This document specifies the geometric design for each characteristic of screw threads - UNJ profile inch series and the conformance requirements. In addition, the purpose of this standard is to: a. Define the geometric requirements for a selected series of Unified Screw Threads, modified to provide a radius at the external thread root. b. Establish requirements for a continuous radius at the root of the external threads. c. Establish requirements for an increase in the minor diameter of both internal and external threads to accommodate the external thread root radius.