page_title: Torx
section_title: Variants
hierarchical_section_title: Torx / Variants
caption_attribution_description: Close-up of secure Torx driver
context_page_description: Torx, developed in 1967 by Camcar Textron, is a trademarked type of screw drive characterized by a 6-point star-shaped pattern. A popular generic name for the drive is star, as in star screwdriver or star bits. The official generic name, standardized by the International Organization for Standardization as ISO 10664, is hexalobular internal. This is sometimes abbreviated in databases and catalogs as 6lobe. Torx Plus, Torx Paralobe and Torx ttap are improved head profiles.
  Torx screws are commonly found on automobiles, motorcycles, bicycle brake systems, 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.
context_section_description: 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 Torx socket is used to drive it. The external “E” Torx nominal sizing does not correlate to the “T” size, (e.g. an E40 socket is too large to fit a T40 Torx bit, while an E8 Torx socket will fit a T40 Torx bit).
  Torx Paralobe is a further developed Torx Drive System with 6% longer Flanks which results in a 20% higher applicable torque.
  A Torx successor, Torx Plus, was introduced around 1990 when the original Torx patent was expiring. The lobes are more square to allow for higher torque and to minimize wear. The name is shortened to IP (Internal Plus) with sizes ranging from 1IP to 100IP  (sometimes listed as IP1 to IP100 ) and EP (External Plus) with sizes ranging from 1EP to 42EP as well as smaller sizes ranging from H7EP to H2EP and includes five-lobed tamper-resistant variants. The specifications for these licenses are held by Textron. Standard Torx drivers can be used to drive Torx Plus screws, but not to full torque because of the loose fit. Torx Plus drivers will not fit into standard Torx screws.
  A tamper-resistant version of Torx Plus exists having five lobes rather than six, plus a solid post in the center, and is used for security as the drivers are uncommon. Though Acument (formerly Textron) lists no designation, TS  or IPR  may be seen. The screw may alternatively be a Pentalobe.
  Torx Plus Maxx Stems is a highly specialized variant used on the ends of fastener opposite the bolt-head, and provides higher torque than other drive systems allow. Torxstem is a stud with the Torx Plus Maxx drive on both ends.
   An improved version of Torx called Torx ttap was developed in 2005, which features a second recess to create a "stick-fit" engagement (named Frixion Fit), designed to minimize wobbling (named Stable Drive) without pressing and the need for magnetic bits, a feature that can be important to certain industrial users. Standard Torx drivers can be used to drive Torx ttap screws, but Torx ttap drivers will not fit standard Torx screws.
  AudiTorx is a tamper-proof fastener where a concave and smooth fastener head is topped with a break-away Torx drive that snaps off when the engineered torque is reached, leaving a rivet-like bolt head that can't be easily removed. The main application for these fasteners is in the railroad industry.
caption: Security Torx driver
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