Lee Valley Tools Woodworking Newsletter
Vol. 1, Issue 5
July 2007
Featured Patents

Robertson Screwdriver

It has been well documented how Canadian entrepreneur Peter Lymburner (P.L.) Robertson changed the fastening world with his invention of the socket head (Robertson) screw in 1907. Similar to the manner in which the history surrounding the Avro Arrow is firmly ensconced into modern Canadian folklore, so is that of Robertson and his numerous business endeavors. The actual patent (#975,285) for the socket head screw was granted on November 8, 1910. Today this type of driving head accounts for over 75% of all screws sold in Canada. The same type of screw is sold in the United States, where it is called a square drive.

Despite previous escapades with various prospective business partners, Robertson maintained staunch control of his product until his death in 1951. The screwdriver pictured here could be considered an example of putting the cart before the horse, for various reasons. On July 2, 1928, Robertson filed a patent request for his invention that he called a "tool holder", which allowed for the use of an adjustable chuck into which one could insert small tool bits (primarily screwdriver bits and other like-sized items). The key claims on this patent filing were the square cross section of the purpose-built bits and the magazine for loading them into the tool holder. Robertson did, however, think it through so that other round-type tools could be used. Never a patient man and apparently always thinking of improvements, he filed for a second version of the tool on January 10, 1929, which he called a "screw driver". This tool had a set of unique, reversible blades, which accommodated both the Robertson and slotted screws. (That is the type of screwdriver shown here.) Strangely, both patents were issued on September 22, 1931, with the sequential issue numbers 1,824,623 and 1,824,624.

Robertson Screwdriver   Robertson Screwdriver

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