Abstract: A down hole hammer comprising a cylindrical casing defining a piston chamber between a top sub at one end and a drill bit support at the other end, a piston within the piston chamber for reciprocation between the one and other end, the piston having a central portion which is sealingly engaged with the internal wall of the casing, one end portion of the piston being intended to impact on the drill bit with movement to an impact position at which position the one end portion sealingly defines a first space at the one end of the piston chamber, the internal wall of the casing adjacent the top sub having two sets of axially spaced fluid ports, the piston adapted to cooperate with a first set of the fluid ports to admit fluid into the first space when the piston is in the impact position and cause movement of the piston to a raised position where the piston is in spaced relation from the drill bit support, the piston adapted to cooperate with a second set of said set of fluid ports to admit fluid into a second sp

Abstract: A down hole hammer assembly comprising a reverse circulation hammer (11) having a drill bit (12) mounted to one end of a housing which accommodates a percussive hammer, the other end of the housing being adapted to be mounted to a drill string, the assembly further comprising a support member (14) receivable on the lower end of a bore hole casing (13) which is receivable over the drill string, the support (14) comprising a first part (15) adapted to be fixed to the lower end of the casing and a second part (16) rotatably received on the first part (15) and capable of limited axial slidable movement thereon, the second part (16) being engagable with the drill bit (12) to be rotatable with the drill bit (12) on rotation of the drill bit (12) in one direction and to be movably axially with the drill bit (12) the drill bit (12) being disengagable with the second part (16) to be able to be movable axially relative to the second part (16), flow passageways being provided between the drill bit and the second part to

Abstract: A make-up system of a down-the-hole hammer. The down-the-hole hammer is of the type comprising a hammer casing (111) having a top sub (112) mounted to one end and a drill bit chuck mounted to the other end. The casing accommodates a piston which is caused to reciprocate within the hammer casing.

Abstract: A fluid operated hammer for rock drills comprising; a cylinder, a drill chuck mounted at one end to receive a drill bit; a drill sub attached to the other end; a tubular fluid feed tube mounted in the drill sub and extending towards the chuck, the longitudinal central axis of the feed tube corresponding to the longitudinal central axis of the cylinder; at least one set of apertures provided in the side wall of the feed tube and spaced from each end; a piston slidably mounted in the cylinder and over the feed tube to move between the drill chuck and drill sub the lower end being adapted for striking a portion of the drill bit extending through the drill chuck; a first passageway in said piston communicating with one end face thereof and opening into the center of the piston at a location spaced along the length of said piston; a second passageway in said piston communicating with the end face of the piston communicating with the end of the piston opposite to that of the first passageway and opening into the ce

Abstract: A stabilizing tool comprising a substantially cylindrical body; said body having a plurality of substantially cylindrical chambers formed therein said chambers being located axially within the body and spaced symmetrically around the body with respect to the longitudinal central axis thereof, wherein the diameter of the chambers is such that a portion of the wall would extend beyond the perimeter of the body to provide axial rectangular openings in the side of the body; each end of the body being provided with an axial fluid passageway which is divided to provide a fluid path through each chamber; stabilizing rollers rotatably mounted upon a hollow shaft mounted in said chambers such that the circumference of rotation of the rollers extend through said rectangular openings beyond the body; a lubricant reservoir provided in said body and vented to the fluid passageway for the application of fluid pressure to the lubricant in the reservoir; and outlets in the reservoir communicating with the bearing surfaces be

Abstract: A rotary drill bit having a bit head and roller cutters mounted thereon, wherein each roller cutter is rotatably mounted upon a shaft fixed at one end to the bit head, the shaft being provided with an annular formation having a spherical outer surface thereon, forming the bearing surface of the shaft. The roller cutter is provided with an inner bearing surface in bearing engagement with that of the shaft and of corresponding configuration.