A steerable rock bit attached by a drill string to a horizontal directional drill. The bit comprises a plurality of flanges radially extending from a central hub and a slanted face formed in the body of the bit. Cutting elements such as polycrystalline diamond compacts are disposed on the flanges on one side of the flanges such that they will provide cutting force when the bit is rotated in the direction of the cutting elements. The bit is advanced generally straight when the bit is rotated and is advanced at an angle away from the slanted face when the bit is not rotated.