Abstract: The invention relates to a drill bit assembly for fluid-operated percussion drill tools comprising a percussion bit (1) having a head portion (3) formed with an axially extending stub shank (32). The stub shank is provided with axially extending splines (36), which are slideably engageable with complementary splines (35) formed on a drive chuck (4). Rotational drive from the chuck (4) may be transmitted to the stub shank (32) by means of the splines. Bit retaining means (6, 7, 41, 42) at the chuck are adapted for engagement with complementary retaining means (37, 51) at a spline portion of the stub shank to retain the stub shank in the drill bit assembly. Engagement means on the chuck (4) are adapted for connecting the chuck (4) to a drive means (5) of the fluid-operated percussion drill tool.

Abstract: A drill bit assembly for fluid-operated percussion drill tools. The assembly comprises a percussion bit (1) having a head portion (3) formed with an axially extending stub shank (32). A drive bush (2) is releasably connectable to the bit head portion (3). Axially extending splines (35) on the drive bush (2) are slideably engageable with complementary splines (36) formed on a drive chuck (4) whereby rotational drive from the chuck (4) may be transmitted to the drive bush (2). The assembly further comprises engagement means on the chuck (4) adapted for connecting the chuck (4) to a drive means (5) of the fluid-operated percussion drill tool.

Abstract: The present invention relates to a percussion hammer for enlarging drilled holes. The hammer comprises an external outer wear sleeve (5), an inner cylinder (7) mounted co-axially within the outer wear sleeve (5), a tubular torque shaft (3) disposed axially and centrally of the hammer assembly, and extending longitudinally through the assembly. The hammer further comprises a sliding piston (6) mounted for reciprocating movement within the inner cylinder (7) and outer wear sleeve (10) and about the tubular torque shaft (3) to strike a hammer bit (1) for reciprocal movement in a chuck (4) adjacent a forward end of the hammer assembly. The hammer bit (1) has a central bore (46) through which the torque shaft (3) extends, such that the torque shaft (3) protrudes forwardly of the hammer.

Abstract: A reverse circulation down-the-hole drill includes an outer wear sleeve (1) and a backhead (2) assembly located at one end of the outer wear sleeve (1) for connecting the drill to a double-walled drill string and to a source of pressure fluid to actuate the drill. A fluid diverter (5) is mounted inside the outer wear sleeve (1) adjacent to the backhead (2). An inner tube (9), concentric with the outer wear sleeve (1) and extending into the fluid diverter (5), defines at least part of a central return passageway in the drill. A bit (10), located by a chuck (3) at the other end of the outer wear sleeve (1), is slidably mounted on the inner tube (9) in an annular chamber (28, 30) defined by the outer wear sleeve, by the inner tube, by the diverter at one end (28), and by the bit at the other end (30).