BURRING METHOD, AND PUNCH TIP

摘要

PROBLEM TO BE SOLVED: To provide a burring method and a punch tip, by which an annular burr is not formed on the inner periphery of the tip end of the cylindrically projecting part formed by a burring process. SOLUTION: The burring method comprises a process for inserting a projecting portion 25 provided at the tip end of the punch tip 21 into a prepared hole 11 formed on a workpiece W, a process for expanding the inlet side periphery of the prepared hole 11 outward when the edge of the prepared hole 11 is formed into a cylindrical shape by pushing the tip end side of the punch tip 21 into the prepared hole 11, and a process for forming the edge of the prepared hole 11 into the cylindrical shape by expanding the inlet side periphery of the prepared hole 11 outward and by pushing the tip end side of the punch tip 21 through the prepared hole 11. The punch tip 21 to be used has a tapered portion 23 formed at the tip end side thereof. An inlet side deformation preventing portion 25 for preventing the inward deformation of the inlet side periphery of the prepared hole 11 by being fitted into the prepared hole 11 formed on the plate shape workpiece W is protrusively provided at the tip end portion of the tapered portion 23. COPYRIGHT: (C)2004,JPO