Abstract: A drilling mast assembly (20) mounted on a vehicle (24) for operation in a vertical position and comprising an elongated main mast (44), a secondary mast unit (46) swingably mounted on the main mast (44) for movement from a locked position aligned and contiguous with the main mast (44) to a position swung away from the main mast (44), percussive unit (48) mounted on the secondary mast unit (46) and having a sinker drill (48) movable vertically relative and parallel to the main mast (44) for forming an initial opening in a surface therebelow, and an auger unit (49) having an augar drill (51) mounted on the main mast (44) for vertical movement relative and parallel to the main mast (44) along a longitudinal axis aligned with the longitudinal axis of the percussive sinker drill (48).

Abstract: In a rotary drilling device for powering a drill string into subterranean strata and having a vertically alignable drill mast, a drill head assembly for applying rotational movement to the drill string, elevational means on which the head assembly is mounted on said mast for vertical movement thereon, and with the head assembly including a support housing for a rotary drive unit pivotally movable from an operating position in alignment with the drill string to a pivoted position out of such alignment.