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The Battle: 60o Defeats 55o

Life is filled with so many things I have never thought about. For example, the need for standardization of tools, electronics, labeling, etc. When did it begin? Who is responsible? This becomes important knowing that there currently are almost one million global standards.

It turns out that the world's efforts for standardization are traced back to the difference between angles of 55o and 60o. And, the person responsible was William Sellers...on April 21, 1864.

Sellers was a tool builder, and had just been elected to head the Franklin Institute in Philadelphia, a professional society for engineers and machinists. His induction speech was "On a Uniform System of Screw Threads."

At that time, each machine shop custom-made their own screws, bolts, and nuts...so there was little expectation of things "fitting" from different shops. In short, it was a mess.

Sellers recognized this problem, and he realized that the key design feature in a screw was the shape of the threads running along its shaft. Also, the threads impacted the strength and durability of a screw.

The cross-section of a screw thread is triangular, and tended to approximate one of two angles: the Whitworth thread was 55o and rounded at the top, while the Sellers thread was 60o amd flattened at the top. Sounds trivial, right?

In practical use and construction, the Whitworth tread was difficult to measure precisely and required special gauges for its construction (plus three kinds of cutters and two lathes). In contrast, the Sellers thread was easy to measure, being the angle of any equilateral triangle, and could be constructed easily (needing one cutter and one lathe).

Arguing the need for standardization (especially for his thread design), Sellers' speech won over the crowd...the enthusiasm spread...and his call was implemented in the U.S. by 1900 and adopted as a standard by Europe in 1901.

So began the effort towards standardization...all due to a fight over the difference of 55o and 60o. Hope you find this interesting as well.

Source: J. Surowiecki's "Turn of the Century," WIRED, January 2002, pp. 84-89