Drill tip

Abstract

The present invention relates to a drill tip for machining lightweight alloys, such as aluminum alloys, the drill tip comprising a body having a front end with an apex region (13), a central axis of rotation (8) extending rearward from the center of the apex region (13), and at least one cutting structure (10). Each cutting structure (10) comprises a first rake face (17), a first flank face (18), a cutting edge (11) at the intersection between the first rake face (17) and the first flank face (18), and a peripheral cutting corner (14). The cutting edge (11) extends radially outward from the apex region (13) to the cutting corner (14). The first flank (18) has a width (b) in a front view, the width (b) being a distance perpendicular to the cutting edge (11) and extending from the cutting edge (11) to a first flank edge (19) that rotates backward relative to the cutting edge (11). The body further has a nominal cutting radius (22) that is a radially outward distance from the rotational axis (8) to the cutting corner (14) and is at least 1 mm. The cutting edge (11) has a central portion (32) that extends radially outward from the apex region (13) to a radially outer end (23). The radially outer end (23) of the cutting edge central portion (32) has a radial distance to the rotational axis (8) that is at least 10% of the nominal cutting radius (22). The width (b) of the first flank along the cutting edge central portion (32) is at least 0.05 mm and at most 5% of the nominal cutting radius (22).

Description

Technical Field

[0001] The present invention relates to a drill tip for machining lightweight alloys such as aluminum alloys.

Background Art

[0002] Drills for machining lightweight alloys such as aluminum alloys are known. A known drill includes a drill tip that is a substantially conical front end of the drill, a shank at the rear end of the drill for attaching the drill to a machine spindle, and a straight or tapered portion therebetween. The drill tip is typically formed by the intersection of a rake face and a flank face, and includes two cutting edges extending radially outward from a central position adjacent to the rotational center axis. The chisel edge connects the two cutting edges across the rotational center axis. Chip grooves are provided in a straight or tapered segment to guide chips away from the cutting edges.

[0003] When drilling a workpiece made of a lightweight alloy such as an aluminum alloy, such known drills tend to have reduced centering characteristics and have a problem of reduced ability to machine according to strict tolerances.

Summary of the Invention

[0004] An object of the present invention is to provide a drill tip that reduces the drawbacks of the prior art and has improved centering characteristics.

[0005] This object is achieved by the present invention having the features of claim 1.

[0006] The drill tip of the present invention for machining lightweight alloys such as aluminum alloys comprises a body having a front end portion with a vertex region, a rotation center axis extending rearward from the center of the vertex region, and at least one cutting structure. Each cutting structure includes a first rake face, a first flank face, a cutting edge at the intersection between the first rake face and the first flank face, and a peripheral cutting corner. The cutting edge extends radially outward from the vertex region to the cutting corner. The first flank face has a width in a front view, and the width is the distance extending perpendicularly to the cutting edge and from the cutting edge to the edge of the first flank face that rotates and trails behind the cutting edge. The body further has a nominal cutting radius which is the radial distance from the rotation center axis to the cutting corner and is at least 1 mm. The cutting edge has a central portion extending radially outward from the vertex region to the radially outer end portion. The radially outer end portion of the central portion of the cutting edge has a radial distance to the rotation center axis of at least 10% of the nominal cutting radius. The width of the first flank face along the central portion of the cutting edge is at least 0.05 mm and at most 5% of the nominal cutting radius.

[0007] During operation, the drill tip rotates around the rotation center axis, and the cutting speed in the rotation direction varies from 0 at the center of the cutting edge to high speed at the outer peripheral end portion. As a result, chips are cut from the material machined along the peripheral portion of the cutting edge, while the machined material is plastically deformed mainly in the central portion. Therefore, clean chips are not formed at the center of the drill.

[0008] In prior art drills, when machining lightweight alloys such as aluminum alloys, the material from the machined object tends to adhere to the drill at the center where appropriate chips are not formed. Such accumulation of material occurs particularly on the flank face behind the cutting edge near the center of the drill. This has been found to be a major cause of reducing the centering characteristics of the drill.

[0009] Thanks to the drill tip of the present invention having a very narrow relief surface close to the center, the risk of material adhering to the relief surface is reduced. Nevertheless, if the material adheres, it tends to break from such a narrow surface. Therefore, it becomes difficult for the material to accumulate on the relief surface, thereby improving the centering characteristics of the drill tip and enabling machining of the object to be machined according to strict tolerances.

[0010] The drill tip according to the present invention is suitable for machining such as drilling of an object to be machined belonging to the object material group ISO-N according to the ISO classification standard of the object material. This group includes non-ferrous metals, such as lightweight alloys such as aluminum-based alloys.

[0011] The drill tip is made of, for example, one or more of cemented carbide, ceramic, cubic boron nitride, polycrystalline diamond, and / or cermet. Optionally, the drill tip is coated with a surface coating containing, for example, titanium nitride, titanium carbonitride, diamond-like carbon (DLC) and / or aluminum oxide.

[0012] The drill tip is configured to rotate around the rotation center axis in the cutting direction during machining of the object to be machined. When viewed in this rotation direction, the features of the drill tip lead or lag with respect to each other.

[0013] The cutting edge of each cutting structure of the drill body is formed at the intersection of the first rake face and the first relief face. Optionally, the cutting edge extends from or near the rotation center axis.

[0014] Preferably, the cutting edge has an edge radius of 6 μm or less, more preferably 4 μm or less. Such a sharp edge radius is advantageous for cutting the object to be machined of the target lightweight alloy material. Optionally, the edge radius is constant in the cross-section of the cutting edge, i.e., formed by a circular segment or varies to form an asymmetric edge. Optionally, the edge radius is constant or varies along the cutting edge. The edge radius can be measured, for example, using an optical 3D measuring device.

[0015] The cutting edge has an outer end at a cutting corner located around the body. The nominal cutting radius of the drill tip should be understood as the radius from the rotational center axis to the cutting corner. The drill tip has a nominal cutting radius of at least 1 mm. A drill tip with a smaller nominal cutting radius essentially has a smaller width of the first relief surface so that the machined material adheres thereto with difficulty.

[0016] Preferably, the nominal cutting radius of the drill tip is at most 20 mm. Generally, a larger drill tip is not very suitable for machining lightweight alloys such as aluminum alloys using state-of-the-art processes and machines.

[0017] The apex region of the body of the drill tip should be understood as a small region around the rotational center axis of the foremost tip of the drill tip. For example, in an embodiment where the cutting edge has a central end close to the rotational center axis, it is a small region at the center of the central end of the cutting edge, or in an embodiment having a chisel edge, it is a region limited by a circle with the full length of the chisel edge as the diameter.

[0018] In each cutting structure, the first rake surface is the surface portion closest to the cutting edge where the material removed from the object to be machined first slides. According to one embodiment, each cutting portion includes chips, and the first rake surface is part of the chip surface closest to the cutting edge. Accordingly, further rake surfaces can follow axially rearward of the first rake surface.

[0019] In each cutting structure, the first relief surface is a surface that rotates immediately after the cutting edge and faces forward. When viewed from the front end, in other words, as viewed in the direction of the rotational center axis toward the front end portion, the first relief surface has a width from the cutting edge to the edge of the first relief surface that rotates and moves rearward. Optionally, the first relief surface is curved or planar, and the first relief surface may be angled with respect to the plane with the rotational center axis as the normal. For example, the true width following the curvature of the curved first relief surface may deviate from the width when viewed from the front end.

[0020] The width of the first relief face along the central part of the cutting edge is at least 0.05 mm and a maximum of 5% of the nominal cutting radius. The smaller the width, the weaker the drill tip, and it may break when receiving cutting force during operation. With a larger width, the material from the workpiece to be machined, such as lightweight alloys like aluminum, begins to increasingly adhere to the relief face.

[0021] Optionally, the width of the first relief face along the central part of the cutting edge is constant or varies within a defined limit. For example, the width is constant over the main part, narrower the closer it is to the rotational central axis, and continuously widens along the outer part, aligning with the wider first relief face of the outer part of the cutting edge.

[0022] Preferably, when the nominal cutting radius is greater than 2 mm, the width of the first relief face along the central part of the cutting edge is a maximum of 3% of the nominal cutting radius. Thereby, the drill tip having such a larger nominal cutting radius has a first relief face with a width at the central part of the cutting edge, which is a smaller part of the nominal cutting radius. Due to the larger nominal cutting radius, the smaller part that is advantageous for adhesion also becomes strong enough during operation.

[0023] Preferably, when the nominal cutting radius is greater than 5 mm, the width of the first relief face along the central part of the cutting edge is at least 1% of the nominal cutting radius. Thereby, the drill tip having such a larger radius is advantageously stronger, and at the same time, the width of the first relief face at the central part of the cutting edge is small enough to sufficiently prevent the adhesion of the material from the workpiece to be machined during operation.

[0024] Preferably, the width of the first relief surface is 10 - 30% of the nominal cutting radius along the outer portion of the cutting edge, and the cutting edge extends radially inward from the cutting corner to the maximum of the central portion of the cutting edge up to the outer end. Since the cutting speed at the cutting edge of the drill tip is higher in the radially outer portion, appropriate chips are cut from the machined material in that area, and there is no concern about the adhesion of the material to the first relief surface. Therefore, advantageously, the width of the first relief surface in the radially outer portion of the cutting edge is instead optimized with respect to cutting performance and strength. A width of at least 10% of the nominal cutting radius achieves an increase in strength that can be expected for a particular operation. A width of up to 30% of the nominal cutting radius ensures smooth operation.

[0025] The central portion of the cutting edge extends radially outward from the apex region, or in other words, from the radially inner end near or on the rotational center axis. The radially outer end of the central portion of the cutting edge is located at a position having a radial distance to the rotational center axis of at least 10% of the nominal cutting radius. This is the region where the cutting speed is the lowest during operation and the machined material has the greatest tendency to adhere to the first relief surface. Preferably, the radially outer end of the central portion of the cutting edge has a radial distance to the rotational center axis of at least 35% of the nominal cutting radius.

[0026] According to one embodiment, the cutting edge includes a main cutting edge extending radially inward from the cutting corner and a second cutting edge extending radially outward from the apex region to the inner end of the main cutting edge. In a front view, the main cutting edge extends at an angle with respect to the second cutting edge, and the central portion of the cutting edge forms the second cutting edge. For example, in order to provide a more beneficial cutting shape, the main cutting edge is designed to have an extension portion extending inward from the cutting corner toward a position beside the rotational center axis, and the second cutting edge is designed to connect the main cutting edge to the apex region. For example, the second cutting edge mainly extends on the web of the drill tip body. Such an embodiment is advantageous in that the main cutting edge and its first relief surface can be optimized for chip removal machining, while the central portion of the cutting edge, i.e., the second cutting edge, is given the characteristics of the central portion of the cutting edge of the present invention to minimize adhesion.

[0027] According to an embodiment having a cutting edge central portion in the form of such a leading cutting edge and a second cutting edge that are angled with respect to each other, the leading cutting edge comprises a leading transition edge portion closest to the second cutting edge. Thereby, advantageously, the sharp corner of the cutting edge can be avoided.

[0028] Preferably, each cutting structure further comprises a front-facing front end face. The front end face extends radially outward from the apex region to the periphery of the body, connects to the edge of the first relief face, and rotates and trails along the edge of the first relief face. Optionally, the front end face comprises two or more relief faces that rotate and follow in sequence behind the first relief face. According to one embodiment, at least the radially outer portion of the edge of the first relief face is linear in a front view.

[0029] According to one embodiment, the front end face comprises a recess delimited by a recess surface, and the recess surface is adjacent to the edge of the first relief face at least along the cutting edge central portion. Thus, along the cutting edge central portion, the recess surface extends axially rearward from the edge of the first relief face. The recess rotates and trails along the edge of the first relief face. Providing a recess in the front end face is an efficient way to obtain the desired narrow width of the first relief face at the cutting edge central portion. The recess can be provided, for example, by grinding.

[0030] According to one embodiment, each cutting structure further comprises a coolant channel having a coolant opening and is at least partially located in the recess surface. Thereby, the coolant and / or lubricant supplied through the coolant channel can advantageously reach the cutting edge central portion by flowing over the recess. In addition to supplying the coolant and / or lubricant to the cutting edge central portion, the fluid flow contributes to reducing the material adhering to the first relief face from the workpiece. Preferably, at least a majority of the radially inner and axially forward quarter around the coolant opening is adjacent to the recess surface or, in other words, blocks the recess surface.

[0031] Preferably, the recess is a concave surface. The concave surface is efficient, for example, for manufacturing using a grinding wheel. According to one embodiment, the recess surface comprises a curved bottom surface extending axially rearward, a radially inner curved surface extending from the bottom surface to the apex region, and a radially outer curved surface extending from the bottom surface to the coolant opening. Preferably, in a front-end view, the longitudinal extension of the bottom surface is parallel to the central portion of the cutting edge. Preferably, in a side view, the bottom surface extends longitudinally in the direction of the central axis of rotation at least up to the axial position of the center of the coolant channel opening.

[0032] Optionally, the body comprises two, three or more cutting structures arranged rotationally symmetrically about the axis of rotation. However, embodiments having only one cutting structure are also contemplated.

[0033] According to a preferred embodiment, the body comprises two cutting structures and is arranged with 180° rotational symmetry about the axis of rotation. Optionally, the body comprises a chisel edge connecting the cutting edges of the two cutting structures across the apex region. According to one embodiment, each cutting edge is connected to the chisel edge via a small transitional edge. Thereby, advantageously, the sharp corners of the cutting edges can be avoided.

[0034] Preferably, the drill tip of the present invention is incorporated into a drill head, which is optionally an integral part of an exchangeable head connectable to a solid circular tool or a drill tool body. The drill tip then forms the front-end segment of a larger entity such as a solid tool such as an exchangeable head or a drill.

[0035] According to one embodiment, a solid tool in the form of a drill comprising the drill tip of the present invention further comprises a shank at the rear end for attaching the drill to a machine spindle and a straight or tapered segment between the drill tip and the shank. The chip groove is provided in the straight or tapered segment connecting to the drill tip so as to be able to guide the chips away from the cutting edge during operation. Optionally, the chip groove is spiral or straight.

[0036] Hereinafter, exemplary embodiments will be described in more detail with reference to the accompanying drawings.

Brief Description of the Drawings

[0037]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0038] All the figures are schematic diagrams and are not necessarily to scale. Generally, only the parts necessary to clarify each embodiment are shown, but other parts may be omitted or merely suggested. Unless otherwise indicated, the same reference numerals refer to the same parts in different figures.

[0039] Figs. 1 and 2 show a solid drill tool in the form of a twist drill with an embodiment of the drill tip 1 according to the present invention. The drill tip 1 according to the embodiment constitutes a substantially conical front segment 2 of the twist drill. The twist drill further comprises a shank 6 within a rear segment 4 for attaching the twist drill to a machine spindle. A straight segment 3 extends between the front segment 2 and the rear segment 4. A helical chip groove 5 is disposed within the straight segment 3, and the chip groove 5 continues axially within the drill tip 1. The twist drill is configured to rotate about the central axis 8 in the cutting direction 9 during machining of the workpiece, such as drilling an aluminum alloy. The features of the drill tip 1 and the twist drill are advanced or retarded relative to each other when viewed in the cutting direction 9.

[0040] Referring to Figs. 3 to 6, an embodiment of the drill tip 1 provided on the twist drill will be described.

[0041] The drill tip 1 comprises a body having a foremost tip in the form of a chisel edge 7. The central axis of rotation 8 extends rearward within the body from the center of the chisel edge 7.

[0042] The body further comprises two cutting structures 10 arranged with 180° rotational symmetry with respect to the central axis of rotation 8. Each cutting structure 10 comprises a cutting edge 11, and each cutting edge 11 is connected to respective ends of the chisel edge via a small transition edge 12. The central region around the central axis of rotation 8 comprises the chisel edge 7 and the small transition edge 12, forming an apex region 13.

[0043] Each cutting edge 11 extends from the radially outer end of the small transition edge 12 of the apex region 13 to a peripheral cutting corner 14. The radius from the central axis of rotation 8 to the cutting corner 14 forms the nominal cutting radius 22 of the drill tip 1 and the exemplary twist drill. The drill tip of the embodiment has a nominal cutting radius of 5 mm. In side view, each cutting edge 11 and the small transition edge 12 are substantially straight and form a point angle β of 140°. Other embodiments may have different cutting edge shapes, such as a cutting edge extending substantially in an axial plane.

[0044] Each cutting edge 11 is sharp with an edge radius of up to 4 μm.

[0045] Each cutting edge 11 includes a main cutting edge 15 extending radially inward from the cutting corner 14 and a central cutting edge portion (32) in the form of a second cutting edge 16. The second cutting edge 16 extends radially outward from the small transition edge 12 in the apex region and has a radially outer end 23 at the radially inner end of the main cutting edge 15. The main cutting edge 15 includes a main transition edge 24 closest to the radially outer end 23 of the second cutting edge 16. The radial distance from the rotation center axis 8 to the radially outer end 23 of the second cutting edge 16 is 2.07 mm, i.e., at least 35% of the nominal cutting radius 22, i.e., 1.75 mm.

[0046] In the front view of FIG. 3, the main cutting edge 15 extends at an angle with respect to the second cutting edge 16. The angle α between the line passing through the rotation center axis 8 and the radially outer end of the second cutting edge 16 and the line along the nominal cutting radius 22 passing through the rotation center axis 8 and the cutting corner 14 is 20 - 40°, and in the illustrated embodiment, the angle α is 24°.

[0047] In the front view of FIG. 3, the second cutting edge 16 is substantially straight, the main cutting edge 15 is concave for most of its length, and the main transition edge 24 is straight. The small transition edge 12 is concave. Other embodiments may have different cutting edge shapes.

[0048] Each cutting edge 11 is formed at the intersection of the first rake face 17 and the first flank face 18. One of the chip grooves 5 extends rearward from each cutting edge 11. The first rake face 17 is the portion of the chip groove face closest to the cutting edge 11.

[0049] As best seen in FIGS. 4 and 6, each second cutting edge 16 has a first rake face 17 in the form of a thin face 26. In the chisel edge 7 and the small transition edge 12, close to the rotation center axis 8, the thin face 26 has a concave portion. Axially below the main radially outer length of the second cutting edge 16, the thin face 26 has a planar portion.

[0050] In each cutting structure 10, the first relief surface 18 is a surface that rotates immediately after the cutting edge 11 and faces forward and rearward.

[0051] Each cutting structure 10 further includes a front end surface 20 facing forward. The front end surface 20 extends radially outward from the apex region 13 to the periphery of the main body, connects to the first relief surface 18, and rotates rearward with respect to the first relief surface. The first relief surface 18 has an edge 19 that moves rearward at the transition portion to the front end surface 20. The front end surface 20 includes a second relief surface 21, which rotates and follows behind the first relief surface 18. The rotating and rearward edge of the second relief surface 21 connects to the axially forward and rotationally front side surface 31 of the chip groove 5. The axially forward and rotationally front side surface 31 and the first rake surface 17 are partial surfaces of the same chip groove 5, but are associated with different ones of the cutting structures 10. The front end surface 20 follows a part of the periphery of the main body.

[0052] In the front view of FIG. 3, the first relief surface 18 has a width (b), which is measured perpendicular to the cutting edge 11. The width (b) is the distance from the cutting edge 11 to the edge 19 of the first relief surface.

[0053] The width (b) of the first relief surface along the second cutting edge 16 is greater than 0.06 mm, that is, greater than 0.05 mm and 1% of the nominal cutting radius 22, and less than 3% of the nominal cutting radius, that is, less than 0.15 mm.

[0054] The width (b) of the first relief surface along the outer portion of the cutting edge 11 is 0.53 mm, that is, more than 10% and less than 30% of the nominal cutting radius 22, that is, less than 1.5 mm. Specifically, this larger width (b) exists radially inward from the cutting corner 14 along most of the main cutting edge 15.

[0055] The width (b) of the first relief surface 18 is substantially constant along the second cutting edge 16, continuously widens along the transition portion 24 of the main cutting edge 15, and slightly changes along the outer portion of the main cutting edge 15 due to its concave curvature.

[0056] Each front end face 20 facing forward is provided with a recess 25 delimited by a recess surface, and is adjacent to the first relief face 18 along the small transition edge portion 12, along the second cutting edge 16, and along the radially central portion of the main cutting edge 15 including the main transition edge portion 24. On the radially outer side, the recess surface is adjacent to the second relief face 21 and the rotation-direction front face 31 axially forward of the chip groove 5.

[0057] Due to the recess 25, the portion of the first relief face 18 having the narrow width (b) of the present invention is located on the raised portion. The raised portion has a rotation-direction front face flank in the form of a thin face 26 that functions as a rake face 17 and a rotation-direction trailing flank in the form of the recess surface.

[0058] The recess surface is a concave surface including an axially rearwardly extending curved bottom surface 27, a radially inwardly curved surface 28 extending from the bottom surface 27 to the apex region 13, and a radially outwardly curved surface 29. See FIGS. 4 and 6.

[0059] In the front-end view of FIG. 3, the radially inwardly curved surface 28 extends across the apex region 13 along the second cutting edge 16 of both cutting structures 10. Specifically, the radially inwardly curved surface 28 of the first cutting structure is adjacent to the thin face 26 of the second cutting structure, and the radially inwardly curved surface 28 of the second cutting structure is adjacent to the thin face 26 of the first cutting structure. Due to the difference in the concave curvature between the radially inwardly curved surface 28 and the thin face 26, a common edge is formed at their intersection.

[0060] Each cutting structure 10 further includes a coolant channel having a coolant opening 30. The coolant opening 30 is partially located on the recess surface and partially located on the rotation-direction front face 31 of the chip groove 5. Accordingly, the coolant opening 30 is located on the radially outwardly curved surface 29 of the recess 25, and substantially radially inward and axially forward half around the coolant opening 30 is located on the recess surface.

[0061] As can be best understood from FIGS. 4 to 6, due to the recess 25 of the present invention, the coolant exiting through the coolant opening 30 is guided toward the second cutting edge 16. In combination with the narrow width of the present invention of the first flank 18 along the second cutting edge 16, the risk of material adhering to the flank 18 is significantly reduced.

Claims

1. A drill tip for machining lightweight alloys, wherein the drill tip comprises a body, and the body comprises: a front end portion having a vertex region (13); a rotation center axis (8) extending rearward from the center of the vertex region (13); at least one cutting structure (10); and has: Each cutting structure comprises: a first rake face (17); a first flank face (18); a cutting edge (11) at the intersection of the first rake face (17) and the first flank face (18); and a peripheral cutting corner (14); and is provided with: The cutting edge (11) extends radially outward from the vertex region (13) to the peripheral cutting corner (14); The first flank face (18) has a width (b) in a front-end view, and the width (b) is a distance that is perpendicular to the cutting edge (11) and extends from the cutting edge (11) to the edge (19) of the first flank face that rotates and trails behind the cutting edge (11); At the drill tip, the body further has a nominal cutting radius (22) that is the radial distance from the rotation center axis (8) to the peripheral cutting corner (14) and is at least 1 mm; The cutting edge (11) has a cutting-edge central portion (32) that extends radially outward from the vertex region (13) to a radially outer end portion (23); The radially outer end portion (23) of the cutting-edge central portion (32) has a radial distance to the rotation center axis (8) that is at least 10% of the nominal cutting radius (22); The width (b) of the first flank face along the cutting-edge central portion (32) is at least 0.05 mm and at most 5% of the nominal cutting radius (22); The radially outer end portion (23) of the cutting-edge central portion (32) has a radial distance to the rotation center axis (8) that is at least 35% of the nominal cutting radius (22); A drill tip, characterized in that.

2. When the nominal cutting radius (22) is greater than 2 mm, the width (b) of the first relief face along the central portion (32) of the cutting edge is at most 3% of the nominal cutting radius (22). The drill tip according to claim 1.

3. When the nominal cutting radius (22) is greater than 5 mm, the width (b) of the first relief face along the central portion (32) of the cutting edge is at least 1% of the nominal cutting radius (22). The drill tip according to claim 1 or 2.

4. The width (b) of the first relief face is 10 to 30% of the nominal cutting radius (22) along the outer portion of the cutting edge (11), and the outer portion of the cutting edge (11) extends radially inward from the peripheral cutting corner (14) to at most the radially outer end (23) of the central portion (32) of the cutting edge. The drill tip according to any one of claims 1 to 3.

5. The cutting edge (11) is A main cutting edge (15) extending radially inward from the peripheral cutting corner (14), and A second cutting edge (16) extending radially outward from the apex region (13) to the inner end of the main cutting edge and is provided with In a front view, the main cutting edge (15) extends at an angle with respect to the second cutting edge, The central portion (32) of the cutting edge forms the second cutting edge (16), The drill tip according to any one of claims 1 to 4.

6. The main cutting edge (15) extends at an angle with respect to the second cutting edge such that, in a front view, the angle (α) between the line passing through the rotational center axis (8) and the radially outer end (23) of the second cutting edge (16) and the line passing through the rotational center axis (8) and the peripheral cutting corner (14) is 20 to 40°. The drill tip according to claim 5.

7. The drill tip according to any one of claims 1 to 6, wherein the cross-section of the cutting edge (11) has an edge radius of at most 4 µm.

8. Each cutting structure (10) further comprises a front end face (20) facing forward, and the front end face (20) extends radially outward from the apex region (13) to the periphery of the body, connects to the edge (19) of the first relief face, rotates and moves rearward along the edge of the first relief face, the front end face (20) comprises a recess (25) delimited by a recess surface, the recess surface is adjacent to the edge (19) of the first relief face at least along the central portion (32) of the cutting edge, The drill tip according to any one of claims 1 to 7.

9. Each cutting structure (10) further comprises a coolant channel having a coolant opening (30) located at least partially within the recess surface, according to claim 8.

10. The drill tip according to claim 9, wherein when the periphery of the coolant opening (30) is divided into four, a quarter portion located radially inward and axially forward around the coolant opening (30) is adjacent to the recess surface.

11. The recess surface comprises a radially inner curved surface (28) extending from the apex region (13), a radially outer curved surface (29) extending from the coolant opening (30), and a curved bottom surface (27) located at least partially between the radially inner curved surface (28) and the radially outer curved surface (29) and extending axially rearward, and is a concave surface comprising The drill tip according to claim 9 or 10.

12. The body includes two cutting structures (10) arranged with 180° rotational symmetry around the rotation central axis (8), and the body includes a chisel edge (7) connecting the cutting edges (11) of the two cutting structures (10) across the apex region (13). The drill tip according to any one of claims 1 to 11.

13. The body includes two cutting structures (10) arranged with 180° rotational symmetry around the rotation central axis (8), and the body includes a chisel edge (7) connecting the cutting edges (11) of the two cutting structures (10) across the apex region (13), On the first rake face (17) of the first cutting structure of the two cutting structures (10), a first thin face (26) located at the central portion of the cutting edge (32) extends axially rearward from the chisel edge (7), On the first rake face (17) of the second cutting structure of the two cutting structures (10), a second thin face (26) located at the central portion of the cutting edge (32) extends axially rearward from the chisel edge (7), The radially inner curved portion surface (28) of the recess surface of the first cutting structure (10) is adjacent to the second thin face (26) via a common edge, The radially inner curved portion surface (28) of the recess surface of the second cutting structure (10) is adjacent to the first thin face (26) via a common edge. The drill tip according to claim 11.

14. A drill tool comprising the drill tip (1) according to any one of claims 1 to 13.

Images