drill

Abstract

Drill (2) having a drill bit (4), - wherein the drill bit (4) has at least one main cutting edge (8) with a cutting edge (10) from which the main cutting edge (8) extends to a center (12), - wherein the drill bit (4) has at least one additional cutting edge (22) with an additional cutting edge (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 section (26) of the drill tip (4) and is therefore shorter than the main cutting edge (8), - wherein the additional cutting corner (24) projects beyond the cutting corner (10) to distribute the load between the cutting corner (10) and the additional cutting corner (24).

Description

Background of the invention

[0001] The invention relates to a drill.

[0002] A drill bit is used for machining a workpiece by drilling. For this purpose, a drill bit has a drill bit tip with, for example, two main cutting edges, which remove chips from the workpiece as the drill bit rotates around a longitudinal axis. This sometimes places heavy loads on the front of the drill bit, leading to wear. Wear is usually greatest in the radially outward direction, so damage often occurs here first. The cutting edge, which forms the outer end of each main cutting edge, is particularly affected. The service life of the drill bit is then limited primarily by wear on the cutting edge.

[0003] KR 101 000 863 B1 describes a drill that, in addition to two main cutting edges, also has two auxiliary cutting edges located between the main cutting edges. The auxiliary cutting edges have a length corresponding to 0.4 times the radius of the drill. Part of the torque is distributed from the main cutting edges to the auxiliary cutting edges, allowing for increased feed rates.

[0004] DE 103 46 217 A1 describes a drill with solid cutting edges and reaming cutting edges, whereby the reaming cutting edges are shorter than the solid cutting edges.

[0005] US 2008 / 0193234 A1 describes a tool having a first and a second cutting edge, wherein the first cutting edge is spaced from a central axis at a first distance which is less than a second distance of the second cutting edge from the central axis. Object of the invention

[0006] Against this background, it is an object of the invention to provide an improved drill which has the longest possible service life. Solution to the task

[0007] The object is achieved according to the invention by a drill having the features according to claim 1. Advantageous embodiments, further developments and variants are the subject of the subclaims.

[0008] A drill is used for machining a workpiece by drilling. The drill is generally a rotary tool that extends along a longitudinal axis around which the drill rotates in a circular direction during operation.

[0009] The drill has a drill tip, which is formed on the front side of the drill and thus faces a workpiece during operation. The drill tip is either formed integrally, i.e., monolithically, with a base body of the drill or as a cutting insert for a base body of the drill.

[0010] The drill bit tip has at least one main cutting edge with a cutting corner, from which the main cutting edge extends to a center of the drill bit. The main cutting edge provides a first cutting effect of the drill bit. The center is in particular a circular inner region of the drill bit and has a radius which preferably corresponds to 0.1 to 0.3 times the total diameter of the drill bit. In the center, the drill bit tip preferably has a chisel cutting edge. For this purpose, a thinning is suitably formed in the center so that the main cutting edge merges into the chisel cutting edge at the transition to the center. On the outer edge, however, i.e. at the cutting corner, the main cutting edge is followed in particular by a secondary cutting edge which generally runs in the axial direction, for example spirally around the longitudinal axis.

[0011] The drill bit further comprises at least one additional cutting edge, with an additional cutting corner, from which the additional cutting edge extends towards the center. The additional cutting edge is formed only on an outer section of the drill bit and is therefore shorter than the main cutting edge. The additional cutting edge results in an additional, second cutting effect. The additional cutting edge is fundamentally designed similarly to the main cutting edge in such a way that the additional cutting edge generally extends from a cutting corner, here more precisely the additional cutting corner, on an outer edge of the drill bit towards the center. In contrast to the main cutting edge, however, the additional cutting edge does not extend all the way to the center, but ends beforehand, so that the additional cutting edge is shorter overall. This forms an outer section of the drill bit which surrounds the center and extends from the outer edge of the drill bit, i.e.from a lateral surface of the drill, extends inwards over a specific radius. The outer section either borders directly on the center or a further, likewise annular central section is arranged between the center and the outer section. The center, central section and outer section are in particular arranged concentrically. The radius of the outer section, i.e. its thickness, and thus the length of the additional cutting edge are 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 the total diameter.

[0012] Analogous to the main cutting edge and its cutting edge, the additional cutting edge, especially its cutting edge, is also suitably followed by a secondary cutting edge. This also generally runs in an axial direction, for example, spiraling around the longitudinal axis.

[0013] In this case, the additional cutting edge protrudes beyond the cutting edge. This specifically means that, when viewed from the opposite direction of rotation to the main cutting edge, the additional cutting edge is not completely concealed by the cutting edge and disappears behind it, but rather protrudes, forming a projection relative to the cutting edge that trails the cutting edge. Roughly speaking, the additional cutting edge is larger or protrudes relative to the cutting edge. In particular, the additional cutting edge thus also partially or completely protrudes relative to the main cutting edge.

[0014] A key aspect of the invention is, in particular, the relief of the main cutting edge, and in particular its cutting edge, by means of the additional auxiliary cutting edge and in particular its auxiliary cutting edge. Due to the additional cutting action on the outer section, the main cutting edge is correspondingly relieved in the radial direction. Any load is distributed between the main cutting edge and the trailing auxiliary cutting edge. Since the load increases with increasing radius and is greatest at the outer edge, the auxiliary cutting edge is shorter than the main cutting edge in order to achieve relief, especially on the outside, and to maintain the greatest possible stability of the drill tip towards the inside. The main cutting edge therefore wears much more evenly, resulting in an improved tool life.

[0015] In principle, it is sufficient to align the additional cutting corner with the cutting corner, i.e., to make both the same size. This also absorbs part of the load on the cutting corner. In this case, however, we go even further, and deliberately design the additional cutting corner to project, meaning the additional cutting corner protrudes relative to the cutting corner. This allows for a much more precise and targeted distribution of the load between the cutting corner and the additional cutting corner. The distribution can then be optimally adapted to a wide variety of applications.

[0016] In an advantageous embodiment, the additional cutting edge projects beyond the cutting edge in an axial direction, i.e., along the longitudinal axis of the drill. The drill is therefore longer at the additional cutting edge than at the cutting edge. This results in a length difference, which is preferably between 0.05 mm and 2 mm. The additional cutting edge therefore projects beyond the cutting edge in the axial direction by this length difference, which is also referred to as the axial projection. The axial projection is constant along the additional cutting edge in one embodiment and varies in another embodiment.

[0017] The axial projection, in particular, results in the additional cutting edge protruding axially relative to the cutting edge. Generally, however, the additional cutting edge does not protrude beyond the chisel edge of the drill in the axial direction, but is preferably set back from it, i.e., offset a certain distance to the rear in the axial direction. Viewed purely in the axial direction from front to back, the additional cutting edge lies between the chisel edge and the cutting edge. The chisel edge therefore forms, in particular, a frontmost point of the drill in the axial direction.

[0018] In a further advantageous embodiment, the additional cutting edge projects beyond the cutting edge in a radial direction, i.e., perpendicular to the longitudinal axis. Analogous to the length difference in the axial direction, the drill bit then has a larger radius at the additional cutting edge than at the cutting edge. This results in a radius difference, which is preferably between 0.05 mm and 2 mm. The additional cutting edge therefore projects beyond the cutting edge in the radial direction by this radius difference, which is also referred to as the radial projection. The radial projection is constant along the additional cutting edge in one embodiment and varies in another embodiment.

[0019] The radial and axial projections can also be advantageously combined with each other, so that the additional cutting edge projects beyond the cutting edge both in the radial direction and in the axial direction.

[0020] The cutting edge is generally a component of the main cutting edge and forms its radial and outward end. Similarly, the additional cutting edge is generally a component of the additional cutting edge and forms its radial and outward end. There are basically various suitable designs for the cutting edge and the additional cutting edge, which are selected depending on the specific application.

[0021] In a suitable embodiment, the additional cutting corner is rounded. As a result, the additional cutting corner is not point-shaped, but rather forms a corner cutting edge, which is an outer partial cutting edge of the additional cutting edge or corresponds to it. In other words: either the additional cutting edge is identical to the corner cutting edge, so that the additional cutting edge is limited to the rounded additional cutting corner, or an inner partial cutting edge adjoins the corner cutting edge towards the inside, which partial cutting edge together with the corner cutting edge then forms the additional 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 strongly the additional cutting corner is rounded. The additional cutting corner is preferably rounded in that it has a corner radius of 0.4 mm to 5 mm.The corner radius is measured in an imaginary plane that extends parallel to or at a slight angle of up to 20° to the longitudinal axis. The transition between the inner and outer cutting edges is preferably continuous, i.e., round and straight, not pointed or discontinuous. The transition from the corner cutting edge to the secondary cutting edge is either equally continuous or, alternatively, a corner is formed.

[0022] Alternatively, the additional cutting edge can be pointed in a suitable configuration. In this case, the additional cutting edge runs predominantly radially outward and meets the secondary cutting edge at a specific angle, for example, greater than 90° to 120°. In the pointed configuration, a corner or point is formed at the end of the additional cutting edge with the additional cutting edge.

[0023] The rounded additional cutting edge is particularly advantageous when machining abrasive materials such as cast iron. The rounded design distributes the load on the outer edge over an elongated area, namely the outer cutting edge. In contrast, with the pointed design, the load on the outer edge is directed at a specific point on the pointed additional cutting edge. The pointed design, on the other hand, is particularly suitable for machining soft and less abrasive materials such as aluminum.

[0024] The cutting edge of the main cutting edge, like the additional cutting edge, is preferably rounded or pointed, depending on the application. Conveniently, both the cutting edge and the additional cutting edge are either rounded or pointed. A mixed design, in which the cutting edge is rounded and the additional cutting edge is pointed, or vice versa, is also possible, at least as long as the additional cutting edge still projects beyond the cutting edge.

[0025] A particularly preferred embodiment is one in which the cutting corner and the additional cutting corner are formed with the same shape. This means that the cutting corner and the additional cutting corner each have a contour that then follows the same course but is dimensioned differently, so that the additional cutting corner is a correspondingly enlarged version of the cutting corner and thus protrudes accordingly. The additional cutting corner is thus obtained by appropriate scaling without distorting the cutting corner. In this way, the protrusion of the additional cutting corner is formed particularly uniformly.

[0026] The cutting corner and the additional cutting corner preferably enclose an angle which is less than 90°. An angle in the range of 20° to 80° is particularly preferred. The angle is measured in particular in the direction of rotation, i.e. in a plane perpendicular to the longitudinal axis. This is based on the observation that the distribution of the load between the cutting corner and the additional cutting corner can be adjusted not only by means of the projection of the additional cutting corner, but also by means of the angle. This is because the angle determines which proportion of the machining of the workpiece is played by the additional cutting corner relative to the cutting corner during one full rotation of the drill. The smaller the angle, the less the additional cutting corner is loaded and the more the cutting corner.

[0027] In conjunction with the overhang, this results in a two-dimensional parameter space in which the load distribution is adjusted depending on the two parameters angle and overhang. This allows the load to be kept constant by increasing the angle for a smaller overhang, or vice versa. Similarly, for a given overhang or angle, the distribution can be changed by adjusting the angle or the overhang, i.e., the corresponding other parameter. In this way, manufacturing limitations regarding the overhang or the angle, for example, can be advantageously overcome by using the other parameter.

[0028] In an advantageous embodiment, the drill has a plurality of main cutting edges, each with a cutting corner, followed by an additional cutting corner which forms an angle with the cutting corner, such that a plurality of angles are formed. The angles are preferably of different sizes. In other words: in a drill with a plurality of main cutting edges and an associated additional cutting corner, a correspondingly large number of angles are also formed. These angles are expediently selected to be of different sizes in order to reduce vibrations and in particular chattering of the workpiece or drill during machining. By selecting different angles, the otherwise existing symmetry of the drill is broken up, so that the vibration properties of the system consisting of drill and workpiece change advantageously during machining.

[0029] In particular, a chip groove precedes the main cutting edge, through which chips removed by the main cutting edge are carried axially backward from the drill tip. The chip groove extends, in particular, over the full length of the main cutting edge and then also ends at the center. The center thus simultaneously forms a core of the drill, up to which the chip groove penetrates but into which it does not penetrate, so that the chip groove then has a depth corresponding to the difference between the total radius of the drill and the core radius of the core.

[0030] The drill preferably has a chip groove which runs ahead of the additional cutting edge for collecting chips at the additional cutting edge. In addition to the chip groove to the main cutting edge, the drill therefore has a further chip groove to the additional cutting edge. The chips which are generated by the additional cutting edge and generally by the additional cutting edge are removed via this additional chip groove. These chips usually have a different shape than the chips on the main cutting edge. Since the additional cutting edge is shorter, the chips here are typically also shorter. The chip groove to the additional cutting edge is also suitably shallower than the chip groove to the main cutting edge and therefore protrudes less deeply into the base body of the drill. This leaves space in particular for an optional coolant channel which is expediently arranged between the main cutting edge and the chip groove to the additional cutting edge, viewed in the direction of rotation.Both chip grooves are preferably spiral in design.

[0031] In an advantageous embodiment, the main cutting edge is adjoined by a clearance surface that slopes downwards toward the additional cutting edge and transitions into a secondary clearance surface that slopes upwards toward the additional cutting edge. The clearance surface behind the main cutting edge, in particular, forms a clearance angle. Due to the clearance surface and the secondary clearance surface, the drill tip has a depression located between the main cutting edge and the center on the one hand, and the additional cutting edge and the additional cutting edge on the other hand, preventing the drill tip from rubbing against the workpiece during operation.

[0032] Preferably, the additional cutting edge ends toward the center at a secondary clearance surface, which is in particular the secondary clearance surface described above. The secondary clearance surface is thus located between the center and the additional cutting edge. The length of the additional cutting edge is then limited by the secondary clearance surface.

[0033] The flank to the main cutting edge is bordered in the leading direction by that same main cutting edge. The flank is bordered in the trailing direction in the center in particular by the web thinning which forms the chisel cutting edge. Towards the outer edge, the flank is bordered in the trailing direction in particular by the chip groove to the additional cutting edge. The secondary flank is then arranged between the web thinning and the chip groove. This then also borders the flank in a trailing direction. While the drill tip drops further from the flank into the chip groove to the additional cutting edge and into the web thinning, the secondary flank creates a rise in contrast, so that the additional cutting edge protrudes accordingly. The secondary flank preferably merges in the trailing direction into the web thinning and in the leading direction into the chip groove to the additional cutting edge.In particular, the secondary flank is designed in principle similar to the point thinning, namely in such a way that the secondary flank forms the end of the additional cutting edge.

[0034] In principle, the drill can have several main cutting edges, one, several or all of which are followed by one or more additional cutting edges. A design is particularly preferred in this case in which the drill has exactly two main cutting edges, each with a cutting edge, each followed by exactly one additional cutting edge, or more precisely, an additional cutting edge with an additional cutting edge. A drill with two main cutting edges is also referred to as a double-edged drill and has particularly good stability and, in particular, centering during operation. The additional but shorter additional cutting edges hardly or not at all impair this stability. In return, the additional cutting edges result in more homogeneous loading and wear on the main cutting edges and, in particular, their cutting edges. Description of the characters

[0035] In the following, exemplary embodiments of the invention are explained in more detail with reference to a drawing. In each case, the following schematically show: Fig. 1 a front view of a drill, Fig. 2 a section of the drill Fig. 1 in a perspective view, Fig. 3 a section of the drill Fig. 1 in a side view, Fig. 4 a section of the drill Fig. 1 in a different side view. Description of the embodiments

[0036] In the Fig. 1-4 show an embodiment of a drill 2 used for machining a workpiece (not shown) by drilling. The drill 2 is generally a rotary tool extending along a longitudinal axis L, around which the drill 2 rotates in a direction of rotation U during operation. Fig. 1 shows a front view of the drill 2, Fig. 2 a perspective view and Fig. 3 and Fig. 4 each show a side view, whereby the view of the Fig. 3 starting from the view in Fig. 4 is rotated by 90° in the direction of rotation U. The drill 2 has a drill tip 4, which is formed on the front side of the drill 2 and thus faces a workpiece during operation. In the exemplary embodiment shown, the drill tip 4 is formed integrally, ie monolithically, with a base body 6 of the drill 2. In an alternative not shown, the drill tip 4 is formed as a cutting insert for a base body 6 of the drill 2.

[0037] The drill bit tip 4 has at least one main cutting edge 8 with a cutting edge 10, from which the main cutting edge 8 extends to a center 12 of the drill bit 2. In Fig. 1, one of the two main cutting edges 8 is shown clearly by a thicker line. The main cutting edge 8 creates an initial cutting effect. 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 has a chisel cutting edge 14. For this purpose, a thinning 16 is formed so that at the transition to the center 12, the main cutting edge 8 merges into the chisel cutting edge 14. At the outer edge 18, however, i.e. at the cutting corner 10, the main cutting edge 8 is adjoined by a secondary cutting edge 20, which generally runs in the axial direction A, for example, spirally around the longitudinal axis L.

[0038] The drill bit 4 further comprises at least one additional cutting edge 22, with an additional cutting edge 24, from which the additional cutting edge 22 extends towards the center 12. In Fig. 1, one of the two additional cutting edges 22 is also shown clearly by a thicker line. The additional cutting edge 22 is formed only on an outer section 26 of the drill tip 4 and is therefore shorter than the main cutting edge 8. The additional cutting edge 22 results in an additional, second cutting effect. The additional cutting edge 22 is designed similarly to the main cutting edge 8 in such a way that the additional cutting edge 22 also generally extends from a cutting corner, here more precisely the additional cutting corner 24, on an outer edge 18 of the drill tip 4 towards the center 12. In contrast to the main cutting edge 8, however, the additional cutting edge 22 does not extend all the way to the center 12, but ends beforehand, so that the additional cutting edge 22 is shorter overall. As a result, an outer section 26 of the drill tip 4 is formed, which surrounds the center 12 and extends from the outer edge 18, ie from a lateral surface 28 of the drill 2, over a certain radius R2 inwards.The outer section 26 either borders directly on the center 12 or is between the center 12 and the outer section 26 as in . Fig. 1, a further, likewise annular central section 30 is arranged. Center 12, central section 30, and outer section 26 are arranged concentrically here. The radius R2 of the outer section 26, i.e., its thickness, and thus the length of the additional cutting edge 22, are 0.1 to 0.5 times the total radius Rg.

[0039] Analogous to the main cutting edge 8 and its cutting edge 10, a secondary cutting edge 20 is also connected to the additional cutting edge 22, specifically to its additional cutting edge 24. This also generally runs in the axial direction A, here spirally around the longitudinal axis L. The secondary cutting edges 20 are particularly Fig. 2 recognizable.

[0040] In the present case, the additional cutting edge 24 protrudes beyond the cutting edge 10. This means that, when viewed at the main cutting edge 8 opposite the direction of rotation U, the additional cutting edge 24 is not completely concealed by the cutting edge 10 and disappears behind it, but rather that the additional cutting edge 24 protrudes and thereby forms a projection 32, 34 relative to the cutting edge 10, which projection trails the cutting edge 10. In this case, the additional cutting edge 22 also partially or completely protrudes relative to the main cutting edge 10.

[0041] In the embodiment shown, the additional cutting edge 24 projects beyond the cutting edge 10 in an axial direction A, i.e., along the longitudinal axis L. At the additional cutting edge 24, the drill 2 therefore has a greater length than at the cutting edge 10. This results in a length difference, which here amounts to 0.05 mm to 2 mm and is also referred to as axial projection 32. In addition, the additional cutting edge 24 also projects beyond the cutting edge 10 in a radial direction R, i.e., perpendicular to the longitudinal axis L. Analogous to the length difference in the axial direction A, the drill 2 then has a larger radius Rg at the additional cutting edge 24 than at the cutting edge 10. This results in a radius difference, which here amounts to 0.05 mm to 2 mm and is also referred to as radial projection 34. Fig. 2 and Fig. 4, both projections 32, 34 are indicated by a dashed line below the additional cutting edge 22 and additionally the radius and length difference are indicated by two arrows each.

[0042] The radial projection 34 and the axial projection 32 can also be realized independently of one another, so that the additional cutting corner 24 then projects beyond the cutting corner 10 either in the radial direction R or in the axial direction A.

[0043] The cutting edge 10 is generally a component of the main cutting edge 8 and forms its end in the radial direction R and toward the outside. Similarly, the additional cutting edge 24 is generally a component of the additional cutting edge 22 and forms its end in the radial direction R and toward the outside. In principle, various suitable configurations exist for the cutting edge 10 and the additional cutting edge 24.

[0044] For example, in the illustrated embodiment, the additional cutting edge 24 is rounded and forms a corner cutting edge itself. The rounded additional cutting edge 24 is largely identical to the additional cutting edge 22. As shown in Fig. As shown in Figure 4, the additional cutting corner 24 is an outer partial cutting edge of the additional cutting edge 22. An inner partial cutting edge 36 adjoins the inside, which together with the corner cutting edge then forms the additional cutting edge 22. For example, the inner partial cutting edge 36, as in the illustrated embodiment, is a straight continuation of a rounded outer partial cutting edge. In a variant not shown, however, the rounded additional cutting corner 24 corresponds exactly to the additional cutting edge 22, i.e., is identical to it and does not have an inner partial cutting edge 36.

[0045] In the illustrated embodiment, the additional cutting edge 24 is rounded in that it has a corner radius R3 of 0.4 mm to 5 mm. The additional cutting edge 24 is continuous overall. The transition from the additional cutting edge 24 to the secondary cutting edge 20, however, is formed here as a corner 38.

[0046] In an alternative not shown, the additional cutting edge 24 is not rounded, but rather is pointed. In this case, the additional cutting edge 24 then runs predominantly radially outward and meets the secondary cutting edge 20 at a specific angle. In the pointed configuration, a corner 38 is formed at the end of the additional cutting edge 22 with the additional cutting edge 24.

[0047] In the illustrated embodiments, both the cutting corner 10 and the additional cutting corner 24 are rounded. A mixed configuration, in which the cutting corner 10 is rounded and the additional cutting corner 24 is pointed, or vice versa, is also possible in principle. In the illustrated embodiment, the cutting corner 10 and the additional cutting corner 24 are even formed with the same shape, i.e., they each have a contour that then has the same profile but is of different sizes. The additional cutting corner 24 is accordingly an enlarged version of the cutting corner 10 and therefore protrudes accordingly.

[0048] In the illustrated embodiment, the cutting corner 10 and the additional cutting corner 24 form an angle W which is less than 90°. The angle W is explicitly defined in Fig.1. The angle W determines what proportion of the machining of the workpiece is carried out by the additional cutting edge 24 relative to the cutting edge 10 during one full rotation of the drill 2. The smaller the angle W, the less the additional cutting edge 24 is loaded and the more the cutting edge 10 is loaded. In conjunction with the projection 32, 34, this results in a two-dimensional parameter space in which the distribution of the load is set depending on the two parameters angle W and projection 32, 34.

[0049] In the illustrated embodiment, the drill 2 has two angles W, which are also of equal size. In a configuration not explicitly shown but equally suitable, however, the angles W are of different sizes.

[0050] In the exemplary embodiments shown, a chip groove 40 precedes the main cutting edge 8, via which chip groove 40 chips lifted off by the main cutting edge 8 are carried away rearward in the axial direction A from the drill tip 4. The chip groove 40 extends here over the full length of the main cutting edge 8 and also ends at the center 12. Furthermore, the drill 2 has an additional chip groove 42 which precedes the additional cutting edge 24 and for receiving chips on the additional cutting edge 24 which are generated by this same additional cutting edge 24 and generally by the additional cutting edge 22. The chip groove 42 to the additional cutting edge 22 also has a smaller depth than the chip groove 40 to the main cutting edge 8 and therefore projects less deeply into the base body 6. This leaves space for an optional coolant channel 44, which in the embodiment shown is arranged between the main cutting edge 8 and the chip groove 42 to the additional cutting edge 22, viewed in the direction of rotation U.Both chip grooves 40, 42 are spiral in this case.

[0051] As can be seen in the figures, the main cutting edge 8 is adjoined by a clearance surface 46 which slopes downwards in the direction of the additional cutting edge 24 and merges into a secondary clearance surface 48 which rises towards the additional cutting edge 24. The clearance surface 46 and the secondary clearance surface 48 give the drill tip 4 a depression which is arranged between the main cutting edge 8 and the center 12 on the one hand and the additional cutting edge 22 and the additional cutting edge 24 on the other hand and which prevents the drill tip 4 from rubbing against the workpiece during operation. In the present case, the additional cutting edge 22 ends towards the center 12 at the secondary clearance surface 48, which is thus arranged between the center 12 and the additional cutting edge 22. The secondary clearance surface 48 shapes the end of the additional cutting edge 22.

[0052] The flank surface 46 is bordered in the leading direction by the main cutting edge 8. The flank surface 46 is bordered in the trailing direction by the point thinning 16 in the center 12. Towards the outer edge 18, the flank surface 46 is bordered in a trailing direction by the chip groove 42 to the additional cutting edge 22. The secondary flank surface 48 is then arranged between the point thinning 16 and the chip groove 42. This flank surface then also borders the flank surface 46 in a trailing direction. While the drill tip 4 continues to slope downwards from the flank surface 46 into the chip groove 42 to the additional cutting edge 22 and into the point thinning 16, the secondary flank surface 48, in contrast, creates a rise such that the additional cutting edge 24 is correspondingly projecting. In this case, the secondary flank surface 48 also transitions downwards into the point thinning 16 and in the leading direction into the chip groove 42 to the additional cutting edge 22.

[0053] In principle, the drill 2 can have a plurality of main cutting edges 8, one, several, or all of which are followed by one or more additional cutting edges 22. In the illustrated embodiment, the drill 2 has exactly two main cutting edges 8, each with a cutting edge 10, each of which is followed by exactly one additional cutting edge 24, more precisely, an additional cutting edge 22 with an additional cutting edge 24.

Claims

[1] Drill (2) having a drill bit (4), - wherein the drill bit (4) has at least one main cutting edge (8) with a cutting edge (10) from which the main cutting edge (8) extends to a center (12), - wherein the drill bit (4) has at least one additional cutting edge (22) with an additional cutting edge (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 section (26) of the drill tip (4) and is therefore shorter than the main cutting edge (8), - wherein the additional cutting corner (24) projects beyond the cutting corner (10) to distribute the load between the cutting corner (10) and the additional cutting corner (24). [2] Drill (2) according to claim 1, wherein the additional cutting edge (24) projects beyond the cutting edge (10) in an axial direction (A). [3] Drill (2) according to claim 1 or 2, wherein the additional cutting edge (24) projects beyond the cutting edge (10) in a radial direction (R). [4] Drill (2) according to one of claims 1 to 3, wherein the additional cutting edge (24) is rounded. [5] Drill (2) according to one of claims 1 to 3, wherein the additional cutting edge (24) is pointed. [6] Drill (2) according to one of claims 1 to 5, wherein the cutting corner (10) and the additional cutting corner (24) are formed with the same shape. [7] Drill (2) according to one of claims 1 to 6, wherein the cutting corner (10) and the additional cutting corner (24) enclose an angle (W) which is less than 90°. [8] Drill (2) according to one of claims 1 to 7, wherein said cutter has a plurality of main cutting edges (8) each with a cutting corner (10), each of which is followed by an additional cutting corner (24) which forms an angle (W) with the cutting corner (10), so that a plurality of angles (W) are formed, where the angles (W) are of different sizes. [9] Drill (2) according to one of claims 1 to 8, wherein it has a chip groove (42) which runs ahead of the additional cutting edge (24) for receiving chips on the additional cutting edge (24). [10] Drill (2) according to one of claims 1 to 9, wherein the main cutting edge (8) is adjoined by a clearance surface (46) which slopes down in the direction of the additional cutting edge (24) and merges into a secondary clearance surface (48) which slopes up towards the additional cutting edge (24). [11] Drill (2) according to one of claims 1 to 10, wherein the additional cutting edge (24) ends at a secondary flank (48) towards the center (12). [12] Drill (2) according to one of claims 1 to 11, wherein it has exactly two main cutting edges (8) each with a cutting edge (10), which are each followed by exactly one additional cutting edge (24).

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