What Is The Difference Between AF And Whitworth Spanners?

What Is The Difference Between AF And Whitworth Spanners? AF was introduced much later and refers to Across Flats and was related to UNC(universal national coarse) and UNF(universal national fine) threads in the USA A 1/2 inch Whitworth socket is for a nut that fits on a 1/2 inch diameter thread, and is usually 1.5