Thin plate burring processing method and thin plate female screw-forming method

Abstract

A thin plate burring processing method includes a first step of forming a thin portion thinner than an original thickness in a target portion by performing crushing processing on the target portion of a plate-like workpiece, a second step of forming a circular through-hole in the thin portion by punching processing, and a third step of forming an annular portion rising from a surface of the workpiece by performing projection processing with burring processing around the through-hole formed in the thin portion.

What is claimed is: 
     
         1 . A thin plate burring processing method, comprising:
 a first step of forming a thin portion thinner than an original thickness in a target portion by performing crushing processing on the target portion of a plate-like workpiece;   a second step of forming a circular through-hole in the thin portion by punching processing; and   a third step of forming an annular portion rising from a surface of the workpiece by performing projection processing with burring processing around the through-hole formed in the thin portion.   
     
     
         2 . The thin plate burring processing method according to  claim 1 , wherein an area where the surface of the workpiece is formed into a concave shape and/or a convex shape by flow of a crushed material of the workpiece is previously set to be equal to or smaller than an area inside an outer diameter of the annular portion formed by the burring processing. 
     
     
         3 . The thin plate burring processing method according to  claim 1 , wherein a thick portion thicker than the original thickness of the workpiece is formed in an area where the surface of the workpiece is formed into a concave shape and/or a convex shape by flow of a crushed material of the workpiece. 
     
     
         4 . The thin plate burring processing method according to  claim 1 , wherein an area of the thin portion formed by the crushing processing is previously set to be equal to or smaller than an area of the through-hole formed by the punching processing. 
     
     
         5 . A thin plate female screw-forming method, comprising:
 a first step of forming a thin portion thinner than an original thickness in a target portion by performing crushing processing on the target position of a plate-like workpiece;   a second step of forming a circular through-hole in the thin portion by punching processing;   a third step of forming an annular portion rising from a surface of the workpiece by performing projection processing with burring processing around the through-hole formed in the thin portion; and   a fourth step of forming a female screw in an inside wall surface of the annular portion.