CA1074779A

CA1074779A - Earth-boring drill bits

Info

Publication number: CA1074779A
Application number: CA282,374A
Authority: CA
Inventors: Bruce H. Walker; David S. Rowley; Coy M. Fielder
Original assignee: Christensen Inc
Current assignee: Norton Christensen Inc
Priority date: 1976-07-12
Filing date: 1977-07-08
Publication date: 1980-04-01
Also published as: NO149181C; SU946410A3; BE856697A; NL7706233A; DE2730602C3; MX144441A; DE2730602B2; DE2730602A1; NL172477B; FR2358537B1; NL172477C; JPS539205A; NO771015L; AU504704B2; FR2358537A1; BR7704531A; NO149181B; JPS5614832B2; GB1556562A; AU2639577A

Abstract

EARTH-BORING DRILL BITS

Abstract of the Disclosure The invention relates to the design of earth bore-hole drill bits employing shaped preform cutters containing hard abrasive materials such as diamonds.

Description

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Background_o~ the Invention Diamond bits employing natural or synthetic diamonds positioned on the face of a drill shank and bonded to the shank in a matrix of a secondary abrasive, such as tungsten 5 carbide, by means of a metal bond, are well known in the art.
There are two general types: One in which the diamonds usually of very small gage are randomly distributed in the matrix; another type contains diamonds, usually of larger size, positioned in the surface of the drill shank in 10 a predetermined pattern referred to as surface set. (See U.S. Patents 3,709,308; 3,825,083; 3,871,840; 3,757,878; and 3,757,879.) Drill bits formed according to the above procedure are subject to damage when used as bore-hole drill bits. Such 15 damage results from localized destruction of the diamond matrix complex. When this occurs, the useful life of the bit may be terminated and extensive repairs or salvage of the bit is required by separating the diamonds and tungsten carbide from the steel shank.
20 Statement of the Invention Instead of using individual diamond particles distributed either in random orientation in the secondary abrasive matrix, such as tungsten carbide with a metallic bonding agent, or as surface set bits, we employ a cutter 25 preform. The cutter preform may be made as described in U.S.
Patent 3,745,623 or by molding mixtures of diamond particles, secondary abrasive particles, and particles of a metallic bonding agent employing the techniques of the above patents in suitable shaped molds, for example, by the hot press methods 30 described in Patents 3,841,852 and 3,871,840. We prefer a `~ :

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preform formed as in Patent 3,745,623. According to our invention, the preforms are mounted in the body of the drill bit, such as described above, to be placed in spaced relation from the part adjacent to the central axis to close to the gage of the bit. The arrangement of the preforms in the bit is such that on rotation o~ the bit about its axis substantially the entire surface of the earth traversed by the bit on rotation is engaged by the preforms.
In order to assure that the preforms can cut without undue stress, the preforms are set at a negative rake and the preforms are backed by an adjacent portion o~ the body of the bit to take the thrust on the preform cutters imposed during drilling. Bending stresses are thus minimized and in a practical sense avoided in the preforms.
Provisions are made to move the cuttings away from the preforms. The drilling fluid is passed through a central bore to provide a flushing action. For this purpose, channels are provided in fluid communication with the bore in front of the cutter preforms. The channels extend across the face of the bit from the central bore to the gage of the bit. While, for some uses, the channels may be omitted, the channels, as in our preferred embodiments, aid in establishing the bit hydraulics to clean the face of the bit. The cutters may be set with a zero but preferably with a negative side rake~ so as to provide for a snowplow effect to move the cutting to the gage of the bit. The channels in our preferred embodiment extend in front of the cutter preforms which are oriented as -described above. The orientation of the rake and the fluid through the channels move the cutting to the annulus between the bit and bore hole to be carried up the annulus to the

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surface. The preform cutters are carried in sockets positioned in the base of the drill bit, preferably in a drill bit, coated, for example, with metal-bonded secondary abrasives having a hardness value less than diamonds. Coating of the drill bit with such hard material is conventional, but in such case, the diamonds are mounted as described in the above patents. We prefer to prepare sockets in the drill, so oriented about the drill bit, and with the preforms so oriented in the sockets, as to give the pattern previously referred to.
The cutters according to our invention may be mounted in sockets formed in the matrix-coated drill, so formed as to orient the preforms which are mounted by insertion into the sockets, to provide the pattern and rakes described above.
Instead, the preforms may be mounted in receptacles positioned on studs which are inserted in sockets formed in the matrix-coated drill. The studs and sockets are formed so that on insertion of the studs in the receptacles, the preforms are oriented in the pattern and with the rakes described above.
We prefer to use the bits carrying the studs in relatively soft formations and to use the preforms mounted directly in the sockets for hard formations.
The arrangements, both that employing preform cutters mounted on studs positioned in the sockets and the preforms mounted directly in the sockets formed in the face of the bit, have the advantagè that the cutters may be backed so that they are in compression rather than in tension due to binding~
We prefer to arrange the cutters in an array in the manner and for the purposes described above and more fully described below and to arrange the fluid channels to be ~0 positioned in front of the cutter arrays. This arrangement ~ 7~
controls the flow pat~ern across the cut~ing surface in immediate proximity of the cutters and aids in removing cuttings and flushes them away from the cutters.
One of the advantages of the mounted preform cutters according to our invention is that, on destruction or other damages to a preform, the damaged preform may be removed and replaced without requiring the salvage of the entire bit.
The above design of the diamond bit of our invention is particularly suitable when using synthetic diamonds, such as are employed in the formation of the cutting elements described in Patent 3,745,623. Such diamonds are weakened to a much greater degree than are natural diamonds at temper-atures normally employed in production of drill bits by processes, such as are described in United States Patents

3,709,308; 3,824,083; and 3,757,879. Such processes entail exposing diamonds to temperatures which are used in the infiltration or hot press processes of the aforesaid patents.
The temperatures employed in such procedures are in the order of above about 2000 F., for example, 2150F. Such temperatures, while suitable for natural diamonds, are excessive for synthetic diamonds and weaken them excessively.
The design of the drill bit of our invention permits the use of synthetic diamonds as well as natural diamonds in that the preforms using synthetic diamonds or natural diamonds may be formed at temperatures suitable for synthetic diamonds as is described in said Patent 3,7~5,623.
The design of our invention thus permits the formation of the drill bit body at high temperatures and the formation of the preforms when using natural diamonds by the high 0 temperature methods previously described or when using , .

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synthetic diamonds by forming them at lower temperatures, ~or example, as described in Patent 3,745,623. Thus the preforms employing, for example, natural diamond~ may be formed by the hot press method referred to in Patent 3,871,840 employing molds of suitable shape to form the preform of the desired geometric configuration.
Other features and objects of the invention will be understood by reference to the drawings of which:
Figure 1 is a view partly in elevation and partly in quarter section of an earth-boring bit according to our invent.ion;
Figure 2 is a plan view of the bottom of the bit taken on line 2-2 of Figure l;
Figure 3 is a fragmentary section taken on line 3-3 of Figure 1 with parts in elevation;
Figure 4 is a section taken on line 4-4 of Figure 3;
Figure 5 is a section on line 5-5 of Figure 4;
Figure 6 is a fragmentary detail of Figure 2 showing the side rake;
Figure 7 is.a fragmentary section on line 7-7 of Figure 2;
Figure 8 is a section similar to Figure 1 prior to installation of the studs;
Figure 9 is a vertical section of another form of a bit according to our invention;
Figure 10 is a view taken on line 10-10 of Figure 9;
Figure 11 is a fragmentar~ detail on line 11-11 of Figure 10;
Figure 12 is a section taken on line 12-12 of Figure 11;
Figure 13 is a section taken on line 13-13 of Figure 12.
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In the form of Figures 1-7, the tubular shank 1 of the bit is of conventional shape and is connected to the drill collar 2 and is coated internally and externally of the shank 1 with a hard material 3, for example, such as metal-bonded tungsten carbide to form the face 4 of bit section and the stabilizer section 5, as in prior art diamond drill bits used or earth bore-hole drilling. The hard coating 3 of the bit extends circumambiently about the central axis of the bit and is positioned between the gage 6 of the bit and across the face of the bit. The hart coating at 5 extends to form the gage 6.
Sockets 7 are positioned in the coating 3 spaced as herein described in the face 4 in accordance with a pattern for the purposes herein described. The cutters 8 are mounted 1~ in the receptacles 9 carried on studs 14 positioned in sockets 7. We prefer, especially where the cutters are mounted in studs as described below, to form the face of the bit in steps 26 extending circumambiently about the :Eace of the bit, as is described in a copending Canadian application filed jointly with 2a applicants and another, S.N. 288,987. As is shown in the copending application and in Figures 1, 2, 7, and 8, the steps extend as a spiral from an intermediate portion 10 of the bit 1 to the portion of the face of the bit adjacent the gage 6, as will be more fully described below. The sockets in the case of the bit, shown in said copending application and in Figures 1-7, are formed in the angle between 1 and 31 of one step and the rise 30 of the adjacent step.
In the form shown in Figures 1-7, each of the cutters is positioned in a stud-mounted receptacle. The studs 14 are .i ., '7~
formed with a receptacle 9 whose axis 16 is at an obtuse angle to the central axis of the stud 14. The stud is formed of steel or material of similar physical properties and ls coated with a hard surface 18 coating formed, for example, of material of the same kind as is used in the coating 3. The stud may be held securely in the socket by an interference fit or by brazing or other means of securing the stud in the socket.
Secured in the receptacles as by soldering or brazing are preform cutters 8 formed as described above. They may be of any desired geometric configuration to fit into the receptacle. For convenience, we prefer cylindrical wafers whose axial dimension is but a minor fraction of the diameter o~ the wafer. The acute angle 20 thus establishes a negative vertical cutting rake.
The studs 14 are provided with indexing means, for example, flat sections 21 tFigure 4) so as to orient the studs as is described below. Positioned in the sockets 7 are means which cooperate with indexing means on the studs, for example, the flat section 22 (Figure 4). The indexing means are arranged to position the studs in a longitudinal array extending from adjacent the gage 6 across the face 4 towards the axis of the bit.
The aforesaid longitudinal array extends circumambiently about the bit spaced from each other as is illustrated in 25 Figures 1 and 2. The arrays are separated by fluid channels ~ ;
23 which extend from the central portion 10 of the bit to the gate 6 of the bit at the stabilizer section 5 where it joins the grooves 24. The studs are positioned in each array spaced from each other in said arrays. The cutters are arranged in 0 each longitudinal array so that they are in staggered ..

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1 position with respect of the cu-tters in adjacent array. The cutters overlap each other in the sense that the portion of the earth, not traversed by a cutter of one array, is traversed by a cutter in the following array during rotation.
The indexing flats in the socket and stud are positioned so that the cutting face of the preform cutters in each array face in the same angular direction as the intended direction of rotation of the bit. The bit is designed for rotation in the usual manner by a clockwise rotation of the drilling string connected to the collar 2.
This arrangement assures that all sections of the surface to be cut by the bit are traversed by a series of `
cutters during each rotation oE the bit.
A convenient arrangement is to position the sockets and studs in a generally spiral configuration extending from the center of the bit to the gage.
While the studs may be mounted in sockets formed in the face of the bit in any geometric form, for example, that shown in Figures 8-12 or in any form employed in the prior art, we prefer to mount the studs in sockets formed in the face as described and claimed in the copending Canadian application, S.N. 288,987.
The form is shown in Figures 1 and 2; the face is formed with a central portion 10 having a substantially ~S circular perimeter 25. The portion of the face of the bit extending from the perimeter 25 to the gage 6 of the bit is formed with steps 26 in a spiral configuration. ~s is shown in Figure 2, the spiral 27 starts at the tangent 29 at the rise 30 and traverses the face 4 as a spiral to form the lands 31.

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The sockets 7 are formed in the face of the bit with the axis of the sockets intersecting the apex of the angle between the rise and the land oE the steps. The geometry of this arrangement allows the bit to constitute a jig to assure that the sockets will be in a spiral configuration.
The positioning of the studs in the angle between the rise and the land aids in the protection of the preform.
Impact loads are absorbed by the lands and rises where the studs are located.
As a result of this arrangement, on rotation of the bit, the preform cutter elements follow each other to cut the spaces which had been missed by the cutters of the preceding array. The result is that all portions of the earth are traversed by a series of cutters during each rotation.
In order to facilitate the cleaning of the bit and prevent clogging between the cutters, we provide, as described above, fluid channels to join the grooves 24 in the stabilizer section. The fluid channels are in the form of grooves positioned between ad~acent longitudinal arrays of cutters and extending adjacent to the face of the cutters in the array. Nozzles 3~ (see Figures 1, 2, and 7) are positioned in the body of the face to connect with each channel. The nozzles are connected by bores 35 with the central tubular bore of the shank 1. They are positioned at various radial distances from the center around the bit in a ~enerally spiral arrangement.
The flushing action of the fluid in the channels 23 may be sufficient to clean the cutters and prevent clogging.
In such case, the face of the cutters may be set at a zero rake, that is, perpendicular to the direction of rotation or _ 9 _ ~f'` -' , :. . ' . "

with the negative side rake described below. Drilllng fluid, conventionally used, is discharged from the nozzles 34 into the channels 23 to flush cuttings, and flows upwardly by the stabilizer 5 directed by grooves 24 through the annulus between the d~ill string and the bore-hole wall to the surface.
To facilitate the discharge of the cuttings and to clean the bit, the cutters, in addition to the vertical negative rake shown in Figure 3, may be set in a horizontal rake as shown in Figure 6. In order to assist in movir.g the cutting to the gage ~ o~ the bit, we prefer to orient the cutters so that the cutting surfaces of the preform cutters 8 are rotated about a vertical axis counterclockwise to provide a negative sideways rake 36 (see Figure 6).
The negative horizontal rake angle 36 may be, for example, about 1 to 10, preferably about 2. The effect of the negative sideways rake is to introduce a snowplow effect and to move the cuttings to the gage of the bit where they may be picked up by the circulating fluid and carried up the grOoves 24 of the stabilizer 5. The vertical negative rake angle 20 may be from about 4 to about 20.
As will be seen, the space taken by the receptacle and the preforms makes impractical the positioning oF a large multiple of preform cuttiny elements at the center of the bit.
The portion may thus produce a core. This is aggravated if any of the preforms are lost from the central portion because of damage occurring during use.
We prefer to supplement the cutting effect at the center by including diamonds 37, either in a pattern or in random distribution~ We also provide for diamonds positioned at the gage where the side impacts during drilling are large, ' ~

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employing conventional techniques in setting the diamonds as described above.
For practical reasons, this portion of -the bit is first formed before setting of the preform cutters.
One of the features of the above construction is that, should any one or more of the preform cutters be destroyed or the studs damaged, they may be removed; and a new stud and preform may be inserted.
The form of cutters of our invention, which is the presently preferred form, especially for use in hard formations, employs preforms mounted directly in position on the face of the bit.
As shown in Fi~ures 9 and 10, the bit is formed by a shank 101, coated as in the form of Figure 1 by a hard coating 15 102. The face of the bit 103 is of generally conical shape facing into the central opening 104. As is shown in Figure 10, the central opening may be the form of a threefold manifold with three branches 10~. The mani~olds connect with channels 105 extendin~ to the gage 106. They connect with the grooves ~0 107 in the stabilizer section 108.
On the face of the bit are formed protuberances 109 spaced in longitudinal arrays about the face of the bit. Each of the protuberances carries an extension 110 and a socket 111 in which is mounted a preform cutter 112 of the above 25 composition. As is shown in Figures 11, 12, and 13, the cutters are positioned in sockets 111 and at the extensions 110 which are formed on the face of the bit and which act as receptacles. The entire back of the preform i5 supported by the socket and the extension 110 which acts as a receptacle to receive the preform.

,'.'-. - . '. ~', ' . ' As in the case of the cutters of Figures 1-7, the receptacles support the cutters with both vertical and horizontal rakes as is described for the cutters of Figures 1-7. As is shown in Figure 12, the preform is mounted with a vertical negative rake 120 and, as is shown in Figure 11, with a horizontal negative rake 136. The rake angles may be as described above for the forms of Figures 1-8.
The protuberances are spaced in a longitudinal array from each other adjacent the channels 105, about the face of the bit. The protuberances and ~heir contained receptacles are spaced from each other in arrays, as is described for the form of Figures 1-8~ The cutters positioned in the receptacles in the protuberances are thus arrayed in a staggered overlapping arrangement with respect of the cutters in the protuberances lS in adjacent longitudinal arrays similar to the arrangement of the stud supported preforms. The cutting surface of the cutters faces in the same angular direction as the direction of rotation of the bit. Fluid channels 105 are positioned in front of the array of cutter 113. The fluid which is fed through the central bore of the tubular drill shank 101 discharges into the manifold 104 and thus through the channel 105 to flush the cuttings, which have been moved towards the gage, upward into the annulus.
In both forms, the cutters are preforms which may be replaced as they are damaged or lost. They permit the cutters to be placed in receptacles formed in the hard coating of the diamond bit, in a predetermined array to efficiently cut an entire surface. The preforms may use fine primary abrasives such as diamonds or equivalent hard abrasive particles in a preform arranged in a predetermined array on the bit. The use : '- ' : ..

'7~3 of such preforms mounted in a pattern to cover substantially the entire surface to be cut bu-t which would permit replacement o~ individual damaged cutters, has the advantage that a worn bit may be readily repaired and need not be discarded or require salvage. In order to permit the mounting of preforms which tend to be brittle in a bit where they will meet impact forces, our invention provides for a support which preserves the integrity of the preform.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An earth-boring bit comprising a metallic shank having a fluid passage, one end of said shank being coated with a hard material bonded to said end and forming a face of said bit; preformed sockets in said hard material of said face, preform cutters mounted in said sockets; each of said cutters including a plurality of abrasive particles bonded into a preform, said preform cutters each being formed with a cutting face and a back, each of said sockets embracing sides of said cutter mounted therein between said cutting face and back, said hard material at said sockets overlying and being contiguous said backs and extending rearwardly therefrom, whereby said material adjacent said sockets transmits thrusts through said backs to said cutters during rotation of the bit.

2. An earth-boring bit comprising a metallic shank having a fluid passage, one end of such shank being coated with a hard material bonded to said end and forming a face of said bit, preformed sockets in said hard material of said face, pre-formed cutters removably mounted in said sockets, said preform cutters being of a shape to fit into said sockets, each cutter having a cutting face and a back, each of said sockets embracing sides of said cutter mounted therein between said cutting face and back, said hard material at said sockets overlying and being contiguous said backs and extending rearwardly therefrom, whereby said material adjacent said sockets transmits thrusts through said backs to said cutters during rotation of the bit.

3. An earth-boring bit comprising a metallic shank having a fluid passage, one end of said shank having a coating of hard material bonded to said end and forming a face of said bit, a plurality of preformed sockets in said hard material extending in spaced relation with respect to each other across the face of said bit, cutters removably mounted in said sockets, said sockets and cutters mounted therein being arranged in a plurality of arrays spaced longitudinally from each other about said face, each of said cutters including a plurality of abrasive particles bonded into a preform, said preform cutters each being formed with a cutting face and a back, each of said sockets embracing sides of said cutter mounted therein between said cutting face and back, portions of said hard material providing protuberances extending from said sockets, said protuberances and hard material at said sockets overlying and being contiguous said backs and extending rear-wardly therefrom, whereby said protuberances and said hard material adjacent said sockets transmit thrusts through said backs to said cutters during rotation of the bit, said pro-tuberances being disposed at an angle from said cutters to the adjacent face of the bit.

4. The bit of claim 1, said preform cutters being of a shape to fit into said sockets with the back of said cutters supported by said hard material at a rake angle, said hard material extending from said back at an angle to the adjacent face of said bit in thrust transmitting relation between said cutters and said material.

5. An earth-boring bit comprising a metallic shank having a fluid passage, one end of said shank being coated with a hard material bonded to said end and forming a face of said bit, preformed sockets in said hard material, said sockets being spaced from each other in a plurality of arrays, preform cutters removably positioned in said sockets, said cutters comprising abrasive particles bonded into a preform, said cutters in each array being arranged in staggered relation to the cutters in an adjacent array, said preform cutters each having a cutting face and a back, each of said sockets embracing sides of said cutter mounted therein between said cutting face and back, said preform cutters being of a shape to fit into said sockets at a rake angle with the back of each cutter supported by said hard material, said hard material at said sockets overlying and being contiguous said backs and extending rearwardly therefrom at an angle to the adjacent portion of said face, whereby said material adjacent said sockets transmits thrusts through said backs to said cutters during rotation of the bit, said cutters being positioned in longitudinal arrays across the face of the bit, the cutting faces of said cutters in each array all facing in a forward direction.

6. In an earth-boring bit comprising a metallic shank having a fluid passage, one end of said shank being coated with a hard material bonded to said end and forming a face of said bit, said hard material extending from a central portion of said bit to the gage of said but, a plurality of fluid channels positioned in said face and extending to the gage of said bit, said fluid channels communicating with said fluid passage, the improvement which comprises preformed sockets in said hard material, protuberances in said hard material, pre-form cutters in said sockets arranged in longitudinal arrays each of said cutters including abrasive particles bonded into a preform, said preform cutters each having a cutting face and a back, each of said sockets embracing sides of said cutter mounted therein between said cutting face and back, the back of each cutter being supported by the hard material adjacent to said socket, said adjacent material including said protuberances extending from said back at an angle to the adjacent face of said bit, the cutting faces of the said cutters in each array facing in a forward direction, said fluid channels extending in front of said preform cutters.

7. In an earth boring bit comprising a metallic shank having a fluid passage, one end of said shank being coated with a hard material bonded to said end and forming the face of said bit extending from a central portion of said bit to the gage of said bit, a plurality of fluid channels positioned in said face and extending to the gage of said bit, said fluid channels communicating with said fluid passage, the improvement which comprises preformed sockets in said hard material, preform cutters removably positioned in said sockets, said cutters being spaced apart in a plurality of longitudinal arrays, said cutters in one array being arranged in staggered relation to the cutters in another array, each of said cutters including abrasive particles bonded into said preform cutters, said preform cutters each including a cutting face and a back, each of said sockets embracing sides of said cutter mounted therein be-tween said cutting face and back, said preform cutters being positioned in said sockets at a negative rake angle with the back of said cutters supported by the hard material adjacent to said sockets, said adjacent hard material including a pro-tuberance extending from the back of each cutter in thrust transfer relation to said cutter, said fluid channels exten-ding in front of said preform cutters.

8. The bit of claims 1, 2, or 3, the said preforms comprising bonded diamond particles.

9. The bit of claims 5, 6, or 7, the said preforms comprising bonded diamond particles.

10. The bit of claims 1, 2, or 3, the said preforms comprising bonded synthetic diamond particles.

11. The bit of claims 5, 6, or 7, the said preforms comprising bonded synthetic diamond particles.

12. The bit of claims 1, 2, or 3, the said preforms comprising bonded diamond particles and the said hard material extending from said fluid passage to the gage of the hit, diamonds in said hard material adjacent said fluid passage and diamonds in said hard material at the gage.

13. The bit of claims 5, 6, or 7, the said preforms comprising bonded diamond particles and the said hard material extending from said fluid passage to the gage of the bit diamonds in said hard material adjacent said fluid passage and diamonds in said hard material at the gage.

14. The bit of claim 1, 2, or 3, the said preforms com-prising bonded synthetic diamond particles and the hard mater-ial extending from said fluid passage to the gage of the bit, diamonds in said hard material adjacent the said fluid passage and diamonds in said hard material at said gage.

15. The bit of claims 5, 6, or 7, the said preforms com-prising bonded synthetic diamond particles and the hard mater-ial extending from said fluid passage to the gage of the bit, diamonds in said hard material adjacent the said fluid passage and diamonds in said hard material at said gage.