| 摘要 |
Method of and tool bit for making a hole and a hole-surrounding flange in the wall of a workpiece. The rotatable tool bit includes a piercing head (2), followed in the advancing direction by a helical profile (3) whose lower section (4) has the shape of a truncated cone. The tool bit is advanced in the same direction both during hole-making and flanging. By choosing the advanced distance/revolution different from the helix rise/revolution, the rim of a hole made by means of the piercing head (2) can be gradually lifted up to form a flange (7). |
