Abstract: A pilot bit for use with an auger bit in an auger bit assembly secured to the downhole end of tubular drill stem for drilling boreholes in earth formations comprises a tubular pilot bit body having a downhole end and an upper end at the axially opposite end of the body, the body being dimensioned to be telescopically received within an axial bore of an auger bit and being releasably connectable to the auger bit against axial and angular displacement, an axial throughbore extending through the body for telescopically receiving an earth sampling tool, a closure device secured to the downhole end of the pilot bit for opening and closing the throughbore, and pilot bit cutting teeth secured to the closure device.

Abstract: A drill bit latch assembly for releasably securing an earth drill bit to the bottom end of a drill string comprises a tubular housing adapted to be secured to the bottom end of a tubular drill string, drill bit holder adapted to be secured to a drill bit, and a latch assembly. The drill bit holder is telescopically movably received in one end of the housing and coupled thereto for rotation with the housing. The latch assembly is telescopically received in the other end of the housing. The latch assembly releasably engages the holder and is operative with the housing for maintaining the holder in a predetermined operative position within the housing. The latch assembly is responsive to an unlatching tool lowered down the drill string to unlatch the holder.

Abstract: A double-walled drill pipe, having a plurality of outer pipe lengths connected end-to-end and a plurality of inner pipe lengths connected end-to-end and concentrically disposed within the outer pipes and defining an annular fluid flow passageway and a return flow passageway, is provided with an inner pipe support arrangement for minimizing stresses applied to the inner pipe lengths when blows are applied to the outer pipe lengths to drive a cutting bit. Each outer pipe length is provided with a ledge on its inner surface to provide a seat for an abutment on the outer surface of its adjacent inner pipe. When a blow is applied to the outer pipe lengths, the outer pipe is forced downwardly but due to inertial effects, the inner pipe unseats and is permitted to fall under its own weight. A resilient shock ring may be positioned on the length to cushion the fall of the inner pipe and provision may be made to limit axial displacement between the inner and outer pipes.