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Concept

Unified Thread Standard

A screw with a unified thread design, symbolizing the 1948 agreement between the US, Canada, and UK to standardize screw threads post-World War II.

Screw thread system agreed in 1948 between the United States, Canada and the United Kingdom after the supply chaos of the Second World War made cross-Atlantic incompatibility intolerable. It took the 60-degree American thread angle but harmonised diameters, pitches and tolerances across the three nations. The ISO metric thread, agreed during the 1960s, eventually displaced it for new design work, but Unified threads remain in widespread use across North American industry.

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