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.
PUBLISHED
SRPS ISO 68-2:2007
PROJECT
prSRPS ISO 68-2:2026
10.99
New project approved
Jan 1, 2026