Abstract: A tool for cutting percussive rotary drilling of boreholes includes a hollow casing having a bit. A hammer piston is installed in the casing for reciprocations and for cooperation with the bit for imparting impact impulses thereto. The hammer piston divides a working space of the casing into a workstroke chamber and a return stroke chamber which are alternately connected through distribution means provided in the casing with a source of a fluid under pressure for reciprocations of the hammer piston.

Abstract: A system for automatic control of a rotary drill comprises a unit for computing the value of drilling tool penetration per single revolution, said unit connected with its inputs to respective transducers and with its output--to an element for comparison of the current value of drilling tool penetration per single revolution thereof with the preset value of such penetration. The preset value of drilling tool penetration is computed by computer means connected with its inputs to respective transducers and to setters of input parameters. With its outputs, the computer means is connected to the element for comparison of the current value of drilling tool penetration per single revolution thereof with the preset value of such penetration, to regulators of drilling tool axial load and rotation frequency and to an element for comparison of the current value of specific drillability of the rock being drilled with the preset value of specific drillability.