Abstract: A rock drill bit comprising a main body arranged to drill at the end of a shaft of the drilling assembly, the main body having a diameter larger than that of the shaft, a front face on the main body arranged to engage an area for drilling and an outer surface extending rearwards from the front face. A flush channel extends through the main body to the front face and at least one open end of the flush channel at the front face is arranged to provide a fluid to an area at the front face. A plurality of contact points on the front face for engaging the area. A flush groove extends from the open end of the flush channel outwards to the outer surface and at least one relief bore extends from the front face rearwards to a relief area behind the outer surface for providing a release for the fluid from the front face to the relief area. The relief bore is located within the flush channel between the open end and the outer surface such that the debris is flushed from the drilling area to an area behind the main body.

Abstract: Apparatus for blast hole drilling includes a hammer and drill bit driven by a hydraulic drive motor outside the hole through a drill string extending along the drilled hole to the drill bit. The drive motor is carried on a mast with a telescopic hydraulic cylinder driving the motor along the mast in a forward direction for forwarding the drill bit along the hole to the rock face and for applying a feed force on the drill bit at the rock face and in a rearward direction for reducing the feed force and for withdrawing the drill bit from the hole. The cylinder assembly has a pulldown pressure side fed at a constant supply rate and a holdback pressure side controlled to discharge the fluid when moving downwards and to supply the fluid at a constant rate when pulling up.