BS 1657:1950

Included angle between pressure and trailing flanks of 52°; standard form of thread has a pressure flank angle of 7°; 'special' form has pressure flank normal to axis of screw. No rigid pitch/diameter relationship. Includes preferred series for diameters and pitches. Tables of tolerances and allowance for three classes of fit. System of gauging with notes on appropriate types and sizes of gauge. Method of measurement of effective diameter of buttress threads, tables of dimensions for the sizes of thread measuring cylinders.Cross References:BS 1044