Abstract: The invention comprises an Accessory for use with a driver for forceably inserting friction rock stabilizers into bores formed in earth structures (such as mine roofs). In the depicted embodiments, the Accessory comprises an elongate body having a driver element with a pin or boss at one, lower, "driven" end of the body for engaging and supporting an end of a stabilizer, and a second driver element with a socket, at the opposite, upper, "driving" end of the body for receiving an insertion tool. The latter driver element can be pivotably offset, to accommodate an angled, unobstructed address of the insertion tool to the upper end of the body, and to enable a linear insertion of a stabilizer, supported on the lower end of the body, into a bore.

Abstract: A hammer for driving piles comprises an anvil adapted to rest on top of a pile to be driven and a weight arranged to travel through a stroke between an upper position and a lower position. At least one flexible member interconnects the anvil and weight in such a way that when the weight travels to its lower position the flexible member is in tension and prevents the weight striking the anvil. The tension in the flexible member transfers the energy of the weight in a progressive fashion to the anvil.

Abstract: In an hydraulic rock drill there is an hydraulic so called recoil damper that damps the reflected shock waves that propagates from the rock backwardly through the drill stem. The damper comprises a support piston (68) slidably in a cylinder so that a pressure chamber (20) is formed in which the support piston has a piston area. Narrow clearances (75,76) between the support (68) and its cylinder form leak passages and these leak passages are coupled in series with an orifice restrictor (84) to sump. The pressure peaks in the pressure chamber do not reach sealing rings located at the outer portions of the clearances.

Abstract: An improved pile driving cap block cushion is the subject of this invention. The material is a glass filled thermoplastic characterized by a melting point of 125.degree. C. or higher, a secant modulus of elasticity of from 50,000 to 800,000 p.s.i. and a coefficient of restitution of from 0.4 to 0.9. A number of thermoplastics are suitable for forming the material of the invention and include polyamides, polyesters, polyolefins, polycarbonates, polyimides, polyamide-imide copolymers, acetal homopolymers, acetal copolymers, fluoroplastics, polyphenyl oxides, copolyesters, polyetherimides, polystyrenes, polyvinyls, and polysulfones. A particularly useful group of materials is poly(ethylene terephthalate), poly(butylene terephthalate) nylon 6 and nylon 66. Additives such as antioxidants, heat stabilizers, reinforcers and colorants may also be added.

Abstract: A hand-held motor-driven percussion tool comprises a piston driven over an air cushion and acting over an axially movable anvil on the inner end of a tool axially movable in a tool receiver provided at one end of a tool housing. The anvil has an annular collar located in the cavity of an impact body which is movable in the direction of the impact of the piston against a cushioning ring. The impact body has an abutment face adapted to be engaged by a collar of the anvil when the latter is driven by the piston. A face of the impact body facing away from the cushioning ring is directed toward a part fixedly connected with the tool housing. The mass of the impact body is for instance 10% greater than that of the anvil. If the tool during operation is withdrawn from a workpiece, then the flange of the anvil impinges upon the abutment face of the impact body and accelerates the latter towards the cushioning ring.

Abstract: A force-transmitting a drive caps is interposable between a pile driver hammer and a pile to be driven. This cap is formed with an upwardly open cylinder which is of smaller area than the striking face of the hammer. A piston is vertically reciprocal in this cylinder and has an upper surface which is engageable with the striking face of the hammer. The chamber below the piston in the drive cap contains a body of liquid and a body of gas. The gas is pressurized so as to urge the piston into a raised position extending upwardly from the upper face of the drive cap. The piston and hammer are dimensioned so that the hammer first strikes the piston, driving it downwardly in the cylinder, and thereafter strikes the upper surface of the drive cap. The gas body may be held in a separate container within the chamber in te drive cap and the pressure of the gas body is established by the amount of liquid in this chamber.

Abstract: A ram head for self-driven pneumatic ram drills for producing boreholes in the earth, having a generally tubular housing within which there is movable axially back and forth an impact piston whose impact energy can be transmitted to the ram head arranged at the front end of the housing. In order on the one hand, to crush obstacles by high energy and, on the other hand, to avoid too strong a compacting of small particles of earth in front of the apparatus and in addition make it possible to drive pipes, the generally conical ram head is provided with a central axial bore within which an impact bolt is mounted for longitudinal displacement between two end positions which are limited by stops, at the front end position of which supported by a spring the impingement surface of the impact bolt for the impact piston lies within the anvil surface of the ram head and at the rear end position of which the impingement surface projects from the anvil surface in the direction towards the impact piston.

Abstract: An attachment for driving pipe wherein a plurality of concentric sleeves having diminishing diameters are arranged in driving engagement with a pipe end with a driving hammer operating to impart a driving force to the pipe, the sleeves being arranged to form a generally concial configuration such that the sleeves are in contact with each other at points which lie along lines of contact intersecting at the axis of the driving hammer to form an acute included angle.

Abstract: A pile driving device of the drop hammer variety is disclosed and includes a crane supportable housing containing a hydraulic drive motor and a cam member for executing generally circular motion within the housing in response to operation of the drive motor and a ram depending from the housing of a substantial mass and having a bearing plate selectively engageable by the cam with cam motion sequentially raising the ram and disengaging the bearing plate to allow the ram to free fall and impact a pile. Also depending from the housing is a vertical guide arrangement for limiting ram motion to generally vertical reciprocating motion limited at one end by the pile being driven and at the upper extreme by the uppermost position of the cam member. The drop hammer assembly may further include a sleeve which is removably attachable to a pile upper end and which extends upwardly therefrom to provide a sleeve portion in which the ram may reciprocate.

Abstract: When inserting a locking wedge (14) having planar wedge surfaces (16, 17) between an anvil (4; 5) and a hammerhead (1) or an anvil block lining (6) the wedge (14), which is provided with a draw head (18; 22) is drawn in between two mutually converging locking surfaces (9, 7) on the anvil and the hammerhead or the anvil block insert.

Abstract: Rock drilling apparatus including a pressure fluid driven rock drilling machine (10) and a drill unit (11). The drill unit (11) includes a drill rod (18), a drill bit (16) and a tube (20) surrounding the drill rod (18). The drill rod (18) has a collar (22) in front of a shank (21), the collar (22) maintaining the tube (20) rotatably therebetween and between the drill bit (16). The rock drilling machine (10) includes coupling device (46; 57), a socket means (42) and a rotation chuck (44) for receiving and holding the tube (20) and shank (21) connected to the machine (10), the tube (20) being radially spaced around the drill rod (18) and non-rotatably connected to the socket means (42).

Abstract: A massive piston that does not strike anything during operation reciprocates with bouncing action up and down within a cylinder. An annular pressurized gas storage chamber encircles the piston and travels up and down with it. Pressurized gas is continuously supplied into this movable chamber to be temporarily stored therein. As the piston descends toward the lower end of the cylinder, pressurized gas from this travelling chamber is automatically suddenly allowed to bypass the lower portion of the piston, thereby injecting the pressurized gas into a bounce chamber between the descending piston and a bottom assembly. When this pressurized gas rushes through the bypass, it forces an exhaust valve closed.

Abstract: A block of cushioning material arranged to be disposed in a cavity within a drive cap of a pile hammer, the drive cap being positioned on the upper end of a pile for impact engagement by the ram with the block of cushioning material during a pile driving operation, the block of cushioning material being of high heat conductivity and arranged in heat transfer relationship with the inner wall of the cavity whereby hysteresis heat generated within the block of cushioning material during impact driving is conducted by the block to the drive cap acting as a heat sink for ultimate radiation of the heat into the ambient air.

Abstract: A method of and apparatus for driving piles by the impact force delivered by a hammer disposed in a housing from the bottom end of which there extends downwardly a pile sleeve in which a pile anvil is held captive, in which shock absorbing means separate from the hammer are interposed between the bottom end of the housing and the pile anvil for absorbing rebounce forces reaching the top of the pile of lower magnitude to that of the impact force.A pile driving apparatus constructed according to another aspect of the invention comprises a hammer and resilient means in the path of travel of the hammer for transmitting the impact force of the hammer to a pile, and stop means for cutting out the resilient effect of the resilient means on the impact force by delivering a non-resilient blow to the pile.

Abstract: There is disclosed a pile-driver comprising a cylinder and a piston, the piston being in registry with a cap disposed over an article to be driven. The cap has a lining in striking relationship with the piston, which lining comprises a thermoplastic and a metal powder.

Abstract: A casing hammer for simultaneously driving casing and drilling a water well comprises a housing having an annular pneumatic chamber with an annular piston that drives an annular anvil which seals the lower end of the chamber. The chamber is formed by outer and inner sleeves of which the inner sleeve is fixed to an end cap solely at its rear end and is thus cantilevered from the end cap, being free of connection at its forward end. The forward end of the inner sleeve is stabilized by means of a relatively small clearance between the anvil and the sleeves at the front end of the chamber. The cantilevered connection of the inner sleeve at its rear end provides a smooth and unobstructed bore through which extends a rotating drill string that also extends through casing while the casing is being driven by the annular hammer.

Abstract: In a pile driver the sharp force loading on a pile at the moment of impact by a ram is absorbed by a pile driver cushion. The cushion includes a pad formed from a flexible strip of compressed knitted wire mesh wound in a flat spiral and further constructed to maintain its integrity during use and handling.

Abstract: The invention comprises an Accessory for use with a driver for forceably inserting friction rock stabilizers into bores formed in earth structures (such as mine roofs). In the depicted embodiments, the Accessory comprises an elongate body having a pin or socket at one, "lower", "driven" end for engaging and supporting an end of a stabilizer, and a limb or socket at the opposite, "upper", "drive" end for receiving a driver. The latter limb or socket is offset, to accommodate an angled, unobstructed address of the driver to the upper end of the body, and to enable a linear insertion of a lower-end-supported stabilizer into a bore. In accommodating a driver at the upper end of the body, to forceably insert a stabilizer which has its termination supported on the lower end of the body (the insertion force, therefore, being applied through the body), the Accessory facilitates bore insertion of lengthy stabilizers, by means of conventional drivers, in low headroom, subterranean openings.

Abstract: A hydraulic impactor having a reciprocating piston, a liquid coupling having a stepped bore and an actuatable driven member of a configuration to obtain the optimum energy transfer to the driven member.

Abstract: A wheeled, self-propelled apparatus has a percussion tool or hammer mounted on its forward end and an impact transmitting means carried on the tractor below the hammer. The impact transmitting means is adapted to be mounted to transmit repeated impacts from the hammer to a cemetery marker until the latter is flush with the ground surface where it will not interfere with ground maintenance, such as lawnmowing and the like.

Abstract: A pile driver has a hollow and elongated cylindrical housing. Within the housing, a ram can slide upwardly and downwardly in order to provide the force which can drive a pile into dense strata of the earth. A follower, located partially inside the housing and extending out of the bottom thereof, is struck by the ram and is thus interposed between the ram and the pile to be driven when the device is operated. Various devices are disclosed which serve as shock absorbers, the devices cooperating with the follower and with the housing in order to absorb recoil shock which is reflected back to the pile driver after a blow has been transmitted to the pile by the ram via the follower. These devices are so designed that the exterior diameter of the housing does not have to be substantially increased, which allows the pile driver thus manufactured to drive piles through surrounding guides.

Abstract: A mobile generator for producing seismic waves in the ground, which includes a mobile four-sided frame, a boom having its lower end pivotally connected to the frame, and a worm gear mounted on the frame such that by rotating the worm gear about its longitudinal axis, the boom is pivoted toward a selected impact position. A hammer, mounted on the boom, is raised and then dropped toward an anvil carried beneath the frame on the ground. The anvil has several impact-receiving surfaces such that either a P wave or a shear wave can be generated by pivoting the boom and without relocating the anvil.The anvil structure is positioned on the ground by applying a major portion of the weight of the apparatus on the anvil plate.

Abstract: A pile driver has a hollow and elongated cylindrical housing. Within the housing, a ram can slide upwardly and downwardly in order to provide the force which can drive a pile into dense strata of the earth. A follower, located partially inside the housing and extending out of the bottom therof, is struck by the ram and is thus interposed between the ram and the pile to be driven when the device is operated. Various devices are disclosed which serve as shock absorbers, the devices cooperating with the follower and with the housing in order to absorb recoil shock which is reflected back to the pile driver after a blow has been transmitted to the pile by the ram via the follower. These devices are so designed that the exterior diameter of the housing does not have to be substantially increased, which allows the pile driver thus manufactured to drive piles through surrounding guides.

Abstract: A hammer for breaking down strong abrasive materials comprising a body with a movable ram reciprocated by a drive and provided with a socket accommodating a tool intended to break down the materials by impacts during reciprocation of the ram. The end of the tool shank and the contacting bottom of the ram socket have the shape of matching spherical surfaces. The side surfaces of the tool shank and ram socket are separated by an elastic gasket and are made in the form of truncated cones whose larger base faces the working portion of the tool and angles of their cones are smaller than the angles of friction between the adjoining surfaces, the end of the working portion of the tool being provided with a blind hole which ensures better penetration of the tool into the material being broken.

Abstract: The drill has a housing receiving therein a reciprocating striker, effecting percussive action upon the tool for breaking the rock at the face of the hole, mounted at the forward part of the housing, and upon the housing itself for propelling the drill in the hole. The housing also receives therein a mechanism for rotating the tool, including a self-controlled coupling provided with a movable sleeve and a stationary sleeve and adapted to transmit a torque to the tool in only one direction of rotation. The drill is provided with a device preventing a rearward motion of the housing and its rotation during a drilling operation. The drill is characterized by having a return device for retracting the tool from the face after it has been struck by the striker.

Abstract: The driving power and driving rate of a pile driver hammer is increased without increasing the overall weight of the hammer through the use of a hydraulic spring transformer which is disposed between the ram and the pile in the housing of the hammer and presents a Q at the frequency where the mass of the ram and the stiffness of the hydraulic spring are in resonance which is less than about one.

Abstract: A hydraulic rotary percussive drill which is adapted to operate as a drill for installing rock bolts in mines is described. The drill is configured so that the shank (which holds the drill steel and bit) forms a right angle with the impact mechanism, thereby reducing the height of the drill and providing longer lengths of drill steel feed in a confined environment. A hydraulic spring force coupler transfers the impact energy from the impact mechanism to the shank, steel and bit and shapes the energy so as to provide force pulses of such length as to couple efficiently the percussive energy to the rock being drilled while reducing the strain in the steel and bit. A rotation mechanism may be mounted in the same leg of the right angle as the shank, steel and bit to rotate the steel and bit independently from the percussive action.

Abstract: A seismic wave generator constructed of fungible high density elements contained within a flexible envelope is dropped to impact upon the ground and generate seismic waves for seismic investigations. The non-rigid construction minimizes or eliminates bounce or reverberation after impact. Because of the lack of bounce and reverberation, recordings of the seismic waves produced are relatively free of superimposed wave forms otherwise resulting from multiple impacts.

Abstract: Disclosed is an apparatus for increasing the effectiveness of hammer-type pile drivers by making possible the use of higher hammer velocities without damaging the pile or the equipment. The apparatus includes a pair of aligned cylinders of unequal diameter, the smaller of which contains an anvil piston and the larger of which contains a driving piston, connected to a pile cap engageable with a pile. Means are provided for applying a deadweight load to the apparatus and for maintaining the space lying between the pistons full of liquid. In addition to enabling use of higher hammer velocities, the apparatus effectively incorporates the deadweight load into driving force when the hammer strikes.

Abstract: To facilitate the return of a percussion tool by the action of the striking mass, namely, a double-acting piston, without damage to the machine body, the tool is held by a casing attached to the body and the tool. The latter piston defines a chamber with a confronting face of the casing, the chamber being supplied with a liquid under pressure through a check valve. The chamber is connected to a reservoir by a pressure-relief valve.

Abstract: A gas cushion impact cap, used in connection with pile driving, is connected to an external pressure chamber holding an additional volume of gas, whereby there will be no appreciable change in the gas pressure during the impact. The gas pressure is primarily determined by varying the volume of a liquid contained in the pressure chamber, in response to the resistance met by the pile while penetrating the ground. The impact cap may be pre-loaded during an upwards movement, the pre-load being released upon the impact, to throw the hammer upwards again.

Abstract: A pile driver operated by a pressure supply of compressible fluid has a cushioning fluid chamber for transmitting the driving pulses to a pile. Both the cushioning chamber and the working chambers for generating the driving pulses are connected to an enclosed space from which the exhaust flow of fluid is able to escape by way of muffler means. The cushioning chamber draws in air at or near atmospheric pressure by way of said space which is in permanent communication with the exterior through the muffler means.

Abstract: A relatively quiet-operating rotary hammer for use in apparatus for securing T-edging and similar edging bands. The hammer includes a pivoted hammer head that is intermittently and continuously impacted to provide a hammering action. The hammer is impacted by a rotary structure carrying spaced hammering elements for forcibly pivoting the hammer head.

Abstract: An apparatus and a method for driving piles onshore or offshore, including driving a tubular pile within a submersed tubular jacket leg of an offshore structure and field disassembly.The apparatus hammer includes a displaceable ram structure, mounted within a pressurized air-filled housing, which is reciprocated by a pressurized working liquid against a pile-engaging anvil structure, which is in dry contact with a pile inserted within one end of the pressurized housing. The ram structure compresses air within the housing near the end of its firing stroke to preload the anvil structure for better energy transfer to the pile. The ram structure also compresses the air within the housing near the end of its loading stroke to slow the ram structure and permit full charging of working liquid accumulators, which discharge during the firing stroke to maintain working liquid pressure and prevent cavitation.

Abstract: A housing has a tool mounted therein so that a portion of the tool can slide for reciprocatory movement deeper into and farther out of the housing. A prestressed biasing spring or a cushion of gas is interposed between and acts upon the housing and the aforementioned portion of the tool, being prestressed to an extent which is less than the minimum force with which the tool can engage a workpiece when the tool is pushed against the workpiece by the weight of the hammer, and which biasing means has a flat spring characteristic.

Abstract: Electrostatic precipitators and other devices requiring vibration may be required to operate in high temperature environments, have a high dielectric strength, and withstand impacts that range into thousands of foot-pounds per second at a high repetition rate. In the present invention, a transmission or rapper rod is employed including tapered ends, that are too short to bottom in the corresponding mounting sleeves, and further including a pair of thin, malleable metallic shims between the tapered ends and the sleeves acting to accommodate dimensional tolerances and distinct surface finishes, thereby eliminating fracture-inducing impacts.

Abstract: An arrester system for arresting without substantial bounce a moving object, such as the arm of a billet stamper, is constituted by a housing mounting at one end a steel ball which is struck by the moving object. The housing also guides an axially movable steel cylinder which is normally in contact with the steel ball but is driven away from it on impact of the moving object with the ball. The housing further carries a hydraulic or resilient energy absorber which has a piston rod which extends parallel to the movement of the cylinder and which is struck by the cylinder when the latter is driven away from the steel ball. The ball and cylinder form an energy transforming device, the energy of the moving object being transferred via the ball to the cylinder, which in turn transfers the energy to the energy absorber in the direction of the piston rod. Energy transfer is effected without movement of the steel ball and without any substantial bounce of the object.

Abstract: A tool and a method for drilling holes having an increased cross-sectional area in a region remote from an exposed surface of the support structure in which the holes are to be drilled include mounting a drill bit having cutting edges at one end of a resiliently-deflectable, elongated force-transmitting spring, and angularly displacing an other end of the elongated force-transmitting spring so as to resiliently deflect said one end thereof into a plurality of positions in each of which the cutting edges of the drill bit are brought into engagement with the inner circumferential wall of the hole being drilled so as to form undercut surfaces in said region.

Abstract: A percussive drill extension rod having first and second externally threaded ends, a rod zone therebetween, and a substantially round, internal bore in the threaded ends and rod zone along the longitudinal axis of the extension rod, with particular relative dimensions designed to improve performance and reduce costs. The first threaded end of the extension rod has an outside diameter (TD) in the range of about 1.25 to about 2.5 inches, and the rod zone has an outside diameter (RD) within a range from about equal to the outside diameter (TD) of the first threaded end to about 1.1 times the outside diameter (TD) of the first threaded end. The first threaded end has a cross-sectional area (TDX) derived from the specific outside diameter of the threaded end (TD) selected from the given range of about 1.25 to about 2.5 inches. The rod zone has an annular cross-sectional area (RX) equal from about 0.64 to about 0.

Abstract: A jarring moulding machine having a table and impact receiving arrangement between the table and an anvil, which arrangement includes an annular impact member recessed into a surface of the anvil, and an impact insert of greater resilience than the impact member seated in an annular recess of step form at the inner periphery of the annular impact member. The top surface of the impact member projects slightly beyond of the anvil surface and the top surface of the impact insert projects slightly beyond of the top surface of the surrounding impact member so that the insert receives the impact before the impact member. The seating recess for the insert is undercut at the junction of its walls so as to leave a small clearance therebetween. The impact member may be of a polyethylene synthetic plastics material and the insert may be of rubbery polyurethane.

Abstract: The removal of a lining, for example of wood, from a pile driving head is a very difficult and time-consuming operation. In order to remove the lining easily from the pile driving head, at least one armature is embedded in the lining to be used in the pile driving head, said armature being provided with fastening means, and a tool is connected with the armature by means of said fastening means for removing the lining. When the lining is stroke down during the pile driving operation, the armature with at least part of the lining is drawn from the pile driving head by means of said energized tool supporting on the driving head and/or a further part of the lining.

Abstract: Apparatus for use in driving a pile by means of successive hammer blows at the same time as a vibratory force is to be applied to the pile comprises means for simultaneously transmitting, to a pile to be driven, a force produced by a hammer blow and a vibrating force which is generated by the application of the hammer blow.

Abstract: An impact tool is used to apply an impact blow to the underside of a portion of a roof which has been partly cut away, wherein the portion of the roof is removed for the installation of a dormer. The impact tool consists of an elongated hollow handle formed from a plurality of sections, wherein the sections permit length adjustment of the handle. A heavy weight element communicates with an upper free end of a top section and a rubber cushion element communicates with a bottom end of a bottom section.

Abstract: Apparatus is disclosed for cushioning or attenuating the highly destructive, peak impact forces which occur between an operating pile hammer ram and the pile cap or helmet at the moment of initial contact while permitting a maximum of the delivered energy to be converted into useful work in driving the pile. Such impact forces, which can physically damage the pile hammer, the helmet, the pile, or all three, are effectively and efficiently reduced by means of an energy storing, flat spring member. Said member is so arranged as to permit a determinable, relatively constant portion of the energy absorbed from the hammer blow to be stored during hammer deceleration and then be returned to the hammer ram on its retraction stroke while minimizing that portion of absorbed energy which is irrecoverably converted to heat.

Abstract: A ram-borer apparatus is described which comprises a tubular housing, a percussion piston which is movable axially to and fro in the housing, and a striker-tip which is arranged to slide in an axial direction relative to the housing and which bears against the housing in the working direction via a resilient member. In accordance with the invention, there is attached to the rear end of the housing a drag-sock for coupling a tube or cable, etc. to the housing, and/or an expander-cone for enlarging the bore formed by the apparatus, and/or a steering tube for steering the apparatus along a straight or preselected arcuate path.

Abstract: The post driver apparatus of the instant invention is designed to be mounted on a truck chassis that can be readily moved from site to site and comprises a fluid-pressure impact hammer mounted in a shock absorbing cage assembly that permits rapid driving of posts into the ground without transmission of substantial shock forces to the frame and chassis on which the post driver is mounted. The apparatus is also equipped with means to vary the location and orientation of the impact hammer with respect to the truck chassis thereby minimizing the precision with which the truck chassis must be located.

Abstract: A very powerful pile driver is disclosed capable of operation in the air, partially submerged or totally submerged in the ocean for driving long piles into the ocean floor in deep water construction jobs. The pile driver includes a cylindrical housing, a movable massive weight within the housing, an annular cylindrical thrust-transferring member defining a discharge chamber below this weight, and a movable driving head attached to this annular member, forming a thrust-transmitting assembly adapted to be engaged with the pile. Pressurized gas such as compressed air is discharged from gas discharge apparatus, called an airgun located within the discharge chamber and provides two driving thrusts for each discharge.

Abstract: A penetrometer frame for mounting on, for example, a truck and comprising a fixed part provided with slides which guide a moving part in the form of a frame which itself serves as a guide for a driving hammer and which may be raised or lowered by two hydraulic rams. The fixed part of the frame is pivoted on a platform about a horizontal pivot offset from the point where tubes are inserted or removed. The arrangement is such that extending the rams causes the penetrometer frame to pivot and allows access to the position at which tubes are inserted or removed.

Abstract: A fatigue resistant anvil bit is described for use on a percussion rock drill. The anvil bit has a shank having a substantially uniform cross section terminated in a threaded end portion. A bit head is threadably mounted on the end portion having a diameter substantially greater than the bit shank. An anvil ring is shrunk fit on the shank engaging the bit head to provide lateral support and minimize the creation of fatigue fractures.