| 摘要 |
PROBLEM TO BE SOLVED: To improve the burring accuracy by machining a V-shaped groove in an outer circumference of a prepared hole in a work. SOLUTION: A punch die P to punch the work W in cooperation with a die D is provided with a V-shaped groove machining blade tip portion 35 at the position corresponding to the outer circumference of the prepared hole A of the work W placed on the die D. The prepared hole A in the work W is punched by using the punch die P, the V-shaped groove 41 is machined in the outer circumference of the prepared hole A, the prepared hole A is protruded to the V-shaped groove 41 side, and a flange F1 is formed to implement the burring.
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