PURPOSE: To caulk a pipe and a shaft sufficiently, by forming the face of percussion of a die so that the curvature of this face is changed from the curvature of a pipe befor contraction to that after contraction according as going from both side end parts of the front toward the center.

CONSTITUTION: In respect to a pecussion face 16 of a die 15, both side end parts 18 and 18 of the front are formed on the arc face having a radius equal to a radius R1 of a pipe P before contraction, and a center 19 is formed on the arc face having a radius equal to a radius R2 of the pipe P after contraction, and it is desirable that the proportion of the arc face having the radius equal to the radius R2 to the whole of the percussion face 16 is 30W60%. Both end parts 20 and 17 of the die 15 are conncted smoothly by a taper face 21. First, the die 15 is opened, and a shaft S where grooves G are worked and the pipe P are positioned in the die 15 and are fixed; and next, a swaging device is operated to perform the caulking work while clamping the die 15.