CA1061325A - Diamond cutter rock bit with penetration limiting - Google Patents
Diamond cutter rock bit with penetration limitingInfo
- Publication number
- CA1061325A CA1061325A CA263,992A CA263992A CA1061325A CA 1061325 A CA1061325 A CA 1061325A CA 263992 A CA263992 A CA 263992A CA 1061325 A CA1061325 A CA 1061325A
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- Canada
- Prior art keywords
- cutters
- diamond
- rock
- rolling cone
- bit
- Prior art date
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Abstract
Abstract of the Disclosure A rock bit for recovering core samples is described, along with variations for drilling oil wells or the like.
In each of these embodiments a plurality of diamond cutters are mounted on the bit body for cutting rock by a shearing action. Each diamond cutter is in the form of a thin diamond plate bonded to a carbide slug that is inserted into the bit body. Means are also provided for limiting the depth of penetration of the diamond cutters into the rock formation being drilled preferably in the form of rolling cone cutters having a plurality of carbide inserts protruding from Their surfaces. The protrusion of the carbide inserts from the surface of the cutter cones is less than the length of the diamond plate. This limits the depth that the diamond can penetrate in the rock and inhibits damage. Typically the diamond cutters are mounted for cutting one portion of the hole area by shearing action and the rolling cone cutters are mounted for cutting another portion of its area by chipping-crushing action.
In each of these embodiments a plurality of diamond cutters are mounted on the bit body for cutting rock by a shearing action. Each diamond cutter is in the form of a thin diamond plate bonded to a carbide slug that is inserted into the bit body. Means are also provided for limiting the depth of penetration of the diamond cutters into the rock formation being drilled preferably in the form of rolling cone cutters having a plurality of carbide inserts protruding from Their surfaces. The protrusion of the carbide inserts from the surface of the cutter cones is less than the length of the diamond plate. This limits the depth that the diamond can penetrate in the rock and inhibits damage. Typically the diamond cutters are mounted for cutting one portion of the hole area by shearing action and the rolling cone cutters are mounted for cutting another portion of its area by chipping-crushing action.
Description
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1 DIAMOND CUTTER ROCK BIT WITH PENETRATION LIMITING :: :
., ,,, ' .:, Back~Lround Two principal types of rotary drill bits are empLoyed ` ::
25 for rock drilling for oil wells7 recovering core samples, :
and the like. One type uses rolling cone cutters mounted -~
on the body of the drill bit so as to rota~e as the dx ill .
bit is rotated. The angles o~ the cones and the bearing pins on which they are mounted are aligned so that the _ .s"''' '' , '.
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~ ~ 6~3 Z 5 1 cones essentially roll on the bot~om of the hole without gross slippage. Sometimes ~he cones are deliberately skewed to enhance gouging actio~ in some rock types. One type of rolling cone cut~er is an integral body of hardened steel with teeth formed on its periphery. A~other ~ype has a steel body with a plurality o tungsten carbide or ~imilar inserts o~ high hardness that protrude from the surface of the body somewhat like æmall knobs. As the rolling cone cutters roll on the bottom of ~he hole being drilled, the teeth or carbide inser~s apply a high compressive load to the rock and fracture it. The cutting action in rolling cone cutters i8 typically by a combination of crushing and chipping. ~he cuttin~s from a rolling cone cutter are typically a mixture of moderately large chips and fine 15 particles. ``
Another basic type of rotary rock drilL is a drag bit.
Some o~ these have steel or hard faced teeth, but primarily they are set diamond drills. Typically in a set diamond drill the face i8 coated over r,luch of its area with a hard 20 material in which are embedded or "set" numerous diamonds.
The diamonds protrude from the surface of the matrix a short distance (typically no more than a few hundredths of an inch in a new drill~ and when the drill is used they rub on ~he rock, abrad~ng shallow tr~cks and cu~ting ;~
primarily by a combination of compressi~e and shearing action. In most cases set diamonds, due to their ~mall size, bear loads of abou~ 100 to 200 pounds per diamond.
In many set d~amond bits9 rounded d~amonds are selected to give best resistance to compressive forces~
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` ~ 10 61 32 5 l The depth of penetration o~ the set diamonds is ord~narily determined by the weight on the bit, the quantity of diamonds -^
on the bit and heat limitations.
Combinations of drag bits and rolling cone bits have S been proposed. For example, U.S. Patent No. 3,174,564 to E. A. Morlan for a "Combination Core Bit", has a cylindricàl crown encrusted with set diamonds for cutti1lg an annulus ~ -around a core. The 8et diamonds protrude from the matrlx tiny distances in the con~en~ionaL man~er. A pluraLity of rolling cone cutters with carbide inserts are mounted in special recesses around the cylindrical crown for cutting ;~
an outer annulas of considerably greater area than ~he inner annulus cut by the diamonds. The set d~amonds are ~;~
used for their fine ahrasive action in trimming the core 15 and thereby minimizing breakage. Most of the cut~ing i~ ;
done by the rolling cone cutters.
In conventional æe~ diamond drills the depth of l penetration of each diamond is only a few mils but rapid penetration rates can be obtained because of the large number of diamonds set on the face of the bit. Penetration rate i8 limited 80 that there i8 minimal wear of the mat~ix in which the diamonds are mounted. Rock drilling by set diamond drills i~ analagous to grind~nc with a grinding wheel made of small abrasive particles. The cu~tings from 2S a se~ diamond bit are in the ~orm Qf extremely fine par~icles~ -U,S, Patents 1,731,262 to Phipps and 2,054,277 to Wright `~
also haYe combinations of drag bits and rolling cone cut~ers. `;
These bits have Large steel drag teeth and steel rolling cone cutters hence are rather lim~ted in application.
Only very soft formations can be cut . . j . . . .. . . ..
' -~ 10~13Z5 1 ¦ eff~ciently with such a design and they are impractical for ¦ deep wells where it is desirable ~o cut long distances `~
before changing the rock bit.
¦ Recently a new product ha~ become a~ailable that 5 ¦ penmi~s a new ~ype of rock bit~ The product is a diamond cutter described in greater detail hereinater. Broadly, the diamond cutter has a wafer or plate of diamond about 0.020 inch thick and 0.33 inch in dlameter bonded to a tungste~ carbide slug. This produc~ was developed by 10 General Electric and i8 c~mmercially available under `~
their trademark COMPAX. The slug can be inserted in a drill bit body ~o that the diamond plate protrudes thererom at the proper angle for cutting rock. The cu~ting action by these diamond cutters is by shearing the rock much in the 15 manner o~ conventional machining with cutt~ng tools rather than the gr~nding-like action of con~entional set di~mond drilLs. Instead o f$nely ground material, much o~ the cut rock emerges from the drilled hole 88 appreciable si~e chips, s~mewha~ like th~se from a rolling cone 20 cutter.
. A rock drlll having such diamond cutters protruding from ~t8 face has been built by General Electric. Such bits have demonstrated good penetration rates in a variety of rocks ~nd very long lifetime. So~e problems have been 25 noted u~der adveræe conditions due to breakage of the diamond cu~ter~. This appears to be a par~icular problem in interspersed for~ations where there are sudden changes between relatively soft and relatively hard types o rock, i ' :
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l and most particularly when the dip of the interspersed formation is steep relative to the hole being drilled.
When a rotary rock bit is being used, a select~d ~-weight is appl~ed to it by the weight of the dri1l string 5 in the hole above it, as con~rolled by the drilling rig. -The weight applied to the bi~ i8 adjusted depending upon the type of rock being trilled. Rapid drilling weigh~
ad~u~tment ~o account for differences in rock types in lnterspersed formatlons i8 not feasible. This means ~0 that penetration may be too much in one rock type or too little in the other. This problem is serIous in ordinary set diamond driLls bu~ i~ not significant in rolling cone drills. It also can be signiicant in drills with diamond cutters where a limited number of cutters are engaging the rock during drilling~
Drills with diamond cutters appear particularly sensit~ve to overloading which can break the diamond cutters. Sudden changes in rock hardness may also apply an impact Load on the diamond cutter and initiate failu~e.
It may, the~efore, be necessary in interspersed formations to use a drilling load that iB appreciably less than -~
optimum for best penetration to protect the bit with `
diamond cutter~. It is desirable to provide a means for protecting the diamond cutters during drilling to inhibit damage to the diamond cutters ~o that max~mum penetration rates cnn be ach~eved.
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In accordance with the present invention there i5 ~` , provided a rotary rock bit comprising: a blt: body having a longitudinal axis of rotation; a plurality of diamond cutter~
each having a cutting edge protruding from the bit body for en~aging the bottom of a hole being drilled at a selected rake angle for shearing rock in a plurality of paths concentric with the axis of the bit body; and means for limiting depth of penetration of the diamond cutters into the rock to les~
than the distance of protrusion of the diamond cutters from the bit body comprising a plurality of rolling cone cutters mounted on the bit body for rotation upon rotation of the bit body, each rolling cone cutter comprising a plurality of carbide inserts protruding rom the surface of the rolling cone cutter a distance less than the distance of protrusion of the diamond cutters from the hit body in the axial direction for engaging the bottom of the hole being drilled and for crushing or gouging of rock in a path çoncentric with the ~:
portion of the hole drilled by the diamond cutters.
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These and other features and advantages of the present invention will be appreciated as the same becomes better understood by reference to the follo~wing de~iled :~;
5 i description of presently preferred embodimemts wherein:
FIG. 1 is a Longitudinal cross sectilDn of a drill b~t constructed according to principles o this i~ven~ion;
FIG. 2 is an end view of the drill bit of Fig. l; ~;
FIG. 3 is a semi-schematic illus~ration o the dr~
10 ~ bit indicat~ng the relationship between the diamond cutters . ;
and rolling cone cutters thereon;
FXG. 4 is a perspective view o a dlamond cutter;
FIG, 5 i~ a semi-~chematic end ~iew o another `.
. embodiment of drill bit constructed according to principles 15 ~ of thi~ invention; ::
FIG. 6 is a semi-schematic end view of another .. ~:
embodiment of drill-bit constructed according to principles o this invention, and FIG. 7 is a semi-schematic end view of another . ~ :
20. l') embodiment o drill bl~. ~
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1 Description FIG. 1 is a longi~udinaL cross section and FI~. 2 is an end view of a core bi~ making application of both diamond cutters and rolling cone cut~ers. In Fig. 2 the S bit is ready for about the last stage of assembly, namely, insertion of the diamond cut~ers. They are omi~ted from this view to show the alignment of the holes ~n which the cutters are mounted.
As best seen in FIG. 1, it is ~onvenien~ to make 10 the bit body in several pieces and weld it together during '~
assembly. Four steel legs 10 having a general L-shape are machined and heat treated. Each o these legs includes a conven~ional bearing pin which cannot be seen in FIG. 1 since rolling cone cutters 11 are mounted on the respective ~`
pins in the conventional manner. The rolling eone cutter legs 10 are welded on a Lower bit body 12 after it has been machined. A pin blank 13 is then welded on to the body 12 ..
and a conventional oil well thread 14 i8 machined on the blank. The body and pin blank have a hollow axiaL passage L6 which, during use, receives a conventional core catcher ff for retrievlng cores cut by the core drill. At the lower end of t~e passage and above the level where cuttlng occurs there are four surfaces 17 collectively defining a cylinder h~ving only a sl~ghtly larger diameter than the diame~er of the core being made by the bit. These surfaces 17 are on the interior of four arms 18 spaced between the four rolling cone cutter~ 11. These arms support diamond cutters lS (Fig. 1).
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, . " , ' ,-, ,, 1 The diamond cutters are mounted in each of slx fldt bottomed holes 19 ~Fig. 2~ drilled in the ends of the arms 18. The holes are labeled A, B and C to indicate the r~w of cutting for each di~mond cut~er as furthler described ;.
S hereafter Each hole l9 is formed at an angle to the axis of the bit for supporting the respective diamond :
cutter in its proper position. This is indicated in FIG. 2 by showing the outer end of the hole in solid lines and also showing the bottom of the hole with the hidden 10 portions in dotted lines. The specific angular relation- .
ships are not readily determined from this drawing since : ``. -the ends of the arms 18 ln which the holes are.drilled .;
are not planar, as seen in FIG. 1. The angular relation .:.
between the holes for the diamond cutters and the axis of the bit is better ~een in FIG. 3 which i8 a semi-schematic cross section.indicating the paths of ~he cutters. ~.
FIG 4 is a per~pective view of one of the COMPAX diamond cutters available from General Electric. The diamond ~s pre~ent as a plate 21 about 0.020 inch thick and about 0.33 inch diameter. This is not a single crystal diamond but . i8 a diamond-to-diamond, bonded, polycrystalline material.
The diamond plate 21 is bonded to a tungsten carbide cylinder 22 that is in turn brazed to a tungsten carbide . slug 23.- The carbide slug has a cylindrical base about 0.503 inch diameter to give a tight press fit in a one-half inch diEmeter hole in the bi~. Soch a press fit is the sole mounting required or such a diamond cu~er. :
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lOb.:3--5 1The short carbide cylinder 22 i~ supported on the slug 23 by a buttress like portion 25 ~uppor~ing the end of the carbide cylinder, except a narrow rim about 0,01 inch wide around half the perimeter o the carbide cylinder. ~ ' S This prevents portions of the carbide slug from interfering with cutting action by the diamond pla~e 21. The carbide cylinder 22 and hence the diamond plate 21 are tilted rearwardly (downwardly in Fig. 4) relative to the axis o~ the sLug at an angle in the range of from about 5 to 15 so that 10 in use the rake ang~e or angle of attack of the diamond ,~ -plate on the rock is abou~ -5 to -15. Rake angles from about 0 to about -20 appear to be suitable. COMPAX diamond cutters with carbide 81ug9 are available in a few lengths between abou~ 0.9 and 1.155 inch to accommodate various lS desired extensions of the diamond plate from the body of the bit in which the ~lug is inserted or to accommodate `
various hole depths.
The rolling cone cutters 11 are of a generally conventional type. In this embodiment each cutter has 20 either two or three inner rows of tungsten carbide inserts 26. Each roll~ng cone cutter also has an outermost row of carbide inserts 28 generally referred to as the gage row.
The inserts in the outer~ost row are at the periphery of the hole being drilled and maintain its full gage. The 25 spacing of the inserts within the rows 26 and 28 on individual rolling cone cutters may be varied in the conventional manner to minimize tracking and maximize cutting efficiency. The inner rows of inserts 26 on the various rolling cone cutters are at different radi~l ;
30 distances from the axis of the bit. Thus, five "groovesl' are cut by the inner rows and one by the gage row so that in effect six diff~rent annular "groove6" are cut in the , 9 , ' ~ j ~
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1 bottom of the hole as ~he drill i~ operated. A variety of such patterns can be provided as are well known to those skilled in the art for assuring full ~ace cutting on the end of the hole being drilled.
FIG~ 3 is a schematic illustration for indicating the location of the various grooves cut by the inæerts in the : ~ -rolling cone cutters illustrated in FIGS. l and 2 and by the diamond cutters. In ~he left side of this view the cutting elements are projected around the axis of the bit ,;
~0 as if all lay in a common radial plane. This suggests considerable overlap of the mounting portions o~ the cutting elements that is not present in the actual structure of the ; ;
bit, The purpose is to indicate the relative locations of the cutting portions.
In this view the gage row of inserts 28 is seen to be adjacent the wall 29 of the hole being drilled. The balance of the carbide inser~s 26 ~n the inner rows of ~he rolling cone cutters can be seen to cut a major portion of the annulus between the wall 29 of the hole and a cylindrical core of rock 20 32 entering the axial passage through the bit. The three rows of diamond cutters in this embodiment are labeled 15A, 15B
and L5C ~n FIG. 3, corresponding to the holes 19A, l9B and l9C ~n FIG. 2. It will be noted that whereas there are a large numb.er of carbide inserts in each of the ~ows 26 and 25 28 cut by the rolling cone cutters, there are only two diamond cutters 15 in each of the rows A, B and C.
The innermost p~ir 15A of diamond cutters cuts a path ;~
through ~he rock adjacent the core 32 and thus trims the core to gage. The other two pairs l5B and l5C of diamond cutters 30 cut the balance of the annulus between the innermost iamond cut~er l5A and the innermost row 31 . .
' 10 , 0 6 ~ 3 2 5 1 of carbide inserts. ALthough the various inserts and diamond cutters essentially cut ln a plurality of concentric grooves on the bottom of the hole, they ~re arranged to cut in a profile that ls an essentially S continuous or smooth curve extending across ~he annulus from the core to the gage of the hole. Other arrangement~
can be provided with ~he diamond ou~ter~ leading or trailing the cutting by the carbide inserts but the illustrated arrangement is pre~erred for minimizing cracking of the core. Further, by avoiding a '~step" i~, ~he bottom of the hole, formation of excessively large chips is avoided. Large chips from the edge o~ such a step may cau~e lmpact loads on the diamond cu~ers, leading ~o failure. This principle is applicable whether a core i~ being formed or ths full face of the hole i8 being drilled.
It will be noted ~hat the curvature provided in the bottom of the hole in the arrangement illustrated in FIG. 3 is a sub~tantially smooth curve blending rather 20 gradually into the core 32 in the center and somewhat Les8 .
graduall~ into the wall 29 of the hole. Thi8 curvature without a sharp trans~tion between the annulus being cut and the core minimizes locations of stress concentrat-lon and fur~her helps avoid breakage of the core.
It is an important function of the rolling cone cutt.ers to limit the depth of penetration by the diamond .
cutters. Depth of penetration o the diamond cutters should be limited to no more than about three fourths o~ the length of the diamond plate. In this context, the ~.Le~gth . 11 ', l ¦of the plate is considered to be its extent in the directiQn ¦parallel to the hole ax~s. Since the available COMPAX diamond ¦plates are circular and about 0.33 inch diameter, it Ls pre-¦ ferred that the depth o~ penetration be no more than about S ¦ 0.25 inch. If penetration exceeds about three-fourths the ¦ length of the diamond plate s~gnificant wear of the carbide ¦ BlUg may occur~ weakening ~t to the point that it may fa~10 ¦ Further, with exces~ive penetration, drilling in interspersed ¦ formations can lead to high impact loads on the diamond ~ ¦cutters and failure. Preferably ~he depth of penetration ¦ of the diamond plate is appreciably less ~han three-four~h~
oP its length 80 that life time is determined by wear of the diamond r~ther than by the pos~ibility of fracture.
Preferably the depth of penetration i8 no more than about 0.1 inch to minimize impact l~ading on the diamond cutter in the case of interspersed formations.
The depth of penetration of the diamond cutters i~
limited by the protrusion of the carbide inserts ~rom the body of the rolling cone cutters. The carbide inserts ean penetrate into the rock during drilling no more than their protru~ion from the surfaee of the rolling cone cut~er.
The actual depth of penetration i8 ordinarily less than ~
the full protrusion of the carbide inserts since there i8 ' . .
interference by fragmented rock. Thus, by limiting the protrusion of the carbidè ~næerts from the rolling cone cutters to a fraction o~ the len~th of the diamond plate, the depth of penetr~tion o~ the d~amond plate i8 also . , , , ' 1,'' ' ,.
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1 limited.
In the arrangemen~ hereinabove described and illus~rated, the length of the diamond plate is about 0.33 inch. Protrusion of the carbide inserts from the S rolling cone cutters is about 0.25 inch. Because of interference during drilling opera~ions, the maximum ,depth of pene~ration of the dîamond plates into rock . . .. ~ , . . . .. _ _ . _ -- _ .... ._ . ..
being cut is less than the full leng~h of the carbide inserts~
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Most typically, the penetration by the diamond plate is no more than about one-~hird of their length~
It i8 also pre~erred that the protrusions of the carbide inserts on the rolling cone cutters be more than about one-fourtho the length of the diamond plate. If the protrusion is less than this amount, cut~ing b~ the diamond cutters may be unduly limited so that they do not work to full capacity and maximum penetration rate cannot be obtained.
Practic2 of this inven~ion with limitation o penetration of diamond cutters is not restricted to the core drill hereinabove described and illustrated.
FIG, 5, for example, lllu~trates in end view an . embodiment of rock bit for drilling a hole without a core uslng both rolling cone cutters and diamond cutters. In this embodiment, the center portion o~
the hole is drilled by rolling cone cutters 41 and ~he surrounding annulus is drilled by diamond cutters.
Thus, three conventional rolling cone cu~ters 41 are mounted in the center portion o a drill bit. The nose ends of these cutters are arranged to provide 3~
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~1 10613Z5 1 drilling to the center of the hole ~n ~he conven~ional ~ -manner. In essence the arrangement of the three rolling ~;
cone cutters i8 the same as in a conventional three-cone rock bit. Each of the rolling cone cutter~ has a plurality of carbide in~erts 42 protruding from its surface in a series of rows. ~referably these rows and the insert~
within them are ~taggered in a con~entional manner to assure cutting over the full face of the bit and ~bsence of tracking. : : -The bit body 40 extends radially outwardly from . :
the path cut by the rolling cone cutters. On this por~ion o~ the bit body there are a plurality of diamond cutter~ ; :
43 mounted to sweep out a number of circular paths for cutting rock in the annulus beyond the outside row o lS inserts on the cutter cones. The diamond cutters in :~
this embodiment are like those hereinabove described and illustrated in FIG. 4 but are illustrated schematically simply ~s semi-circles to indicate the direction o~ cu~ting.
In each case the diamond plate faces in a circumferential ;~
direction around the bit. Fluid ~ets 44 are provided in . the .bit body ~or directing drilling mud into the regions around the various cutters for removing rock chips from the hole. "Junk slots" 45 or c~earancë maylbe providëd around th~
body of the bit in a conventional mannër to accommodate 25 such flow. :
In rock drilling with rolling cone cutters, main~
~aining the gage o~ the hole is often one of the problems encountered. For this reason, typical carbide insert type rock ~its have a ~ull row of inserts in the gage row ~0 . ' : .
- 106:1L3Z5 1 on each rolling cone cutter and the inserts are typically closely spaced to best a~sure a ~ull gage hole throughout the life of the bit . The gage row is subject to considerable wear because of drag of the carbide inserts on the wall o~
the hole. Carbide inser~s are effeckive in the ch~pping-crushing action in the bottom of the hole and less effective in drag on the sides. Wear on the gage row inserts ean cause tight hole~ giving later difficulties in installing casing or running new tools in the hole.
~0 Many of these problems are avoided in an embodiment as illustrated in FIG. 5 since the outermost row o~ inserts on the rolling cone cutters 41 are not relied upon to define the gage of the hole. The hole gage is assured by the outermost row of diamond cutters 43 which are appropriately designed for drag cutting as hereinabove described. Since these diamond cutters are provided on a relatively large diameter portion of the bit, a substan~ial number may be used so that wear on each is minimized and accidenta7 damage to some of the inserts will not deleteriously aect operation of the bit. If desired a single row of diamond inserts may be prov~ded on the gage of an otherwise conventional three cone bit. Thus the hole can essentially be reamed to fulL gage by the diamond cutters while the main downhole cutting is by rolling cone cutters.
In the illustrated arrangement, the bit body 4~ ~as three legs extending down-hole so that the diamond cutters b~3 form a cut that has a proile that i~ essentially a continuation of the profile made by the rolLing cone cutters 41. Thus the bottom o~ the hole is in the form 3~ :
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l of a series of concentric grooves without an extens~ve ~tep therebetween. This minimizes the formation of oversized chips that do not clear the face of the tool promptly and result in regrinding with con~;equent loss S of efficiency or possible damage to the diamond cutters.
If desired, the diamond cutters can lead or trail the rolling cone cutters so as to cut at a different eleva~ion in the hole.
The inserts 42 on the rolling cone cutters protrude from the facP of the respective cutter a distance less than the length of the diamond plate on the diamond cutters.
This limits the extent of penetration o~ the diamond cutters as hereinabove described. The proportions between the pro~rusion of the carbide inserts and the length of the diamond plates is preferably the same as hereinabove described. By providing such means for limiting penetration of the diamond cu~ters prolonged!
life is obtained.
FIG. 6 illustrates another embodiment of hole drilling bit constructed according to principles of thi6 invention. As illustrated in this embodiment, the bit body 51 has a plurality of diamond cutters 52 mountèd on the face thereof in an array that provides cutting over substantially ~he full face of the drill bit. A relatively small hole 53 is let in the middle ~ince drag cutting is relatively inefficient near the centerline of the bit~ A small core of rock passe~
through the hole 53 to a conventional core breaker 1~613ZS
1 (not shown) in the bit body.
The face of the drill b~t illustra~ed in FIG. 6 is not planar but preferably more resembles the surface of a donut or torus. That is, the face is relati~ely S recessed near its periphery and near the hole 53 through the center. The intermediate portion is relatlvely raised or nearer as seen in FIG. 6. Since each of the diamond cutters extends from the bit body the same diætance, the hole that is cut as the bit is used is approx~mately the complement of the lower face. Such a configuration appears desirable for best mud circulation from ~e~s 54 during drilling operat~ons.
As mentioned above, penetration of the diamond cutters into the rock being cut should be l~mited to prolong their life. There are, therefore, provided a pair of generally conical rollers 56 mounted for ~.
rotation on the bit body with minimum slippage on the bottom of a hole to minimiæe wear on the rollers. The rollers 56 are hardened steel or may be faced wi~h a hard facing materlal if desired. They do not have carb~de inserts on their faces but are essentiaLly smooth and con~igured to approximateLy con~orm to the shape of the bottom o the hole being drilled.
~he surfaces of the rollers are recessed slightly
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1 DIAMOND CUTTER ROCK BIT WITH PENETRATION LIMITING :: :
., ,,, ' .:, Back~Lround Two principal types of rotary drill bits are empLoyed ` ::
25 for rock drilling for oil wells7 recovering core samples, :
and the like. One type uses rolling cone cutters mounted -~
on the body of the drill bit so as to rota~e as the dx ill .
bit is rotated. The angles o~ the cones and the bearing pins on which they are mounted are aligned so that the _ .s"''' '' , '.
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~ ~ 6~3 Z 5 1 cones essentially roll on the bot~om of the hole without gross slippage. Sometimes ~he cones are deliberately skewed to enhance gouging actio~ in some rock types. One type of rolling cone cut~er is an integral body of hardened steel with teeth formed on its periphery. A~other ~ype has a steel body with a plurality o tungsten carbide or ~imilar inserts o~ high hardness that protrude from the surface of the body somewhat like æmall knobs. As the rolling cone cutters roll on the bottom of ~he hole being drilled, the teeth or carbide inser~s apply a high compressive load to the rock and fracture it. The cutting action in rolling cone cutters i8 typically by a combination of crushing and chipping. ~he cuttin~s from a rolling cone cutter are typically a mixture of moderately large chips and fine 15 particles. ``
Another basic type of rotary rock drilL is a drag bit.
Some o~ these have steel or hard faced teeth, but primarily they are set diamond drills. Typically in a set diamond drill the face i8 coated over r,luch of its area with a hard 20 material in which are embedded or "set" numerous diamonds.
The diamonds protrude from the surface of the matrix a short distance (typically no more than a few hundredths of an inch in a new drill~ and when the drill is used they rub on ~he rock, abrad~ng shallow tr~cks and cu~ting ;~
primarily by a combination of compressi~e and shearing action. In most cases set diamonds, due to their ~mall size, bear loads of abou~ 100 to 200 pounds per diamond.
In many set d~amond bits9 rounded d~amonds are selected to give best resistance to compressive forces~
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` ~ 10 61 32 5 l The depth of penetration o~ the set diamonds is ord~narily determined by the weight on the bit, the quantity of diamonds -^
on the bit and heat limitations.
Combinations of drag bits and rolling cone bits have S been proposed. For example, U.S. Patent No. 3,174,564 to E. A. Morlan for a "Combination Core Bit", has a cylindricàl crown encrusted with set diamonds for cutti1lg an annulus ~ -around a core. The 8et diamonds protrude from the matrlx tiny distances in the con~en~ionaL man~er. A pluraLity of rolling cone cutters with carbide inserts are mounted in special recesses around the cylindrical crown for cutting ;~
an outer annulas of considerably greater area than ~he inner annulus cut by the diamonds. The set d~amonds are ~;~
used for their fine ahrasive action in trimming the core 15 and thereby minimizing breakage. Most of the cut~ing i~ ;
done by the rolling cone cutters.
In conventional æe~ diamond drills the depth of l penetration of each diamond is only a few mils but rapid penetration rates can be obtained because of the large number of diamonds set on the face of the bit. Penetration rate i8 limited 80 that there i8 minimal wear of the mat~ix in which the diamonds are mounted. Rock drilling by set diamond drills i~ analagous to grind~nc with a grinding wheel made of small abrasive particles. The cu~tings from 2S a se~ diamond bit are in the ~orm Qf extremely fine par~icles~ -U,S, Patents 1,731,262 to Phipps and 2,054,277 to Wright `~
also haYe combinations of drag bits and rolling cone cut~ers. `;
These bits have Large steel drag teeth and steel rolling cone cutters hence are rather lim~ted in application.
Only very soft formations can be cut . . j . . . .. . . ..
' -~ 10~13Z5 1 ¦ eff~ciently with such a design and they are impractical for ¦ deep wells where it is desirable ~o cut long distances `~
before changing the rock bit.
¦ Recently a new product ha~ become a~ailable that 5 ¦ penmi~s a new ~ype of rock bit~ The product is a diamond cutter described in greater detail hereinater. Broadly, the diamond cutter has a wafer or plate of diamond about 0.020 inch thick and 0.33 inch in dlameter bonded to a tungste~ carbide slug. This produc~ was developed by 10 General Electric and i8 c~mmercially available under `~
their trademark COMPAX. The slug can be inserted in a drill bit body ~o that the diamond plate protrudes thererom at the proper angle for cutting rock. The cu~ting action by these diamond cutters is by shearing the rock much in the 15 manner o~ conventional machining with cutt~ng tools rather than the gr~nding-like action of con~entional set di~mond drilLs. Instead o f$nely ground material, much o~ the cut rock emerges from the drilled hole 88 appreciable si~e chips, s~mewha~ like th~se from a rolling cone 20 cutter.
. A rock drlll having such diamond cutters protruding from ~t8 face has been built by General Electric. Such bits have demonstrated good penetration rates in a variety of rocks ~nd very long lifetime. So~e problems have been 25 noted u~der adveræe conditions due to breakage of the diamond cu~ter~. This appears to be a par~icular problem in interspersed for~ations where there are sudden changes between relatively soft and relatively hard types o rock, i ' :
3011 "
. :-.
l and most particularly when the dip of the interspersed formation is steep relative to the hole being drilled.
When a rotary rock bit is being used, a select~d ~-weight is appl~ed to it by the weight of the dri1l string 5 in the hole above it, as con~rolled by the drilling rig. -The weight applied to the bi~ i8 adjusted depending upon the type of rock being trilled. Rapid drilling weigh~
ad~u~tment ~o account for differences in rock types in lnterspersed formatlons i8 not feasible. This means ~0 that penetration may be too much in one rock type or too little in the other. This problem is serIous in ordinary set diamond driLls bu~ i~ not significant in rolling cone drills. It also can be signiicant in drills with diamond cutters where a limited number of cutters are engaging the rock during drilling~
Drills with diamond cutters appear particularly sensit~ve to overloading which can break the diamond cutters. Sudden changes in rock hardness may also apply an impact Load on the diamond cutter and initiate failu~e.
It may, the~efore, be necessary in interspersed formations to use a drilling load that iB appreciably less than -~
optimum for best penetration to protect the bit with `
diamond cutter~. It is desirable to provide a means for protecting the diamond cutters during drilling to inhibit damage to the diamond cutters ~o that max~mum penetration rates cnn be ach~eved.
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. 5 , , ', ~.,.
. ., ., , ~ i13~S
In accordance with the present invention there i5 ~` , provided a rotary rock bit comprising: a blt: body having a longitudinal axis of rotation; a plurality of diamond cutter~
each having a cutting edge protruding from the bit body for en~aging the bottom of a hole being drilled at a selected rake angle for shearing rock in a plurality of paths concentric with the axis of the bit body; and means for limiting depth of penetration of the diamond cutters into the rock to les~
than the distance of protrusion of the diamond cutters from the bit body comprising a plurality of rolling cone cutters mounted on the bit body for rotation upon rotation of the bit body, each rolling cone cutter comprising a plurality of carbide inserts protruding rom the surface of the rolling cone cutter a distance less than the distance of protrusion of the diamond cutters from the hit body in the axial direction for engaging the bottom of the hole being drilled and for crushing or gouging of rock in a path çoncentric with the ~:
portion of the hole drilled by the diamond cutters.
~ . . .
' . ' :,.
~ 3 2 5 ~8~
. .
These and other features and advantages of the present invention will be appreciated as the same becomes better understood by reference to the follo~wing de~iled :~;
5 i description of presently preferred embodimemts wherein:
FIG. 1 is a Longitudinal cross sectilDn of a drill b~t constructed according to principles o this i~ven~ion;
FIG. 2 is an end view of the drill bit of Fig. l; ~;
FIG. 3 is a semi-schematic illus~ration o the dr~
10 ~ bit indicat~ng the relationship between the diamond cutters . ;
and rolling cone cutters thereon;
FXG. 4 is a perspective view o a dlamond cutter;
FIG, 5 i~ a semi-~chematic end ~iew o another `.
. embodiment of drill bit constructed according to principles 15 ~ of thi~ invention; ::
FIG. 6 is a semi-schematic end view of another .. ~:
embodiment of drill-bit constructed according to principles o this invention, and FIG. 7 is a semi-schematic end view of another . ~ :
20. l') embodiment o drill bl~. ~
. : "^`,: " .. :
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1 Description FIG. 1 is a longi~udinaL cross section and FI~. 2 is an end view of a core bi~ making application of both diamond cutters and rolling cone cut~ers. In Fig. 2 the S bit is ready for about the last stage of assembly, namely, insertion of the diamond cut~ers. They are omi~ted from this view to show the alignment of the holes ~n which the cutters are mounted.
As best seen in FIG. 1, it is ~onvenien~ to make 10 the bit body in several pieces and weld it together during '~
assembly. Four steel legs 10 having a general L-shape are machined and heat treated. Each o these legs includes a conven~ional bearing pin which cannot be seen in FIG. 1 since rolling cone cutters 11 are mounted on the respective ~`
pins in the conventional manner. The rolling eone cutter legs 10 are welded on a Lower bit body 12 after it has been machined. A pin blank 13 is then welded on to the body 12 ..
and a conventional oil well thread 14 i8 machined on the blank. The body and pin blank have a hollow axiaL passage L6 which, during use, receives a conventional core catcher ff for retrievlng cores cut by the core drill. At the lower end of t~e passage and above the level where cuttlng occurs there are four surfaces 17 collectively defining a cylinder h~ving only a sl~ghtly larger diameter than the diame~er of the core being made by the bit. These surfaces 17 are on the interior of four arms 18 spaced between the four rolling cone cutter~ 11. These arms support diamond cutters lS (Fig. 1).
.. . ..
, . " , ' ,-, ,, 1 The diamond cutters are mounted in each of slx fldt bottomed holes 19 ~Fig. 2~ drilled in the ends of the arms 18. The holes are labeled A, B and C to indicate the r~w of cutting for each di~mond cut~er as furthler described ;.
S hereafter Each hole l9 is formed at an angle to the axis of the bit for supporting the respective diamond :
cutter in its proper position. This is indicated in FIG. 2 by showing the outer end of the hole in solid lines and also showing the bottom of the hole with the hidden 10 portions in dotted lines. The specific angular relation- .
ships are not readily determined from this drawing since : ``. -the ends of the arms 18 ln which the holes are.drilled .;
are not planar, as seen in FIG. 1. The angular relation .:.
between the holes for the diamond cutters and the axis of the bit is better ~een in FIG. 3 which i8 a semi-schematic cross section.indicating the paths of ~he cutters. ~.
FIG 4 is a per~pective view of one of the COMPAX diamond cutters available from General Electric. The diamond ~s pre~ent as a plate 21 about 0.020 inch thick and about 0.33 inch diameter. This is not a single crystal diamond but . i8 a diamond-to-diamond, bonded, polycrystalline material.
The diamond plate 21 is bonded to a tungsten carbide cylinder 22 that is in turn brazed to a tungsten carbide . slug 23.- The carbide slug has a cylindrical base about 0.503 inch diameter to give a tight press fit in a one-half inch diEmeter hole in the bi~. Soch a press fit is the sole mounting required or such a diamond cu~er. :
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lOb.:3--5 1The short carbide cylinder 22 i~ supported on the slug 23 by a buttress like portion 25 ~uppor~ing the end of the carbide cylinder, except a narrow rim about 0,01 inch wide around half the perimeter o the carbide cylinder. ~ ' S This prevents portions of the carbide slug from interfering with cutting action by the diamond pla~e 21. The carbide cylinder 22 and hence the diamond plate 21 are tilted rearwardly (downwardly in Fig. 4) relative to the axis o~ the sLug at an angle in the range of from about 5 to 15 so that 10 in use the rake ang~e or angle of attack of the diamond ,~ -plate on the rock is abou~ -5 to -15. Rake angles from about 0 to about -20 appear to be suitable. COMPAX diamond cutters with carbide 81ug9 are available in a few lengths between abou~ 0.9 and 1.155 inch to accommodate various lS desired extensions of the diamond plate from the body of the bit in which the ~lug is inserted or to accommodate `
various hole depths.
The rolling cone cutters 11 are of a generally conventional type. In this embodiment each cutter has 20 either two or three inner rows of tungsten carbide inserts 26. Each roll~ng cone cutter also has an outermost row of carbide inserts 28 generally referred to as the gage row.
The inserts in the outer~ost row are at the periphery of the hole being drilled and maintain its full gage. The 25 spacing of the inserts within the rows 26 and 28 on individual rolling cone cutters may be varied in the conventional manner to minimize tracking and maximize cutting efficiency. The inner rows of inserts 26 on the various rolling cone cutters are at different radi~l ;
30 distances from the axis of the bit. Thus, five "groovesl' are cut by the inner rows and one by the gage row so that in effect six diff~rent annular "groove6" are cut in the , 9 , ' ~ j ~
.
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10613Z~
.
1 bottom of the hole as ~he drill i~ operated. A variety of such patterns can be provided as are well known to those skilled in the art for assuring full ~ace cutting on the end of the hole being drilled.
FIG~ 3 is a schematic illustration for indicating the location of the various grooves cut by the inæerts in the : ~ -rolling cone cutters illustrated in FIGS. l and 2 and by the diamond cutters. In ~he left side of this view the cutting elements are projected around the axis of the bit ,;
~0 as if all lay in a common radial plane. This suggests considerable overlap of the mounting portions o~ the cutting elements that is not present in the actual structure of the ; ;
bit, The purpose is to indicate the relative locations of the cutting portions.
In this view the gage row of inserts 28 is seen to be adjacent the wall 29 of the hole being drilled. The balance of the carbide inser~s 26 ~n the inner rows of ~he rolling cone cutters can be seen to cut a major portion of the annulus between the wall 29 of the hole and a cylindrical core of rock 20 32 entering the axial passage through the bit. The three rows of diamond cutters in this embodiment are labeled 15A, 15B
and L5C ~n FIG. 3, corresponding to the holes 19A, l9B and l9C ~n FIG. 2. It will be noted that whereas there are a large numb.er of carbide inserts in each of the ~ows 26 and 25 28 cut by the rolling cone cutters, there are only two diamond cutters 15 in each of the rows A, B and C.
The innermost p~ir 15A of diamond cutters cuts a path ;~
through ~he rock adjacent the core 32 and thus trims the core to gage. The other two pairs l5B and l5C of diamond cutters 30 cut the balance of the annulus between the innermost iamond cut~er l5A and the innermost row 31 . .
' 10 , 0 6 ~ 3 2 5 1 of carbide inserts. ALthough the various inserts and diamond cutters essentially cut ln a plurality of concentric grooves on the bottom of the hole, they ~re arranged to cut in a profile that ls an essentially S continuous or smooth curve extending across ~he annulus from the core to the gage of the hole. Other arrangement~
can be provided with ~he diamond ou~ter~ leading or trailing the cutting by the carbide inserts but the illustrated arrangement is pre~erred for minimizing cracking of the core. Further, by avoiding a '~step" i~, ~he bottom of the hole, formation of excessively large chips is avoided. Large chips from the edge o~ such a step may cau~e lmpact loads on the diamond cu~ers, leading ~o failure. This principle is applicable whether a core i~ being formed or ths full face of the hole i8 being drilled.
It will be noted ~hat the curvature provided in the bottom of the hole in the arrangement illustrated in FIG. 3 is a sub~tantially smooth curve blending rather 20 gradually into the core 32 in the center and somewhat Les8 .
graduall~ into the wall 29 of the hole. Thi8 curvature without a sharp trans~tion between the annulus being cut and the core minimizes locations of stress concentrat-lon and fur~her helps avoid breakage of the core.
It is an important function of the rolling cone cutt.ers to limit the depth of penetration by the diamond .
cutters. Depth of penetration o the diamond cutters should be limited to no more than about three fourths o~ the length of the diamond plate. In this context, the ~.Le~gth . 11 ', l ¦of the plate is considered to be its extent in the directiQn ¦parallel to the hole ax~s. Since the available COMPAX diamond ¦plates are circular and about 0.33 inch diameter, it Ls pre-¦ ferred that the depth o~ penetration be no more than about S ¦ 0.25 inch. If penetration exceeds about three-fourths the ¦ length of the diamond plate s~gnificant wear of the carbide ¦ BlUg may occur~ weakening ~t to the point that it may fa~10 ¦ Further, with exces~ive penetration, drilling in interspersed ¦ formations can lead to high impact loads on the diamond ~ ¦cutters and failure. Preferably ~he depth of penetration ¦ of the diamond plate is appreciably less ~han three-four~h~
oP its length 80 that life time is determined by wear of the diamond r~ther than by the pos~ibility of fracture.
Preferably the depth of penetration i8 no more than about 0.1 inch to minimize impact l~ading on the diamond cutter in the case of interspersed formations.
The depth of penetration of the diamond cutters i~
limited by the protrusion of the carbide inserts ~rom the body of the rolling cone cutters. The carbide inserts ean penetrate into the rock during drilling no more than their protru~ion from the surfaee of the rolling cone cut~er.
The actual depth of penetration i8 ordinarily less than ~
the full protrusion of the carbide inserts since there i8 ' . .
interference by fragmented rock. Thus, by limiting the protrusion of the carbidè ~næerts from the rolling cone cutters to a fraction o~ the len~th of the diamond plate, the depth of penetr~tion o~ the d~amond plate i8 also . , , , ' 1,'' ' ,.
,~ ;
. ' ' ', . ' 1~ ~
.. ...
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1 limited.
In the arrangemen~ hereinabove described and illus~rated, the length of the diamond plate is about 0.33 inch. Protrusion of the carbide inserts from the S rolling cone cutters is about 0.25 inch. Because of interference during drilling opera~ions, the maximum ,depth of pene~ration of the dîamond plates into rock . . .. ~ , . . . .. _ _ . _ -- _ .... ._ . ..
being cut is less than the full leng~h of the carbide inserts~
. ........ . . . . .. . . . .. . ... . . .
Most typically, the penetration by the diamond plate is no more than about one-~hird of their length~
It i8 also pre~erred that the protrusions of the carbide inserts on the rolling cone cutters be more than about one-fourtho the length of the diamond plate. If the protrusion is less than this amount, cut~ing b~ the diamond cutters may be unduly limited so that they do not work to full capacity and maximum penetration rate cannot be obtained.
Practic2 of this inven~ion with limitation o penetration of diamond cutters is not restricted to the core drill hereinabove described and illustrated.
FIG, 5, for example, lllu~trates in end view an . embodiment of rock bit for drilling a hole without a core uslng both rolling cone cutters and diamond cutters. In this embodiment, the center portion o~
the hole is drilled by rolling cone cutters 41 and ~he surrounding annulus is drilled by diamond cutters.
Thus, three conventional rolling cone cu~ters 41 are mounted in the center portion o a drill bit. The nose ends of these cutters are arranged to provide 3~
, . .
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3 ::
~1 10613Z5 1 drilling to the center of the hole ~n ~he conven~ional ~ -manner. In essence the arrangement of the three rolling ~;
cone cutters i8 the same as in a conventional three-cone rock bit. Each of the rolling cone cutter~ has a plurality of carbide in~erts 42 protruding from its surface in a series of rows. ~referably these rows and the insert~
within them are ~taggered in a con~entional manner to assure cutting over the full face of the bit and ~bsence of tracking. : : -The bit body 40 extends radially outwardly from . :
the path cut by the rolling cone cutters. On this por~ion o~ the bit body there are a plurality of diamond cutter~ ; :
43 mounted to sweep out a number of circular paths for cutting rock in the annulus beyond the outside row o lS inserts on the cutter cones. The diamond cutters in :~
this embodiment are like those hereinabove described and illustrated in FIG. 4 but are illustrated schematically simply ~s semi-circles to indicate the direction o~ cu~ting.
In each case the diamond plate faces in a circumferential ;~
direction around the bit. Fluid ~ets 44 are provided in . the .bit body ~or directing drilling mud into the regions around the various cutters for removing rock chips from the hole. "Junk slots" 45 or c~earancë maylbe providëd around th~
body of the bit in a conventional mannër to accommodate 25 such flow. :
In rock drilling with rolling cone cutters, main~
~aining the gage o~ the hole is often one of the problems encountered. For this reason, typical carbide insert type rock ~its have a ~ull row of inserts in the gage row ~0 . ' : .
- 106:1L3Z5 1 on each rolling cone cutter and the inserts are typically closely spaced to best a~sure a ~ull gage hole throughout the life of the bit . The gage row is subject to considerable wear because of drag of the carbide inserts on the wall o~
the hole. Carbide inser~s are effeckive in the ch~pping-crushing action in the bottom of the hole and less effective in drag on the sides. Wear on the gage row inserts ean cause tight hole~ giving later difficulties in installing casing or running new tools in the hole.
~0 Many of these problems are avoided in an embodiment as illustrated in FIG. 5 since the outermost row o~ inserts on the rolling cone cutters 41 are not relied upon to define the gage of the hole. The hole gage is assured by the outermost row of diamond cutters 43 which are appropriately designed for drag cutting as hereinabove described. Since these diamond cutters are provided on a relatively large diameter portion of the bit, a substan~ial number may be used so that wear on each is minimized and accidenta7 damage to some of the inserts will not deleteriously aect operation of the bit. If desired a single row of diamond inserts may be prov~ded on the gage of an otherwise conventional three cone bit. Thus the hole can essentially be reamed to fulL gage by the diamond cutters while the main downhole cutting is by rolling cone cutters.
In the illustrated arrangement, the bit body 4~ ~as three legs extending down-hole so that the diamond cutters b~3 form a cut that has a proile that i~ essentially a continuation of the profile made by the rolLing cone cutters 41. Thus the bottom o~ the hole is in the form 3~ :
' 15 ' .. ..
. .~
13ZS ~
l of a series of concentric grooves without an extens~ve ~tep therebetween. This minimizes the formation of oversized chips that do not clear the face of the tool promptly and result in regrinding with con~;equent loss S of efficiency or possible damage to the diamond cutters.
If desired, the diamond cutters can lead or trail the rolling cone cutters so as to cut at a different eleva~ion in the hole.
The inserts 42 on the rolling cone cutters protrude from the facP of the respective cutter a distance less than the length of the diamond plate on the diamond cutters.
This limits the extent of penetration o~ the diamond cutters as hereinabove described. The proportions between the pro~rusion of the carbide inserts and the length of the diamond plates is preferably the same as hereinabove described. By providing such means for limiting penetration of the diamond cu~ters prolonged!
life is obtained.
FIG. 6 illustrates another embodiment of hole drilling bit constructed according to principles of thi6 invention. As illustrated in this embodiment, the bit body 51 has a plurality of diamond cutters 52 mountèd on the face thereof in an array that provides cutting over substantially ~he full face of the drill bit. A relatively small hole 53 is let in the middle ~ince drag cutting is relatively inefficient near the centerline of the bit~ A small core of rock passe~
through the hole 53 to a conventional core breaker 1~613ZS
1 (not shown) in the bit body.
The face of the drill b~t illustra~ed in FIG. 6 is not planar but preferably more resembles the surface of a donut or torus. That is, the face is relati~ely S recessed near its periphery and near the hole 53 through the center. The intermediate portion is relatlvely raised or nearer as seen in FIG. 6. Since each of the diamond cutters extends from the bit body the same diætance, the hole that is cut as the bit is used is approx~mately the complement of the lower face. Such a configuration appears desirable for best mud circulation from ~e~s 54 during drilling operat~ons.
As mentioned above, penetration of the diamond cutters into the rock being cut should be l~mited to prolong their life. There are, therefore, provided a pair of generally conical rollers 56 mounted for ~.
rotation on the bit body with minimum slippage on the bottom of a hole to minimiæe wear on the rollers. The rollers 56 are hardened steel or may be faced wi~h a hard facing materlal if desired. They do not have carb~de inserts on their faces but are essentiaLly smooth and con~igured to approximateLy con~orm to the shape of the bottom o the hole being drilled.
~he surfaces of the rollers are recessed slightly
2 below the sur~ace cut by the diamond cutters 52 so that during normal operations when the diamond cutters are penetrating the rock ormation by an acceptable amount, . , ':' ''' '', .
. , ~.'`,'.' .
. , ~.'`,'.' .
3 ; :~
. 17 ' , ;:'',. :
~ 1 0 61 32 5 l the rollers do not come in~o direc~ contact with the uncu~
rock. I~, however, there is an accidental overload on the drill bit for ~he particular rock formation being drilled at that ~ime such tha~ the diamond cutters would over-penetrate, the rollers come in contact with the bottom ofthe hole and limit the penetration. Excess loads applied to ~he rock bits are carried by the rollers rather than the diamond cutters. Thi8 protects the diamond cutters from accidental damage and significantly prolongs the life of the drilling blt, particularly when drilling in interspersed formations that are particularly troublesome drilling for thi~ type of bit. Preferably the roller~ 56 are recessed about three fourths of the length o the diamond plates on the diamond cutters. Thi3 assures that the diamond plates do not penetrate more than this amount and in practice they penetrate less due to intererence between rock fragments and the roller~. !
In an embodiment as illustrated in FIG. 6 a hard-faced "skid" area may sometimes be ~ubstituted for the rollers 560 Such may be used where overloading i~ expected to be intermittent and infrequent. Such "skids" have high friction which may cause considerable power waste and generate high temperatures at the cutting surfaces. Rollers for limiting penetration of the dra~ cutter6 are therefore pre-ferred.
FIG, 7 is a semi-~chemat~c end view of another embodiment of rock drill bit c~nstructed according to princ;ples of this invent~on. This embodiment differs from those of FIGS. ~ to S in that diamond cutters and carbide inserts on rolling cone cutters drill portions of the bottom of a hole ~hat o~erlap, ;
. ' ..
.
1 0 6~ 32 5 1 that ls, at least part of both the diamond cutters and carbide inserts follow the same annular paths on the bottom of a hole being drilled.
In this embodiment, the bit body has a pair of depending S arm~ 61 for mounting diamond cutters. Between the arms there are mounted a pair of tungs~en carbide insert rolling cone cutters 62. An axial hole 63 ~n the bit body leads to a conventional core breaker (not shown) 60 that the complete cross section of the hole is drilled. Each of the rolling cone cutters has a row of tungsten carbide inserts 64 ~n a gage row that assures that a full gage hole i8 drilled.
One of the rolling cone cutters has two additiGnal rows of tungsten carbide inserts 66 ~paced inwardly from the gage row. The other of the rolling cone cut~ers has three 15 ~ddi~ional rows of tungsten carbide in~er~s 67 spaced inwardly from the gage row. Each of these row~ of carbide insert~ drills in an annular path on the bottom o~ the!hole ~-as the drilL bit i8 rotated. The two rows of carbid~
inserts 66 on the flrst rolling cone are positioned so 20 t~at the annular paths that they drill are intersper~ed between the annular paths drilled by the ~hree rows o~
carbide in8ert8 67 on the other rolling cone. Thus~ fiv~
annular paths are drilled inwardly from the outermost gage row. Such an arrangement permits the carbide inserts -to be somewhat spaced apart for greatest ~trength of the cone and still provide for drilling over the full bottom ;~ -of the hole. .
The bottom of each of the arm~ 6L has 8 profile approximately the ~ame a~ ~he profile of the cutter ~one~
3 62. Each arm has three diamond cutter~ 68 mounted for . ', 19 ,'"' ; - . , , .. ~ ,. .
' ~1 0 6 ~ Z 5 ~ ~
1 cutting at the gage of the hole being drilled. These , ,-diamond cutters are illus~rated schematically in FIG. 7 in the same manner as FIGS. 5 and 6 but it wilL be ~, appreciated that they are of the type herein,abo~e S described and illustrated in FIG. 4. The ga,ge diamond cutters 68 drill in the same annular path as the gage carbide inserts 64 on the two rolling cone cutters.
Each arm also has a plurality of additional diamond cutters 69 spaced inwardly from the gag,e row 68. These additional diamond cutters are pos~tioned in annular paths corresponding to the addi~ional annular paths drilled by the carbide inserts 66 and 67 in the rolling cone cutters.
Thu8, the annular paths on the bottom of a hole are drilled by both carbide inserts and diamond cutters.
Aæ mentioned above, carbide inserts on rolling cone cutters conventionally drill by either of two actions. ;, When the axis of the cone ~ntersects the axis of the rock drill the principal drilling action i8 due to crushing of the rock by the carbide Inserts due to the heavy weight applied to the drill bit. When the axis of a cutter cone is offset slightly from the axis of the drilL bit there is ~ome sliding or skidding action by the cone and an appreciable amount of gouging action during drilling. The gouging action "
o an off~et bit is desirable in relatively softer rock. The 25 'primary crushing action of a non-ofset drill bit is ord~nariLy preferred in relatively harder rock. -' Either an offset or non-offset roller for primarily gouging or crushing action, respectively, can be used in the arrangement of FIG. 7. In either case the path that is 3 drilled by each row of carbide inserts is rough .ince the . . ' , ....
, ' 10613Z5 1 ¦loads are applied intermi~tently on ~he rock.
¦ The diamond cutters cut by a shearing action as they ¦are dragged acro~ the rock. Thus a groove cut by a diamond ¦cutter is ordinarily rather ~mooth except as chip~ from the 5 ¦rock may leave a sl~ghtly roughened surface.
The diamond cutters in the embodimen~ of FIG. 7 are arranged in the same annular paths as the carbide insert~V
on the roLling cone cutters. Thus, the rough groove formed by the carbide inserts i8 scraped smooth by ~he diamond 10 cutters. This reduces the load on the diamond cutters ~ -~or a given volume of rock removed from the bottom of the hole. Further, it minimizes or eliminate~ the possibi~ity of ~Itrack~ng~ by the rolling cone cutters where the carbide inserts r~peatedly contact the same point on the bottom of ~;
15 the hoLe and drill ine~iciently. Thus9 a combinatlon o~ :
diamond cutters and rolling cone cutters on a rock drill where both drill in the same profile on the bottom oP a hole can be more effective in some formations than either diamond cutters or rolling cone cutters alone.
In the embodiment of FIG. 7 substantially the entire bottom of the hole is dri}led by both carbide inserts and diamond cutters. I~ desired, either can be arranged so that diferent portions are drilled, with only a portion oi the bottom of the hole being drilled by both carbide 25 inserts and diamond cutters.
The carb~de inserts on the rolling cone cutters in the embodiment of FIG. 7 protrude from the surface thereof a `:
distance less than ~he full length of the diamond cutters.
Thus, as described abo~e the depth of penetration of the 30 diamond cutters i8 limited to minimize wear on ~he carbide . . .,, . , .. ,~.
' 1 0613Z5 1 ¦ slug mounting the diamond plate and minimizing the impact ¦ loading on the diamond. Criteria as set forth above are ¦ employed whether the carbide inserts and di~mond cutter~ ~
¦ drill in similar or different portions of the bottom of ~-S ¦ a hole.
Al~hough limited emb~diments of drill bits havlng diamond cutters with means for limiting penetratlon of the diamond cutters have been described and illustrated herein, many modifica~ions and ~arlati~ns will be apparQnt $o one skilled in the art. Thus, or example, although the drag cutters are described herein in terms of the carbide slugs bearing a diamond plate currently ava~lable commercially? other variations o~ drag cutter are also suitable. The drag cutter may have other ~ 15 configurations instead of the essentially cylindrical end prvvided by the diamond plates.
In some embod~ments tungsten carbide or other h~rd drag cutters may be used with depth of penetration limited by rollers better capable of carrying heavy axial load.
Use o means ~or limiting penetration i9 particularly applicable when the drag cutters are hard and ~herefore wear res~stant, yet ~ubject to impact or failure upon over-penetration. This inven~ion has essentially no applicability in steel drag bits for soft for~tions.
If desir2d, one may use diæmond cutters near the center of the hole being drilled (with or without a core) and on the hole ga~e with carbide insert r~lling cone cutter~ -drillin~ an annulus ~herebetween. Many other modifications and variations will be apparent to one skilled in the art, and it is therefore to be understood that the in~ention may be practiced otherwise than as specifically described.
.. .,., ., j : .
. 17 ' , ;:'',. :
~ 1 0 61 32 5 l the rollers do not come in~o direc~ contact with the uncu~
rock. I~, however, there is an accidental overload on the drill bit for ~he particular rock formation being drilled at that ~ime such tha~ the diamond cutters would over-penetrate, the rollers come in contact with the bottom ofthe hole and limit the penetration. Excess loads applied to ~he rock bits are carried by the rollers rather than the diamond cutters. Thi8 protects the diamond cutters from accidental damage and significantly prolongs the life of the drilling blt, particularly when drilling in interspersed formations that are particularly troublesome drilling for thi~ type of bit. Preferably the roller~ 56 are recessed about three fourths of the length o the diamond plates on the diamond cutters. Thi3 assures that the diamond plates do not penetrate more than this amount and in practice they penetrate less due to intererence between rock fragments and the roller~. !
In an embodiment as illustrated in FIG. 6 a hard-faced "skid" area may sometimes be ~ubstituted for the rollers 560 Such may be used where overloading i~ expected to be intermittent and infrequent. Such "skids" have high friction which may cause considerable power waste and generate high temperatures at the cutting surfaces. Rollers for limiting penetration of the dra~ cutter6 are therefore pre-ferred.
FIG, 7 is a semi-~chemat~c end view of another embodiment of rock drill bit c~nstructed according to princ;ples of this invent~on. This embodiment differs from those of FIGS. ~ to S in that diamond cutters and carbide inserts on rolling cone cutters drill portions of the bottom of a hole ~hat o~erlap, ;
. ' ..
.
1 0 6~ 32 5 1 that ls, at least part of both the diamond cutters and carbide inserts follow the same annular paths on the bottom of a hole being drilled.
In this embodiment, the bit body has a pair of depending S arm~ 61 for mounting diamond cutters. Between the arms there are mounted a pair of tungs~en carbide insert rolling cone cutters 62. An axial hole 63 ~n the bit body leads to a conventional core breaker (not shown) 60 that the complete cross section of the hole is drilled. Each of the rolling cone cutters has a row of tungsten carbide inserts 64 ~n a gage row that assures that a full gage hole i8 drilled.
One of the rolling cone cutters has two additiGnal rows of tungsten carbide inserts 66 ~paced inwardly from the gage row. The other of the rolling cone cut~ers has three 15 ~ddi~ional rows of tungsten carbide in~er~s 67 spaced inwardly from the gage row. Each of these row~ of carbide insert~ drills in an annular path on the bottom o~ the!hole ~-as the drilL bit i8 rotated. The two rows of carbid~
inserts 66 on the flrst rolling cone are positioned so 20 t~at the annular paths that they drill are intersper~ed between the annular paths drilled by the ~hree rows o~
carbide in8ert8 67 on the other rolling cone. Thus~ fiv~
annular paths are drilled inwardly from the outermost gage row. Such an arrangement permits the carbide inserts -to be somewhat spaced apart for greatest ~trength of the cone and still provide for drilling over the full bottom ;~ -of the hole. .
The bottom of each of the arm~ 6L has 8 profile approximately the ~ame a~ ~he profile of the cutter ~one~
3 62. Each arm has three diamond cutter~ 68 mounted for . ', 19 ,'"' ; - . , , .. ~ ,. .
' ~1 0 6 ~ Z 5 ~ ~
1 cutting at the gage of the hole being drilled. These , ,-diamond cutters are illus~rated schematically in FIG. 7 in the same manner as FIGS. 5 and 6 but it wilL be ~, appreciated that they are of the type herein,abo~e S described and illustrated in FIG. 4. The ga,ge diamond cutters 68 drill in the same annular path as the gage carbide inserts 64 on the two rolling cone cutters.
Each arm also has a plurality of additional diamond cutters 69 spaced inwardly from the gag,e row 68. These additional diamond cutters are pos~tioned in annular paths corresponding to the addi~ional annular paths drilled by the carbide inserts 66 and 67 in the rolling cone cutters.
Thu8, the annular paths on the bottom of a hole are drilled by both carbide inserts and diamond cutters.
Aæ mentioned above, carbide inserts on rolling cone cutters conventionally drill by either of two actions. ;, When the axis of the cone ~ntersects the axis of the rock drill the principal drilling action i8 due to crushing of the rock by the carbide Inserts due to the heavy weight applied to the drill bit. When the axis of a cutter cone is offset slightly from the axis of the drilL bit there is ~ome sliding or skidding action by the cone and an appreciable amount of gouging action during drilling. The gouging action "
o an off~et bit is desirable in relatively softer rock. The 25 'primary crushing action of a non-ofset drill bit is ord~nariLy preferred in relatively harder rock. -' Either an offset or non-offset roller for primarily gouging or crushing action, respectively, can be used in the arrangement of FIG. 7. In either case the path that is 3 drilled by each row of carbide inserts is rough .ince the . . ' , ....
, ' 10613Z5 1 ¦loads are applied intermi~tently on ~he rock.
¦ The diamond cutters cut by a shearing action as they ¦are dragged acro~ the rock. Thus a groove cut by a diamond ¦cutter is ordinarily rather ~mooth except as chip~ from the 5 ¦rock may leave a sl~ghtly roughened surface.
The diamond cutters in the embodimen~ of FIG. 7 are arranged in the same annular paths as the carbide insert~V
on the roLling cone cutters. Thus, the rough groove formed by the carbide inserts i8 scraped smooth by ~he diamond 10 cutters. This reduces the load on the diamond cutters ~ -~or a given volume of rock removed from the bottom of the hole. Further, it minimizes or eliminate~ the possibi~ity of ~Itrack~ng~ by the rolling cone cutters where the carbide inserts r~peatedly contact the same point on the bottom of ~;
15 the hoLe and drill ine~iciently. Thus9 a combinatlon o~ :
diamond cutters and rolling cone cutters on a rock drill where both drill in the same profile on the bottom oP a hole can be more effective in some formations than either diamond cutters or rolling cone cutters alone.
In the embodiment of FIG. 7 substantially the entire bottom of the hole is dri}led by both carbide inserts and diamond cutters. I~ desired, either can be arranged so that diferent portions are drilled, with only a portion oi the bottom of the hole being drilled by both carbide 25 inserts and diamond cutters.
The carb~de inserts on the rolling cone cutters in the embodiment of FIG. 7 protrude from the surface thereof a `:
distance less than ~he full length of the diamond cutters.
Thus, as described abo~e the depth of penetration of the 30 diamond cutters i8 limited to minimize wear on ~he carbide . . .,, . , .. ,~.
' 1 0613Z5 1 ¦ slug mounting the diamond plate and minimizing the impact ¦ loading on the diamond. Criteria as set forth above are ¦ employed whether the carbide inserts and di~mond cutter~ ~
¦ drill in similar or different portions of the bottom of ~-S ¦ a hole.
Al~hough limited emb~diments of drill bits havlng diamond cutters with means for limiting penetratlon of the diamond cutters have been described and illustrated herein, many modifica~ions and ~arlati~ns will be apparQnt $o one skilled in the art. Thus, or example, although the drag cutters are described herein in terms of the carbide slugs bearing a diamond plate currently ava~lable commercially? other variations o~ drag cutter are also suitable. The drag cutter may have other ~ 15 configurations instead of the essentially cylindrical end prvvided by the diamond plates.
In some embod~ments tungsten carbide or other h~rd drag cutters may be used with depth of penetration limited by rollers better capable of carrying heavy axial load.
Use o means ~or limiting penetration i9 particularly applicable when the drag cutters are hard and ~herefore wear res~stant, yet ~ubject to impact or failure upon over-penetration. This inven~ion has essentially no applicability in steel drag bits for soft for~tions.
If desir2d, one may use diæmond cutters near the center of the hole being drilled (with or without a core) and on the hole ga~e with carbide insert r~lling cone cutter~ -drillin~ an annulus ~herebetween. Many other modifications and variations will be apparent to one skilled in the art, and it is therefore to be understood that the in~ention may be practiced otherwise than as specifically described.
.. .,., ., j : .
Claims (20)
1. A rotary rock bit comprising:
a bit body having a longitudinal axis of rotation;
a plurality of diamond cutters each having a cutting edge protruding from the bit body for engaging the bottom of a hole being drilled at a selected rake angle for shearing rock in a plurality of paths concentric with the axis of the bit body; and means for limiting depth of penetration of the diamond cutters into the rock to less than the distance of protrusion of the diamond cutters from the bit body comprising a plurality of rolling cone cutters mounted on the bit body for rotation upon rotation of the bit body, each rolling cone cutter comprising a plurality of carbide inserts protruding from the surface of the rolling cone cutter a distance less than the distance of protrusion of the diamond cutters from the bit body in the axial direction for engaging the bottom of the hole being drilled and for crushing or gouging of rock in a path concentric with the portion of the hole drilled by the diamond cutters.
a bit body having a longitudinal axis of rotation;
a plurality of diamond cutters each having a cutting edge protruding from the bit body for engaging the bottom of a hole being drilled at a selected rake angle for shearing rock in a plurality of paths concentric with the axis of the bit body; and means for limiting depth of penetration of the diamond cutters into the rock to less than the distance of protrusion of the diamond cutters from the bit body comprising a plurality of rolling cone cutters mounted on the bit body for rotation upon rotation of the bit body, each rolling cone cutter comprising a plurality of carbide inserts protruding from the surface of the rolling cone cutter a distance less than the distance of protrusion of the diamond cutters from the bit body in the axial direction for engaging the bottom of the hole being drilled and for crushing or gouging of rock in a path concentric with the portion of the hole drilled by the diamond cutters.
2. A rock bit as defined in claim 1 wherein the rolling cone cutters are mounted relatively nearer the axis of the bit body and the diamond cutters are mounted relatively nearer the periphery of the bit body for drilling an annulus around the portion of a hole drilled by the rolling cone cutters.
3. A rock bit as defined in claim 1 wherein the diamond cutters are mounted relatively nearer the axis of the bit body and the rolling cone cutters are mounted relatively nearer the periphery of the bit body for drilling an annulus around the portion of a hole drilled by the diamond cutters.
4. A rock bit as defined in claim 1 wherein the bit body further comprises an axial core receiving passage, and wherein the diamond cutters are mounted on an end portion of the rock bit body around the axial passage for drilling an annular portion of a hole between a rock core and the portion of the hole drilled by the rolling cone cutters.
5. A rock bit as defined in claim 1 wherein the diamond cutters are mounted on the bit body in a position such that there is a substantially smooth curve between the profile cut by the diamond cutters and the profile cut by the rolling cone cutters so that the bottom of a drilled hole comprises essentially a continuous surface of concentric grooves without a step shoulder therebetween.
6. A rock bit as defined in claim 1 wherein each diamond cutter comprises:
a slug inserted in the bit body; and a diamond plate bonded to the slug, the diamond plate facing in a circumferential direction relative to the axis of the bit body for shearing rock upon rotation thereof.
a slug inserted in the bit body; and a diamond plate bonded to the slug, the diamond plate facing in a circumferential direction relative to the axis of the bit body for shearing rock upon rotation thereof.
7. A rock bit as defined in claim 1 or 6 wherein the selected rake angle of the diamond cutters is in the range of from about 0° to about -20°.
8. A rock bit as defined in claim 6 wherein the carbide inserts on the rolling cone cutters protrude from the surface thereof more than about one-fourth the length of the diamond plates on the diamond cutters and less than the full length thereof.
9. A rock bit as defined in claim 6 wherein the carbide inserts protrude from the surface of the rolling cone cutters no more than about three-fourths of the length of the diamond plates.
10. A rock bit as defined in claim 1 wherein the bit body comprises:
a plurality of cone cutter legs extending downwardly therefrom and wherein a rolling cone cutter is mounted on each of the cone cutter legs;
an axial passage for receiving a core; and a plurality of diamond cutter arms extending down-wardly therefrom and interspersed between the cone cutter legs, and wherein each of the diamond cutter arms has at least one of said diamond cutters mounted thereon for drilling an annulus between the axial passage and a portion of rock drilling by the rolling cone cutters.
a plurality of cone cutter legs extending downwardly therefrom and wherein a rolling cone cutter is mounted on each of the cone cutter legs;
an axial passage for receiving a core; and a plurality of diamond cutter arms extending down-wardly therefrom and interspersed between the cone cutter legs, and wherein each of the diamond cutter arms has at least one of said diamond cutters mounted thereon for drilling an annulus between the axial passage and a portion of rock drilling by the rolling cone cutters.
11. A rock bit as defined in claim 1 wherein the rolling cone cutters have a profile similar to a profile cut by a plurality of the diamond cutters, said rolling cone cutters rotating with the bit body in essentially the same annular track as the said plurality of diamond cutters, the surface of the rolling cone cutters trailing the diamond cutters in a direction along the axis of a hole being drilled for engaging the bottom of the hole only upon maximum penetration of the diamond cutters.
12. A rock bit as defined in claim 1 wherein the rolling cone cutters are mounted for drilling a portion of the bottom of a hole and the diamond cutters are mounted for drilling another portion of the bottom of the hole.
13. A rock bit as defined in claim 1 wherein the rolling cone cutters are mounted for drilling the same portion of the bottom of a hole as at least a portion of the diamond cutters.
14. A rock bit as defined in claim 1 wherein the rolling cone cutters are mounted for drilling at least a portion of the bottom of a hole and wherein the diamond cutters are mounted for drilling at least a portion of the bottom of the hole, and the portion drilled by each at least partly overlaps the portion drilled by the other.
15. A rock bit as defined in claim 6 wherein the rolling cone cutters each include a plurality of carbide inserts protruding from the surface of the respective rolling cone cutter less than the full length of the diamond cutters, and the rolling cone cutters are mounted for drilling an annulus between the portion of the bottom of a hole drilled by the diamond cutters and the periphery of the hole.
16. A rock bit as defined in claim 15 wherein the bit body further comprises an axial passage for receiving a rock core, and wherein the diamond cutters drill an annulus between the rock core and the portion of a hole drilled by the rolling cone cutters.
17. A rock bit as defined in claim 6 wherein the rolling cone cutters each include a plurality of carbide inserts protruding from the surface thereof a distance less than the length of the diamond cutters; and wherein the rolling cone cutters are mounted on the bit body for drilling a central portion of a hole, and the diamond cutters are mounted on the bit body for drilling an annulus around the portion of the hole drilled by the rolling cone cutters.
18. A rock bit as defined in claim 6 wherein each rolling cone cutter includes a plurality of carbide inserts protruding from the surface thereof an effective distance less than about three fourths of the length of the diamond cutters for limiting penetration thereof, and greater than about one-third the length of the diamond cutters.
19. A rock bit as defined in claim 1, wherein the carbide inserts on the rolling cone cutters protrude from the surface thereof more than about one-fourth the length of the diamond portion of the diamond cutters and less than the full length thereof.
20. A rock bit as defined in claim 1, wherein the carbide inserts protrude from the surface of the rolling cone cutters no more than about three-fourths of the length of the diamond portion of the diamond cutters.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA263,992A CA1061325A (en) | 1976-10-22 | 1976-10-22 | Diamond cutter rock bit with penetration limiting |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA263,992A CA1061325A (en) | 1976-10-22 | 1976-10-22 | Diamond cutter rock bit with penetration limiting |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1061325A true CA1061325A (en) | 1979-08-28 |
Family
ID=4107104
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA263,992A Expired CA1061325A (en) | 1976-10-22 | 1976-10-22 | Diamond cutter rock bit with penetration limiting |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1061325A (en) |
-
1976
- 1976-10-22 CA CA263,992A patent/CA1061325A/en not_active Expired
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