Punching die for manufacturing seal member and method for manufacturing seal member

A method comprising:

• manufacturing a plurality of seal members for winding around an exhaust gas purifier body from a sheet of an inorganic fiber mat having a contour, wherein the manufacturing comprises:
• forming a punching die by supporting a first blade on a base plate with the first blade having a cutting edge extending to form a loop, and supporting a plurality of second blades on the base plate at an outer side of the first blade, wherein each second blade includes only one notch having a substantially constant width;
• punching the inorganic fiber mat with the punching die by using the first blade to punch out a frame-shaped unnecessary portion, which includes the contour of the inorganic fiber mat, and a seal member formation portion, from which only the plurality of seal members are obtained and which is surrounded by the frame-shaped unnecessary portion, from the inorganic fiber mat, and using the plurality of second blades to form perforations in the frame-shaped unnecessary portion, the perforations each extending from an inner edge to an outer edge of the frame-shaped unnecessary portion and including a cut part that is cut by the second blade and an uncut connection part that is not cut by the notch of the second blade for tearably connecting linear-shaped or L-shaped unnecessary fragments of the frame-shaped unnecessary portion to one another, wherein the cut part of the perforation is formed at least at the outer edge of the frame-shaped unnecessary portion, the uncut connection part of the perforation is not formed at least at the outer edge of the frame-shaped unnecessary portion, and neither the first blade nor the second blade are arranged at the location corresponding to the uncut connection part of the perforation;
• tearing up the uncut connection parts to divide the perforated frame-shaped unnecessary portion into a plurality of linear-shaped or L-shaped unnecessary fragments;
• and
• removing the linear-shaped or L-shaped unnecessary fragments from the seal member formation portion.