Robertson vs. Security Torx
Comparing 2 standards across 10 specifications. 10 key differences identified.
The Robertson drive (Square socket / SCRULOX, standardized under ANSI Type III / CSA B35.4) is a 4-sided tapered square recess drive invented in Canada by P.L. Robertson, patented in 1906-07, with a 1908 manufacturing refinement (cold-forming the socket) that made it commercially viable. Known for its distinct tapered geometry that locks the screw onto the driver bit for one-handed operation, it is the dominant construction and electrical fastener across Canada.
Security Torx (Tamper-Resistant Torx / Pin-in-Torx / Torx TR) is a tamper-evident variant of the standard hexalobular drive. Featuring a hardened solid cylindrical metal post in the center of the 6-lobed recess, it prevents standard flat, hex, or standard Torx driver bits from inserting, requiring a specialized hollow-tipped security bit.
Specification Comparison Table
10 Parameters| Parameter / Spec | ||
|---|---|---|
|
Drive Geometry
|
4-sided square recess with a slight interior conical taper (approx. 3° taper) | Standard 6-lobed Torx star with a centered solid cylindrical metal post |
|
Standard Specifications
|
CSA B35.4 / ANSI Type III Square Recess / ASME B18.6.3 | — |
|
Self-Holding 'Stick-Fit'
|
Yes (Taper friction-locks screw onto driver bit for horizontal/overhead 1-handed driving) | — |
|
Cam-Out Tendency
|
Near Zero (Straight square drive walls resist climbing) | — |
|
Color-Coded Sizing System
|
#00 Orange, #0 Yellow, #1 Green, #2 Red (dominant wood/deck size), #3 Black, #4 Brown | — |
|
Primary Geographic Usage
|
Universal in Canada (electrical/framing/decking) / Pocket-hole woodworking globally (Kreg) | — |
|
Tool Bit Requirement
|
— | Hollow-center / Bore-hole driver bit (e.g. TR20 bit has a drilled center) |
|
Standard Sizing Tiers
|
— | T6H, T7H, T8H, T9H, T10H, T15H, T20H, T25H, T27H, T30H, T40H ('H' or 'TR' designation) |
|
Tamper Resistance Level
|
— | Medium (Deters unauthorized consumer disassembly without specialty tools) |
|
Primary Applications
|
— | Public infrastructure (restroom partitions, subway signs), video game consoles (Xbox, PlayStation controllers), consumer power tools |