CUTTER BIT AND CUTTER DEVICE

摘要

PROBLEM TO BE SOLVED: To provide cutter bits with their cutting ability prevented from lowering during drilling a sectionally different-shape tunnel and provide a cutter device not to cause drilling residuals in drilling the sectionally different-shape tunnel. SOLUTION: Suitable cutter bits 14 are provided on an overcutter 9 for a positively and reversely running cutter head 3 and the ridge lines of chips are radially arranged from the ends of the chips. The cutter bits 14 are so arranged when mounted on the overcutter 9 as to prevent drilling residuals from being formed between the drilling tracks of the cutter bits 14 even during drilling in any direction.