CORE BIT AND EXCAVATOR

摘要

PROBLEM TO BE SOLVED: To prevent the generation of resistance caused by the friction of the peripheral surface of the tube of a core bit and the wall surface of the hole of the tube. SOLUTION: The core bit 13 is constituted of the cylindrical tube 14 having a through-hole 14a and the bit 15 provided to the leading end of the tube 14. A spiral grinding particle layer 10a going toward the rear side of a rotary direction toward the front side thereof is formed to the inner peripheral surface 14' of the tube 14. A spiral abrasive particle layer 10b going toward the leading end side of the rotary direction toward the front side thereof is formed to the outer peripheral surface 14" of the tube 14.