Drilling tools

Abstract

A drilling tool comprising two main cutting edges (2) connected to each other via side cutting edges (6) and arranged in a partially arcuate shape, a drill face (4), a drill longitudinal axis (L) about which a drilling tool (1) rotates in a rotation direction (R), a drill bit (3) located on the drill longitudinal axis (L), two longitudinal flutes (5) extending along the drill longitudinal axis (L), a web (7) forming a back surface (8) at the peripheral edge and formed between the longitudinal flutes (5), and a web thin-walled portion (12) provided on the drill face (4), wherein an opening angle (φ) of the longitudinal flutes (5) is formed on the front face of the drill face (4), The opening angle is, in the case of grinding the conical surface of the drill face (4), a virtual connection of the drill bit (3) to the cutting corner (9) of the main cutting edge (2); defined as spanning between the imaginary connection of the drill bit (3) to the land edge (10) formed in the land (8) at the transition of the flank (11) to the flute (5); In the case of surface grinding of the drill face (4), a virtual connection of the drill bit (3) to the cutting corner (9) of the main cutting edge (2); the web thinning (12) is defined as being stretched between the radially outwardly extending portion of the contour (14) of the web thinning (12), the opening angle (φ) of which is between 85° and 95°, the web thinning (12) being introduced into the drill face (4) in such a way that the nominal spacing (NA) of the internal points of the web thinning (12) relative to the imaginary connection of the drill bit (3) with the cutting corner (9) is equal to or less than the nominal spacing (NU) of the transition points (U) between the main cutting edge (2) and the side cutting edge (6) adjacent to the web thinning (12) relative to the imaginary connection of the drill bit (3) with the cutting corner (9), and the web thinning (12) starts from the transition point (U) and meets the adjacent main cutting edge (2) without any bends; Drilling tools.

Description

[Technical Field]

[0001] The present invention relates to a drilling tool having the features of the preamble of claim 1. Furthermore, a method for manufacturing this drilling tool is presented. [Background technology]

[0002] A drilling tool of this type is known, for example, from DE 10 200 094 14 5, in which a good chip removal is achieved in that the chip outflow shoulder of the web thin-walled section has an axial angle that continuously decreases with increasing distance towards the web from the central axis. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] European Patent No. 3038776(B1) Summary of the Invention [Problem to be solved by the invention]

[0004] The object of the present invention is to provide an improved drilling tool. In particular, the drilling tool should be easily manufacturable with little grinding work. In particular, the improved drilling tool should achieve advantageous chip removal with low machining forces. [Means for solving the problem]

[0005] This problem is solved by a drilling tool having the features of claim 1. The drilling tool according to the present invention comprises: two main cutting edges connected to each other via side cutting edges and having an at least partially arcuate arrangement; a drill face; and a drill longitudinal axis about which the drilling tool is rotated in a rotational direction; a drill bit located on the longitudinal axis of the drill; at least two flutes extending along the drill longitudinal axis; a web formed between the longitudinal flutes and having lands formed at the peripheral edge; a thin web portion provided on the drill surface; and A longitudinal groove opening angle is formed on the drill face at the front surface of the drill face; This opening angle is, in the case of conical outer mantle grinding of the drill face, a virtual connection of the drill bit to the cutting corner of the main cutting edge; a virtual connection of the drill bit to a land edge formed on the land at the transition to the flute on the flank; It is stretched between In the case of surface grinding of drill faces, a virtual connection of the drill bit to the cutting corner of the main cutting edge; a portion extending radially outward from the contour of the thin-walled portion of the web; It is stretched between The aperture angle is 85° to 95°. The web thinning is introduced into the drill face in such a way that the standard spacing of the internal points of the web thinning relative to the imaginary connection of the drill bit with the cutting corner is less than or equal to the standard spacing of the transition points between the main and side cutting edges adjacent to the web thinning relative to the imaginary connection of the drill bit with the drill bit, so that the web thinning starts from the transition point and adjoins the adjacent main cutting edge without any bends.

[0006] "Surface grinding" means grinding with flat flank facets, especially four-sided grinding.

[0007] The interaction of the small opening angle between 85° and 95° according to the present invention and the web thinning extending far toward the center ensures particularly good axial removal of chips in the center of the drilling tool. This feature, in particular, ensures that chips removed from the radially inner side of the web thinning are guided directly axially along the longitudinal axis into the flutes. Therefore, chips removed from the radially inner side do not reach the deep radially outer portion of the flutes at all. As a result, chips can be effectively removed, especially near the center. Furthermore, chips guided directly in the axial direction generate only slight friction on the chip face of the drilling tool.

[0008] Due to the different spatial cutting curves that occur in connection with the grinding of the web thinnings and flanks, the definition of the opening angle is specified in connection with the respective grinding.

[0009] It is preferred that the web thinnings extend further in the direction of the imaginary connection to the cutting corner of the drill bit than the transition point adjacent to the web thinning between the main cutting edge and the side cutting edge. In other words, it is advantageous for the web thinnings to extend further beyond the side cutting edge into the center of the drilling tool than the transition point associated with said web thinning between the main cutting edge and the side cutting edge. In other words, the web thinnings protrude further in the direction of the central parting plane extending from the connection between the cutting corner and the longitudinal axis than the transition point between the main cutting edge and the side cutting edge. These circumstances are particularly evident at the front face of the drill face.

[0010] The web thinning is formed in particular in a single grinding operation, which is associated with the advantage that production is particularly economical. The web thinning is preferably single-sided. In this connection, it is advantageous if the surface of the thin-walled portion of the web is edge-free and therefore has particularly low friction. In production, this means that the introduction with the grinding tool can be carried out in a particularly stepless manner in the grinding operation.

[0011] In particular, the web thinning from the direction of the associated cutting corner to the adjacent main cutting edge is curved only immediately after the transition point. Advantageously, at the transition point, the main cutting edge and the web thinning have the same tangent (to the front face of the drill face). Immediately after the transition point, the web thinning proceeds in a concave curve. "Concave" here should be interpreted in relation to the convexly curved main cutting edge, i.e., the main cutting edge curves in the direction of the flute, while the web thinning curves in the opposite direction. From this perspective, the transition point is preferably an inflection point. In particular, the main cutting edge extends to the transition point via a straight section.

[0012] The drilling tool is in particular a helical drill having flutes extending in a helical fashion. More preferably, the drilling tool is monolithically formed including a cutting portion and a shank portion. Alternatively, the drilling tool may take the form of a drill head which can be connected to a separate shank. The drilling tool consists of a hard material, in particular a hard metal. A "hard metal" is a composite material consisting of carbides as the hard material phase and a tough metal belonging to the iron group (Fe, Co, Ni) as the binder phase. In particular, the hard material particles are constituted by tungsten carbide. In the case of hard metals, the binder is generally cobalt (Co). However, other metals or alloys are also considered as binders. In common English terminology, hard metals are often also called "cemented carbides". Particularly preferably, the drilling tool takes the form of a fully hard metal (VHM) tool.

[0013] The two main cutting edges are arranged at least partially in an arcuate fashion. In particular, the main cutting edges are convexly curved. "Convex" in this context means that the main cutting edges are curved into the assigned longitudinal flutes.

[0014] In particular, the main cutting edge is formed so as to lead into the side cutting edge via a straight section, which then forms an end / bend with the likewise straight side cutting edge against the front face of the drill face. Therefore, the main cutting edge exhibits only a slight curvature, preferably close to the center, and is preferably constituted by a straight section close to the center. By virtue of the slight curvature close to the center, or more preferably by the straight section close to the center, a low cutting force is achieved close to the center. As a result, only a low torque acts on the drilling tool. The web thinnings are preferably arranged at least partially in an arcuate shape, with the apex of the arcuate shape having a maximum curvature. The radial position of the apex relative to the drill bit is typically located between 0.02 x BR and 0.1 x BR, where BR is half the drill diameter. The apex is typically located between 0.03 x BR and 0.07 x BR. This indicates that the maximum curvature of the web thinning is particularly close to the center. Because the maximum curvature of the web thinning is located very close to the center, chip bypass occurs at low orbital speeds, with associated low friction and low torque.

[0015] Advantageously, a tangent is constructed at the apex of the thinned portion of the web, and the normal to the tangent to the imaginary connection of the drill bit and the cutting corner makes an angle of 60° to 70°. This allows the web thinning to have a settable main direction of extension above the maximum curvature, at an angle of 60°-70° relative to the imaginary connection between the drill bit and the cutting corner assigned to it. At the maximum curvature, a particularly strong chip deflection always occurs. The favorable position of the maximum curvature results in low torques and therefore low machining forces. The favorable position of the main direction of extension in the region of the web thinning allows for particularly good chip removal close to the center of the flute.

[0016] Advantageously, the axial angle of the web thinning, measured relative to the drill longitudinal axis, is between 30° and 40°. In particular, the axial angle of the web thinning is 35° ± 1°. The axial angle of the web thinning is a measure of the axial "steepness" of the web thinning. A progression that is too flat, i.e., an axial angle of, for example, 45° or more, impairs chip removal into the groove. A progression that is too steep, i.e., an axial angle of, for example, 25° or less, elongates the web thinning and results in a grinding cut at the transition of the web thinning to the land, which is unfavorable for chip collection.

[0017] The above-mentioned preferred magnitude of the axial angle of the web thinning is obtained particularly in the region where the web thinning extends radially outward, and in particular extends radially outward linearly. More preferably, the axial angle of the web thinning is constant along the radial progression of the web thinning.

[0018] The object of protection is the following grinding process in which a thinned portion of the web is introduced onto the drill face and a grinding tool is used: i) forming a thinned portion of the web near the center, the apex of which has an angle of 60° to 70° with respect to the normal to the tangent; ii) forming adjacent portions of the web thinned portion by linear radial outward movement of the grinding tool; The present invention is also directed to a method for manufacturing a drilling tool, including: forming a radius near the center of the web thinning; and then guiding a grinding tool radially outward through a linear grinding path. The linear path is preferably oriented at an angle of 85° to 95° relative to the connection between the drill bit and the cutting corner. It will be apparent to those skilled in the art that additional operations are required to manufacture the drilling tool. Only the steps related to forming the web thinning are considered herein.

[0019] Further advantages and effectiveness of the present invention will become apparent from the following description of the preferred embodiments with reference to the accompanying drawings. [Brief explanation of the drawings]

[0020] [Figure 1a] 1 shows a drilling tool according to a first embodiment in different views; [Figure 1b] 1 shows a drilling tool according to a first embodiment in different views; [Figure 1c] 1 shows a drilling tool according to a first embodiment in different views; [Figure 1d] 1 shows a drilling tool according to a first embodiment in different views; [Figure 2a] 2A and 2B show a drilling tool according to a second embodiment in different views. [Figure 2b] 2A and 2B show a drilling tool according to a second embodiment in different views. [Figure 3] 1 shows a schematic diagram of a manufacturing method for conical surface grinding. [Figure 4] A schematic diagram of the manufacturing method for four-sided grinding is shown. DETAILED DESCRIPTION OF THE INVENTION

[0021] 1a shows a drilling tool 1 according to a first embodiment in a front view of the drilling tool 1, which is shown as a drill face 4. The viewing direction runs parallel to the longitudinal axis L of the drilling tool 1, which also represents the central axis, and is therefore projective in this view. The drill face 4 is formed with two main cutting edges 2 connected to each other via side cutting edges 6. The drilling tool 1 according to the invention is a two-cutter having two main cutting edges 2 .

[0022] The main cutting edge 2 preferably exhibits a shape that is curved in the direction of rotation R. In other words, the main cutting edge 2 is curved in an arc shape, the apex of the arc shape extending in the direction of rotation R. It is therefore referred to as a convex main cutting edge 2. The (at least partially) arc shape of the main cutting edge 2 provides a robust cutting edge and gentle cutting. The main cutting edge 2 preferably exhibits an overall S-shaped configuration. The main cutting edges 2 preferably transition into the side cutting edges 6 via straight sections, i.e. each main cutting edge 2 preferably comprises a radially outer arcuate section and a radially inner straight section. The drilling tool 1 is rotatable along its longitudinal axis L, the direction of rotation being indicated by R in this case. The drilling tool 1 of the present invention is therefore right-handed. The present invention can also be applied to left-handed tools. In front of the main cutting edges 2 in the direction of rotation R, there are longitudinal flutes 5, which extend at a helix angle along the longitudinal axis L. Further inside, the outlet openings of the coolant passages IK are shown, although their placement may be optional. The most distal end of the side cutting edge 6 constitutes the drill bit 3 located on the longitudinal axis L.

[0023] In particular, the drilling tool 1 is equally divided, i.e. the main cutting edges 2 are distributed over 180°. The junction of the opposing cutting corners 9 comprises the drill bit 3. Furthermore, the two main cutting edges 2 are preferably configured identically, and are referred to as symmetrical drilling tools 1.

[0024] The webs 7 are formed between the longitudinal grooves 5. The lands 8 are arranged on the outer periphery of the webs. In this embodiment, a guide chamfer 13 is formed, which is located on the drilling diameter D. In contrast, the lands 8 are reset on the land diameter DR. Adjacent to the rear of each main cutting edge 2 in the direction of rotation R is a flank 11. In this example, the drill face 4 is conically ground, i.e. the flank 11 is formed by a segment of a cone. The flank 11 on the drill face 4 is provided with a web thinning 12 which reduces the side cutting edge 6 to the desired size.

[0025] The flank 11 extends peripherally from the cutting corner 9 to a rear corner 10 where the flank 11 meets and terminates the flute 5. In other words, the rear corner 10 on the front side of the drill face 4 is the point on the periphery where the land 8 intersects with the contour 14 of the web reduction 12. The line of intersection between the web reduction 12 and the flank 11 is referred to as the contour 14 of the web reduction 12.

[0026] The contour 14 of the web thinning 12 also indicates the transition of the flank 11 to the flute 5. The web thinning 12 is considered to belong to the flute 5.

[0027] In this front view of the drill face 4, the opening angle φ of the flutes 5 can be defined on the drill face 4, this opening angle φ being: the imaginary connection of the drill bit 3 to the cutting corner 9 of the main cutting edge 2 and following it in the direction of rotation R, the imaginary connection of the drill bit 3 to the rear corner 10 formed at the transition of the flank 11 to the longitudinal groove 5 at the land 8; The opening angle φ ranges between 85° and 95°. This specification of the opening angle φ applies to drilling tools with conical surface grinding. The opening angle φ is preferably 90°±2°. In this embodiment and the following embodiments, the preferred opening angle is 90°. It should be noted that the curved shape of the web thinning 12 along the contour 14 is in this example caused by the conical shape of the drill face 4. When forming the web thinning 12 by grinding, the grinding disk preferably follows a straight path from radially inside to outside, preferably at a constant height relative to the longitudinal axis L.

[0028] Considered further, a dividing plane E dividing the drilling tool in the middle is defined to include the junction of the longitudinal axis L and the cutting corner 9 .

[0029] The web thinning 12 begins at a cutting point indicated as U, which is the transition point between the main cutting edge 2 and the side cutting edge 6 adjacent to the web thinning 12 . The web thinning 12 is formed in such a way that, with respect to the standard distance to the imaginary connection between the drill bit 3 and the cutting corner 9, it extends towards the centre, i.e. towards the parting plane E of the drilling tool 1, at least as far as the transition point U. In particular, the web thinning 12 extends further in the direction of the imaginary connection between the drill bit 3 and the cutting corner 9 than the transition point U. In other words, the web thinning 12 projects further in the direction of the parting plane E than the transition point U connected to the web thinning 12. In other words, the web thinning 12 projects beyond the side cutting edge in the direction of the parting plane E.

[0030] The protrusion of the web thinned portion 12 creates additional chip space near the center. Furthermore, the combination of the opening angle φ and the special shape of the thin web portion 12 allows for effective chip removal. Because the web thinned portion 12 extends toward the center and exhibits maximum curvature near the center, the tip experiences a strong deflection near the center and is guided by the flutes 5 near the center. As a result, most of the tip deflection occurs at low orbital velocities, resulting in little force. The favourable evacuation of chips in combination with the increased chip space in the centre of the drilling tool 1 significantly reduces the cutting forces and therefore the mechanical load on the tool and workpiece.

[0031] In the region of the side cutting edge 6, the web thinning 12 is unbent and in particular faces tangentially away from the main cutting edge 2. In other words, at the transition point U the web thinning 12 is unbent and in particular faces tangentially towards the adjacent main cutting edge 2. A "tangential" transition means that, according to this preferred embodiment, the main cutting edge 2 and the contour 14 of the web thinning 12 have the same tangent at the transition point U. The twist-free, especially tangential transition between the main cutting edge 2 and the web thinning 12, ensures a particularly smooth and uniform chip formation.

[0032] Figure 1b shows a side view of the drilling tool 1 of Figure 1a. In this figure, the rear corner 10 can advantageously be defined as the intersection of the rear end 15 of the land 8 with the contour 14 of the web thinned portion 12, which contour 14 marks the transition to the relief surface 11 to the longitudinal groove 5.

[0033] In FIG. 1b, the axial angle γ of the web thinned portion 12 measured relative to the drill longitudinal axis L is further marked. Advantageously, the axial angle γ of the web thinnings 12 is between 30° and 40°. In particular, the axial angle of the web thinnings is 35°±2°, more preferably 35°±1°. The axial angle is measured in particular in the region of the web thinnings 12, where the web thinnings 12 extend radially outward, in particular along straight sections.

[0034] FIG. 1c shows a detail of FIG. 1a, ie the front view of the drill face 4 along the longitudinal axis L. This detailed view further reveals the particularity of the web thinning 12 according to the invention. According to the invention, the web thinning 12 extends towards the centre, such that the standard spacing NA of the inner point of the web thinning 12 relative to the imaginary connection between the drill bit 3 and the cutting corner 9 is less than or equal to the standard spacing NU of the transition point U between the main cutting edge 2 and the side cutting edge 6 adjacent to the web thinning 12 due to the imaginary connection between the drill bit 3 and the cutting corner 9 (not shown). In other words, the contour 14 of the web thinning 12 extends towards the centre of the drilling tool 1 at least as far as the transition point U adjacent to the web thinning 12. Advantageously, the contour 14 of the web thinning 12 extends further towards the centre than the transition point U. In other words, the web thinning extends "behind" the side cutting edge 6. The distance from the centre is measured as the standard spacing from the parting plane, not necessarily relative to the drill bit 3. Furthermore, the main extending direction of the web thin-walled portion 12 can be defined as follows. That is, web thinning 12 has a vertex S near the center where the curvature of profile 14 of web thinning 12 may be greatest. If web thinning 12 is continuously curved as it approaches the center, for example along a radius of curvature, vertex S may be defined at the center of the continuous arcuate arrangement. A tangent line T can be defined at this vertex S. A tangent line reference point TN perpendicular to the tangent line T defines the main direction of extension of the web thinned portion 12. At the transition point U between the corresponding main cutting edge 2 and side cutting edge 6, the web thin-walled portion 12 adjoins the main cutting edge 2 without bending, but at this transition point U the main cutting edge 2 and the web thin-walled portion 12 show a common tangent line TU at the transition point U (as is clear from the contour line 14 in the selected front view).

[0035] Figure 1d again shows the same embodiment in a front view of the drill face 4. For clarity, further aspects of the invention will be described using this alternative view. Similarly, for ease of understanding, not all reference numbers are included.

[0036] Thus, the web thinned portion 12 exhibits a groove having a radius of curvature near the center. The radius of curvature (r) of the web thinned portion 12 at the vertex S is preferably between 0.06 and 0.09 x D, where D is the perforation diameter. More preferably, the radius of curvature r of the web thinned portion 12 is 0.07 to 0.08 x D, especially 0.075 x D. Alternatively, a circle of curvature having the radius of curvature (r) is inscribed as a radius.

[0037] The tangent TU to the main cutting edge 2 at the transition point U with the imaginary connection between the drill bit 3 and the cutting corner 9 is preferably at an angle α between 10° and 30°. TU , more preferably between 15° and 25°, and even more preferably between 17° and 23°. TU In particular, the angle α TU is 20°±2°.

[0038] The main extension direction of the web thinning portion 12, defined by the normal TN, forms an angle α between 30° and 60° with the tangent TU at the transition point U. TN , in particular between 40° and 50°, more preferably between 42° and 48°. TN Including angle α of 45°±2° TN has proven to be particularly advantageous, especially with regard to chip removal from the radially inner part of the main cutting edge 2 .

[0039] More preferably, the main direction of extension of the web thinning 12, defined by the normal TN, subtends an angle between 60° and 70° with an imaginary connection between the drill bit 3 and the cutting corner 9. In particular, this angle is 65°±2°. This direction has been found to be particularly favorable for near-center chip deflection and removal. Additionally, an outer dimension a beyond the center of web thinning 12 can be specified. The beyond-center dimension (a) specifies how far web thinning 12 maximally extends above an equatorial plane A that is 90° to parting plane E and contains longitudinal axis L. In this embodiment, where the opening angle φ is 90°, the track on the equatorial plane A coincides with the junction of the two opposing rear corners 10. The dimension (a) beyond the center of the web thinned portion 12 is preferably 5% to 15% of the drill diameter D, more preferably 10% ± 2% of the drill diameter D.

[0040] The main cutting edge 2 preferably extends into the transition point U via a straight section, whereby the main cutting edge 2 and the side cutting edge 6 form a twist at the transition point U.

[0041] The side cutting edge 6 preferably subtends an angle between 50° and 70°, in particular 60°±2°, at the imaginary junction between the drill bit 3 and the cutting corner 9 .

[0042] In conjunction with the above-mentioned preferred arrangement of the main cutting edge 2 at the transition point U, it is particularly preferred that the main cutting edge 2 and the side cutting edge 6 form an external angle of 140°±4° at the transition point U.

[0043] The drilling tool 1 is particularly symmetrically formed, i.e. the geometrical features described above apply to both flutes 5. In other words, the drilling tool 1 can be displaced on itself by rotating it along its longitudinal axis L by 180°.

[0044] 2a and 2b show various aspects of a drilling tool 1 according to a further embodiment. Figure 2a shows a front view of the drill bit 4 of the drilling tool 1 according to the invention. In this embodiment, the drill surface 4 is so-called four-sided ground. In the case of four-sided grinding, the flank 11 comprises two partial facets 11a and 11b. The partial facets 11a, 11b of the flank 11 have different clearance angles. The facets 11a, 11b of the flank 11 are preferably flat, i.e. not curved. The opening angle φ is, for grinding with flat flank facets as in the four-sided grinding here, the imaginary connection between the drill bit 3 and the cutting corner 9 of the main cutting edge 2 assigned to it, a portion extending radially outward of the contour 14 of the web thin-walled portion 12; and the aperture angle φ is 85° to 95°. The aperture angle φ is preferably 90°±2°. In this embodiment, the aperture angle is more preferably 90°.

[0045] The radially outwardly extending portion of the contour 14 of the web thinning 12 refers to the portion of the web thinning 12 adjacent to the bend near the center of the web thinning 12 and extending generally radially outward in a straight line with a flat relief facet for grinding. In the case of a drilling tool 1 having an abrasive surface, it is advantageous for the contour 14 of the web thin-walled portion 12 to have at least partially a straight portion on the front surface of the drill face 4, which in this case is advantageously used as a second clue to define the opening angle φ.

[0046] Such straight portions are produced by, for example, a straight grinding path during the manufacturing process of the web thinned portion 12 by a grinding tool.

[0047] In particular, the profile 14 of the web thinned portion 12 has a radially outer straight portion 14a. The radially outer linear portion 14a of the web thinning 12 refers to the linear portion 14a of the contour 14 of the web thinning 12 through which the web thinning 12 leads to the rear corner 10. This linear portion 14a is used as a second clue in determining the opening angle φ.

[0048] For the sake of clarity, the web thinning 12 is formed in particular in the following way: the grinding disk first reproduces the radially inner radius of the web thinning 12 and then generates the remaining contour 14 of the web thinning 12 along a linear path from the radially inner to the outer side, preferably at a constant height relative to the longitudinal axis L. Since the web thinning 12 in this example is guided into the flat flank 11, the linear path of the grinding disk is also reproduced as a linear portion of the contour 14 of the web thinning 12.

[0049] In this embodiment involving grinding with flat flank facets, the center outer dimension a of the web thinned portion 12 can also be specified as follows: That is, the dimension (a) beyond the center specifies the maximum extent of the web thinned portion 12 on the equatorial plane A which is at 90° to the parting plane E and contains the longitudinal axis L. The central outer dimension (a) of the web thin-walled portion 12 is preferably 5% to 15% of the perforation diameter D, and more preferably 10%±2% of the perforation diameter D.

[0050] The configuration of the web thinning 12 is similar to the previously described embodiment with conical surface grinding. In particular, the details regarding the curvature, the main direction of extension and the preferred dimensions of the web thinning 12 apply to all embodiments, whether the drilling tool 1 has a conical surface grinding or a surface grinding with flank facets.

[0051] In FIG. 2b, the axial angle γ measured relative to the longitudinal drill axis L of the web thinning 12 is further marked. Advantageously, the axial angle γ of the web thinning 12 is between 30° and 40°. In particular, the axial angle of the web thinning is 35°±1°. The axial angle of the web thinning is a measure of the axial "steepness" of the web thinning. All the above-mentioned developments and advantages apply equally to all embodiments.

[0052] 3a) to 3f) show a preferred method for forming the web thinning 12 in a drilling tool 1 with a conical surface grinding. For better understanding, the contour of the web thinning 12 is already shown from the beginning. Naturally, the contour of the web thinning 12 results only from the sequence of operations shown here to introduce the web thinning 12. For clarity, the reference numerals are assigned only to the individual figures. The grinding tool 16 (in this case a grinding disk) is first moved towards the drill bit 3. The rotation of the grinding tool 16 is carried out along the axis of rotation D S occurs along the Next, the portion near the center of the thin web portion 12 is ground so that the apex S of the thin web portion is positioned "rear" of the intersection between the side cutting edge 6 and the main cutting edge 2 (see steps d) to e) in the figure) relative to the dividing plane E. Finally, the grinding tool 16 is guided radially outward along the linear grinding path of step f) in the figure.

[0053] 4a) to 4f) show a preferred method for introducing the web thinning 12 in the case of a drilling tool 1 for four-sided grinding. The sequence of operations is the same as that described with reference to FIGS. 3a) to 3f). Repetition of symbols is omitted. Due to the planar relief surface, the radially tapered profile 14 of the web thinning 12 is shown here as a straight line. [Explanation of symbols]

[0054] 1 Drilling tools 2 Main cutting edge 3 drill bits 4 Drill Surface 5 Vertical grooves 6 Side cutting edge 7. Web 8 rand 9 Cutting Corner 10 rear corners 11 Flank 12 Thin-walled web 13 Guide chamfer 14 Thin-walled web contour 15 Rear end of land 16 Grinding tools

Claims

1. two main cutting edges (2) which are at least partially arranged in an arcuate shape and which are connected to each other via side cutting edges (6); a drill surface (4) and a drill longitudinal axis (L) about which the drill tool (1) can rotate in a rotation direction (R); a drill bit (3) arranged on the drill longitudinal axis (L); two flutes (5) extending along the drill longitudinal axis (L); a web (7) formed between the longitudinal grooves (5) and having lands (8) formed around its periphery; a web thinning portion (12) provided on the drill surface (4), forming a land (8) in a circumferential direction, the drill surface (4) being provided with the web thinning portion (12), and the opening angle (φ) of the longitudinal flutes (5) being formed on the drill surface (4) with respect to a front surface of the drill surface (4); In a drilling tool comprising: In the case of conical surface grinding, the drill face (4) is defined as being bridged between the imaginary connection between the drill (3) and the cutting angle (9) of the main cutting edge (2) and the imaginary connection between the drill bit (3) and the rear corner (10) formed on the land (8) at the transition of the flank (11) to the flute (5), In the case of surface grinding, the drill surface (4) is defined as being between the imaginary connection of the drill bit (3) with the cutting angle (9) of the main cutting edge (2) and the radially outwardly extending cross section of the contour (14) of the web thinning (12); The aperture angle (φ) is 85° to 95°, the web thinning (12) is introduced into the drill face (4) in such a way that the nominal distance (NA) of an inner point of the web thinning (12) from the imaginary connection of the drill bit (3) to the cutting corner (9) is less than or equal to the nominal distance (NU) from the imaginary connection of the drill bit (3) to the cutting corner (9) to the transition point (U) between the main cutting edge (2) and the side cutting edge (6) adjacent to the web thinning (12); the web thinned portion (12) starts from the transition point (U) and is connected to the adjacent main cutting edge (2) without bending; Drilling tools.

2. 2. The drilling tool (1) according to claim 1, wherein the web thinning (12) extends further in the direction of the imaginary connection of the drill bit (3) with the cutting corner (9) than the transition point (U) between the main cutting edge (2) and the side cutting edge (6) adjacent to the web thinning (12).

3. 3. The drilling tool (1) according to claim 1 or 2, wherein the web thin-walled portion (12) is continuous in an arc shape with its apex (S) at least in cross section relative to a front view of the drill face (4), and the radial position of the thin-walled portion (12) starting from the drill bit (3) is between 0.1 x BR and 0.33 x BR, where BR is half the drill diameter (D).

4. 4. The drilling tool (1) according to claim 1, wherein the transition point (U) between the main cutting edge (2) and the side cutting edge (6) constitutes an inflection point with respect to the curvature of the web thin-walled portion (12).

5. 5. The drilling tool (1) according to any one of claims 1 to 4, wherein the web thinning (12) and the main cutting edge (2) present a common tangent (TU) at a transition point (U) between the main cutting edge (2) and the side cutting edge (6).

6. At the vertex (S) of the web thinning (12), a tangent line can be formed, the normal (TN) of which defines the main direction of extension of the web thinning (12) and which forms an angle (α) of between 30° and 60° with a tangent line (TU) at the transition point (U) between the main cutting edge (2) and the side cutting edge (6). ＴＮ 6. A drilling tool (1) according to any one of claims 1 to 5, comprising:

7. 7. The drilling tool (1) according to any one of claims 1 to 6, wherein at the vertex (S) of the web thinning (12) it is possible to form a tangent line, the normal (TN) of which forms an angle of between 60° and 70° with respect to the imaginary connection of the drill bit (3) and the cutting corner (9), and which defines the main direction of extension of the web thinning (12).

8. At the transition point (U) between the main cutting edge (2) and the side cutting edge (6), the tangent (TU) to the main cutting edge (2) forms an angle (α) of 10° to 30° with respect to the imaginary connection between the drill bit (3) and the cutting corner (9). ＴＵ 8. A drilling tool (1) according to any one of claims 1 to 7, comprising:

9. 9. The drilling tool (1) according to any one of claims 1 to 8, wherein the web thinned portion (12) exhibits a maximum curvature near the center, the radius of curvature (r) being 0.06 to 0.09 x D, where D is the cutting diameter.

10. 2. A drilling tool (1) according to claim 1, wherein the web thinned portion (12) is formed on one side.

11. 11. The drilling tool (1) according to any one of claims 1 to 10, wherein the web thinning (12) has an axial angle (g) measured relative to the longitudinal drill axis (L) of between 30° and 40°.

12. A method for manufacturing a cutting tool (1), in particular a cutting tool (1) according to any one of claims 1 to 6, comprising the steps of: The web thinning (12) is introduced onto the drill face (4) and, with the grinding tool (16), 1) forming a thinned portion (12) of the web near the center, the thinned portion having a vertex (S) that forms an angle of between 60° and 70° with a normal (TN); 2) forming adjacent portions of said web thinned portion (12) by linearly moving a grinding tool (16) radially outward; A method comprising:

Images