Sheet retainer for punching ceramic green sheet and punching apparatus

A punching apparatus for punching a through hole in a sheet, comprising:

• a base for laying said sheet,
• a punching tool provided with a cutter section for performing said punching and being movable toward said base, and
• a sheet retainer, said sheet retainer being composed of elastic material and comprises:
• a support portion disposed on one end in the axial direction and being thick-walled in the radial direction,
• a contact portion disposed on the other end in the axial direction, being thinner-walled in the radial direction than the support portion and having an outer diameter smaller than an outer diameter of the support portion,
• a housing hole axially extending from said contact portion within said sheet retainer to the opposite end, and
• an engagement groove connected to the housing hole and having in the radial direction a diameter larger than a diameter of the housing hole, said engagement groove adapted for engaging and fixedly retaining therein a portion of said punch tool,
• said sheet retainer having an outer surface with an outer diameter being (a) uniformly and inwardly tapered from a location opposite the engagement groove to the one end, and (b) uniformly and inwardly tapered from the location to the other end, and the taper of the outer surface from the location to the one end being different than the taper of the outer surface from the location to the other end.