DRILLING MACHINE FOR VERY SMALL HOLES

摘要

The drilling machine includes a tool damage preventive system having a rotation cycle detecting element detecting the rotation cycle of a spindle from an air spindle of the drilling machine in a non-contact manner; a comparator comparing the detected signal with a reference voltage to produce a waveformed signal; a divider dividing the comparator 's output to produce a signal with a plurality of rotation cycles; an AND gate performing an AND operation with respect to an output signal of the divider and a high-frequency oscillating frequency; a counter citcuit counting a pulse signal output from the AND gate; a signal processing means obtaining a rotation number per minute from a resultant value of the counting and comparing the number with a previous rotation numbe to obtain an error value, and comparing the error value with the preset value so as to produce Z-axis value; and a step motor performing an Z-axis driving of the spindle from the signal processing means.