SERRATION WORKING METHOD

PURPOSE:To execute a burr-removal of a prepared hole and a serration working by one process, and to improve a productivity by using a punch provided with a punching guide part and a serration working part, when performing the serration working to a forging on which a prepared hole is formed. CONSTITUTION:A burr 3 is left in the end part of a prepared hole 2 of an object to be worked 1 on which the prepared hole 2 is formed by means of cold forging, etc. This object to be worked 1 is fixed and set in a die 8, and a punch 5 provided with a punching guide part 7 and a serration working part 6 is subjected to rolling reduction into the prepared hole 2. When the punching guide part 7 passes through, the burr 3 of the prepared hole 2 is punched and removed, and subsequently, the serration working is executed by depressing further the punch 5 and inserting the serration working part 6 into the part of the prepared hole 2. By using this punch 5, the burr-removal and the serration working can be executed by one operation, therefore, the productivity is raised.