Patent ID: 7934410

Claim:
An expansion die for manufacturing metal containers comprising: a work surface configured to expand a diameter of a metal container having a closed bottom, the work surface comprising a progressively expanding portion and a land portion; and an undercut portion; wherein the land portion is between the progressively expanding portion and the undercut portion and an outer diameter of the land portion is a maximum diameter of the die; wherein the undercut portion comprises: (a) an undercut surface; and (b) an outer diameter of the undercut surface, wherein the outer diameter of the undercut surface is : (i) at least approximately 0.01 inches smaller than the outer diameter of the land portion; and (ii) no less than a minimum diameter so as to reduce but not eliminate frictional contact between the undercut surface and the metal container; and wherein the work surface is dimensioned so that when inserted into the metal container the entire land portion and at least a portion of the undercut portion enter the metal container causing the diameter of the at least a portion of the container to expand.