Some advice for those unfamiliar with thread systems and fasteners. Do not mix fasteners with differing thread angles. People will tell you that Whitworth and UNC are "the same". They are not. Whitworth form threads have a 55 degree angle whilst Unified form is 60 degree. Whilst BSW and UNC will screw together with the exception of 1/2", this is not good practice. Mismatched thread angles cause crushing of the crests of the threads and have self-loosening characteristics. Nor will they maintain set torque.
Angles are:- BS series 55 degrees
UN series 60 degrees
Metric (all sorts) 60 degrees
BA 47.5 degrees





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