PURPOSE: To form a different-sized portion in a single drilled hole.
CONSTITUTION: There are provided a muck discharge blade 3 in which a spiral blade 25 is installed to its outer periphery and which is connected to a rotary drive unit 13 of a drilling machine and a holder 9 connected to the tip of the muck discharge blade 3 and a shaft 11 inserted into the holder 9 passing through the inside of the muck discharge blade 3 and a drilling blade 1 which is expandable and installed in such a fashion that it may be rotated integrally with the holder 9 and an operation lever 17 which moves the shaft 11 in the longitudinal direction and a regulation means 21 which regulates the longitudinal directional movement of the shaft 11. The holder 9 is engaged with the cutting hole blade 1 in a state in which the shaft 11 is moved to the side of the rotary drive unit 13, thereby by keeping the drilling blade 1 in a closed state. In such a state that the shaft 11 is moved to the side of the holder 9, the drilling blade 1 is allowed to be expanded. An engagement part is allowed to be formed in such a fashion that it may be engaged with the drilling blade 1 and hold the expanded state of the drilling blade 1.
SHIRAI KOJI
SAITO MASAYASU
ADACHI YOSHITOMO
ISHIBASHI SHIGERU
FURUKAWA DORIRU TEC KK
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