dies utilized for this process will be determined by the desired shape and diameter of the final ring structure and by the following general principles if the die has a relatively flat rolling surface it will cause a reduction in material thickness and a diametrical increase with minimum axial redistribution of material such flat rolling surfaces cause internal circumferential stresses to be set up in the rolled structure unless the amount of reduction is uniform across the axial cross section of the rolled ring structure conversely if the die face is pointed it will cause a shearing of the ring structure resulting in maximum axial redistribution of material with a minimum diametrical growth and almost no circumferential stresses roll bending and roll pinching are two additional methods of axial material redistribution with minimal diametrical growth the dies utilized for this process are shaped so as to combine these four principles in a manner which will provide for axial distribution of ring material with minimum circumferential stresses it will generally be necessary to anneal the ring between die changes since it will have hardened during cold working the work hardening tendencies of the metal or metal alloy material utilized for the ring will generally determine the amount of reduction in material thickness which may be achieved prior to annealing it has been found that most nickel and cobalt based alloys can be reduced by cold rolling about 30 percent prior to interstage annealing however.