This Standard specifies requirements for dies of circular form used for the production of screw threads by rolling on bolts, studs, screws and similar components. Definitions of the terms used are given together with details of the limits of tolerance necessary for their manufacture and during their use. The tolerances on the actual thread form are based on the provisions of BS 84 for Whitworth threads, BS 93 for B.S threads and BS 1580 for Unified threads with the addition of an allowance for the wear of the die. The tolerances given in This Standard allow for only one grade of thread, suitable for rolling threads to the close fit limits of the system concerned, but this ensures the possibility of rolling threads to any wider tolerances necessary for coarser fits.