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: A percussion drill 10 has a tubular fluid transmitting body 14, with a drill bit 16 mounted on a drill bit support 20 itself mounted in body 14 via a spring 22 and salines 24. A mass 28 is spring mounted in the body 14 and is movable to impact on a face 26 of the support 20. Mounted to the mass 28 is a rotating valve 32 comprising two valve plates 34, 36. Each plate 34, 36 defines a slot 38, 40, such that rotation of one of the valve plates 36 relative to the other moves the slots 38, 40 into and out of alignment; the change in alignment of the slots 38, 40 alters the flow of drilling fluid through the valve 32, so altering the drilling fluid pressure force acting on the mass 28, so causing mass 28 to push against the spring 30, and impact on the drill bit support 20 providing a percussive act ion at the drill bit 16.

Abstract: A tool for effecting drilling and/or chiseling and including a tubular shaft (2,22) having an axially extending through-channel (8,28) and provided, at one of its axial ends, with a drilling or chiseling head (5), and a connection member (3,23) connected with another of axial ends of the shaft and provided at its end remote from the shaft (2,22) with a shank (4,24), the through-channel (8,28) being connected with the tool circumference by a cross-bore (7,27), and the largest cross-sectional surface (A1,A4) of the connection member (3,23) corresponding at least to 2.5 times of the largest cross-sectional surface of the shank (4,24).

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 rock drill head including a radially extending groove (2a) formed in a head body, a recess (5) formed inside the groove (2a); and at least two, substantially plate-shaped, hard-material inserts located in the groove (2a) and having each a radially extending, segment (4a, 4b) engaging in the recess (5).

Abstract: In a percussion boring machine for producing or widening earth boreholes, the housing is equipped with nozzles and houses a striking piston caused to reciprocate axially by means of compressed air and means of generating pressure which supplies the nozzles with a flushing, cutting, lubricating and/or steering liquid. Since the liquid pressure required for the excavation of the ground surrounding the machine and/or for causing the machine to travel on a curved path is generated in the machine itself, the machine only needs to be supplied through a supply line with a liquid at a slightly raised pressure.

Abstract: In an air actuated down-the-hole hammer for rock drilling, a piston reciprocates within a casing to impact against a rear anvil surface of a drill bit. A foot valve extends axially between the piston and the drill bit. The anvil surface is inclined downwardly in a radially outward direction to cause liquid on the anvil surface to be discharged in a direction away from the foot valve, to prevent damage to the foot valve which could occur if piston impacts were able to create high-speed liquid streams contacting the foot valve.

Abstract: A rotatable cutting bit which comprises an elongate bit body which has a forward end and a rearward end and which defines a peripheral surface. The bit body contains a first seat at the axially forward end thereof. A first cutting insert is mechanically retained in the seat so as to present a clearance cutting edge which radially extends past the peripheral surface of the bit body. The first cutting insert has a leading cutting edge disposed at a lead angle between 50 degrees and 80 degrees.

Abstract: A rock drill for percussive drilling includes a shank, a collar connected to a front end of the shank, and a rod portion which at one end connects to the collar while the other end carries a rock cutting means. A central flush channel extends from the front free end of the shank in a direction towards the front end. The central flush channel has a substantially constant diameter (d) along essentially its entire length; a ratio of the diameter (d) to a smallest outer cross sectional width (D) of the rod portion being in the range of 0.35 to 0.43.

Abstract: A rock drilling rod is manufactured by placing free ends of first and second hollow rod components in abutment, and establishing relative rotation between the free ends to friction weld those free ends together. The first component comprises a thread and a clearance portion disposed adjacent the thread. The first component has a hot hardness value of at least about 170 HV1 at 600.degree. C. Prior to friction welding the components together, the thread, clearance portion and central passage of the first component are heat treated against corrosion fatigue. Then, the thread is high frequency hardened to a depth at least as great as the heat treated layer. Following the welding, the weld is cooled while keeping a core hardness of the respective portions of the first and second components disposed immediately adjacent the weld no lower than 390 HV1.

Abstract: A rotary system having a sectional drill steel column connecting a drilling machine and rotary drill bit and being constructed and arranged to accommodate internal fluid flow to the drill bit without pressure loss, and which column employs a coupler section having both threaded and multi-faced ends for joining adjacent drill steel sections; and further having supplemental bore reamers adjacent to the drill bit to maintain design bore dimensions and accommodate fluid flow and removal of cuttings.

Abstract: A rotatable cutting bit which comprises an elongate bit body which has a forward end and a rearward end and which defines a peripheral surface. The bit body contains a first seat at the axially forward end thereof. A first cutting insert is mechanically retained in the seat so as to present a clearance cutting edge which radially extends past the peripheral surface of the bit body. The first cutting insert has a leading cutting edge disposed at a lead angle between 50 degrees and 80 degrees.

Abstract: A rotary spade drill arrangement comprising a combination spade drill body having a rotational axis, a shank portion, and a generally planar spade cutter portion with a pair of oppositely directed cutting edges extending radially of the axis, and a rotatable frusto conical cutter mounted on the spade cutter portion adjacent the maximum radial extent of each cutting edge.

Abstract: A rock drill bit for percussive drilling includes a steel body in which six gauge buttons and a single front button are mounted. The gauge buttons are arranged symmetrically and equally spaced about a central axis of the bit. The front button is arranged along the central axis. The front button is of larger diameter than the gauge button. At least three of the gauge buttons are diamond-enhanced, and the front button may be diamond-enhanced.

Abstract: A rotatable cutting bit-chuck assembly wherein the cutting bit has an axially forward end an axially rearward end with at least one cutting insert at the axially forward end. The cutting bit contains a cavity defined by a cavity wall. The chuck has an axially forward end and an axially rearward end. Upon assembling the cutting bit on the chuck, the cavity of the cutting bit receives the axially forward end of the chuck wherein there is a variable resistance retention member between the chuck and the cavity wall.

Abstract: A method for making an earth boring drill bit which includes an outer shell having an external surface adapted to carry cutting elements and a unitary shank and bit core which is fitted into the outer shell. The shell and bit core are threadably engaged with one another or are interferingly engaged. The shell and bit core may be welded, secured with brazing alloys or with high temperature adhesives. In one embodiment, a ridge formed on the shank is received in a groove formed on an interior surface of the shell to prevent relative rotational movement of the shank and shell during drilling. In another embodiment, the shell is formed using matrix infiltration techniques. After the shell is formed, it is heated to braze cutters thereto. While still hot from the brazing process, the shell and shank are fitted together. After cooling the shell contracts to form heat shrink connection between the shell and the shank.

Abstract: A percussion tool includes a housing part having a frontal end provided with an opening; a tool bit guide supported in alignment with the opening; and a tool bit slidably supported in the tool bit guide and projecting from the housing part through the opening. The tool bit is arranged for a reciprocating motion parallel to the longitudinal tool bit axis and transverse excursions substantially perpendicular to the tool bit axis. A transverse guide is attached to the housing part and displaceably receives an outer seal composed of a transverse slide. The transverse slide has an aperture through which the tool bit passes. The transverse slide and the tool bit are arranged such that the transverse slide and the tool bit move as a unit during the transverse excursions of the tool bit. There is further provided an inner seal disposed in the housing part between the transverse slide and the tool bit guide externally thereof.

Abstract: A cutting bit assembly which includes a driven member and a cutting bit detachably connected to the driven member by a retainer. The retainer includes a magnetic pin that removably engages at least one of the cutting bit and the driven member.

Abstract: A make-up system of a down-the-hole hammer. The down-the-hole hammer is of the type comprising a hammer casing (111) having a top sub (112) mounted to one end and a drill bit chuck mounted to the other end. The casing accommodates a piston which is caused to reciprocate within the hammer casing.

Abstract: A bit retention device for a bit and chuck assembly of a down-the-hole, percussive drill, for retaining a head section of a bit should the head section separate from a shank of the bit includes a chuck adapted for threadable connection to a drill casing, a drill bit, a bit retaining shoulder in the the assembly; a wear collar concentric about the chuck and bit and a flexible retaining member removably connected to the assembly, the retaining member extending radially between the wear collar and bit a sufficient distance to contact the retaining shoulder should the bit drop axially downwardly.

Abstract: A method for making an earth boring drill bit which includes an outer shell having an external surface adapted to carry cutting elements and a unitary shank and bit core which is fitted into the outer shell. The shell and bit core are threadably engaged with one another or are interferingly engaged. The shell and bit core may be welded, secured with brazing alloys or with high temperature adhesives. In one embodiment, a ridge formed on the shank is received in a groove formed on an interior surface of the shell to prevent relative rotational movement of the shank and shell during drilling. In another embodiment, the shell is formed using matrix infiltration techniques. After the shell is formed, it is heated to braze cutters thereto. While still hot from the brazing process, the shell and shank are fitted together. After cooling the shell contracts to form heat shrink connection between the shell and the shank.

Abstract: A percussion drill bit includes a drill body having a fluid passage formed therein for conducting flushing fluid to a front drilling face of the drill bit. The fluid passage includes a main portion extending from a rear end of the bit and terminating short of the drilling face, and a plurality of branch lines extending from a front end of the main portion to the drilling face. Front and rear axially spaced seats are disposed in the main portion of the fluid passage. A check valve in the form of a ball is freely movable within the main portion of the fluid passage between contact with the front and rear seats. When the drill bit is oriented upwardly and no flushing fluid is supplied, the ball gravitates rearwardly into sealing contact with the rear seat so that no fluid can flow rearwardly past the rear seat. When flushing fluid is conducted, the flushing fluid pushes the ball forwardly, into non-sealing contact with the front seat and travels past the ball into the branch lines.

Abstract: A hydraulic breaking hammer (10) has a machine housing (11) in which a percussion motor (15) which includes a reciprocatingly movable percussion piston (17) delivers impacts to a breaking tool (13) in the front of the machine housing (11). The machine housing (11) is carried by a surrounding carrier support (18) via intermediate walls (24, 25, 26). The carrier support has the form of a shell (18) which is attached at the rear adjacent connecting devices (19), to a carrier, such as a hydraulic digging machine which aligns the machine housing (11) while the manner (10) is at work. The machine housing (11) is constructed without joints in its axial direction along the length of the housing and includes a guide passage (21) in which a percussion motor (15) is carried, this percussion motor having the form of an insert cartridge which can be clamped from the rear.

Abstract: A method for making an earth boring drill bit which includes an outer shell having an external surface adapted to carry cutting elements and a unitary shank and bit core which is fitted into the outer shell. The shell and bit core are threadably engaged with one another or are interferingly engaged. The shell and bit core may be welded, secured with brazing alloys or with high temperature adhesives. In one embodiment, a ridge formed on the shank is received in a groove formed on an interior surface of the shell to prevent relative rotational movement of the shank and shell during drilling. In another embodiment, the shell is formed using matrix infiltration techniques. After the shell is formed,it is heated to braze cutters thereto. While still hot from the brazing process, the shell and shank are fitted together. After cooling the shell contracts to form heat shrink connection between the shell and the shank.

Abstract: A down-the-hole rock drill includes a top sub, a driver sub having a bore therein, and a piston case extending between and detachably connected to the top sub and the driver sub. A piston is located within the piston case, and a drill device is detachably connected to the driver sub. The drill device includes a shank and a head. The drill device also has a central passageway for a flushing medium. A tube is secured in the central passageway at a free end of the shank. The tube extends beyond the free end of the shank, and the piston has a central piston passageway that receives the tube. The piston is slidably movable relative to the tube. A first portion of the shank located closest to the head has a cross section, normal to a longitudinal center axis of the shank, in the shape of a multi-lobed figure that is continuously non-concave, and the bore of the driver sub is of a matching cross-sectional shape.

Abstract: An apparatus for a percussive, down-hole drill, for positioning a split retaining ring against an internal surface of a drill casing including a chuck with a tapered top surface, a bit bearing with a tapered bottom surface, and a reversible split retaining ring sandwiched therebetween, the split ring having a tapered top and bottom surface, each tapered surface subtending an angle between 5.7 and 25 degrees, as measured from a perpendicular to a drill longitudinal axis, whereby a portion of any longitudinal load on the split ring is developed into a preselected maximum and minimum amount of radial load, to position the split ring in the casing, without damaging the casing.

Abstract: A drag bit for soft, sticky formations is disclosed with a new fluid dynamics control mechanism that minimizes "bit-balling". Multiple blades carrying PDC cutters have tapered back sides to achieve greater velocity through the fluid channels. Multiple jet nozzles in each fluid channel create interacting vortices that produce extremely turbulent flow thereby minimizing the coagulation and deposition of the hydrated clay cuttings on the bit cutting surfaces.

Abstract: The present invention related to a drill bit (10) for rock drilling, preferably a down-the-hole drill bit, said drill bit (10) including a head (11) and a shaft (12), said head (11) defining a cutting face (14) that carries a number of hard material button inserts (15) having end portions extending outwardly of said cutting face (14), means (16,17) for transporting flushing medium from the free end (13) of the shaft (12) to the cutting face (14) of the head (11), said means for transporting flushing medium including a central passage (16) extending from the free end (13) of the shaft (12) and terminating in the head (11) short of the cutting face (14) and at least one branch passage (17) emanating from the central passage (16) and emerging in the cutting facc (14).In the field of down-the-hole drill bits big volumes of flushing medium, normally compressed air, are used since the flushing medium is also activating the down-the-hole hammer.

Abstract: A fluid-activated, percussive, down-the-hole drill having a reversible bearing and bit combination for altering the volume of return reservoir exhaust fluid between a larger amount for deep hole drilling and a smaller amount for shallow hole drilling.

Abstract: A rock drill bit having a shank and a replaceable cutting head, comprising steps of producing a shank having a tip with an outer surface having a given shape, producing a head having a working face at one end and a recess at the other end with a cross-section corresponding in shape to that of said shank tip, and having a size about 0.15% less than that of said shank tip, cooling said shank in a cryogenic gas at ambient pressure to reduce its size, installing said head on said shank tip, and permitting the components to return to ambient temperature, to establish a shrink fit between the head and the shank.

Abstract: A device for forming an undercut in a drill hole includes a drilling tool having a shank receivable in a chuck of a drilling machine and having a convex collar supported on a corresponding concave bearing surface of a bearing element of the device. The bearing element has a bore that communicates the bearing surface with an opening which communicates with a source of a lubricant liquid. The collar has at least one groove for conducting the liquid into the drill hole to the drill bit head of the tool.

Abstract: An earth boring bit having a body provided with a shank having a tubular bore and a head along the opposite end of said body having flow passages communicating with the bore, the head having face portions including a center end face portion, a nose portion, a shoulder portion, and a gage portion along the maximum diameter of the bit, and cutting elements mounted over said face portions having cutting faces oriented in the direction of rotation of the drill bit, the areas of the cutting faces of the cutting elements ranging from a maximum at the center face portion to a minimum at the gage portion of the bit. The cutters may be individually mounted, mounted in groups, arranged in random patterns, and arranged in a variety of other patterns, including radial longitudinal rows circumferentially spaced around the bit face.

Abstract: A rock drill bit for continuous drilling through overburden and rock has a body with end and side surfaces. The drill bit is constructed for rotation in a predetermined direction. The body defines a conduit for compressed air which terminates at a port in the side surface of the body. The port is disposed to open in a direction facing generally away from the predetermined direction of rotation of the drill bit.

Abstract: Device in impact machines. The device comprises a number of rods (6) provided with projections (51). The rods are journalled in a surrounding set of tubes (7) by means of elastic bushings (52,53) which are provided with grooves (57) through which said projections can be passed.

Abstract: The proposed tool comprises a body (1) designed to interact with a percussion-rotary device and a casing (2) shaped as a sleeve. The casing (2) accommodates rock-crushing elements (5, 6) arranged in a manner allowing axial displacement thereof and in the form of concentric rows relative to a working end of the casing (2), the rock-crushing elements having shanks (7, 8) which interact with the body (1). Each rock-crushing element (6) in a peripheral row comprises a spring biased pin mechanism (16) for fixing the rock-crushing element (6) in the casing (2). The casing includes a threaded joint (9) for its axial displacement relative to the body (1). The length of axial displacement of the casing (2) relative to the body (1) is at least equal to the length (H) of the wearable portion of the rock-crushing elements (5, 6).

Abstract: A novel fluid powered rotary percussion drill is disclosed having a small, efficient, fluid energy to impulsive mechanical energy conversion motor and a unique bit arrangement wherein individual independently acting formation disintegration inserts are periodically actuated by the motor at a comparatively high cycle frequency to drill earthen boreholes. Bit drilling structure is renewable by replacing individual inserts and better borehole diameter and bit cutting ability is maintained by rotational gage row inserts. Bottom borehole sensing structure determines drill operational mode.

Abstract: A percussion drilling apparatus for drilling bore holes into subterranean formation in which a plurality of drill rods are arranged in concentric rows in a drill bit housing, each rod having an impact tooth at its lower ends and the rods arranged either to converge inwardly adjacent to the center of the housing or to diverge outwardly at progressively increased angles in each row toward the outermost row. The impact teeth are fired sequentially by concentric combustion chambers arranged above the drill rods and where the pattern and rate of firing can be controlled by cam operated intake and exhaust valves associated with the combustion chambers. The drill bit housing is arranged at the lower end of the drill string with an umbilical cord which carries all necessary cables and lines between the surface controls and the drill bit housing for the purpose of controlling combustion in each chamber and of carrying away the cuttings as the drilling operation proceeds.

Abstract: In a percussion drilling tool, a bit is connected to a drill motor through a mating spline connection. External splines on the bit engage internal splines in the drill motor and have respective load bearing faces disposed in a plane extending radially outwardly from central axes. The splines also include a crest land, and a root land. When the splines are in an abutting centered position, there is a uniform radially measured outer clearance between the external spline crests and the internal spline roots, and a uniform radially measured inner clearance between the external spline roots and the internal spline crests. The outer clearance is less than the inner clearance to prevent abrasive damage below the root diameter of the bit resulting from axial relative movement so that the external spline crests will engage the associated internal spline roots while continually maintaining a spacing between the external spline roots and the internal spline crests.

Abstract: A drill bit has a cylindrical main body, a formation cutting face at the lower end of the body, and means by which the upper end of the bit can be connected into a drill string. A drilling fluid flow passageway extends axially through the main body and provides flow of drilling fluid to the drilling face. The passageway contains flow restrictions for balancing the flow of drilling fluid onto the bit face. The restrictors contain diffusing stages for reducing the velocity of the drilling fluid. Flow isolating paths are formed on the bit face to prevent diversion or channeling of fluid flow on the bit face.

Abstract: Percussion drill bit for rock perforators is provided whose frontal face is covered by a plurality of hard-metal studs, whereby a plurality of studs are positioned to form a group, there being several of these groups present and each of the so-called groups being at a distance from one another at least circumferentially and separated through circulation-medium channels, and further provided with at least one axial center channel located roughly in a center of the frontal face and opening into the circulation-medium channels, characterized in that each group consists of only one row of studs (1) arranged on sloped protruding drilling facets (4), in that the drilling facets (4) run against the rotation direction (A) of the drill bit, at an angle with respect to the radius, and in that the circulation-medium channels (2) formed in the frontal face widen starting from the center of the drill bit, radially towards the outside.

Abstract: In a percussive tool in which a very high pressure and preferably cavitating water jet is directed through an opening in the working surface of the tool, the jet is formed by a nozzle positioned in a cavity behind the opening and decoupled from the tool by a bearing layer of water from the jet. A supply pipe extends rearwardly of the nozzle without contacting the tool, and is supported externally of the tool, on a machine which operates the tool, by a support which allows the fluid bearing to center the nozzle within the cavity while restraining movement of the nozzle axially of the tool.

Abstract: A rotary drill bit comprises a bit body having a leading face and a gauge region, a number of blades on the leading face of the bit body, and a number of cutting elements mounted along each blade. A passage in the bit body supplies drilling fluid to nozzles in the leading face of the bit body for cooling and cleaning the cutting elements. Each nozzle is so oriented, and the surface of the bit body in the region in front of each blade is so shaped, as to promote a vortex flow of drilling fluid around said region, with part of the periphery of the vortex extending across the cutting elements on the blade, so that fluid in the periphery of the vortex passes across the cutting elements mounted on each blade before escaping through an exit channel in the gauge region.

Abstract: Disclosed is a new method of construction for multiple or gang down hole rock drills. A rigid mounting cylinder with alignment and securing means for the individual drills is provided. The cylinder further serves to attach the multiple drills to a single drill string which supplies air to the individual drills. The cylinder further facilitates rock chip removal by filling all but the peripheral annulus which forms the exit channel for exhaust air.

Abstract: An annular air hammer apparatus for drilling wells has a cylindrical body which accommodates a stepped annular hammer mounted for reciprocations. A stepped air distribution tube is rigidly secured in the body and has inlet ports and exhaust ports, the tube cooperating with the hammer and defining therewith a work stroke chamber and defining a return stroke chamber with the body. A pipe for receiving drillings is stationary mounted in the air distribution tube and defines therewith a plenum. An annular member is provided between the pipe for receiving drillings and air distribution pipe, in the zone between the inlet and exhaust ports, to define an exhaust chamber between the pipe for receiving drillings and air distribution tube. The plenum and exhaust chamber permanently communicate with each other through a throttle means.

Abstract: A percussion drilling tool assembly is provided which operates under fluid pressure to reciproce a hammer, the hammer is disposed in a barrel assembly and operates to strike an anvil bit shank to cause the bit to thereby penetrate a rock substrate material. A central fluid passage through the drill stem of the assembly and through the reciprocating hammer allows a flushing fluid to be used with the drilling assembly to flush cuttings from the hole up and around the drill stem simultaneously with and separate from the fluid operating system for reciprocating the hammer. The drill stem includes intake and exhaust passages for pressured working fluid as well as a mud passage for the flushing fluid or mud, the drill stem is made up in sections connected to form a string which extends the length of the hole and provide the pressured working fluid and mud to the pneumatic tool connected at the end of the drill stem.

Abstract: A matrix bit is shown of the type having a metallic mandrel with a connecting end for connection in a well pipe string leading to the well surface. An opposite end is covered with a cast matrix material which defines a central bit body. A plurality of integral blades are formed of the cast matrix material and extend axially and radially from the central bit body. Each of the blades is reinforced by a metallic extension which is contained within the matrix material and extends coaxially with each blade.

Abstract: A borehole excavation apparatus and method which employs a down-hole positive displacement pump to circulate the drilling fluid and lift the excavated rock to the surface through nonmetallic composite pipe. The excavation of rock occurs by use of apparatus which produces a combination of percussion impact, cavitation, and hydrostatic depressuring which utilizes the pore pressure and elastic energy stored within the rock to fracture the rock into small pieces. The down-hole positive displacement pump and the excavation tool are actuated by the axial oscillation of a weighted momentum unit which in turn is actuated by the axial oscillation of the nonmetallic composite pipe, which in turn is actuated by the oscillating motion of a rocker beam at the surface where the drilling fluid and excavated rock particles are discharged.

Abstract: A rock drill for percussion drilling comprises frontal and gauge button inserts, said frontal button inserts being parallel with the longitudinal axis of the rock drill and said gauge button inserts being inclined at an angle relative to said longitudinal axis and arranged to define the diameter of the hole drilled by the rock drill. The number of the frontal button inserts is two and the number of gauge button inserts is two.

Abstract: Disclosed is a single-pass notching and drilling tool. The tool comprises an adaptor having a first threaded end for coupling with a power source, an opposed second threaded end, an enlarged diameter portion adjacent to the first threaded end and having a first abutment face and a mediate portion adjacent to the first axial abutment face and adjacent to the second threaded end. There is also a drill portion joined to the second threaded end of the adaptor and having a second axial abutment face. The tool further comprises a notching tool comprising a body having a central bore rotatably engaging the mediate portion of the adaptor. The notching tool is freely rotatable about the mediate portion independent of the rotation of the adaptor. The axial movement of the notching tool is bounded by the first and second axial abutment faces. Disclosed also is a method of drilling a blast hole with the single-pass notching and drilling tool.

Abstract: A tool assembly in which the tool holder 6 forms a relatively small volume of metal thereby facilitating brazing of the tool bits (21, 23) and inexpensive replacement.