Abstract: A vertical thrust boring machine adapted to be positioned in the horizontal drift of a mine and to cut a tunnel extending upwardly from the drift so as to remove ore or other cuttings therefrom. The machine includes a rotary table for lifting a drill string which in turn supports the cutter head, and is characterized by drill stem sections having a spline connection on their lower ends, and a drive coupling ring associated with the rotary platform having a mating spline connection, so that when changing the length of the drill string the lowermost drill stem section can slide or float vertically relative to the rotary platform at the same time that it is being drivingly rotated.