Conjoined polycrystalline diamond compact drill teeth and oil and gas drill bit employing same

Abstract

The utility model belongs to petroleum drilling and production equipment technical field discloses a kind of polycrystalline diamond composite drill teeth of conjoined type, including the block body being connected by hard alloy layer and polycrystalline diamond layer, the side surface of the combination position of hard alloy layer and polycrystalline diamond layer is as the side surface of block body, part of block body side surface is as working surface, is equipped with two above cutting unit.The utility model further discloses a kind of oil and gas drilling using drill bit, drill bit is arranged with conjoined type polycrystalline diamond composite drill teeth.The utility model can be realized in the case where local collapse occurs, drill bit can also continue to cover well bottom, realize continued drilling by the arrangement of conjoined type polycrystalline diamond composite drill teeth.

Description

Technical Field

[0001] This utility model belongs to the technical field of oil drilling and production equipment, and relates to diamond composite drill teeth for drill bits, especially to integrated polycrystalline diamond composite drill teeth and drill bits for oil and gas drilling. Background Technology

[0002] Global demand for fossil fuels will continue to increase, and in the foreseeable future, the energy available for human life and production will still mainly come from fossil fuels such as oil and natural gas. As the density and depth of oil and gas drilling continue to increase, the requirements for the number and performance of drill bits and teeth used in oil and gas drilling are also constantly increasing.

[0003] Polycrystalline diamond cutters (PDC) are also known in the industry as petroleum composite cutters, diamond composite cutters, or diamond drill bits. Most oil and gas drilling bits utilize PDC cutters to cut (scrape) underground rock formations, offering advantages such as high efficiency, energy saving, significantly improved safety, and reduced drilling costs. However, the performance requirements for PDC cutters are stringent, and related technologies have become core technologies in oil and gas geological drilling. The performance of PDC cutters is a key factor directly affecting the efficiency, cost, and safety of oil and gas drilling.

[0004] PDC drill bits are generally made of a polycrystalline diamond layer (1-4 mm thick, 8-25 mm in diameter) and a WC-Co cemented carbide matrix, sintered under high temperature (approximately 1500 °C) and high pressure (approximately 60,000 atmospheres). Typically, drill bits used for oil and gas drilling consist of two or more cutting edges, such as... Figure 1 As shown, each cutter wing has multiple independently fixed PDC drill teeth, and each PDC drill tooth fixed on the cutter wing becomes a working unit for scraping rock. After half a century of application in oil and gas drilling and production, the use of PDC drill teeth in the industry has formed a series of common specifications, such as: 0808, 1108, 1308, 1613, 1916, 2513, etc. (the first two digits represent the diameter, and the last two digits represent the height, in mm). The overall shape of traditional PDC drill teeth is cylindrical, with a diameter between 8 mm and 25 mm and a height between 5 mm and 25 mm.

[0005] With this tooth arrangement, the drill bit can achieve complete coverage of the bottom of the well during drilling. When the composite blades wear down or suffer impact damage, the cutting structure of the drill bit is insufficient to cover the entire bottom of the well (the drilling front face). This causes the drill bit body to come into contact with the formation rock and wear down rapidly, leading to drill bit failure and ultimately, the scrapping of the drill bit. Utility Model Content

[0006] The purpose of this invention is to address the shortcomings of existing technologies by providing an integrated polycrystalline diamond composite drill bit with a large contact surface and high connection strength with the drill bit body. This can delay the wear of the drill bit body, thereby improving the overall service life of the drill bit and reducing the risk of failure.

[0007] Another objective of this invention is to provide an oil and gas drilling bit employing the aforementioned integrated polycrystalline diamond composite drill teeth.

[0008] To achieve the above objectives, the present invention adopts the following technical solution.

[0009] This utility model provides an integrated polycrystalline diamond composite drill bit, comprising a block composed of a cemented carbide layer and a polycrystalline diamond layer fixedly connected, the side where the cemented carbide layer and the polycrystalline diamond layer are joined serves as the side of the block, a portion of the side of the block serves as the working surface, and two or more cutting units are provided thereon.

[0010] In one possible implementation, the cutting unit is wedge-shaped, conical, spherical, cylindrical, or a protruding structure formed by two adjacent arcuate grooves extending inward from the working surface of the block.

[0011] In one possible implementation, all cutting elements are arranged in an arc or linear pattern, depending primarily on the shape of the drill bit body and the position of the drill teeth.

[0012] In one possible implementation, the thickness of the cemented carbide layer is 0-20 mm; the thickness of the polycrystalline diamond layer is 1 mm-10 mm.

[0013] In one feasible approach, the block is designed with multiple independent crown profile cutting structures to enable the continuous drill teeth to effectively cut the formation. This requires multiple mechanical equilibrium design calculations to obtain the required cutting units. The main function of the portion of the block outside the cutting units is to connect the various cutting units into a single unit. The dimensions and structure of this portion are not limited by this invention and can be set according to design requirements.

[0014] In the preferred implementation, the dimensions of each cutting unit may be the same or different, with an equivalent diameter ranging from 2mm to 20mm. An equivalent diameter refers to the diameter of an irregularly shaped object whose volume is equivalent to that of a sphere.

[0015] In the preferred implementation, when all cutting units are arranged in an arc shape, the angle between the axes of two adjacent cutting units is 5°-55°; when all cutting units are arranged in a linear shape, the distance between the axes of two adjacent cutting units is 3mm-25mm; the height of the cutting unit refers to the distance between the crest and trough, which is 1mm-10mm; the half-width of the cutting unit refers to the width when the cutting unit is half its height, which is 2mm-15mm.

[0016] In the preferred implementation, the number of cutting units is 2-12.

[0017] In a preferred implementation, the polycrystalline diamond layer side edge of each cutting unit is designed with a 0°-60° chamfer to control the wear rate of the cutting unit; the smaller the chamfer, the lower the wear rate, but the lower the cutting efficiency; and vice versa. Furthermore, the polycrystalline diamond layer side is also inclined to both sides along the axis of each cutting unit, forming a 100°-180° protrusion to improve cutting efficiency.

[0018] Compared with the prior art, the integrated polycrystalline diamond composite drill bit provided by this utility model has the following beneficial effects:

[0019] (1) The integrated polycrystalline diamond composite drill bit provided by this utility model has two or more cutting units on a polycrystalline diamond layer and a cemented carbide layer that are connected as one piece; after being fixed on the drill bit blade, it has a large contact surface with the drill bit body and a high connection strength, and the drill bit body has a large holding force on the integrated polycrystalline diamond composite drill bit.

[0020] (2) The bottom of the multiple cutting units of the integrated polycrystalline diamond composite drill bit provided by this utility model is connected by a polycrystalline diamond layer and a cemented carbide matrix. After the upper cutting unit is worn or damaged by impact, the polycrystalline diamond layer and cemented carbide layer at the bottom can delay the wear of the drill bit body, thereby improving the overall service life of the drill bit and reducing the risk of failure.

[0021] (3) The integrated polycrystalline diamond composite drill bit provided by this utility model has multiple cutting units, which can be easily and quickly fixed on the drill bit, greatly improving the drill bit preparation efficiency and reducing the drill bit preparation cost. It is also beneficial to the design and processing of drill bit shape, and can facilitate the layout of cutting units for specific rock layers, thereby improving rock breaking efficiency.

[0022] This utility model also provides a drill bit for oil and gas drilling, wherein the drill bit is equipped with integrated polycrystalline diamond composite drill teeth as described in any of the above-mentioned feasible embodiments. Through the integrated polycrystalline diamond composite drill teeth, even in the event of localized breakage, the drill bit can continue to cover the bottom of the well, enabling continued drilling.

[0023] In one implementation, each blade of the drill bit has an integrated polycrystalline diamond composite drill bit arranged in the front row. When drilling highly abrasive formations (including but not limited to sandstone, igneous rocks, etc.) using integrated polycrystalline diamond composite drill bits as main teeth, the coverage ratio of the bottom of the well by the integrated drill bits is much greater than that of traditional single-tooth spread drill bits, which can significantly increase the drilling footage.

[0024] In one possible implementation, one or more cutter wings of the drill bit are arranged with integrated polycrystalline diamond composite drill teeth between the rear row or the front row and the rear row. Using the integrated polycrystalline diamond composite drill teeth as auxiliary teeth, once a single tooth in the front row is damaged, the integrated drill tooth structure can participate in cutting the formation, thereby achieving a higher cut than traditional single-tooth drill bits.

[0025] In one possible implementation, a plurality of discrete PDC drill teeth are arranged in the front row of one or more cutter wings of the drill bit; an integral polycrystalline diamond composite drill tooth fixed to the cutter wings is arranged below the discrete PDC drill teeth; and the groove on the integral polycrystalline diamond composite drill tooth is adapted to the contour shape of the discrete PDC drill teeth. If the discrete PDC drill tooth, which serves as the main cutting structure, is damaged and detaches from the annular groove, the integral drill tooth can contact the formation and become the new main cutting structure to continue drilling.

[0026] The PDC (polycrystalline diamond) composite drill teeth used on different cutter blades may have the same or different PDC crown profile structures. For integrated polycrystalline diamond composite drill teeth, the side of the block facing the working face is used to fix it to the drill bit. Attached Figure Description

[0027] Figure 1 A three-dimensional view of the integrated polycrystalline diamond composite drill bit provided in Example 1;

[0028] Figure 2 This is a front view of the integrated polycrystalline diamond composite drill bit provided in Example 1;

[0029] Figure 3 A three-dimensional view of the integrated polycrystalline diamond composite drill bit provided in Example 2;

[0030] Figure 4 This is a front view of the integrated polycrystalline diamond composite drill bit provided in Example 2;

[0031] Figure 5 A three-dimensional view of the integrated polycrystalline diamond composite drill bit provided in Example 3;

[0032] Figure 6 This is a front view of the integrated polycrystalline diamond composite drill bit provided in Example 3;

[0033] Figure 7 A three-dimensional view of the integrated polycrystalline diamond composite drill bit provided in Example 4;

[0034] Figure 8 This is a front view of the integrated polycrystalline diamond composite drill bit provided in Example 4;

[0035] Figure 9 This is a schematic diagram of the drill bit structure used in the oil and gas drilling provided in Example 5;

[0036] Figure 10 A schematic diagram of a discrete PDC drill tooth structure;

[0037] Figure 11 This is a schematic diagram of the drill bit structure used in the oil and gas drilling provided in Example 6;

[0038] Figure 12 This is a schematic diagram of the drill bit structure used in the oil and gas drilling provided in Example 7;

[0039] In the figure, 1-integrated polycrystalline diamond composite drill bit a; 11-first cemented carbide layer; 12-first polycrystalline diamond layer; 13-first cutting unit; 2-integrated polycrystalline diamond composite drill bit b; 21-second cemented carbide layer; 22-second polycrystalline diamond layer; 23-second cutting unit; 3-integrated polycrystalline diamond composite drill bit c; 31-third cemented carbide layer; 32-third polycrystalline diamond layer; 33-third cutting unit; 4-integrated polycrystalline diamond composite drill bit d; 41-fourth polycrystalline diamond layer; 42-fourth cutting unit; 5-first drill bit body; 6-discrete PDC drill bit; 61-fifth cemented carbide layer; 62-fifth polycrystalline diamond layer; 7-tapered polycrystalline diamond drill bit; 8-second drill bit body; 9-third drill bit body. Detailed Implementation

[0040] The following will provide embodiments of this utility model with reference to the accompanying drawings, and further elaborate and describe the technical solution of this utility model through these embodiments. The following embodiments are merely a part of the embodiments of this utility model. Based on the content of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0041] Example 1

[0042] This embodiment provides an integrated polycrystalline diamond composite drill bit a1, such as Figure 1 and Figure 2 As shown, it includes a block formed by a first cemented carbide layer 11 and a first polycrystalline diamond layer 12 fixedly connected; the side where the first cemented carbide layer 11 and the first polycrystalline diamond layer 12 are joined serves as the side of the block; a part of the side of the block serves as the working surface, and five first cutting units 13 are provided thereon; the part of the side of the block opposite to the working surface is a planar structure, which serves as the bottom of the drill teeth.

[0043] The first cemented carbide layer 11 is made of WC / Co cemented carbide, purchased externally, with the grade YG13 (containing 13% cobalt); the thickness of the first cemented carbide layer 11 is 6 mm. The thickness of the first polycrystalline diamond layer 12 is 3 mm.

[0044] Each of the first cutting units 13 has the same structure, being a wedge-shaped structure with an equivalent diameter of 8 mm. The top of each first cutting unit 13 is an arc surface, and adjacent first cutting units 13 are smoothly transitioned through an arc surface. The height h1 of each first cutting unit 13 is 10 mm, and its half-width d1 is 8 mm. All first cutting units 13 are arranged in an arc shape, and the angle θ1 between the axes of adjacent first cutting units 13 is 17°.

[0045] Furthermore, the first polycrystalline diamond layer side edge of each first cutting unit 13 is designed with a 20° chamfer; and the first polycrystalline diamond layer side is inclined to both sides along the axis of the first cutting unit 13 to form a 165.24° protrusion.

[0046] The aforementioned integrated polycrystalline diamond composite drill bit a1 can be processed by laser cutting or other methods on a cemented carbide layer / polycrystalline diamond layer with a diameter of 50mm.

[0047] Example 2

[0048] This embodiment provides an integrated polycrystalline diamond composite drill bit b2, such as Figure 3 and Figure 4 As shown, it includes a block formed by the bonding of a second cemented carbide layer 21 and a second polycrystalline diamond layer 22; the side where the second cemented carbide layer 21 and the second polycrystalline diamond layer 22 are bonded together serves as the side of the block; a portion of the side of the block serves as the working surface, on which nine second cutting units 23 are provided; the portion of the side of the block opposite to the working surface is a planar structure, serving as the bottom of the drill teeth.

[0049] The second cemented carbide layer 21 and the second polycrystalline diamond layer 22 are made of the same material as the first cemented carbide layer 11 and the first polycrystalline diamond layer 12 in Example 1; the thickness of the second cemented carbide layer 21 is 5 mm. The thickness of the second polycrystalline diamond layer 22 is 3 mm.

[0050] Each second cutting unit 23 has the same structure, being a wedge-shaped structure with an equivalent diameter of 4 mm. The top of each second cutting unit 23 is an arc surface, and adjacent second cutting units 23 are smoothly transitioned through arc surfaces. The height h2 of each second cutting unit 23 is 8 mm, and its half-width d2 is 4 mm. All second cutting units 23 are arranged in an arc shape, and the angle θ2 between the axes of adjacent second cutting units 23 is 10°.

[0051] The aforementioned integrated polycrystalline diamond composite drill bit b2 can be processed by laser cutting or other methods on a cemented carbide layer / polycrystalline diamond layer with a diameter of 70mm.

[0052] Example 3

[0053] This embodiment provides an integrated polycrystalline diamond composite drill bit c3, such as Figure 5 and Figure 6 As shown, it includes a block formed by the bonding of a third cemented carbide layer 31 and a third polycrystalline diamond layer 32; the side where the third cemented carbide layer 31 and the third polycrystalline diamond layer 32 are bonded together serves as the side of the block; a portion of the side of the block serves as the working surface, on which five third cutting units 33 are provided; the portion of the side of the block opposite to the working surface is a planar structure, serving as the bottom of the drill teeth.

[0054] The third cemented carbide layer 31 and the third polycrystalline diamond layer 32 are made of the same material as the first cemented carbide layer 11 and the first polycrystalline diamond layer 12 in Example 1; the thickness of the third cemented carbide layer 31 is 12 mm. The thickness of the third polycrystalline diamond layer 32 is 6 mm.

[0055] Each third cutting unit 33 has the same structure, being a semi-cylindrical structure with an equivalent diameter of 8mm. Adjacent third cutting units 33 are joined together. The height h3 of each third cutting unit 33 is 3mm, and its half-height width d3 is 8mm. All cutting units are arranged linearly, with a distance D between the axes of two adjacent third cutting units 33 of 10mm.

[0056] The aforementioned integrated polycrystalline diamond composite drill bit c3 can be processed on a 60mm diameter cemented carbide / polycrystalline diamond layer by means of laser cutting or other methods.

[0057] Example 4

[0058] This embodiment provides an integrated polycrystalline diamond composite drill bit d4, such as Figure 7 and Figure 8 As shown, it includes a fourth polycrystalline diamond layer 41; a portion of the side of the fourth polycrystalline diamond layer 41 serves as a working surface, and three fourth cutting units 42 are provided thereon; the portion of the side of the block opposite to the working surface serves as the bottom of the drill teeth.

[0059] The fourth polycrystalline diamond layer 41 is made of the same material as the first polycrystalline diamond layer 12 in Example 1; the thickness of the fourth polycrystalline diamond layer 41 is 8 mm.

[0060] Each fourth cutting unit 42 has the same structure, consisting of a protrusion formed by two adjacent arc-shaped grooves extending inward from the working surface of the block, with an equivalent diameter of 6 mm; the radius of the arc-shaped groove is 8 mm, and the depth is 8 mm. The height h4 of the fourth cutting unit 42 is 8 mm, and its half-width d4 is 6 mm. All fourth cutting units 42 are arranged in an arc shape; the angle θ4 between the axes of two adjacent fourth cutting units 42 is 30°.

[0061] The aforementioned integrated polycrystalline diamond composite drill bit d4 can be processed on a polycrystalline diamond layer with a diameter of 70mm by means of laser cutting or other methods.

[0062] In this embodiment, the integrated polycrystalline diamond composite drill bit d4 can be arranged below the traditional discrete PDC drill bit. Therefore, the discrete PDC drill bit is embedded in the arc-shaped groove. The working surface of the fourth polycrystalline diamond layer 41 and the bottom contour shape of the drill bit are adapted to the contact position of the drill bit.

[0063] Example 5

[0064] This embodiment provides a drill bit for oil and gas drilling, such as... Figure 9 As shown. The oil and gas drill bit includes a first drill bit body 5, which has six cutter wings arranged circumferentially. The first, third, and fifth rows of cutter wings are connected as one piece, while the second, fourth, and sixth rows of cutter wings are independently arranged. Each cutter wing of the first drill bit body 5 has three or more discrete PDC drill teeth 6 arranged in the front and rear rows, and a one-piece polycrystalline diamond composite drill tooth a1 provided in Example 1 is arranged between the two rows. In addition, a conical polycrystalline diamond drill tooth 7 is arranged in front of and behind the one-piece polycrystalline diamond composite drill tooth a1 on the second, fourth, and sixth rows of cutter wings.

[0065] The discrete PDC drill bit 6 adopts a conventional structure already disclosed in the art. Specifically, such as... Figure 10 As shown, the discrete PDC drill bit 6 has a cylindrical structure with a diameter of 16 mm. It includes a fifth cemented carbide layer 61 and a fifth polycrystalline diamond layer 62. The fifth cemented carbide layer 61 has a thickness of 10 mm, and the fifth polycrystalline diamond layer 62 has a thickness of 3.2 mm. The fifth cemented carbide layer 61 and the fifth polycrystalline diamond layer 62 are made of the same material as the first cemented carbide layer and the first polycrystalline diamond layer described earlier.

[0066] The advantage of the drill bit design used in the above-mentioned oil and gas drilling is that the drill bit can cover the bottom of the well with fewer teeth and obtain a higher mechanical drilling rate under the same drilling parameters (drilling pressure, rotation speed). Once the front row of single teeth is damaged, the rear row of integrated drill teeth structure can participate in cutting the formation, thereby obtaining a higher footage than the traditional single-tooth tooth distribution drill bit.

[0067] When drilling granite using the aforementioned oil and gas drilling tools and drill bits with the integrated polycrystalline diamond composite drill teeth a1 removed (traditional drill bits), the service life of the drill bits can be increased by more than 30%.

[0068] Example 6

[0069] This embodiment provides a drill bit for oil and gas drilling, such as... Figure 11As shown. The oil and gas drill bit includes a second drill bit body 8; the second drill bit body 8 has 6 cutter wings arranged circumferentially. The 1st, 3rd, and 5th rows of cutter wings are connected as one piece, while the 2nd, 4th, and 6th rows of cutter wings are set independently. Each cutter wing of the second drill bit body 9 has multiple continuous integrated polycrystalline diamond composite drill teeth b2 provided in Example 2 arranged in the front row. Each cutter wing also has two discrete PDC drill teeth 6 arranged in the rear row, and one or two conical polycrystalline diamond drill teeth 7 are arranged in front of and behind the discrete PDC drill teeth 6.

[0070] The advantage of the aforementioned oil and gas drilling bit design is that when drilling into highly abrasive formations (including but not limited to mudstone, sandstone, igneous rocks, etc.), the coverage ratio of the bottom of the well by the integrated drill teeth is much greater than that of the traditional single-tooth spread-tooth drill bit, which can significantly increase the drilling footage.

[0071] Using the aforementioned oil and gas drilling bit and the conventional bit in Example 5 for drilling mudstone, the mudstone drilling efficiency can be increased by more than 30%.

[0072] Example 7

[0073] This embodiment also provides a drill bit for oil and gas drilling, such as... Figure 12 As shown. The oil and gas drill bit includes a third drill bit body 9; the third drill bit body 9 has 6 cutter wings arranged circumferentially. The first, third, and fifth rows of cutter wings are connected as one piece, while the second, fourth, and sixth rows of cutter wings are set independently. Each cutter wing of the third drill bit body 9 has two or more discrete PDC drill teeth 6 arranged in the front and rear rows, and the front row side is embedded with the integrated polycrystalline diamond composite drill teeth d4 shown in Example 4, which are arranged along the direction of the cutter wings; the multiple discrete PDC drill teeth 6 in the front row of the cutter wings are simultaneously embedded in the grooves of the integrated polycrystalline diamond composite drill teeth d4. The rear rows of the second, fourth, and sixth rows of cutter wings have one or two conical polycrystalline diamond drill teeth 7 arranged in front and behind the discrete PDC drill teeth 6.

[0074] The advantage of the drill bit design used in the above-mentioned oil and gas drilling is that, after the discrete PDC drill bit, which is used as the main cutting structure, is damaged and detaches from the annular groove, the integrated drill bit can contact the formation and become the new main cutting structure to continue drilling.

[0075] When drilling granite using the aforementioned oil and gas drill bit and the conventional drill bit in Example 5, the drill bit service life can be increased by more than 25%.

Claims

1. A one-piece polycrystalline diamond composite drill bit, comprising a block formed by a cemented carbide layer and a polycrystalline diamond layer fixedly connected; the side where the cemented carbide layer and the polycrystalline diamond layer are bonded together serves as the side of the block; characterized in that, A portion of the side surface of the block serves as the working surface, with two or more cutting units.

2. The integral polycrystalline diamond composite drill bit according to claim 1, characterized in that, The dimensions of each cutting unit may be the same or different, with an equivalent diameter of 2mm-20mm.

3. The integral polycrystalline diamond composite drill bit according to claim 1, characterized in that, All cutting units are arranged in an arc or linear pattern.

4. The integral polycrystalline diamond composite drill bit according to claim 3, characterized in that, When all cutting units are arranged in an arc, the angle between the axes of two adjacent cutting units is 5°-55°; when all cutting units are arranged in a linear manner, the distance between the axes of two adjacent cutting units is 3mm-25mm; the height of the cutting unit is 1mm-10mm; and the half-width of the cutting unit is 2mm-15mm.

5. The integral polycrystalline diamond composite drill bit according to claim 1, characterized in that, Each cutting unit has a chamfer of 0°-60° on the side edge of the polycrystalline diamond layer.

6. The integral polycrystalline diamond composite drill bit according to claim 1, characterized in that, The thickness of the cemented carbide layer is 0-20 mm; the thickness of the polycrystalline diamond layer is 1 mm-10 mm.

7. The integral polycrystalline diamond composite drill bit according to any one of claims 1 to 6, characterized in that, The number of cutting units is 2-12.

8. The integral polycrystalline diamond composite drill bit according to claim 7, characterized in that, The cutting unit is wedge-shaped, conical, spherical, cylindrical, or a protruding structure formed by two adjacent arc-shaped grooves extending inward from the working surface of the block.

9. A drill bit for oil and gas drilling, characterized in that, The drill bit is provided with the integral polycrystalline diamond composite drill teeth as described in any one of claims 1 to 8.

10. The drill bit used in oil and gas drilling according to claim 9, characterized in that, The drill bit has integrated polycrystalline diamond composite drill teeth arranged in the front row, rear row, or between the front and rear rows of each blade.

11. The drill bit used in oil and gas drilling according to claim 9, characterized in that, The drill bit has several discrete PDC drill teeth arranged in the front row of one or more blades; below the discrete PDC drill teeth are integrated polycrystalline diamond composite drill teeth fixed to the blades; and the grooves on the integrated polycrystalline diamond composite drill teeth are adapted to the contour shape of the discrete PDC drill teeth.

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