This International Standard lays down the form and dimensions of thread undercuts for bolts, screws and similar externally threaded products, recommended for use in those cases where an undercut is needed for threaded components such as plugs, unless other-wise specified in the appropriate product standard.
SIS SS-ISO 4755:1986 history
1986SIS SS-ISO 4755:1986 Fasteners - Thread undercuts for external metric ISO threads