Method of producing fluid-chamber component elements

A method of producing fluid-chamber component elements comprising the steps of:

• fixing a steel plate having a circular contour to a rotary mold unit having a peripheral portion for thickening the peripheral portion of the steel plate by pushing a roller rotated in a direction opposite to the direction of rotation of the rotary mold unit, and forming a seal ring groove in the outer peripheral surface of the peripheral portion thus thickened;
• preliminary thickening that portion of the steel plate which corresponds to the peripheral portion of the rotary mold unit forming thereby a preliminary thickened portion the greatest thickness of which is smaller than the thickness at the step of forming a seal ring groove, said preliminary thickened portion having a tapered outer surface;
• finally thickening said preliminary thickened portion thereby forming a final thickened portion having a tapered outer surface, said preliminary thickening and said final thickening being successively conducted at different steps with the use of different forming rollers and different forming molds such that the taper of the outer surface of the preliminary thickened portion is different from the taper of the same outer surface of the final thickened portion;
• and
• forming a seal ring groove in the outer peripheral surface of said final thickened portion.