Hollow hole-cutting drill bit

Abstract

A hollow hole-cutting drill bit (10), comprising a drill bit head (11) located at a distal end, wherein the drill bit head (11) is provided with a plurality of cutting teeth (13) distributed around an operating rotation axis, and each cutting tooth (13) comprises a plurality of cutting sections (14) arranged in sequence in an axial direction, the plurality of cutting sections (14) being arranged in sequence towards a radial outer side in a radial direction as same are arranged in sequence towards a proximal side in the axial direction, thereby forming a stepped structure, the plurality of cutting sections (14) comprising one end section (15) and one or more circumferential step sections (16), the end section (15) being located at the most distal end of the corresponding cutting tooth (13) in the axial direction and comprising an end cutting edge (28), and the circumferential step section (16) being positioned on a proximal side of the end section (15) in the axial direction. During a drilling process, a cutting force can be decomposed, thereby reducing the cutting heat and the deformation of the cutting teeth (13), and helping to divide cutting chips, and thus helping to prolong the service life.

Description

Hollow hole drill bit Technical Field

[0001] The present invention relates to the field of cutting tools, and more particularly to a hollow hole drill. Background Art

[0002] In industrial production, it is often necessary to drill holes with large apertures. If a solid drill bit is used, the drill bit will be subjected to great stress and will generate a large amount of cutting heat. In order to solve the above problem, a hollow hole drill bit can be used, so that the material in the entire volume surrounded by the hole does not need to be drilled out, but only the material in the annular part needs to be drilled out. When drilling through the hole, the material of the part surrounded by the annular part (generally referred to as the "core") falls down. At present, hollow hole drill bits (for example, steel plate drills) are widely used in magnetic base drilling machines, bench drilling machines, drilling and milling machines, etc., to cut holes of different sizes in plates and cut off the core.

[0003] Figure 1 shows a schematic diagram of a hollow drill bit 1 in the prior art. Figure 2 shows an end view of the hollow drill bit 1 in Figure 1 as viewed along the axial direction, schematically illustrating two cutting teeth, namely a first cutting tooth 2 and a second cutting tooth 3. n represents the rotational direction of the hollow drill bit 1 during operation, and B represents the radial thickness of the hollow drill bit 1. Figures 3A and 3B are views of the first cutting tooth 2 and the second cutting tooth 3, respectively, as viewed along the AA and BB directions in Figure 2. These views show that the main flank face of the first cutting tooth 2 has a segment 4 in a radial plane, and the main flank face of the second cutting tooth 3 has two segments 5 at angles to each other. The shape of the main flank face of each cutting tooth in the aforementioned radial plane reflects the shape of the corresponding main cutting edge.

[0004] As further shown in Figures 3A and 3B , in this design of a hollow hole drill 1 , the axial length of the cutting edge of the cutting teeth (corresponding to the Lr indicated in Figures 3A and 3B ) is often relatively short. This results in all cutting teeth participating in the drilling process within a very short time and a very small axial range during the drilling process. This results in greater cutting resistance, leading to higher cutting power consumption. Furthermore, this also results in a larger cross-sectional area of ​​the chips, making chip evacuation difficult and generating high cutting heat. This hollow hole drill 1 also presents problems such as difficulty positioning and difficulty in cutting during the initial drilling process, which can easily damage the drill bit and the drilling machine. Poor chip evacuation can also lead to the undesirable phenomenon of chips being discharged toward the drill core. Furthermore, due to the large cross-sectional area of ​​the chips, as shown in Figure 4 , when the hole in the workpiece 7 is almost drilled through, the thinner portion to be cut is more likely to be torn and split rather than neatly cut. This can result in a "hat-brim"-like structure 9 at the edge of the core 8, making it difficult to drill multiple layers of a plate-like workpiece 7.

[0005] Summary of the Invention

[0006] Therefore, the present invention aims to provide a hollow hole drill bit, by means of which at least one of the technical problems existing in the prior art can be solved.

[0007] The present invention relates to a hollow hole drill bit, comprising a drill head located at a distal end of the hollow hole drill bit, the drill head having a plurality of cutting teeth distributed around a working rotation axis of the hollow hole drill bit, each cutting tooth comprising a plurality of cutting segments arranged sequentially in an axial direction,

[0008] The plurality of cutting segments are sequentially arranged toward the proximal side in the axial direction and toward the radial outer side in the radial direction, thereby forming a step-like structure.

[0009] Wherein, the multiple cutting segments include an end segment and one or more circumferential step segments, the end segment is located at the farthest end of the corresponding cutting tooth in the axial direction and includes an end cutting edge, the circumferential step segment is positioned proximal to the end segment in the axial direction, each circumferential step segment extends generally in the circumferential direction and includes a main cutting edge and a secondary cutting edge.

[0010] The hollow drill bit according to the present invention can decompose cutting forces during the drilling process, reducing cutting resistance and power, cutting heat, and deformation of the cutting teeth. It also helps to divert chips to reduce the area of ​​individual chips, thereby facilitating chip removal, preventing chip jams, and reducing the tendency of chips to be discharged toward the core. This helps to extend the service life of the hollow drill bit and improve machining quality. Furthermore, the hollow drill bit according to the present invention can achieve relatively accurate positioning and easy penetration during initial penetration into the workpiece, which reduces the chance of damage and scrapping of the hollow drill bit during use. Furthermore, the hollow drill bit according to the present invention can also help to undercut the core to reduce the brim-like structure at the bottom of the core, thereby enabling continuous drilling through stacked workpieces.

[0011] In some embodiments, the main cutting edge in the circumferential step section:

[0012] is of one-piece design and therefore comprises a single main cutting edge section; or

[0013] It is multi-segmented and therefore comprises a plurality of main cutting edge segments, between which two adjacent cutting edge segments each form an angle.

[0014] In some embodiments, one or more of the cutting teeth each include a plurality of circumferential step sections, the orientation and size of the major cutting edges and the minor cutting edges of the plurality of circumferential step sections being identical to each other.

[0015] In some embodiments, one or more of the cutting teeth each include a plurality of circumferential step sections, wherein the plurality of circumferential step sections meet one or more of the following conditions:

[0016] The main cutting edge of each circumferential step section is configured as a single segment, and the orientation and / or size of the respective main cutting edges are at least partially different from each other;

[0017] The number of segments of the main cutting edges of the respective circumferential step segments is at least partially different from each other;

[0018] The orientation and / or the size of the minor cutting edges of the individual circumferential step sections differ at least partially from one another.

[0019] In some embodiments, the end cutting edge and the main cutting edge of each circumferential step segment are both constructed in one piece, and the rake angles of the end cutting edge and the main cutting edge of each circumferential step segment are respectively between -30° and +30°.

[0020] In some embodiments, in the axial plane, the thickness of the end segment in the radial direction and the thickness of each circumferential step segment in the radial direction are respectively one-half to one-fifth of the wall thickness of the hollow hole drill bit in the radial direction; and / or,

[0021] The sum of the thickness of the end section in the radial direction and the thickness of each circumferential step section in the radial direction is equal to the wall thickness of the hollow hole drill in the radial direction.

[0022] In some embodiments, the end cutting edge:

[0023] - is of one-piece design and therefore comprises a single cutting edge segment; or

[0024] It is multi-segmented and therefore comprises a plurality of cutting edge segments, wherein an angle is formed between each two adjacent cutting edge segments.

[0025] In some embodiments, in the axial plane, the thickness of the end segment in the radial direction and the thickness of each circumferential step segment in the radial direction are equal to or at least partially unequal to each other; and / or

[0026] The end cutting edge and the main cutting edge of each circumferential step section are both constructed in one section, and the rake angles of the end cutting edge and the main cutting edge in each circumferential step section are equal to or at least partially unequal to each other.

[0027] In some embodiments, in the axial direction, the total length of the plurality of cutting segments of each cutting tooth is not less than half the depth of the groove between the cutting tooth and any adjacent cutting tooth.

[0028] In some embodiments, at least two cutting teeth in the plurality of cutting teeth have the same tooth shape.

[0029] In some embodiments, at least two cutting teeth of the plurality of cutting teeth have different tooth shapes and satisfy one or more of the following:

[0030] The at least two cutting teeth have end sections of different configurations;

[0031] The at least two cutting teeth have different numbers of circumferential step sections;

[0032] The sizes and orientations of the main cutting edges and the secondary cutting edges of the circumferential step sections of the same sequence starting from the circumferential step section furthest in the axial direction of the at least two cutting teeth are at least partially different from each other.

[0033] In some embodiments, the at least two cutting teeth have end sections of different configurations and satisfy one or more of the following:

[0034] The number of segments of the cutting edge sections of each end cutting edge is different;

[0035] The main angles of the cutting edge sections of the end cutting edges located at the innermost ends in the radial direction are different;

[0036] Each end cutting edge is configured as one segment, and the lengths and / or rake angles of the respective end cutting edges are different.

[0037] In some embodiments, the at least two cutting teeth have different numbers of circumferential step segments, and the orientation and size of the main cutting edges and secondary cutting edges of each circumferential step segment in the same sequence starting from the axially farthest circumferential step segment of the at least two cutting teeth are the same as each other.

[0038] In some embodiments, each circumferential step section of the at least two cutting teeth in the same sequence starting from the circumferential step section furthest in the axial direction satisfies one or more of the following conditions:

[0039] The main cutting edge of each circumferential step segment is configured in one segment, and the orientation and / or size of the main cutting edge of each circumferential step segment are different from each other;

[0040] The main cutting edge of each circumferential step section is constructed in one section, and the main cutting edge of each circumferential step section has a different rake angle;

[0041] The number of segments of the main cutting edge of each circumferential step section is different;

[0042] The minor cutting edges of the individual circumferential step sections may be oriented and / or dimensioned differently.

[0043] In some embodiments, the at least two cutting teeth satisfy one or both of the following conditions:

[0044] The distal ends in the axial direction are located at different axial positions;

[0045] The inner ends in the radial direction are located at different radial positions.

[0046] In some embodiments, the at least two cutting teeth are arranged adjacent to each other in the circumferential direction, the at least two cutting teeth constitute a cutting tooth group, and the core hole drill bit includes a plurality of the cutting tooth groups arranged successively in the circumferential direction.

[0047] In some embodiments, the at least two cutting teeth include a first cutting tooth and a second cutting tooth, the first cutting tooth includes one circumferential step section, and the second cutting tooth includes two circumferential step sections.

[0048] In some embodiments, the plurality of cutting teeth are evenly spaced about the working rotational axis of the core hole drill bit.

[0049] In some embodiments, the hollow hole drill bit includes at least one first cutting tooth, the end cutting edge of the first cutting tooth and the main cutting edge in each circumferential step section are constructed as a one-piece type, and include at least one arc-shaped cutting edge, each of the arc-shaped cutting edges is recessed inward toward the working rotation axis or protrudes outward away from the working rotation axis in the radial direction.

[0050] In some embodiments, the first cutting tooth includes a plurality of arcuate cutting edges, and the plurality of arcuate cutting edges have the same size and orientation.

[0051] In some embodiments, the first cutting tooth only includes the arc-shaped cutting edge, and the hollow hole drill bit includes at least one second cutting tooth, the end cutting edge of the second cutting tooth and the main cutting edge in each circumferential step segment are both constructed as a one-piece type and only include straight cutting edges. Preferably, the second cutting tooth includes multiple circumferential step segments, and the main cutting edges of each circumferential step segment have the same orientation and size.

[0052] In some embodiments, the first cutting tooth and the second cutting tooth have the same number of circumferential step sections.

[0053] In some embodiments, the first cutting teeth and the second cutting teeth are arranged adjacent to each other in a circumferential direction to form a cutting tooth group, and the core hole drill bit includes a plurality of the cutting tooth groups.

[0054] In some embodiments, the first cutting tooth and the second cutting tooth satisfy one or both of the following conditions:

[0055] The distal ends in the axial direction are located at different axial positions;

[0056] The inner ends in the radial direction are located at different radial positions.

[0057] The technical features mentioned above, the technical features described below, and the technical features shown individually in the accompanying drawings may be combined arbitrarily, as long as the combined technical features do not conflict with each other. All possible feature combinations are technical contents explicitly described in this document. Any of the multiple sub-features included in the same statement can be applied independently and does not necessarily have to be applied in conjunction with the other sub-features. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] The present invention is further described below with reference to the accompanying drawings and embodiments, in which:

[0059] FIG1 shows a perspective view of a hollow hole drill bit in the prior art.

[0060] FIG2 shows a schematic end view of the hollow hole drill bit in FIG1 as viewed in the axial direction, wherein the positions of the first cutting teeth and the second cutting teeth are marked.

[0061] 3A and 3B respectively show views viewed along the AA direction and the BB direction in FIG. 2 .

[0062] FIG4 is a schematic diagram showing a workpiece machined by some hollow hole drill bits in the prior art and a core cut off by the casing.

[0063] FIG. 5 illustrates a perspective view of a core drilling bit according to some embodiments of the present invention.

[0064] FIG6 shows a schematic end view of the core drilling bit in FIG5 as viewed in the axial direction, wherein exemplary positions of the first cutting teeth and the second cutting teeth are marked.

[0065] FIG. 7A shows a side view of the core drilling bit of FIG. 5 , with the position of the first cutting tooth marked.

[0066] FIG. 7B shows an enlarged perspective view of the first cutting tooth in FIG. 7A .

[0067] FIG. 7C illustrates a view of the first cutting tooth according to some embodiments of the present invention, viewed along the MM direction in FIG. 6 .

[0068] 7D illustrates an end view of a first cutting tooth in an axial plane according to some embodiments of the present invention, as viewed in the axial direction of the core drilling bit of FIG. 5 .

[0069] FIG. 8A shows a side view of the core drilling bit of FIG. 5 , with the position of the second cutting tooth marked.

[0070] FIG. 8B shows an enlarged perspective view of the second cutting tooth in FIG. 8A .

[0071] FIG. 8C illustrates a view of the second cutting tooth according to some embodiments of the present invention, viewed along the QQ direction in FIG. 6 .

[0072] 8D illustrates an end view of a second cutting tooth in an axial plane according to some embodiments of the present invention, as viewed in the axial direction of the core drilling bit of FIG. 5 .

[0073] FIG9 is a schematic diagram showing a workpiece machined by the hollow hole drill in FIG5 and a core cut by the casing.

[0074] FIG. 10 shows a perspective view of a core drilling bit according to other embodiments of the present invention.

[0075] 11A and 11B are perspective views of a drill head of a core drilling bit according to other embodiments of the present invention.

[0076] FIG. 12 shows a perspective view of a core drilling bit according to still other embodiments of the present invention.

[0077] Figure 13 shows a schematic diagram of a circumferential step segment on a first cutting tooth of a hollow hole drill according to some embodiments of the present invention and a circumferential step segment on a second cutting tooth rotated to the same circumferential position when viewed along a direction perpendicular to the axial direction, wherein the main cutting edges of the two circumferential step segments shown are both arc-shaped cutting edges and are recessed inward in the radial direction toward the working rotation axis.

[0078] Figure 14 shows a schematic diagram of a circumferential step segment on a first cutting tooth of a hollow hole drill according to some embodiments of the present invention and a circumferential step segment on a second cutting tooth rotated to the same circumferential position when viewed along a direction perpendicular to the axial direction, wherein the main cutting edges of the two circumferential step segments shown are both arc-shaped cutting edges and protrude outward in the radial direction away from the working rotation axis.

[0079] Figure 15 shows a schematic diagram of a circumferential step segment on a first cutting tooth and a circumferential step segment on a second cutting tooth rotated to the same circumferential position of a hollow hole drill according to some embodiments of the present invention when viewed along a direction perpendicular to the axial direction, wherein one of the main cutting edges of the two circumferential step segments shown is an arc-shaped cutting edge and is recessed inward in the radial direction toward the working rotation axis, and the other is a straight cutting edge.

[0080] Figure 16 shows a schematic diagram of a circumferential step segment on a first cutting tooth of a hollow hole drill according to some embodiments of the present invention and a circumferential step segment on a second cutting tooth rotated to the same circumferential position when viewed along a direction perpendicular to the axial direction, wherein one of the main cutting edges of the two circumferential step segments shown is an arc-shaped cutting edge and protrudes outward in the radial direction away from the working rotation axis, and the other is a straight cutting edge.

[0081] 17 illustrates a partial perspective view of a core drilling bit according to some embodiments of the present invention. DETAILED DESCRIPTION

[0082] Various illustrative embodiments of the present invention are described below. In this specification, for the sake of explanation only, various systems, structures and devices are schematically depicted in the accompanying drawings, but not all features of the actual systems, structures and devices are described, such as well-known functions or structures are not described in detail to avoid unnecessary details that make the present invention unclear. It should be understood that in any actual application, many specific implementation decisions need to be made to achieve the specific goals of the developer or user, and system-related and industry-related restrictions need to be followed, and these specific goals may vary from one actual application to another. In addition, it should be understood that such specific implementation decisions, although complex and time-consuming, are routine tasks for those of ordinary skill in the art who benefit from this application.

[0083] The terms and phrases used herein should be understood and interpreted as having a meaning consistent with the understanding of those terms and phrases by those skilled in the relevant art. No special definition of a term or phrase, i.e., a definition that is different from the ordinary and customary meaning as understood by those skilled in the art, is intended to be implied by consistent usage of a term or phrase herein. For terms or phrases that are intended to have a special meaning, i.e., a meaning that is different from that understood by those skilled in the art, such special definition will be explicitly set forth in the specification as a definition, directly and unambiguously giving the special definition of the term or phrase.

[0084] Unless the content requires otherwise, throughout the following description, the word "include" and variations such as "comprising" are to be interpreted in an open, inclusive sense, that is, as in "including but not limited to."

[0085] Throughout this specification, reference to the terms "one embodiment," "an embodiment," "some embodiments," "examples," "specific examples," or "some examples" means that a particular feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0086] Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature identified with "first," "second," etc., may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0087] In the present invention, unless otherwise expressly specified or limited, terms such as "mounted," "connected," "coupled," "connected," and "fixed" should be understood broadly. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to direct connections, indirect connections through an intermediary, or internal communication between two components. Those skilled in the art will understand the specific meanings of these terms in the present invention based on specific circumstances.

[0088] In the following description of the drawings, like reference numerals refer to similar or identical elements throughout the drawings and their descriptions. Furthermore, the various features of the drawings discussed below are not necessarily drawn to scale. The dimensions of the various features and elements in the drawings may be enlarged or reduced to more clearly illustrate the embodiments of the present invention. For supplementary aspects of the teachings that can be directly identified from the drawings, reference is made to the relevant prior art. It should be noted that various modifications and variations in the form and details of the embodiments are possible without departing from the overall concept of the present invention.

[0089] Below, some embodiments of the hollow drill bit of the present invention are described in detail based on the accompanying drawings. In this specification, unless otherwise specified, the direction of the working rotation axis around which the hollow drill bit rotates during rotary drilling is the axial direction, the direction of rotation of each cutting tooth of the hollow drill bit during rotary drilling is the circumferential direction, the direction perpendicular to the axial direction of the hollow drill bit is the radial direction, the plane passing through the above-mentioned rotation axis is the radial plane, and the plane perpendicular to the above-mentioned rotation axis is the axial plane. In addition, for convenience of description, the side of the hollow drill bit closer to the workpiece to be machined can be defined as the distal side, and the side away from the workpiece to be machined (i.e., the side closer to the operator) can be defined as the proximal side.

[0090] As shown in FIG5 , a core drill bit 10 according to some embodiments of the present invention may include a drill head 11 located at a distal end and a shank 12 positioned proximal to the drill head 11. The drill head 11 and shank 12 may be integrally formed. The drill head 11 may include a plurality of cutting teeth 13 distributed about a rotational axis. Each cutting tooth 13 is configured to cooperate with each other in drilling a workpiece to remove an annular portion of material and cut a cylindrical core. Advantageously, the cutting teeth 13 may be evenly spaced about the working rotational axis of the core drill bit 10 to facilitate force balance during drilling, thereby extending the life of the core drill bit 10.

[0091] As shown in FIG5 , each cutting tooth 13 may include a plurality of cutting segments 14 arranged in sequence in the axial direction. These cutting segments 14 may be arranged so as to be arranged in sequence toward the radially outer side in the radial direction as they are arranged in sequence toward the proximal side in the axial direction, so as to form a stepped structure. These cutting segments 14 may extend in the circumferential direction between the proximal end and the distal end. The plurality of cutting segments 14 forming a stepped structure may increase the total length of each cutting segment 14 of the cutting tooth 13 in the axial direction, and the cutting tooth 13 may be cut into the workpiece in steps, so that the cutting force on the cutting tooth 13 may be effectively decomposed and dispersed. Accordingly, this helps to dissipate cutting heat and miniaturize the chip area, thereby facilitating smooth chip removal and reducing the generation of built-up edge, thereby extending the life of the hollow hole drill 10.

[0092] Furthermore, because the cutting segments 14 of the cutting teeth 13 that initially contact and penetrate the workpiece are smaller in the radial direction, the hollow drill bit 10 is facilitated to be inserted into the workpiece and positioned more accurately, reducing relative wobbling between the hollow drill bit 10 and the workpiece, thereby improving machining accuracy and quality. Similarly, when the hole in the workpiece is about to be completed, the cutting segments 14 of the cutting teeth 13 that last contact and penetrate the workpiece are smaller in the radial direction. This helps reduce relative wobbling between the hollow drill bit 10 and the workpiece, thereby reducing or preventing the formation of a "brim"-like structure when the lower surface of the workpiece is supported by a relatively hard object. For example, as shown in FIG9 , this allows the hollow drill bit 10 to be used to machine two or more stacked workpieces 7', with a small "brim" structure 9' formed only below the core 8' cut from the lowermost workpiece 7', or even no "brim" structure 9' at all.

[0093] The cutting section 14 may include an end section 15 located at the most distal end in the axial direction, and a circumferential step section 16 located proximal to the end section 15 in the axial direction. As shown in FIG5 , each circumferential step section 16 may be provided to extend substantially in the circumferential direction.

[0094] 7A to 7D and 8A to 8D , the first cutting teeth 20 and the second cutting teeth 30 of the core drill bit 10 according to some embodiments of the present invention are further described. The first cutting teeth 20 and the second cutting teeth 30 can be positioned at the positions shown in FIG. 6 in the circumferential direction, for example.

[0095] As shown in FIG7A , the core drill bit 10 may include a first cutting tooth 20. As shown in FIG7B , the first cutting tooth 20 may include an end section 21 and a plurality of circumferential step sections 22, the end section 21 may include an end cutting edge 28, and each circumferential step section 22 includes a primary cutting edge 23 and a secondary cutting edge 24.

[0096] As shown in Figure 7B, the end cutting edge 28 of the first cutting tooth 20 can be constructed as a one-piece type and thus include a single cutting edge segment. The main cutting edge 23 of each circumferential step segment 22 of the first cutting tooth 20 can also be constructed as a one-piece type and thus include a single main cutting edge segment. In other embodiments, the end cutting edge 28 of the first cutting tooth 20 can also be constructed as a multi-piece type and thus include a plurality of cutting edge segments, wherein a certain angle is formed between adjacent cutting edge segments of the plurality of cutting edge segments. In other embodiments not shown, the main cutting edge 23 of each circumferential step segment 22 of the first cutting tooth 20 can also be constructed as a multi-piece type and thus include a plurality of main cutting edge segments, wherein a certain angle is formed between adjacent cutting edge segments of the plurality of main cutting edge segments.

[0097] FIG7C shows a view of the first cutting tooth 20 according to some embodiments of the present invention as viewed along the MM direction in FIG6 . As shown in FIG7C , the orientation and size of the main cutting edge 23 and the secondary cutting edge 24 of each circumferential step section 22 of the first cutting tooth 20 can be configured to be identical to each other, so as to facilitate processing and manufacturing, and to contribute to uniform heat generation during the drilling process. For example, as shown in FIG7C , the heights h11, h12, h13, and h14 of the main cutting edge 23 of each circumferential step section 22 of the first cutting tooth 20 in the axial direction can be set to be identical to each other, and the heights h21, h22, h23, and h24 of the secondary cutting edge 24 in the axial direction can be set to be identical to each other. In addition, each main cutting edge 23 can have the same orientation, and each secondary cutting edge 24 can have the same orientation. Advantageously, the sum of the axial heights Lr1 of all cutting segments of the first cutting tooth 20 (i.e., including the end segment 21 and the plurality of circumferential step segments 22) is set to be no less than half the depth L0 (e.g., shown in FIG. 7A ) of the groove between the first cutting tooth 20 and any adjacent cutting tooth. For example, the sum of the heights Lr1 can be set to 60%, 80%, 90%, etc., of the depth L0.

[0098] In other embodiments not shown, the sizes and orientations of the main cutting edges 23 and the secondary cutting edges 24 of the various circumferential step sections 22 of the first cutting tooth 20 can be at least partially different from each other to accommodate various drilling requirements. For example, the main cutting edge 23 of each circumferential step section 22 of the first cutting tooth 20 can be configured as a single segment, and the orientations and / or sizes of the various main cutting edges 23 can be set to at least partially different from each other. For example, the number of segments of the main cutting edge 23 of each circumferential step section 22 of the first cutting tooth 20 can be set to at least partially different from each other. For example, the orientations and / or sizes of the secondary cutting edges 24 of each circumferential step section 22 of the first cutting tooth 20 can be set to at least partially different from each other.

[0099] FIG7D shows an end view of the first cutting tooth 20 according to some embodiments of the present invention, viewed along the axial direction of the core drill bit 10 in FIG5 , schematically illustrating the rake angle β1 of the end cutting edge 28 and the rake angles β11, β1i, and β1n of some of the main cutting edges 23 of the circumferential step segment 22. Here, i can be equal to 1, 2, 3, ..., n, and represents the sequence of the circumferential step segments, starting from the farthest circumferential step segment. Position "O" represents the position of the working rotation axis of the core drill bit 10. Advantageously, the aforementioned rake angles can be set between -30° and 30°. In some embodiments, the rake angle β1 of the end cutting edge 28 may be set to be equal to one or more of the rake angles β11 ... β1i ... β1n of the main cutting edge 23 of each circumferential step section 22, or may be set to be unequal to any of the rake angles β11 ... β1i ... β1n of the main cutting edge 23 of each circumferential step section 22. The rake angles β11 ... β1i ... β1n of each main cutting edge 23 may be set to be equal to one another, or at least partially unequal to one another.

[0100] FIG7D further illustrates, in projection on an axial plane, the radial thickness b1 of the end section 21 and the radial thicknesses b11, b12, b1i, and b1n of the plurality of circumferential step sections 22. Advantageously, the sum of the radial thickness b1 of the end section 21 and the radial thicknesses b11, b12, b1i, and b1n of the plurality of circumferential step sections 22 equals the radial wall thickness B of the hollow hole drill bit 10. Each of the aforementioned radial thicknesses can be set to between one-half and one-fifth of the radial wall thickness B of the hollow hole drill bit 10. Advantageously, in some embodiments, the radial thickness b1 of the end segment 21 can be set to be equal to one or more of the radial thicknesses b11, b12, ..., b1i, ..., b1n of each circumferential step segment 22, or can be set to be unequal to any of the radial thicknesses b11, b12, ..., b1i, ..., b1n of each circumferential step segment 22. The radial thicknesses b11, b12, ..., b1i, ..., b1n of each circumferential step segment 22 can be set to be equal to each other, or at least partially unequal to each other.

[0101] 8A to 8D illustrate the second cutting tooth 30 of the core drilling bit 10 according to some embodiments of the present invention. For example, as shown in FIG8A and FIG8B , the second cutting tooth 30 can be substantially similar in construction to the first cutting tooth 20, differing primarily in that the end cutting edge 38 of the end section 31 of the second cutting tooth 30 can be two-piece, and thus can include two cutting edge sections, wherein the two cutting edge sections form a certain angle. FIG8B also schematically illustrates the corresponding circumferential step section 32 of the second cutting tooth 30, as well as the corresponding primary cutting edge 33 and secondary cutting edge 34 of the circumferential step section 32.

[0102] It should be understood that, in addition to the first cutting teeth 20 and the second cutting teeth 30 described above, the core drilling bit 10 according to the present invention may further include cutting teeth 13 of one or more other shapes, which will not be described in detail herein.

[0103] In the hollow hole drill bit 10 shown in FIG5 , at least two of the plurality of cutting teeth 13 can be arranged so that their distal ends in the axial direction are located at different axial positions. During drilling, the cutting teeth 13 at different axial positions do not contact the workpiece simultaneously, but instead contact the workpiece and begin drilling sequentially. This helps distribute cutting forces and reduce cutting heat, thereby minimizing deformation of the cutting teeth 13 and extending the life of the hollow hole drill bit 10. The at least two cutting teeth 13 can be arranged adjacent to each other in the circumferential direction. Advantageously, the at least two adjacent cutting teeth 13 constitute a cutting tooth group, and the hollow hole drill bit 10 can include multiple cutting tooth groups arranged consecutively in the circumferential direction. This helps balance forces during rotation of the hollow hole drill bit 10, further extending the life of the hollow hole drill bit 10.

[0104] In other embodiments, the at least two cutting teeth 13 described above may alternatively or further be arranged so that their radially innermost ends are located at different radial positions. Such a hollow hole drill bit 10 can simultaneously remove material from different locations of a workpiece during drilling, which helps improve drilling efficiency, disperse cutting forces, and reduce cutting heat, thereby reducing deformation of the cutting teeth 13 and extending the life of the hollow hole drill bit 10.

[0105] As described above, the at least two cutting teeth 13 of the core drill bit 10 according to an embodiment of the present invention can be arranged to be offset relative to each other in one or both of the axial and radial directions. This helps reduce or avoid periodic vibrations of the core drill bit 10 during the drilling process, making the drilling process smoother and thus helping to improve machining accuracy and smoothness. Furthermore, this helps to disperse cutting forces, reduce cutting heat, and minimize deformation of the cutting teeth 13, thereby extending the life of the core drill bit 10.

[0106] The at least two cutting teeth 13 described above can have the same tooth shape for ease of manufacturing. Alternatively, the at least two cutting teeth 13 described above can also have different tooth shapes to help adapt to various drilling requirements, such as helping to further disperse cutting force, reduce cutting heat, etc.

[0107] For example, each cutting tooth 13 may have an end segment 15 with a different configuration. For example, in the first cutting tooth 20 and the second cutting tooth 30 described above, the end cutting edge 28 of the end segment 21 of the first cutting tooth 20 and the end cutting edge 38 of the end segment 31 of the second cutting tooth 30 have different numbers of cutting edge segments. Furthermore, the main deflection angles of the radially innermost cutting edge segments of the end segments 15 of each cutting tooth 13 may be different from one another. For example, FIG7C illustrates the main deflection angle λ1 of the radially innermost cutting edge segment of the end cutting edge 28 of the end segment 21 of the first cutting tooth 20 according to some embodiments of the present invention, while FIG8C illustrates the main deflection angle λ2 of the radially innermost cutting edge segment of the end cutting edge 38 of the end segment 31 of the second cutting tooth 30 according to some embodiments of the present invention. The main deflection angle λ1 and the main deflection angle λ2 may be unequal. For another example, when the end cutting edge of the end section 15 of each cutting tooth 13 is configured as a one-piece type, the lengths of the respective end cutting edges may be set to be different from each other.

[0108] However, it should be understood that the end segments 15 of the above-mentioned cutting teeth 13 can be constructed to be identical to each other in one or more of the number of cutting edge segments, the main rake angle of the cutting edge segment located at the innermost end in the radial direction, and the length of each end cutting edge when the end cutting edge of the end segment 15 of each cutting tooth 13 is constructed as a one-segment type.

[0109] For example, the respective cutting teeth 13 may have different numbers of circumferential step segments 16, and the sizes and orientations of the main cutting edges and secondary cutting edges of the circumferential step segments 16 of the same sequence between the respective cutting teeth 13, starting from the circumferential step segment 16 furthest to the side in the axial direction, may be at least partially different from each other. For example, for the respective circumferential step segments 16 of the same sequence, the main cutting edge of each circumferential step segment 16 may be constructed as a one-segment type, and the orientations and / or sizes of the main cutting edges of the respective circumferential step segments 16 may be at least partially different from each other. For another example, for the respective circumferential step segments 16 of the same sequence, the number of segments of the main cutting edges of the respective circumferential step segments 16 may be set to be at least partially different from each other. For another example, for the respective circumferential step segments 16 of the same sequence, the orientations and / or sizes of the secondary cutting edges of the respective circumferential step segments 16 may be set to be at least partially different from each other. For another example, for each circumferential step segment 16 in the same sequence, the main cutting edge of each circumferential step segment 16 may be constructed in one section, and the main cutting edge of each circumferential step segment 16 may have a different rake angle.

[0110] However, it should be understood that the above-mentioned cutting teeth 13 can be constructed to be identical to each other in one or more of the following aspects: the number of circumferential step segments 16, the number of main cutting edge segments of the circumferential step segments 16 in the same sequence starting from the farthest circumferential step segment 16 in the axial direction, the orientation and / or size of the main cutting edge of each circumferential step segment 16 when the main cutting edge is constructed in one section, the orientation and / or size of the secondary cutting edge, and the inclination angle of the main cutting edge of each circumferential step segment 16 when the main cutting edge is constructed in one section.

[0111] For example, as shown in Figures 7C and 8C, the height h11 of the main cutting edge 23 of the first circumferential step section 22 of the first cutting tooth 20, which is farthest from the axial direction, and the height h31 of the main cutting edge 33 of the first circumferential step section 32 of the second cutting tooth 30, which is farthest from the axial direction, may be equal or unequal. Similarly, the heights h12, h13, ..., h1i, h1n of the main cutting edges 23 of the second, third, ..., i, n circumferential step sections 22 of the first cutting tooth 20, which are farthest from the axial direction, and the heights h32, h33, ..., h3i, h3n of the main cutting edges 33 of the corresponding second, third, ..., i, n circumferential step sections 32 of the second cutting tooth 30, which are farthest from the axial direction, may be equal or unequal.

[0112] For example, as shown in Figures 7C and 8C, the height h21 of the secondary cutting edge 24 of the first circumferential step section 22 of the first cutting tooth 20, which is farthest from the axial direction, and the height h41 of the secondary cutting edge 34 of the first circumferential step section 32 of the second cutting tooth 30, which is farthest from the axial direction, may be equal or unequal. Similarly, the heights h22, h23, ..., h2i, h2n of the secondary cutting edges 24 of the second, third, ..., i, n circumferential step sections 22 of the first cutting tooth 20, which are farthest from the axial direction, and the heights h42, h43, ..., h4i, h4n of the secondary cutting edges 34 of the corresponding second, third, ..., i, n circumferential step sections 32 of the second cutting tooth 30, which are farthest from the axial direction, may be equal or unequal.

[0113] For example, as shown in Figures 7D and 8D, the rake angle β1 of the end cutting edge 28 of the first cutting tooth 20 and the rake angle β2 of the end cutting edge 38 of the second cutting tooth 30 may be equal or unequal. For example, the rake angles β11 ... β1i, β1n of each main cutting edge 23 of the first cutting tooth 20 starting from the first circumferential step section 22 on the farthest side in the axial direction and the corresponding rake angles β21 ... β2i, β2n of each main cutting edge 33 of the second cutting tooth 30 starting from the first circumferential step section 32 on the farthest side in the axial direction may be equal or unequal.

[0114] For example, FIG10 illustrates a core drilling bit 10' according to some embodiments of the present invention. As shown, the adjacent first and second cutting teeth 50, 60 of the core drilling bit 10' may constitute a cutting tooth set 70, and the core drilling bit 10' may include multiple cutting tooth sets 70 arranged sequentially in the circumferential direction. For example, the core drilling bit 10' may include three consecutive cutting tooth sets 70. The sizes and orientations of the primary and secondary cutting edges of the same circumferential step sections of the first and second cutting teeth 50, 60, starting from the circumferential step section furthest in the axial direction, may differ at least in part. For example, the primary and secondary cutting edges of the same circumferential step sections may have different lengths. The first and second cutting teeth 50, 60 may also have different numbers of circumferential step sections. For example, as shown in FIG10, the first cutting tooth 50 may have one circumferential step section, while the second cutting tooth 60 may have two circumferential step sections. Optionally, the axially distal ends of the first cutting tooth 50 and the second cutting tooth 60 may be located at different axial positions. Optionally, the radially inner ends of the first cutting tooth 50 and the second cutting tooth 60 may be located at different radial positions. During the drilling process of the hollow hole drill bit 10' constructed in this manner, the cutting edges of the various circumferential step sections of each cutting tooth only need to be responsible for partial cutting, thereby decomposing the cutting force, diverting the chips, reducing the cutting resistance of each cutting tooth, and lowering cutting heat. In addition, the hollow hole drill bit 10' constructed in this manner also helps to reduce the area of ​​the chips and makes them easier to discharge, thereby making the cutting process easier and helping to extend the life of the hollow hole drill bit 10'.

[0115] Although FIG5 shows an integrally formed drill head 11 and shank 12, in other embodiments, the core drilling drill 10 may include a drill head and shank formed separately, and the drill head and shank are detachably coupled together. For example, FIG11A and FIG11B show a drill head 11' for coupling to a corresponding shank (not shown).

[0116] In the embodiment shown in FIG5 , the drill head 11 of the core drill 10 can be integrally made of the same material. In other embodiments, such as the embodiment shown in FIG12 , the drill head 11 of the core drill 10 can also include a base portion 18 and a hard material portion 19 welded to the base portion 18 at the surface of each cutting tooth 13 facing the workpiece to be machined. The hard material portion 19 can be made of cemented carbide, for example.

[0117] Figure 13 shows a schematic diagram of a circumferential step section 42 on a first cutting tooth 41 and a circumferential step section 44 on a second cutting tooth 43 rotated to the same circumferential position, as viewed perpendicular to the axial direction, of a core drilling bit 40 according to some embodiments of the present invention. As shown in Figure 13 , the main cutting edges 45 and 46 of the two circumferential step sections can each be a one-segment curved cutting edge. The curved portion can have a radius of curvature R and can be radially concave inward toward the axis of rotation. The shaded areas in the figure represent the cutting zones.

[0118] Figure 14 illustrates a schematic diagram of a circumferential step section 52 on a first cutting tooth 51 and a circumferential step section 54 on a second cutting tooth 53 rotated to the same circumferential position, as viewed perpendicular to the axial direction, of a core drilling bit 50 according to some embodiments of the present invention. As shown in Figure 14 , the main cutting edges 55 and 56 of the two circumferential step sections may each be a one-segment curved cutting edge. The curved portion may have a radius of curvature R and may bulge outward in the radial direction away from the axis of rotation. The shaded areas in the figure represent the cutting zones.

[0119] Compared to a straight cutting edge, a curved cutting edge has a longer cutting edge length. Under the same cutting force, the cutting edge is subjected to less force per unit length, making the cutting process smoother and the cutting edge life longer. It should be understood that in other embodiments not shown, a hollow hole drill bit may also include cutting teeth with one or more outwardly protruding curved cutting edges and cutting teeth with one or more inwardly recessed curved cutting edges. The outwardly protruding curved cutting edges and the inwardly recessed curved cutting edges may be formed on the same cutting tooth or on different cutting teeth. It should be understood that a cutting tooth of a hollow hole drill bit may include multiple curved cutting edges, and advantageously, these curved cutting edges may have the same size and orientation. Figure 15 shows a schematic diagram of a circumferential step section 62 on a first cutting tooth 61 and a circumferential step section 64 on a second cutting tooth 63 rotated to the same circumferential position of a hollow hole drill bit 60 according to some embodiments of the present invention, when viewed along a direction perpendicular to the axial direction. As shown in Figure 15 , one of the two circumferentially stepped main cutting edges 65 and 66 is a one-segment curved cutting edge that is recessed radially inward toward the axis of rotation, while the other is a one-segment straight cutting edge. When viewed perpendicular to the axial direction, the straight cutting edge may form a specific angle θ with the axis of rotation. The shaded areas in the figure represent the respective cutting zones.

[0120] In the embodiment shown in FIG15 , the first cutting tooth 61 including the circumferential step section 62 of one of the above-mentioned embodiments may include only a plurality of inwardly recessed arcuate cutting edges as shown, and the second cutting tooth 63 including the circumferential step section 64 of the other of the above-mentioned embodiments may include only a plurality of linear cutting edges. Advantageously, the plurality of arcuate cutting edges may have the same size and orientation, and the plurality of linear cutting edges may have the same size and orientation. Advantageously, the first cutting tooth 61 and the second cutting tooth 62 may have the same number of circumferential step sections. Advantageously, the first cutting tooth 61 and the second cutting tooth 62 may be arranged adjacent to each other in the circumferential direction to form a cutting tooth group, and the hollow hole drill bit 60 may include a plurality of such cutting tooth groups.

[0121] As shown in FIG17 , a hollow hole drill bit 70 according to some embodiments of the present invention includes a first cutting tooth 71 comprising only an inwardly concave arcuate cutting edge, a second cutting tooth 72 comprising only a straight cutting edge, and the first cutting tooth 71 and the second cutting tooth 72 are arranged adjacent to each other in the circumferential direction to form a cutting tooth set. The hollow hole drill bit 70 may include a plurality of such cutting tooth sets.

[0122] Figure 16 illustrates a schematic diagram of a circumferential step section 82 on a first cutting tooth 81 and a circumferential step section 84 on a second cutting tooth 83 rotated to the same circumferential position, both of which are shown in a hollow core drill bit 80 according to some embodiments of the present invention, viewed perpendicularly to the axial direction. As shown in Figure 16 , one of the main cutting edges 85 and 86 of the two circumferential step sections is a one-piece curved cutting edge that protrudes radially outward away from the axis of rotation, while the other is a one-piece straight cutting edge. When viewed perpendicularly to the axial direction, the straight cutting edge may form a specific angle θ with the axis of rotation. The shaded areas in the figure represent the respective cutting zones.

[0123] In the embodiment shown in FIG16 , the first cutting tooth 81 including the circumferential step section 82 of one of the above-mentioned embodiments may include only a plurality of outwardly protruding arcuate cutting edges as shown, and the second cutting tooth 83 including the circumferential step section 84 of the other of the above-mentioned embodiments may include only a plurality of linear cutting edges. Advantageously, the plurality of arcuate cutting edges may have the same size and orientation, and the plurality of linear cutting edges may have the same size and orientation. Advantageously, the first cutting tooth 81 and the second cutting tooth 83 may have the same number of circumferential step sections. Advantageously, the first cutting tooth 81 and the second cutting tooth 83 may be arranged adjacent to each other in the circumferential direction to form a cutting tooth group, and the hollow hole drill bit 80 may include a plurality of such cutting tooth groups.

[0124] As can be seen from Figures 15 and 16 , the core drilling bit according to the present invention can include both cutting teeth with one or more curved cutting edges and cutting teeth with one or more straight cutting edges. It should be understood that the curved cutting edges and straight cutting edges can be formed on the same cutting tooth or on different cutting teeth. Furthermore, it should be understood that each of the curved cutting teeth can be outwardly convex or inwardly concave.

[0125] Optionally, the circumferential step segments on the two cutting teeth can be staggered in the radial direction by a certain distance so that the distal ends in the axial direction are located at different axial positions. Optionally, the circumferential step segments on the two cutting teeth can be staggered in the axial direction by a certain distance so that the inner ends in the radial direction are located at different radial positions. For example, Figures 13 and 14 schematically illustrate the misalignment of the circumferential step segments on the two cutting teeth in the radial direction and in the axial direction. By staggering the distal ends in the axial direction of different cutting teeth in the axial direction, and / or staggering the inner ends in the radial direction in the radial direction, it helps to decompose the cutting force, reduce the blade length of the cutting edge involved in cutting, divert the chips, reduce the cutting resistance of each cutting tooth, make the cutting process smoother, and reduce cutting heat.

[0126] In addition, as shown in Figures 13 to 16, the curved cutting edge can be constructed to be recessed radially inward toward the working axis of rotation, or to protrude radially outward away from the working axis. Compared to an outward-protruding curved cutting edge, the portion of the inward-recessed curved cutting edge near the secondary cutting edge has a smaller angle with the working axis of rotation, and therefore experiences correspondingly less resistance in the axial direction, allowing it to cut into the workpiece more smoothly. In addition, compared to an outward-protruding curved cutting edge, the portion of the inward-recessed curved cutting edge near the secondary cutting edge has a smaller primary rake angle, resulting in a smaller load per unit length and correspondingly less wear, thereby helping to improve durability. On the other hand, compared to an inward-recessed curved cutting edge, an outward-protruding curved cutting edge has greater strength, particularly at the tip, and is less prone to chipping.

[0127] As described above, the core drill bit 10 according to some embodiments of the present invention can decompose cutting forces during drilling, reducing cutting resistance and power, cutting heat, and deformation of the cutting teeth. It also helps to divert chips to reduce the area of ​​individual chips, thereby facilitating chip removal, preventing chip jamming, and reducing the tendency of chips to escape into the core. This helps extend the service life of the core drill bit 10 and improve machining quality. Furthermore, the core drill bit 10 according to embodiments of the present invention can achieve relatively accurate positioning and easy penetration during initial penetration into the workpiece, reducing the chance of damage and scrapping of the core drill bit 10 during use. The core drill bit 10 according to some embodiments of the present invention can also help reduce or avoid periodic vibration during drilling, resulting in a smoother drilling process and improved machining accuracy and smoothness. Furthermore, the core drill bit 10 according to the present invention can also help undercut the core to reduce the brim-like structure at the bottom of the core, thereby enabling continuous drilling through stacked workpieces.

[0128] The present invention may include any feature or feature combination or generalization disclosed herein, whether implicit or explicit, and is not limited to the scope of any limitation listed above. Any elements, features and / or structural arrangements described herein may be combined in any suitable manner.

[0129] The particular embodiments disclosed above are exemplary only, and it will be apparent to those skilled in the art having the benefit of the teachings herein that the present invention may be modified and practiced in different but equivalent manners. It is therefore apparent that changes and modifications may be made to the particular embodiments disclosed above, and all such variations are considered to fall within the scope and spirit of the present invention.

Claims

1. A hollow hole drill bit, characterized in that: The hollow hole drill bit comprises a drill head at a distal end of the hollow hole drill bit, the drill head having a plurality of cutting teeth distributed around a working rotation axis of the hollow hole drill bit, each cutting tooth comprising a plurality of cutting sections arranged sequentially in an axial direction, The plurality of cutting sections are sequentially arranged toward the proximal side in the axial direction and radially outward in the radial direction, thereby forming a step-like structure. Wherein, the multiple cutting segments include an end segment and one or more circumferential step segments, the end segment is located at the farthest end of the corresponding cutting tooth in the axial direction and includes an end cutting edge, the circumferential step segment is positioned proximal to the end segment in the axial direction, each circumferential step segment extends generally in the circumferential direction and includes a main cutting edge and a secondary cutting edge.

2. The hollow hole drill bit according to claim 1, characterized in that: The main cutting edge in the circumferential step section: - is of one-piece design and therefore comprises a single main cutting edge section; or - is of multi-segmented design and therefore comprises a plurality of main cutting edge segments, between which every two adjacent cutting edge segments form an angle.

3. The hollow hole drill bit according to claim 1, characterized in that: One or more of the cutting teeth respectively include a plurality of circumferential step sections, the orientation and size of the main cutting edges and the secondary cutting edges of the plurality of circumferential step sections being identical to each other.

4. The hollow hole drill bit according to claim 1, characterized in that: One or more of the cutting teeth respectively include a plurality of circumferential step sections, and the plurality of circumferential step sections satisfy one or more of the following: The main cutting edge of each circumferential step section is configured in one section, and the orientation and / or size of each main cutting edge are at least partially different from each other; The number of segments of the main cutting edges of the respective circumferential step sections is at least partially different from each other; The orientation and / or the size of the minor cutting edges of the individual circumferential step sections differ at least partially from one another.

5. The hollow hole drill bit according to any one of claims 1 to 4, characterized in that: The end cutting edge and the main cutting edge of each circumferential step section are both one-piece constructed, and the edge inclination angles of the end cutting edge and the main cutting edge of each circumferential step section are respectively between -30° and +30°.

6. The hollow hole drill bit according to any one of claims 1 to 4, characterized in that: In the axial plane, the thickness of the end section in the radial direction and the thickness of each circumferential step section in the radial direction are respectively one-half to one-fifth of the wall thickness of the hollow hole drill in the radial direction; and / or, The sum of the thickness of the end section in the radial direction and the thickness of each circumferential step section in the radial direction is equal to the wall thickness of the hollow hole drill in the radial direction.

7. The hollow hole drill bit according to any one of claims 1 to 4, characterized in that: The end cutting edge: - is of one-piece design and therefore comprises a single cutting edge segment; or - is of multi-segmented design and therefore comprises a plurality of cutting edge segments, between which two adjacent cutting edge segments each form an angle.

8. The hollow hole drill bit according to any one of claims 1 to 4, characterized in that: In the axial plane, the thickness of the end segment in the radial direction and the thickness of each circumferential step segment in the radial direction are equal to each other or at least partially unequal to each other; and / or The end cutting edge and the main cutting edge of each circumferential step section are both constructed in one section, and the edge inclination angle of the end cutting edge and the edge inclination angle of the main cutting edge in each circumferential step section are equal to or at least partially unequal to each other.

9. The hollow hole drill bit according to any one of claims 1 to 4, characterized in that: In the axial direction, the total length of the plurality of cutting sections of each cutting tooth is not less than half the depth of the groove between the cutting tooth and any adjacent cutting tooth.

10. The hollow hole drill bit according to claim 1, characterized in that: At least two cutting teeth among the plurality of cutting teeth have the same tooth shape.

11. The hollow hole drill bit according to claim 1, characterized in that: At least two cutting teeth among the plurality of cutting teeth have different tooth shapes and satisfy one or more of the following: The at least two cutting teeth have end sections of different configurations; The at least two cutting teeth have different numbers of circumferential step sections; The orientations and sizes of the main cutting edges and the secondary cutting edges of the circumferential step sections of the same order starting from the circumferential step section farthest in the axial direction of the at least two cutting teeth are at least partially different from each other.

12. The hollow hole drill bit according to claim 11, characterized in that: The at least two cutting teeth have end sections of different configurations and satisfy one or more of the following: The number of segments of the cutting edge sections of each end cutting edge is different; The main rake angles of the cutting edge sections located at the innermost ends in the radial direction of the respective end cutting edges are different; Each end cutting edge is configured as one-piece, and the lengths and / or cutting angles of the respective end cutting edges are different.

13. The hollow hole drill bit according to claim 11, characterized in that: The at least two cutting teeth have different numbers of circumferential step sections, and the orientations and sizes of the main cutting edges and the secondary cutting edges of the circumferential step sections of the at least two cutting teeth in the same sequence starting from the axially farthest circumferential step section are the same as each other.

14. The hollow hole drill bit according to claim 11, characterized in that: Each circumferential step section of the at least two cutting teeth in the same sequence starting from the circumferential step section farthest in the axial direction satisfies one or more of the following conditions: The main cutting edge of each circumferential step section is configured in one section, and the orientation and / or size of the main cutting edge of each circumferential step section are different from each other; The main cutting edge of each circumferential step section is constructed in one section, and the main cutting edges of each circumferential step section have different rake angles; The number of segments of the main cutting edge of each circumferential step section is different; The minor cutting edges of the individual circumferential step sections may be oriented and / or dimensioned differently.

15. The hollow hole drill bit according to any one of claims 10 to 14, characterized in that The at least two cutting teeth satisfy one or both of the following conditions: The distal ends in the axial direction are located at different axial positions; The inner ends in the radial direction are located at different radial positions.

16. The hollow hole drill bit according to claim 15, characterized in that: The at least two cutting teeth are arranged adjacent to each other in the circumferential direction, the at least two cutting teeth constitute a cutting tooth group, and the hollow hole drill bit includes a plurality of the cutting tooth groups arranged successively in the circumferential direction.

17. The hollow hole drill bit according to claim 16, characterized in that: The at least two cutting teeth include a first cutting tooth and a second cutting tooth, the first cutting tooth includes one circumferential step section, and the second cutting tooth includes two circumferential step sections.

18. The hollow hole drill bit according to any one of claims 1 to 4, characterized in that: The plurality of cutting teeth are evenly spaced and distributed around the working rotation axis of the core drilling bit.

19. The hollow hole drill bit according to claim 1, characterized in that: The hollow hole drill comprises at least one first cutting tooth, the end cutting edge of the first cutting tooth and the main cutting edge in each circumferential step section are both constructed as a one-piece type, and comprise at least one arcuate cutting edge, each of the arcuate cutting edges being recessed inwardly toward the working rotation axis or protruding outwardly away from the working rotation axis in the radial direction.

20. The hollow hole drill bit according to claim 19, characterized in that: The first cutting tooth includes a plurality of arc-shaped cutting edges, and the plurality of arc-shaped cutting edges have the same size and direction.

21. The hollow hole drill bit according to claim 19 or 20, characterized in that: The first cutting tooth only includes the arc-shaped cutting edge, and the hollow hole drill includes at least one second cutting tooth, the end cutting edge of the second cutting tooth and the main cutting edge in each circumferential step segment are both constructed as a one-piece type and only include a straight cutting edge. Preferably, the second cutting tooth includes multiple circumferential step segments, and the main cutting edges of each circumferential step segment have the same orientation and size.

22. The hollow hole drill bit according to claim 21, characterized in that The first cutting tooth and the second cutting tooth have the same number of circumferential step sections.

23. The hollow hole drill bit according to claim 21 or 22, characterized in that: The first cutting teeth and the second cutting teeth are arranged adjacent to each other in a circumferential direction to form a cutting tooth group, and the core opening drill bit includes a plurality of the cutting tooth groups.

24. The hollow hole drill bit according to any one of claims 21 to 23, characterized in that The first cutting tooth and the second cutting tooth satisfy one or both of the following conditions: The distal ends in the axial direction are located at different axial positions; The inner ends in the radial direction are located at different radial positions.

25. The hollow hole drill bit according to any one of claims 21 to 24, characterized in that The individual cutting teeth of the hollow hole drill are evenly spaced around the working rotation axis.

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