All stresses, and particularly those due to friction, which occur during pressing and sizing operations have consequences on the dimensions, on internal stresses, and eventually on micro-cracks. This friction can have an influence on the variations of the density from one point to another but, when used in a proper way, it can help the movement of punches and increase homogeneity. Three different types of re-pressing are considered—drawing, sizing, and coining—and examples are given to show their influence on mechanical properties and especially on the fatigue limit.
