The production of the precut hole was by drilling, turning and finishing. Subsequently, the edges of the hole were polished in order to prevent, as far as possible, any hardening of the edges and also to produce an idealised surface.This procedure is necessary since the effect of the surface quality of the hole edge on the expansion ratio is greater than that of the material itself.The present work shows a possibility of making available the improved results of modern measuring techniques in sheet metal forming for analytical processing as well. By means of numerical balancing calculations, the yield locus and stress‐strain curve are described with the help of polynomial representations and put into an energetic stability criterion.The limiting strains during plunging were calculated using a SWIFT material as an example.