Casting Study: Two-Piece Punch Body

For three generations, B-V has been producing heavy-duty, specialty hand punches from two sand-cast malleable iron halves. Sand casting inaccuracies required sorting and extensive fitting to locate matching halves. Thickness variations up to 0.025 in. were encountered, and reference points for machining were inconsistent. Almost every surface was ground or polished for fit and/or appearance. Altogether, the 65 separate machining, fitting, assembly, and finishing operations contributed to excessive manufacturing costs. Attempts to reduce costs using malleable iron sand castings were futile and B-V looked for a non-ferrous alternative. Zinc die casting more than met expectations. All parts are now exactly the same, and halves are randomly mated without shaping or finishing. The as-cast die pocket accepts the steel die without sizing and the ticket slot is formed during casting. The punch profile on the male half is holding up well, and the cast pivot-pin holes align exactly. The die-cast halves are one-third the cost of the malleable iron sand castings. The 65 operations have been reduced to 20, equaling a 50 percent reduction in manufacturing cost. The zinc punch has the same weight and feel as the iron punch and only a small amount of cosmetic polishing with a mild abrasive belt is needed. Punches are produced as-cast or chrome plated for those still looking for a shiny, bright punch.