The Pros and Cons of Robertson Head Screws
Robertson screws, often referred to as square drive screws, are growing in popularity as a screw head type with many advantages and few disadvantages. Because of issues with licensing, Robertson heads never became popular outside Canada, the homeland of their inventor, a situation that is slowly changing.
As power drivers become more popular, Robertson screws and square drive screws have expanded from their traditional heartland, and mechanics, contractors, and woodworkers across the US are adopting the square drive.
A History of the Robertson Screw
A Canadian inventor, P.L. Robertson, invented the Robertson screw, in 1908, seeing it as a useful alternative to the traditional slot head. He licensed the screw to a company in the UK, but they contrived to steal the invention, and he had to pay a considerable amount of money to buy back the rights to his own design. Because of this, he refused to grant any more licenses, even when Henry Ford asked for permission to use the screw on his production lines.
Ford opted for the Phillips screw, instead, and the Robertson head was confined to Canada, despite its superiority over the Phillips. The Europeans opted for the Pozidriv, and hex recess screws became another alternative to the square drive, sharing many of the advantages associated with the type, but they are not as efficient and simple as the Robertson.
The terms ‘Square Drive’ and ‘Robertson screw’ are often used interchangeably, but they are not exactly the same. The base of the Robertson head recess has a taper rather than a flat base, improving the self-centering [properties of the screw.
Apparently, Robertson invented these screws after badly cutting his hand when his screwdriver slipped out of the edge of a slotted screw. He created the square drive, and it proved to be an excellent screw for a range of applications, from woodwork to aviation. The story of these useful screws claims that Robertson invented them after injuring his hand when a screwdriver slipped out of a slotted head screw. He devised the square design and it proved to be an excellent screw.
- The tapered square recess provides excellent grip, reducing cam out and allowing the user to tighten the screw with one hand
- Robertson screws are self-centering, ensuring that you don’t accidentally drive them at an angle
- The square drive screw has four positions of engagement, a useful trait in tight corners
- The head is designed to cope with high torque without damaging screw head or driver
- With the advent of slipping clutches, overtorquing with power tools is rare
- On production lines, Robertson screws are far more efficient than Phillips heads, speeding production and avoiding damage from cam out
Disadvantages of the Robertson Screw
- They are still difficult to source in may parts of the world, although the growth of the online marketplace is largely negating this problem
- There is no leeway with drivers – you need exactly the right size to engage the screw
Due to the restrictions with availability, recessed hex screws became popular in many parts of the world, and the Torx screw has proved itself capable of matching the Robertson drive for most applications. Hex screws are designed to fit standard Allen keys, but they lack the self-centering property of the genuine Robertson and they are more prone to damage and can out. Nevertheless, they are a decent alternative.
Robertson Driver Sizes
There are five different sizes of Robertson screwdriver, fitting different sized recesses. Colored handles are used to distinguish between the various sizes.
- Orange Handle (00): Fits screw sizes #1 and #2
- Yellow Handle (0): Fits screw sizes #3 and #4
- Green Handle (1): Fits screw sizes #5, #6, and #7
- Red Handle (2): Fits screw sizes #8 and #10
- Black Handle (3): Fits screw sizes #12 and larger
Buy Robertson Screws Online
Robertson screws have always been tricky to find outside Canada, but an increasing number of online retailers are offering screws and drivers as a great alternative to the Phillips. Shopping online also allows you to take advantage of the wide range of shapes, sizes, and styles, as well as benefit from discounts for bulk purposes. Almost a century after their invention, Robertson screws and square drive screws are finally receiving the respect they deserve.
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