This Standard specifies requirements for flat dies used for producing screw threads by rolling on bolts, studs, screws and the like. Definitions of the various parts of the dies are included, together with details of the limits of tolerance applicable during manufacture and use. The tolerances on the actual thread form are based on the provisions of BS 84 for Whitworth threads, BS 93 for B.A threads and BS 1580 for Unified threads, but an allowance for die wear is also included. Provision is made for two grades, Grade 1 referring to dies having the thread form ground and Grade 2 to dies having the thread form milled. The tolerances on thread form given in Tables 1, 2 and 3 apply to Grade 1 dies only. Dimensional and other relevant details for duplex dies are also included. Information on the process of thread rolling is given in the Appendix.