drive bit engagement
• Drivers last ten tines longer than Phillips
• 15° drive angle prevents full engagement of the drive bit and fastener
• 15° drive angle permits a small amount of radial stress which reduces driver bit life