| 摘要 |
PURPOSE:To form a joining end of a square pipe excellent in strength easily and efficiently by pressing the square pipe between a mandrel and a die and tapering top and bottom and forming a side to bulged form having a flange face at the tip. CONSTITUTION:A mandrel 61 having tapered faces 62a at the top and bottom and provided with the tip part 62 having lacked left and right sides is fitted into a square pipe 3. A die 71 in which a forming chamber 74 consisting of upper and lower formed faces 73 and formed faces 75 that extend to left and right outside is shifted by a lift cam 72 to press the tip of the square pipe 3. By this way, a joining end 3a having upper and lower faces 11, 12 of tapered off faces 13, 14, left and right sides 15, 16 of widened tapered faces 17, 18, a flange part consisting of a bent part 23, a bulged part 22, excellent in strength, rigidity and appearance, high in dimensional accuracy and having joining part 25 of sufficient welding area can be formed easily by one process. |
