Provides for two forms of thread, designated respectively 'standard' having a pressure flank angle of 7 degrees with an included angle between the pressure and trailing flanks of 52 degrees; and 'special' having the pressure flank normal to the axis of the screw with an included angle between the pressure and trailing flanks of 52 degrees. Does not specify a rigid pitch/diameter relationship but includes preferred series for both diameters and for pitches. Provides tables of tolerances and allowances for three classes of fit, namely, close, medium, and fine. Includes a recommended system of gauging, with notes on the appropriate types and design sizes of the gauges; also includes an explanation of the method of measurement of the effective diameter of buttress threads together with tables of dimensions for the best sizes of thread measuring cylinders.