Screw standards
James Surowiecki has written a history lesson about technological standardisation for Wired. He claims that standards have had large economic and technological effects. OK, I agree. But he gives too much credit to just one man, William Sellers, who he calls a legend and the finest tool builder of his time.
!['[Whitworth] Taper Tap', figure 623 in Paul N Hasluck (editor), 'Metalworking: a book of tools, materials and processes...' (London: Cassell & Co, 1904) Screw tap](images/tap.gif)
Surowiecki makes out that Sellers’s proposal for a new screw thread standard was a revolutionary advance on the established Whitworth design, but I am not convinced. And was the introduction of yet more incompatible standards such a triumph? Still, I enjoyed reading this ripping yarn — here’s a quote from the introduction:
William Sellers knew that the end of the hand-tooled machine age was nigh. So he grabbed the manufacturing elite by the nuts and bolts and dragged them into the mass production era. A case study in the power of standards…
I'm a student in mechanical engineering.
It is an interisting story but some what incomplete. The full set of rules for Sellers thread is printed in "The Steam Engine" by W. Marks 1884 second edition.
The finished bolt and nut sizes are not the sizes used today. For example a 9/16" dia. bolt the finish head size is 29/32" and the rough head size is listed as 31/32"
I checked this out in a 1895 machinery cataloge and the wrench size for a 9/16" bolt is listed as 31/32" across the flats.