AU2007229422A1 - Ground cutting tools and methods of forming same - Google Patents

Description

GROUND CUTTING TOOLS AND METHODS OF FORMING SAME FIELD OF INVENTION THIS INVENTION relates to ground cutting tools and to methods of forming ground O cutting tools. The invention has particular application to ground cutting tools for cutting and/or C 5 breaking up hard rock. However, the invention is not limited to this field of use. The invention has particular application to a plurality of ground cutting tools incorporated into an assembly for CI cutting and/or breaking up hard rock such as may be encountered, for example, in mining of iron ore. However, the invention is not limited to this field of use. In one particular form, the CI invention has application to ground cutting tools having cutting elements formed from or with an r- 10 advanced diamond composite, the cutting elements being partially embedded into tool bodies to form the cutting tools. In another particular form, the invention has application to ground cutting tools having cutting elements formed from a wear resistant material such as tungsten carbide or tungsten carbide-cobalt, the cutting elements being partially embedded into tool bodies to form the ground cutting tools. It will be appreciated that the invention is not limited to a particular material for the cutting elements.

BACKGROUND ART Ground cutting tools for use in mining of coal and tunnelling through rock have traditionally comprised a "pick" or "drag tool" formed as a chisel-shaped or pointed rock cutting tool mounted to a sleeve in which they may rotate and in turn mounted to a rotatable drum. In this 0 specification, unless the context indicates otherwise, the term "ground cutting tool" is to be taken to incorporate "picks" and "drag tools". The ground cutting tools may have a cutting element embedded in one end to for a cutting tip. The cutting element has normally been formed from tungsten carbide-cobalt material mounted. The ground cutting tool normally includes, or is mounted to, the end of a steel shank. A plurality of such ground cutting tools is mounted to a cutting head via respective sleeves. The ground cutting tools may rotate in the sleeves in which they are mounted. The cutting head is typically in the form of a rotatable drum. In the art in general, the term abrasion resistant material may have a broad general meaning referring to a material's ability to resist wear caused by two materials rubbing together. In this specification, unless the context requires otherwise, the term abrasion resistant material means a material comprising ADC, or a material which incorporates ADC or tungsten carbide or their equivalents in a composite weld having supported therein a wear resistant material in grit-like form, the grits being or tungsten carbide or their equivalents.

O Improvements have been made to ground cutting tools by mounting a cutting element formed from advanced diamond composite (ADC) to a tool body. In other words, the normal O wear resistant cutting elements of tungsten carbide-cobalt have been substituted by the ADC cutting elements. Examples of such improvements are disclosed in the specification of International Patent Application No. PCT/AU2001/000567 filed 18 May 2001, the contents of S which are incorporated herein by reference. In this specification, the cutting tools in general, and the "picks" in particular, taught in PCT/AU2001/000567 are referred to as "the improved cutting S tool" unless the context indicates otherwise. In this specification, unless the context indicates otherwise, the terms advanced diamond compact, advanced diamond composite and ADC refer to N, 10 International Patent Application Nos. PCT/AU1985/000201, PCT/AU1988/000058 and/or PCT/AU1989/000273.

The improved cutting tool makes use of metal matrix composites (MMC) to bond the ADC cutting element or elements to the tool body. The improved cutting tool provides a considerably extended life of the cutting tool by virtue of the significantly diminished wear of the cutting element formed from ADC. However, inadequacies of the tool body of the improved cutting tool may be the mode of failure when an attempt is made to take advantage of its extended life in service. The tool body, being the remainder of the improved cutting tool without the cutting element, may wear undesirably rapidly, thereby reducing the length of life in service for the improved cutting tool despite the significant increase in wear resistance of the ADC ?0 cutting element.

The present invention aims to provide ground cutting tools and to methods of forming ground cutting tools which alleviate at least one of the inadequacies of the prior art. Other aims and advantages of the invention may become apparent from the following description.

DISCLOSURE OF THE INVENTION With the foregoing in view, this invention in one aspect resides broadly in a ground cutting tool including:a tool body having one or more cutting elements formed from ADC and embedded in said tool body to provide an exposed portion of said one or more cutting elements protruding from said tool body, and an outer face of said tool body, at least some of said outer face being formed from an abrasion resistant material.

O The abrasion resistant material may be of any form such as, for example a hardfacing comprising one or more beads of composite weld having supported therein a wear resistant O material in grit-like form disposed about and forming the outer face of the tool body.

N, Alternatively, one or more rings of hard-wearing material, such as tungsten carbide, may be formed onto a tool blank to form the tool body and may be bonded thereto, for example, by welding, brazing or soldering. The abrasion resistant material may also be provided about an (-i outer circumferential face of a sleeve into which one or more of the cutting elements may be S mounted. The sleeve may be formed entirely from the abrasion resistant material in the form of hard-wearing material such as tungsten carbide. The entire tool body may be formed from the CNI 10 abrasion resistant material, in which case, the cutting element or elements are partially embedded in the abrasion resistant material to provide the exposed portion as hereinbefore described.

Typically, the tool body includes a shank by which the finished ground cutting tool may be mounted to a sleeve for mounting a plurality of such ground cutting tools to a cutting head via the respective sleeves.

When the abrasion resistant material is provided in the form of one or more beads of composite weld, the beads may be provided in a circumferentially running direction about the tool body. The hardfacing may include a plurality of beads formed to include a substantially contiguous layer. The contiguous layer may be provided by a plurality of circumferentially running beads in edge abutting relationship. The hardfacing may include one or more layers of composite weld. In such form, the tool body may include a tool blank having formations such that any one or more layers overlaid by a further layer substantially retain their composite form as a composite weld having supported therein a wear resistant material in grit-like form to form the tool body when provided thereon having an outer face formed from an abrasion resistant material.

The wear resistant material grits may be the same material as the wear resistant material forming the cutting element, or it maybe a different wear resistant material. Alternatively, one or more rings of wear resistant material, such as tungsten carbide, may be formed onto the tool body and may be bonded thereto, for example, by welding, brazing or soldering. The abrasion resistant material may also be provided about an outer circumferential face of a sleeve into which a cutting tool may be mounted.

O The tool blank may include one or more lands upon which said hardfacing is formed.

The one or more lands may be formed by machining onto or into the tool body or as a preformed O tool blank. Of course, the preformed tool blank may be machined to provide the lands.

In a preferred form, the ground cutting tool includes a tool blank of substantially circular cross-section and having one or more circumferentially running lands; N, one or more cutting elements formed from an advanced diamond composite and mounted to an end of said tool body so as to comprise an embedded portion embedded in said CI tool blank and an exposed portion protruding from said tool blank; a hardfacing formed on said one or more lands and comprising one or more layers of C 10 composite weld having supported therein a wear resistant material in grit-like form, said one or more layers being arranged remote from said exposed portion a distance sufficient to permit the exposed portion to engage with a material to be cut, and the hardfacing and tool blank together comprising a tool body having an outer face formed an abrasion resistant material.

The one or more layers may be provided by a plurality of circumferentially running beads of weld. The abrasion resistant material is provided substantially independently from or substantially in such manner as to leave unaffected the bonding of the one or more cutting elements to or with the tool blank and/or tool body. The composite weld is formed in situ onto the aforementioned formations on the tool blank, thereby bonding the abrasion resistant material thereto to form the tool body.

,0 When the abrasion resistant material is provided in the form of a plurality of rings of hard-wearing material, the rings are preferably bonded to a tool blank in similar form to the tool blank upon composite weld hardfacing may be applied. In such form, the rings are preferably brazed, silver soldered or soldered to the tool blank to form the tool body.

In another aspect, this invention resides broadly in a method of forming a ground cutting tool including:providing a tool body; providing one or more cutting elements formed from ADC; embedding said one or more cutting elements in said tool body to provide an exposed portion of said one or more cutting elements protruding from said tool body; and providing an outer face of said tool body, at least some of said outer face being formed from an abrasion resistant material.

The abrasion resistant material may be formed by laying down a hardfacing comprising (-i one or more beads of composite weld having supported therein a wear resistant material in grit- O like form. In such form, the tool body includes a tool blank having formed thereon one or more N, lands onto which the one or more beads may be laid up to form the outer face formed from an abrasion resistant material. The one or more beads may be laid down in a circumferentially S running direction about the tool body. The hardfacing may be laid down as a substantially contiguous layer. For example, successive beads may be laid down one after the other in edge

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CNI abutting relationship. In such form, one or more layers of composite weld may be provided by laying down successive beads of weld on one or more previously laid down beads. In such form, NI 10 the method may include machining formations onto or into the tool body to form a tool blank.

The machined formations may include one or more lands formed such that the hardfacing may be provided on the one or more lands. The one or more cutting elements are typically mounted substantially centrally and coaxially with respect to one end of the tool body. The one or more cutting elements may abut the tool blank axially, or be embedded therein.

The formation of the lands may be provided, for example, by machining the lands onto or into the tool body to form the tool blank or onto or into a preformed tool blank. If the one or more cutting elements are provided prior to laying down the hardfacing, cooling of the workpiece may be provided to enable the hardfacing to be laid relatively close to the one or more cutting elements without substantially affecting the bonding of the one or more cutting elements to the tool body. The hardfacing may be laid down in accordance with the present invention prior to mounting the one or more cutting elements to the hardfaced tool body in accordance with the improved cutting tool as hereinbefore defined.

In such an arrangement, the tool body may be kept cool by mounting the shank in a cooling bath of water. For example, a sleeve may be fitted over the shank and water passed into and out of the sleeve with a view to maintaining a temperature of 200'C or less. In this respect, the wire may be selected from, for example, 0.6 mm to 1.2 mm diameter confirming to BS2901 Part 1 1970A18 and AWS A5.18 E70S-6. The workpiece may be held at an appropriate angle, such as tilted tip down, and rotated at the necessary speed to lay the weld down whilst adding the wear resistant material which may, for example, be provided in the form of tungsten carbide grit.

The angle of the workpiece and welding angle of the torch are believed to be of less importance

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O than maintaining the temperature of the workpiece below that which would adversely affect the o bonding of the cutting element to the tool body. The weld current may be from 100 A to 200 A at

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N a potential from 25 V to 30 V. The grit may be added into the molten weld pool during the welding process by any suitable means, and is preferably to mesh size 12/35 5 In another aspect, the present invention resides broadly in a method of hardfacing a tool I body of substantially circular cross-section for a cutting tool including:laying down one or more beads of composite weld having supported therein a wear S resistant material in grit-like form about an outer circumferential face of the tool body and spaced from a concavity into which one or more cutting elements may be mounted.

In another aspect, this invention resides broadly in a ground cutting tool including:a tool body of substantially circular cross-section formed into a shank for mounting the tool body and two or more engagement portions for engaging ground, each engagement portion having one or more cutting elements embedded therein, a one or more circumferentially running lands extending axially along a substantial part of said engagement portion and being arranged in substantially axial alignment with one another; and a hardfacing on at least some of said lands, said hardfacing including one or more layers of composite weld supporting therein a wear resistant material in grit-like form.

In another aspect, this invention resides broadly in a ground cutting tool including:a tool body of substantially circular cross-section formed into a shank for mounting the tool body and an engagement portion for engaging ground, the engagement portion having one or more cutting elements embedded therein, one or more circumferentially running lands extending axially along a substantial part of said tool body and three or more transection elements embedded in said engagement portion, said transection elements being of substantially planar form and extending radially outward from the one or more cutting elements and axially from the tip of the engagement portion, said transection elements being formed from material which is more wear resistant than the material in which they are embedded; and a hardfacing on at least some of said lands, said hardfacing including one or more layers of composite weld supporting therein a wear resistant material in grit-like form.

In such form, the transection elements do not completely transect the tool body.

However, where the engagement portion does not include the one or more cutting elements, the transection elements are arranged diametrically across the tool body.

O In another aspect, this invention resides broadly in a ground cutting tool including:a tool body of substantially circular cross-section formed into a shank for mounting the O tool body and an engagement portion for engaging ground, the engagement portion having one or ,i more cutting elements embedded therein, a plurality of circumferentially running machined lands spaced axially along a substantial part of said tool body; and

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N, a hardfacing on at least some of said lands, said hardfacing including one or more layers of composite weld supporting therein a wear resistant material in grit-like form.

,IC In this specification, the term "land", unless the context requires otherwise, refers to encompass any surface that can accommodate one or more beads of weld. This meaning may be 10 taken to encompass the meaning of the term as defined in The Procedure Handbook of Arc Welding (4th edition) published by The James F Lincoln Arc Welding Foundation, Cleveland, Ohio (May 2000).

Typically, the shank is provided for mounting to or into a sleeve which in turn is mounted to a drum assembly to permit the engagement portion to engage with ground to be cut when the drum is rotated about its axis. The hardfacing is typically built up to form the outer face of the tool body. The one or more cutting elements and where provided, the transection elements, are typically formed from a wear resistant material such as tungsten carbide or tungsten carbidecobalt material or the like. The one or more cutting elements may be formed from a natural or synthetic diamond composite material such as polycrystalline diamond (PCD), polycrystalline diamond compact (PDC), advanced diamond composites or such like, and such materials are to be taken to be incorporated within the meaning of the term ADC unless the context requires otherwise.

The engagement portion of the tool body may include one or more cutting elements formed from a wear resistant material and embedded in said tool body to provide an exposed portion of said one or more cutting elements protruding from said tool body. In such form, the hardfacing may be spaced from the one or more cutting elements to accommodate the protrusion thereof from the tool body. Alternatively, the hardfacing may be formed to encapsulate the exposed portion as well as the engagement portion of the tool body, there being provided a gap between or cap over the one or more cutting elements and the hardfacing.

The hardfacing may be, for example, formed from one or more beads of composite weld having supported therein a wear resistant material in grit-like form disposed about the outer 8 S circumferential face of the tool body. The wear resistant material grits may be the same material as the wear resistant material forming the cutting element, or it maybe a different wear resistant 0 material. Alternatively, one or more rings of wear resistant material, such as tungsten carbide, C may be formed onto the tool body and may be bonded thereto, for example, by welding, brazing or soldering. The hardfacing may also be provided about an outer circumferential face of a sleeve N, into which a cutting tool may be mounted.

The hardfacing may be provided with a plurality of flutes, curved or straight, and N, running generally axially to project radially outward from the outer face of the remainder of the hardfacing. In such form, one or more beads of composite weld are laid down over the N 10 circumferentially running beads. The size of and spacing between the hardfacing flutes are selected such as to substantially avoid dissolution of the wear resistant material in grit-like form into the matrix of the composite weld. The provision of the hardfacing flutes is for the purpose of enhancing the propensity for spinning the cutting tool about its axis when in use, thereby promoting even wear of the cutting tool about the axis.

It will be appreciated that some alloys, such as chromium carbide, may be regarded as a wear resistant material on its own accord as opposed to being a composite. The present invention involves the use of a composite weld having supported therein wear resistant material in grit-like form. Accordingly, for composite weld wherein the weld matrix is relatively wear resistant of itself, the wear resistant material supported therein in grit-like form is typically selected from materials which are more wear resistant than the material used for the matrix.

In another aspect the present invention resides broadly in a ground cutting tool including:a shank having which may be inserted into a sleeve for rotation about its axis and a mounting formation formed on or in one end; a tool body of substantially circular cross-section and having a passage extending substantially axially through the tool body, the passage having a complementary mounting formation for mounting the tool body to the mounting formation formed on or in said shank and one or more cutting elements in the passage of the tool body abutting the shank, and wherein the cutting elements are formed from an advanced diamond composite material and the tool body is formed from sintered tungsten carbide.

O In such form, the tool body forms a collar around the cutting element and the mounting formation of the shank.

0 In another aspect, the present invention resides broadly in a ground cutting tool CI including:a shank body construct having a shaft portion extending from one end and which may be S inserted into a sleeve for rotation about its axis and a tool body portion of substantially circular cross-section of greater diameter than the shaft portion and extending axially from the shaft CI portion; and one or more cutting elements embedded in the tool body portion in or at the end remote CI 10 from the shaft portion, and wherein the cutting elements are formed from an advanced diamond composite material and the shank body construct is formed from sintered tungsten carbide.

In another aspect, the present invention resides broadly in a ground cutting tool including:a shank having a proximal end which may be inserted into a sleeve for rotation about its axis and a distal end remote from the proximal end, the proximal end of the shank having a mounting formation formed thereon or therein; a tool body of substantially circular cross-section and having a complementary mounting formation formed about its axis for mounting the tool body to the shank and one or more cutting elements embedded in the tool body remote from the complementary mounting formation, and wherein the cutting elements are formed from an advanced diamond composite material and the tool body is formed is formed from sintered tungsten carbide.

Typically, the shank is formed from forged steel. Typically, the cutting elements are mounted to the tool body with the aid of brazing. Where the cutting element abuts the shank, it is preferred that the cutting element is also brazed to the shank.

In typical form, the mounting formation includes a flange extending radially outward from the shank portion near one end of a shaft portion, the shaft portion and the flange together constituting the shank. The shaft portion is of substantially cylindrical form and substantially circular cross-section, of elongate form extending from a proximal end to the flange. The flange preferably includes a lip around its circumferential periphery extending in the same axial 'u S direction as a distal tip on the other end of the shaft portion from the proximal end thereof. In O such form, the mounting formation includes a central cone-like projection surrounded by a planar S annulus extending radially outward from the base of the cone-like projection, and the outer CI periphery of the planar annulus having a ridge forming the aforementioned lip circumscribing the planar annulus, the ridge being on the same side of the planar annulus as the central cone-like N, projection. The cone-like projection may have a shaped apex, such as a bullet or ogival shaped profile.

NI The cross-section of the lip preferably includes a sloped outer portion forming a O relatively short truncated cone commensurate with the sloping sides of the tool body which is 10 also preferably formed as a truncated cone. The cutting element, tool body and lip of the flange of the shank all have aligned outer face portions to constitute the outer peripheral face or surface of the cutting tool, but the outer periphery in total may be constituted of a series of intersecting cones of different slope. In particular, it is preferred that the cutting element and a portion of the tool body be of a shallower slope than the intermediate portion of the tool body axially interposed between the apical end and the flange. It is also preferred that the sloped outer portion of the lip of the flange and part of the outer face of the tool body be of a shallower slope than the intermediate portion of the tool body. In such form, the outer face or surface of the ground cutting tool between the apical end and the flange is of a bell-like or campanulate or arrowhead-like profile.

In an alternative form, particularly in aggressive situations, both the shank and tool body may be integrally formed from a wear resistant material such as sintered tungsten carbide as hereinbefore described. In such form, integral shank and tool body include a cutting element embedded in its apical end to provide the aforesaid profile of the ground cutting tool.

BRIEF DESCRIPTION OF THE DRAWINGS In order that this invention may be more readily understood and put into practical effect, reference will now be made to the accompanying drawings which illustrate exemplifying embodiments of the invention, wherein:- Fig. 1 is a part sectional, part side view of the ground cutting tool having composite weld hardfacing according to the invention; Fig. 2 is a cross sectional view of the ground cutting tool having rings of hard-wearing material according to the invention; O Fig. 3 is a part sectional, part side view of the ground cutting tool having one form of sleeve formed from hard-wearing material according to the invention; O Fig. 4 is a part sectional, part side view of the ground cutting tool having another form c of sleeve formed from hard-wearing material according to the invention Fig. 5 is a side view of the ground cutting tool of Fig. 1; and Fig. 6 is a side view of a tool blank for the ground cutting of Fig. 1.

Fig. 7 is a diagrammatic sectional view of the ground cutting tool according to the N, invention; Fig. 8 is a diagrammatic sectional view of a machined profile for the tool body of an 10 alternative ground cutting tool according to the invention Fig. 9 is a diagrammatic side/sectional view of a second alternative ground cutting tool according to the invention which includes two engagement portions; Fig. 10 is a diagrammatic side/sectional view of a third alternative ground cutting tool according to the invention which includes two engagement portions; Figs. 11 and 12 are diagrammatic side and end views of a third alternative ground cutting tool having transection elements; and Figs. 13 and 14 are diagrammatic side and end views a fourth alternative ground cutting tool shown and described in respect of Figs. 11 and 12.

Figs. 15 and 16 are diagrammatic side and end views a fifth alternative ground cutting tool shown and described in respect of Figs. 11 and 12.

DETAILED DESCRIPTION OF THE DRAWINGS The ground cutting tool 10 shown in Figs. 1 and 5 includes tool body 11 having a cutting element 12 embedded in one end. The cutting element has a conical end and cylindrical portion extending from the conical end, the cylindrical portion being substantially completely embedded in the end of the tool body with the conical portion projecting therefrom as shown. The tool body has a stepped shank 13 extending from a proximal end 26 to meet a tapered tip 14 extending from other end, the stepped shank and tapered tip being separated from one another by a grooved flange 15. The stepped shank has a rebate groove 27 spaced from the proximal end towards the grooved flange. The stepped shank includes a shank step 28 such that the shank has a larger diameter near the grooved flange and a smaller diameter near the proximal end. The larger and smaller diameter portions of the stepped shank are of substantially constant cross-section.

O A hardfacing is provided on the tool body as shown in detail in Fig. 1 and comprises a groove bead 16 which substantially fills the groove to the level of the cylindrical faces of the O flange, and a plurality of hard facing beads shown typically at 17 extending from adjacent and N, adjoining the groove bead and along the tapered tip of the tool body from the flange face to a plurality of bevel profile beads shown typically at 19 to terminate at the second step 25 to S conform substantially to the profile of a tapered tip of the ground cutting tool. The hardfacing beads are laid up side-by-side to form a bell profile as shown at 18 and a bevelled profile as N, shown at 19 in Fig. 1. The hardfacing comprises the outer face of abrasion resistant material rapplied to a tool blank 20 to provide the tool body.

c1 10 The ground cutting tool 21 shown in Fig. 2 includes a tool blank 22 onto which are fixed three tungsten carbide rings 23 (23c being a smaller diameter than 23b which is smaller than 23a) having a frusto-conical outer face 33, in inner cylindrical face 35 and an radial face 34. The rings are provided in axial abutting relationship with respect to one another, the smallest one abutting axially with a conical ring 24 adjacent the cutting element. The conical ring has a frusto-conical outer face 34 which is at a shallower pitch than the frusto-conical faces fo the other rings, an inner frusto-conical face 36 meeting a radial face 34 and a partial cylindrical face 37 extending axially between the inner frusto-conical face and the outer frusto-conical face.

The ground cutting tool 40 having one form of sleeve 52 shown in Fig. 3 has a similar outer profile to that of the ground cutting tool shown in Figs. 1 and 2, and the same reference !0 numerals are used to refer to corresponding equivalent parts. The tool blank 51 includes a frustoconical outer face 53 which extends from a flange 56 to the cutting element 12a. A wall portion 57 is interposed between the distal tip of the sleeve and the body of the cutting element The sleeve is formed from tungsten carbide to comprise the abrasion resistant material on the outer face of the tool body.

The ground cutting tool 50 having another form of sleeve 53 shown in Fig. 4 is the same in every respect to that shown in Fig. 3, except that the other form of sleeve is thicker and there is no wall portion between the cutting element and the sleeve. The cutting element 12a in Figs. 3 and 4 includes a flange portion 54 to provide a smooth transition in respect of the outer face of the ground cutting tool as between the cutting element and the sleeve.

As shown in particular in Fig. 6, the grooved flange includes a V-shaped groove 121 substantially central of the flange and between two cylindrical faces 129. A flange face 122 S facing the tapered tip delineates the flange from the tapered tip which has a first step 123, and a bevel 124 remote from the first step towards the cutting element, the tool body terminating in a O second step 125 comprising a circular annular face through which the cutting element passes. The C pitch angle of the bevel is more acute towards the axis of the ground cutting tool than the cone face of the cutting element. This permits the hard facing to adopt a profile having a frusto- N, conical profile portion shown at 132 in Fig. 5 which has substantially the same pitch angle as the pitch angle of the cone portion of the cutting element from the wider end of the frusto-conical I profile extends a bell profile 131.

The ground cutting tool described in Figs. 1 to 4 may be formed from ground cutting I 10 tools of the prior art which may have an idealised profile as shown at 130 in Fig. 5. The tool blank may be machined down to a profile such as that illustrated in Fig. 6 and a plurality of beads of composite weld having supported therein a wear resistant material in grip like form laid up one after the other until their height reaches substantially that of the idealised profile, or a plurality of rings of tungsten carbide or ADC mounted about the lands and fixed thereto by brazing. A plurality of cutting tools may typically be mounted in a sleeve for rotation when the ground cutting tool and sleeve is mounted as an assembly to a drum, the assembly typically being mounted with the ground cutting tools at a skewed angle with respect to the radius and axis of the drum.

The cutting element is typically formed from ADC (advanced diamond composite) and has a bullet shaped protruding portion extending from the conical face of the tool body, the other part of the cutting element comprising the embedded portion of the cutting element. The bonding matrix is typically a metal matrix composite or the like as described in International Patent Specification No. PCT/AU2001/000567. The circumferential face of the tool body, except for that of the shank, is substantially covered by the abrasion resistant material. It will be appreciated that as the abrasion resistant material wears away, more becomes exposed to provide the outer face of abrasion resistant material in accordance with the invention.

A gap is provided between the bonding matrix and the first bead of weld 131 or third bead of weld 133 not only to provide the frusto-conical face, but also to avoid the possibility of a heat affected zone from application of the hard facing extending to and possible adversely affecting the bonding matrix. The angle of the frusto-conical face would typically be selected to be commensurate with the angle of the pick to the drum to which it is mounted. By selecting the lI-, S appropriate lengths of the land portions and height of the wall portions, a suitable bell profile of the hard facing can be provided. Arranged with arrow 129 facing upward, the tool body is rotated O at a suitable speed to lay down the hard facing. Additionally, the tool body may typically be i cooled, particularly if the cutting element is already in place in the tool body. The cutting element may be bonded to the tool body after the forming of the lands and wall portions and the laying S down of the hardfacing. Cooling of the tool body is effected during machining in the normal manner with a cutting fluid, but cooling of the tool body during welding may be with the Ci provision of a cooling water stream as close as practical to the site of the weld. Alternatively, water cooled jaws may be used to hold the part and also cool the tool body, particularly the CI 10 bonded portion of the tool body.

The hardfacing may be applied by any suitable welding process, and, metal inert gas (mig) welding or tungsten inert gas (tig) welding may be used for this purpose. In such a process, the weld pool is impinged with particles of wear resistant material, for example, tungsten carbide in grit-like form. The beads are laid up until a hard facing of desired profile is formed substantially all the way around the tool body and if required, successive layers are built up to form the preferred bell profile. The wear resistant material tungsten carbide grit is typically added to the molten weld pool during the welding process, and may be added by any suitable means.

Typically, the grit size, for example, is mesh size 12/35. Although this size gives numerical limits to the grit size of the wear resistant material, it is suggested that a suitable size of the grit be that !0 which would be detectable by the human senses.

In such form, the rotating speed of the tool body to apply weld layers would typically be in the range of 15 to 25 millimetres per second. The welding torch may be angled from the vertical, such as from 15 to 300 when applied to the lands on the tool body. Current may be in the range of from 200 amps to 300 amps and the electrical potential from 22 volts to 26 volts on ARM- i and ARM-2 wires. In this respect, the wire may be selected from, for example, 0.6 mm to 1.2 mm diameter confirming to BS2901 Part 1 1970A18 and AWS A5.18 E70S-6. The tool body may be preheated, and the surface treated if required to provide the appropriate weld bond between the material of the tool body and the composite weld of the hard facing.

If desired, further runs of beads may be laid as double layering or laid across the circumferential beads such that the outer profile of the hardfaced tool body has a swale, fluted or star-like cross-section so as to increase the circumferential contact shear applied to the pick in O order to improve the propensity for the pick to rotate in its sheath or sleeve. Rotation of the pick is critical to maintain tangentially consistent wear of the cutting element, thereby maximising its O service life potential.

I The improved ground cutting tool 210 shown in Fig. 7 includes an engagement portion 211 extending from one end and a shank portion 212 extending from the other end of the tool.

The engagement and shank portions are separated from one another along the axis of the tool by a flange 214. The tool comprises a tool body 218 onto which a hardfacing or hardfaced capping is N, provided. The capping includes a plurality of circumferentially running beads of composite weld shown typically at 217. The composite weld is formed as a weld matrix having supported therein ,I 10 wear resistant material in grit-like form. The hardfacing is formed onto a plurality of lands which have been machined or otherwise formed onto or into the outer face of the tool body. The lands are formed to provide a machined profile onto which the hardfacing may be deposited. The machined profile also includes a circumferentially running V-shaped groove extending all the way around the cylindrical face of the flange. The hardfacing also includes one or more beads filling the groove and covering the circumferential face of the flange.

The lands, as indicated by the tie lines leading from reference numeral 220 in Fig. 7, constitute a stepped profile of successively smaller diameter cylinders leading away from the flange. Orientation and re-orientation of the tool body permits the circumferential faces 21 and the annular disc faces 222 of the stepped profile to function as lands onto which the successive beads of weld are laid as the tool body is rotated. The beads of weld are laid up in side-by-side, edge-abutting relationship. Successive beads are laid up to form one or more layers of composite weld until an external profile is reached conforming at least roughly to a compound cone having a tip at 216 about as sharp as can be expected from having been formed from a dot or the like of composite weld. The machined profile also includes a frusto-conical face 223 towards the tip of the hardfacing.

A cutting element 219 is embedded into the tool body beneath the hardfacing. A gap 224 is left beneath the hardfacing from tip of the hardfacing to the annular disc face adjacent the cutting element. Thus, that portion of the cutting element which would normally be exposed is encapsulated by the hardfacing, but a gap is provided such that there is no contact between the hardfacing and the cutting element during the formation of the hardfacing thereon. The gap may S be filled with a suitable material such as, but not limited to, copper in the form of a copper cap covering the exposed portion of the cutting element.

O The tool body 240 for the alternative cutting tool shown in Fig. 8 includes the shank CI portion 212, flange 214 and flange groove 213 substantially the same as those described with reference to Fig. 7. However, there is no cutting element, and instead of the cutting element and S the frusto-conical portion described with respect to Fig. 7 there is a six-step profile comprising six circumferential lands 242, 244, 246, 248, 250 and 252 separated from one another by six Ci annular disc lands 241, 243, 235, 237, 249 and 251. The distal end of the tool body 240 remote from the flange is formed as a circular end face 253. Successive beads of composite weld having N, 10 supported therein wear resistant material in grit-like form may be laid up on the machined profile to achieve an as-welded profile substantially conforming to a compound conical external profile at least similar to that described with reference to Fig. 7.

The second alternative cutting tool 250 shown in Figs. 9 and 10 includes two engagement portions 251 and 252 is end-to-end abutting axial alignment with one another. Each engagement portion includes a cutting element 219 and a hardfacing 257 made up of a plurality of beads shown typically at 217 in similar fashion to the other embodiments of the cutting tool already described. The hardfacing is shown on one side only of the cutting tool to retain clarity in respect of the inclusion of a second engagement element. It will also be appreciated that the particular arrangement of the beads is exemplary only, and should not be taken to require the beads to be laid down in any apparent order which may be construed from the representation thereof in the drawing. Successive beads are laid down on a land as herein defined, sometimes being a machined land and sometimes being a land formed from the paying down of a previous bead of weld. Where several layers ofhardfacing weld are provided, the workpiece is cooled as herein described to substantially prevent degradation of the grit-like wear resistant material in the composite weld. It will be seen that the only difference between the two versions of the second alternative cutting tool relate to the configuration of the engagement portions.

The third alternative cutting tool 260 is shown in Figs. 11 and 12. The fourth alternative cutting tools 270 is shown in Figs. 13 and 14. The fifth alternative cutting tool 280 is shown in Figs. 15 and 16. Each of these alternatives include transection elements. In the case of the third alternative cutting tool, the transection elements 261 axially abut the cutting element 219 and extend radially therefrom. In the case of the fourth and fifth cutting tools, there are provided O diametric transection elements 272 ands 281 respectively, and in the case of the fourth alternative cutting tool, there are two radius transection elements 271 arranged substantially at right angles to O the midpoint of the diametric transection element 272. In the case of the fifth alternative cutting C tool, there are four radius transection elements 282 arranged substantially at 600 to each other and the midpoint of the diametric transection element 281. Hardfacing (not shown) may be applied to the third, fourth and fifth alternative ground cutting tools in accordance with the invention herein described, such as, for example, that depicted in respect of Fig. 7.

N In use, the cutting tools of the present invention may be mounted to a cutting roller of the type which may be used for example in mining. It would be typical to insert the cutting tools N 10 into sleeves arranged to provide an angle of attack from 40 to 600. Alternatively; the angle of attack may be set in the range of 60 to 800 in accordance with the disclosure in International Patent Specification No. PCT/AU2001/000567. The angle of attack comprises an angle to the radial extension of the roller (obtuse to the tangent in the direction of intended rotation) as well as an angle to the roller axis. This arrangement permits the cutting tools to rotate as they bear against the rock-face being cut by the cutting elements. The rotation provides relatively even wear circumferentially around the cutting tool.

It is believed that providing hard facing to the tool body to provide the cutting tool in accordance with the present invention will enable a longer life of the cutting tool as an assembly because of the extra wear life expected of cutting elements made from advanced diamond composite and the consequential requirement that the tool body be of a more wear resistant nature. It will be appreciated that the hard facing applied to the tool body is not required to have the same wear characteristics as the cutting element, and indeed it is the cutting element would perform most of the cutting of the hard rock when the cutting tool is in use. However, abrasion of the tool body as the by-product of hard rock cutting can be reduced by application of the hard facing according to the present invention.In this specification, a composite material is a combination of materials differing in form or composition on a macroscale. Accordingly, the composite weld taught herein comprises wear resistant material suspended in a weld matrix, the wear resistant material being provided on a macroscale that is, in grit-like form. Irrespective of the proposition that such composites may sometimes be referred to as alloys, it will be appreciated by persons skilled in the art that there is a distinction between alloys which are 18

O

S homogeneous on a macroscale and composite materials which are non-homogeneous on a S macroscale.

O Although the invention has been described with reference to specific examples, it will be C appreciated by persons skilled in the art that the invention may be embodied in other forms within the broad scope and ambit of the invention as herein set forth and defined by the following S claims.

Claims (9)

1. A ground cutting tool including:- ,IC a tool body having one or more cutting elements formed from ADC and embedded in said tool body to provide an exposed portion of said one or more cutting elements protruding C, from said tool body, and an outer face of said tool body, at least some of said outer face being formed from an abrasion resistant material. O 2. A ground cutting tool according to Claim 1, wherein said abrasion resistant material is in the form a hardfacing comprising one or more beads of composite weld having supported therein a wear resistant material in grit-like form disposed about and forming the outer face of the tool body.

3. A ground cutting tool according to Claim 1, wherein said abrasion resistant material is in the form of one or more rings of hard-wearing material formed onto a tool blank

4. A ground cutting tool according to Claim 1, wherein said abrasion resistant material is provided about an outer circumferential face of a sleeve into which the or each cutting element is mounted. A ground cutting tool according to Claim 1, wherein the entire tool body is formed from said abrasion resistant material.

6. A ground cutting tool according to Claim 2, wherein said beads are provided in a circumferentially running direction about said tool body.

7. A ground cutting tool according to Claim 2 wherein said tool body includes a tool blank having formations for overlaying one or more layers of said composite weld.

8. A ground cutting tool according to Claim 7, wherein said tool blank includes one or more lands upon which said hardfacing is formed. t

9. A method of forming a ground cutting tool including:- providing a tool body; O providing one or more cutting elements formed from ADC; ,Ic embedding said one or more cutting elements in said tool body to provide an exposed portion of said one or more cutting elements protruding from said tool body; and providing an outer face of said tool body, at least some of said outer face being formed from an abrasion resistant material. (-i A ground cutting tool including:- 10 a tool body of substantially circular cross-section formed into a shank for mounting the tool body and two or more engagement portions for engaging ground, each engagement portion having one or more cutting elements embedded therein, a one or more circumferentially running lands extending axially along a substantial part of said engagement portion and being arranged in substantially axial alignment with one another; and a hardfacing on at least some of said lands, said hardfacing including one or more layers of composite weld supporting therein a wear resistant material in grit-like form.

11. A ground cutting tool including:- a tool body of substantially circular cross-section formed into a shank for mounting the !0 tool body and an engagement portion for engaging ground, the engagement portion having one or more cutting elements embedded therein, one or more circumferentially running lands extending axially along a substantial part of said tool body and three or more transection elements embedded in said engagement portion, said transection elements being of substantially planar form and extending radially outward from the one or more cutting elements and axially from the tip of the engagement portion, said transection elements being formed from material which is more wear resistant than the material in which they are embedded; and a hardfacing on at least some of said lands, said hardfacing including one or more layers of composite weld supporting therein a wear resistant material in grit-like form.

12. A ground cutting tool substantially as hereinbefore described with reference to any one of the accompanying drawings. 21 O O -q- o Dated this 2 2 n d day of October 2006. N, THE TRACK SHOP PTY LTD By their Patent Attorneys SAHEARN FOX