| 摘要 |
PROBLEM TO BE SOLVED: To provide a boring head that resists damage to a cutting point of a bit, reduces large intermittent shocks and reduces hole bending even when impacting rock or the like during boring, in a boring head for a screw auger for use in drilling ground in civil engineering works or the like. SOLUTION: The boring head is mounted in a tip end of a screw auger rod with a peripheral helical blade. The periphery of a base shaft whose base is fixed to the screw auger rod has three helical blades of the same outside diameter, and to tips of the three helical blades, pluralities of small bits with an acute cutting point are attached respectively. COPYRIGHT: (C)2004,JPO
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