BS ISO 2904:2020 pdf free.ISO metric trapezoidal screw threads – Basic dimensions.
BS ISO 2904 ISO metric trapezoidal screw threads – – Basic dimensions 1 Scope This document specifies the basic dimensions of ISO metric trapezoidal screw threads in accordance with ISO 2902. The values refer to the design profiles in accordance with ISO 2901. This document is chiefly applicable to traversing threads for traversing motion on machines, tools, etc. It can also be used for fastening threads. 2 Normative references The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.ISO 5408, Screw threads一Vocabulary 3 Terms and definitions For the purposes of this document, the terms and definitions given in ISO 5408 apply. ISO and IEC maintain terminological databases for use in standardization at the following addresses: ISO Online browsing platform: available at https://www.iso.org/obp 一IEC Electropedia: available at http://www.electropedia.org/4 Symbols For the purposes of this document, the following symbols apply. D1 basic minor diameter of internal thread D2 basic pitch diameter of internal thread D4 basic major diameter of internal thread d basic major diameter of  xternal thread (nominal diameter) d2 basic pitch diameter of external thread d3 basic minor diameter of external thread P pitch acclearance at major and minor diameters R1 radius on crest corners of external thread on design profile R2 radius on root corners of internal and external threads on design profile .BS ISO 2904 pdf download.