| 摘要 |
PURPOSE:To start the expansion of the hole with the optimum metal flow, to expand the hole into a specified diameter making superior the property of the internal surface, and to extremely improve the durability of the tool, by improving the shape of the tool at the starting part and following main part for the expanding work of the hole. CONSTITUTION:The expanding tool 10 consists of the tapered down type hole expanding part 11 and the cylindrical guide part 12 continuing to the lower end. The hole expanding part 11 consists of the truncated cone type main part 14 for the hole expansion and the starting part 15 for the hole expansion continuing to the front of the main part 14. The curved part 16 is swelling type and the curved part 17 is sinking type. The cylindrical guide part 12 is straight in the longitudinal direction of the cylinder, and its spearhead is made round 18. At first the starting part 15 for the hole expansion begins the expanding work for the hole at the optimum metal flow, and then, truncated cone type main part 14 for the hole expansion successively works the expansion as far as the specified hole diameter; as a result, the hole expansion is carried out without causing deterioration of the durability of the tool due to the seizing of the tool, and without causing degradation of the internal surface property of the hollow metallic billet. |
