Optimum working conditions in the cross rolling of stepped shaft

Abstract The conditions resulting in the formation of a central cavity during the cross rolling of stepped shaft are investigated by calculating the tensile stress arising at the mid-point of the rod cross-section. Considering the forming to be limited by relative slipping between roller and rod, and the necessity to avoid defects in the rolled products, the optimum reduction in cross-sectional area of rod R op and the effective range of forming angle α and spreading angle β of the tool wedge for practical use are proposed as follows: R op = (0.15 + 0.0038 α)β 0.325 1.93 β −0.925 ⩾ 0.15 + 0.0038 α ⩾ Mβ −0.325 where M is a constant and = 0.35–0.40 , and α and β are expressed in degrees. If the recent application of the cross-rolling process for producing a counter-gear shaft — which is one of parts of the transmission gear for automobiles — is considered, the results of the analysis are effective in determining the limits of forming and to suggest the points to be considered when designing the shape of the roller and in selecting the appropriate working conditions.