Robertson vs. Tri-Wing
Comparing 2 standards across 9 specifications. 9 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.
The Tri-Wing drive (standardized under military spec MIL-P-87893 / NASM 87893) is a tamper-resistant security drive featuring three radial slotted wings surrounding a triangular center point. Originally developed for aerospace structural skins, it was adopted by Nintendo for older cartridge and console hardware -- a distinct drive from the visually different Tri-Point/Y-type screw Apple uses today, despite the two often being confused.
Specification Comparison Table
9 Parameters| Parameter / Spec | ||
|---|---|---|
|
Drive Geometry
|
4-sided square recess with a slight interior conical taper (approx. 3° taper) | 3 radial wings offset from a central triangular hub (120-degree radial spacing) |
|
Cam-Out Tendency
|
Near Zero (Straight square drive walls resist climbing) | Moderate (Requires steady axial alignment to prevent bit climb) |
|
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) | — |
|
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) | — |
|
Original Manufacturer / Spec
|
— | Phillips Screw Company / MIL-P-87893 (US Military Aerospace Specification) |
|
Standard Sizing Tiers
|
— | TRI-000, TRI-00, TRI-0, TRI-1, TRI-2, TRI-3, TRI-4, TRI-5 |
|
Primary Applications
|
— | Aerospace fuselage panels, older Nintendo cartridge/console hardware (original Game Boy, Game Boy Advance) |