| 摘要 |
PURPOSE:To make burring accurately and efficiently by inserting a steel ball into a tube in which an under-hole for burring is bored, and pushing out the steel ball from the under-hole by pressing form both sides of the tube. CONSTITUTION:An under hole is bored in a metallic tube material 18. The outer periphery is restrained by a restraining die 20, and the under-hole and a hole 24 of the restraining dei 20 are made to coincide. Then, a steel ball 21 having diameter equal to specified burring inner diameter is inserted into the tube 18 and pressed uniformly with wedge punches 15, 16. By this, the steel ball 21 is pushed into the hole 24 necessarily bulging the under-hole of the material 18. Next, wedge punches 15, 16 are removed, and a steel ball 25 slightly smaller in diameter than the steel ball 21 is inserted again, and pressed uniformly by wedge punches 15, 16. Consequently, the steel ball 25 necessarily pushes the steel ball 21 out of the material 18. At the same time, the steel ball 25 also falls down. Thus, the steel balls 21, 25 can be recovered easily, and burring is completed. |
