Patent ID: 7963138

Claim:
A method for forming a changed diameter portion of a workpiece, comprising: providing a plurality of target processed portions from an unprocessed portion of said workpiece up to a final target processed portion having a plurality of sections with axes inclined at least in a plane relative to a central axis of the unprocessed portion; providing a plurality of intermediate cross, sections and center points thereof on the basis of said plurality of target processed portions; adjusting a relative position between each intermediate cross section of said workpiece and at least one roller revolving around said workpiece to perform a spinning process, in a moving process between neighboring intermediate cross sections out of said plurality of intermediate cross sections; adjusting a revolution diameter of said roller at the center point of each intermediate cross section of said workpiece, in the moving process between neighboring intermediate cross sections out of said plurality of intermediate cross sections; adjusting an angle of a revolution plane of said roller to the central axis of said unprocessed portion at the center point of each intermediate cross section of said workpiece, in the moving process between neighboring intermediate cross sections out of said plurality of intermediate cross sections, to mate the center point, diameter and inclined angle of the revolution plane of said roller inside of a revolving locus of said roller, with the center point, diameter and inclined angle of each intermediate cross section of said workpiece; and driving said roller and said workpiece relatively to each other, with a part of an outer peripheral surface of said roller being always in contact with an outer peripheral surface of said workpiece, to perform the spinning process to change the diameter of the portion to be processed of said workpiece, with the revolution diameter and the angle of the revolution plane of said roller being adjusted simultaneously in the relative motion between said roller and said workpiece, to form said portion to be processed into the shape of said final target processed portion.