The UN threadform designator was selected as the first two letters of the word UNified. The Unified threadform was developed jointly by the governments of Canada, Great Britain, and the U S A to be an INTERNATIONAL standard that would overcome the logistical problems encountered during World War II created by the non-interchangeability of the U S and British standard threadforms.
Interestingly, ten years after the Unified threadform was introduced, its basic geometry of the Unified threadform was adopted by the International Standards Organation (ISO) as the ISO Metric threadform. Naturally, the Diameters and Pitches of the ISO Metric threads are dimensioned in millimeters rather than inches.
Some decades later, the ISO accepted the Unified threadform as an ISO Standard threadform, under the name ISO Inch.
It's true that many textbooks and other supposedly-reliable references say that the anti-acronym of the UN threadform designation is Unified National, but the originators of the threadform were specific that their intent was replace national-standard threadforms with one Unified international threadform.
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Today's Featured Article - New Life for an Old Allis - by Tyler Woods. My friend Jon, has an old '39 Allis Chalmers B. He thought it a marginal tractor that had long since served its time. She smoked terribly and never had much power but he couldn't afford another so he was limping along with what he had. Jon's Allis has a small front loader and though it doesn't carry much, it serves his needs. It was the hard starting and low power that made him think it was time to replace the old girl. Jon called me to help him discover why his tractor wouldn't start
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