DRILL HEAD FOR DIRECTIONAL BORING
A drill head for an apparatus for directional boring inlcudes a bit having a cutting portion for use in steering, such as a gage tower mounted with carbide studs, suitable for cutting both hard and soft rock, a holder for a device for detecting angular orientation of the bit, and a pneumatic hammer connected head to tail with the bit at the front end. The valve in the hammer initiates reciprocation of the hammer in response to rearward movement of the bit, such as in response to a pushing force exerted by the drill string. The drill string components are preferably keyed to one another so that the orientation of the cutting portion of the bit used for steering is automatically matched to the position of the sonde. The sonde may project laterally so that its mass centroid is on the opposite side of the cutting portion of the bit used for steering to provide better cutting action. Such a drill head is suited for drilling in soil, soft rock and hard rock conditions.