| 摘要 |
PURPOSE:To carry out the cut-in control efficiently without generating unnecessary vibration by outputting an excessive load signal when the cutting force acting on at least one among a plurality of twist drills increases and by instructing the retreat of all the twist drills. CONSTITUTION:When an excessive load is applied on at least one of the drills 6a and 6b, a signal is outputted from one of the excessive load detectors 9a and 9b, and a stop signal is outputted from an OR circuit 10, and the cut-in motors 3a and 3b shift the cut-in tables 4a and 4b upwardly by an instruction device 17. After each cutting force acting on the drills 6a and 6b is reduced, the motors 3a and 3b shift the tables 4a and 4b downwardly, and boring operation is started by the drills 6a and 6b again. Therefore, the boring works by the drills 6a and 6b are completed at the same time without generating unnecessary vibration on a positioning table 13, etc., and cut-in control can be carried out efficiently. |
