Separable anchoring drill bit and method for hydraulic cooperative mechanical drilling

Abstract

The invention relates to a separable anchoring drill bit and method for hydraulic and mechanical drilling, the separable anchoring drill bit for hydraulic and mechanical drilling comprises a drill body, a separation core, a separation drill bit body and a separation ball, the interior of the drill body is hollow and used for being installed at the front end of a hollow drill rod, and the separation core is located in the drill body; the outer side of the separation core is in sealing fit with the interior of the drill body, a central hole is formed in the middle, a threaded hole is formed in the outer side of the separation core, the drill body is provided with a through hole corresponding to the threaded hole, and a fastening screw penetrates through the through hole to be connected with the threaded hole to fix the separation core in the drill body; the separation ball is located in the drill body, the outer diameter of the separation ball is larger than the center hole diameter of the separation core, and the separation ball is used for blocking the rear-end opening of the center hole. According to the construction method, a drill rod push rod and an open hole anchoring agent anchor cable anchor rod propelling process can be omitted, disturbance to a drill hole is reduced, and the technical problems that in the current anchor cable construction process, procedures are complex, disturbance is generated to the drill hole many times, the procedure time is long, and the construction efficiency is low are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of tunnel construction support, more particularly, it relates to a separable anchor drill bit and method of water-assisted mechanical drilling. BACKGROUND

[0002] Tunnel engineering construction and underground coal mining are the main force of large-scale underground engineering construction in China, and the total length of new tunneling is more than 12000 km per year. The main support method of tunnels in China is anchor rod and anchor cable support. Many researchers have conducted more research on the performance of anchor rod support. With the development of science and technology, automatic and intelligent anchor rod drilling machines are increasingly valued. The performance of anchor rod drilling directly affects the anchor rod support speed and support quality, and is the key process of anchor rod support construction engineering. The on-board hydraulic anchor rod drilling machine is widely used in the field of tunnel / roadway and rock anchoring construction due to its strong adaptability, wide adjustment range and flexible operation. Since the installation of anchor rod construction links such as anchor agent cannot be automated, the construction of the hydraulic anchor rod drilling machine mainly relies on manual operation, and the anchor rod construction time is long and the technical dependence on the operator is large. The existing hydraulic anchor rod drilling machine construction process mainly includes: installing the drill rod, drilling, disassembling the drill rod, installing the anchor agent, installing the anchor rod, mixing the anchor agent, and tightening the threaded rod. The construction process is more, resulting in a long anchor rod construction time.

[0003] The existing automatic construction technology of hydraulic anchor rod drilling machine mainly has two development directions. One is to upgrade and transform the traditional anchor rod construction process, and some experts set up pneumatic anchor rod clamps and drill rod clamps on the anchor rod drilling machine to realize the automatic replacement of anchor rods and drill rods. Some experts design specific automatic anchor rod conveying and automatic anchoring devices to realize automatic anchor rod construction. The automatic replacement of anchor rods and drill rods based on the transformation of the traditional anchor rod construction process has large overall size of the anchor rod drilling machine, and the structure of the motion implementation mechanism is complex, and the reliability is low. The other research direction of automatic construction of hydraulic anchor rod drilling machine is to develop integrated anchor rod drilling and supporting construction process. Some experts propose to make a one-time sheet-shaped drill bit embedded at the front end of a hollow grouting anchor rod to form an integrated anchor rod drilling and supporting anchor rod. When the anchor rod drilling machine rotates counterclockwise, the anchor rod drills, and when the anchor rod drilling machine operates clockwise, the rotating rod nut realizes pre-tightening. Through the control of the electro-hydraulic valve, the automatic discharge of the grouting agent can be realized.

[0004] The integrated anchor rod drills a hole, anchors, and pre-tightens by using a set of drilling box mechanism, thereby avoiding repeated switching of construction equipment and drill rods, saving time for disassembling the drill rod, and improving construction efficiency. SUMMARY

[0005] In view of the deficiencies in the prior art, the present application aims to provide a separable anchor drill bit for hydraulic and mechanical drilling, which can solve the technical problems of complex process, repeated disturbance to the drill hole, long process time, and low construction efficiency in the current anchor cable construction process. The present application also aims to provide a separable anchor method for hydraulic and mechanical drilling, which can solve the technical problems of complex process, repeated disturbance to the drill hole, long process time, and low construction efficiency in the current anchor cable construction process.

[0006] The present application provides the following technical solutions: A separable anchor drill bit for hydraulic and mechanical drilling includes a drill body, a separation core, a separation drill bit body, and a separation ball. The drill body is hollow inside and is used to install at the front end of a hollow drill rod. The separation core is located inside the drill body. The outer side of the separation core is in sealing cooperation with the inside of the drill body, and a central hole is arranged in the middle. Threaded holes are arranged on the outer side of the separation core, and corresponding threaded holes are arranged in the drill body. Fastening screws are used to connect the threaded holes and the threaded holes, and the separation core is fixed inside the drill body. The separation ball is located inside the drill body, and the outer diameter is greater than the hole diameter of the central hole of the separation core. The separation ball is used to block the opening at the rear end of the central hole during use. The separation drill bit body is installed at the front end of the drill body and includes a connecting part and a drill bit body. The connecting part is made of elastic material. The rear end of the connecting part extends into the inside of the drill body, is connected with the clamping groove of the drill body, and maintains interference fit. The front end of the connecting part is connected with the drill bit body. A nozzle is arranged in the middle of the drill bit body, and a cutting edge is arranged on the outer side. A connecting channel is arranged in the middle of the connecting part to connect the nozzle and the inside of the drill body.

[0007] Beneficial effects: The present invention provides a separable hydraulically coordinated mechanical drilling anchoring drill bit. Through the separation core and the separation drill bit body connected to the drill body respectively, it ensures the normal drilling and rock cutting functions of the drill bit when the drill rod rotates. On the other hand, it pressurizes the inside of the drill body through high-energy fluid and separation ball. When the pressure reaches a certain limit value, the separation core and the separation drill bit body are dislodged, opening the drill bit. The anchoring agent and anchor cable / anchor rod can directly pass through the drill bit to the front end of the borehole without removing the drill rod. This eliminates the need for drill rod push rod and bare hole anchoring agent, anchor cable and anchor rod advancement process, effectively reducing the number of steps in the anchoring construction process. The anchoring agent and anchor cable / anchor rod can enter the front end of the drill bit without the need to remove the rod, reducing disturbance to the borehole. It can significantly reduce the number of anchoring steps, save process time, and significantly improve construction efficiency. This invention features an ingenious structure. By incorporating a separation ball, a separation core, and a separation drill bit body, it enables long-distance delivery of the separation ball and sealing of the central hole of the separation core. High-pressure fluid is applied to the separation core and fastening screws to achieve precise and controllable separation of the separation core. The separation process is stable and effective, unaffected by the drill rod's orientation, angle, or drilling depth. The separation drill bit body is mainly composed of a connecting part and a drill bit body at the front end. This structural design allows the separation drill bit body to withstand pressure from the soil in front during drilling and cutting, while being able to detach from the high-pressure fluid load inside. The separation core and the separation drill bit body are separately configured and detached sequentially, facilitating the processing and assembly of the overall structure.

[0008] Furthermore, a tapered section with a gradually increasing diameter from the inside to the outside is provided at the rear end opening of the central hole.

[0009] Beneficial effects: The conical section guides the separation ball, which helps ensure that the separation ball abuts against the conical section under the action of high-pressure fluid and reliably seals the central hole.

[0010] Furthermore, a first sealing ring is provided on the outside of the separation core, and the first sealing ring maintains a sealed fit with the inside of the drill body. Two first sealing rings are provided and are respectively distributed on both sides of the threaded hole.

[0011] Beneficial effects: By placing the first sealing ring on both sides of the fastening bolt connection, leakage at the threaded hole is prevented, and the deformation of the first sealing ring is adjusted by adjusting the fastening bolt, ensuring good sealing between the separation core and the drill body and preventing pressure leakage.

[0012] Furthermore, a core groove is provided at the axial midpoint of the outer side of the separation core.

[0013] Beneficial effects: Setting a groove in the core body can reduce the difficulty of inserting the separation core and the drill body, and to a certain extent reduce the fit tolerance requirements between the surface of the separation core and the inside of the drill body, thereby reducing the machining accuracy requirements and saving machining costs.

[0014] Furthermore, the portion of the connecting part that extends into the drill body has a connecting groove at the axial middle position, and the drill body has an annular protrusion structure that corresponds to the shape of the connecting groove. The two sides of the connecting groove and the rear end face of the connecting part are all tapered transition surfaces.

[0015] Beneficial effects: It facilitates the insertion of the connector into the drill body while ensuring a stable connection between the connector and the drill body.

[0016] Furthermore, a second sealing ring is provided on the outer side of the connecting part, and the connecting part is threadedly connected to the drill body through the second sealing ring.

[0017] Beneficial effects: The outer side of the connecting part is sealed with the drill body through the second sealing ring, ensuring that the internal pressurization process of the drill body is carried out, so that the separation core and the separation drill bit body can be smoothly separated from the drill body; the connecting part is threadedly connected to the drill bit body, which ensures the connection strength while facilitating the assembly of the two.

[0018] Furthermore, a spiral core is provided inside the connecting channel to generate a rotating jet under the action of fluid.

[0019] Beneficial effects: The spiral core transforms high-energy fluid into a rotating jet, converting vertical impact damage into rotating three-dimensional jet flushing-shearing damage, and using hydraulically assisted rotating cutting blades to break rocks and drill holes, greatly improving rock-breaking ability.

[0020] The present invention also provides the following technical solutions: An anchoring method for a separable hydraulic-assisted mechanical drilling system, implemented based on an abrasive waterjet grooving-assisted roller cutter rock-breaking device of the present invention, includes the following steps: S1. After the drill bit has drilled to the specified depth of the anchor rod or anchor cable, continue drilling to a certain depth; S2. Place the separation ball inside the hollow drill pipe, and the separation ball will enter the drill body with the high-energy fluid; S3. The separation ball is stuck at the rear end opening of the central hole, hindering the forward flow of high-energy fluid; S4. The pressure of the high-energy fluid inside the drill bit gradually increases, and the fastening screw breaks after exceeding the upper limit of the shear resistance of the fastening screw. S5. The separation ball and the separation core move forward to impact the separation drill bit body. After exceeding the upper limit of the shear resistance of the connecting slot, the separation drill bit body, the separation ball and the separation core are separated from the drill body. S6. The lower end of the drill body is open, and anchoring agent, anchor rod or anchor cable is inserted through the drill pipe to allow the anchoring agent, anchor rod or anchor cable to enter the front end of the drill bit.

[0021] Beneficial effects: A separable hydraulic-assisted mechanical drilling anchoring method, through a separation core and a separation drill bit body connected separately to the drill body, ensures the normal drilling and rock cutting functions of the drill bit when the drill rod rotates. On the other hand, high-energy fluid and separation balls pressurize the inside of the drill body. When the pressure reaches a certain limit, the separation core and the separation drill bit body detach, opening the drill bit. The anchoring agent and anchor cable / anchor rod can directly pass through the drill bit to the front end of the borehole without removing the drill rod. This eliminates the need for drill rod push rod and the process of advancing the anchoring agent, anchor cable, and anchor rod in the bare hole, effectively reducing the number of steps in the anchoring construction process. The anchoring agent and anchor cable / anchor rod can enter the front end of the drill bit without the need to remove the rod, reducing disturbance to the borehole. This significantly reduces the number of anchoring steps, saves time, and significantly improves construction efficiency. Attached Figure Description

[0022] Fig. 1 This is a schematic diagram of a specific embodiment 1 of the anchoring drill bit for detachable hydraulic-assisted mechanical drilling according to the present invention; Fig. 2 This is a schematic diagram of the structure of a specific embodiment 1 of the anchoring drill bit for separable hydraulic co-operated mechanical drilling of the present invention, in which the separation core is separated from the drill body under the action of the separation ball; Fig. 3 This is a schematic diagram of a specific embodiment 1 of the present invention of a separable hydraulic co-operated mechanical drilling anchoring drill bit in the state where the separable drill bit body and the separable core are separated from the drill body. Reference numerals: 1-Drill body; 2-Separation ball; 3-Separation core; 31-Center hole; 32-Conical section; 33-First sealing ring; 34-Fasting screw; 35-Core groove; 36-Threaded hole; 4-Separation drill bit body; 41-Connecting part; 411-Second sealing ring; 412-Helical core; 413-Connecting groove; 414-Conical transition surface; 42-Drill bit body; 421-Nozzle; 422-Cutting edge. Detailed Implementation

[0023] The present invention will now be described in detail with reference to the accompanying drawings.

[0024] Specific embodiment 1 of the detachable hydraulic-assisted mechanical drilling anchoring drill bit of the present invention: like Figs. 1-3 As shown, the detachable hydraulic-assisted mechanical drilling anchoring drill bit of the present invention mainly consists of a drill body 1, a separation ball 2, a separation core 3, and a separation drill bit body 4. The drill body is hollow inside and is installed at the front end of the hollow drill rod during use. Figs. 1-3The directions shown are for reference only; the area below the diagram is front, and the area above the area below the diagram is rear. The separation core 3 is located inside the drill body 1. A central hole 31 is provided in the center of the separation core 3. The outer side of the separation core 3 is sealed to the drill body 1 via a first sealing ring 33. A core groove 35 is provided at the axial center position on the outer side of the separation core. The core groove 35 is designed to reduce the assembly difficulty of the separation core 3 and the drill body 1, reduce the tolerance requirements for the fit between the separation core surface and the drill body interior, and reduce the machining difficulty of both. A threaded hole 36 is provided on the outer side of the separation core 3, and a corresponding through hole is provided on the drill body. A fastening screw 34 passes through the through hole, connects to the threaded hole 36, and fixes the separation core 3 inside the drill body 1. The separation ball 2 is located inside the drill body, with an outer diameter larger than the diameter of the central hole 31 of the separation core. It is used to seal the rear opening of the central hole 31. To guide the separation ball 2 to stably seal the rear opening of the central hole 31, a tapered section 32 with a gradually increasing diameter from the inside to the outside is provided at the rear opening of the central hole 31.

[0025] Two first sealing rings 33 are provided on the outer side of the separation core 3, respectively distributed on both sides of the threaded hole 36. The threaded hole 36 is located at the rear end of the separation core 3, ensuring that when the separation ball 2 is at the rear end of the central hole 31, the internal pressure of the drill body is quickly transmitted to the fastening screw 34, achieving precise and controllable fracture of the fastening screw 34. The first sealing rings 33 are provided on both sides of the threaded hole 36 to ensure that there is no pressure leakage at the threaded hole. The deformation of the first sealing rings 33 can also be adjusted by adjusting the fastening bolts to ensure good sealing between the separation core and the drill body and avoid pressure leakage.

[0026] The split drill bit body 4 is installed at the front end of the drill body 1. The split drill bit body 4 includes a connecting part 41 and a drill bit body 42. The connecting part 41 is made of elastic material, and its rear end extends into the drill body 1, connecting with the drill body's groove and maintaining an interference fit. Specifically, the portion of the connecting part 41 extending into the drill body has a connecting groove 413 at its axial center position. The drill body 1 has an annular protrusion structure corresponding to the shape of the connecting groove 413. Both sides of the connecting groove and the rear end face of the connecting part are tapered transition surfaces 414, facilitating the insertion of the connecting part 41 into the drill body 1 and maintaining the connection under the action of the groove. Two second sealing rings 411 are provided on the outer side of the connecting part 41, sealing the drill body through the second sealing rings 411.

[0027] The front end of the connecting part 41 is threadedly connected to the drill bit body 42, which facilitates installation and ensures a stable connection. A nozzle 421 is located in the middle of the drill bit body, and a cutting edge 422 is located on the outer side. A connecting channel is provided in the middle of the connecting part 41 to connect the nozzle and the interior of the drill body. In this embodiment, a spiral core 412 is provided inside the connecting channel of the connecting part 41 to generate a rotating jet under the action of fluid. The spiral core 412 converts the high-pressure jet ejected from the nozzle into a rotating jet, thereby transforming the vertical impact damage to the rock mass or soil layer into a rotating three-dimensional jet flushing-shearing damage. Combined with the mechanically rotating cutting edge when the drill rod rotates, this greatly improves the drill bit's rock-breaking ability and drilling efficiency.

[0028] In use, this invention involves installing a drill body equipped with a separation core and a separation drill bit body at the front end of a hollow drill rod. High-energy fluid is injected into the hollow drill rod, and under the action of the spiral core, a rotating jet is ejected from the nozzle, using hydraulic force to assist the rotating cutting edge in efficient drilling. After drilling is completed, a separation ball is placed inside the hollow drill rod. The separation ball enters the drill body with the high-energy fluid and becomes stuck at the rear end of the central hole. The pressure inside the drill body increases, exceeding the upper limit of the shear resistance of the fastening screw, causing the fastening screw to break. The separation core detaches from the drill body and moves forward, impacting the separation drill bit body. After exceeding the upper limit of the shear resistance of the connecting groove, the separation drill bit body, separation ball, and separation core detach from the drill body, leaving the lower end of the drill body open. Anchoring agent, anchor rods, or anchor cables can then be inserted through the drill rod to allow them to enter the front end of the drill bit.

[0029] This invention features a cleverly designed structure, incorporating a separation ball, a separation core, and a separation drill bit body. This allows for long-distance delivery of the separation ball and sealing of the separation core's central hole. High-pressure fluid is applied to the separation core and fastening screws, enabling precise and controllable separation of the core. The separation process is stable and effective, unaffected by drill rod orientation, drill rod angle, or drilling depth. The separation drill bit body is primarily composed of a connecting section and a front-end drill bit body. This structural design allows the separation drill bit body to withstand pressure from the soil ahead during drilling and cutting, while mitigating the internal high-pressure fluid load, enabling timely detachment. The separation core and separation drill bit body are separate components, allowing for sequential and controlled detachment, facilitating the processing and assembly of the overall structure.

[0030] This invention discloses a separable hydraulic-assisted mechanical drilling anchoring drill bit. Through a separation core and a separation drill bit body connected separately to the drill body, it ensures the normal drilling and rock-cutting functions of the drill bit during drill rod rotation. Simultaneously, high-energy fluid and a separation ball pressurize the interior of the drill body, reaching a certain pressure limit to cause the separation core and separation drill bit body to detach, opening the drill bit. This allows the anchoring agent and anchor cable / anchor rod to directly pass through the drill bit to the front of the borehole without removing the drill rod. This eliminates the need for drill rod push rods and the process of advancing the anchoring agent, anchor cable, and anchor rod in the bare hole, effectively reducing the number of steps in the anchoring construction process. The anchoring agent and anchor cable / anchor rod can enter the front of the drill bit without the need for rod removal, reducing disturbance to the borehole. This significantly reduces the number of anchoring steps, saves time, and significantly improves construction efficiency.

[0031] Based on the above-mentioned detachable hydraulic co-mechanical drilling anchoring drill bit, this invention provides an anchoring method for detachable hydraulic co-mechanical drilling. However, this method is not limited to the implementation of the detachable hydraulic co-mechanical drilling anchoring drill bit of this invention, and includes the following steps: S1. After the drill bit has drilled to the specified depth of the anchor rod or anchor cable, continue drilling to a certain depth; S2. Place the separation ball inside the hollow drill pipe, and the separation ball will enter the drill body with the high-energy fluid; S3. The separation ball is stuck at the rear end opening of the central hole, hindering the forward flow of high-energy fluid; S4. The pressure of the high-energy fluid inside the drill bit gradually increases, and the fastening screw breaks after exceeding the upper limit of the shear resistance of the fastening screw. S5. The separation ball and the separation core move forward to impact the separation drill bit body. After exceeding the upper limit of the shear resistance of the connecting slot, the separation drill bit body, the separation ball and the separation core are separated from the drill body. S6. The lower end of the drill body is open, and anchoring agent, anchor rod or anchor cable is inserted through the drill pipe to allow the anchoring agent, anchor rod or anchor cable to enter the front end of the drill bit.

[0032] This invention discloses an anchoring method for a separable hydraulic-assisted mechanical borehole. Through a separation core and a separation drill bit body connected to the drill body, the method ensures the normal drilling and rock-cutting functions of the drill bit during drill rod rotation. Simultaneously, a separation ball, supplied with high-energy fluid, pressurizes the drill body. When the pressure reaches a certain limit, the separation core and separation drill bit body detach, opening the drill bit. This allows the anchoring agent and anchor cable / anchor rod to directly pass through the drill bit to the borehole tip without needing to protrude from the drill rod. This eliminates the need for drill rod push-rod and bare-hole anchoring agent / anchor cable / anchor rod advancement processes, effectively reducing the number of steps in the anchoring construction process. The anchoring agent and anchor cable / anchor rod can enter the drill bit tip without needing to retract the rod, reducing disturbance to the borehole. This significantly reduces the number of anchoring steps, saves time, and significantly improves construction efficiency.

[0033] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principle of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A detachable hydraulically coordinated mechanical drilling anchoring drill bit, characterized in that, The system includes a drill body, a separation core, a separation drill bit body, and a separation ball. The drill body is hollow and is installed at the front end of a hollow drill rod. The separation core is located inside the drill body, with its outer side sealing against the inside of the drill body. It has a central hole in the middle and a threaded hole on its outer side. The drill body has a corresponding through hole for the threaded hole. A fastening screw passes through the through hole and connects to the threaded hole to fix the separation core inside the drill body. The separation ball is located inside the drill body and has an outer diameter larger than the central hole diameter of the separation core. It is used to seal the rear opening of the central hole during use. The separate drill bit body is installed at the front end of the drill body and includes a connecting part and a drill bit matrix. The connecting part is made of elastic material. The rear end of the connecting part extends into the drill body and is connected to the drill body groove with an interference fit. The front end of the connecting part is connected to the drill bit matrix. The drill bit matrix has a nozzle in the middle and a cutting edge on the outside. The connecting part has a connecting channel in the middle connecting the nozzle and the inside of the drill body.

2. The anchoring drill bit for detachable hydraulic-assisted mechanical drilling as described in claim 1, characterized in that, The central hole has a tapered section at its rear end opening, with the diameter gradually increasing from the inside to the outside.

3. The anchoring drill bit for detachable hydraulic-assisted mechanical drilling as described in claim 1 or 2, characterized in that, A first sealing ring is provided on the outside of the separation core and maintains a sealed fit with the inside of the drill body through the first sealing ring. Two first sealing rings are provided and are respectively distributed on both sides of the threaded hole.

4. The anchoring drill bit for detachable hydraulic-assisted mechanical drilling as described in claim 3, characterized in that, A core groove is provided at the axial midpoint of the outer side of the separation core.

5. The anchoring drill bit for detachable hydraulic-assisted mechanical drilling as described in claim 1, 2, or 4, characterized in that, The part of the connecting portion that extends into the drill body has a connecting groove at the middle position in the axial direction. The drill body has an annular protrusion structure that corresponds to the shape of the connecting groove. The two sides of the connecting groove and the rear end face of the connecting portion are all tapered transition surfaces.

6. The anchoring drill bit for detachable hydraulic-assisted mechanical drilling as described in claim 5, characterized in that, A second sealing ring is provided on the outer side of the connecting part, and the connecting part is threadedly connected to the drill body through the second sealing ring.

7. A separable hydraulic-assisted mechanical drilling anchoring drill bit as described in claim 1, 2, 4, or 6, characterized in that, The connecting channel is equipped with a spiral core to generate a rotating jet under the action of fluid.

8. An anchoring method for a detachable hydraulic-assisted mechanical borehole, characterized in that, The implementation of the abrasive waterjet grooving assisted roller rock-breaking device according to any one of claims 1-7 includes the following steps: S1. After the drill bit has drilled to the specified depth of the anchor rod or anchor cable, continue drilling to a certain depth; S2. Place the separation ball inside the hollow drill pipe, and the separation ball will enter the drill body with the high-energy fluid; S3. The separation ball is stuck at the rear end opening of the central hole, hindering the forward flow of high-energy fluid; S4. The pressure of the high-energy fluid inside the drill bit gradually increases, and the fastening screw breaks after exceeding the upper limit of the shear resistance of the fastening screw. S5. The separation ball, along with the separation core, moves forward and impacts the separation drill bit body. After exceeding the upper limit of the shear resistance of the connecting slot, the separation drill bit body, separation ball, and separation core detach from the drill body. S6. The lower end of the drill body is open, and anchoring agent, anchor rod or anchor cable is inserted through the drill pipe to allow the anchoring agent, anchor rod or anchor cable to enter the front end of the drill bit.

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