Torx (Hexalobular Internal)
Direct Answer
Torx (standardized as Hexalobular Internal under ISO 10664) is a 6-lobed star-shaped screw drive system developed by Camcar Textron in 1967. Engineered with a low 15-degree drive angle and curved lobes, it eliminates cam-out entirely, delivers exceptional torque transfer, and drastically extends tool bit lifespan across automotive, computing, and construction hardware.
Source: ISO 10664 / ASME B18.6.3 / Camcar Textron Specification
Specs
| International Standard | ISO 10664 (Hexalobular internal driving feature for bolts and screws) |
| Drive Geometry | 6-pointed star with rounded circular lobes |
| Drive Angle | 15 degrees (near-perpendicular torque vector) |
| Cam-Out Tendency | Zero (Radial drive force completely eliminates axial climb) |
| Common Sizing Tiers | T1–T5 (smartphones), T6–T10 (laptops/electronics), T15–T25 (wood/auto), T30–T50 (chassis/structural) |
| External Variant | E-Torx (Inverted star socket for high-torque automotive bolts, E4 to E24) |
Mechanical Torque Vector Physics
In cross-recess and hex drives, the driving force pushes outward against the fastener walls at steep angles (up to 60°), generating severe stress concentrations that round off the corners. Torx uses 6 circular lobes where the drive angle is only 15°. This directs almost 100% of the rotational force purely tangentially, enabling automated assembly robots to drive high-torque structural fasteners at thousands of RPM without bit slippage.
Consumer Electronics and Automotive Adoption
Torx is the primary fastener across Apple, Dell, and HP laptops (T5/T6), smartphone internals (T2/T3), European automobile engines (BMW, Mercedes, VW), and modern structural construction timber screws (T25/T30).