Abstract: The invention is a transmission sleeve for the reverse circulation down hole hammer activated by fluid under pressure, the hammer including an outer hammer casing, a drill bit retaining means (17) and a drill bit (10) retaining means (17) and extending forwardly therefrom. The transmission sleeve (25) comprises a transmission sleeve retaining means to retain the transmission sleeve (25) to the hammer, a flange (28) to direct exhaust fluid from the hammer extending from the transmission sleeve retaining means towards the cutting face (14) of the drill bit (10) so that the exhaust fluid is directed towards the cutting face (14) and a chamber (30) that extends circumferentially around the drill bit (10) into which the exhaust fluid flows prior to discharge from the end of the flange (28).

Abstract: The present invention relates to a sacrificial transmission sleeve for a reverse circulation down hole hammer of the percussive type actuated by a fluid under pressure, including an outer sleeve, a drill bit retained in retaining means, the transmission sleeve comprising a body and an annular flange extending from the body towards the drill bit, wherein the transmission sleeve has an outer diameter greater than that of the outer sleeve and substantially the same as the drill bit.