PURPOSE: To achieve the additional saving of cutting work and the improvement of yield by plastically working the surface of a shaft blank material which is engaged and supported into the center holes on both end faces by a pair of centers, by moving a die between the centers, which is coaxial to the axial center of the centers, parallel to the axial center.
CONSTITUTION: A shaft blank material, for example, a drive shaft blank material 305, is obtainable by cold plastic working, and coaxial center holes are formed on both end faces thereof. Stationary and movable centers 403, 405 which coaxially oppose to each other on a base 401 are engaged with these to support the blank material 305. Next, a die supporting base 407 fitted with a die coaxially to the axial center of both centers between both centers is moved rightward of the figure by a hydraulic cylinder for press whereby teeth are formed on the teeth part 304 of the blank material. At this time, the left side end part 302 of the blank material receives tensile force, but since constant pressing force in the rightward direction of the figure is held exerted to the center 405 by a hydraulic cylinder 406, no elongation occurs. The spline part 306 of the blank material is worked in the similar manner and these may be worked with good concentricity.
OUMI KAZUHIKO
IIFUSHI JIYUNICHI
