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Torx
Torx
(pronounced /tɔːrks/), developed in 1967[1] by Camcar Textron,[2] is the trademark for a type of screw head 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
International Organization for Standardization
as ISO 10664, is hexalobular internal.[3] This is sometimes abbreviated in databases and catalogs as 6lobe (starting with numeral, 6, not a capital letter, G). Torx
Torx
Plus is an improved head profile. Torx
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.[4] Torx screws are also becoming increasingly popular in construction industries.

Contents

1 Principles of operation 2 Sizing 3 Variants 4 Competitive variants 5 Gallery 6 See also 7 References 8 External links

Principles of operation[edit]

The angle between the plane of contact between tool and fastener and the circumferentially directed force is much closer to 90º in a Torx type of head (lower) than in a conventional hex head (upper).

By design, Torx
Torx
head screws resist cam-out better than Phillips head or slot head screws.[1] Whereas Phillips heads were allegedly designed to cause the driver to cam out, to prevent overtightening, Torx
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. The Torx
Torx
design allows for a higher torque to be exerted than a similarly sized conventional hex socket head without damaging the head and/or the tool.[1] The diagram on the right depicts the interaction between the male and female components of a conventional hex drive and a Torx
Torx
drive. The clearance between the components is exaggerated for clarity. The green circle, passing through the six points of contact between the two components, represents the direction of the rotational force being exerted at each of those points. Because the plane of contact is not perpendicular to this circle, a radial force is also generated which tends to "burst" the female component and "crush" the male one. If this radial force component is too great for the material to withstand, it will cause the corners to be rounded off one or both components or will split the sides of the female part. The magnitude of this force is proportional to the cotangent of the angle (depicted in orange) between the green circle and the contact plane. For the Torx
Torx
type of design, the angle is much closer to 90º than in the case of the hex head, and so for a given torque the potentially damaging radial force is much lower. This property allows the head of the fastener to be smaller for the same required torque, which can be an advantage in applications where space to accommodate the head is limited. The disadvantage on older Torx
Torx
heads is that the smaller internal "splines" can corrode relatively easily and cause the Torx
Torx
driver to slip and damage the head, making it more difficult to remove than the traditional hexagon head. Sizing[edit]

Part of a series on

Screw
Screw
drive types

Slotted

 Slot drive  Cross

Cruciform

 Phillips PH  Frearson  French recess  JIS B 1012  Mortorq  Pozidriv PZ  Supadriv PZ  Torq-set  Phillips/​Slotted

Internal polygon

 Square  Robertson  Hex  12-point  Hex socket (Allen)  Security hex  Double-square  Triple-square XZN  12-spline flange  Double hex

Hexalobular

 Torx T & TX  Security Torx TR   Torx
Torx
Plus TR  Polydrive  External Torx  Line head male  Line head female  Line head female tamper

Three-pointed

 TA  Tri-point  Tri-groove  Tri-wing

Special

 Clutch A  Clutch G  One-way  Bristol  Quadrex  Pentalobe  Spanner head (pig nose) TH

v t e

Torx
Torx
head sizes are described using the capital letter "T" followed by a number ranging from T1 to T100.[5] A smaller number corresponds to a smaller point-to-point dimension of the screw head (diameter of circle circumscribed on the cross-section of the tip of the screw driver). Common sizes include T10, T15, and T25, while T5.5, T35, and T47 tend to see specialized use. Only the proper driver can drive a specific head size without risk of damaging the driver or screw. The same series of Torx
Torx
drivers is used to drive SAE, metric and other thread system fasteners, reducing the number of bit sizes required. The "external" variants of Torx
Torx
head sizes (see below) are described using the capital letter "E" followed by a number ranging from E4 to E44.[6] The "E" numbers are different from the "T" numbers of the same size: for example, an E4 Torx
Torx
socket fits a T20 head.[5]

Properties of various Torx
Torx
drives[5]

Size Point-to-point distance Maximum torque range ~ E Torx

(in) (mm) (lb·ft) (N·m)

T1 0.031 0.81 0.01–0.02 0.02–0.03

T2 0.036 0.93 0.05–0.07 0.07–0.09

T3 0.046 1.10 0.10–0.13 0.14–0.18

T4 0.050 1.28 0.16–0.21 0.22–0.28

T5 0.055 1.42 0.32–0.38 0.43–0.51 E2

T5.5[7]

T6 0.066 1.70 0.55–0.66 0.75–0.90

T7 0.078 1.99 1.0–1.3 1.4–1.7

T8 0.090 2.31 1.6–1.9 2.2–2.6

T9 0.098 2.50 2.1–2.5 2.8–3.4

T10 0.107 2.74 2.7–3.3 3.7–4.5

T15 0.128 3.27 4.7–5.7 6.4–7.7

T20 0.151 3.86 7.74–9.37 10.5–12.7 E4

T25 0.173 4.43 11.7–14.0 15.9–19 E5

T27 0.195 4.99 16.6–19.8 22.5–26.9

T30 0.216 5.52 22.9–27.6 31.1–37.4 E6

T35[8]

E7

T40 0.260 6.65 39.9–48.0 54.1–65.1 E8

T45 0.306 7.82 63.4–76.1 86–103.2

T47[9][10] GM-Style

T50 0.346 8.83 97.4–117 132–158 E10

T55 0.440 11.22 161–189 218–256 E12

T60 0.519 13.25 280–328 379–445 E16

T70 0.610 15.51 465–516 630–700 E18

T80 0.690 17.54 696–773 943–1048 E20

T90 0.784 19.92 984–1094 1334–1483

T100 0.871 22.13 1359–1511 1843–2048 E24

Variants[edit]

Security Torx
Torx
driver

External Torx
Torx
driver

A version known as Security Torx, Tamper-Resistant Torx
Torx
(often shortened to Torx
Torx
TR) or pin-in Torx
Torx
contains a post in the center of the head that prevents a standard Torx
Torx
driver (or a straight screwdriver) from being inserted. An External Torx
Torx
version exists, where the screw head has the shape of a Torx
Torx
screwdriver bit, and a Torx
Torx
socket is used to drive it. The external “E” Torx
Torx
nominal sizing does not correlate to the “T” size, (e.g. an E40 socket is too large to fit an T40 Torx
Torx
bit, while E8 Torx
Torx
socket will fit a T40 Torx
Torx
bit [5]).

Properties of various External Torx
Torx
drives

Size   Point-to-point distance [5]    Standard fastener selection [6] 

(in) (mm) SAE Metric

E4 0.15 3.8 #6 M3

E5 0.18 4.7 #8 M4

E6 0.22 5.6 #10 M5

E7 0.24 6.1

E8 0.29 7.4 1/4" M6 & M7

E10 0.36 9.3 5/16" M8

E12 0.43 11.1 3/8" M10 & M11

E14 0.50 12.8 7/16" M12

E16 0.57 14.7 1/2"

E18 0.65 16.6 9/16" M14

E20 0.72 18.4 5/8" M16

E24 0.87 22.1 3/4" M18 & M20

E28

7/8" M22

E32

1" M24 & M27

E36

1-1/8" M30

E40

1-1/4" M33

E44

1-3/8" M36

A Torx
Torx
successor, Torx
Torx
Plus, was introduced about 1990 when the original Torx
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 [11] (sometimes listed as IP1 to IP100 [12]) 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.[11] The specifications for these licenses are held by Textron. Standard Torx drivers can be used to drive Torx
Torx
Plus screws, but not to full torque because of the loose fit. Torx
Torx
Plus drivers will not fit into standard Torx
Torx
screws.

A tamper-resistant version of Torx
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.[13] Though Acument (formerly Textron) lists no designation,[14][15] TS [16] or IPR [17] may be seen. Torx
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.[18] Torxstem is a stud with the Torx
Torx
Plus Maxx drive on both ends.

A modified version of Torx
Torx
called Torx
Torx
TTAP was developed in 2005,[19] which features a second recess to create a "stick-fit" engagement, designed to minimize wobbling without the need for magnetic bits, a feature that can be important to certain industrial users.[20] Standard Torx
Torx
drivers can be used to drive TTAP screws, but TTAP drivers will not fit standard Torx
Torx
screws.[21] Audi Torx
Torx
is a tamper-proof fastener where a concave and smooth fastener head is topped with a break-away Torx
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.[22]

Competitive variants[edit] AW drive is a similar hexalobular type screw head to Torx, with a tapered profile to aid in centering, developed by the Würth
Würth
Group in Germany.[23] Available in five sizes: AW 10, AW 20, AW 25, AW 30 and AW 40.[24] Gallery[edit]

Torx
Torx
bits T15, T20, T25, and T30

A Torx
Torx
wrench

Closeup of Torx
Torx
screwdriver tip

See also[edit]

Wrench

References[edit]

^ a b c U.S. Patent 3,584,667, Bernard F Reiland, "Coupling arrangement and tools for same", filed 1967-03-21 ^ Camcar eventually became part of Textron
Textron
Fastening Systems in the 1990s. In 2006 Textron
Textron
Fastening Systems was sold to Platinum Equities, LLC, of Beverly Hills, California. They renamed the company Acument Global Technologies, which as of 2010 includes Avdel, Camcar, Ring Screw, and others. In 2014, Acument was sold from Platinum Equity to Fontana Gruppo. ^ ISO 10664:2005, ISO.org, retrieved 2012-01-14  ^ Paul Sharke (June 2005). "Fast and Secure: how much proof is tamperproof?". Mechanical Engineering. 127 (6): 32. ISSN 0025-6501. Archived from the original on 2007-02-09. Retrieved 2012-01-14. CS1 maint: BOT: original-url status unknown (link) ^ a b c d e "Chart of Torx
Torx
fasteners and tools". Wiha Tools USA. Archived from the original on 2015-12-26. Retrieved 2012-01-14.  ^ a b "TORX Drive System" (PDF). Textron
Textron
Fastening Systems. Archived from the original (PDF) on 2007-01-02.  ^ "16pc torx bit set". Amtech Tools. Retrieved 24 February 2017.  ^ "2 Pcs T35 3/13 Torx
Torx
Head Screwdriver
Screwdriver
Link 1/2 Square Mechanic Drive Socket".  ^ "FTX47E, Socket Driver, TORX, GM-Style, T47".  ^ "Fiero Torx
Torx
Sockets".  ^ a b "TORX PLUS Drive System" (PDF). Acument.  ^ "TORX PLUS Long arm L-Keys". Wiha Tools USA. Archived from the original on 7 October 2015. Retrieved 14 July 2016.  ^ Egon Pavlis (16 March 2010). "When a Phillips is not a Phillips Plus So Much More!". Instructables.  ^ "Fastening Solutions" (PDF). Acument.  ^ "Tamper-Resistant TORX PLUS Drive System" (PDF). Textron
Textron
Fastening Systems. Archived from the original (PDF) on 2006-11-10.  ^ "TS Star Bits (5 Sided) 1/4"D 7pc - Part No. 3389 - Part of the TS Star/Torx* Plus range from Laser Tools". Retrieved 14 July 2016.  ^ "Security TORX PLUS Insert Bits". Wiha Tools USA. Archived from the original on 13 December 2015. Retrieved 14 July 2016.  ^ "TORX PLUS® MAXX Drive System".  ^ US patent 6951158, Jone Edland, "System comprising a screw and a tool therefor", issued 2005-10-04  ^ "TTAP Fastener". Acument Global Technologies. Retrieved 26 February 2017.  ^ " Torx
Torx
TTAP Advantages". TTAP Drive AS. Retrieved 26 February 2017.  ^ "Acument Industrial fastening systems".  ^ "Technical Information on Fasteners: Design recommendations 11.1 Inside drives for screws – AW drive (AW-Antrieb)" (PDF). Adolf Würth
Würth
GmbH & Co. KG. Retrieved 2 March 2017.  ^ "Construction Range Overview (Fasteners: Introducing the AW Drive System, p3)" (PDF). Würth
Würth
New Zealand. 2016. 

External links[edit]

Media related to Torx
Torx
at Wikimedia Commons Identifying and naming every Torx
Torx
variation

v t e

ISO standards by standard number

List of ISO standards / ISO romanizations / IEC standards

1–9999

1 2 3 4 5 6 7 9 16 31

-0 -1 -2 -3 -4 -5 -6 -7 -8 -9 -10 -11 -12 -13

128 216 217 226 228 233 259 269 302 306 428 518 519 639

-1 -2 -3 -5 -6

646 690 732 764 843 898 965 1000 1004 1007 1073-1 1413 1538 1745 1989 2014 2015 2022 2047 2108 2145 2146 2240 2281 2709 2711 2788 2848 2852 3029 3103 3166

-1 -2 -3

3297 3307 3602 3864 3901 3977 4031 4157 4217 4909 5218 5428 5775 5776 5800 5964 6166 6344 6346 6385 6425 6429 6438 6523 6709 7001 7002 7098 7185 7200 7498 7736 7810 7811 7812 7813 7816 8000 8178 8217 8571 8583 8601 8632 8652 8691 8807 8820-5 8859

-1 -2 -3 -4 -5 -6 -7 -8 -8-I -9 -10 -11 -12 -13 -14 -15 -16

8879 9000/9001 9075 9126 9293 9241 9362 9407 9506 9529 9564 9594 9660 9897 9899 9945 9984 9985 9995

10000–19999

10005 10006 10007 10116 10118-3 10160 10161 10165 10179 10206 10218 10303

-11 -21 -22 -28 -238

10383 10487 10585 10589 10646 10664 10746 10861 10957 10962 10967 11073 11170 11179 11404 11544 11783 11784 11785 11801 11898 11940 (-2) 11941 11941 (TR) 11992 12006 12182 12207 12234-2 13211

-1 -2

13216 13250 13399 13406-2 13450 13485 13490 13567 13568 13584 13616 14000 14031 14224 14289 14396 14443 14496

-2 -3 -6 -10 -11 -12 -14 -17 -20

14644 14649 14651 14698 14750 14764 14882 14971 15022 15189 15288 15291 15292 15398 15408 15444

-3

15445 15438 15504 15511 15686 15693 15706

-2

15707 15897 15919 15924 15926 15926 WIP 15930 16023 16262 16612-2 16750 16949 (TS) 17024 17025 17100 17203 17369 17442 17799 18000 18004 18014 18245 18629 18916 19005 19011 19092 (-1 -2) 19114 19115 19125 19136 19439 19500 19501 19502 19503 19505 19506 19507 19508 19509 19510 19600 19752 19757 19770 19775-1 19794-5 19831

20000+

20000 20022 20121 20400 21000 21047 21500 21827:2002 22000 23270 23271 23360 24517 24613 24617 24707 25178 25964 26000 26300 26324 27000 series 27000 27001 27002 27006 27729 28000 29110 29148 29199-2 29500 30170 31000 32000 38500 40500 42010 55000 80000

-1 -2

.