Abstract: The present invention relates to a down-the-hole hammer comprising an external cylindrical outer wear sleeve (5), a sliding piston (8) mounted for reciprocating movement within the outer wear sleeve to strike a percussion bit (1) of a drill bit assembly located at the forward end of the outer wear sleeve.

Abstract: An attachment for a fluid-operated percussion drill tool, the drill tool having a backhead assembly for attachment to a drill rod. The attachment comprises a shaft attachable to the backhead assembly, wherein the shaft comprises a central bore in fluid communication with a pressure bore of the drill rod. The attachment further comprises a sleeve co-axially slidably mounted on the shaft, the sleeve comprising an outer shoulder at a rear end thereof, and at least one rearwardly-directed exhaust passage. Pressurised air supplied from the central bore of the shaft to urge the sleeve rearwards into a closed position in which air is prevented from exhausting through the exhaust passage. When a restriction is encountered at the shoulder, the sleeve moves forward to an open position in which air is permitted to exhaust through the exhaust passage adjacent to the restriction.

Abstract: The present 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); axially extending splines (36) on the stub shank (32) slideably engageable with complementary splines (35) formed on a drive chuck (4) whereby rotational drive from the chuck (4) may be transmitted to the stub shank (32); bit retaining means adapted for engagement with complementary retaining means on the stub shank to retain the stub shank in the drill bit assembly; and engagement means on the chuck (4) adapted for connecting the chuck (4) to a drive means (5) of the fluid-operated percussion drill tool. The bit retaining means comprises a bit retaining ring (41), and the complementary retaining means comprises a retaining shoulder (37) on the stub shank, wherein the bit retaining ring is arranged to engage the retaining shoulder to retain the stub shank in the drill bit assembly.