TWIST-DRILL BREAKAGE DETECTING APPARATUS

PURPOSE:To permit the breakage of a twist drill to be detected easily and certainly by measuring the synchronous state of the drilling signal by a controller and the detection signal of a chip detector and detecting the breakage of the twist drill from the stop of formation of chips. CONSTITUTION:The hole drilling work for a printed board by a twist drill is carried-out on the basis of the hole drilling signal 23 which has a hole drilling indication part 23a which is transmitted from a controller. When the chip formed by the hole drilling work passes through a pipe which communicates to a dust collector, a chip detection signal 24 which has a chip indication part 24a is transmitted from a chip detector. When the chip indication part 24a does not exist in the part of the chip detection signal 24 corresponding to the hole drilling indication part 23'a of the hole drilling signal 23 in the detection division 25'a of a detection division signal 25, it is confirmed that chip is not formed. In other words, the above-described case is the abnormal state where a twist drill 13 is broken, and an alarm is transmitted to inform an operator of the trouble.