This paper discusses the engineering and manufacturing development of metric 12-spline flange bolts from “blue sky” ideas through final stages of analysis, testing, and manufacturing.

This fastener was developed in the course of a program to study the development of an Optimum Metric Fastener System (OMFS). Finite element techniques, photoelastic tests, and extensive structural as well as wrenching tests were used to establish a final configuration commensurate with preselected engineering and economic criteria. The developed and manufactured 12-spline flange bolt performance characteristics can be described by lower bearing pressures, lower head stress concentration factors, and lower head spring rates than those found in existing hexagon head designs. Additionally, substantial raw material savings are predicted. Metric 12-spline flange bolts are documented in OMFS-9 (also under consideration as ANSI B18.2.5).