To prevent cracks by reducing the bearing gap of a swaging die, and performing the swaging while an instable part to be formed on a tube end part is abutted on a rear wall of a bearing part of the die to suppress the outward expansion of the instable part.
Because the tube reduction by swaging is of a contraction, stress is released at an end part passing though a die part, the outwardly opening force is generated, and a tube end part after reduction becomes an outwardly expanded working instable part 2. Elongation of the stock is reduced by the work hardening because of the cold working. An inner wall 13 in the rear of a bearing part of a die 10 is abutted on the working instable part 2 of the tube end part passing through a die part 11 by reducing the bearing gap 12 of the die 10 to demonstrate the effect to suppress the outward expansion during the working and to prevent cracks.
MOCHIZUKI HIROYUKI
MAKITA SHINYA
Next Patent: FLANGE JOINT AND ITS MANUFACTURE