| 摘要 |
PROBLEM TO BE SOLVED: To efficiently and accurately perform hole drilling work by inexpensively manufacturing a hole drilling unit by keeping high mechanical strength. SOLUTION: This drill device is composed of the hole drilling unit 22 installed on the tip of an inner rod 16 connected to a shank rod of a rock drill surrounded by an outer pipe 12 buried in a drilled hole. This hole drilling unit 22 is composed of a crown-shaped integral object of a hole drilling bit part 26 and a link bit part 28, and this hole drilling unit 22 is removably connected to the inner rod 16 via a bit adapter 30. COPYRIGHT: (C)2004,JPO&NCIPI
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