Abstract: A pressure fluid actuated downhole percussion tool includes a reciprocating piston hammer with differential transverse pressure surfaces cooperable with a cylinder housing, a guide sleeve and a bit carried exhaust tube to form opposed pressure fluid chambers to which pressure fluid may be conducted to deliver repeated impact blows to a bit having circumferentially spaced bosses and replaceable cutting inserts. The bit is drivenly connected to the tool by plural drive pins supported in circumferentially spaced grooves in the bit shank and in a removable sub supported by the tool housing. Improved earth penetration performance is realized utilizing a claw bit with a pressure fluid actuated percussion tool providing rotation as well as selective deliverance of impact blows through the bit.

Abstract: A percussive drill bit has a working face opposite a shank end. The working face has a central jack insert and a plurality of peripheral inserts extending from the working face. The ends of the plurality of the peripheral inserts form an impacting plane. The central jack insert is disposed within a recessed portion of the working face and has an end extending between the working face and the impacting plane.

Abstract: A drill bit intended for percussive rock drilling is formed to reduce the occurrence of cavitation during percussive drilling. The drill bit includes an integral skirt and at least one channel for transport of flush medium, such as water. The drill bit has a front face provided with buttons, which define a greatest first external diameter (D0). A recess with a female thread, such as a rope or trapezoid thread for percussive drilling, extends into the drill bit from a rear end face of the drill bit. The recess has an axial depth (L0). The external surface of the skirt includes a conical portion having an axial extension that is greater than one-eighth of the depth (L0) of the recess but smaller than the depth (L0) of the recess.

Abstract: The present invention relates to a rock drill bit for percussive drilling. The drill bit comprises a bit body, a head portion defining a longitudinal center axis. The head portion includes an axially forward rock-crushing surface and a skirt that extends axially rearwardly from the rock-crushing surface. The rock-crushing surface comprises several rock-crushing means. A circumferential outer surface of the skirt is provided with circumferentially spaced apart grooves forming lands therebetween. The grooves and the lands extend generally in an axial direction. An axially rearward portion of a land is provided with a guiding surface. The guiding surface faces radially outwardly. The guiding surface comprises at least one step or a sloping surface such to reduce the diametrical dimension stepwise or continuously, respectively. The guiding surface comprises a first guiding portion and a second guiding portion both situated radially outside of an imaginary extension line of the waist.

Abstract: A male portion for percussive rock drilling includes sections of reduced cross-sectional area. At least one thread for percussive rock drilling is provided at an end of the male portion. The end of the male portion comprises an abutment surface for the transfer of impact waves. The length of the portion is defined as the length of an imaginary cylinder from a plane of the impact surface to a point where the plane ceases to contact a crest of the thread, wherein the length divided by the external diameter of the cylinder lies within a range of 1–2.

Abstract: A fluid distributor device is for a percussive drill assembly including a generally tubular casing (2) having a longitudinal centerline and a piston (6) disposed within the casing so as to define a reservoir chamber (27) in the casing. The distributor device comprises a generally cylindrical body (12) disposed within the casing and including a central axis, two opposing ends spaced apart along the axis, first and second interior chambers and a port fluidly connecting the two chambers. The body further has a plurality of fluid passages extending between the two ends and fluidly connecting the first chamber with the reservoir chamber and a deflectable retainer portion (16) releasably engaged with the casing so as to retain the body at a desired position with respect to the casing centerline. A valve (7) is disposed within the body and is configured to permit fluid flow through the port and to alternatively prevent fluid flow through the port.

Abstract: A connection rod (1) for rock drilling includes a first rod part (2) whidh has an external thread (4) provided at one end thereof, wherein the end of the rod opposite to the one end includes an end portion (6) which carries an internal thread (5), wherein the end portion (6) is joind to the first rod part (2) by friction welding and wherein the end portion (6) has been heat treated prior to being joined to the first rod part (2). The invention also relates to a method of producing such a connection rod.

Abstract: The invention relates to a method for horizontal drilling with a percussion implement and a percussion head or percussion head element mounted in a movable manner relative to the percussion implement, the percussion impulse being transmitted in at least three steps.

Abstract: A cup-shaped drill head with an inner conical surface (2) for force-locking connection with an exterior conical surface (3) of a driving drill shaft (4), which at the leading end changes over into a cup base (5) with a center point (P), whereby in the change over from the cup base (5) to the inner conical surface (2) a lesser curvature (K) is present than at the center point (P).

Abstract: A drill crown (1) used for drilling purposes, especially for rotary percussion drilling of a mouth of a blast furnace. The drill crown (1) consists of a drilling head (4) provided with a plurality of hard material or hard metal inserts (6) and a base body (2) for connection to a drive element etc. in order to drive or impinge upon said drill crown. The hard material or hard metal inserts (6) are received in bores or openings (5) of the drill head (4). According to the invention, at least one hard material or hard metal insert (6) is provided with an at least partially curved or domed surface contour (11) on the end which is received in the drill head (4). Said contour cooperates with a complementary domed or curved surface of the drill head (4) and/or base body (2), whereby the percussive energy required for appropriate drilling power is transmitted in a reliable manner, even when the hard material or hard metal insert (6) is slackened.

Abstract: A rock drill includes a shank. A percussion piston is arranged to hit the back end of the shank. Further, a pulling element is arranged around the shank, to which a pulling force can be directed in such a manner that the shank can, by the pulling force, be moved toward the percussion piston, when stuck drilling equipment is freed. During rock drilling, a push force is arranged to act on the pulling element, the push force being opposite with respect to the pulling force. The push force is designed in such a manner that during drilling the pulling element moves due to the push force toward the front section of the drill to be at a predefined distance from the position corresponding to the impact point of the shank.

Abstract: A drill head for rock drilling comprising cutting edges (1) made of hard material, which is detachably connected axially, over a bearing surface (3), with a drilling shaft (4) with at least one radially projecting driver blade (5a, 5b, 5c) by a bayonet-type connection slot (6a, 6b, 6c), wherein at least one connection slot (6a, 6b, 6c) is present, which forms two axially opposing undercuts (7a, 7b), within which the driver blade (5a, 5b, 5c) has limited axial movement.

Abstract: The rock drill apparatus (1) comprises a rock drill machine (6) provided with a percussion device (4), a feed device (9) and a tool (7), the tool (7) end comprising a bit (8) for breaking rock. The tool (7) is arranged to transmit impact energy generated by the percussion device (4) as a compression stress wave to the bit. The feed device (9) is arranged to thrust the tool (7) and the bit (8) against the rock to be drilled, whereby on drilling at least part of the compression stress wave generated by the percussion device (4) to the tool (7) reflects from the rock to be drilled back to the tool (7) as tensile stress, and impact energy of the percussion device (4) is adjusted on the basis of the level of tensile stress (&sgr;v) reflecting from the rock.

Abstract: The present invention relates to a downhole-hammer drill-bit assembly for removable attachment to a substantially tubular casing of a downhole hammer. The drill-bit assembly has a substantially tubular chuck, a drill-bit, and a substantially tubular retainer. The chuck has a step. The drill-bit has a bit shank, a bit shoulder extending from the shank and a bit head. A 6first portion of the bit shank is in a bore of the chuck. The retainer has a split retainer sidewall, a first end and a second end. The first end has a split retainer collar. The second end has a split retainer ring. The split retainer sidewall is around a portion of the chuck and the bit shoulder. The split retainer collar is around a first surface of the step. The split retainer ring is around a portion of the bit shank between the bit shoulder and the bit head.

Abstract: A retainer device (10) is provided for retaining a drill bit (12) within a percussive drill assembly casing (2). The retainer device (10) includes a generally annular body (16) having a central axis and an inner circumferential shoulder portion (18) disposable within the casing (2) such that the body axis (17) is substantially collinear with a casing axis (2a). The shoulder (17) is deflectable between a first position (P1), where the shoulder (18) is contactable with the bit head (14) to retain the bit (12) within the retainer body (16), and a second position (P2). The second position (P2) is spaced radially outwardly from the first position such that the bit head (14) is displaceable through the body (16) in a direction along the casing axis (2a). Also, the retainer device (10) includes a spacer (24) that locates the retainer body (16) at a desired axial position within the casing (2) and a centralizer (26) that centers the body (16) about the casing axis (2a).

Abstract: A method of boring a hole in which a down hole hammer is pneumatically operated to form a hole, and a cementous material is injected into the hole through a passage in the down hole hammer.

Abstract: A rock drilling apparatus includes a drill string terminating in a drill chuck (32) and a drill bit (16) detachably fitted into the drill chuck, the drill bit having a shank (18) received in the drill chuck, the drill chuck (32) and the drill bit shank (18) having complementary splines and grooves allowing rotation or movement of the drill chuck to be transmitted to the drill bit whilst allowing limited longitudinal movement of the drill chuck relative to the drill bit. The drill bit has a drill head (22) at its lower end which is of greater diameter than said shank, said head having a part (26) above that lower end and below the splined region.

Abstract: A rock drill that comprises a shank (6), the back end of which a percussion piston (10) is arranged to hit. Further, a pulling element (17, 29) is arranged around the shank, to which a pulling force can be directed in such a manner that the shank (6) can by means of said pulling force be moved toward the percussion piston (10), when stuck drilling equipment is freed. During rock drilling, a push force is arranged to act on the pulling element (17, 29), the push force being opposite with respect to the pulling force. The push force is designed in such a manner that during drilling the pulling element (17, 29) moves due to said push force toward the front section of the drill to be at a predefined distance from the position corresponding to the impact point of the shank.

Abstract: A drill bit consists of a bit body having a forward end and a slot in the forward end to hold a hardened cutting blade. The blade has a central slot extending into the forward end thereof such that the slot defines inner side wails and a bridge extending between the inner side walls. A protrusion along the leading face of each of the cutting sides of the blade with each protrusion extending to the forward edge extends the length of the cutting edges and by distributing the load along a greater length reduces the stress to the cutting edge. Protrusions along the trailing face of the blade also extern to the cutting edge and increase the strength of the blade.

Abstract: The present invention relates to a downhole-hammer drill-bit assembly for removable attachment to a substantially tubular casing of a downhole hammer. The drill-bit assembly has a substantially tubular chuck, a drill-bit, and a substantially tubular retainer. The chuck has a step. The drill-bit has a bit shank, a bit shoulder extending from the shank and a bit head. A 6first portion of the bit shank is in a bore of the chuck. The retainer has a split retainer sidewall, a first end and a second end. The first end has a split retainer collar. The second end has a split retainer ring. The split retainer sidewall is around a portion of the chuck and the bit shoulder. The split retainer collar is around a first surface of the step. The split retainer ring is around a portion of the bit shank between the bit shoulder and the bit head.

Abstract: The invention relates to a method for horizontal ground-boring, in particular for rock-boring, by means of a rotating and hammering driven ground-boring device, whereby the device is alternately or simultaneously supplied with compressed air and drilling medium and the compressed air and drilling medium are supplied through a channel.

Abstract: A rock drill bit for percussive drilling, especially top hammer drilling, includes a drill head provided with rock removing members. The rock drill bit is provided with a number of external grooves for conducting cuttings, the grooves extending in the axial direction of the rock drill bit. Formed between adjacent grooves are lands which also extend in the axial direction of the rock drill bit. The rock drill bit has a thread for connection of the rock drill bit to a drill rod. Rear end portions of at least some of the lands define retrac teeth. Each retrac tooth has at least one cutting edge. At least some of the lands comprise a chip surface and a clearance surface that form therebetween an edge angle not greater than 100°.

Abstract: A male portion for percussive rock drilling includes sections of reduced cross-sectional area. At least one thread for percussive rock drilling is provided at an end of the male portion. The end of the male portion comprises an abutment surface for the transfer of impact waves. The length of the portion is defined as the length of an imaginary cylinder from a plane of the impact surface to a point where the plane ceases to contact a crest of the thread, wherein the length divided by the external diameter of the cylinder lies within a range of 1-2.

Abstract: A bit retainer for a percussion bit assembly has a bore and upper and lower lips extending into the bore. Multiple slots extend from the lower end of the retainer member to a terminal end disposed intermediate the upper and lower ends, forming multiple cantilever beam segments. The cantilever beam segments are resiliently, radially deflected by the retention shoulder of the percussion bit to mount and retain the bit.

Abstract: A retainer device (10) is provided for retaining a drill bit (12) within a percussive drill assembly casing (2). The retainer device (10) includes a generally annular body (16) having a central axis and an inner circumferential shoulder portion (18) disposable within the casing (2) such that the body axis (17) is substantially collinear with a casing axis (2a). The shoulder (17) is deflectable between a first position (P1), where the shoulder (18) is contactable with the bit head (14) to retain the bit (12) within the retainer body (16), and a second position (P2). The second Position (P2) is spaced radially outwardly from the first position such that the bit head (14) is displaceable through the body (16) in a direction along the casing axis (2a). Also, the retainer device (10) includes a spacer (24) that locates the retainer body (16) at a desired axial position within the casing (2) and a centralizer (26) that centers the body (16) about the casing axis (2a).

Abstract: A percussive rock drill bit includes a head portion with a forward surface surrounded by a peripheral surface. The peripheral surface supports a wreath of peripheral buttons. Front buttons are mounted to the forward surface inside the wreath of peripheral buttons. The button shave a diameter (D) and a height (H), wherein H/D<1.2. The buttons are welded to an essentially flat part of the forward surface whereby the buttons are metallurgically bound to the head portion.

Abstract: A twist drill (1) has a plurality of of protuberances (9) arranged in the grooves (6) of the helix (4) which project radially outward partially into the groove cross section to prevent clumps.

Abstract: A working tool for use with a percussion power tool and including a cushioning elongate stem (3), and a head (4) connected with the stem (3) for joint rotation therewith and for a limited axial displacement relative thereto, with the tool head (4) being adapted, with respect to its resistance associated with its cushioning properties, to characteristics of the percussion piston (5) of the power tool and with the tool stem (3) and the tool head (4) having mutually abutting each other end surfaces (10) which form at least a partially flat contact upon abutting each other.

Abstract: A drilling and/or chiseling tool (1) comprises a shaft (2) and a cylindrical insertion end (4) connected with the shaft (2) with at least one elongated recess (5 to 8), open toward the outer surface of and toward the free end of the insertion end (9) and forming a rotationally locking groove. A collar (3) is disposed between the shaft (2) and the insertion end (4) and extends at least partially around the tool (1) and projects at least radially outwardly of the shaft (2) and of the insertion end (4). The cylindrical insertion end (4)has a diameter not less than 18 mm and preferably larger than 22 mm. The at least one recess (5 to 8) has a cross-sectional area, extending perpendicularly to the axis of the tool (1), and expands toward the outer surface and is provided essentially in the form of an arc of a circle.

Abstract: A percussive rock drill bit includes a head portion with a forward surface surrounded by a peripheral surface. The peripheral surface supports a wreath of peripheral buttons. Front buttons are mounted to the forward surface inside the wreath of peripheral buttons. The button shave a diameter (D) and a height (H), wherein H/D<1.2. The buttons are welded to an essentially flat part of the forward surface whereby the buttons are metallurgically bound to the head portion.

Abstract: The invention relates to a device (1) for the drilling, notably by percussion or rotary-percussion drilling, and draining of holes in soil or rock. A drill bit (2, 3) mounted on a drill rod (4) creates a bore hole and a jacket tube (6) is coupled to the drill rod (4) or the drill bit (2, 3). In the area adjacent to the drill bit (2, 3) the jacket tube (6) has at least one through hole which opens into an annular space embodied between the drill rod and the jacket tube. In the end area adjacent to the drill bit (2, 3) the jacket tube (6) is surrounded by at least one filter tube (7) having a plurality of through holes or slits (8) which are distributed especially evenly across its circumference. This allows for correspondingly safe and reliable drainage during boring, using simple measures.

Abstract: A drill bit for drilling a borehole having a bit body with an axis of rotation, a leading face, and a plurality of blades upstanding from the leading face. At least one of the blades terminates in a gauge pad having a gauge surface arranged, in use, to face a wall of the borehole. The gauge surface being devoid of cutting elements and terminating at an end remote from the blade at a junction with a gauge pad end wall. The gauge pad carries a cutter having a face and a cutting edge located radially inward of the gauge surface, and the junction of the gauge surface and the gauge pad end wall crosses, radially, between the face of the cutter and the wall of the borehole. The gauge surface may be a substantially continuous surface, and may have at least one additional cutter located angularly between two adjacent blades of the drill bit.

Abstract: A drill bit for drilling a borehole, the drill bit comprising a bit body 10 having an axis of rotation 12, a leading face, a plurality of blades 26 upstanding from the leading face, at least one of the blades terminating in a gauge pad 28 having a gauge surface 29 arranged, in use, to face a wall 30 of the borehole 32, the gauge surface 29 being devoid of cutting elements, the gauge surface 29 terminating at an end thereof remote from the blade at a junction 58 with a gauge pad end wall 56, wherein the gauge pad 28 carries a single cutter 62 having a face 64 and a cutting edge 65 located radially inward of the gauge surface 29, and wherein the junction 58 of the gauge surface 29 and the gauge pad end wall 56 crosses, radially, between the face 64 of the cutter 62 and the wall 30 of the borehole 32.

Abstract: A rotary-percussion device for directional drilling in rock comprises a substantially cylindrical, rotatable body portion (15) housing a percussion hammer, and a frustroconical head (2) eccentrically mounted on the front of the body portion. The minimum diameter face (3) of the head is adjacent to the body portion. The axis (6) of the head is parallel to but offset from the axis (5) of the body. The front face (4) of the head is chisel-shaped and comprises at least one oblique plane (11) sloping forwardly in the same direction as the offset of the head axis relative to the body axis.

Abstract: A percussive drilling component includes a cylindrical male screw thread formed of a steel material. The thread includes thread crests and thread roots interconnected by thread flanks. To protect the thread against corrosion, the thread is coated with a material having a lower electrode potential than the steel material. The coating is situated at least in regions located radially inwardly of the thread flanks. The male screw thread can be attached to a female screw thread of another percussive drilling component, the female screw thread also being coated with the material.

Abstract: A percussive drilling component includes a cylindrical male screw thread formed of a steel material. The thread includes thread crests and thread roots interconnected by thread flanks. To protect the thread against corrosion, the thread is coated with a material having a higher electrode potential than the steel material. The coating is situated at least in regions located radially inwardly of the thread flanks. The male screw thread can be attached to a female screw thread of another percussive drilling component, the female screw thread also being coated with the material.

Abstract: A percussive drilling component includes a cylindrical male screw thread formed of a steel material. The thread includes thread crests and thread roots interconnected by thread flanks. To protect the thread against corrosion, the thread is coated with a material having a higher electrode potential than the steel material. The coating is situated at least in regions located radially inwardly of the thread flanks. The male screw thread can be attached to a female screw thread of another percussive drilling component, the female screw thread also being coated with the material.

Abstract: A percussion or hammer tool bit (20) having a substantially rearward shank portion (24) of a first diameter (ds) and an elongated substantially uniformly cylindrical forward tool portion (26) having a second diameter (dt) in the range of 15-20% greater than the diameter of the rearward shank portion. The overall tool length (Lo) is 90-95% of the overall tool length of the prior art (Lopa). The combination of the increased diameter of the forward tool portion and the decreased length of the overall tool length (relative to the prior art) provides substantially the same or greater mass than the prior art tool bit when the tool bit is used percussively, but is less likely to flex, which reduces the likelihood of stress fracture failure. The forward portion (26) includes a striking face (30), such as a blunt (31), moil point (31′), or chisel (31″).

Abstract: A drill bit that combines the forces of high rotational torque and percussive impact with impact-resistant shear cutting inserts in order to increase formation penetration rates, particularly in deep wells were borehole pressure is high. The drill bit may also be used in cooperation with high-pressure jets that augment penetration, cool the shear cutting inserts, and remove the chips.

Abstract: The invention relates to a device (1) for the drilling, notably by percussion or rotary-percussion drilling, and draining of holes in soil or rock. A drill bit (2, 3) mounted on a drill rod (4) creates a bore hole and a jacket tube (6) is coupled to the drill rod (4) or the drill bit (2, 3). In the area adjacent to the drill bit (2, 3) the jacket tube (6) has at least one through hole which opens into an annular space embodied between the drill rod and the jacket tube. In the end area adjacent to the drill bit (2, 3) the jacket tube (6) is surrounded by at least one filter tube (7) having a plurality of through holes or slits (8) which are distributed especially evenly across its circumference. This allows for correspondingly safe and reliable drainage during boring, using simple measures.

Abstract: A rock drilling tool includes a pilot bit screw threaded into a front end of a drill rod. A reamer is mounted on the outside of the pilot bit. The reamer includes a central opening having a front portion and a rear portion. The front portion is connected to the pilot bit, and the rear portion constitutes a stiffening sleeve which extends around the outside of the drill rod.

Abstract: Overburden drilling equipment for drilling a hole includes a down-the-hole hammer formed by a cylinder and a piston reciprocating in the cylinder due to pressurized water being directed alternately to the upper and lower ends of the piston. Each downward stroke inflicts an impact blow upon an anvil portion of a drill bit extending upwardly within the lower portion of the cylinder. A drill chuck is mounted at a lower end of the cylinder to receive the drill bit. A generally cylindrical casing shoe is attached to a casing and is rotatably connected to the drill bit to be longitudinally advanced thereby during drilling operation. The drill chuck includes at least one key which defines the largest radius of the drill chuck. The casing includes a diametrically reduced portion which has at least one keyway therein. The key and the diametrically reduced portion retain the hammer longitudinally in relation to the drill bit.

Abstract: The present invention relates to a partially enhanced drill bit (10') for percussive drilling. The bit comprises a bit body, at least one annular row of non-enhanced buttons (11') mounted in the bit body; and at least one annular row of enhanced buttons (12') mounted in the bit body radially outside of the non-enhanced buttons. At least one annular row of non-enhanced buttons (11') and said at least one annular row of enhanced buttons (12') are provided to partly overlap each other. There is an axial shoulder (19') radially outside of the non-enhanced buttons (11'). There are chamfers (20') at least partly surrounding the enhanced buttons (12'). These chamfers (20') interrupt the shoulder (19') in the circumferential direction.

Abstract: A combination drilling member includes an axially elongated drill, such as used for drilling rock, having an axially extending shaft (2) with a first end leading in the drilling direction containing a cutting bit (3). The shaft (2) has at least one helical drilled material removal groove (4) and an auxiliary element encircling and detachably connected to the shaft (2) intermediate the ends thereof. The auxiliary element (6) has at least one elastic plastic part (9) extending around the shaft and containing a through hole (10) for the shaft where the plastic part is secured to the shaft by at least one of frictional and positive locking engagement against inadvertent axial displacement and held against relative rotation to torques of up to 40 Nm.

Abstract: A substantially tubular retainer member is provided, having a bore of substantially uniform internal diameter which can slip over the retention shoulder of the percussion bit, whether that shoulder is solid or threaded. Pins are then driven through holes in the retainer, under the retention shoulder. The pins retain the head of the bit in the event of bit breakage.

Abstract: A roof bolt bit arrangement comprising a combination spade drill body having a rotational axis, a shank portion, a generally planar spade cutter portion with a pair of oppositely directed cutting edges extending radially of the axis, and at least one rotatable frusto conical cutter mounted on the shank portion with its cutting edge in the path of the maximum radial extent of each spade cutter portion cutting edge.

Abstract: A downhole hammer bit including at least one bit impact head mounted to a vertical guide member by a plurality of retaining ring segments. Opposed surfaces of the bit impact head and the guide member have corresponding circumferential grooves or groove sections that define a channel or channel sections, respectively, for receiving the retaining ring segments. The retaining ring segments are inserted into the respective channel/channel section via a bore that extends from an external surface of the hammer bit. A pin disposed in the bore retains the retaining ring segments in the channel/channel section. The retaining ring segments engage the upper and lower surfaces of the channel/channel sections along an extended arc, reducing the stress and possibility of mechanical failure.

Abstract: The present invention relates to a drilling tool for percussive drilling by means of a top hammer unit, which unit gives compressive pulses. The tool comprises at least one drill tube (12) and a drill bit (11), which cooperates via a connection. The drill bit comprises a bit head (13) provided with crushing means (15) and a shank (17). A shoulder (20) is provided in connection with the bit head, said bit portion having a first abutment surface (21) facing towards a free end of the tube. The free end of the tube facing towards the drill bit is povided with a second abutment surface (23), said top hammer unit being provided to tannsfer compressive pulses to the tube. Each compressive pulse is transferred to the drill bit via the impact surfaces (21, 23). The tube and the drill bit comprise cooperating device (19, 24, 25) for driving and retaining. The tool is defined by that it has a relation between the length of the shank and the length of the bit head that is 5 or more.

Abstract: A rock drilling tool for percussive drilling includes a drill bit and a drill tube cooperating by means of shoulder abutment in a threaded connection. The connection includes at least one male thread and a female thread. The male thread is provided on a shank being an integral part of the drill bit. The drill bit is provided with a shoulder at the inner end of the shank, the shoulder having an abutment surface facing towards the free end of the shank. The female thread is provided in the drill tube and the free end of the drill tube is provided with an impact surface. The threads are cylindrical. The combination of shoulder abutment with a short head provides straight energy transfer at a rock drilling tool.

Abstract: A drill including an elongate shaft (2) a rear end (5) of which is formed as a shank, and a drilling head (10) provided at the front end of the shaft (2) and having central cutting edges (11, 12) extending from a leading center point (14), which is provided substantially at an extension of a shaft axis, backward toward a circumference of the drilling head, and at least one minor cutting edge (13) a portion (n) of which extending transverse to the shaft axis projects beyond a circumference of the shaft (2), with the projecting portion (n) having a length equal from about 10% to 100% of an entire length of the minor cutting edge.