To see that reinforcement such as reinforcing rods buried in a substance to be excavated does not break during boring, by boring the substance to be bored, in a short time.
A boring device is composed of a core bit 13 which has a bit to bore concrete C being substance to be excavated at the tip, a rotary shaft 11 where the core bit 13 is attached to the tip, a direct motor 2 which is equipped with a rotor 17 being provided integrally with this rotary shaft 11 passed thereinto, and a power source 1b which applies voltage to the direct motor 2. The direct motor 2 is a DC motor which rotates, being impressed with DC voltage, and the power source 1b is provided with a current detector which detects the current flowing to the motor, and a motor drive voltage stopping means which stops the output of the DC voltage to the motor when the current value detected by that current detector gets over a threshold.
IMAOKA TOSHIO
SATO KUSUO
NIPPON DIAMOND KK
SATO KUSUO
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