| 主权项 |
1. A burring method for forming burring holes having a first axis line as center axis lines with respect to a first wall portion and a second wall portion facing each other, the burring method comprising:
a first process of disposing an internal unit of a burring apparatus between the first wall portion and the second wall portion, disposing a first external unit of the burring apparatus outside the first wall portion, and disposing a second external unit of the burring apparatus outside the second wall portion; a second process of, out of a piercing punch and a burring punch which are shaft members having the first axis line as the center axis lines provided in at least one of the internal unit, the first external unit, and the second external unit, and are provided so as to be movable along the first axis line, first, forming prepared holes having the first axis lines as the center axis lines with respect to the first wall portion and the second wall portion using the piercing punch, and thereafter, forming burring holes having the first axis line as the center axis lines with respect to the first wall portion and the second wall portion using the burring punch; and a third process of detaching the internal unit, the first external unit, and the second external unit from the first wall portion and the second wall portion. |
