Drill bit with a retained jack element

Abstract

A drill bit having a bit body intermediate a shank and a working face having at least one cutting insert. A bore is formed in the working face co-axial within an axis of rotation of the drill bit. A jack element is retained within the bore by a retaining element that intrudes a diameter of the bore.

Description

BACKGROUND OF THE INVENTION

This invention relates to drill bits, specifically drill bit assemblies for use in oil, gas and geothermal drilling. Drill bits are continuously exposed to harsh conditions during drilling operations in the earth's surface. Bit whirl in hard formations for example may result in damage to the drill bit and reduce penetration rates. Further loading too much weight on the drill bit when drilling through a hard formation may exceed the bit's capabilities and also result in damage. Too often unexpected hard formations are encountered suddenly and damage to the drill bit occurs before the weight on the drill bit may be adjusted. When a bit fails it reduces productivity resulting in diminished returns to a point where it may become uneconomical to continue drilling. The cost of the bit is not considered so much as the associated down time required to maintain or replace a worn or expired bit. To replace a bit requires removal of the drill string from the bore in order to service the bit which translates into significant economic losses until drilling can be resumed.

The prior art has addressed bit whirl and weight on bit issues. Such issues have been addressed in the U.S. Pat. No. 6,443,249 to Beuershausen, which is herein incorporated by reference for all that it contains. The '249 patent discloses a PDC-equipped rotary drag bit especially suitable for directional drilling. Cutter chamfer size and backrake angle, as well as cutter backrake, may be varied along the bit profile between the center of the bit and the gage to provide a less aggressive center and more aggressive outer region on the bit face, to enhance stability while maintaining side cutting capability, as well as providing a high rate of penetration under relatively high weight on bit.

U.S. Pat. No. 6,298,930 to Sinor which is herein incorporated by reference for all that it contains, discloses a rotary drag bit including exterior features to control the depth of cut by cutters mounted thereon, so as to control the volume of formation material cut per bit rotation as well as the torque experienced by the bit and an associated bottomhole assembly. The exterior features preferably precede, taken in the direction of bit rotation, cutters with which they are associated, and provide sufficient bearing area so as to support the bit against the bottom of the borehole under weight on bit without exceeding the compressive strength of the formation rock.

U.S. Pat. No. 6,363,780 to Rey-Fabret which is herein incorporated by reference for all that it contains, discloses a system and method for generating an alarm relative to effective longitudinal behavior of a drill bit fastened to the end of a tool string driven in rotation in a well by a driving device situated at the surface, using a physical model of the drilling process based on general mechanics equations. The following steps are carried out: the model is reduced so to retain only pertinent modes, at least two values Rf and Rwob are calculated, Rf being a function of the principal oscillation frequency of weight on hook WOH divided by the average instantaneous rotating speed at the surface, Rwob being a function of the standard deviation of the signal of the weight on bit WOB estimated by the reduced longitudinal model from measurement of the signal of the weight on hook WOH, divided by the average weight on bit defined from the weight of the string and the average weight on hook. Any danger from the longitudinal behavior of the drill bit is determined from the values of Rf and Rwob.

U.S. Pat. No. 5,806,611 to Van Den Steen which is herein incorporated by reference for all that it contains, discloses a device for controlling weight on bit of a drilling assembly for drilling a borehole in an earth formation. The device includes a fluid passage for the drilling fluid flowing through the drilling assembly, and control means for controlling the flow resistance of drilling fluid in the passage in a manner that the flow resistance increases when the fluid pressure in the passage decreases and that the flow resistance decreases when the fluid pressure in the passage increases.

U.S. Pat. No. 5,864,058 to Chen which is herein incorporated by reference for all that is contains, discloses a down hole sensor sub in the lower end of a drillstring, such sub having three orthogonally positioned accelerometers for measuring vibration of a drilling component. The lateral acceleration is measured along either the X or Y axis and then analyzed in the frequency domain as to peak frequency and magnitude at such peak frequency. Backward whirling of the drilling component is indicated when the magnitude at the peak frequency exceeds a predetermined value. A low whirling frequency accompanied by a high acceleration magnitude based on empirically established values is associated with destructive vibration of the drilling component. One or more drilling parameters (weight on bit, rotary speed, etc.) is then altered to reduce or eliminate such destructive vibration.

BRIEF SUMMARY OF THE INVENTION

A drill bit comprising a bit body intermediate a shank and a working face comprising at least one cutting insert. A bore is formed in the working face co-axial within an axis of rotation of the drill bit. A jack element is retained within the bore by a retaining element that intrudes a diameter of the bore.

The jack element may comprise a polygonal or cylindrical shaft. A distal end may comprise a domed, rounded, semi-rounded, conical, flat, or pointed geometry. The shaft diameter may be 50 to 100% a diameter of the bore. The jack element may comprise a material selected from the group consisting of gold, silver, a refractory metal, carbide, tungsten carbide, cemented metal carbide, niobium, titanium, platinum, molybdenum, diamond, cobalt, nickel, iron, cubic boron nitride, and combinations thereof.

In some embodiments, the jack element may comprise a coating of abrasive resistant material comprised of a material selected from the following including natural diamond, polycrystalline diamond, boron nitride, tungsten carbide or combinations thereof The coating of abrasion resistant material comprises a thickness of 0.5 to 4 mm.

The retaining element may be a cutting insert, a snap ring, a cap, a sleeve or combinations thereof The retaining element may comprise a material selected from the group consisting of gold, silver, a refractory metal, carbide, tungsten carbide, cemented metal carbide, niobium, titanium, platinum, molybdenum, diamond, cobalt, nickel, iron, cubic boron nitride, and combinations thereof.

In some embodiments, the retaining element may intrude a diameter of the shaft. The retaining element may be disposed at a working surface of the drill bit. The retaining element may also be disposed within the bore. The retaining element may be complimentary to the jack element and the retaining element may have a bearing surface.

In some embodiments, the drill bit may comprise at least one electric motor. The at least one electric motor may be in mechanical communication with the shaft and may be adapted to axially displace the shaft.

The at least one electric motor may be powered by a turbine, a battery, or a power transmission system from the surface or down hole. The at least one electric motor may be in communication with a down hole telemetry system. The at least one electric motor may be an AC motor, a universal motor, a stepper motor, a three-phase AC induction motor, a three-phase AC synchronous motor, a two-phase AC servo motor, a single-phase AC induction motor, a single-phase AC synchronous motor, a torque motor, a permanent magnet motor, a DC motor, a brushless DC motor, a coreless DC motor, a linear motor, a doubly- or singly-fed motor, or combinations thereof.

In some aspects of the invention, a drill bit comprises a bit body intermediate a shank and a working face comprising at least one cutting insert. A bore is formed in the working face and is substantially co-axial with an axis of rotation of the drill bit. A jack element is secured within the bore and has a pointed distal end brazed to the shaft. The pointed distal end comprises diamond with a thickness of at least 100 inches.

The diamond may be bonded to a carbide substrate which is brazed to the shaft. The diamond may be thicker than the substrate. The pointed distal end may be off set from a central axis of the shaft. An axis of the pointed distal end may form an angle of less than 10 degrees with an axis of the shaft. The pointed distal end may comprise an apex with a radius of 0.050 to 0.200 inches. In some embodiments, the apex may comprise a 0.080 to 0.160 inch radius. The pointed distal end may comprise an included angle of 40 to 50 degrees. The diamond may be 0.130 to 0.250 thick. The substrate may comprise a larger diameter than the shaft. The at least cutting insert may intrude upon the bore.

In another aspect of the invention, a method for making a drill bit may include providing a bit body intermediate a shank and a working face comprising at least one cutting insert and a bore formed in the working face substantially co-axial with an axis of rotation of the drill bit; securing a jack element secured within the bore which comprises a shaft; and brazing a pointed distal end brazed to the shaft which pointed distal end comprises diamond with a thickness of at least 0.100 inches. In some embodiments, a region of the substrate adjacent the braze may be ground to reduce or eliminate any cracks that may have been formed during manufacturing or brazing. In some embodiments, the substrate may be brazed to the shaft while the shaft is being brazed within the bore.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective diagram of an embodiment of a drill string suspended in a bore hole.

FIG. 2 is a perspective diagram of an embodiment of a drill bit.

FIG. 3 is a cross-sectional diagram of an embodiment of a drill bit.

FIG. 4 is a cross-sectional diagram of another embodiment of a drill bit.

FIG. 5 is a cross-sectional diagram of another embodiment of a drill bit.

FIG. 6 is a cross-sectional diagram of another embodiment of a drill bit.

FIG. 7 is a cross-sectional diagram of another embodiment of a drill bit.

FIG. 8 is a cross-sectional diagram of another embodiment of a drill bit.

FIG. 9 is a cross-sectional diagram of an embodiment of a steering mechanism.

FIG. 10 is a cross-sectional diagram of another embodiment of a jack element.

FIG. 11 is a cross-sectional diagram of another embodiment of a jack element.

FIG. 12 is a cross-sectional diagram of an embodiment of an assembly for HPHT processing.

FIG. 13 is a cross-sectional diagram of another embodiment of a cutting element

FIG. 14 is a cross-sectional diagram of another embodiment of a cutting element.

FIG. 15 is a cross-sectional diagram of another embodiment of a cutting element.

FIG. 16 is a diagram of an embodiment of test results.

FIG. 17 a is a cross-sectional diagram of another embodiment of a cutting element.

FIG. 17 b is a cross-sectional diagram of another embodiment of a cutting element.

FIG. 17 c is a cross-sectional diagram of another embodiment of a cutting element.

FIG. 17 d is a cross-sectional diagram of another embodiment of a cutting element.

FIG. 17 e is a cross-sectional diagram of another embodiment of a cutting element.

FIG. 17 f is a cross-sectional diagram of another embodiment of a cutting element.

FIG. 17 g is a cross-sectional diagram of another embodiment of a cutting element.

FIG. 17 h is a cross-sectional diagram of another embodiment of a cutting element.

FIG. 18 is a diagram of an embodiment of a method for making a drill bit.

DETAILED DESCRIPTION OF THE INVENTION AND THE PREFERRED EMBODIMENT

Referring now to the figures, FIG. 1 is a perspective diagram of an embodiment of a drill string 102 suspended by a derrick 101. A bottom-hole assembly 103 is located at the bottom of a bore hole 104 and comprises a rotary drag bit 100. As the drill bit 100 rotates down hole the drill string 102 advances farther into the earth. The drill string 102 may penetrate soft or hard subterranean formations 105.

FIGS. 2 through 3 disclose a drill bit 100 of the present invention. The drill bit 100 comprises a shank 200 which is adapted for connection to a down hole tool string such as drill string 102 comprising drill pipe, drill collars, heavy weight pipe, reamers, jars, and/or subs. In some embodiments coiled tubing or other types of tool string may be used. The drill bit 100 of the present invention is intended for deep oil and gas drilling, although any type of drilling application is anticipated such as horizontal drilling, geothermal drilling, mining, exploration, on and off-shore drilling, directional drilling, water well drilling and any combination thereof. The bit body 201 is attached to the shank 200 and comprises an end which forms a working face 206. Several blades 202 extend outwardly from the bit body 201, each of which may comprise a plurality of cutting inserts 203. A drill bit 100 most suitable for the present invention may have at least three blades 202; preferably the drill bit 100 will have between three and seven blades 202. The blades 202 collectively form an inverted conical region 303. Each blade 202 may have a cone portion 350, a nose portion 302, a flank portion 301, and a gauge portion 300. Cutting inserts 203 may be arrayed along any portion of the blades 202, including the cone portion 350, nose portion 302, flank portion 301, and gauge portion 300. A plurality of nozzles 204 are fitted into recesses 205 formed in the working face 206. Each nozzle 204 may be oriented such that a jet of drilling mud ejected from the nozzles 204 engages the formation 105 before or after the cutting inserts 203. The jets of drilling mud may also be used to clean cuttings away from the drill bit 100. In some embodiments, the jets may be used to create a sucking effect to remove drill bit cuttings adjacent the cutting inserts 203 by creating a low pressure region within their vicinities.

The jack element 305 comprises a hard surface of 1 least 63 HRc. The hard surface may be attached to the distal end 307 of the jack element 305, but it may also be attached to any portion of the jack element 305. The jack element 305 may also comprise a cylindrical shaft 306 which is adapted to fit within a bore 304 disposed in the working face 206 of the drill bit 100. The jack element 305 may be retained in the bore through the use of at least one retaining element 308. The retaining element 308 may comprise a cutting insert 203, a snap ring, a cap, a sleeve or combinations thereof. The retaining element 308 retains the jack bit 305 in the bore 304 by intrusion of a diameter of the bore 304. FIGS. 2 through 3 disclose a drill bit 100 that utilizes at least one cutting insert 203 as a retaining element 308 to retain the jack element 305 within the bore 304. At least one of the retaining elements may intrude on the diameter by 0.010 to 1 inch. In some embodiments, the at least one retaining element may intrude by 0.300 to 0.700 inches into the bore diameter. In some embodiments, the retaining element intrudes by within 5 to 35 percent of the bore diameter.

In some embodiments, the jack element 305 is made of the material of at least 63 HRc. In the preferred embodiment, the jack element 305 comprises tungsten carbide with polycrystalline diamond bonded to its distal end 307. In some embodiments, the distal end 307 of the jack element 305 comprises a diamond or cubic boron nitride surface. The diamond may be selected from group consisting of polycrystalline diamond, natural diamond, synthetic diamond, vapor deposited diamond, silicon bonded diamond, cobalt bonded diamond, thermally stable diamond, polycrystalline diamond with a cobalt concentration of 1 to 40 weight percent, infiltrated diamond, layered diamond, polished diamond, course diamond, fine diamond or combinations thereof. In some embodiments, the jack element 305 is made primarily from a cemented carbide with a binder concentration of 1 to 40 weight percent, preferably of cobalt.

The working face 206 of the drill bit 100 may be made of a steel, a matrix, or a carbide as well. The cutting inserts 203 or distal end 307 of the jack element 305 may also be made out of hardened steel or may comprise a coating of chromium, titanium, aluminum or combinations thereof.

One long standing problem in the industry is that cutting inserts 203, such as diamond cutting inserts 203, chip or wear in hard formations 105 when the drill bit 100 is used too aggressively. To minimize cutting insert 203 damage, the drillers will reduce the rotational speed of the bit 100, but all too often, a hard formation 105 is encountered before it is detected and before the driller has time to react. The jack element 305 may limit the depth of cut that the drill bit 100 may achieve per rotation in hard formations 105 because the jack element 305 actually jacks the drill bit 100 thereby slowing its penetration in the unforeseen hard formations 105. If the formation 105 is soft, the formation 105 may not be able to resist the weight on bit (WOB) loaded to the jack element 305 and a minimal amount of jacking may take place. But in hard formations 105, the formation 105 may be able to resist the jack element 305, thereby lifting the drill bit 100 as the cutting inserts 203 remove a volume of the formation 105 during each rotation. As the drill bit 100 rotates and more volume is removed by the cutting inserts 203 and drilling mud, less WOB will be loaded to the cutting inserts 203 and more WOB will be loaded to the jack element 305. Depending on the hardness of the formation 105, enough WOB will be focused immediately in front of the jack element 305 such that the hard formation 105 will compressively fail, weakening the hardness of the formation and allowing the cutting inserts 203 to remove an increased volume with a minimal amount of damage.

Now referring to various embodiments of the present invention as disclosed in FIG. 4 through 7. FIG. 4 discloses a drill bit 100 with a bore 304 disposed in the working face 206. The shaft 306 of the jack element 305 is disposed within the bore 304. At least one recess has been formed in the circumference of the bore 304 such that a snap ring may be placed within the bore 304 retaining the shaft 306 within the bore 304.

FIG. 5 discloses a jack element 305 retained in a bore 304 by a cap retaining element 308. The cap retaining element 308 may be threaded, brazed, bolted, riveted or press-fitted to the working surface 206 of the drill bit 100. The surface of the retaining element 308 may be complimentary to the jack element 305. The retaining element 308 may also have a bearing surface. In some embodiments the drill bit body is made of steel or matrix.

Now referring to FIG. 6, the shaft 306 may have at least one recess to accommodate the reception of the retaining element 308. The retaining element 308 is a snap ring that retains the jack bit 305 in the bore 304 by expanding into the recess formed in the bore 304 and into the recess formed in the shaft 306. A sleeve may be used as a retaining element 308 as disclosed in FIG. 7.

The drill bit 100 may comprise a plurality of electric motors 800 adapted to alter the axial orientation of the shaft 306, as in the embodiment of FIGS. 8 and 9. The motors 800 may be disposed within recesses 803 formed within the bore 304 wall. They may also be disposed within a collar support secured to the bore 304 wall. The plurality of electric motors may comprise an AC motor, a universal motor, a stepper motor, a three-phase AC induction motor, a three-phase AC synchronous motor, a two-phase AC servo motor, a single-phase AC induction motor, a single-phase AC synchronous motor, a torque motor, a permanent magnet motor, a DC motor, a brushless DC motor, a coreless DC motor, a linear motor, a doubly- or singly-fed motor, or combinations thereof.

Each electric motor 800 may comprise a protruding threaded pin 801 which extends or retracts according to the rotation of the motor 800. The threaded pin 801 may comprise an end element 804 such that the shaft 306 is axially fixed when all of the end elements 804 are contacting the shaft 306. The axial orientation of the shaft 306 may be altered by extending the threaded pin 801 of one of the motors 800 and retracting the threaded pin 801 of the other motors 800. Altering the axial orientation of the shaft 306 may aid in steering the tool string 102.

The electric motors 800 may be powered by a turbine, a battery, or a power transmission system from the surface or down hole. The electric motors 800 may also be in communication 802 with a downhole telemetry system.

FIG. 10 discloses a jack element with a substrate 1300 with a larger diameter than the shaft 2005. The pointed distal end may comprise an included angle 2006 between 40-50 degrees. FIG. 11 discloses a substrate 1300 which is brazed to an interface 2007 of the shaft 2006 which is non-perpendicular to a central axis 2008 of the shaft 2005, thus a central axis 2009 of the pointed distal end forms an angle 2010 of less than 10 degrees with the central axis 2008 of the shaft 2005. The off set distal end may be useful for steering the drill bit along curved trajectories.

FIG. 12 is a cross-sectional diagram of an embodiment for a high pressure high temperature (HPHT) processing assembly 1400 comprising a can 1401 with a cap 1402. At least a portion of the can 1401 may comprise niobium, a niobium alloy, a niobium mixture, another suitable material, or combinations thereof. At least a portion of the cap 1402 may comprise a metal or metal alloy.

A can such as the can of FIG. 12 may be placed in a cube adapted to be placed in a chamber of a high temperature high pressure apparatus. Prior to placement in a high temperature high pressure chamber the assembly may be placed in a heated vacuum chamber to remove the impurities from the assembly. The chamber may be heated to 1000 degrees long enough to vent the impurities that may be bonded to superhard particles such as diamond which may be disposed within the can. The impurities may be oxides or other substances from the air that may readily bond with the superhard particles. After a reasonable venting time to ensure that the particles are clean, the temperature in the chamber may increase to melt a sealant 410 located within the can adjacent the lids 1412, 1408. As the temperature is lowered the sealant solidifies and seals the assembly. After the assembly has been sealed it may undergo HPHT processing producing a cutting element with an infiltrated diamond working end and a metal catalyst concentration of less than 5 percent by volume which may allow the surface of the diamond working end to be electrically insulating.

The assembly 1400 comprises a can 1401 with an opening 1403 and a substrate 1300 lying adjacent a plurality of super hard particles 406 grain size of 1 to 100 microns. The super hard particles 1406 may be selected from the group consisting of diamond, polycrystalline diamond, thermally stable products, polycrystalline diamond depleted of its catalyst, polycrystalline diamond having nonmetallic catalyst, cubic boron nitride, cubic boron nitride depleted of its catalyst, or combinations thereof. The substrate 1300 may comprise a hard metal such as carbide, tungsten-carbide, or other cemented metal carbides. Preferably, the substrate 1300 comprises a hardness of at least 58 HRc.

A stop off 1407 may be placed within the opening 1403 of the can 1401 in-between the substrate 1300 and a first lid 1408. The stop off 1407 may comprise a material selected from the group consisting of a solder/braze stop, a mask, a tape, a plate, and sealant flow control, boron nitride, a non-wettable material or a combination thereof. In one embodiment the stop off 1407 may comprise a disk of material that corresponds with the opening of the can 1401. A gap 1409 between 0.005 to 0.050 inches may exist between the stop off 1407 and the can 1401. The gap 1409 may support the outflow of contamination while being small enough size to prevent the flow of a sealant 1410 into the mixture 1404. Various alterations of the current configuration may include but should not be limited to; applying a stop off 1407 to the first lid 1408 or can by coating, etching, brushing, dipping, spraying, silk screening painting, plating, baking, and chemical or physical vapor deposition techniques. The stop off 1407 may in one embodiment be placed on any part of the assembly 1400 where it may be desirable to inhibit the flow of the liquefied sealant 1410.

The first lid 1408 may comprise niobium or a niobium alloy to provide a substrate that allows good capillary movement of the sealant 1410. After the first lid 1408 is installed within the can, the walls 1411 of the can 1401 may be folded over the first lid 1408. A second lid 1412 may then be placed on top of the folded walls 1401. The second lid 1412 may comprise a material selected from the group consisting of a metal or metal alloy. The metal may provide a better bonding surface for the sealant 1410 and allow for a strong bond between the lids 1408, 1412, can 1401 and a cap 1402. Following the second lid 1412 a metal or metal alloy cap 1402 may be placed on the can 1401.

Now referring to FIG. 13, the substrate 1300 comprises a tapered surface 1500 starting from a cylindrical rim 1504 of the substrate and ending at an elevated, flatted, central region 1501 formed in the substrate. The diamond working end 1506 comprises a substantially pointed geometry 1700 with a sharp apex 1502 comprising a radius of 0.050 to 0.125 inches. In some embodiments, the radius may be 0.900 to 0.110 inches. It is believed that the apex 1502 is adapted to distribute impact forces across the flatted region 1501, which may help prevent the diamond working end 1506 from chipping or breaking. The diamond working end 1506 may comprise a thickness 1508 of 0.100 to 0.500 inches from the apex to the flatted region 1501 or non-planar interface, preferably from 0.125 to 0.275 inches. The diamond working end 1506 and the substrate 1300 may comprise a total thickness 1507 of 0.200 to 0.700 inches from the apex 1502 to a base 1503 of the substrate 1300. The sharp apex 1502 may allow the drill bit to more easily cleave rock or other formations.

The pointed geometry 1700 of the diamond working end 506 may comprise a side which forms a 35 to 55 degree angle 555 with a central axis 304 of the cutting element 208, though the angle 555 may preferably be substantially 45 degrees. The included angle may be a 90 degree angle, although in some embodiments, the included angle is 85 to 95 degrees.

The pointed geometry 1700 may also comprise a convex side or a concave side. The tapered surface of the substrate may incorporate nodules 1509 at the interface between the diamond working end 1506 and the substrate 1300, which may provide more surface area on the substrate 1300 to provide a stronger interface. The tapered surface may also incorporate grooves, dimples, protrusions, reverse dimples, or combinations thereof. The tapered surface may be convex, as in the current embodiment, though the tapered surface may be concave.

Comparing FIGS. 13 and 15, the advantages of having a pointed apex 1502 as opposed to a blunt apex 1505 may be seen. FIG. 13 is a representation of a pointed geometry 1700 which was made by the inventors of the present invention, which has a 0.094 inch radius apex and a 0.150 inch thickness from the apex to the non-planar interface. FIG. 5b is a representation of another geometry also made by the same inventors comprising a 0.160 inch radius apex and 0.200 inch thickness from the apex to the non-planar geometry. The cutting elements were compared to each other in a drop test performed at Novatek International, Inc. located in Provo, Utah. Using an Instron Dynatup 9250G drop test machine, the cutting elements were secured in a recess in the base of the machine burying the substrate 1300 portions of the cutting elements and leaving the diamond working ends 1506 exposed. The base of the machine was reinforced from beneath with a solid steel pillar to make the structure more rigid so that most of the impact force was felt in the diamond working end 1506 rather than being dampened. The target 1510 comprising tungsten carbide 16% cobalt grade mounted in steel backed by a 19 kilogram weight was raised to the needed height required to generate the desired potential force, then dropped normally onto the cutting element. Each cutting element was tested at a starting 5 joules, if the elements withstood joules they were retested with a new carbide target 1510 at an increased increment of 10 joules the cutting element failed. The pointed apex 1502 of FIG. 13 surprisingly required about 5 times more joules to break than the thicker geometry of FIG. 15.

It is believed that the sharper geometry of FIG. 13 penetrated deeper into the tungsten carbide target 1510, thereby allowing more surface area of the diamond working ends 1506 to absorb the energy from the falling target by beneficially buttressing the penetrated portion of the diamond working ends 1506 effectively converting bending and shear loading of the substrate into a more beneficial compressive force drastically increasing the load carrying capabilities of the diamond working ends 1506. On the other hand it is believed that since the embodiment of FIG. 15 is blunter he apex hardly penetrated into the tungsten carbide target 1510 thereby providing little buttress support to the substrate and caused the diamond working ends 1506 to fail in shear/bending at a much lower load with larger surface area using the same grade of diamond and carbide. The average embodiment of FIG. 13 broke at about 130 joules while the average geometry of FIG. 15 broke at about 24 joules. It is believed that since the load was distributed across a greater surface area in the embodiment of FIG. 13 it was capable of withstanding a greater impact than that of the thicker embodiment of FIG. 15.

Surprisingly, in the embodiment of FIG. 13, when the super hard geometry 1700 finally broke, the crack initiation point 1550 was below the radius of the apex. This is believed to result from the tungsten carbide target pressurizing the flanks of the pointed geometry 1700 (number not shown in the FIG.) in the penetrated portion, which results in the greater hydrostatic stress loading in the pointed geometry 1700. It is also believed that since the radius was still intact after the break, that the pointed geometry 1700 will still be able to withstand high amounts of impact, thereby prolonging the useful life of the pointed geometry 1700 even after chipping.

FIG. 16 illustrates the results of the tests performed by Novatek, International, Inc. As can be seen, three different types of pointed insert geometries were tested. This first type of geometry is disclosed in FIG. 14 which comprises a 0.035 inch super hard geometry and an apex with a 0.094 inch radius. This type of geometry broke in the 8 to 15 joules range. The blunt geometry with the radius of 0.160 inches and a thickness of 0.200, which the inventors believed would outperform the other geometries broke, in the 20-25 joule range. The pointed geometry 1700 with the 0.094 thickness and the 0.150 inch thickness broke at about 130 joules. The impact force measured when the super hard geometry with the 0.160 inch radius broke was 75 kilo-newtons. Although the Instron drop test machine was only calibrated to measure up to 88 kilo-newtons, which the pointed geometry 700 exceeded when it broke, the inventors were able to extrapolate that the pointed geometry 700 probably experienced about 105 kilo-newtons when it broke.

As can be seen, super hard material 1506 having the feature of being thicker than 0.100 inches or having the feature of a 0.075 to 0.125 inch radius is not enough to achieve the diamond working end's 1506 optimal impact resistance, but it is synergistic to combine these two features. In the prior art, it was believed that a sharp radius of 0.075 to 0.125 inches of a super hard material such as diamond would break if the apex were too sharp, thus rounded and semispherical geometries are commercially used today.

The performance of the present invention is not presently found in commercially available products or in the prior art. Inserts tested between 5 and 20 joules have been acceptable in most commercial applications, but not suitable for drilling very hard rock formations

FIGS. 17 a through 17g disclose various possible embodiments comprising different combinations of tapered surface 1500 and pointed geometries 1700. FIG. 17a illustrates the pointed geometry with a concave side 1750 and a continuous convex substrate geometry 1751 at the interface 1500. FIG. 17b comprises an embodiment of a thicker super hard material 1752 from the apex to the non-planar interface, while still maintaining this radius of 0.075 to 0.125 inches at the apex. FIG. 17c illustrates grooves 1763 formed in the substrate to increase the strength of interface. FIG. 17d illustrates a slightly concave geometry at the interface 1753 with concave sides. FIG. 17e discloses slightly convex sides 1754 of the pointed geometry 1700 while still maintaining the 0.075 to 0.125 inch radius. FIG. 17f discloses a flat sided pointed geometry 1755. FIG. 17g discloses concave and convex portions 1757, 1756 of the substrate with a generally flatted central portion.

Now referring to FIG. 17h , the diamond working end 1506 (number not shown in the FIG.) may comprise a convex surface comprising different general angles at a lower portion 1758, a middle portion 1759, and an upper portion 1760 with respect to the central axis of the tool. The lower portion 1758 of the side surface may be angled at substantially 25 to 33 degrees from the central axis, the middle portion 1759, which may make up a majority of the convex surface, may be angled at substantially 33 to 40 degrees from the central axis, and the upper portion 1760 of the side surface may be angled at about 40 to 50 degrees from the central axis.

In another aspect of the invention, a method 2003 for making a drill bit may include providing 2000 a bit body intermediate a shank and a working face comprising at least one cutting insert and a bore formed in the working face substantially co-axial with an axis of rotation of the drill bit; securing 2001 a jack element secured within the bore which comprises a shaft; and brazing 2002 a pointed distal end brazed to the shaft which pointed distal end comprises diamond with a thickness of at least 0.100 inches. In some embodiments, a region of the substrate adjacent the braze may be ground to reduce or eliminate any cracks that may have been formed during manufacturing or brazing. In some embodiments, the substrate may be brazed to the shaft while the shaft is being brazed within the bore.

Whereas the present invention has been described in particular relation to the drawings attached hereto, it should be understood that other and further modifications apart from those shown or suggested herein, may be made within the scope and spirit of the present invention.

Claims

1. A drill bit, comprising: a bit body intermediate a shank and a working face comprising at least one cutting insert;a bore formed in the working face substantially co-axial with an axis of rotation of the drill bit;a jack element secured within the bore and comprising a shaft and a pointed distal end brazed to the shaft; andthe pointed distal end comprises diamond with a thickness of at least 0.100 inches;wherein the at least one cutting insert intrudes upon the bore.

2. The bit of claim 1, wherein the diamond is bonded to a carbide substrate which is brazed to the shaft.

3. The bit of claim 2, wherein the diamond is thicker than the substrate.

4. The bit of claim 1, wherein the pointed distal end is off set from a central axis of the shaft.

5. The bit of claim 1, wherein an axis of the pointed distal end forms an angle of less than 10 degrees with an axis of the shaft.

6. The bit of claim 1, wherein the pointed distal end comprises an apex with a radius of 0.050 to 0.200 inches.

7. The bit of claim 6, wherein apex comprises a radius of 0.080 to 0.160 inches.

8. The bit of claim 1, wherein the pointed distal end comprises an included angle of 40 to 50 degrees.

9. The bit of claim 1, wherein the diamond is 0.130 to 0.250 thick.

10. The bit of claim 1, wherein the substrate comprises a larger diameter than the shaft.

11. A method for making a drill bit, comprising: providing a bit body intermediate a shank and a working face comprising at least one cutting insert and a bore formed in the working face substantially co-axial with an axis of rotation of the drill bit;securing a jack element secured within the bore which comprises a shaft; andbrazing a pointed distal end brazed to the shaft which pointed distal end comprises diamond with a thickness of at least 0.100 inches;wherein the at least one cutting insert intrudes upon the bore.

12. The method of claim 11, wherein the pointed distal end comprises a carbide substrate.

13. The method of claim 12, wherein a region of the substrate adjacent the braze is ground.

14. The method of claim 12, wherein the substrate is brazed to the shaft while the shaft is being brazed within the bore.