ISO 68-2:2023

This document specifies the basic and design profiles for ISO inch screw threads (UN and UNR). UN applies to both internal and external threads. UNR only applies to external threads. A flat or rounded root contour, due to the threading process, is specified for UN threads, while only a defined rounded root contour is specified for UNR external threads. This document is applicable to the inch fastening screw threads.