| 摘要 |
PURPOSE:To eliminate a waste of time liable to take place at the start and end of cutting process, by controlling the step action substantially aiming at only the period of time for a practical cutting process, namely a period of time during which the magnitude of a load exerted on a drill stays above a certain level. CONSTITUTION:In a step of machining start, counting of time is started at the point of time when a cutting process is srated by means of a drill reaching a work through a progressive fast feeding process. Then, back and forth reciprocating motion of a drill is repeated prescribed times of step and only a period of time from the start of cutting to the completion of hole machining is detected at the final step. The period of time in no-load condition after completion of a through hole is free from the target of time counting and the machining end is detected at the progressive end F, then the drill retreats, thus one process of hole machining being completed. |
