Drill inserts and drill bits for drilling hard materials

Abstract

A drill bit for drilling hard materials comprises a drill bit blade (1), the drill bit blade defining a rotation axis (O) and comprising: a first side edge (11) and a second side edge (12) located laterally opposite the rotation axis; a blade tip (A) laterally offset relative to the rotation axis; and a first cutting edge (21) and a second cutting edge (22) starting from the blade tip and terminating at the first and second side edges, respectively; wherein an angle bisector (X) between the first and second cutting edges is inclined at an angle (θ) relative to the rotation axis.

Description

Technical Field

[0001] The present application relates to a drill insert for drilling hard materials and a drill bit using the insert. Background Art

[0002] Many drill bits used for drilling hard materials have symmetrical drill blades. When the drill blades penetrate a workpiece, each cutting edge is subjected to pressure from the workpiece. Because the two cutting edges are symmetrical, they both contact the workpiece over their entire length, maintaining a large contact area between the two cutting edges and the workpiece. It has been found that the drilling speed of a drill bit is related to the contact pressure between the cutting edges and the workpiece. The larger the contact area between the cutting edges and the workpiece, the lower the pressure between them, which leads to a decrease in drilling speed. To increase the pressure between the cutting edges and the workpiece and thus increase the drilling speed, one can consider reducing the blade thickness or increasing the sharpness of the cutting edges. However, this will result in faster blade wear.

[0003] Figure 1 FIG. 1 shows an eccentric drill insert 1 according to the prior art, wherein the sharp point A between the two cutting edges 2a and 2b is offset by a lateral distance relative to the drill rotation axis O. The two cutting edges have the same inclination angle relative to the rotation axis O, so that the angle bisector X between the two cutting edges is parallel to the rotation axis O. When this drill insert 1 is drilling into a workpiece 3, only the cutting edge portion ( Figure 2 The insert (indicated by the bold line in the figure) bears pressure P from the workpiece and actually cuts the workpiece. This increases the pressure between the cutting edge and the workpiece, which can increase drilling speed. However, the workpiece pressure P on this insert only comes from one side relative to the rotation axis O. There is no workpiece pressure on the other side. Therefore, during drilling, the insert is subjected to a unilateral lateral component, which is detrimental to drilling accuracy and insert life.

[0004] Figure 2 Figure 1 shows another prior art eccentric drill insert 1, in which the cusp A between the two cutting edges 2a and 2b lies on the drill's rotational axis O. However, the two cutting edges are tilted at different angles relative to the rotational axis O, causing the angle bisector X between the two cutting edges to be tilted at a constant angle relative to the rotational axis O. When drilling into a workpiece, this insert also experiences pressure P from the workpiece on only one cutting edge (indicated by the bold line in the figure). Therefore, while this improves drilling speed, the insert is still subject to a single lateral component during drilling, which is detrimental to drilling accuracy and insert life. Summary of the Invention

[0005] The present application aims to provide an eccentric insert for drilling hard materials and a drill bit using the eccentric insert, which can improve drilling accuracy while ensuring drilling quality and insert life.

[0006] According to one aspect of the present application, there is provided a drill bit insert for drilling hard materials, which defines a rotation axis and comprises:

[0007] a first side edge and a second side edge located on first and second lateral sides of the rotation axis, respectively;

[0008] a blade tip laterally offset relative to the axis of rotation by a laterally offset distance; and

[0009] a first cutting edge and a second cutting edge originating at the blade tip and terminating at the first side edge and the second side edge, respectively;

[0010] The angle bisector between the first and second cutting edges is tilted at an angle relative to the rotation axis.

[0011] In one possible embodiment, the angle bisector between the first and second cutting edges is inclined relative to the rotation axis in a direction such that the intersection or the closest point of the angle bisector and the rotation axis is axially rearward relative to the blade tip.

[0012] In one possible embodiment, the axial positions of the end points of the first and second cutting edges on the first and second sides are different from each other.

[0013] In one possible embodiment, the blade tip is offset from the rotation axis toward the second lateral side, and the axial position of the end point of the second blade on the second side is further rearward than the axial position of the end point of the first blade on the first side.

[0014] In a possible embodiment, the lateral offset distance and the inclination angle are designed in combination so that: during drilling, the first and second cutting edges each have an effective cutting section participating in drilling the workpiece material and a non-cutting section not participating in drilling the workpiece material.

[0015] In one possible embodiment, the lateral offset distance and the tilt angle are further combined and designed to achieve one or more of the following optimization goals:

[0016] The difference between the length of the first blade and the length of the second blade is minimized, for example, less than a predetermined length difference limit;

[0017] During drilling, the difference between the effective cutting length of the first cutting edge and the effective cutting length of the second cutting edge is minimized, for example, less than a preset effective cutting length difference limit value;

[0018] During the drilling process, the degree to which the lateral components of the force borne by the first and second cutting edges from the workpiece material offset each other is maximized, for example, the lateral resultant force generated by the lateral components on both sides is less than a preset lateral force limit value.

[0019] In a feasible embodiment, the distance that the blade tip is laterally offset relative to the rotation axis is greater than 0 and smaller than the drilling radius of the drill bit blade, preferably smaller than half of the drilling radius, and in particular smaller than 1 / 3 of the drilling radius.

[0020] In a possible embodiment, the angle bisector between the first and second cutting edges is inclined relative to the rotation axis at an angle greater than 0 degrees and less than 45 degrees, preferably less than 30 degrees.

[0021] In a possible embodiment, at least one of the first blade and the second blade consists of two or more blade segments connected in sequence.

[0022] According to one aspect of the present application, there is provided a drill bit for drilling hard materials, comprising:

[0023] As previously described, the drill insert is mounted, for example welded, to the drill body.

[0024] According to the present application, the drill bit blade has a sharp point that is eccentric relative to the drill bit's rotational axis and a blade centerline (the blade angle bisector) that is inclined at an angle relative to the drill bit's rotational axis. During drilling, a portion of each blade contacts the workpiece on both sides of the drill bit's rotational axis. This reduces the actual contact area between the blade and the workpiece, increasing pressure and, consequently, drilling speed. Simultaneously, the workpiece exerts pressure on the blade on both sides of the drill bit's rotational axis, and the lateral components of these two pressures at least partially offset each other, improving drilling accuracy and blade life. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 and Figure 2 are schematic diagrams of some drill bit blades according to the prior art;

[0026] Figure 3 A front view of a drill bit blade according to one embodiment of the present application;

[0027] Figure 4 yes Figure 3 An enlarged bottom view of the drill bit blade in FIG;

[0028] Figure 5 is the definition Figure 3 Schematic diagram of the structural dimensions of the drill bit blade;

[0029] Figure 6 Shown Figure 3Two rotational positions of the drill bit blade in a state where the drill bit blade is not advanced axially;

[0030] Figure 7 Shown Figure 3 Two rotational positions of the drill bit blade in the state where the drill bit blade has advanced axially for a certain distance;

[0031] Figure 8 Shown Figure 3 The part of the drill bit blade that contacts the workpiece during drilling;

[0032] Figure 9 is a schematic diagram of a drill bit blade according to another embodiment of the present application;

[0033] Figure 10 Shown Figure 9 Two rotational positions of the drill bit blade in the state where the drill bit blade has advanced axially for a certain distance;

[0034] Figure 11 Shown Figure 9 The part of the drill bit blade that contacts the workpiece during drilling;

[0035] Figure 12 and Figure 13 is a schematic diagram of a drill bit blade according to other embodiments of the present application. DETAILED DESCRIPTION

[0036] Various possible embodiments of the drill insert and the drill bit according to the present application will be described below with reference to the accompanying drawings.

[0037] According to one embodiment of the present application, a drill bit insert 1 is used as a drill bit. Figures 3 to 8 The drill bit blade 1 is made of cemented carbide, is generally flat, and is welded to a drill bit body (not shown) for drilling hard materials such as ceramics, stone, metal, hardwood, etc.

[0038] like Figure 3 As shown, the drill bit blade 1 defines a first side 11 and a second side 12. Optionally, when the drill bit blade 1 is mounted on the drill bit body (not shown), the first and second sides 11, 12 are parallel to the drill bit rotation axis O (i.e., the rotation axis of the drill bit blade 1), and are located on both sides of the rotation axis O at equal lateral distances from the rotation axis O. Of course, the configuration of the first and second sides is not limited to this, and other conceivable configurations may also be applied to the present application. For example, the first and second sides may be parallel to each other, but not parallel to the rotation axis. For another example, the first and second sides may not be parallel to each other.

[0039] The drill insert 1 further defines a first cutting edge 21 located on a first lateral side and a second cutting edge 22 located on a second lateral side. The two cutting edges 21, 22 converge at a cusp A, which is the forward-most portion of the drill insert 1, and extend from the cusp A in opposite directions to respective end points B and C located on the sides 11, 12 of the drill insert 1. The cusp A is laterally offset from the drill bit's rotational axis O, about which the drill bit rotates during drilling. Furthermore, an angle bisector X between the two cutting edges 21, 22 is tilted at an angle θ relative to the rotational axis O. The tilt of the angle bisector X is such that the intersection (or closest point) of the angle bisector X with the rotational axis O is located axially rearward of the cusp A.

[0040] In this application, "front" refers to the direction in which the drill bit penetrates the workpiece, that is, the direction of the drill bit; "rear" refers to the opposite direction of the drill bit, that is, the direction toward the drill shank.

[0041] The size of the lateral offset of the tip A from the drill bit rotation axis O and the angle θ at which the inter-edge angle bisector X is inclined relative to the rotation axis O are designed in combination so that the end points of the two cutting edges 21, 22 have desired different axial positions, for example, so that the length difference between the two cutting edges 21, 22 is as small as possible (for example, less than a predetermined length difference limit value), or even no difference. Figure 3 In the illustrated embodiment, the sharp point A is located on the second side of the drill insert 1 , and the end point C of the second cutting edge 22 is located rearward in the axial direction relative to the end point B of the first cutting edge 21 .

[0042] It is understood that since the drill blade 1 has a certain thickness, the two cutting edges 21, 22 are usually gradually sharpened, that is, they change from the thickness of the drill blade 1 to the sharp edge. For some forms of the drill blade 1, the cutting edges of the two cutting edges 21, 22 are coplanar (for example, they are both located at the center of the blade thickness direction). Therefore, it is easy to measure the dimensions and angles related to them, or define the angle bisector between them, based on their coplanar cutting edges. However, in some cases, the two cutting edges 21, 22 are not coplanar. For example, as shown in Figure 4 The cutting edges of the first and second cutting edges 21, 22 (indicated by thick lines in the figure) are respectively located on opposite main surfaces of the drill blade 1, and the cusp A is formed at the transition portion between the cutting edges of the first and second cutting edges 21, 22. Since the first and second cutting edges 21, 22 themselves have such thickness, when discussing the dimensions, angles, positions, and angle bisectors between the two cutting edges 21, 22 in this application, the center line ( Figure 4 The center line between the middle endpoints B and C is used as the reference.

[0043] As shown in Figure 5 The first and second blades 21 and 22 have first and second transverse dimensions L1 and L2 in the transverse direction and first and second axial dimensions H1 and H2 in the axial direction, respectively. The first transverse dimension L1 is larger than the second transverse dimension L2, and the first axial dimension H1 is smaller than the second axial dimension H2.

[0044] For most embodiments applicable to the present application, the lateral distances between the end points B and C and the axis of rotation O are equal.

[0045] The dimension L3 of the lateral offset of the sharp point A from the rotation axis O is greater than 0 and smaller than the radius of the drill hole. In actual design, it is feasible that the dimension L3 of the lateral offset of the sharp point A from the rotation axis O is smaller than half or even 1 / 3 of the radius of the drill hole.

[0046] The tilt angle θ is set to be greater than 0 degrees. In actual design, it may be feasible to select the tilt angle θ to be less than 45 degrees, or even 30 degrees.

[0047] In order to explain the technical effect of the drill bit blade 1 described above, Figure 6 The figure shows two rotational positions of the drill insert 1, which differ by 180 degrees from each other. The solid line represents the first rotational position of the drill insert 1, and the dashed line represents the second rotational position of the drill insert 1 after rotating 180 degrees about the rotation axis O. There is no axial position change between these two rotational positions.

[0048] like Figure 6 As shown schematically, in the second rotational position, the first cutting edge 21 and the second cutting edge 22 face portions of the workpiece 3 where some material has already been removed by the second cutting edge 22 and the first cutting edge 21, respectively, in the first rotational position. Therefore, in the second rotational position, the second cutting edge 22 faces a void region (no material remaining) 31 and a solid region (still containing material, as indicated by the hatching) 32, while the first cutting edge 21 faces a void region (no material remaining) 33 and solid regions (still containing material, as indicated by the hatching) 34 and 32, respectively. Consequently, in the second rotational position, the first and second cutting edges only need to remove material from the solid regions 34 and 32 they face, respectively.

[0049] Figure 7 Two rotational positions are shown taking into account the axial advancement factor. Specifically, in the second rotational position, the drill blade 1 moves forward in the axial direction by a distance ΔH relative to the first rotational position. Figure 6 Compared with the situation shown in FIG, it can be seen that when there is an axial advancement distance, the solid areas 32 and 34 become larger and the hollow areas 31 and 33 become smaller. Based on this comparison, it can be deduced that the greater the axial forward thrust applied to the drill blade 1, the larger the area on the first and second cutting edges that can remove material, and therefore the greater the drilling speed.

[0050] As can be seen from the above description, by using a drill insert 1 having an inclined and asymmetrical cutting edge, at each moment in the drilling process, only the portion of each of the first and second cutting edges facing the solid area of the material is used to remove material, while the portions of the first and second cutting edges facing the void area do not remove material. The drill insert 1 of the present application does not use the full length of both cutting edges for drilling; only the effective cutting length of the two cutting edges (the portion of the two cutting edges facing the solid area of the material) actually removes material during drilling. Figure 8 The effective cutting sections of the two cutting edges are schematically shown in FIG (indicated by thick solid lines). Figure 8 In the figure, the effective cutting section of the first blade 21 includes section AD and section BE, and the effective cutting section of the second blade 22 is section AG. The section BF adjacent to the end point B on the first side 11 may also participate in the cutting. Points D and E are located on the first blade 21, point G is located on the second blade 22, and point F is located on the first side 11. They can be cut by Figure 6 and Figure 7 Taking into account the different advancement speeds of the drill bit during drilling, the specific positions of these points are not fixed.

[0051] In contrast to conventional drill inserts with symmetrical structures, the drill insert 1 of the present application uses less than the full length of its two cutting edges for drilling. Only the effective cutting length of the two cutting edges (the portion of each cutting edge facing the material's solid area) actually removes material during drilling. The effective cutting length of each cutting edge is less than its full length, increasing the pressure at the contact point between the cutting edge and the workpiece, thereby increasing drilling speed. Furthermore, there's no need to increase the sharpness of the cutting edge to increase drilling speed, thereby extending the life of the drill insert 1.

[0052] In addition, from Figure 8 It can be seen that the workpiece material acts on the drill blade 1 with pressures P1, P2, and P3, respectively, in the effective cutting sections AD and BE of the first cutting edge 21 and in the effective cutting section AG of the second cutting edge 22. The axial components of these pressures resist the axial thrust applied to the drill bit by the operator, while the radial (lateral) components of these pressures cancel each other out, thereby at least partially offsetting the radial (lateral) thrust components of the material acting on the drill blade 1, allowing the rotation axis of the drill blade 1 to remain undisturbed, thereby improving drilling accuracy.

[0053] When determining the lateral offset of the tip A from the drill bit's rotational axis O and the angle θ at which the inter-edge angle bisector X is inclined relative to the rotational axis O, in addition to minimizing the length difference between the two cutting edges 21, 22 as described above, another approach may be to minimize the difference in effective cutting length between the two cutting edges during normal drilling operations (e.g., less than a preset effective cutting length difference limit), thereby ensuring that the wear of the two cutting edges is as balanced as possible, which also helps extend the service life of the drill bit insert 1. Alternatively, another approach may be to minimize the mutual offset between the lateral components of the workpiece material applied to the two cutting edges during normal drilling operations (e.g., ensuring that the resultant lateral force generated by the lateral components on both sides is less than a preset lateral force limit).

[0054] Based on the principles described above, a variety of drill bit blade structures can be conceived. For example, in the embodiment described above, there is a straight cutting edge on each side of the tip A; however, according to the modification of the present application, at least one of the two cutting edges can be constructed in a multi-segment non-straight form.

[0055] For example, in Figure 9 In the illustrated embodiment, the drill insert 1 includes a first cutting edge 21 located on a first lateral side of the apex A and a second cutting edge located on a second lateral side of the apex A. The second cutting edge is composed of a first cutting segment 22a and a second cutting segment 22b that are angled relative to each other. The first cutting edge 21 originates at the apex A and terminates at a point B on the first side 11 of the drill insert 1. The first and second cutting segments 22a, 22b meet at a point G located on the second side of the apex A. The first cutting segment 22a originates at the apex A and terminates at point G, while the second cutting segment 22b originates at point G and terminates at point C on the second side 12 of the drill insert 1. In the axial direction, point G is located between the apex A and point B, and point C is located at a different axial position than point B. Furthermore, the axial and lateral positions of point G are combined to form a convex corner at point G.

[0056] In addition, the cusp A is laterally offset from the rotation axis O by a lateral distance, and the angle bisector X between the first cutting edge 21 and the first cutting edge segment 22 a of the second cutting edge is inclined at an angle θ relative to the rotation axis O. The inclination direction of the angle bisector X is such that the intersection point (or the closest point) of the angle bisector X with the rotation axis O is located axially rearward of the cusp A.

[0057] Figure 10 Schematic display Figure 9 Two rotational positions of the drill insert 1 are shown. Figure 10 In FIG. 1 , a first rotational position of the drill insert 1 is indicated by a solid line, and a second rotational position rotated 180 degrees about the rotation axis O and advanced a certain distance ΔH in the axial direction relative to the first rotational position is indicated by a dotted line.

[0058] like Figure 10 As schematically shown in the figure, in the second rotational position, the first and second blades each face a corresponding empty area (no material) and a solid area (still with material, as shown by the hatched lines), so that the first and second blades only need to cut off the material in the solid areas they face respectively in the second rotational position. Figure 9 The effective cutting sections of the cutting edges on both sides of the drill blade 1 are shown in FIG. Figure 11 The thick solid line represents the area of the cutting edge. As can be seen, the presence of active cutting segments on both cutting edges allows the radial (lateral) components of the material pressure on the two cutting edges to at least partially offset each other, thereby improving drilling accuracy. Furthermore, the length of the active cutting segment on each cutting edge is less than the full length of the cutting edge, thereby increasing drilling speed.

[0059] Previous reference Figures 3 to 8 The features of the embodiments described are also applicable to Figures 9 to 11 The implementation shown will not be described in detail here.

[0060] exist Figure 12 In the illustrated embodiment, the first blade located on the first lateral side of the tip A is composed of a first blade segment 21a and a second blade segment 21b, and the second blade located on the second lateral side of the tip A is composed of a first blade segment 22a and a second blade segment 22b. The first and second blade segments 21a and 21b meet at point J. The first and second blade segments 22a and 22b meet at point G. In the axial direction, the axial positions of the respective points A, B, C, G, and J are different from each other, and outward convex angles are formed at points G and J, respectively. The tip A is laterally offset from the rotation axis O by a lateral distance, and the angle bisector X between the first blade segment 21 and the first blade segment 22a of the second blade is inclined at an angle θ relative to the rotation axis O. The inclination direction of the angle bisector X is the same as in the previously described embodiment. Formerly referring to Figures 3 to 8 The features and technical effects of the embodiments described are also applicable to Figure 12 The implementation shown will not be described in detail here.

[0061] exist Figure 13In the embodiment shown, the first blade located on the first lateral side of the tip A is composed of a first blade segment 21a and a second blade segment 21b, and the second blade located on the second lateral side of the tip A is composed of a first blade segment 22a, a second blade segment 22b and a third blade segment 22c. The first and second blade segments 21a and 21b meet at point J. The first and second blade segments 22a and 22b meet at point G, and the second and third blade segments 22b and 22c meet at point K. In the axial direction, the axial positions of the respective points A, B, C, G, J, and K are different from each other, and convex angles are formed at points G, J, and K, respectively. The tip A is laterally offset from the rotation axis O by a lateral distance, and the angle bisector X between the first blade segment 21a of the first blade 21 and the first blade segment 22a of the second blade is inclined at an angle θ relative to the rotation axis O. The inclination direction of the angle bisector X is the same as in the embodiment described above. Formerly referring to Figures 3 to 8 The features and technical effects of the embodiments described are also applicable to Figure 13 The implementation shown will not be described in detail here.

[0062] Other possible implementations are also contemplated.

[0063] Generally speaking, the drill insert of the present application includes first and second cutting edges, both of which originate at a pointed point and terminate at laterally opposite sides of the drill insert. The pointed point is offset from the rotational axis of the drill insert, and the angle bisector between the first and second cutting edges is inclined at an angle relative to the rotational axis. The end points of the two cutting edges are located at different axial positions. Through this combination of features, during the drilling process, only a portion of each of the first and second cutting edges contacts and cuts the tool material. As a result, compared to symmetrical drill inserts, the pressure between the cutting edges and the material is increased, thereby improving drilling speed and efficiency.

[0064] Furthermore, there's no need to increase the sharpness of the cutting edge to increase drilling speed, making the cutting edge more wear-resistant. Furthermore, since both cutting edges experience wear during the drilling process, the wear rate is more even. These factors extend the life of the drill insert.

[0065] In addition, during the drilling process, the radial (lateral) components of the pressure from the material borne by the two cutting edges can offset each other to a certain extent, thereby preventing the drill bit from being dislocated due to the lateral thrust of the material, which improves the drilling accuracy.

[0066] Although the present application is described herein with reference to specific exemplary embodiments, the scope of the present application is not limited to the details shown, and various modifications may be made to these details without departing from the basic principles of the present application.

Claims

1. A drill insert for drilling hard materials, defining an axis of rotation and comprising: A first side edge (11) and a second side edge (12) located on first and second lateral sides of the rotation axis, respectively; a blade tip (A) laterally offset relative to said axis of rotation by a laterally offset distance; and a first cutting edge (21) and a second cutting edge (22) starting from the tip of the blade and terminating at the first side edge and the second side edge respectively; wherein the angle bisector (X) between the first and second cutting edges is inclined at an inclination angle (θ) relative to the rotation axis; In which, the lateral offset distance and the inclination angle are designed in combination so that: during the drilling process, the first and second cutting edges each have an effective cutting segment that participates in drilling the workpiece material and a non-cutting segment that does not participate in drilling the workpiece material, and the difference between the effective cutting segment length of the first cutting edge and the effective cutting segment length of the second cutting edge is less than a preset effective cutting length difference limit value.

2. The drill bit blade according to claim 1, wherein The angular bisector between the first and second cutting edges is inclined relative to the rotation axis in a direction such that the intersection or the closest point of the angular bisector with the rotation axis is axially rearward relative to the blade tip.

3. The drill bit blade according to claim 1, wherein The axial positions of the distal ends of the first and second cutting edges on the first and second sides are different from each other.

4. The drill bit blade according to claim 3, wherein: The blade tip is offset from the rotation axis toward the second lateral side, and the axial position of the end point (C) of the second blade on the second side is further rearward than the axial position of the end point (B) of the first blade on the first side.

5. The drill bit insert according to any one of claims 1 to 4, wherein The lateral offset distance and the tilt angle are further designed in combination to achieve one or more of the following optimization goals: minimizing the difference between the length of the first blade and the length of the second blade; During drilling, the difference between the effective cutting segment length of the first cutting edge and the effective cutting segment length of the second cutting edge is minimized; During drilling, the first cutting edge and the second cutting edge are subjected to a maximum degree of mutual cancellation of lateral components of the force from the workpiece material.

6. The drill bit insert according to any one of claims 1 to 4, wherein: The lateral offset distance and the inclination angle are further designed in combination to achieve: a difference between the length of the first blade and the length of the second blade is less than a preset length difference limit value.

7. The drill bit insert according to any one of claims 1 to 4, wherein: The lateral offset distance and the inclination angle are further designed in combination to achieve: during the drilling process, the lateral resultant force generated by the lateral components of the force from the workpiece material borne by the first cutting edge and the second cutting edge is less than a preset lateral force limit value.

8. The drill bit insert according to any one of claims 1 to 4, wherein The distance that the tip of the blade is laterally offset relative to the rotation axis is greater than 0 and less than the drilling radius of the drill blade.

9. The drill bit blade according to claim 8, wherein The tip of the insert is laterally offset relative to the axis of rotation by a distance less than half the radius of the drill hole.

10. The drill bit insert according to any one of claims 1 to 4, wherein The angle bisector between the first and second cutting edges is inclined relative to the rotation axis at an angle greater than 0 degrees and less than 45 degrees.

11. The drill bit blade according to claim 10, wherein The angle bisector between the first and second cutting edges is inclined at an angle less than 30 degrees relative to the rotation axis.

12. The drill bit insert according to any one of claims 1 to 4, wherein At least one of the first blade and the second blade is composed of two or more blade segments connected in sequence.

13. A drill bit for drilling hard materials, comprising: A drill bit insert as claimed in any one of claims 1 to 12, mounted to a drill bit body.

14. The drill bit for drilling hard materials according to claim 13, wherein The drill bit blades are welded to the drill bit body.

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