To provide a method for boring a hole of a large diameter with the low surface roughness of a profile and high quality using a drill of a long service life at a relatively short machining time, even if a drill spindle of a high maximum rotational speed is used.
Step-Dwell machining for repeating a step for inserting a drill to continue boring after the standby of a predetermined time at the time of drawing the drill is used for a conventional step machining. When a standby time is not provided, because the torque of the drill spindle with a high maximum rotational speed is low, a time is required for recovering the rotational speed decreased by cutting resistance, so that a short time for descending and ascending the drill spindle is not enough for the recovery or reduction of a cutting temperature.
KAWASAKI YUTAKA
IRIE AKIRA
