Method for forming a bead forming die

A method of forming a press-forming die apparatus for press-forming a sealing bead in a plate between forming a hole in the plate and punching out a gasket from the plate, said sealing bead dividing said gasket into an inner gasket portion including said hole and an outer gasket portion surrounding said inner gasket portion, said method comprising the steps of:

• forming an upper die means for forming a front surface of said gasket by cutting a first base plate perpendicularly to a surface of said first base plate to divide said first base plate into an upper inner die block, having an upper inner die surface for forming a front surface of said inner gasket portion and an upper outer die block, having an upper outer die surface for forming a front surface of said outer gasket portion and fixedly holding said upper inner die block by an upper holder and externally fitting for sliding movement said upper outer die block onto said upper die block;
• and
• forming a lower die means for forming a back surface of said gasket by cutting a second base plate in a vertical direction with respect to a surface of said second base plate by cutting said second base plate perpendicularly to a surface of said second base plate to divide said second base plate into a lower inner die block, having a lower inner die surface for forming a back surface of said inner gasket portion and a lower outer die block having a lower outer die surface for forming a back surface of said outer gasket portion and fixedly holding said lower inner die block and said lower outer die block to a lower holder.

A method of forming a press-forming die apparatus for press-forming a convex sealing bead in a plate between forming a hole in the plate and punching out a gasket from the plate, said convex sealing bead dividing said gasket into an inner gasket portion including said hole and an outer gasket portion surrounding said inner gasket portion, said method comprising the steps of:

• forming a first base plate with two adjacent cuts perpendicular to a surface of said first base plate according to a shape of said convex sealing bead and removing an in-between portion between said adjacent cuts from said first base plate so as to provide an upper inner die block having an upper inner die surface for forming a front surface of said inner gasket portion and an upper outer die block having an upper outer die surface for forming a front surface of said outer gasket portion, with an annular slot left between said upper inner die block and said upper outer die block and fixedly holding said upper inner die block by an upper holder and externally fitting for sliding movement said upper outer die block onto said upper inner die block;
• cutting and forming an annular ring coinciding, in shape and width, with said annular slot from a second base plate;
• inserting said annular ring into said annular slot so as to provide an upper die means for forming a front surface of said gasket;
• and
• forming a third base plate with two adjacent cuts perpendicular to a surface of said third base plate according to a shape and a width of said convex sealing bead and removing an in-between portion between said adjacent cuts from said third base plate so as to provide a lower die means for forming a back surface of said gasket comprising a lower inner die block having a lower inner die surface for forming a back surface of said inner gasket portion and a lower outer die block having a lower outer die surface for forming a back surface of said outer gasket portion, with an annular groove left between said lower inner die block and said lower outer die block and fixedly holding said lower inner die block and said lower outer die block to a lower holder.