| 摘要 |
PROBLEM TO BE SOLVED: To provide a casing bit for preventing chipping of a carbide tip, by dispersing a load by increasing the number of excavation points, by providing a plurality of top parts (the excavation points) in the carbide tip.SOLUTION: The present invention is constituted of a casing bit provided so that carbide tips 3 and 4 are respectively fixed to two places of a left and part and a right end part of a head part of the casing bit, and the top parts 3a, 3b, 4a and 4b are respectively projectingly formed by two places in a longitudinal width direction of the head part in both respective carbide tips, and among the top parts of four places in total in both carbide tips, the front side top part 3a of the carbide tip 3 of the left end part and the front side top part 4a of the carbide tip 4 of the right end part, are provided along the ridgeline in a lateral direction positioned on the front side of the head part of the casing bit, and the rear side top part 3b of the carbide tip 3 of the left end part and the rear side top part 4b of the carbide tip 4 of the right end part are provided along the ridgeline in the lateral direction positioned on the rear side of the head part of the casing bit. |
