Tool for creating a conical borehole

Abstract

Tool (1) for producing a conical drill hole, with a twist drill (2) which has a drill holder (3) at one end, which has a spirally extending cutting edge (4) at the other end, which has a section (5) between the drill holder (3) and the cutting edge (4), which shows one section (5) with a smaller diameter than the area with the cutting edge (4), wherein the tool (1) shows a stop disc (6) which is firmly connected to the section (5) or the drill holder (3) and encloses the twist drill (2), wherein the tool (1) shows an annular elevation (7) which is connected to the stop disc (6) and encloses the section (5) of the twist drill (2) and is arranged between the stop disc (5) and the cutting edge (4).

Description

TECHNICAL AREA

[0001] The invention relates to a tool for creating a conical bore opening. STATE OF THE ART

[0002] German patent DE 100 46 799 C2 discloses milling cutters for creating a conical drilled opening, also called composite anchor holes, especially in aerated concrete.

[0003] The installation of heavy elements, such as canopies, awnings, and the like, requires the fastening elements to withstand greater forces. In particular, since the static properties of the brick wall (exterior wall) cannot be considered as a bearing surface, high demands are placed on the deflection stiffness and anchorage depth of the fastening (bonded anchors). Therefore, it is necessary to use anchors with a relatively large diameter that are also anchored as far as possible into the load-bearing aerated concrete wall.

[0004] These milling cutters comprise a mounting tube equipped with a drill chuck, which accommodates a pivoting blade that can be moved in and out via an actuating unit. The actuating unit includes a sleeve that moves back and forth on the mounting tube and is connected to a laterally pivoting blade via a bolt, a spring, and a linkage assembly.

[0005] This milling cutter proves to be very complicated in its construction and use. DESCRIPTION OF THE INVENTION

[0006] The invention is based on the objective of providing a tool for producing a conical bore opening that is improved compared to the prior art.

[0007] The problem is solved according to the invention with a device which has the features specified in claim 1.

[0008] Advantageous embodiments of the invention are the subject of the dependent claims.

[0009] The tool according to the invention for producing a conical borehole is provided with a twist drill having a drill holder at one end, a spirally extending cutting edge at the other end, and a section between the drill holder and the cutting edge, wherein the section has a smaller diameter than the area with the cutting edge. Furthermore, the tool includes a stop disc which is rigidly connected to the section or the drill holder and encloses the twist drill. The tool also includes an annular projection which is connected to the stop disc and encloses the section of the twist drill, and is arranged between the stop disc and the cutting edge.

[0010] The silhouette of the stop disc and the annular projection acts as a limiter to prevent the tool from tilting when drilling into a wall, particularly one made of aerated concrete. This allows for the creation of a conical borehole with this tool. Since the annular projection is positioned between the stop disc and the cutting edge, and its diameter is smaller than that of the stop disc, the conical borehole inside the wall or aerated concrete block tapers towards the wall surface and thus towards the stop disc of the tool according to the invention. This results in a highly effective drill anchor capable of absorbing and transmitting significant forces along its entire conical length without substantially compromising the stability of the wall or aerated concrete block.When creating the conical borehole, where a cylindrical borehole is usually first drilled using the spiral drill bit, the conical borehole is then milled using the cutting edge by tilting and swiveling.

[0011] The degree of tilting is determined by the silhouette of the stop disc and the ring-shaped protrusion, which directly determines the degree of tapering of the conical bore opening.

[0012] This tool according to the invention makes it possible to create a simple and robust tool that enables the creation of a conical bore opening in a simple, reproducible and safe manner.

[0013] The stop disc can completely enclose the section between the drill chuck and the cutting edge. The stop disc can be circular (with a constant radius) or have varying radii, thicknesses, or be made of different materials such as metals (e.g., steel, aluminum, iron alloys, etc.), thermosets (e.g., Teflon, PVC, polycarbonate, polyamide, polypropylene sulfide, etc.), or rigid composites or combination materials. The chosen rigid materials and the shape of the stop disc enable its function: to act as a stop, either alone or in combination with other tool components, limiting the tilt angle during use.

[0014] Stop discs made of homogeneous material with a circular diameter and constant thickness have proven to be particularly advantageous, as they are characterized by low imbalance when the tool rotates around its longitudinal axis, which improves the handling of the tool, especially when tilting.

[0015] In the tool according to the invention, the annular projection and the stop disc can be designed as separate parts or as interconnected parts of the tool. The annular projection, which extends into or is located in the space between the cutting edge and the stop disc, can project into the stop disc or even extend through it towards the drill chuck.

[0016] The annular protrusion and the cutting edge of the twist drill can touch or overlap. It is also possible for the annular protrusion and the cutting edge of the twist drill to be positioned at a distance from each other within the section of the twist drill. This distance is preferably chosen to be smaller than the distance determined by the silhouette of the annular protrusion and the stop disc. This reduced distance enables effective and efficient milling of the conical bore.

[0017] It has proven particularly advantageous to further develop the inventive tool for creating a conical borehole such that the annular projection is designed as a disc with a central hole for receiving the section of the twist drill and is detachable from the stop disc. The stop disc and the annular projection form contact surfaces that can move relative to each other. This creates a flexible system of stop disc and annular projection that can adapt to external conditions during tool use, particularly when tilted, and is characterized by greater durability. This is especially true when the diameter of the central hole is slightly larger than the diameter of the section of the twist drill in which the annular projection is located.

[0018] The ring-shaped and disc-shaped elevation can be formed with a constant radius, i.e., circular, or with different radii, different thicknesses, or from different materials such as metals (e.g., steel, aluminum, iron alloys, etc.), thermosets (e.g., Teflon, PVC, polycarbonate, polyamide, polypropylene sulfide, etc.), or from rigid composite materials or combination materials.

[0019] Ring-shaped and disc-shaped protrusions made of homogeneous material with a circular diameter and constant thickness have proven to be particularly advantageous, as they are characterized by low imbalance when the tool rotates around its longitudinal axis, which improves the handling of the tool, especially when tilting.

[0020] Furthermore, it has proven particularly advantageous to further develop the inventive tool for creating a conical bore opening in such a way that the ring- and disc-shaped protrusion and the stop disc have contact surfaces which are designed as dome-shaped contact surfaces that allow them to slide along each other over a flat surface.

[0021] Additionally, it has proven advantageous to design the hole of the protrusion with a larger diameter than the section, so that there is a clearance or play between the protrusion and the section of the spiral drill bit, allowing the protrusions of the stop disc to tilt relative to each other.

[0022] This unique, smooth sliding action, combined with the tilting capability, allows the tool to mill conical bore openings with exceptional ease and safety. This is because the sliding action provides guidance both during the rotation of the twist drill and when the tool is tilted. This makes the tool particularly easy and safe to handle. Furthermore, it ensures exceptionally high precision when creating the conical bore opening.

[0023] It has proven particularly effective to design the spherical surfaces with the same or nearly the same radius, resulting in exceptionally well-designed contact surfaces. This ensures excellent handling of the tool and high manufacturing precision.

[0024] Besides the option of providing the disc-shaped protrusion with a conical recess and the stop disc with a conical bulge, it has proven particularly effective to provide the stop disc with a conical recess and, conversely, the disc-shaped protrusion with a corresponding conical bulge. This design proves to be particularly stable, since the shape of the stop disc, with its preferably detachable fixation to the twist drill, allows for the provision of a corresponding recess on the surface facing the protrusion without significant loss of stability. Furthermore, this type of tool proves to be less susceptible to wear.

[0025] Alternatively or additionally, it has proven particularly effective to further develop the tool for creating a conical borehole so that the twist drill has a conical taper in the area of ​​the cutting edge and / or the section between the cutting edge and the stop plate, tapering towards the drill chuck. By providing a smoothly tapering section, the stability of the twist drill is increased, thereby further improving the tool's durability.

[0026] The arrangement of the tapered section in the cutting area has the disadvantage that the stability of the twist drill is significantly reduced due to the reduction in radius in conjunction with the cutting edge, while the positioning of the stop washer or the raised section is improved due to the constant or largely constant radius. Conversely, the advantages of arranging the transition area exclusively in the section are offset by disadvantages, and vice versa. The preferred solution is to arrange the tapered section in the transition area between the cutting edge and the section, thus encompassing both, as this represents a particularly favorable compromise between stability and flexibility in positioning the stop washer and the raised section.

[0027] A particularly preferred tool according to the invention is one in which the section between the cutting edge and the drill holder has a cylindrical area with a smaller diameter than the cutting edge area. This cylindrical area can be located adjacent to a tapered section and between the subsequent section and the drill holder. It has proven advantageous for the diameter of the cylindrical area to correspond approximately to the smallest diameter of the tapered section. The cylindrical area has no cutting edge and thus, in particular, a smooth surface, which may transition smoothly or almost seamlessly into the smooth surface of the tapered section, thereby ensuring exceptional tool stability.

[0028] A particularly preferred embodiment of the invention shows the possibility that the conically tapered region tapers uniformly, particularly at an angle α of approximately 10°. This stability is especially advantageous with a uniformly tapered region. Here, a taper at an angle α of approximately 10°, for example 7.5°, has proven particularly effective.

[0029] A particularly preferred embodiment of the invention shows a tool for creating a conical borehole, in which the angle α corresponds to the opening angle defined by the height of the protrusion and the distance between the highest point of the protrusion and the edge of the stop disc. This design of the silhouette, consisting of the protrusion and the stop disc, and in particular the highest point of the protrusion and the edge of the stop disc, makes it possible to limit or define the maximum inclination of the tool when inserting, especially when milling, the conical borehole. This allows the opening angle α to be selected such that the conical borehole provides a particularly stable connection in the porous building material, especially in aerated concrete. A taper at an angle α of approximately 10°, and in particular 7.5°, has proven especially effective in this regard.

[0030] In a preferred embodiment of the inventive tool for creating a conical borehole, it has proven particularly advantageous to attach the tool's stop disc firmly but releasably to the twist drill. This releasable stop disc allows its position along the twist drill in the area of ​​the drill chuck or the section to be varied, thereby adjusting the drilling depth and, if necessary, the length of the conical bore to the specific requirements of the construction site. Furthermore, it enables the stop disc to be replaced with a new, possibly modified, one as needed, which is beneficial for maintenance, ensuring the tool's continued functionality and longevity. This also ensures consistently good handling over an extended period.

[0031] In addition to the particularly stable and robust design of the tool for creating a conical bore opening with a one-piece stop plate, it has also proven effective to equip the tool for creating a conical bore opening with a stop plate that has an annular recess. This recess is designed to partially accommodate the raised section or, alternatively, to partially accommodate the raised section using an annular receiving piece inserted into the annular recess. By providing the annular recess as a receiving element for the raised section itself, or for both the receiving piece and the raised section, a particularly stable structure is created for such a tool, which proves to be exceptionally robust and stable.It has proven particularly advantageous to design the annular recess or receiving element on its surface facing the protrusion in such a way that it correlates with the surface of the annular protrusion, specifically exhibiting a corresponding dome-shaped structure or surface characterized by uniformly and extensively formed contact areas. This preferred design proves to be exceptionally robust and very easy to handle. By providing such a receiving element, it becomes possible to adapt it to the function through appropriate material selection, thereby enabling particularly efficient sliding of the contact surfaces against each other with low wear and low resistance.

[0032] According to a preferred embodiment of the invention, the tool for creating a conical bore opening is provided with a receiving piece that is permanently and, in particular, detachably connected to the stop disc. Of the various permanent connections such as gluing, welding, riveting, screwing, or snap-fit ​​connections, the detachable ones have proven to be particularly advantageous. Before considering the permanent and detachable connections of the stop disc to the receiving piece, screwing has proven to be particularly easy to handle, secure, and yet detachable. Furthermore, the detachable connection allows for the targeted replacement of individual components during maintenance or repair processes, thereby ensuring the tool remains functional in the long term.

[0033] In a preferred embodiment of the inventive tool for producing a conical bore, it has proven particularly advantageous to provide the tool with a thrust washer having a hole through which the twist drill extends. The thrust washer is designed such that it can rotate freely around the twist drill, that it is positioned between the cutting edge and the stop washer, and that it can rotate freely relative to the stop washer. Preferably, it is made of plastic.

[0034] This thrust washer effectively mediates and compensates for the movement between the protrusion and the stop disc against the wall into which the conical bore is to be drilled, thus significantly simplifying tool handling. Furthermore, the use of this thrust washer reduces the risk of damaging the wall surface, thereby improving the quality of the conical bore drilling process. The use of a plastic thrust washer allows for frequent replacement, particularly after drilling one or a few holes, ensuring the tool's long-term functionality.Elastomeric plastics have proven to be particularly advantageous and effective, as their elastic properties make them especially suitable for efficiently compensating for different movements.

[0035] Furthermore, it has proven particularly advantageous to further develop the tool for creating a conical bore opening in such a way that the raised section extends through the hole of the thrust washer and protrudes beyond the thrust washer. This design of the thrust washer, or rather the raised section of the tool, proves to be particularly easy to handle and especially stable and robust.

[0036] Furthermore, it has proven particularly advantageous to further develop the tool for creating a conical bore opening by providing the thrust washer with a profile on its surface. This profile, located on the side facing the cutting edge or the wall to be drilled, and / or on the side of the thrust washer itself, effectively compensates for differing movements of the thrust washer relative to the wall or the stop washer, thereby improving both handling and the tool's service life.

[0037] In a particularly preferred embodiment of the tool according to the invention for producing a conical bore, it has one or more magnets that press the protrusion and / or the thrust washer against the stop disc by means of magnetic force. This effective yet flexible type of soft fixation between the stop disc and the thrust washer or protrusion ensures that the connection is released even under high forces, thereby preventing or reducing damage to the tool components and significantly increasing the tool's durability. This design of the tool also proves to be very advantageous in handling, since the tool components are connected as a unit by magnetic force. This unit remains connected during normal use, while it can be separated in extreme cases or in the event of a malfunction.

[0038] The invention is explained below by way of example with reference to preferred embodiments and the illustrations. The invention is not limited to these preferred embodiments. Fig. Figure 1 shows a schematic representation in a side view of an exemplary tool according to the invention for creating a conical bore opening, Fig. Figure 2 shows a schematic sectional view along the longitudinal axis of the exemplary tool used to create a conical borehole in a wall made of Fig. 1 and Fig. Figure 3 shows a schematic representation of the exemplary tool from Fig. 1 as an exploded view and in an oblique view.

[0039] In the Fig. 1, Fig. 2 to Fig. Figure 3 shows an exemplary tool 1 according to the invention for creating a conical bore opening in schematic representations.

[0040] The exemplary tool 1 according to the invention for producing a conical borehole is provided with a twist drill 2, which has a drill holder 3 at one end, a spirally extending cutting edge 4 at the other end, and a section 5 between the drill holder 3 and the cutting edge 4. The section 5 has a smaller diameter than the area with the cutting edge 4. In the section 5, the diameter of the twist drill 2 tapers towards the drill holder 3, which has a constant diameter.

[0041] Furthermore, the tool 1 shows a stop disc 6, which is firmly connected to the section 5 or the drill holder 3 and encloses the twist drill 2. The tool 1 also shows an annular projection 7, which is at least loosely connected to the stop disc 6 and encloses the section 5 of the twist drill 2, and is arranged between the stop disc 6 and the cutting edge 4.

[0042] The silhouette of the stop disc 6 and the ring-shaped elevation 7 provides a limit to the tilting of the tool 1 when drilling a hole in a wall 20, especially one made of aerated concrete, thus making it possible to create a conical borehole with this tool 1.

[0043] Since the annular projection 7 is arranged between the stop disc 6 and the cutting edge 4, and since the annular projection 7 has a smaller diameter than the stop disc 6, the conical borehole inside the wall 20 or inside the aerated concrete block is designed such that it tapers towards the surface of the wall 20 and thus towards the stop disc 6 of the tool 1 according to the invention. This results in a very effective drill anchor that can absorb and transmit large forces over its entire conical length without significantly impairing the stability of the wall 20 or the aerated concrete block. When creating the conical borehole, in which a cylindrical borehole is typically first drilled using the twist drill 2, the conical borehole is then milled using the cutting edge 4 by tilting and pivoting the tool 1.

[0044] The degree of tilting is determined by the silhouette of the stop disc 6 and the ring-shaped elevation 7, which directly determines the degree of tapering of the conical bore opening.

[0045] This tool 1 according to the invention makes it possible to create a simple and robust tool 1 which enables the creation of a conical bore opening in a simple and safe manner.

[0046] The stop disc 6 completely and annularly encloses the section 5 between the drill chuck 3 and the cutting edge 4. The stop disc 6 has a constant radius and is therefore designed as a disc with a circular cross-section. It has a uniform thickness or is made of a uniform material such as steel or aluminum. The selected rigid materials, as well as the shape of the stop disc, enable the stop disc 6 to function as a stop, either alone or in combination with other components of the tool 1, thus limiting the tilt angle during use.

[0047] Furthermore, such stop discs have proven to be particularly advantageous, as they are characterized by a low imbalance when the tool 1 rotates around the longitudinal axis, which improves the handling of the tool 1, especially when tilting.

[0048] In this tool 1, the annular projection 7 and the stop disc 6 are designed as separate parts that can come into contact with each other and thus be interconnected. The annular projection 7, which extends into or is located in the space between the cutting edge 4 and the stop disc 6, projects into the stop disc 6 in the direction of the drill chuck 3.

[0049] The annular projection 7 and the cutting edge 4 of the twist drill are arranged at a distance from each other in the section 5 of the twist drill 2. This distance is preferably chosen to be smaller than the distance determined by the silhouette of the annular projection 7 and the stop disc 6. This reduced distance enables effective and efficient milling of the conical bore opening.

[0050] The stop disc 6 is detachably connected to the drill holder 3 of the twist drill 2. The fixed but detachable connection 6a is achieved by means of an Allen screw 6a, which is inserted into a bore with an internal thread in the stop disc 6, by means of which the stop disc 6 is fixed to the drill holder 3 of the twist drill 2 by means of a clamping screw.

[0051] The annular projection 7 is designed as a disc with a central hole 8 for receiving the section 5 of the spiral drill 2 and is detachable from the stop disc 6. The stop disc 6 and the annular projection 7 form contact surfaces 9, 10, which are designed as dome-shaped contact surfaces 9, 10 that allow them to slide along each other over a flat surface.

[0052] This creates a flexible system consisting of a stop disc 6 and annular projection 7, which can adapt to external conditions during the use of the tool 1, particularly when tilted, and is characterized by greater durability. This is especially true when the diameter of the central hole 8 is slightly larger than the diameter of the section 5 of the twist drill 2 in which the annular projection 7 is located.

[0053] The ring-shaped and disc-shaped elevation 7 exhibits a constant radius with uniform thickness and is made of a homogeneous material such as steel or aluminum. This results in low imbalance when the tool rotates around its longitudinal axis, thus improving the tool's handling, especially when tilted.

[0054] The tool 1 for producing a conical bore opening is to be provided with a stop disc 6 which has an annular recess designed to at least partially receive an annular receiving piece 14 and the annular projection 7. The receiving piece 14 and the annular projection 7 have the dome-shaped contact surfaces 9, 10.

[0055] By providing the ring-shaped elevation as a receiving option for the receiving piece 14 and the ring-shaped elevation 7, a particularly stable structure is created for such a tool 1, which proves to be particularly robust and stable.

[0056] By providing such a receiving piece 14, it becomes possible to adapt it to the function by appropriately selecting the material, thereby enabling particularly efficient sliding when in contact with each other with low wear and low resistance.

[0057] The receiving element 14 is detachably but firmly connected to the rest of the stop disc 6 by means of a releasable adhesive bond and can be replaced with a spare receiving element 14 if necessary, which enhances the durability and longevity of the tool 1 according to the invention. The fixing elements 14a, which are designed as magnets 14a, are permanently fixed in the receiving element 14 and are designed to use magnetic force to pull the annular projection 7 towards the stop disc 6 with the receiving element 14, thereby bringing them into contact as desired and enabling mutual sliding. By selecting the magnet strength, and in particular by choosing neodymium magnets, it is possible to precisely adjust the necessary force for sliding without compromising the security of the connection between the stop disc 6 and the projection 7.This ensures particularly safe handling with high and reproducible quality when creating the conical bore.

[0058] A thrust washer 15 is arranged between the stop disk 6 and the cutting edge 4. This thrust washer has a central hole 16, which is designed such that the projection 7, with the twist drill 2 located therein, can protrude through the thrust washer 15. The thrust washer 15 is annular and has a folded edge that surrounds the edge of the stop disk 6. The thrust washer 15 is made of a rubber-elastic material. It is designed to rotate freely around the twist drill 2.

[0059] This allows the thrust washer 15 to rotate freely relative to the stop washer 6 and the spiral drill bit 2.

[0060] This thrust washer 15 makes it possible to mediate and compensate the movements between the raised area 7 and the stop washer 6 relative to the wall 20 into which the conical bore is to be made, thus significantly simplifying the handling of the tool 1.

[0061] Furthermore, the provision of this thrust washer 15 reduces the risk of damage to the surface of the wall 20 and thus increases the quality of the process of drilling the conical bore. In particular, the selection of a thrust washer 15 made of an elastomeric plastic makes it possible to replace the thrust washer 15 regularly and therefore more frequently, especially after drilling one or a few bores, thus ensuring the long-term and sustainable functionality of the tool 1.

[0062] The described tool 1 enables the sustainable creation of a conical borehole in a wall, particularly one made of aerated concrete. It is characterized above all by its robustness and its very simple and safe application. Reference symbol list 1 tool for creating a conical bore opening 2 spiral drill bits 3 Drill chuck 4 spirally arranged cutting edges 5 Section between drill chuck and cutting edge 6 Stop disc 6a Fixing the stop disc to the spiral drill bit 7 ring-shaped elevation 8 central hole in the ring-shaped protrusion for the spiral drill bit 9 Contact surface 10 Contact surface 11. tapered section of the spiral drill bit 12 Transition area 13 ring-shaped recesses 14 ring-shaped receiving piece 14a Fixing element, magnet 15 Thrust washer 16 central hole in the thrust washer for elevation 20 wall QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 100 46 799 C2

[0002]

Claims

Tool (1) for producing a conical borehole, comprising a twist drill (2) having a drill holder (3) at one end, having a spirally extending cutting edge (4) at the other end, having a section (5) between the drill holder (3) and the cutting edge (4), having a section (5) with a smaller diameter than the area with the cutting edge (4), wherein the tool (1) comprises a stop disk (6) which is firmly connected to the section (5) or the drill holder (3) and encloses the twist drill (2), wherein the tool (1) comprises an annular projection (7) which is connected to the stop disk (6) and encloses the section (5) of the twist drill (2) and is arranged between the stop disk (5) and the cutting edge (4). Tool for producing a conical borehole according to claim 1, wherein the annular protrusion (7) is designed as a disk with a central hole (8) for receiving the section (5) of the spiral drill (2) and is detachable from the stop disk (6), and wherein the stop disk (6) and the annular protrusion (7) form contact surfaces (9, 10). Tool for producing a conical bore opening according to claim 2, wherein the ring- and disc-shaped elevation (7) and the stop disc (6) are designed such that their dome-shaped contact surfaces (9, 10) are designed so that they can slide along one another in a planar manner and can incline towards each other in conjunction with the hole (8), which has a larger diameter than the section (5). Tool for producing a conical bore opening according to one of claims 1 or 3, wherein the twist drill (2) has a conically tapered area (11) in the area of ​​the cutting edge (4) and / or the section (5) in the direction of the drill holder (3). Tool for producing a conical bore opening according to claim 4, wherein the conically tapered area (11) tapers conically uniformly, in particular at an angle α of about 10°. Tool for producing a conical bore opening according to claim 5, wherein the angle α corresponds to the opening angle defined by the height of the annular protrusion (7) and the distance between the highest point of the annular protrusion (7) and the edge of the stop disc (6). Tool for producing a conical bore opening according to one of claims 1 to 6, wherein the section (5) between the cutting edge (4) and the drill holder (3) has a region which has a cylindrical shape and a smaller diameter than the region with the cutting edge (4). Tool for producing a conical bore opening according to one of claims 1 to 7, wherein the stop disc (6) is detachably attached to the spiral drill (2). Tool for producing a conical bore opening according to one of claims 1 to 8, wherein the stop disc (6) has an annular recess which is provided to partially accommodate the elevation (7) in height or to partially accommodate the elevation (7) in height by means of an annular receiving piece (14) inserted into the annular recess (13). Tool for producing a conical bore opening according to claim 9, wherein the receiving piece (14) is detachably and firmly connected to the stop disc (6), in particular by screwing. Tool for producing a conical bore opening according to one of claims 1 to 10, wherein the tool (1) has a thrust washer (15) in particular made of plastic with a hole (16) through which the twist drill (2) extends, which can rotate freely around the twist drill (2), which is arranged between the cutting edge (4) and the stop washer (6) and which can rotate freely relative to the stop washer (6). Tool for producing a conical bore opening according to claim 11, wherein the protrusion (7) extends through the hole (16) of the thrust washer (15) and projects beyond the thrust washer (15). Tool for producing a conical bore opening according to one of claims 11 to 12, wherein the thrust washer (15) is provided with a profile on its surface. Tool for producing a conical bore opening according to one of claims 1 to 13, further comprising one or more magnets (14a) which press the protrusion and / or the thrust washer (15) against the stop washer (6) by means of magnetic force.

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