Puncher

Abstract

A puncher is used when piercing a workpiece with a piercing punch while the workpiece is kept pressed by a stripper. The cover provided on the puncher is made of metal and a diameter of a cover portion at and near a tip end side is smaller than that of the other cover portion other than the cover portion. The other cover portion of the cover receives a biasing member. The cover portion at a tip end side gradually reduces its diameter toward the tip end to form a tapered portion. The puncher provides a long lifetime, guarantees sufficient pressing force onto a workpiece, and punches a hole at a position near and nearer a corner of the workpiece having adjacent metal plate surfaces forming an angle of from 90 degrees to 95 degrees at the corner.

1 . A puncher comprising:
 a cylindrical cover with a one-end opening hole;   a piercing punch, a tip end surface of which is protruded from the one-end opening hole, and which is loosely but not removably inserted with respect to the cover;   a cylindrical stripper provided between the cover and the piercing punch in a retaining state;   a biasing member by which the stripper is protruded more than the piercing punch from the one-end opening hole; and   wherein, when the stripper is pressed in against biasing force of the biasing member, the tip end surface of the piercing punch becomes protruded out from a through-hole formed at a protruding end of the stripper, the cover is made of metal, and a diameter of a second cover portion of the cover at and near the one-end opening hole side is smaller than that of a first cover portion other than the second portion.   
   
   
       2 . The puncher according to  claim 1 , wherein the first cover portion receives the biasing member. 
   
   
       3 . The puncher according to  claim 2 , wherein the second cover portion reduces in diameter toward the opening hole to form a tapered portion. 
   
   
       4 . The puncher according to  claim 3 , wherein an inclining line of the tapered portion is concave inwardly. 
   
   
       5 . The puncher according to  claim 1 , wherein the biasing member is a compression coil spring. 
   
   
       6 . The puncher according to  claim 1 , wherein piercing process is conducted by the piercing punch while a workpiece is kept pressed by the stripper.