PURPOSE: To carry out a flank machining process, a thinning process and a rounding process in series by providing an intermediate sleeve having eccentric points having two positions which are different from each other by an angle of 180deg., a drill feed cam plate and a cam ring for laterally sliding an intermediate sleeve holding housing.

CONSTITUTION: A drill 20 held in a predetermined posture is started from an eccentric position A in an intermediate sleeve 3, and is rotated toward the other end surface of a grinder 16 together with the intermediate sleeve 3. Simultaneously, the drill 20 is fed in accordance with a rotating amount determined by the cam surface of a cam plate 6 while one of flanks is formed by grinding. Then a holding shaft 2 is turned by an angle of 180deg., and after the other flank is formed by restarting the drill from the point A, the holding shaft 2 is turned by required angle so as to change the posture of the drill, performing a thinning process at two position while the drill 20 is moved straightforward at another eccentric point B. Next, a styles is made abut against a cam ring 10 so as to form a cutting edge at the rotating center of the drill in a convex round shape with the use of the rotation of the holding shaft 2 and a lateral slide action of the housing 4 by the cam surface of the cam ring 10.