METHOD FOR FORMING GROOVE

PURPOSE:To form a shaft sealing O-ring groove that the tolerance of dimension can be enough satisfied by restricting a body to be formed to the rotation impossible state and the movement impossible state, and synchronously revolving a rolling die. CONSTITUTION:A body W to be formed is restricted with a clamp 2 of a forming machine 1 so as not to be rotated. As a result, the body W to be formed can be applied with the compressive force of the axial direction. In this state, because plural numbers of dies 8 rotating around its own axis is pressed to the body (W) to be formed while revolving in a vertical surface to the axis of the body W to be formed, each die 8 begins to rotate with the friction force or the tangential force from the point of time being brought in contact with the body W to be formed, and rolls around the body W to be formed. Therefore, the equilibrium of force is kept with plural numbers of dies 8 in the radial direction of the body W to be formed, and because the compressive force is applied in the axial direction, the enlargement of groove width due to the escape of axial direction of the material with the pressed die 8 or the impulse of the die can prevented.