A multifunction drill bit includes an outer shank including an outer lock head, an outer shank body, and an axial hole wherein spiral grooves are on the outer shank body; from a joining portion of the outer shank body and the outer lock head to the outer lock head, a threaded section, a deformable section, and a guide section are provided; each of the threaded and deformable sections include first external threads; the deformable section has outer curved grooves; a deformable concave surface is on an inner surface of the deformable section; and first internal threads are on the guide section; and an inner shank in the axial hole and including a top socket, an inner lock head, and an inner shank body. Second external threads are on an inner surface of the guide section corresponding to the first internal threads. A tip of the drill bit is replaceable.