Method and device for caulking a caulking member

A method for caulking a caulking member to a metal plate, the method comprising:

• providing a caulking member in the form of a caulking nut having a threaded hole formed in a body portion of the caulking member and a caulking recess portion communicating with the threaded hole,
• the caulking recess portion having an undercut shape with a first diameter portion at an end of the caulking member and a second enlarged diameter portion disposed within the body portion of the caulking member;
• providing a device for caulking that includes a die with a caulking protrusion formed at an end surface thereof, the entirety of the caulking protrusion having a diameter that is smaller than the first diameter of the caulking recess portion formed in the caulking member, and a punch, which is formed of a pressing portion and a downward protruding portion which is formed to have a cylindrical shape and protrudes from an end portion of the pressing portion and arranged to be opposite to the die and to be capable of approaching to and separating from the die;
• placing the metal plate on the die, and arranging the caulking member on the metal plate by aligning a position of the caulking recess portion with the caulking protrusion;
• moving the punch toward the die so that the pressing portion of the punch presses the caulking member against the metal plate and the downward protruding portion is inserted into the threaded hole to restrict and sandwich the metal plate between the caulking protrusion and the downward protruding portion during caulking;
• and
• pressing the caulking member against the metal plate with the punch to plastically flow a portion of the metal plate through the first diameter portion and outwardly into the enlarged second diameter portion of the caulking recess portion to caulk the caulking member to the metal plate without boring the metal plate.