| 摘要 |
A drilling machine is provided with a quill feed device for reciprocating a quill, a driving member and a driven member, disposed between a spindle rotatably supported by the quill and a driving source therefor in such a manner as to produce a relative angular displacement therebetween according to magnitude of a load applied on a tool held by the spindle, a detector generating a series of pulse signals correlated to the relative angular displacement between both members, a counter numerically counting the pulse signals generated from the detector in respect of one rotation of the spindle, a memory memorizing numerical data, corresponding to the relative angular displacement while the tool being separated from a workpiece, counted by the counter device, and a comparator for comparing the value memorized in the memory and an actual counted value in the counter. The quill is, in the event the actual counted becomes larger than the memorized value by a predetermined limit, returned backwards once before being re-advanced.
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