Shrink fit design for precision gear forging dies

The usual way to shrink fit design for precision forging of gear dies is to use thick wall cylinder theory (analytical approach) assuming that bore diameter is equal to pitch diameter by neglecting actual gear tooth shape. For more accurate determination, finite element method (FEM) can be used. The actual stresses predicted by FEM are much higher than the analytical approach, so that the design of the gear shaped die is beyond the capability of the analytical approach. In this paper, analytical approach for dies with gear teeth is modified using FEM solution sets. FEM analyses results are verified by experiments. During experiments cylinder approach is observed to be inadequate for forging loads. An easy to use set of formula and nomograms for determination of sizes of die and ring, and radial interference are presented. The solution set is verified with experiments. Proposed equations can safely be used for shrink fit design of precision forging gear dies.