MXPA97008373A - Modular barrena arm rotato drill barrena - Google Patents

Abstract

The present invention relates to a drill bit for a modular arm. The modular arm includes an inner surface having the first and second angled surfaces whose lower portions form a wedge projecting inwardly. A curved throat relief area connects to a lower edge of the wedge. The bag in the drill bit is dimensioned to receive the support arm. The bag includes a wedge-shaped recess sized to receive the wedge of the support arm. A triangular weld groove is provided. A triangular weld groove is provided on the convex surface of the auger body. A welding section is applied in the welding groove to firmly secure the support arm to the body of the weld

Description

MODULAR BARRENA ARM ROTATORY DRILL BARRENA TECHNICAL FIELD OF THE INVENTION This region generally refers to rotary drill bits used in the drilling of holes in the ground and in particular to a drill bit having an improved modular arm.

BACKGROUND OF THE INVENTION Various types of rock drill bits or rotary drill bits have been used to form a hole in the ground. Examples of such drill bits include roller cone augers or rotary cone augers frequently used in drilling oil and gas wells. A rotating cone auger comprises a bit body with an upper end adapted for connection to a drill string. A plurality of support arms, typically in a number of three, depend on the lower part of the auger body with each arm having a spindle projecting downwardly from said auger body and radially and inwardly with respect to a projected rotational axis. of the auger body.

For some applications, modular construction techniques have been used to fabricate auger bits of a auger body and modular support arms. Such modular support arms often include a flat locating face extending in a line-sight path or non-deflected relative to the outside of the bit, requiring the length of the welded bead to be perpendicular to a radial line extending from the center of the auger. This section of the welded joint or welded bead perpendicular to a radial line running from the center of the bit is known as the straight section of the welded bead. The profile of the arm approaching the area where the weld was deposited near a bag formed in the body of the drill was commonly straight.

SUMMARY OF THE INVENTION In accordance with the present invention, the various disadvantages and problems associated with rotary and drilling holes have been substantially reduced or eliminated. In one aspect of the present invention, a modular support arm has been provided, which has a top surface, an interior surface, an exterior surface with a skirt formed as a part thereof, and a bottom edge. The inner surface and the skirt surface are contiguous at the bottom edge. The support arm has a first side face and a second face extending from the inner surface. The inner surface of the support arm includes the first and second angle surfaces, the bottom portions of which form a wedge projecting inwardly from the interior surface of the support arm, which forms an upper surface and a lower edge on the lower arm. the cradle. The wedge-shaped projection is located on the inside of the modular arm longitudinally between the stump end of the modular arm and the locating features or openings on the inner surface of the modular arm. Parts of the support arm, such as the inner surface and the inner surface, are dimensioned to allow the securing of a part of the support arm within a pocket formed in the auger body. Depending on the application, multiple recesses and projection wedges can be used.

The inner surface of the support arm includes means for aligning and positioning the support arm within the bag during fabrication of the bit. The bag in the auger body is sized to receive the support arm and typically includes a rear wall, a wedge-shaped recess having a general shape of a wedge with a rounded apex, an inner surface coupled to the rear wall in the lowermost edge, and the inclined and opposite sides extending outward from the rear wall. The inclined sides and the lower surface form the wedge-shaped recess dimensioned to receive the wedge of the support arm projecting inwards.

A spindle is fastened to the inner surface near its bottom edge and angled downwardly and inwardly relative to the support arm. A cutter cone assembly is provided with an opening and a chamber for mounting the cutter cone assembly on the spindle.

An advantage of the present invention is that when the wedge-shaped triangular projection and its matching wedge-shaped recess are welded together, they result in a triangular-shaped welded joint that reduces the stress load across the welded joint. The reduction in the stress load through the welded joint essentially reduces the possibility of cracking in the welded joint. Projection of the wedge-shaped part into the machined bag of the auger also lengthens the count of welds on which the stresses can be distributed and therefore reduces the stress load through the weld joint.

Tensions are transferred from the arm to the body through contact of the upper surface of the projection to the lower surface of the bag. This has the effect of increasing the area over which the stresses are transferred and allowing a smooth transition of the tensions from the arm to the body without the stresses being concentrated in any single area of the arm or body. Additionally, the profile of the arm is gradually mixed into a wedge-shaped projection so that stresses are transferred through the arm without concentration in any single area of the arm.

Additional advantages are achieved by relocating the effective area of the welding heat from the heavily loaded part of the arm to an interior inner stressed part. Therefore, the projection serves to distribute the stresses imposed by the fabrication of the auger so that the efforts are benign to the structural integrity of the welded support arms. Without this projection, cracks can be formed as a result of manufacturing efforts and operationally imposed through welding by holding the arm to the body.

Additionally, the adoption of a generally triangular configuration for the wedge reduces the number of weld segments and the need for the welder to reach around and behind the arm to weld the insulated center segment. The welder is therefore capable of producing a more secure weld with overlaps and minimum cuts. The configuration resulting from the teachings of the present invention is less fatiguing to the welder.

BRIEF DESCRIPTION OF THE DRAWINGS For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings in which: Figure 1 is a schematic drawing in the elevation and in section with cut portions of a rotating cone drill bit incorporating the features of the present invention fastened to one end of a drill string placed in a hole; Figure 2 is an isometric drawing showing a partially exploded view of a rotary cone drill bit incorporating the embodiment of the present invention.

Figure 3 is an exploded sectional drawing showing parts of a one-piece auger body, the support arm, and the cutter cone assembly incorporating one embodiment of the present invention.

Figure 4 is an isometric drawing of the support arm of the present invention.

Figure 5 is a drawing in elevation of the support arm shown in Figure 4.

Figure 6 is a drawing taken along line 6-6 of Figure 5, and Figure 7 is a sectional drawing with parts cut away from a unitary auger body having a support arm attached thereto. according to the embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION Preferred embodiments of the present invention and their advantages are better understood by referring to Figures 1-7 of the drawings, with like numbers being used for equal and corresponding parts in the various drawings.

For purposes of illustration, the present invention is involved in a rotary cone drilling bit 20 of the type used in the drilling of a hole in the ground. The rotary cone drilling bit 20 can sometimes be referred to as a "rotary bit" or "rock bit". The rotating cone drilling bit 20 preferably includes a bolt or threaded connection 44 for use in gripping the drill bit 20 with a drill string 22. The threaded connection 44 and the corresponding threaded connection (not shown) associated with the Drill rope 22 is designed to allow rotation of drill bit 20 in response to rotation of drill string 22 on the surface of the well.

In Figure 1, the drill bit 20 is shown attached to a drill string 22 and placed in the hole 24. The ring 26 is formed between the outside of the drill string 22 and the interior or wall 28 of the drill 24 In addition to rotary drilling bit 20, drill string 22 is frequently used to provide a conduit for communicating drilling fluids and other fluids from the well surface to drill bit 20 at the bottom of bore 24. Such drilling fluids may be directed to flow from the drill string 22 to several nozzles 60 provided in the drill bit 20. The cuts formed by the drill bit 20 and any other debris at the bottom of the drill 24 will be mixed with the drilling fluids that exit the nozzles 60 and will return to the surface through the ring 26.

For the rotary cone drilling bit 20, the cutting action or drilling action occurs when the cutter cone assemblies 100 are rolled around the bottom of the hole 24 by rotating the drill string 22. The resulting inside diameter of the perforation 24 defined by the wall 28 corresponds approximately to the measuring diameter or the combined outer diameter of the cutter cone assemblies 100. The cutter cone assemblies 100 cooperate to cut the diameter of the perforation 24 defined by the wall 28 is response to rotating drill bit 20. Cutter cone assemblies 100 can sometimes be referred to as "Rotary Cone Cutters" or "Roller Cone Cutters".

As shown in Figures 1, 2 and 3, each cutter cone assembly 100 includes protruding inserts 104 which scrape and empty against the sides and bottom of the perforation 24 in response to the weight and rotation applied to the drill hole 20 from the drill string 22. The position of the inserts 104 for each cone assembly Cutter 100 may be varied to provide the cutting action downward of the desired hole. Other types of cutter cone assemblies can be used satisfactorily with the present invention, including but not limited to the cutter cone assemblies having the teeth pressed in place of the inserts 104.

The drill bit 20 preferably comprises a unitary or one-piece auger body 40 with the upper part 42 having the bolt or the threaded connection 44 adapted thereto for securing the drill bit 20 to the lower end of a drill string 22. Three arms of Ü2 support 70 are preferably secured to the auger body 40 and extend longitudinally therefrom, opposite from the bolt 44. Each support arm 70 preferably includes a spindle 82 connected and extending from the inner surface 76 of the respective support arm. 70 The auger body 40 includes the lower part 46 having a generally convex outer surface 48 formed thereon. The dimensions of the convex surface 48 and the location of the cutter cone assemblies 100 are selected to optimize fluid flow between the lower portion 46 of the auger body 40 and the cutter cone assemblies 100. The location of the cone assemblies The cutter 100 in relation to the lower part 46 can be varied by adjusting the length of the associated support arm 70 and the spacing of each support arm 70 on the outside of the auger body 40.

The auger body 40 has a number of pockets 54 formed on the outside thereof and spaced radially from one another. The number of bags 54 is selected to correspond to the number of support arms 70 that are to be fastened thereto. The spacing of the pockets 54 relative to each other on the outside of the auger body 40 is selected to correspond to the desired spacing of the support arms 70 and the associated cutter cone assemblies 100.

As shown in Figure 2, each of the bags includes a rear wall 64 and two inclined side walls 66 and 68 angled outwardly from the back wall 64. The rear wall 65 begins at the upper surface 65 of the bag 54 and extends longitudinally through a portion of the bag 54. The dimensions of the back wall 64, and of the side walls 66 and 68 are selected to be compatible with the adjacent inner surface 66, the sides 132 and 134, and the upper surface 74 of the associated support arm 70. The first and second posts 53 and 54 are positioned on the rear wall 64 and are sized to receive the first and second openings 75 and 77 of an associated support arm 70.

Near the bottom of the bag 54, a wedge-shaped recess 121 is formed by the bottom surface 67 of the bag 54 and the side walls 66 and 68. The bottom surface 67 of the bag 54 is generally triangular in shape. . The connection of one side of the triangularly shaped bottom surface 67 and the back wall 64 preferably form a radiated or rounded edge 69.

Similarly, as shown in figure 7, the connection of the lower surface 67 and the side walls 66 and 68 form a corner or a rounded corner 73. The combination of the bottom surface 67 and the side walls 66 and 68, forming together the wedge-shaped recess 121 is sized to receive the wedge-shaped projection 125, shown in Figure 4, of the support arm 70. The wedge 125 is designed as a wedge projecting inwardly because it is projected inwardly relative to the longitudinal axis 50 of the auger body 40. Additional inwardly projecting wedges and matching recesses may be used with the present invention.

The welding groove 126 is formed on a convex surface 48 of the auger body 40 and runs along the lowermost edge 71 of each bag 54. When the support arm 70 is placed in its associated bag 54, a welding section 128 , as shown in Figure 7, is applied in a weld slot 126 to securely secure each support arm 70 to the auger body 40.

Figure 3 is an exploded drawing showing the relationship between the auger body 40, and one of the support arms 70 and its associated cutter cone assembly 100. The auger body 40 includes a middle portion 52 positioned between the part upper 42 and the lower part 46. The longitudinal axis or central hub 50 extends through the auger body 40 and generally corresponds to the axis of rotation projected for the drill bit 20. The middle portion 52 preferably has a generally cylindrical with the bags 54 formed on the outside thereof and spaced radially from one another. The number of bags 54 is selected to correspond to the number of support arms 70 that will be fastened thereto. The spacing of the pockets 54 relative to each other on the outside of the middle part 52, is selected to correspond to the desired spacing of the support arms 70 and their associated cutter cone assemblies 100 with respect to the longitudinal axis 50 and the projected axis of rotation for the rotary auger 20.

Each support arm 70 has a longitudinal axis 72 that extends through it. The support arms 70 are preferably mounted in their respective pockets 54 with their respective longitudinal axis 72 aligned essentially parallel to one another and with the longitudinal axis 50 of the associated auger body 40.

Each support arm 70 is preferably welded into its associated bag by a series of welds, not all of which are shown. The weld groove 126 is formed on a convex surface 48 and runs along the lowermost edge of the bag 71 of the bag 74. The weld 120 is placed in the weld groove 126 to help secure each support arm 70 to the auger body 40. The weld groove 126 and the weld 128 are of a triangular configuration, corresponding approximately to the lower perimeter of the wedge 125. Due to the triangular configuration of the weld groove 126, the weld 128 does not include any section that is perpendicular to a radial line extending from the longitudinal axis 50 of the drill bit 20. The absence of such a weld section reduces the tension stresses of the support arm holder 70 to the bit body 40 in its slot of associated welding 126.

Each cutter cone assembly 100 is preferably constructed and mounted on its associated spindle 82 in an essentially identical manner. Each support arm 70 is preferably constructed and mounted in its associated bag 54 in a substantially the same manner. Therefore, only one support arm 70 and the cutter cone assembly 100 will be described in detail since the same description is generally applied to the other two support arms 70 and their associated cutter cone assemblies 100.

The support arm 70 has a generally rectangular configuration with respect to the longitudinal axis 72. The support arm 70 can have several cross sections taken normal to the longitudinal axis 72, depending on the configuration of the associated bag 54 and other characteristics which can incorporated within the support arm 70 according to the teachings of the present invention. The support arm 70 includes an upper surface 74, the inner surface 76, the bottom edge 78 and the outer surface 80. The support arm 70 also includes the sides 84 and 86 which extend preferably parallel to each other and to the longitudinal axis 72. The dimensions and configuration of each support arm 70 are selected to be compatible with the associated bag 54 as shown in Figures 2 and 3 as the part of each support arm 70 including the top surface 74 and the adjacent parts of the inner surface 76 are dimensioned to fit within the associated bag 54.

The inner surface 76 includes the central portion 142 with the angled surfaces 144 and 146 formed on one side thereof. The configuration of the inner surface 76 can be varied essentially between the upper surface 74 and the bottom edge 78. The inner surface 76 and the outer surface 80 are contiguous with the bottom edge 78 of the support arm 70. The part of the outer surface 80 formed on one side of the bottom 78 is often referred to as a skirt surface 88.

The spindle 82 is preferably angled downwardly and inwardly with respect to both the longitudinal axis 72 of the support arm 70 and the axis of rotation projected from the drill bit 20. This orientation of the spindle 82 results in the exterior of the assembly of cutting cone 100 engaging the side and bottom of the drilling hole 24 during drilling operations. For some applications it may be preferable to place each support arm 70 and its associated spindle 82 with the cutter cone assembly 100 in an offset of the projected axis of rotation of the drill bit 20. The desired offset can easily be obtained by forming the associated pockets 54 inside the auger body 40 with a corresponding offset from the longitudinal axis 50 of the auger body 40. The amount of offset can vary from zero to five or six degrees or zero inches to one and a half inches in the direction of rotation of the drill bit 20.

As shown in Figure 3, each cutter cone assembly 100 preferably includes a base portion 108 with a conically shaped nose or shell 106 extending therefrom. For some applications, the base portion 108 includes a just conically shaped outer surface 110 which is preferably angled in an opposite direction from the angle of the shell 106. The base 108 also includes a rear face 112 which may be placed at a side of the parts of the inner surface 76 of the associated support arm 70. The base part 108 preferably includes the opening 120 12 with the chamber 114 extending therefrom. The chamber 114 preferably extends through the base 108 and up to the nose 106. The dimensions of the opening 120 in the chamber 114 are selected to allow assembly of each cutter cone assembly 100 on its associated spindle 82. One or more Bearing assemblies 122 are preferably mounted on the spindle 82 and placed between a bearing wall (not shown) within a chamber 114 and the annular bearing surface 81 on the spindle 82.

The cutter cone assembly 100 can be retained on its associated spindle 82 by inserting a plurality of ball bearings 124 through the ball conduit 26 extending from the outer surface 80 of the support arm 70 through the spindle 82. A bushing of matching ball (not shown) will typically be provided on the inside of the cutter cone assembly 100. Once inserted, the ball bearings 124 in cooperation with the ball bushing 98 and the matching ball bushing (not shown) on the set Cutter cone 100 will prevent disengagement of cutter cone assembly 100 from spindle 82. Ball duct 96 may be subsequently capped by welding or any other known techniques. For some applications, a ball plug (not shown) may also be placed in conduit 96.

As shown in Figure 3, a portion of the upper surface 74, of the outer surface 80, and of the adjacent sides 84 and 86 have been removed from the upper part of the support arm 70 to provide the cavity 90 for installing a lubricant reservoir (not shown) there.

For one embodiment of the present invention as shown in Figures 4 and 5, the first opening 75 and the second opening 77 are formed on the inner surface 76 of each support arm 70. The first post 53 and the second post 55 are preferably located on the back wall 64 of each bag 54. Posts 53 and 55 extend radially from each rear wall 64 to receive, respectively, the first opening 75 and the second opening 77 so as to place each support arm 70 within its associated bag 54. For one embodiment of the present invention, the first opening 75 preferably comprises a longitudinal groove extending from the upper surface 74 and sized to receive the first post 53 there. The second opening 77 preferably has a generally circular configuration sized to receive the second post 55 there. The first opening 75 is preferably formed as a longitudinal groove to compensate for any variation between the dimensions of the support arm 70 and its associated pocket 54 including the relative position of the first opening 75; of the second opening 77, and of the first post 53 and the second post 55 respectively.

As shown in Figure 4, the inner surface 76 of the support arm 70 preferably includes a central portion 142 with the angled surfaces 144 and 146 extending longitudinally and parallel to each other from the upper surface 74 to the relief area of the upper surface 74. throat 87 formed on the lower part of the inner surface 76.

The inwardly projecting wedge 125 has the first and second inclined sides 132 and 134 extending from the angled surfaces 144 and 146 of the inner surface 76. The encounter of the inclined sides 132 and 134 forms a rounded apex 151 of the wedge 125. An upper surface 136 extends from the central part 142 to the sides 132 and 134, forming an upper edge 138 of the wedge 125. The upper surface 136 is essentially perpendicular to the central part 142. As shown in Figure 5, the upper edge 138 can be chamfered. Alternatively, the upper edge 136 may be rounded or radiated.

Because the central part 142 and the upper surface 136 are positioned against the back wall 64 and the bottom surface 67, respectively, when the support arm 70 is placed in the bag 54, the upper surface 136 and the part central 142 are machined to provide the locator surfaces for each support arm assembly 70 in the pouch 54. The wedge 125 is dimensioned to fit within the wedge-shaped recess 121 of the pouch 54.

The throat relief area 87 of the support arm 70 gradually arcs upwardly from the spindle 82 and the edges 150 to its connection with the lower edge 152 of the wedge 125. The throat relief area 87 and the wedge 125 are contiguous at the lower edge 152. The lower edge 152 is arcuate upwardly triangular, in shape, and includes an outermost part 130. The support arm 70 is placed in the bag 54 so that the outermost point 130 is adjacent to the lowermost edge 71 of the bag 54. Once the support arm 70 is placed in a respective bag 54 the weld 128 is placed in a weld slot 126 to firmly anchor the support arm 70 to the auger body 40.

Figure 6 shows the lower part of the support arm 70 seen along the line 6-6 of Figure 5. The spindle 82 includes the axle 83 extending from the inner surface 76 of the support arm 70. A flat machined surface and generally circular 85 is preferably formed on one side of the joint between the inner surface 76 of the support arm 70 and the spindle 82. The machined area 85 can sometimes be referred to as the "Ultimated Machined Surface or LMS" of the support arm 70. The machined surface 85 preferably has a generally circular configuration defined by the radius Rx as shown in Figure 6 extending from the axis 83 of the spindle 82 which results in the machined surface 85 extending uniformly through three hundred sixty degrees around the axis 83 of the spindle 82. The machined surface 85 and its associated radius R cooperate with the outer surface 80 to partially define the skirt surface 88 and the bottom edge 78 of the support arm 70. The dotted line 112 shown in FIG. 8 corresponds to the outside diameter of the rear face 112.

Extending from the spindle 82 and flanges 150 to the lower edge 152 of Figure 6 is the throat relief area 87. The first and second angle surfaces 144 and 146 extend from the first and second sides 132 and 134, respectively, of the wedge 125. The first and second sides 132 and 134 lie between the upper edge 138 and the lower edge 152 of the wedge 125. The second opening 77 is formed on the central part 142.

Figure 7 shows the placement of the support arm 70 in the bag 74 of the auger body 40. The wedge 125 is positioned within the wedge recess 121. A weld 128 within the weld slot 126 secures the support arm 70 to the bag 54 of the auger assembly 40.

As shown in Figure 1, once the support arm 70 is placed in the bag 54 so that the outermost point 130 is more adjacent to the lowermost edge 71 of the bag 54, a section of the weld 128 is placed in the weld slot 126 to securely secure the support arm 70 to the auger body 40. The weld 128 is triangular in shape and lacks any length that is perpendicular to a straight line occurring from the longitudinal axis 50 of the body of the weld. auger 40. The absence of such a welding section 128 avoids the application of purely tensile stresses in the area of the weld 128. The gradual curvature of the throat relief area 87 provides a means through which the stresses of the boom The support is uniformly transferred to the auger body 40, without concentration in any single location on the support arm 70 or on the auger body 40. The efforts of the support arm 70 are transferred to the auger body through the longitudinal contact of the wedge 125 with the lower surface 67 of the bag 54. The transfer of the stresses through the wedge 125 further reduces the stresses on the weld 128 which has the effect of reducing possibility of cracking of welding 128.

Although the present invention has been described in greater detail, it should be understood that several changes, substitutions or alterations may be made here without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (20)

1. A support arm and a cutter cone assembly for a drill bit having a bit body comprising: said support arm having a top surface, an interior surface, an exterior surface with a skirt surface formed as a part thereof, and a bottom edge, with said interior surface and said skirt surface abutting the bottom edge; said inner surface of said support arm comprises: the first and second angle surfaces, the lower portions of said angled surfaces form a wedge projection from the inner surface, said wedge having a lower edge and an upper edge; a central part including a flat surface extending between the first and second angle surfaces; and a triangular surface extending perpendicularly from said central part to the upper edge of said wedge; a throat relief area connected to said lower edge of said wedge; the dimensions of said upper surface and said inner surface are selected to allow the securing of a part of said support arm within a pocket formed in said auger body, and the dimensions of said wedge selected to allow the securing of said wedge within the wedge-shaped recess formed in said bag in said auger body; a spindle attached to said inner surface near the bottom edge and angled downwardly and inwardly relative to said support arm; Y means provided on said inner surface of said support arm for alignment and positioning of the support arm within said bag during manufacture of the drill bit.

2. The cutter cone and support arm assembly as claimed in clause 1, characterized in that said means for alignment comprises a post corresponding to an opening.

3. The cutter cone and support arm assembly as claimed in clause 1, characterized in that said means for alignment comprise the first and second posts corresponding to the first and second openings, wherein said first opening is a slot longitudinal

4. The cutter cone and support arm assembly as claimed in clause 1, characterized in that said inner surface comprises said wedge.

5. The support and cutter cone assembly as claimed in clause 1, characterized in that the throat relief area arches upwards from the spindle to the wedge.

6. The support arm and cutter cone assembly as claimed in clause 1, characterized in that said central part is smoothly integrated into the upper edge of said wedge.

7. The support arm and cutter cone assembly as claimed in clause 1, characterized in that said upper edge of said wedge is chamfered.

8. A method for manufacturing a modular support arm for a drill bit having a bit body, comprising the steps of: forming a support arm having a top surface; forming an interior surface on the support arm; forming a central part including a flat surface with the first and second angle surfaces on the opposite sides of said flat surface. forming a wedge-shaped projection on said inner surface connected between the first and second angle surfaces so that the dimensions of said wedge-shaped projection are dimensioned to allow securing said wedge-shaped projection within a recess in wedge-shaped in a bag formed in said auger body; forming an upper surface on said wedge-shaped projection extending from the central part so that the dimensions of the upper surface and said inner surface of said support arm are dimensioned to allow the securing of a part of said support arm within of said bag formed in said auger body; forming a throat relief area extending from said wedge-shaped projection; forming means on said inner surface for alignment and positioning within the support arm within said bag of the auger body.

9. The method for manufacturing a modular support arm as claimed in clause 8, characterized in that said step for forming an upper surface includes the steps of: forming said upper surface generally perpendicular to said central part; Y joining said upper surface on said wedge-shaped projection on an upper edge.

10. The method for manufacturing a modular support arm as claimed in clause 9, characterized in that it comprises the step of forming a rounded corner on said upper edge.

11. The method for manufacturing a modular support arm as claimed in clause 9, characterized in that it comprises the step of machining said upper surface.

12. The method for manufacturing a modular support arm as claimed in clause 8, characterized in that it comprises the step of forming a curved lower edge upwards in the connection of said throat relief area and said wedge.

13. A rotating cone drilling bit to form a bore comprising: a bit body having a number of bags formed on the outside of said bit body; a number of support arms extending down from and mounted on said auger body, said number of support arms is equal in number to the number of pockets formed in said auger body, each of the support arms has a upper surface, an inner surface, and a spindle connected to said inner surface, each spindle is generally projected downward and inward with respect to its associated support arm; a number of cutter cone assemblies equaling said number of support arms and mounted respectively on one of said spindles; each of the interior surfaces of each of the support arms comprises: the first and second angle surfaces, the lower part of said first and second angle surfaces form a wedge projecting inwardly having an upper and a lower edge; a central part between said surfaces at first and second angle; an upper surface extending perpendicularly from said central part to said upper edge of said wedge; Y an arched throat relief area extending from the lower edge of said wedge; each of said wedge; each of said bags comprises a rear wall, an inner surface connected to said rear wall in a rounded edge, the inclined and opposite sides extending outwardly from said rear wall, and a wedge-shaped recess formed by the combination of the sides inclined and said lower surface; the dimensions of said upper surface and said inner surface of each of the support arms are selected to allow the securing of a part of the support arm within one of the respective bags, and the dimensions of each of said wedges is selected to allow securing of the wedge within the recess of one of the respective bags; Y means provided on said inner surface of each of the support arms and on each of the rear walls of said bags for the alignment and positioning of said support arm within said bags during the manufacture of the drill bit.

14. The rotary cone drilling bit as claimed in clause 3, characterized in that each of said bags includes a lowermost edge formed in the connection of said bag and said auger body; wherein said auger body includes a slot extending in a triangular pattern along each of the lowermost edges of said bags; a welding section in each of the welding grooves to secure each of the support arms to said auger body.

15. The rotary cone drilling bit as claimed in clause 14, characterized in that each of the lower edges of said wedges is arched upward and includes an outermost point placed on one side of one of the lowermost edges of the rotary cone. said bags.

16. The rotary cone drilling bit as claimed in clause 13, characterized in that each of the upper edges of said wedges forms a rounded edge.

17. The rotary cone drill bit as claimed in clause 13, characterized in that the connection of each of said bottom surfaces and each of the inclined sides forms a rounded corner.

18. The rotary cone drill bit as claimed in clause 13, characterized in that each of said top surfaces of each of the support arms is a machined surface and each of the bottom surfaces of each of the bags is a machined surface.

19. The rotary cone drilling bit as claimed in clause 13, characterized in that each of said bags includes a lower edge at the connection of each of the bags and said auger body; wherein each of the lower edges of each of said wedges includes an outermost tip positioned at a lowermost edge of each of the bags; wherein said auger body includes a weld groove and the weld extending in a triangular pattern around each of the lowermost edges to secure each of said support arms to said auger body.

20. The rotary cone drilling bit as claimed in clause 13, characterized in that said means for alignment and positioning comprise the first and second openings formed on each of the supporting arms, and the first and second posts placed on the back wall of each of the bags.