Unified Thread Standard

Adopted by the Screw Thread Standardization Committees of Canada, the United Kingdom, and the United States on Nov 18, 1949 in Washington, D.C., the Unified Thread Standard or UTS are standards for screw threads used in the above countries with the hope they will be adopted universally. They may be found in the ASA (now ANSI) publication, Vol. 1, 1949.

The ISO preferred series, based on metric rounded numbers is the standard that has been adopted world-wide and has displaced all former standards, including UTS. In the USA, where UTS is still prevalent, over 40 % of products contains ISO preferred. Of the above mentioned countries, the UK has completely abandoned its commitment to UTS in favour of the ISO preferred series, and Canada is inbetween. As the remnant of products still using UTS complete the switch to ISO preferred, it is just a matter of time before the UTS vanishes completely.