Center hole machining method for shaft blank and center hole machining apparatus

A center hole machining apparatus for a shaft blank configured to bore a center hole for machining an outer periphery of the shaft blank formed by forging or casting, the center hole machining apparatus comprising:

• a shape data obtaining unit configured to obtain outer peripheral shape data of a plurality of portions of the shaft blank in an axial direction;
• a center axis calculating unit configured to obtain a center axis for determining the center hole by comparing measured data of the plurality of portions of the shaft blank with design data corresponding thereto;
• a minimum distance calculating unit configured to calculate a minimum distance from the center axis to the outer periphery in each of the plurality of portions of the shaft blank;
• a center axis determining unit configured to:
• determine the center axis as an appropriate center axis when the minimum distance in each of the plurality of portions is greater than a machining dimension;
• and
• shift the center axis in a direction of making the minimum distance greater than the machining dimension and repeatedly execute the processing of calculating the minimum distance based on the shifted center axis when the minimum distance is less than or equal to the machining dimension;
• and
• a center hole machining unit configured to bore the center hole in an end surface of the shaft blank at a position arranged on a line extended from the center axis determined as the appropriate center axis.