Punch

Abstract

The present invention generally relates to a punch, and more particularly to the improvement of a bit portion of a punch for forging a screw. A drive recess of the screw head includes four symmetrical arc-shaped grooves and a square groove formed at the center of the arc-shaped grooves. Also, the bit portion of the punch is used for forging the screw, and includes four symmetrical arc-shaped protrusions and a square protrusion formed at the center of the arc-shaped protrusions. Thus, the types of slot, cross, cross-square combination, square and double-cross of the drive bit of the conventional screw driver bit can be adapted to insert into and engage with the drive recess. Particularly, when the screw driver bit having arc-shaped drive bit is simultaneously used, it is easy to control the screw during locking and to generate larger driving torque, thereby achieving the object of practical utility and economizing effort.

1 . A punch for forging a head of a screw, wherein the screw head is provided with a drive recess including four symmetrical arc-shaped grooves and a square groove formed at a center of the arc-shaped grooves, characterized in that: 
 the punch has a bit portion corresponding to the drive recess of the head of the screw and comprising four symmetrical arc-shaped protrusions and a square protrusion formed at a center of the arc-shaped protrusions.    
   
   
       2 . The punch as claimed in  claim 1 , wherein the arc-shaped groove is a part of circle-shaped groove.  
   
   
       3 . The punch as claimed in  claim 2 , wherein the arc-shaped groove has an arc span which is at least more than a half circle.  
   
   
       4 . The punch as claimed in  claim 3 , wherein the arc span is three-fourth of circle.  
   
   
       5 . The punch as claimed in  claim 1 , wherein the arc-shaped groove is a part of oval-shaped groove.