The Robertson screwdriver uses a square-tapered recess that self-centres on the screw, resists cam-out, and can be driven one-handed. Invented by P.L. Robertson in Milton, Ontario in 1908, it is the dominant screw drive in Canadian construction - and virtually unknown elsewhere.
Why Robertson Didn't Go Global
P.L. Robertson refused to license his design. When Henry Ford wanted to use Robertson screws on the Model A assembly line in the late 1920s, Robertson insisted on manufacturing the screws himself rather than granting Ford a license. Ford walked away and later adopted the Phillips drive instead. That single decision shaped global screw standards for the next century.
Robertson Sizes and Color Codes
| Size | Color Code | Recess Width | Screw Gauge Range | Typical Use |
|---|---|---|---|---|
| #0 | Orange | 1.77 mm | #2–#4 | Small electronics, instrument screws |
| #1 | Yellow | 2.29 mm | #5–#7 | Light hardware, electrical boxes |
| #2 | Green | 2.87 mm | #8–#10 | General construction - the most common size |
| #3 | Red | 3.43 mm | #12–#14 | Heavy construction, decking, subfloor |
| #4 | Black | 4.04 mm | #16+ | Industrial, lag bolts, heavy timber |
Green (#2) Robertson handles about 80% of construction screws in Canada - the same dominance PH2 has in Phillips. If you buy one size, make it green.
Why Tradespeople Prefer Robertson
- Self-centering - the tapered square seats in the screw and holds without a magnet
- No cam-out - the square recess transfers torque directly with no tendency to slip
- One-handed driving - the screw stays on the driver tip, freeing the other hand
- Faster than Phillips - no need to press hard to prevent cam-out
- Works well with power tools - positive engagement means fewer stripped screws
In Canada, Robertson is the default for wood screws, decking, drywall (sometimes), and most construction. The square combo drive - a screw head that accepts both Robertson and Phillips - has helped Robertson gain some traction in the US market.
