A rock drill including a helical shank and a drill head. The drill head has an end face pointing in a feed direction and at least one roof-shaped carbide cutting element on the end face of the rock drill. The carbide cutting element extends transversely across the drill head and has cutting edges. The end face of the carbide cutting element has an additional chip space at least in front of the carbide cutting element and includes an encircling step to create the additional chip space in the feed direction.
A drill bit of the present invention is intended to stably perform drilling by lessening a great change in a drilling condition and to avoid reduction of a drilling efficiency even when large chip lumps are generated. In the drill bit, the main cutting blades have main cutting edges each structured such that an inner end thereof is located at the rotation center of the drill and an outer end thereof is located on an outer periphery of a rotation trace of the cutting blades, and the sub cutting blades have sub cutting edges each structured such that an inner end thereof is located to be spaced radially outward apart from the rotation center and an outer end thereof is located to be spaced radially inward apart from the outer periphery of the rotation trace toward the center of rotation.
