SAE UNF Unified National Fine is equivalent to BSFīSC or CEI thread has no American counterpart. SAE UNC or Unified National Coarse is the counterpart to BSW
The SAE number series would be equivalent to the BA series equivalents would be the Unified Thread System, formally known as the American Standard but renamed in 1949. threads, four families of threads were developed a miniature series known as BA or British Association, a coarse thread series known as BSW or British Standard Whitworth, a fine thread series known as BSF or British Standard Fine, and a thread series designed for use on cycles BSC British Standard Cycle or CEI Cycle Engineers Institute. His legacy lived on for the best part of a century in the form of the screw thread that bore his name and various scholarships. After starting from very humble beginnings, he died in Monte Carlo in 1887 a very wealthy man. Being the consummate engineer, Whitworth made many other engineering advances including the art of casting and forging. Of course, screw threads follow a similar convention to gun barrel rifling. After optimization of these design features, Whitworth developed the tooling required to mass produce rifled gun barrels. Not only was it a very tricky machining operation, but much experimentation was required to arrive at the ideal helix angle and depth of rifling in order to optimize these new design features. In the States, rifling was introduced during the civil war. Interestingly, rifling became accepted in small arms long before it was for larger guns, and the result, in the Whitworth period, was that rifle-equipped sharpshooters could pick off artillery crews from beyond the effective range of that artillery! Consequently, there was something of a panic to shrink the artillery’s circular error. Rifling of gun barrels was known since the 1520 to 1525 time frame. In the mid 1850s, rifling of gun barrels was in its infancy, at least for the British. Whitworth’s talents did not go unnoticed by the British military. This is partly due to the radiused corners designed into the Whitworth thread which reduces the possibility of a stress riser. Size for size, a Whitworth thread is stronger than its SAE counterpart. During this presentation, Whitworth also introduced a standard system of gages which was widely accepted. Up to this time no conventions existed for screw threads. In 1841 he presented a paper before the Institute of Civil Engineers where he introduced his revolutionary thread system. After leaving school at the age of 14, Whitworth pursued various engineering opportunities until 1833 when he started his own tool making business. Coincidently, not too far from where this writer was born. Sir Joseph Whitworth was born in 1803 in Stockport, a grimy area of the industrial north west of England. Most, if not all, British cars, motorcycles, airplanes and machinery up the 1970s – and possibly beyond – used Whitworth thread forms. Just as British industry had completed this transition, the European Common Market had other ideas so they then changed, yet again, to the Metric system.!! However, that is getting well beyond the purpose of this article. SAE thread system but this transition took many years to complete.
Of course, this did not include the Russian who were dubious “Allies” at best. The death knell for Whitworth threads was rung during WWII when it became apparent that a common thread system was desperately required for the Allies. How many times, when working on a piece of British hardware, have you fussed and cussed over these crazy thread systems, wrenches that don’t fit and busted knuckles? Whitworth threads are now a thing of the past, which is really too bad, because this fastening system has a lot to offer. Understandably, many people are confused by British screw threads and fastening systems.
Model Engineering and British Pipe ThreadsĪrticle Whitworth and other British threads pdf Whitworth Thread Chart with SAE reference pdf Technical Support WHITWORTH AND OTHER BRITISH THREADS 03 Mar