The present invention, the state-of-the-art drilling surface is formed relates to a bit for excavation, and a plurality of stopper receiving groove disposed on the outer diameter side isometric view, the bit head portion sliding shaft portion is formed at the rear end; And the body is formed to extend in the longitudinal direction, it is formed with a shaft protruding on both sides, wherein the axial projection is inserted along the guide groove formed in the bit head portion and the stopper receiving groove spread to nearby advanced excavation surface of the bit head portion and the folded It is possible to install the wing bits; And said wing bits are a first stopper of the first length in contact with the wing bit installation is deeply inserted into the stopper receiving recess at one side to maintain the unfolded state is projected outward direction of said bit head, wherein the other side may comprise; is inserted into the lower stopper receiving groove outer cylindrical member and a second stopper of the first and second length shorter than the first length to form a folded area of ​​said wing bits installation.