Center-hole machining method for a tree blank and center-hole machining apparatus

摘要

It is an object of the present invention to prevent a blank surface from remaining on a shaft blank after machining even when the machining allowance of the shaft blank is set to be small. The present center hole machining method includes first to fifth steps. The first step is a step of obtaining outer peripheral shape data of a plurality of portions of the shaft blank in an axial direction. The second step is a step of obtaining a center axis for determining the center hole by comparing measured data of the plural portions of the shaft blank with design data corresponding thereto. The third step is a step of calculating minimum distance from the center axis to the outer periphery of each of the plural portions of the shaft blank. The fourth step is a step of: determining the center axis as an appropriate center axis when the minimum distance in each of the portions is greater than a machining dimension; and shifting the center axis in a direction of making the minimum distance greater than the machining dimension and repeatedly executing the third step based on the shifted center axis when the minimum distance is less than or equal to the machining dimension. The fifth step is a step of boring a 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.