阅读说明：本技术 钻子 (Drill bit ) 是由 H.考珀 J.施瓦格尔 C.施特劳赫曼 于 2021-03-18 设计创作，主要内容包括：本发明涉及一种钻子(2),其包括钻尖(4),其中所述钻尖(4)包括具有切割拐角(10)的至少一个主切割刃(8),所述主切割刃(8)从所述切割拐角延伸到中心(12),其中所述钻尖(4)包括具有额外切割拐角(24)的至少一个额外切割刃(22),所述额外切割刃(22)在所述中心(12)的方向上从所述额外切割拐角延伸,其中所述额外切割刃(22)仅形成于所述钻尖(4)的外部部分(26)上,因此短于所述主切割刃(8),其中所述额外切割拐角(24)突出超过所述切割拐角(10)。(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) with a cutting corner (10), from which the main cutting edge (8) extends to a center (12), wherein the drill tip (4) comprises at least one additional cutting edge (22) with an additional cutting corner (24), from which the additional cutting edge (22) extends 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 thus is shorter than the main cutting edge (8), wherein the additional cutting corner (24) protrudes beyond the cutting corner (10).)

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) with an additional cutting corner (24), from which additional cutting edge (22) extends in the direction of the centre (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).

2. Drill (2) according to claim 1,

wherein the additional cutting corner (24) protrudes beyond the cutting corner (10) in the axial direction (A).

3. 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. Drill (2) according to one of the claims 1 to 3,

wherein the additional cutting corner (24) is rounded.

5. Drill (2) according to one of the claims 1 to 3,

wherein the additional cutting corner (24) is pointed.

6. Drill (2) according to one of the claims 1 to 5,

wherein the cutting corner (10) and the additional cutting corner (24) are configured to have the same shape.

7. Drill (2) according to one of the claims 1 to 6,

wherein the cutting corner (10) and the additional cutting corner (24) enclose an angle (W) of less than 90 °.

8. Drill (2) according to one of the 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), respectively, enclosing an angle (W) with the cutting corner (10) such that a plurality of angles (W) is formed,

wherein the angles (W) have different magnitudes.

9. Drill (2) according to one of the claims 1 to 8,

wherein the drill comprises a flute (42) preceding the additional cutting corner (24) for receiving chips on the additional cutting corner (24).

10. Drill (2) according to one of the claims 1 to 9,

wherein the main cutting edge (8) adjoins a free surface (46) which slopes downwards in the direction of the additional cutting corner (24) and which transitions into a secondary free surface (48) which slopes upwards in the direction of the additional cutting corner (24).

11. Drill (2) according to one of the claims 1 to 10,

wherein the additional cutting edge (24) ends at a secondary free surface (48) towards the centre (12).

12. Drill (2) according to one of the claims 1 to 11,

wherein the drill 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.

Technical Field

The invention relates to a drill.

Background

Drills are used for machining workpieces by drilling. For this purpose, the drill comprises a drill tip with two main cutting edges which strip chips off the workpiece, for example when the drill is rotated about a longitudinal axis. As a result, the front of the drill is sometimes subjected to heavy loads, which can lead to wear. Generally radially outward, the wear is greatest, so damage usually occurs first there. The so-called cutting corners forming the outer ends of the respective main cutting edges are particularly affected. The service life of the drill is limited primarily by wear of the cutting corners.

KR 101000863B 1 describes a drill which, in addition to two main cutting edges, comprises two further auxiliary cutting edges formed between the main cutting edges. The auxiliary cutting edge has a length corresponding to 0.4 times the radius of the drill. A part of the torque is distributed from the main cutting edge to the auxiliary cutting edge, whereby it is possible to increase the feed rate.

Disclosure of Invention

Objects of the invention

In this respect, it is an object of the present invention to provide an improved drill having the longest possible service life.

According to the invention, said object is achieved by a drill having the features according to claim 1. Advantageous configurations, further developments and variants are the subject matter of the dependent claims.

Drills are used for machining workpieces by drilling. In general, a drill is a rotary tool that extends along a longitudinal axis about which the drill rotates in a direction of rotation when in operation.

The drill comprises a drill tip which is formed at the front side of the drill and thus faces the workpiece during operation. The drill tip is formed as one integral piece, i.e. one piece, with the drill base body, or as a cutting insert of the drill base body.

The drill tip includes at least one primary cutting edge having a cutting corner, the primary cutting edge extending from the cutting corner to the center of the drill. The main cutting edge provides a first cutting action of the drill. Said centre is in particular 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 said centre, the drill tip preferably comprises a chisel edge. For this purpose, the edge thinning is suitably formed in the center, so that the main cutting edge transitions into the chisel edge at the transition to the center. On the other hand, on the outer edge, i.e. on the cutting corner, the major cutting edge in particular adjoins the minor cutting edge which extends substantially in the axial direction, for example spirally around the longitudinal axis.

The drill tip further comprises at least one additional cutting edge with an additional cutting corner, which extends from the additional cutting corner in the direction of the center. The extra cutting edge is formed only on the outer portion of the drill tip and is thus shorter than the main cutting edge. The additional cutting edge provides an additional second cutting action. The configuration of the additional cutting edge is fundamentally the same as that of the main cutting edge, so that the additional cutting edge also extends substantially from the cutting corner, which in this case is more particularly the additional cutting corner, towards the center on the drill tip outer edge. However, the extra cutting edge does not extend all the way to the center, but ends earlier, compared to the main cutting edge, so that the extra cutting edge is shorter overall. This forms the outer part of the drill tip which surrounds the centre and extends over a defined radius from the outer edge of the drill tip, i.e. from the outer surface of the drill, inwards. The outer portion is disposed immediately adjacent to the center, or another center section, also annular, is disposed between the center and the outer portion. In particular, the center, center section and outer portion are concentrically disposed. The radius of the outer portion, i.e. its thickness, and thus the length of the additional cutting edge, is preferably 0.1 to 0.5 times, especially preferably 0.2 to 0.4 times, thus approximately one third of the total radius of the drill. The total radius corresponds to half the total diameter.

As with the major cutting edge and its cutting corner, the additional cutting edge, and in particular, its additional cutting corner, also suitably abuts the minor cutting edge. This secondary cutting edge also extends substantially in an axial direction, e.g. helically around the longitudinal axis.

In the present case, the additional cutting corner protrudes beyond the cutting corner. In particular, this means that when the main cutting edge is viewed against the direction of rotation, the additional cutting corner is not completely covered by the cutting corner and disappears behind it, but rather the additional cutting corner protrudes and thus forms an overhang (overlap) along the cutting corner with respect to the cutting corner. Roughly speaking, the additional cutting corner is configured to be larger than the cutting corner or to protrude beyond the cutting corner. In particular, the additional cutting edge thus also projects partially or completely beyond the main cutting edge.

In particular, it is an essential aspect of the invention to reduce the loading of the main cutting edge, in particular its cutting corner, by means of the additional cutting edge, in particular by means of its additional cutting corner. Due to the additional cutting action on the outer part, the load on the main cutting edge is correspondingly relieved in the radial direction on the outside. Any type of load is distributed between the main cutting edge and the following extra cutting edge. Since the load increases with increasing radius and is greatest at the outer edge, in the present case the extra cutting edge is configured shorter than the main cutting edge in order to, inter alia, relieve the load on the outside and achieve the highest possible stability of the drill tip towards the inside. The wear on the main cutting edge is more even and the service life is thus increased.

In principle, it is sufficient to align the additional cutting corners with the cutting corners, i.e. to make them the same size. Also, in this way, part of the load on the cut corner is absorbed by the extra cut corner. However, this can be improved still further, in particular by configuring the additional cutting corner to protrude, i.e. the additional cutting corner has an overhang with respect to said cutting corner. It is thus possible to distribute the load more precisely and in particular specifically between the cutting corner and the additional cutting corner. The distribution can now be optimally tailored for a wide variety of applications.

In one advantageous configuration, the additional cutting corner protrudes beyond the cutting corner in the axial direction, i.e. along the longitudinal axis of the drill. Thus, the drill is longer at the extra cutting corner than at the cutting corner. This results in a length difference, preferably from 0.05mm to 2 mm. Accordingly, the additional cutting corner accordingly protrudes in the axial direction beyond the cutting corner by such a length difference, which is also referred to as axial overhang. In one configuration, the axial overhang is constant along the additional cut corner, while in another configuration it varies.

Specifically, the axial overhang causes the additional cutting corner to protrude in the axial direction relative to the cutting corner. In general, however, the additional cutting corner does not project as far beyond the chisel edge of the drill in the axial direction, but is preferably set back with respect to said chisel edge, i.e. offset backwards in the axial direction by a defined distance. Viewed strictly in the axial direction from front to back, an additional cutting corner is then positioned between the chisel edge and said cutting corner. Thus, in the axial direction, in particular, the chisel edge forms the foremost point of the drill.

In a further advantageous configuration, the additional cutting corner protrudes beyond the cutting corner in a radial direction, i.e. in a direction perpendicular to the longitudinal axis. Similar to the length difference in the axial direction, the drill has a larger radius at the extra cut corner than at said cut corner. This will result in a radius difference of preferably from 0.05mm to 2 mm. Accordingly, the additional cutting corner accordingly protrudes in the radial direction beyond the cutting corner by this difference in radius, which is also referred to as radial overhang. In one configuration, the radial overhang is constant along the additional cutting corner, while in another configuration it varies.

Advantageously, the radial and axial outward extensions can also be combined with each other, thus causing the additional cutting corners to protrude beyond the cutting corners in both the radial and axial directions.

The cutting corner is substantially an integral part of the main cutting edge and forms the end of said main cutting edge in the radial direction as well as to the outside. Similarly, the additional cutting corner is also substantially an integral part of the additional cutting edge and forms an end of said additional cutting edge in the radial direction as well as to the outside. In principle, there are a number of suitable configurations of the cutting corners and the additional cutting corners, which are selected depending on the specific application.

In one suitable configuration, the additional cutting corners are rounded. Thus, the additional cutting corner itself is not pointed but actually forms a corner cutting edge itself, which is thus or corresponds to the outer partial cutting edge of the additional cutting edge. In other words, the additional cutting edge is the same as the corner cutting edge such that the additional cutting edge is limited to the additional cutting corner of a circle, or the corner cutting edge is adjoined to the inside by an inner partial cutting edge which is then formed as a whole together with the corner cutting edge. The specific design depends on how far the additional cutting edge is to extend towards the center and how long the corner cutting edge is, i.e. how much the additional cutting corner is rounded. Preferably, the cutting corner is rounded because it has a corner radius of 0.4mm to 5 mm. In particular, the corner radius is measured in an imaginary plane which extends parallel to the longitudinal axis or at a small angle of only at most 20 °. The transition between the inner and outer partial cutting edges is suitably continuous, i.e. rounded, and in particular not sharp or discontinuous. The transition from the corner cutting edge to the minor cutting edge is likewise continuous or forms a corner here.

Alternatively, in one suitable arrangement, the additional cutting corner is pointed. Here, the additional cutting edge extends mainly radially outwards and meets the secondary cutting edge at a defined angle, for example, exceeding 90 ° to 120 °. In the pointed configuration, a corner or a sharp point is then formed by the additional cutting corner at the end of the additional cutting edge.

The rounded additional cutting corners are particularly advantageous for machining abrasive materials such as cast iron. Due to the rounded design, the load on the outer edge is distributed over the longitudinally extending area, i.e. the outer partial cutting edge. In contrast, with the pointed configuration, the load on the outer edge is selectively directed onto the pointed extra cutting corner. Again, then, the pointed configuration is particularly suitable for machining soft and less abrasive materials such as aluminum.

As with the extra cutting corner, the cutting corner of the major cutting edge is preferably rounded or pointed, depending on the application. Suitably, the cutting corner and the additional cutting corner are both rounded or both pointed. Hybrid configurations are also possible, wherein 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.

A design is particularly preferred 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, which is identical in its outer shape but different in size, so that the additional cutting corner is an enlarged version of the cutting corner and therefore stands out accordingly. Thus, the additional cutting corners result from a corresponding scaling of the cutting corners without deformation. Therefore, the overhang of the extra cutting corner is particularly uniform.

Preferably, the cutting corner and the additional cutting corner enclose an angle of less than 90 °. Particularly preferred is an angle in the range of 20 ° to 80 °. In particular, the angle is measured in the direction of rotation, i.e. in a plane perpendicular to the longitudinal axis. This is based on the following observation: the distribution of the load 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. The reason for this is that the angle determines how much machining of the workpiece is done by the extra cutting corner during one full rotation of the drill. The smaller the angle, the smaller the load on the extra cutting corner and the larger the load on the cutting corner.

In combination with the overhang, this results in a two-dimensional parameter space, in which the distribution of the load is adjusted depending on both the angle and the overhang. Thus, if the angle is increased and the overhang is smaller or vice versa, the load can be kept constant. Thus, for a given overhang or angle, the distribution can be changed by adjusting the angle or overhang, i.e. the corresponding further parameter. For example, manufacturing-related limitations with regard to the overhang or angle are thus advantageously overcome by a further parameter.

In one advantageous configuration, the drill comprises a plurality of main cutting edges, each main cutting edge having a cutting corner followed by an additional cutting corner, respectively, enclosing an angle with the cutting corner such that a plurality of angles are formed. Preferably, the angles have different sizes. In other words, in case of a drill having a plurality of main cutting edges and respectively associated additional cutting corners, a corresponding number of angles is also formed. These angles are suitably selected to have different sizes in order to reduce vibrations and in particular so-called chatter of the workpiece or drill during machining. The selection of different angles breaks the symmetry that the drill originally has, so that the vibration characteristics of the system consisting of the drill and the workpiece advantageously change during the machining.

In particular, the front face of the main cutting edge is a flute, through which chips stripped by the main cutting edge are carried away in the axial direction from the drill tip towards the rear. In particular, the flute extends over the full length of the main cutting edge and then ends at the center as well. Thus, the centre also forms the core of the drill, to which the flutes extend, but into which the flutes do not enter, thus giving the flutes a depth corresponding to the difference between the total radius of the drill and the core radius of the core.

Preferably, the drill comprises a flute preceding the additional cutting corner for receiving chips on the additional cutting corner. Thus, the drill includes a further flute to the additional cutting edge in addition to the flute to the main cutting edge. The chips produced by the extra cutting corner, usually by the extra cutting edge, are carried away through this extra flute. These chips usually have a different shape than the chips on the main cutting edge. Since the additional cutting edge is shorter, shorter chips are usually also produced here. The flute to the extra cutting edge is suitably also shallower than the flute to the main cutting edge, and therefore protrudes less far into the base body of the drill. In particular, this leaves room for an optional coolant channel, which is suitably arranged between the main cutting edge and the flute to the additional cutting edge, viewed in the direction of rotation. Preferably, both flutes are helical.

In an advantageous configuration, the main cutting edge adjoins a free surface which slopes downward in the direction of the additional cutting corner and transitions into a secondary free surface which slopes upward in the direction of the additional cutting corner. Specifically, the free surface behind the primary cutting edge forms a relief angle. Due to the free surface and the secondary free surface, the drill tip comprises a recess which is disposed between the main cutting edge and the centre on the one hand, and the additional cutting edge and the additional cutting corner on the other hand, and which prevents the drill tip from rubbing against the workpiece during operation.

Preferably, the additional cutting edge ends towards the centre at the minor free surface, in particular the minor free surface already described above. Thus, the secondary free surface is disposed between the center and the additional cutting edge. The length of the extra cutting edge is limited by the secondary free surface.

The free surface to the main cutting edge is delimited at the front by this same main cutting edge. The free surface in the rear portion, specifically the center, is defined by an edge thinning through which the chisel edge is formed. At the rear towards the outer edge, the free surface is in particular delimited by flutes to the additional cutting edge. The minor free surface is disposed between the edge thinning and the flute. This then also defines the free surface posteriorly. The drill tip continues to slope downwardly from the free surface into the flute leading to the additional cutting edge and into the edge thinning, while the secondary free surface conversely produces an upward slope so that the additional cutting corner protrudes accordingly. In the rear part, the secondary free surface preferably transitions into the edge thinning and in the front part into a flute leading to the additional cutting edge. In particular, the secondary free surface is configured to be fundamentally similar to the edge thinning, i.e. such that an additional cutting edge is formed at the end side by the secondary free surface.

In principle, the drill may comprise a plurality of main cutting edges, wherein one, more or all of the main cutting edges follow one or more additional cutting edges. An arrangement is particularly preferred in which the drill comprises exactly two main cutting edges, each main cutting edge having a cutting corner, followed by exactly one additional cutting corner, more precisely one additional cutting edge having an additional cutting edge. Drills with two main cutting edges are also referred to as double-edged drills and have particularly good stability, in particular centering, during operation. This stability is hardly or not at all affected by the additional but shorter additional cutting edge. In fact, the additional cutting edge makes the loading and wear of the main cutting edge, and in particular the cutting corner thereof, more uniform.

Drawings

In the following, design examples of the invention are explained in more detail with the aid of the figures. The figures show schematically:

figure 1 is a front view of a drill,

figure 2 is a detail of the drill of figure 1 in perspective view,

figure 3 is a detail of the drill of figure 1 in side view,

fig. 4 shows a detail of the drill of fig. 1 in different side views.

Detailed Description

Fig. 1-4 show examples of designs of a drill 2 for machining an undepicted workpiece by drilling. In general, the drill 2 is a rotary tool extending along a longitudinal axis L, about which the drill 2 rotates in a direction of rotation U when in operation. Fig. 1 shows a front view of a drill 2, fig. 2 shows a perspective view, and fig. 3 and 4 show respective side views, whereby the view of fig. 3 is rotated 90 ° in the direction of rotation U from the view in fig. 4. The drill 2 comprises a drill tip 4, which is formed at the front side of the drill 2 and thus faces the workpiece during operation. In the design example shown, the drill tip 4 is formed in one piece, i.e. in one piece, with the base body 6 of the drill 2. In an alternative not depicted, the drill tip 4 is configured as a cutting insert of the base body 6 of the drill 2.

The drill tip 4 comprises at least one main cutting edge 8 having a cutting corner 10, from which cutting corner the main cutting edge 8 extends to the centre 12 of the drill 2. One of the two main cutting edges 8 is highlighted in bold lines in fig. 1. The main cutting edge 8 provides a first cutting action of the drill. The centre 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 centre 12, the drill tip 4 here also comprises a chisel edge 14. For this purpose, the edge thinning 16 is formed such 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 edge 18, i.e. on the cutting corner 10, the major cutting edge 8 adjoins a minor cutting edge 20 extending substantially in the axial direction a, for example spirally around the longitudinal axis L.

The drill tip 4 further comprises at least one additional cutting edge 22 with an additional cutting corner 24, from which the additional cutting edge 22 extends in the direction of the centre 12. One of the two additional cutting edges 22 is likewise highlighted in bold lines in fig. 1. The extra 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 fundamentally the same as that of the main cutting edge 8, so that the additional cutting edge 22 also extends substantially from a cutting corner, in this case more specifically an additional cutting corner 24, towards the centre 12 on the outer edge 18 of the drill tip 4. However, the extra cutting edge 22 does not extend all the way to the center 12, but terminates earlier, compared to the main cutting edge 8, so that the extra cutting edge 22 is shorter overall. This forms the outer portion 26 of the drill tip 4 which surrounds the centre 12 and extends from the outer edge 18, i.e. from the outer surface 28 of the drill 2, inwards over a defined radius R2. The outer portion 26 is immediately adjacent the center 12, or as can be seen in fig. 1, another likewise annular center section 30 is disposed between the center 12 and the outer portion 26. Here, the center 12, the center section 30 and the outer portion 26 are concentrically disposed. The radius R2 of the outer portion 26, i.e. the thickness of said outer portion, and thus the length of the extra cutting edge 22, is here 0.1 to 0.5 times the total radius Rg.

Just as the major cutting edge 8 and its cutting corner 10, the additional cutting edge 22, and in particular its additional cutting corner 24, also adjoins the minor cutting edge 20. This secondary cutting edge here also extends substantially helically around the longitudinal axis in the axial direction a. The secondary cutting edge 20 can be seen in particular in fig. 2.

In the present case, the additional cutting corner 24 protrudes beyond the cutting corner 10. This means that when the main cutting edge 8 is viewed against the direction of rotation U, the extra cutting corner 24 is not completely covered by the cutting corner 10 and disappears behind it, but the extra cutting corner 24 protrudes and thus forms an overhang 32, 34 along the cutting corner 10 with respect to the cutting corner 10. Here, the additional cutting edge 22 also protrudes partially or completely beyond the main cutting edge 10.

In the illustrated configuration, the additional cutting corner 24 protrudes beyond the cutting corner 10 in the axial direction a, i.e. along the longitudinal axis L. Thus, the drill 2 is longer at the extra cutting corner 24 than at the cutting corner 10. This produces a length difference, here from 0.05mm to 2mm and also referred to as axial overhang 32. Furthermore, in the radial direction R, i.e. perpendicular to the longitudinal axis L, the additional cutting corner 24 also protrudes beyond the cutting corner 10. Similar to the length difference in the axial direction a, the drill 2 then has a larger radius Rg at the additional cutting corner 24 than at the cutting corner 10. This creates a difference in radius, here from 0.05mm to 2mm and also referred to as the radial overhang 34. In fig. 2 and 4, the two overhangs 32, 34 are indicated by dashed lines below the additional cutting edge 22, and the radius and length difference are additionally indicated by two respective arrows.

The radial overhang 34 and the axial overhang 32 can also be realized independently of one another, so that the additional cutting corner 24 then protrudes beyond the cutting corner 10 in the radial direction R or in the axial direction a.

The cutting corner 10 is substantially an integral part of the main cutting edge 8 and forms the end thereof in the radial direction R and to the outside. Similarly, the additional cutting corner 24 is also substantially an integral part of the additional cutting edge 22 and forms the end thereof in the radial direction R as well as to the outside. In principle, there are a number of suitable configurations for the cutting corner 10 and the additional cutting corner 24.

For example, in the design example shown, the extra cutting corner 24 is rounded and itself forms a corner cutting edge. Here, the rounded additional cutting corner 24 is largely identical to the additional cutting edge 22. As shown in fig. 4, the extra cutting corner 24 is an outer partial cutting edge of the extra cutting edge 22. The outer partial cutting edge adjoins to the inside by an inner partial cutting edge 36 which then forms, together with the corner cutting edge, an additional cutting edge 22. For example, in the design example shown, the inner part-cutting edge 36 is a straight continuation of the round outer part-cutting edge. On the other hand, in a variant not depicted, the rounded additional cutting corner 24 corresponds entirely to the additional cutting edge 22, and is therefore identical to the additional cutting edge and does not comprise the inner partial cutting edge 36.

In the design example shown, the extra cutting corner 24 is rounded because it has a corner radius R3 of 0.4mm to 5 mm. The additional cutting edge 24 extends generally continuously. On the other hand, the transition from the additional cutting corner 24 to the minor cutting edge 20 is configured here as a corner 38.

In an alternative not depicted, the additional cutting corner 24 is not rounded, but pointed. In this case, the additional cutting edge 24 then extends mainly radially outwards and meets the secondary cutting edge 20 at a defined angle. In the pointed configuration, a corner 38 is formed by the additional cutting corner 24 at the end of the additional cutting edge 22.

In the design example shown, the cutting corner 10 and the additional cutting corner 24 are both rounded. However, in principle, hybrid configurations are also possible, in which the cutting corner 10 is rounded and the additional cutting corner 24 is pointed, or vice versa. In the design example shown, the cutting corner 10 and the additional cutting corner 24 are configured to have the same shape; i.e. they each have a profile, which is identical in its outer shape but different in size. Thus, the additional cutting corner 24 is an enlarged version of the cutting corner 10 and therefore stands out accordingly.

In the design example shown, the cutting corner 10 and the additional cutting corner 24 enclose an angle W of less than 90 °. The angle W is explicitly shown in fig. 1. The angle W determines how much machining of the workpiece is done by the extra cutting corner 24 and how much by the cutting corner 10 during one full rotation of the drill 2. The smaller the angle W, the smaller the load on the extra cut corner 24 and the larger the load on the cut corner 10. In combination with the overhangs 32, 34, this results in a two-dimensional parameter space, in which the distribution of the load is adjusted depending on both parameters, angle W and overhangs 32, 34.

In the design example shown, the drill 2 comprises two angles W, which are also of the same size. In contrast, in a configuration not explicitly shown but equally suitable, the angle W is of a different magnitude.

In the design example shown, the main cutting edge 8 is preceded by a flute 40, through which the chips stripped off by the main cutting edge 8 are carried away in the axial direction a from the drill tip 4 towards the rear. Here, the flutes 40 extend over the entire length of the main cutting edge 8 and then end also at the center 12. The drill 2 further comprises an additional flute 42 before the additional cutting corner 24 for receiving chips generated by said additional cutting corner 24, typically by the additional cutting edge 22, at the additional cutting corner 24. The flutes 42 to the extra cutting edge 22 are also shallower than the flutes 40 to the main cutting edge 8 and therefore project less far into the chassis body 6. This leaves room for an optional coolant channel 44, which is arranged between the main cutting edge 8 and the flute 42 to the additional cutting edge 22, viewed in the direction of rotation U in the shown design example. Here, the flutes 40, 42 are both helical.

As can be seen in the figure, the major cutting edge 8 adjoins a free surface 46 which is inclined downwards in the direction of the additional cutting corner 24 and which transitions into a minor free surface 48 which is inclined upwards 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 comprises a recess which is disposed between the main cutting edge 8 and the centre 12 on the one hand, and the additional cutting edge 22 and the additional cutting corner 24 on the other hand, and which prevents the drill tip 4 from rubbing against the workpiece during operation. Here, the additional cutting edge 22 ends towards the center 12 at a secondary free surface 48, which is thus disposed between the center 12 and the additional cutting edge 22. The additional cutting edge 22 is formed on the end side by a secondary free surface 48.

The free surface 46 is delimited frontally by the main cutting edge 8. Posteriorly, the free surface 46 is bounded in the center 12 by the edge thinning 16. Towards the rear of the outer edge 18, a free surface 46 is delimited by the flutes 42 to the additional cutting edge 22. The minor free surface 48 is disposed between the edge thinning 16 and the flutes 42. This then also defines the free surface 46 at the rear. The drill tip 4 continues to slope downwardly from the free surface 46 into the flute 42 leading to the additional cutting edge 22 and into the edge thinning 16, while the secondary free surface 48 instead produces an upward slope so that the additional cutting corner 24 protrudes accordingly. At the rear, here too, the secondary free surface 48 transitions into the edge thinning 16 and at the front into the flute 42 leading to the additional cutting edge 22.

In principle, the drill 2 may comprise a plurality of main cutting edges 8, wherein one, more or all of the main cutting edges follow one or more additional cutting edges 22. In the shown design example, the drill 2 comprises exactly two main cutting edges 8, each having a cutting corner 10, followed by exactly one additional cutting corner 24, more precisely one additional cutting edge 22 having an additional cutting corner 24.