John Marshall, Technical Manager at WDS Components Ltd, explains the reason behind the growing product range with inch-size threads.Challenges behind standardisation between Britain, the USA and Canada led to the creation of the Unified Thread Standard (UTS) in 1949. Based on inches, the standard included Unified Coarse (UNC) and Unified Fine (UNF) as the most common examples. 11 years later, the International System of Units was created as the modern form of the metric standard. With origins in Continental Europe, it remains the only standard of measurement, threads included, in almost every country in the world.While the basic profile of UTS and metric threads are the same, the difference in major diameter and pitch (the variation between the thread peaks) removes the potential of compatibility. Within UTS, UNC is more commonly used for general engineering applications while UNF, with its increased thread per inch ratio, is preferred for very small applications and those requiring greater precision and strength, such as aerospace applications.Despite British involvement in the creation of UTS, the UK developed greater ties with Europe and generally adopted the metric thread system. However, following Britain's departure from the European Union, the potential of increased trade with wider partners (including North America) has re-emerged.
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