| 摘要 |
PROBLEM TO BE SOLVED: To keep approximately regular boring performance from the beginning to the end of use and to demonstrate prescribed boring performance even by weak force. SOLUTION: A drill tool bores concrete etc., by rotating a bit driving shaft 3 attached to the front side of a tool body 2 to protrude and a diamond bit 4 fitted to the tip of the bit driving shaft 3. The tool body 2 includes an excitation device which makes the tool boy 2 generate exciting force with its magnitude pulsing and changing along the bit driving shaft 3. The diamond bit 4 includes a base 24 fitted to the tip of the bit driving shaft 3, a first approximately annular or cylindrical diamond whetstone body 25 which is fixed to the base and has an opening hollow 31 on one side, and a second diamond whetstone body 26 which is set in the hollow 31. The second diamond whetstone body 26 is formed to be lower than the first diamond whetstone body 25. COPYRIGHT: (C)2008,JPO&INPIT
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