| 摘要 |
PROBLEM TO BE SOLVED: To improve the working efficiency while shortening the time to be required for boring of a work placed for positioning on a surface plate. SOLUTION: A drill 30 set at a first predetermined position P1 for boring of a work 12 is rapidly fed from a turnout position L to a first working start position M1. The drill 30 is fed for cutting from the first working start position M1 toward the work 12 at the feeding speed for working. When a monitor means for monitoring the load current of a motor for rotating the drill 30 judges that the real load current value input to a comparing unit exceeds a set current value, the work top surface detecting signal is output from the comparing unit to a computing part. The computing part computes the work feeding quantity of the drill 30 considering a position of the work when the work top surface detecting signal is output as a first work top surface position W1, and computes a second working start position M2 at a second predetermined position P2 for boring.
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