The second decade of the 20th century was a fertile period of scientific discoveries, technological advances, and inventions of a vast array of products that we still use today. In 1911, GM engineers invented the first automobile electrical ignition system. 1913 brought the invention of the bra by Mary Phelps Jacob and the crossword puzzle by Arthur Wynne. Stainless steel was invented by Henry Brearly in 1916. The first modern zipper was patented by Gideon Sundback in 1917, and 1919 saw the inventions of the shortwave radio, pop-up toaster, and arc welder.
Along with these mainstream innovations, other more specialized but equally important inventions were being made. In 1919, Hugh Rockwell and Stanley Rockwell, who interestingly enough were not related, patented the original design of the Rockwell hardness tester. Both had been employed by the New Departure Manufacturing Company in Bristol, Connecticut. Up until the early 1900’s, the company was knownfor manufacturing all kinds of bells, starting from their original clockwork-spring mechanism doorbells and expanding from there. The company was so well known for its original specialty, its products provided Bristol with one of its iconic nicknames-the “Bell City”-which lives to this day.
As the company branched out, they built the first patented coaster brake for bicycles, and by 1908 company founder Albert Rockwell had invented the double row ball bearing,which became an integral part of the fledgling automotive building industry. New Departure became the leading bearings manufacturer in the country.
The Rockwell hardness tester was created out of the need for a machine that could quickly and easily measure the effects of heat treatment on the ball bearing track. The new method expanded upon the established indention hardness test by using a conical diamond for the indention media, and basing the test results on displacement. Rockwell hardness testers provided two main advantages. A much smaller area of indentation was needed for the measurement, and the test could now be performed on curved as well as flat surfaces.
Rockwell hardness testers remainto this day the preferred method of hardness testing, and are recognized as one of the 20th century’s great metallurgical advances.
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