A drill assembly for percussive drilling, comprising a drill bit and a percussion device. The drill assembly further includes a hollow cylindrical foot valve partially received within a first central flushing channel thereof and extending therefrom in the uphole direction, such that the foot valve is also partially received within a central recess of an impact piston of the percussion device, at least when the impact piston is in a lowermost position of its reciprocation cycle, and such that the foot valve is no longer received within the central recess, at least when the impact piston is in an uppermost position of its reciprocation cycle. The foot valve includes an internal stiffener extending radially inwardly from at least two circumferential positions of an inner surface of the foot valve.

Method for controlling the direction of a drilling device which drills a hole into a ground wherein a hammering and rotatable bit (3) is used as the drilling bit and the device comprises coupled with the bit (3) a hammering device (2) behind the bit (3) and a drill arm which is potentially related to it wherein the rear part (15) of the hammering device or the drill arm locates in the drilled hole or inside a casing tube (1) which covers the drilled hole in a free space so that there is space for the mentioned rear part (15) to move in the direction of the radius of the drilled hole and that the location of the bit (3) in the ground during the drilling is observed on the grounds of the data received from the position sensors which indicate the location of the bit (3), characterized in that in the method the direction of the drilling is steered by adjusting only the position of the mentioned rear part (15) in relation to the center line (C) of the drilling by organizing a support, which is deviated from the center line (C) or located on the center line (C), for the mentioned rear part (15) with the help of a support element (5, 5, 7) which is located in the drilled hole or at the inner surface of the casing tube (I) which support is adjusted at the feed end of the drilling device and wherein a direction angle (a) is formed only for the bit (3) and hammering device in relation to the mentioned center line (C).

Method for controlling the direction of a drilling device which drills a hole into a ground wherein a hammering and rotatable bit (3) is used as the drilling bit and the device comprises coupled with the bit (3) a hammering device (2) behind the bit (3) and a drill arm which is potentially related to it wherein the rear part (15) of the hammering device or the drill arm locates in the drilled hole or inside a casing tube (1) which covers the drilled hole in a free space so that there is space for the mentioned rear part (15) to move in the direction of the radius of the drilled hole and that the location of the bit (3) in the ground during the drilling is observed on the grounds of the data received from the position sensors which indicate the location of the bit (3), characterized in that in the method the direction of the drilling is steered by adjusting only the position of the mentioned rear part (15) in relation to the center line (C) of the drilling by organizing a support, which is deviated from the center line (C) or located on the center line (C), for the mentioned rear part (15) with the help of a support element (5, 5, 7) which is located in the drilled hole or at the inner surface of the casing tube (I) which support is adjusted at the feed end of the drilling device and wherein a direction angle (a) is formed only for the bit (3) and hammering device in relation to the mentioned center line (C).

A rock drilling shank adaptor has at least one flush hole extending radially through the body of the adaptor in communication with an axially extending internal bore. The flush hole in a direction from an external side to an internal side includes a surface at a rearward region that is curved at least at a radially inner portion to extend in an axial direction towards a forwardmost end of the adaptor to increase the resistance of the adaptor to stress concentrations whilst achieving a desired flow rate of flushing fluid flow into the internal bore.

A rock drilling shank adaptor has at least one flush hole extending radially through the body of the adaptor in communication with an axially extending internal bore. The flush hole in a direction from an external side to an internal side includes a surface at a rearward region that is curved at least at a radially inner portion to extend in an axial direction towards a forwardmost end of the adaptor to increase the resistance of the adaptor to stress concentrations whilst achieving a desired flow rate of flushing fluid flow into the internal bore.

A flow diversion sub for a down-the-hole drill comprising a housing assembly that includes a housing body, a cap extending from the housing body, and a drive shaft having an upper central blind hole and a lower central blind hole spaced from the upper central blind hole, wherein the drive shaft is received within the housing assembly. In operation, one of the housing assembly and drive shaft moves between a first position and a second position relative to the other of the housing assembly and drive shaft. In the first position the upper central blind hole is in fluid communication with the lower central blind hole, and in the second position the upper central blind hole is blocked from being in fluid communication with the lower central blind hole.

A system and method of fabricating a percussion tool that includes one or more surfaces modified using the ferritic nitrocarburization process. The percussion tool includes a piston positioned in sliding contact within a casing. The piston includes an inner wall and an outer wall, where the inner wall defines a passageway extending longitudinally therethrough. The outer wall is positioned in close fitting relationship with an internal surface of the casing. One or more surfaces of at least one of the casing's internal surface and/or the piston's outer wall are modified using the ferritic nitrocarburization process.

A system and method of fabricating a percussion tool that includes one or more surfaces modified using the ferritic nitrocarburization process. The percussion tool includes a piston positioned in sliding contact within a casing. The piston includes an inner wall and an outer wall, where the inner wall defines a passageway extending longitudinally therethrough. The outer wall is positioned in close fitting relationship with an internal surface of the casing. One or more surfaces of at least one of the casing's internal surface and/or the piston's outer wall are modified using the ferritic nitrocarburization process.

A rock drilling shank adaptor has at least one flush hole extending radially through the body of the adaptor in communication with an axially extending internal bore. The flush hole in a direction from an external side to an internal side includes a surface at a rearward region that is curved at least at a radially inner portion to extend in an axial direction towards a forwardmost end of the adaptor to increase the resistance of the adaptor to stress concentrations whilst achieving a desired flow rate of flushing fluid flow into the internal bore.

A system and method of fabricating a percussion tool that includes one or more surfaces modified using the ferritic nitrocarburization process. The percussion tool includes a piston positioned in sliding contact within a casing. The piston includes an inner wall and an outer wall, where the inner wall defines a passageway extending longitudinally therethrough. The outer wall is positioned in close fitting relationship with an internal surface of the casing. One or more surfaces of at least one of the casing's internal surface and/or the piston's outer wall are modified using the ferritic nitrocarburization process.