CUTTER HEAD

PROBLEM TO BE SOLVED: To prevent lowering in excavating efficiency even if cutter bits are abraded, and enhance the safety and the working efficiency in a tunnel excavator. SOLUTION: A drivable-rotatable cutter head 31 is arranged in a front part of an excavator main body, and freely rotatable rotary bodies 36a and 36b of the cutter head 31 are arranged with a support shaft 35 in the direction almost orthogonal to the rotational direction of this cutter head 31, and cutter bits 39a and 39b to which tips 40a, 40b, 41a and 41b are brazed in a multilayer shape, are installed on these rotary bodies 36a and 36b, on the one hand, a plug 43 which checks rotation of the rotary bodies 36a and 36b and allows rotation of the rotary bodies 36a and 36b according to an abraded condition of a cemented carbide tip is provided, and locking pins 47a and 47b and locking holes 48a and 48b are arranged to hold them in its rotary position when the rotary bodies 36a and 36b rotate by a specified angle.