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.