Abstract: A deformed sleeve for mounting a cutting tool in a bit holder has one end shaped as an ellipse. The deformation is done by the application of pressure before heat treating. No further machining is necessary after the heat treatment. The deformed sleeve is force-fitted into a bore in a bit holder and is retained therein in a non-rotating manner by friction.

Abstract: A mobile mining machine for cutting a tunnel in rock has a wheel-like cutterhead assembly supported by a pitch boom assembly that causes movement of the cutterhead assembly in the vertical plane. A swing boom assembly supports the pitch boom assembly and is supported by the main frame of the mobile mining machine. In one embodiment the swing boom assembly has a pivot axis that is tilted from vertical and swings the cutterhead and the pitch boom during mining to cut a tunnel having a wide, flat floor. During mining, a gripper assembly having a floor gripper shoe and a roof gripper shoe brace the mobile mining machine in the tunnel. Thrust is provided by thrust cylinders located between the gripper shoes and the main beam. Extension of the thrust cylinders moves the cutterhead assembly, main beam, and rear portion of the mobile mining machine forward relative to the gripper assembly due to slidable engagement of the main beam and gripper assembly.

Abstract: Mining apparatus in which a cutting wheel supporting a plurality of roller-cutters rotates about a horizontal axis and is supported on a slewing boom for cutting a tunnel with a flat floor and roof and elliptical walls as it slews across a mining face. The slewing boom is supported on a main beam assembly, the front end of which rests on powered crawler tracks and the rear end of which passes through a gripper assembly which may be clamped between the floor and roof of the tunnel, and against which the main beam assembly may be urged forward for engaging the roller-cutters with the mining face. A preload crawler is urged against the roof of the tunnel above the powered crawler tracks to locate the main beam assembly rigidly relative to the tunnel such that the roller-cutters may cut the rock in the mining face with minimal loss of cutting force due to vibration.

Abstract: A mining apparatus for working a horizontally and longitudinally extending seam having a vertical face has a longitudinal row of walking props extending along the face and each having a roof-engaging cap, a floor-engaging foot, and a jack vertically interconnecting the respective cap and foot and expansible to press the cap up and foot down. Upper and lower long-wall mining machines each having a predetermined height substantially less than the distance between the mine roof and floor are each provided with a cutter for working the face and a longitudinal conveyor for carrying off material cut from the face. The upper machine is suspended from the caps well above the floor level and the lower machine is carried on the feet of the promps below the caps thereof generally at floor level and spaced back towards the props from the props so that the upper machine moves on a step above the lower machine and the two machines can simultaneously work the seam at respective vertically and horizontally offset levels.

Abstract: The present invention is applicable to a shield tunneling method and a tunneling machine therefor which excavate a deformed section by rotating a plurality of circular cutters. There is provided a deformed shield tunneling method and a tunneling machine therefor which excavate a tunnel surface by rotating a plurality of circular cutters (4), (5) and (6) arranged in the front of a front casing (2) of a tunneling machine (1) and which cut soil in tangent portions (15a), (15b) and (15c) of circles formed between said circular cutters by rocking rocking cutters (17) attached opposite to the tangent portions in order to continue excavation while completely forming a predetermined deformed section in excavation of any combination of circular cutters regardless of the diameter of the circular cutters.

Abstract: A method of steering a double-ended ranging drum mining machine includes the steps of positioning two previous cut roof followers spaced apart longitudinally of the machine, measuring machine tilt using a second means, estimating coal thickness using third means and generating algorithms therefrom whereby height differences between points on the current and previous cut roof can be calculated to control and steer the leading and trailing drums the algorithms being generated in such a manner that cumulative errors along or towards the face are minimized or eliminated.

Abstract: A self propelled continuous mining machine includes a mobile frame assembly having a first pivot point for a boom assembly or an end of a piston cylinder assembly and a second pivot point for pivotally connecting an end of a piston cylinder assembly or pivotally connecting an end portion of a lever member which may be interchangeably utilized to provide the continuous mining machine with boom assemblies of different cutting heights. The first pivot point is located at an elevation higher than the elevation of the second pivot point. This arrangement of interchangeable boom pivot points permits for low and high cutting height boom assemblies to be utilized with the same continuous mining machine.

Abstract: A method of recovering methane from a solid carbonaceous subterranean formation by injecting a fluid that desorbs methane through at least one injection well into a subterranean formation and recovering desorbed methane through at least one production well. The initial rate of injection of the desorbing fluid can be increased without exceeding formation pressure limitations by injecting a preflush fluid having a desorbing efficiency less than a desorbing efficiency of the first fluid. This increase in injection of the desorbing fluid results in an increase in the recovery rate of methane.

Abstract: A low velocity, high mass ram is connected to the cutting tool. The cutting tool has an array of impact forward and side buttons or bars which form chip-forming spaces there between. The side buttons or bars advantageously cut a gage in the slot. A method of slot kerfing which cuts the kerf on an angle.

Abstract: For narrow ore mining, shrinkage stopping is used with working equipment, such as a working platform or mining rig (30), which is suspended in guide sections (38) in the roof of the mining chamber, and from which drilling and charging is carried through, the mining chamber communicating with a raise. In the raise, which follows the inclination of the ore body, a transport lift is used designed for receiving the working platform or mining rig (30) in its lift cage (20). The lift cage (20) comprises a transport guide arranged for suspension of the working platform or the mining rig in the lift cage and connectable to a start guide in the roof of the mining chamber.

Abstract: A mining system comprises a laterally deflectable segmented conveyor extending longitudinally along a longitudinal face from which material is to be cut, a mining machine displaceable longitudinally along the conveyor and engageable with the face to cut material therefrom and deposit in the conveyor, and a longitudinal succession of support frames each having a respective actuator connected to a respective segment of the conveyor and each also having a respective a respective retractile roof-engaging flap. The process of this invention comprises bracing the frames and conveyor in a safety zone immediately adjacent the mining machine against the roof with their flaps retracted. The machine is advanced in the safety zone while cutting the face in the safety zone, and the flaps of the frames in a zone immediately downstream of the safety zone are sequentially retracted and the flaps of the frames in a zone upstream of the safety zone are sequentially advanced.

Abstract: Coal is mined using water jets to a remove a layer of thin horizontal slices of coal. The thickness of the layer is sufficiently small that elastic deformation of the roof of the layer due to settling will cause the roof to rest against the floor of the layer. A number of additional layers of slices are then extracted in the same manner, each immediately below the floor of the preceding layer. The thickness and location of these layers wiht respect to previous layers is such that elastic deformation of the roof of the first layer due to settling will cause the roof to rest against the floor of the last layer of slices. Through the sequential mining of layers in this manner from top to bottom, the entire seam of coal is extracted and the mine roof rests upon the mine floor without the need for artificial roof support.

Abstract: A method is provided for restoring a refractory lining for repeated use. The lining is present on a underlying wall surface and is still hot from a previous use when one induces thermal shock in the lining (e.g. by spraying water on it) so as to loosen it. The loosened pieces are then pried away from the wall surface, and they are removed from the area. The residual lining is milled to expose a sound, underlying wall surface, and fine particles, dust, and milled-off pieces are removed. The underlying wall surfaces are thus made speedily available for relining and reuse.

Abstract: An accessory for the boom of road working equipment has a frame arranged for attachment to the boom. The accessory also has a shaft rotatably mounted in the frame. Also included is a motor mounted on the frame for rotating the shaft. The accessory employs a rotary tool mounted on the shaft.

Abstract: A method for preventing the formation of acidic mine water wherein inert gas in introduced into a mine cavity under positive pressure to displace oxygen contained therein. Upon detection of the displacement of substantially all of the oxygen from within the mine cavity, the mine cavity is permitted to flood and seal with water.

Abstract: A cutter-type apparatus is mounted on a tractor for positioning and locomotion to remove coatings from planar supporting surfaces of concrete, steel or similar materials. The apparatus defines a cutter that is variably positionable from horizontal to vertical to remove coatings from surfaces oriented in such directions. The cutter provides a plurality of spaced spirally arrayed teeth, of particular configuration, arrayed on a powdered cylinder to remove surface coatings substantially by cutting and to leave the original supporting surface substantially intact. A cover aids in preventing injury or damage from access to the cutter and, in association with a water spray system, aids in preventing overheating of the cutter and in collecting and containing debris.

Abstract: A roadway milling machine includes a hollow, cylindrically walled, shaft mounted, imperforate drum having tungsten carbide tipped steel cutting tools supported in tool holders extending generally radially outwardly from the cylindrical surface of the drum. The drum is moved over a roadway to be milled, and is rotated on its shaft to bring the cutting tools into operative contact with the roadway. Water is fed into the drum along a water access opening provided along the axis of the drum shaft; and this coolant leaves the drum through openings provided in the cylindrical drum wall, one adjacent to each cutting tool, in position where the coolant leaving the drum will impinge upon and cool its adjacent cutting tool. In order to limit the flow of water from the drum to the cutting tools and, at the same time, to prevent the necessarily small openings from clogging up, large openings can be provided through the cylindrical drum wall and well into the tool holders which extend integrally outwardly from that wall.

Abstract: An accessory for the boom of road working equipment has a frame arranged for attachment to the boom. The accessory also has a shaft rotatably mounted in the frame. Also included is a motor mounted on the frame for rotating the shaft. The accessory employs a rotary tool mounted on the shaft.

Abstract: A vibration damper for a road planer and the like with a main frame and a sub-frame movably connected thereto. A prime mover and a tool are mounted on the sub-frame, which includes frame members forming compartments adapted to receive lead shot particles therein. The particles absorb vibrational energy from the prime mover and the tool. A method of damping vibration is disclosed wherein vibrational energy is transmitted to the lead shot particles which vibrate and generate heat. The heat is dissipated through the frame members to the atmosphere.

Abstract: A method for drilling a hole in a hard material such as rock. According to this method, the rock is fragmented by impact along spaced-apart, parallel paths while it is simultaneous fragmented by shear between these paths. An apparatus for carrying out this method is also disclosed.

Abstract: An improved cutting head for a mining machine having a rotary cutting head and shaft removably and rotatably attached to the forward end of a mining machine such that the shaft and cutting head alone may be removed from the forward end of the machine and repaired at the site where the mining is taking place.

Abstract: A method for reducing compressed air losses when driving underground cavities which are supported by compressed air. The part of the inner cavity face exposed by mining is sealed by a viscous medium after breaking away the earth. With a supply of propellant, the viscous medium is applied, in the form of a spray mist which is directed toward the exposed part of the inner cavity face, in such a way that the mist penetrates the substratum without substantially destroying the exposed face. Particles of rock are thus prevented from being detached from the face which is to be sealed.

Abstract: A solar powered cutting, shaping, and polishing device is disclosed. In the preferred embodiment a large concave parabolic reflector is mounted on an X and Y axis rotatable (telescope type) mount and directed towards the sun. A smaller convex parabolic reflector is mounted on an adjustable support structure attached to the large concave reflector such that the two reflectors can be made to share, or nearly share, the same focal point. Mounted between the large and small parabolic reflectors on an additional rotatable mount is a flat reflector. The large and small parabolic reflectors are used to concentrate solar energy to a desired and adjustable focal point. The flat reflector can then be used to direct the concentrated energy across a material in an operator-determined pattern. Depending on certain factors associated with the material and the positioning of the focal point, the material can then be cut, shaped, or polished as the user desires.

Abstract: A method and apparatus for laterally severing an asphalt layer to form a ribbon, separating the asphalt ribbon from an underlying base, elevating the separated asphalt ribbon, and fracturing the elevated asphalt ribbon by bending same. A cutting member having a leading edge which is insertable between the asphalt ribbon and base provides separation thereof along a lateral line. A ramp and elevating structure elevatingly guide the separated asphalt ribbon into a pair of breaker drums which are rotatable in opposite circumferential directions. Each breaker drum has protruding teeth which are arranged in laterally separated circumferential rows with the teeth in adjacent circumferential rows being preferably arcuately offset. Corresponding circumferential rows on the opposed breaker drums are laterally aligned and the teeth in those rows engage opposite surfaces of the asphalt ribbon during rotation of the breaker drums.

Abstract: A first mobile mining machine for cutting mining tunnels in hard rock, which includes a horizontally swinging wheel-like cutterhead assembly mounted on a crawler and base frame assembly. The cutterhead assembly consists of a transverse horizontal axis wheel-like drum on which are multiple peripherally mounted rolling cutter units.A second mobile mining machine for cutting mining tunnels in hard rock, which includes a horizontally swinging and vertically ranging wheel-like cutterhead assembly mounted on a crawler and base frame assembly. The cutterhead assembly consists of a transverse horizontal axis wheel-like drum on which are multiple peripherally mounted rolling cutter units.

Abstract: A method and apparatus are disclosed for grinding out a crack in pavement in preparation for filling the crack. A narrow groove is formed in the pavement following the crack by a single grooving blade having a first thickness. The single grooving blade is replaced with a second grooving blade assembly having a thickness greater than the single grooving blade, and the second grooving blade assembly is moved along the groove and with the second grooving blade assembly engaging opposite edges of the groove and for forming upwardly outwardly sloping sidewalls.

Abstract: Process for sorting coarse to fine materials according to their chemical composition, in which samples are taken and analyzed, and in which the transporting and/or further processing of the materials is controlled according to the results of the analysis. The samples are taken in the form of an air swirled mixture of coarse dust and fine dust (i.e., particles with grain sizes of less than 200 .mu.m) which is obtained as a by-product or is produced artificially. The coarser dust is separated from the mixture. All of the fine dust or a fraction thereof is analyzed.

Abstract: A granular fertilizer and insecticide carrier-filler material which is produced from phosphatic clays is disclosed along with its method of production. The granular carrier-filler material is water-degradable, and is prepared from waste phosphatic clays by tilling the source material, allowing it to dry, crushing the dried material into granules, heating the granules at a temperature of about 450.degree. F. to less than 1600.degree. F. to obtain a granular carrier-filler material having a moisture content of no more than about 15% by weight. Depending upon end use applications, the granular carrier-filler material may be sized as by screening.

Abstract: For sinking of shafts, a cutting machine (1) is provided having its cutting arm (3) pivotable around a vertical axis (4) and a horizontal axis (5). The cutting arm (3) carries cutting heads (14) which are rotatable around an axis (15) horizontally arranged and extending perpendicularly relative to the axis of the cutting arm. The shaft is now sunk around its circumference (9) in direction of its axis (10), for which purpose first the uppermost lead of a screw surface is prepared. On this uppermost lead of the screw surface the cutting machine is advanced until the cutting heads (14) contact the shaft wall (9). In the following, a floor cut (19) is made whereupon a further floor cut (20) is made at a lower level. Starting from a corresponding position of the cutting machine surfaces (23, 24) are cut free starting from the shaft wall (9).

Abstract: Disclosed herein is a new method and improved apparatus for digging and mining earth formations, especially coal formations. A mining or excavating machine having a movable frame with a drive means mounted on the frame is provided with a rotatable structural member and a rotatable cutter support having cutter bits mounted thereon. The structural member is rotatably mounted on the frame and connected to the drive means so as to be driven in one direction of rotation about a longitudinal axis of the structural member. The rotatable cutter support assembly with the cutter bits mounted thereon is rotatably mounted on the structural member and is freely rotatable about its longitudinal axis. The mining machine is then positioned so that the cutter bits will reduce the mineral formation by driving the structural member in one direction of rotation about its longitudinal axis.

Abstract: An improvement in a method for communicating the surface and a subterranean coal seam via a borehole positioned to provide access for the positioning of power transmission and fluid transmission lines from the seam to the surface, the improvement comprising; extending a portion of the borehole beneath the seam, casing at least a portion of the extension of the borehole and thereafter pumping water from the borehole extension.

Abstract: A compact and relatively lightweight rock cutting tool comprises a pair of disc cutters disposed in parallel, the disc cutters having circumferential cutting edges; a support member for the cutters disposed radially inwardly of the cutting edges thereof and on which each cutter is borne for rotation; and a mounting pedestal to which the member is attached between planes defined by the respective cutting edges of the cutters, preferably mid-way between the planes. Preferably each cutter is borne for rotation independently of the other and the cutting edges of the disc cutters are separated by 80 to 100 mm. The overall width of a tool with a separation of 90 mm between the cutting edges and with cutters of 330 mm diameter is only 180 mm which is about half that of an equivalent tool of conventional construction. With the tool of the invention therefore either more tools may be fitted to a given cutting head or more room made available at the cutting head for access to the tools and for the removal of cut rock.

Abstract: In digging and hauling soil, rocks, minerals and the like by the use of a dragline the invention provides a novel combination of said dragline, a conveyor for hauling the materials dug, and a hopper disposed over and movable along the conveyor whereby material may be efficiently excavated and transported out of the working area.

Abstract: A method for drying, curing and mining bentonite clay in a clay pit wherein that overburden of non-clay material which may exist is removed and the surface of the bentonite ore body is tilled to loosen or break up a tier of the bentonite to expose it to the natural drying and curing effects of the atmosphere, the dried and cured tier of bentonite is removed thus exposing another tier of uncured bentonite, which is again tilled for drying and curing, and the process is repeated until the bentonite ore body is exhausted.

Abstract: An improved mining apparatus for excavating material, such as coal, for example, from an earth formation, such as a coal seam, for example, wherein a miner, having a forward and a rearward cutter, is guided through the coal seam and excavates a borehole therein, the borehole being filled with a working fluid during the operation of the miner, the working fluid facilitating the operation of the miner and providing a vehicle for removing the mined material. Substantially all of the operations of the miner are controlled from the earth's surface thereby eliminating the necessity and accompanying hazards and costs involved in utilizing personnel underground during the mining operations.

Abstract: A retainer clip for tool bits comprises an annular strip having circumferentially spaced ends defining a gap therebetween. A pair of proximate projections and at least one remote projection project outwardly from the strip. The proximate projections are located on opposite sides of the gap. The proximate projections include positively oriented front surfaces, and the remote projection includes a non-positively oriented front surface disposed longitudinally rearwardly relative to forwardmost portions of the front surfaces of the proximate projections. Upon forward displacement of the clip within the hole of a holder, contact occurs between the proximate projections and a wall of a retaining groove of the holder to produce radial shifting of the gap of the clip toward the axis of the bit. Removal of the bit from the hole is possible only by shearing the remote projection.

Abstract: A machine for cutting a slot in hard rock uses a percussive drill to slot the rock, the drill being so mounted that the tool has an obtuse angle to the base of the slot in the direction of advance, which angle is for optimum effect between 120.degree. and 145.degree. and preferably between 130.degree. and 140.degree.. The drill is oscillated and cuts on the forward stroke and free wheels on the return stroke. The drill may be adjusted to vary the angle and the angle of inclination to the horizontal.

Abstract: Apparatus for and method of controlling the mining by a mining machine of a seam of material (e.g., coal) overlying or underlying a stratum of undesired material (e.g., clay) to reduce the quantity of undesired material mined with the desired material, the machine comprising a cutter movable up and down and adapted to cut down into a seam of coal on being lowered. The control apparatus comprises a first electrical signal constituting a slow-down signal adapted to be automatically operated to signal when the cutter has cut down into a seam of desired material generally to a predetermined depth short of the interface between the seam and the underlying stratum for slowing down the cutting rate as the cutter approaches the interface, and a second electrical signal adapted to be automatically operated subsequent to the first signal for signalling when the cutter has cut down through the seam to the interface for stopping the cutting operation, thereby to avoid mining undesired material with the desired material.

Abstract: An apparatus for winning material in a mineral mining working utilizes a mineral mining plough which is movable to and fro alongside a conveyor. The plough is provided with first cutter means arranged to win material lying in a first height range, and second cutter means arranged to win material lying in a second height range. The plough is driven on the downhill run with the cutter means so positioned that material is won to a greater depth over the first height range than over the second height range. The plough is then driven on the uphill run with the cutter means so positioned that material is won to a smaller depth over the first height range than over the second height range.

Abstract: A method for loosening stony soil by means of a rotating cutting head fastened to the rear of a tractor and having cutting members to be drawn through the soil and being mounted according to a helical line.Stony soil can be readily loosened to the desired depth because the cutting head can be kept at an acute angle to the direction of movement. So the cutting head is drawn in a stable manner in the direction to the tractor against the stone surface concerned and penetrates the stony soil like a plough, the soil above the cutting head being torn up upwardly.

Abstract: A stopping apparatus is suspended in a pilot shaft and blasting charge holes are drilled outwardly and downwardly from successive vertical positions from the bottom to the top of the pilot shaft to provide a circular array of holes fanned-out from each vertical position. The blasting charge holes are loaded with blasting charges, and detonated, proceeding from the bottom to the top of the pilot shaft.

Abstract: In a method and apparatus for cutting minerals utilizing a cutting tool provided with cutting teeth, the tool rotates about an axis approximately parallel to the winning face and is moved at a feeding rate essentially in axial direction. Several grooves spaced from each other are carved in sequence, and in dependence on the mineral properties the feeding rate is increased with respect to the rotatory velocity when a brittle mineral is to be cut, while the feeding rate is diminished with a tough mineral.

Abstract: A method of breaking hard compact material such as rock adjacent a hole drilled thereinto and an apparatus for performing the method are described. Two forces contribute to efficiently breaking the rock: a force for firmly gripping a region of material adjacent the hole and an axial outwardly directed force. When breaking the material the force for firmly gripping the material is unidirectional with but separate from the axial outwardly directed force. To generate these forces wedge means and sleeve means of the apparatus are inserted into the hole and an axial outwardly directed thrust is exerted on the sleeve means by means of cooperating sliding wedge surfaces of the wedge means and sleeve means which converge towards the apparatus power means. This power means as well as the thrust transmitting means for transferring the reaction force are situated outside the hole.

Abstract: A cutting-chipping system comprising an interconnected triaxial array of rotating drums each mounted for independent rotation. Each drum includes a plurality of spaced, outwardly extending teeth to sequentially cut, chip and break particulate mass such as coal or ice engaged by the system. The drums are oriented with no axis of drum rotation parallel to another and in a configuration wherein the direction of cutter travel from one drum is oblique to that of a second drum. In this manner, particulate matter engaged by the system is initially cut and chipped by a first drum to form a series of protuberances and/or weakened sections which, when struck at an oblique angle by a second drum, will chip and break away. The teeth may be comprised of picks, chisels or combinations thereof constructed and adapted for bidirectional rotation. The system may be adapted for applications upon land vehicles, water crafts, floating platforms, and the like.

Abstract: A method of mining utilizing a reciprocating drive, in which a tooth is driven along a relatively straight path over an ore surface in one direction of movement so as to cut a groove therein, and then a wheel is substituted in place of the tooth and is rolled within the groove in the opposite direction, the wheel having a radially wedge-shaped circumferential edge portion which applies laterally outward and downward crumbling forces to the groove walls.Both the tooth and the wheel may be incorporated into a unitary wheel assembly as a single tool, by attaching the tooth to a point on the circumference of the wheel. The tool is then locked against rotation during its powered drive stroke in one direction, when the tooth engages the groove, but during its stroke in the other direction is released to permit rotation of the wheel.The method provides for working a number of parallel grooves concurrently, with wheels being utilized only in alternate ones of the grooves.

Abstract: A percussion drill bit has an anvil portion and a removable head porton incorporating cutting inserts arranged in circumferentially-spaced groups separated by fluid flow passageways, at least some of the inserts being arranged at axial and radial positions with respect to the drill axis so that during working operation these inserts penetrate the formation being drilled by generally equal amounts and are thus subject to generally the same loading. The removable head portion is retained on the anvil portion of the bit by a splined and threaded lock nut arranged so that the threads are not subjected to cyclical fatigue loading due to operation of the percussion force generating tool.

Abstract: A method of operating a machine having a constant depth linear cutting head which is retrofitted to a continuous mining machine replacing the rotary head. By altering the usual configuration of the cutting head from the high speed rotating type with a large number of bits, as is currently being used, to one employing a non-rotary type head with 10 percent or less of the usual number of bits, and also operating a combined sumping and shearing action without the bits exiting the coal face being cut, less respirable dust is produced at the mine face. In addition to decreasing the dust and amount of menthane gas - when coal is mined - which is liberated, our method also produces more coal on the average for each cut in the mine face by deeper constant depth cuts in the 3- to 6-inch range by first sumping into the mine face and then shearing the face, without withdrawing or rotating the point attack bits.

Abstract: A tool body defines an axis of rotation for the tool and has a periphery surrounding said axis. A plurality of cutter bits are carried by said body and protrude substantially radially from said periphery and have free ends. Said cutter bits are arranged in a plurality of groups which are spaced in the direction of said axis. The free ends of the cutter bits of each of said groups define a circle. The circles defined by the free ends of the cutter bits of said groups increase in diameter in one direction along said axis.

Abstract: A percussion drill bit has an anvil portion and a removable head portion incorporating cutting inserts arranged in circumferentially-spaced groups separated by fluid flow passageways, at least some of the inserts being arranged at axial and radial positions with respect to the drill axis so that during working operation these inserts penetrate the formation being drilled by generally equal amounts and are thus subject to generally the same loading. The removable head portion is retained on the anvil portion of the bit by a splined and threaded lock nut arranged so that the threads are not subjected to cyclical fatigue loading due to operation of the percussion force generating tool.

Abstract: A mining cutter comprises a plurality of holders mounted on a tool support, and a cutting element mounted in a socket of each holder. The tool support is driven such that the cutting elements are alternately moved into cutting and non-cutting modes relative to an earth formation. A retainer rotatably retains each cutting element in its associated socket for limited longitudinal forward movement relative to the holder toward the non-cutting mode and limited longitudinal rearward movement toward the cutting mode. Each cutting element and holder includes mutually engageable surfaces for preventing rotation of the cutting element in the cutting mode while permitting rotation of the cutting element in the non-cutting mode. The arrangement may be such that rotary movement of the cutter element is induced as the cutter element travels toward its cutting mode and/or toward its non-cutting mode.