Metal gaskets for cylinder heads, and methods for manufacturing same

A method for manufacturing a metal gasket for a cylinder head, the metal gasket including:

• at least one substrate made of a resilient metal layer and having cylinder holes formed in correspondence with cylinder bores in a cylinder block to be mounted with the cylinder head in an engine, annular beads each formed around a different one of the cylinder holes, coolant holes formed around an outer periphery of each of the annular beads in correspondence with coolant holes of the cylinder head and a cooling water jacket or coolant holes of the cylinder block, and an outer bead formed and positioned to entirely enclose the annular beads and the coolant holes;
• and
• a step adjustment plate made of a metal layer and having a plurality of annular portions each disposed over and around an outer periphery of a different one of the cylinder holes of the substrate;
• and a plurality of protruding pieces formed integrally with each annular portion at a peripheral edge thereof, each protruding piece of the step adjustment plate engaged through the substrate, the method comprising the steps of:
• forming a prepared hole in each protruding piece of the step adjustment plate;
• forming a tubular portion including a plurality of projecting segments by inserting a die including a polygonal pyramidal punch into the prepared hole so as to bend up a peripheral portion around the prepared hole while cutting the peripheral portion into segments;
• forming in the substrate a fastening hole in correspondence with a position of the tubular portion formed in the step adjustment plate;
• and
• directly engaging the protruding piece through the substrate by inserting the tubular portion of the step adjustment plate through the corresponding fastening hole formed in the substrate, and subsequently folding the plurality of projecting segments of the tubular portion over to an outside of the substrate and flattening out the projecting segments.