drill

Abstract

The invention relates to a drill (2) comprising a drill tip (4), wherein the drill tip (4) comprises at least one main cutting edge (8) having a cutting corner (10), the main cutting edge (8) extending from the cutting corner to a center (12), wherein the drill tip (4) comprises at least one additional cutting edge (22) having an additional cutting corner (24), the additional cutting edge (22) extending from the additional cutting corner in the direction of the center (12), wherein the additional cutting edge (22) is formed only on an outer portion (26) of the drill tip (4) and is thus shorter than the main cutting edge (8), wherein the additional cutting corner (24) protrudes beyond the cutting corner (10).

Description

Technical Field

[0001] This invention relates to a drill. Background Technology

[0002] Drills are used to machine workpieces by drilling. For this purpose, a drill includes a tip with two main cutting edges, which, for example, remove chips from the workpiece as the drill rotates about its longitudinal axis. Consequently, the tip of the drill is sometimes subjected to heavy loads, leading to wear. This wear is typically greatest radially outward, and therefore damage usually occurs first there. The so-called cutting corners, which form the outer ends of the respective main cutting edges, are particularly affected. The lifespan of the drill is primarily limited by the wear of these cutting corners.

[0003] KR 101 000 863 B1 describes a drill that, in addition to two main cutting edges, includes two auxiliary cutting edges formed between the main cutting edges. The auxiliary cutting edges have a length corresponding to 0.4 times the drill radius. A portion of the torque is distributed from the main cutting edges to the auxiliary cutting edges, thereby potentially increasing the feed rate. Summary of the Invention

[0004] Objective of the present invention

[0005] With this in mind, the objective of this invention is to provide an improved drill with the longest possible service life.

[0006] According to the invention, the objective is achieved by a drill having the features described in claim 1. The appended claims concern advantageous configurations, further developments, and variations.

[0007] A drill is used to machine a workpiece by drilling. In general, a drill is a rotary tool that extends along a longitudinal axis and rotates about the longitudinal axis in the direction of rotation during operation.

[0008] The drill includes a drill tip formed on the front side of the drill and thus facing the workpiece during operation. The drill tip and the drill base body are formed as a single unit, i.e., integral, or a cutting insert formed as part of the drill base body.

[0009] The drill tip includes at least one main cutting edge with a cutting corner extending from the cutting corner to the center of the drill. The main cutting edge provides the first cutting action of the drill. The center is specifically a circular inner region of the drill and has a radius preferably corresponding to 0.1 to 0.3 times the total diameter of the drill. In the center, the drill tip preferably includes a chisel edge. For this purpose, a cutting edge thinning portion is appropriately formed in the center, such that the main cutting edge transitions into the chisel edge at the transition point to the center. On the other hand, on the outer cutting edge, i.e., at the cutting corner, the main cutting edge specifically abuts a secondary cutting edge that extends generally in the axial direction, for example, spirally around the longitudinal axis.

[0010] The drill tip also includes at least one additional cutting edge with an additional cutting bevel, which extends from the additional cutting bevel in a central direction. The additional cutting edge is formed only on the outer portion of the drill tip and is therefore shorter than the main cutting edge. The additional cutting edge provides an additional second cutting action. The configuration of the additional cutting edge is essentially the same as that of the main cutting edge, such that the additional cutting edge also extends generally from the cutting bevel toward the center on the outer edge of the drill tip, the cutting bevel being more specifically the additional cutting bevel in this case. However, compared to the main cutting edge, the additional cutting edge does not extend all the way to the center but terminates earlier, making the additional cutting edge shorter overall. This forms the outer portion of the drill tip, which surrounds the center and extends inward along a defined radius from the outer edge of the drill tip, i.e., from the outer surface of the drill. The outer portion is adjacent to the center, or another equally annular central segment is disposed between the center and the outer portion. Specifically, the center, the central segment, and the outer portion are arranged concentrically. The radius of the outer portion, i.e. its thickness, and therefore the length of the additional cutting edge, is preferably 0.1 to 0.5 times the total radius of the drill, particularly preferably 0.2 to 0.4 times, and thus approximately one-third of the total radius. The total radius corresponds to half of the total diameter.

[0011] Just as the main cutting edge and its cutting corner, the additional cutting edge, specifically its additional cutting corner, is also appropriately adjacent to the secondary cutting edge. This cutting edge also generally extends in a spiral shape in the axial direction, for example, around the longitudinal axis.

[0012] In the current configuration, the additional cutting angle protrudes beyond the main cutting angle. Specifically, this means that when viewed against the direction of rotation, the additional cutting angle is not completely covered by the main cutting angle and disappears behind it; instead, the additional cutting angle protrudes and thus forms an overhang relative to the main cutting angle. Roughly speaking, the additional cutting angle is configured to be larger than or protrude beyond the main cutting angle. Specifically, the additional cutting angle also partially or completely protrudes beyond the main cutting angle.

[0013] Specifically, a fundamental aspect of the invention lies in reducing the load on the main cutting edge, particularly the load on its cutting corner, by means of an additional cutting edge, especially by means of its additional cutting angle. Due to the additional cutting action on the outer portion, the load on the main cutting edge is correspondingly reduced in the radial direction on the outer side. Any type of load is distributed between the main cutting edge and the subsequent additional cutting edge. Since the load increases with increasing radius and is greatest at the outer edge, in the current case, the additional cutting edge is configured to be shorter than the main cutting edge to particularly reduce the load on the outer side and to achieve the highest possible stability of the drill tip facing inward. Wear on the main cutting edge is also more uniform, thereby increasing its service life.

[0014] In principle, aligning the additional cutting corner with the cutting corner—that is, making them the same size—is sufficient. Similarly, in this way, part of the load on the cutting corner is absorbed by the additional cutting corner. However, this can be further improved by configuring the additional cutting corner to protrude, i.e., the additional cutting corner has an outward extension relative to the cutting corner. Therefore, it is possible to distribute the load more precisely and particularly specifically between the cutting corner and the additional cutting corner. This distribution can now be optimally customized for a wide variety of applications.

[0015] In an advantageous configuration, the additional cutting bevel protrudes beyond the cutting bevel in the axial direction, i.e., along the longitudinal axis of the drill. Therefore, the drill is longer at the additional cutting bevel than at the cutting bevel itself. This results in a length difference, preferably from 0.05 mm to 2 mm. Consequently, the additional cutting bevel protrudes axially beyond this length difference, also known as axial overhang. In one configuration, the axial overhang is constant along the additional cutting bevel, while in another configuration it varies.

[0016] Specifically, the axial extension causes the additional cutting corner to protrude axially relative to the cutting corner. However, generally speaking, the additional cutting corner does not protrude beyond the chisel edge of the drill bit in the axial direction, but rather preferably shifts rearward relative to the chisel edge, i.e., offset rearward by a defined distance in the axial direction. Strictly viewed from front to back in the axial direction, the additional cutting corner is positioned between the chisel edge and the cutting corner. Therefore, in the axial direction, specifically, the chisel edge forms the foremost point of the drill bit.

[0017] In another advantageous configuration, the additional cutting corner protrudes beyond the cutting corner in the radial direction, i.e., in the direction perpendicular to the longitudinal axis. Similar to the length difference in the axial direction, the drill has a larger radius at the additional cutting corner compared to the cutting corner. This results in a radius difference preferably ranging from 0.05 mm to 2 mm. Therefore, the additional cutting corner correspondingly protrudes beyond this radius difference in the radial direction, which is also referred to as radial extension. In one configuration, the radial extension is constant along the additional cutting corner, while in another configuration it varies.

[0018] Advantageously, the radial and axial extensions can be combined with each other, thus causing the additional cutting corner to protrude beyond the cutting corner in both the radial and axial directions.

[0019] The cutting corner is generally a component of the main cutting edge and forms the end of the main cutting edge radially outward. Similarly, the additional cutting corner is generally a component of the additional cutting edge and forms the end of the additional cutting edge radially outward. In principle, there are several suitable configurations for both the cutting corner and the additional cutting corner, which are selected based on the specific application.

[0020] In a suitable configuration, the additional cutting corner is rounded. Therefore, the additional cutting corner itself is not pointed, but actually forms a corner cutting edge, which is thus the outer portion of the additional cutting edge. In other words, the additional cutting edge is identical to the corner cutting edge such that the additional cutting edge is confined to a rounded additional cutting corner, or the corner cutting edge is adjacent to the interior via an inner portion cutting edge, which then forms the additional cutting edge as a whole, together with the corner cutting edge. The specific design depends on how far the additional cutting edge extends towards the center and how long the corner cutting edge is, i.e., how rounded the additional cutting corner is. Preferably, the cutting corner is rounded because it has a corner radius of 0.4 mm to 5 mm. Specifically, the corner radius is measured in an imaginary plane that extends parallel to or at a small angle of at most 20° to the longitudinal axis. The transition between the inner and outer portions of the cutting edge is suitably continuous, i.e., rounded, and specifically, not pointed or discontinuous. The transition from the corner cutting edge to the secondary cutting edge is also continuous, or a corner is formed here.

[0021] Alternatively, in a suitable configuration, the additional cutting corner is sharp. Here, the additional cutting edge extends primarily radially outward and meets the secondary cutting edge at a defined angle, for example, exceeding 90° to 120°. In a sharp configuration, a corner or point is formed at the end of the additional cutting edge via an additional cutting corner.

[0022] For machining abrasive materials such as cast iron, the additional cutting angle of a circle is particularly advantageous. Due to the rounded design, the load on the outer cutting edge is distributed over the longitudinally extending region, i.e., the outer portion of the cutting edge. In contrast, with a pointed configuration, the load on the outer cutting edge is selectively directed to the pointed additional cutting angle. Then, similarly, the pointed configuration is particularly suitable for machining soft and less abrasive materials such as aluminum.

[0023] Just like the additional cutting corner, the cutting corner of the main cutting edge is preferably rounded or pointed, depending on the application. Suitablely, both the cutting corner and the additional cutting corner are rounded or both are pointed. There may also be mixed configurations, where the cutting corner is rounded and the additional cutting corner is pointed, or vice versa, but at least as long as the additional cutting corner still protrudes beyond the cutting corner.

[0024] A particularly preferred design is one in which the cutting corner and the additional cutting corner are configured to have the same shape. This means that the cutting corner and the additional cutting corner each have a contour, with the same shape but different dimensions, such that the additional cutting corner is an enlarged version of the cutting corner and therefore protrudes accordingly. Thus, the additional cutting corner is generated by a corresponding scaling of the cutting corner without deformation. Consequently, the protrusion of the additional cutting corner is particularly consistent.

[0025] Preferably, the angle enclosed by the cutting corner and the additional cutting corner is less than 90°. An angle in the range of 20° to 80° is particularly preferred. Specifically, the angle is measured in the direction of rotation, i.e., in a plane perpendicular to the longitudinal axis. This is based on the observation that the load distribution between the cutting corner and the additional cutting corner can be adjusted not only by the overhang of the additional cutting corner but also by the angle. This is because the angle determines how much of the workpiece machining is done by the additional cutting corner and how much by the cutting corner during one complete rotation of the drill. The smaller the angle, the smaller the load on the additional cutting corner and the larger the load on the cutting corner.

[0026] Combining the overhang amount creates a two-dimensional parameter space where the load distribution is adjusted according to two parameters: angle and overhang amount. Therefore, if the angle increases while the overhang amount decreases, or vice versa, the load can remain constant. Thus, for a given overhang amount or angle, the distribution can be changed by adjusting the angle or overhang amount—that is, the corresponding other parameter. For example, manufacturing-related limitations regarding the overhang amount or angle can thus be advantageously overcome by using the other parameter.

[0027] In an advantageous configuration, the drill includes multiple main cutting edges, each with a cutting corner, followed by additional cutting corners that enclose an angle with the main cutting edges, thus forming multiple angles. Preferably, these angles have different sizes. In other words, with multiple main cutting edges and associated additional cutting corners, a corresponding number of angles are also formed. These angles are appropriately chosen to have different sizes to reduce vibration, and specifically to reduce so-called chattering of the workpiece or drill during machining. Choosing different angles breaks the original symmetry of the drill, thus advantageously altering the vibration characteristics of the system consisting of the drill and the workpiece during machining.

[0028] Specifically, the main cutting edge is preceded by a chip removal groove, through which chips detached by the main cutting edge are carried away axially from the drill tip toward the rear. Specifically, the chip removal groove extends along the entire length of the main cutting edge and then terminates at the center. Therefore, the center also forms the drill core, into which the chip removal groove extends, but does not enter, thus giving the chip removal groove a depth corresponding to the difference between the total radius of the drill and the core radius.

[0029] Preferably, the drill includes a chip chute before the additional cutting corner for receiving chips from the additional cutting corner. Therefore, in addition to the chip chute to the main cutting edge, the drill also includes another chip chute to the additional cutting edge. Chips generated by the additional cutting corner, and typically by the additional cutting edge, are carried away through this additional chip chute. These chips typically have a different shape than the chips on the main cutting edge. Because the additional cutting edge is shorter, shorter chips are typically generated here as well. The chip chute to the additional cutting edge is also suitably shallower than the chip chute to the main cutting edge, and therefore protrudes less into the drill's base body. Specifically, this reserves space for an optional coolant channel, which, viewed in the direction of rotation, is suitably positioned between the main cutting edge and the chip chute to the additional cutting edge. Preferably, both chip chute types are helical.

[0030] In an advantageous configuration, the primary cutting edge abuts a free surface that slopes downward in the direction of the additional cutting corner and transitions to a secondary free surface that slopes upward in the direction of the additional cutting corner. Specifically, the free surface behind the primary cutting edge forms a back angle. Due to the free surface and the secondary free surface, the drill tip includes a recess on one side positioned between the primary cutting edge and the center, and on the other side positioned between the additional cutting edge and the additional cutting corner, preventing the drill tip from rubbing against the workpiece during operation.

[0031] Preferably, the additional cutting edge terminates at the secondary free surface, specifically, the secondary free surface already described above. Therefore, the secondary free surface is positioned between the center and the additional cutting edge. The length of the additional cutting edge is limited by the secondary free surface.

[0032] The free surface leading to the main cutting edge is defined in the front by the same main cutting edge. In the rear, specifically, the free surface in the center is defined by the edge thinning section, through which the chisel edge is formed. In the rear facing the outer cutting edge, specifically, the free surface is defined by the chip groove leading to the additional cutting edge. The secondary free surface is disposed between the edge thinning section and the chip groove. This then also defines the free surface in the rear. The drill tip continues to slope downward from the free surface into the chip groove connecting to the additional cutting edge and into the edge thinning section, while the secondary free surface, in turn, creates an upward slope, causing the additional cutting corner to protrude accordingly. In the rear, the secondary free surface preferably transitions into the edge thinning section, and in the front, it transitions into the chip groove connecting to the additional cutting edge. Specifically, the secondary free surface is configured to be substantially similar to the edge thinning section, i.e., such that the additional cutting edge is formed on the end side through the secondary free surface.

[0033] In principle, a drill may include multiple main cutting edges, with one, more, or all of the main cutting edges followed by one or more additional cutting edges. A particularly preferred configuration is that the drill includes exactly two main cutting edges, each with a cutting bend, followed by exactly one additional cutting bend, or more precisely, one additional cutting edge with an additional cutting edge. Drills with two main cutting edges are also called double-edged drills and exhibit particularly good stability during operation, especially centering. This stability is hardly or not affected at all by the additional, but shorter, cutting edges. In fact, the additional cutting edges make the load and wear of the main cutting edges, especially their cutting bends, more uniform. Attached Figure Description

[0034] The design examples of the invention are explained in more detail below with the aid of the accompanying drawings. The drawings schematically illustrate:

[0035] Figure 1 Front view of the drill.

[0036] Figure 2 Perspective view Figure 1 Details of the drill

[0037] Figure 3 Side view Figure 1 Details of the drill

[0038] Figure 4 Presenting different side views Figure 1 Details of the drill. Detailed Implementation

[0039] Figure 1-4 A design example of a drill 2 for machining a workpiece (not depicted) by means of drilling is shown. In general, the drill 2 is a rotary tool extending along a longitudinal axis L, which rotates in the rotational direction U about the longitudinal axis during operation. Figure 1 The front view of drill 2 is shown. Figure 2 A perspective view is shown, and Figure 3 and 4 The corresponding side view is shown, thus Figure 3 The view is from Figure 4 The view in the diagram is rotated 90° in the rotational direction U. The drill 2 includes a drill tip 4 formed on the front side of the drill 2 and thus facing the workpiece during operation. In the design example shown, the drill tip 4 and the base body 6 of the drill 2 are formed as a single, integral piece. In an alternative not depicted, the drill tip 4 is configured as a cutting insert for the base body 6 of the drill 2.

[0040] The drill tip 4 includes at least one main cutting edge 8 having a cutting corner 10, the main cutting edge 8 extending from the cutting corner to the center 12 of the drill 2. One of the two main cutting edges 8 is in Figure 1 The center is highlighted with thick lines. The main cutting edge 8 provides the first cutting action of the drill. The center has a radius R1, which here corresponds to 0.1 to 0.3 times the total diameter Dg of the drill 2. The total diameter Dg corresponds to twice the total radius Rg. In the center 12, the drill tip 4 also includes a chisel edge 14. For this purpose, a thinning portion 16 is formed so that the main cutting edge 8 transitions into the chisel edge 14 at the transition to the center 12. On the other hand, on the outer cutting edge 18, that is, at the cutting corner 10, the main cutting edge 8 is adjacent to a secondary cutting edge 20 that extends generally in the axial direction A, for example, spirally around the longitudinal axis L.

[0041] The drill tip 4 also includes at least one additional cutting edge 22 having an additional cutting corner 24, the additional cutting edge 22 extending from the additional cutting corner in the direction of the center 12. One of the two additional cutting edges 22 is in Figure 1The center is also highlighted with thick lines. The additional cutting edge 22 is formed only on the outer portion 26 of the drill tip 4, and is therefore shorter than the main cutting edge 8. The additional cutting edge 22 provides an additional second cutting action. The configuration of the additional cutting edge 22 is essentially the same as that of the main cutting edge 8, such that the additional cutting edge 22 also extends generally from the cutting corner toward the center 12 on the outer cutting edge 18 of the drill tip 4, the cutting corner being more specifically, in this case, the additional cutting corner 24. However, compared to the main cutting edge 8, the additional cutting edge 22 does not extend all the way to the center 12, but terminates earlier, making the additional cutting edge 22 shorter overall. This forms the outer portion 26 of the drill tip 4, which surrounds the center 12 and extends inwardly along the defined radius R2 from the outer cutting edge 18, i.e., from the outer surface 28 of the drill 2. The outer portion 26 is adjacent to the center 12, or as in… Figure 1 As can be seen, another annular central segment 30 is positioned between the center 12 and the outer portion 26. Here, the center 12, the central segment 30, and the outer portion 26 are arranged concentrically. The radius R2 of the outer portion 26, that is, the thickness of the outer portion, and therefore the length of the additional cutting edge 22, is 0.1 to 0.5 times the total radius Rg.

[0042] Just as the main cutting edge 8 and its cutting corner 10, the additional cutting edge 22, specifically its additional cutting corner 24, is adjacent to the secondary cutting edge 20. This secondary cutting edge here also generally extends in a spiral shape around the longitudinal axis in the axial direction A. The secondary cutting edge 20 can be specifically seen in… Figure 2 middle.

[0043] In the current configuration, the additional cutting corner 24 protrudes beyond the cutting corner 10. This means that when the main cutting edge 8 is viewed in the direction of rotation U, the additional cutting corner 24 is not completely covered by the cutting corner 10 and disappears behind it; instead, the additional cutting corner 24 protrudes and thus forms an extension 32, 34 along the cutting corner 10 relative to it. Here, the additional cutting edge 22 also partially or completely protrudes beyond the main cutting edge 10.

[0044] In the configuration shown, the additional cutting bend 24 protrudes beyond the cutting bend 10 in the axial direction A, i.e., along the longitudinal axis L. Therefore, the drill 2 is longer at the additional cutting bend 24 than at the cutting bend 10. This results in a length difference, ranging from 0.05 mm to 2 mm, and is also referred to as axial extension 32. Furthermore, in the radial direction R, i.e., perpendicular to the longitudinal axis L, the additional cutting bend 24 also protrudes beyond the cutting bend 10. Similar to the length difference in the axial direction A, the drill 2 has a larger radius Rg at the additional cutting bend 24 than at the cutting bend 10. This results in a radius difference, ranging from 0.05 mm to 2 mm, and is also referred to as radial extension 34. Figure 2 and 4In the middle, the two extensions 32 and 34 are indicated by the dashed line below the additional cutting edge 22, and the radius and length difference are indicated by two corresponding arrows.

[0045] The radial extension 34 and the axial extension 32 can also be achieved independently of each other, such that the additional cutting corner 24 subsequently protrudes beyond the cutting corner 10 in the radial direction R or in the axial direction A.

[0046] Cutting corner 10 is generally a component of the main cutting edge 8, and forms the end of the main cutting edge outward in the radial direction R. Similarly, additional cutting corner 24 is also generally a component of the additional cutting edge 22, and forms the end of the additional cutting edge outward in the radial direction R. In principle, there are several suitable configurations for cutting corner 10 and additional cutting corner 24.

[0047] For example, in the design example shown, the additional cutting corner 24 is rounded and forms itself a corner cutting edge. Here, the rounded additional cutting corner 24 is largely the same as the additional cutting edge 22. Figure 4 As shown, the additional cutting corner 24 is the outer portion of the additional cutting edge 22. This outer portion of the cutting edge is adjacent to the interior via an inner portion of the cutting edge 36, which then forms the additional cutting edge 22 together with the corner cutting edge. For example, in the illustrated design example, the inner portion of the cutting edge 36 is a straight continuation of the outer portion of the circular cutting edge. On the other hand, in the undepicted variant, the additional cutting corner 24 of the circle corresponds exactly to the additional cutting edge 22, and is therefore identical to the additional cutting edge and does not include the inner portion of the cutting edge 36.

[0048] In the design example shown, the additional cutting corner 24 is rounded because it has a corner radius R3 ranging from 0.4 mm to 5 mm. The additional cutting edge 24 extends continuously throughout. On the other hand, the transition from the additional cutting corner 24 to the secondary cutting edge 20 is configured here as a corner 38.

[0049] In an alternative not depicted, the additional cutting corner 24 is not rounded but pointed. In this case, the additional cutting edge 24 extends primarily radially outward and meets the secondary cutting edge 20 at a defined angle. In the pointed configuration, a corner 38 is formed at the end of the additional cutting edge 22 via the additional cutting corner 24.

[0050] In the design example shown, both the cut corner 10 and the additional cut corner 24 are rounded. However, in principle, a mixed configuration is also possible, where the cut corner 10 is rounded and the additional cut corner 24 is pointed, or vice versa. In the design example shown, the cut corner 10 and the additional cut corner 24 are configured to have the same shape; that is, they each have a contour, and their shapes are the same but their sizes are different. Therefore, the additional cut corner 24 is an enlarged version of the cut corner 10, and thus stands out accordingly.

[0051] In the design example shown, the cut corner 10 and the additional cut corner 24 enclose an angle W of less than 90°. Figure 1 The angle W is clearly shown. Angle W determines how much of the workpiece machining is done by the additional cutting corner 24 and how much by the cutting corner 10 during one complete rotation of drill 2. The smaller the angle W, the smaller the load on the additional cutting corner 24 and the larger the load on the cutting corner 10. Combined with the overhangs 32 and 34, this creates a two-dimensional parameter space in which the load distribution is adjusted according to the two parameters: angle W and overhangs 32 and 34.

[0052] In the design example shown, drill 2 includes two angles W, both of the same size. In contrast, in an equally suitable configuration, though not explicitly shown, angles W are of different sizes.

[0053] In the illustrated design example, a chip removal groove 40 is located in front of the main cutting edge 8. Chips detached by the main cutting edge 8 are carried away from the drill tip 4 towards the rear in the axial direction A through this groove. Here, the chip removal groove 40 extends along the entire length of the main cutting edge 8 and then terminates at the center 12. The drill 2 also includes an additional chip removal groove 42 before the additional cutting corner 24 to receive chips generated at the additional cutting corner 24, typically by the additional cutting edge 22. The chip removal groove 42 to the additional cutting edge 22 is also shallower than the chip removal groove 40 to the main cutting edge 8, and therefore protrudes less into the base body 6. This reserves space for an optional coolant channel 44, which, viewed in the rotational direction U of the illustrated design example, is positioned between the main cutting edge 8 and the chip removal groove 42 to the additional cutting edge 22. Here, both chip removal grooves 40 and 42 are helical.

[0054] As can be seen in the figure, the main cutting edge 8 is adjacent to a free surface 46, which slopes downward in the direction of the additional cutting corner 24 and transitions to a secondary free surface 48 that slopes upward in the direction of the additional cutting corner 24. Due to the free surface 46 and the secondary free surface 48, the drill tip 4 includes a recess on one side positioned between the main cutting edge 8 and the center 12, and on the other side positioned between the additional cutting edge 22 and the additional cutting corner 24, preventing the drill tip 4 from rubbing against the workpiece during operation. Here, the additional cutting edge 22 terminates at the secondary free surface 48 towards the center 12, and the secondary free surface is thus positioned between the center 12 and the additional cutting edge 22. The additional cutting edge 22 is formed on the end side via the secondary free surface 48.

[0055] The free surface 46 is defined at the front by the main cutting edge 8. At the rear, the free surface 46 is defined in the center 12 by the edge thinning section 16. At the rear facing the outer cutting edge 18, the free surface 46 is defined by the chip groove 42 leading to the additional cutting edge 22. The secondary free surface 48 is disposed between the edge thinning section 16 and the chip groove 42. This then defines the free surface 46 again at the rear. The drill tip 4 continues to slope downward from the free surface 46 into the chip groove 42 connecting to the additional cutting edge 22 and into the edge thinning section 16, while the secondary free surface 48, in turn, creates an upward slope, causing the additional cutting corner 24 to protrude accordingly. At the rear, here, the secondary free surface 48 also transitions into the edge thinning section 16, and at the front, it transitions into the chip groove 42 connecting to the additional cutting edge 22.

[0056] In principle, the drill 2 may include multiple main cutting edges 8, wherein one, more, or all of the main cutting edges are followed by one or more additional cutting edges 22. In the design example shown, the drill 2 includes exactly two main cutting edges 8, each having a cutting corner 10, followed by exactly one additional cutting corner 24, or more precisely, one additional cutting edge 22 having the additional cutting corner 24.

Claims

1. A drill (2) comprising a drill tip (4), wherein the drill tip (4) comprises at least one main cutting edge (8) having a cutting corner (10), the main cutting edge (8) extending from the cutting corner to a center (12), wherein the drill tip (4) comprises at least one additional cutting edge (22) having an additional cutting corner (24), the additional cutting edge (22) extending from the additional cutting corner in the direction of the center (12), wherein the additional cutting edge (22) is formed only on an outer portion (26) of the drill tip (4) and is thus shorter than the main cutting edge (8), wherein the additional cutting corner (24) protrudes beyond the cutting corner (10); wherein in the center (12) the drill tip (4) further comprises a chisel edge (14) and a free surface in the center (12) is delimited by an edge thinning (16), the chisel edge (14) being formed by the edge thinning (16) such that the main cutting edge (8) transitions into the chisel edge (14) at a transition to the center (12).

2. The drill (2) according to claim 1, wherein the additional cutting corner (24) protrudes beyond the cutting corner (10) in an axial direction (A).

3. The drill (2) according to claim 1 or 2, wherein the additional cutting corner (24) protrudes beyond the cutting corner (10) in a radial direction (R).

4. The drill (2) according to any one of claims 1 to 3, wherein the additional cutting corner (24) is rounded.

5. The drill (2) according to any one of claims 1 to 3, wherein the additional cutting corner (24) is pointed.

6. The drill (2) according to any one of claims 1 to 5, wherein the cutting corner (10) and the additional cutting corner (24) are configured to have the same shape.

7. The drill (2) according to any one of claims 1 to 6, wherein the cutting corner (10) and the additional cutting corner (24) enclose an angle (W) of less than 90°.

8. The drill (2) according to any one of claims 1 to 7, wherein the drill comprises a plurality of main cutting edges (8), each main cutting edge having a cutting corner (10) followed by an additional cutting corner (24), the additional cutting corner enclosing an angle (W) with the cutting corner (10) such that a plurality of angles (W) is formed, wherein the angles (W) have different sizes.

9. The drill (2) according to any one of claims 1 to 8, wherein the drill comprises a flutes (42) preceding the additional cutting corner (24) for receiving chips on the additional cutting corner (24).

10. The drill (2) according to any one of claims 1 to 9, wherein the main cutting edge (8) adjoins a free surface (46) which slopes downward in the direction of the additional cutting corner (24) and transitions into a secondary free surface (48) which slopes upward in the direction of the additional cutting corner (24).

11. The drill bit (2) according to any one of claims 1 to 10, wherein the additional cutting edge (22) terminates at a secondary free surface (48) towards the center (12).

12. The drill bit (2) according to any one of claims 1 to 11, wherein the drill bit comprises exactly two main cutting edges (8), each main cutting edge having a cutting corner (10) followed by exactly one additional cutting corner (24), respectively.

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