PURPOSE: To form a good looking and a strong mouth edge simply by fitting an annular part formed in annular recessed shape to a mouth and bending and winding the lower edge of the annular part inside and outward to make them as a united body.

CONSTITUTION: A work (a) to which an annular part C formed in annular concavity is fitted is supported by a rotating work holder 1. When the bottom of the work (a) is pressed and supported by a work pressing piece 8 and the mouth (b) of the work (a) to which an annular part (c) is fitted is pressed and supported by a mouth pressing piece 9 by advancing a handle 17, the work (a) starts rotation. When a handle 7 is turned down in the direction to compress a spring, a bending and winding roll 4 comes into contact with the edge 10 of the fitted annular part (c) and bends and winds the edge 10 inside and outward by the recessed arc face 11 to unite the work (a) and the annular part (c) into one body. Thus, a convex annular mouth is formed.