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BS 1768:1963
Specification for Unified precision hexagon bolts, screws, & nuts (UNC & UNF threads). Normal series (British Standard)
Dimensions, general requirements for $9D in to 2 in. Dimensions for bolts, screws, ordinary nuts, thick ordinary nuts, lock nuts, slotted nuts, thick slotted nuts. Formulae for calculation of dimensions for bolt and screw heads and nuts in intermediate or larger sizes. Applies to ferrous and non-ferrous bolts, screws, nuts and, for steel, refers to appropriate qualities up to 75 tonf/in$u2 minimum tensile strength. Manufacturing requirements, including decarburization and rolling laps, mechanical properties and tests for steel bolts, screws, nuts. Steels suitable for various methods of manufacture are listed; testing fixtures and recommended gauges, standard sizes of bolts and screws most likely to be stocked, shortest lengths designated as bolts, identification marking.
British Standards Institution [bsi]