Drill head for use with microtunneling apparatus

A drill head for use with a microtunneling apparatus to produce a bore, the drill head including a housing having an annular shell and a radial member adjacent a distal end of the housing, a cutter bar having at least one cutting element positioned for front cutting, the cutter bar is rotatable across the radial member within a working zone of the bore to produce swarf, an air cavity extending longitudinally of the housing leading to an air aperture in the radial member for supplying air to the working zone, the radial member having at an exhaust aperture leading to an exhaust cavity extending longitudinally of the housing for removing swarf from the working zone, the housing having at least one exhaust spray outlet adapted for spraying fluid towards the exhaust aperture, also including an air cavity extending longitudinally of the housing leading to an air aperture in the radial member for supplying air to the working zone, the radial member having at an exhaust aperture leading to an exhaust cavity extending in a direction parallel to a longitudinal axis of the housing for extracting swarf from the working zone, the air cavity, the working zone and the exhaust cavity defining an air flow path, a pressure adjustment mechanism including a throat member that is positioned between the air aperture and the exhaust aperture to create a venturi flow therebetween, the throat member is adjustable to control venturi flow of air in the working zone at the distal end of the housing for adjusting air pressure in the working zone so as to adjust the extraction of swarf from the working zone.