Gaspare, Thank you for posting the images, they really do help visualizing the process. If I understood Hapur correctly, here is a simulation of the (inside) "punch" portion of the set. With it pushing the sheet metal into the cavity of the die. While ordinarily I would think that the punch would be made of steel because of a lack of lateral support. Perhaps he will correct me (?). FP

WW_Ring_Die_Set__Corrected.jpg (92.26 KB, 400 downloads)