Disclosed is an automatic force adjustment control system for mobile drilling machines and methods for automatically adjusting a force on a down-the-hole drill bit of a drill string of a mobile drilling machine. A method may include: monitoring bit air pressure of the down-the-hole drill bit during an automatic down-the-hole drilling operation; and automatically adjusting a force provided to the drill string based on the monitored bit air pressure so that the bit air pressure approaches a target air pressure value.

A down the hole rock drilling machine and a method of drilling rock. The drilling machine includes a reciprocating piston, which has a sleeve-like configuration. Inside a central opening of the piston is arranged one or more fluid passages for conveying pressurized fluid during the work cycle of an impact device of the drill machine.

A down the hole rock drilling machine and a method of drilling rock. The drilling machine includes a reciprocating piston, which has a sleeve-like configuration. Inside a central opening of the piston is arranged one or more fluid passages for conveying pressurized fluid during the work cycle of an impact device of the drill machine.

A ground drilling device with a percussion piston for drilling into the soil, comprising at least one housing section for the percussion piston, wherein an insert is arranged in the housing between the drilling head tip and the percussion piston such that the insert transmits at least a portion of the energy of the percussion piston to the housing, and the insert is held in the housing by means of a shrinking adhesion connection.

A coating architecture is disclosed that includes a substrate having a surface finish R.sub.a of 0.3μ or finer, an intermediate layer overlying and in contact with the substrate; and a solid lubricant layer overlying and in contact with the intermediate layer. The test results of applying the coating architecture to a reciprocating hammer drill utilizing the coating is also disclosed.

A coating architecture is disclosed that includes a substrate having a surface finish R.sub.a of 0.3μ or finer, an intermediate layer overlying and in contact with the substrate; and a solid lubricant layer overlying and in contact with the intermediate layer. The test results of applying the coating architecture to a reciprocating hammer drill utilizing the coating is also disclosed.

A directional drilling apparatus using a water hammer unit according to the present invention includes a hammer body in which a bit unit configured to perform boring work is installed to be movable upward and downward at an end portion of the hammer body, a piston slidably installed on the hammer body and including an operating fluid discharge part formed in a longitudinal direction, a drive unit installed between the hammer body and the piston to support an upper portion of the piston and configured to move the piston upward and downward using water supplied through a rod connected to the hammer body, a hammer unit including a rotary shaft coupled to a bit by a first coupling part so as to transmit a rotational force in a state in which the hammer unit passes through the piston installed on the hammer body and is moved upward or downward by the bit, and a mud motor unit coupled to the hammer body and configured to rotate the rotary shaft.

A directional drilling apparatus using a water hammer unit according to the present invention includes a hammer body in which a bit unit configured to perform boring work is installed to be movable upward and downward at an end portion of the hammer body, a piston slidably installed on the hammer body and including an operating fluid discharge part formed in a longitudinal direction, a drive unit installed between the hammer body and the piston to support an upper portion of the piston and configured to move the piston upward and downward using water supplied through a rod connected to the hammer body, a hammer unit including a rotary shaft coupled to a bit by a first coupling part so as to transmit a rotational force in a state in which the hammer unit passes through the piston installed on the hammer body and is moved upward or downward by the bit, and a mud motor unit coupled to the hammer body and configured to rotate the rotary shaft.

A piston actuated drilling tool includes a housing, a top sub, a piston and a drive sub. The piston has a nose at its forward end that is slidably mounted for reciprocating movement within the housing and which strikes a mandrel located at the forward end of the housing. An integrated retaining and bushing system has a retaining ring arranged for preventing the mandrel from detaching from the rest of the tool. The retaining ring encases a bushing for co-operation with the piston nose to stabilise and guide the piston and provide a timing event for percussion of the tool.

A piston actuated drilling tool includes a housing, a top sub, a piston and a drive sub. The piston has a nose at its forward end that is slidably mounted for reciprocating movement within the housing and which strikes a mandrel located at the forward end of the housing. An integrated retaining and bushing system has a retaining ring arranged for preventing the mandrel from detaching from the rest of the tool. The retaining ring encases a bushing for co-operation with the piston nose to stabilise and guide the piston and provide a timing event for percussion of the tool.