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What is a Torx Screw?


We are all familiar with traditional slot-head screws, which require a flat-bladed screwdriver, and cross-head screws, which might be Phillips or Pozidriv. But there are many additional, specialised screw-types including Torx screws.

What is a Torx Screw?

Torx is the trademark for a type of screw head, developed by Camcar Textron in 1967. It’s characterised by a distinct, 6-point star-shaped pattern and is often called a ‘star screw’ that requires a ‘star screwdriver’ with a ‘star bit’ to tighten and untighten them. 

Torx screws are typically used in vehicles, motorcycles, bicycles, computer systems, hard disk drives and consumer electronics. The unusual star-shaped head makes them far more secure than regular flat-head or cross-head screws and allows higher torque transmission so screws and bolts can be tightened more securely.

Torx Screwdrivers

Torx screwdrivers have distinctive 6-point star shaped head which mate perfectly with appropriately sized screw heads. The unique Torx design means that there is less likelihood that the screw head will be stripped or the screwdriver damaged. Torx screwdrivers can last up to ten times longer than regular screwdrivers due to the resilience of the design.


torx tools
Torx Tools

The important thing to remember regarding Torx screwdrivers is that the screwdriver size must match the size of the Torx screws. So if you are working with T15 Torx screws then you need a T15 Torx screwdriver. Torx screwdriver sets are available in various sizes.

Security Torx

Security Torx screws are often called Pin Torx due to the additional pin at the centre of the six-point star socket head. This centre pin makes it impossible to use a standard Torx screwdriver, making this type of fastening tamper-proof.

torx machine screws
Standard and Security Torx Heads

Security Torx screws are sometimes called: 6 lobe screws, tamper proof torx, 6 lobe pin torx, torx TR, torx pin and star pin drive screws. Tamper-proof security Torx screws provide a higher level of security than standard Torx due to the specialised security Torx screwdriver that’s needed to loosen them.

Security Torx Screwdrivers

As noted, standard 6 point Torx screwdrivers will not mate with security torx screws due to the additional centre pin in the socket head. To use security Torx screws requires appropriate tools which accommodate the additional security pin.

torx screwdrivers standard and security
Torx Screwdrivers - Standard and Security

5 Point Torx Plus

A successor to the original Torx design was Torx Plus, introduced in 1990. This design made improvements on the original which enabled higher torque to be applied while minimising wear. 

A further development has been the introduction of the tamper resistant variant of Torx Plus sometimes called Torx Plus Security or Torx Plus TR (tamper resistant). This form uses a 5 point star shaped head socket with a centre pin. 

Torx Plus five point head socket with centre pin

This five-point or five-lobed socket design is generally called a pentalobular socket. The revised design adds a further level of security and requires the use of appropriate tools that mate with the 5-point star socket and central security pin.

Torx Screw Sizes

As noted, it’s important to match the size of the Torx screw or bolt socket head with the correct size of Torx screwdriver. Here’s a chart showing the standard Torx sizes.

Torx Size Imperial Point to Point (inches) Metric Point to Point Max Torque Range
T1 .031" .81mm .02 to .03 Nm
T2 .036" .93mm .07 to .09 Nm
T3 .046" 1.10mm .14 to .18 Nm
T4 .050" 1.28mm .22 to .28 Nm
T5 .055" 1.42 mm .43 to .51 Nm
T6 .066" 1.70 mm .75 to .9 Nm
T7 .078" 1.99 mm 1.4 to 1.7 Nm
T8 .090" 2.31 mm 2.2 to 2.6 Nm
T9 .098" 2.50 mm 2.8 to 3.4 Nm
T10 .107" 2.74 mm 3.7 to 4.5 Nm
T15 .128" 3.27 mm 6.4 to 7.7 Nm
T20 .151" 3.86 mm 10.5 to 12.7 Nm
T25 .173" 4.43 mm 15.9 to 19 Nm
T27 .195" 4.99 mm 22.5 to 26.9 Nm
T30 .216" 5.52 mm 31.1 to 37.4 Nm
T40 .260" 6.65 mm 54.1 to 65.1 Nm
T45 .306" 7.82 mm 86 to 103.2 Nm
T50 .346" 8.83 mm 132 to 158 Nm
T55 .440" 11.22 mm 218 to 256 Nm
T60 .519 13.25 mm 379 to 445 Nm
T70 .610 15.51 mm 630 t0 700 Nm
T80 .690 17.54 mm 943 to 1048 Nm
T90 .784 19.92 mm 1334 to 1483 Nm
T100 .871 22.13 mm 1843 to 2048 Nm

Torx Sizes Chart

Here at Insight-Security.com we are experts in all aspects of security fastenings, screws and bolts. Contact us on 01273 475500 to discuss your requirements.

This message was added on Thursday 1st August 2019

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