Drilling tool

Abstract

A drilling tool comprising two main cutting edges (2) at least partially having an arcuate travel and connected to each other by a transverse cutting edge (6); a drill rake face (4), a longitudinal drill axis (L) about which the drilling tool (1) can be rotated in a direction of rotation (R); a drill bit (3) located on the longitudinal drill axis (L); two flutes (5) extending along the longitudinal drill axis (L); a drill core (7) formed between the flutes (5), the drill core (7) forming a land (8) in the circumferential direction; a core foil (12) introduced into the drill rake face (4), an opening angle (alpha) of the flute (5) having been formed on the drill rake face (4) with respect to a front view of the drill rake face (4), the opening angle (alpha) being defined in the case of conical grinding of the drill rake face (4) between: an imaginary connection of the drill bit (3) to the cutting corner (9) of the main cutting edge (2), and an imaginary connection of the drill bit (3) to the cutting corner (9) of the main cutting edge (2); and an imaginary connection of the drill bit (3) to a relief angle (10) formed on the land (8) at the transition of the flank (11) to the flute (5); in the case of surface grinding of the drill rake face (4), it is defined between an imaginary connection of the drill bit (3) to the cutting corner (9) of the main cutting edge (2) and a radially outwardly extending section of the contour (14) of the core foil (12). The opening angle (alpha) is between 85 DEG and 95 DEG, and the drill core foil (12) has been introduced into the drill rake face (4), the core thin piece (12) is arranged in the drill bit (3) such that a normal distance (NA) of an inner point of the core thin piece (12) from an imaginary connection of the drill bit (3) to the cutting corner (9) is less than or equal to a normal distance (NU) of a transition point (U) between the main cutting edge (2) and the transverse cutting edge (6) adjoining the core thin piece (12) from an imaginary connection of the drill bit (3) to the cutting corner (9), the core thin portion (12) begins at the transition point (U) and adjoins the adjacent main cutting edge (2) in a non-kink manner.

Description

Technical Field

[0001] The invention relates to a drilling tool having the features of the preamble of claim 1. Furthermore, a method for producing the drilling tool is described. Background Art

[0002] A drilling tool of this type is known, for example, from EP 3 038 776 (B1). According to this publication, advantageous chip removal is achieved by the fact that the chip lift shoulder of the thin drill core portion has an axial angle, measured relative to the center axis, which decreases continuously with increasing distance from the front side. Summary of the Invention

[0003] The object of the present invention is to provide an improved drilling tool. In particular, the drilling tool can be advantageously manufactured with minimal grinding operations. In particular, the improved drilling tool exhibits advantageous chip removal under low machining forces.

[0004] This object is achieved by a drilling tool having the features of claim 1 .

[0005] The drilling tool according to the present invention has:

[0006] two main cutting edges which at least partially have an arc-shaped progression and are connected to each other by a transverse cutting edge,

[0007] Drill face, longitudinal drill axis, the drilling tool can rotate in the direction of rotation around the longitudinal drill axis,

[0008] The drill bit, which is located on the longitudinal drill shaft,

[0009] Two flutes extending along the longitudinal drill axis,

[0010] The drill core (web) formed between the chip flutes forms a land in the circumferential direction.

[0011] web thinning introduced into the drill rake face,

[0012] Among them, relative to the front view of the drill rake face, the opening angle (aperture angle) of the chip groove has been formed on the drill rake face, the opening angle:

[0013] In the case of conical surface grinding of the drill rake face, it is defined as being limited between:

[0014] - the imaginary connection of the cutting corner of the drill bit with the main cutting edge, and

[0015] - an imaginary connection between the drill and the relief angle, which is formed on the land at the transition from the flank to the chip groove,

[0016] In the case of surface grinding of the drill rake face, it is defined as being limited between:

[0017] - the imaginary connection of the cutting corner of the drill bit with the main cutting edge, and

[0018] - a radially outwardly extending section of the profile of the core sheet,

[0019] The opening angle is between 85° and 95°,

[0020] and the drill core thin piece has been introduced into the drill rake face so that the normal spacing of an inner point of the drill core thin piece from an imaginary connection of the drill bit to the cutting corner is less than or equal to the normal spacing of a transition point between a main cutting edge and a transverse cutting edge adjacent to the drill core thin piece from an imaginary connection of the drill bit to the cutting corner,

[0021] Therein, the thin core section begins at the transition point and adjoins the adjacent main cutting edge in a kink-free manner.

[0022] "Surface grinding" refers to grinding with a flat flank facet, in particular four-sided grinding.

[0023] The interaction of the small opening angle of between 85° and 95° and the centrally extending thin core section according to the present invention ensures particularly good axial chip removal in the center of the drilling tool. These features ensure that, in particular, chips removed radially inward are guided axially from the thin core section directly along the longitudinal axis into the chip flute. Consequently, chips carried radially inward do not reach the radially outer portions of the chip flute. The result is efficient chip removal, particularly near the center. Furthermore, the directly axially guided chips generate only minimal friction on the end face of the drilling tool.

[0024] Due to the spatial curve of the intersection of the drill core thin section and the flank surface which is produced variably during grinding, the definition of the opening angle has been assigned in relation to the respective grinding.

[0025] The present invention preferably provides that the core thinning portion extends further into the cutting corner in the direction of the imaginary connection of the drill bit than the transition point between the main cutting edge and the transverse cutting edge, which adjoins the core thinning portion. In other words, the present invention preferably provides that the core thinning portion extends further beyond the transverse cutting edge into the center of the drilling tool than the transition point between the main cutting edge and the transverse cutting edge in relation to the core thinning portion in question. In other words, the core thinning portion protrudes further than the transition point between the main cutting edge and the transverse cutting edge in the direction of the central interface spanned by the longitudinal axis and the connection of the cutting corner. These relationships become particularly clear in a front view of the drill rake face.

[0026] In particular, the thin drill core section is formed by a single grinding operation. This has the advantage that production is particularly economical.

[0027] The thin core portion is preferably single-sided.

[0028] This has the advantage that the surface of the thin part of the drill core is edgeless and therefore particularly low-friction. For production, this means that the introduction by means of the grinding tool can be carried out in one grinding operation, in particular in a step-free machining operation.

[0029] In particular, the present invention provides that the core thinning portion of adjacent main cutting edges, in the direction of the associated cutting corner, is curved only after a transition point. At the transition point, the main cutting edge and the core thinning portion preferably have the same tangent (in front view relative to the drill rake face). Only after the transition point does the core thinning portion exhibit a concavely curved progression. The term "concave" is to be interpreted herein with reference to a convexly curved main cutting edge. That is, while the main cutting edge arches in the direction of the chip flute, the curvature of the core thinning portion points in the opposite direction. In this regard, the transition point is preferably an inflection point.

[0030] In particular, the main cutting edge extends via a straight section into the transition point.

[0031] In particular, the drilling tool is a twist drill having a plurality of chip flutes extending in a twisted manner.

[0032] More preferably, the drilling tool has been integrally formed, comprising a cutting edge section and a shank section. Alternatively, the drilling tool may take the form of a drill bit that can be connected to a separate shank.

[0033] In particular, the drilling tool is made of a hard material such as hard metal. The term "hard metal" is to be understood as a composite material consisting of carbides as the hard material phase and a ductile metal belonging to the iron group (Fe, Co, Ni) as the binder phase. In particular, the hard material grains are made of tungsten carbide. In the case of hard metal, the binder is usually cobalt (Co). However, other metals or alloys are also considered as binders. In common English parlance, hard metal is also commonly referred to as "hard alloy." Particularly preferably, the drilling tool is in the form of a solid carbide (SC) tool.

[0034] The two main cutting edges have at least partially an arc-shaped run. In particular, the main cutting edges are convexly curved. The term "convex" in this context means that the main cutting edges arch into the designated chip flute.

[0035] In particular, the present invention provides that the main cutting edge passes into the transverse cutting edge by a straight section. Then, they form a cutting edge (edge) or turning ridge (kink) with the transverse cutting edge, which is also straight with respect to the front view of the drill rake face.

[0036] Therefore, the main cutting edge preferably has only a slight curvature near the center and is preferably composed of a straight line near the center. Due to the slight curvature near the center, or more preferably, the straight line near the center, low cutting forces are achieved near the center. As a result, only low torque acts on the drilling tool.

[0037] The core thin portion preferably at least partially presents an arcuate run having an apex at which the curvature of the arcuate run may have a maximum.

[0038] The radial position of the apex relative to the drill bit is typically between 0.02xBR and 0.1xBR, where BR is half the drill bit diameter. Specifically, the apex lies between 0.03xBR and 0.07xBR. This reflects the fact that the maximum curvature of the thin section of the drill core is particularly close to the center. Because the maximum curvature of the thin section of the drill core is so close to the center, chip deflection occurs at low trajectory speeds, and this is associated with low friction and torque.

[0039] The invention preferably provides that a tangent can be formed at the vertex of the thin drill core portion, the tangent normal of which forms an angle of between 60° and 70° with the imaginary connection of the drill head to the cutting corner.

[0040] This expresses the fact that the drill core thin portion has a main extension direction which can be established by a maximum curvature which presents an angle of between 60° and 70° compared to an imaginary connection between the drill head and the designated cutting corner.

[0041] The chips are always particularly strongly deflected at the point of maximum curvature. Due to the preferred position of the maximum curvature, only low torques and, therefore, low machining forces are generated. Due to the preferred position of the main extension direction of the thin section of the drill core, particularly good chip removal is achieved, with the chips entering the chip flute close to the center.

[0042] The present invention preferably provides that the axial angle of the thin core section, measured relative to the longitudinal drill axis, is between 30° and 40°. In particular, the axial angle of the thin core section amounts to 35°±1°. The axial angle of the thin core section is a measure of the axial "steepness" of the thin core section. A too gentle run-in, i.e., an axial angle of 45° or greater, for example, impairs the removal of chips into the chip flutes. An excessively steep run-in, i.e., an axial angle of 25° or less, prolongs the thin core section and results in a grinding cut at the transition from the thin core section to the land, which is detrimental to chip collection.

[0043] In particular, the preferred values ​​of the axial angle of the core thin portion are obtained in the region where the core thin portion extends radially outward, in particular in the region where the core thin portion extends straight radially outward. More preferably, the axial angle of the core thin portion is constant along the radial direction of travel of the core thin portion.

[0044] A method for producing a drilling tool is also sought, wherein a drill core thinning is introduced on the drill rake face, comprising the following grinding steps using a grinding tool:

[0045] i) forming a thin drill core portion near the center, the thin drill core portion having an apex at which the tangent normal presents an angle between 60° and 70°;

[0046] ii) forming the adjacent section of the thinned core section by moving the grinding tool radially outward. In the method according to the present invention, after creating the radius of the thinned core section near the center, the grinding tool is guided radially outward along a straight grinding path. The straight path is preferably oriented between 85° and 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 produce the drilling tool. In this section, only the steps related to creating the thinned core section will be considered. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Other advantages and effects of the present invention will become apparent from the following description of embodiments with reference to the accompanying drawings.

[0048] Figure 1a -d shows a drilling tool according to a first embodiment in different views;

[0049] Figure 2a -b shows a drilling tool according to a second embodiment in different views;

[0050] Figure 3 af shows a schematic representation of the method for production in the case of conical surface grinding;

[0051] Figure 4 af show a schematic representation of the method for production in the case of four-surface grinding. DETAILED DESCRIPTION

[0052] Figure 1a A drilling tool 1 according to a first embodiment is schematically shown, with the drill face 4 being marked in a front view of the front side of the drilling tool 1. The line of sight is parallel to the longitudinal axis L of the drilling tool 1, which also constitutes the central axis and is therefore highlighted in this illustration.

[0053] Two main cutting edges 2 are formed on the drill rake face 4 and are connected to each other via a transverse cutting edge 6 .

[0054] The drilling tool 1 according to the invention is a two-tool having two main cutting edges 2 .

[0055] The main cutting edge 2 preferably exhibits an arc-shaped progression in the direction of rotation R. In other words, the main cutting edge 2 is curved in an arc, with the arc's progression apex extending in the direction of rotation R. The drill bit has a convex main cutting edge 2. The arc-shaped design of at least a portion of the main cutting edge 2 enhances cutting edge strength while also ensuring smooth cutting.

[0056] The main cutting edge 2 preferably exhibits an S-shaped progression in an overall view.

[0057] The main cutting edge 2 preferably extends via a straight section into the transverse cutting edge 6. This means that each main cutting edge 2 preferably comprises an arcuate section radially on the outside and a straight section radially on the inside.

[0058] The drilling tool 1 is rotatable along its longitudinal axis L, in which case the direction of rotation R is defined. The drilling tool 1 according to the invention is accordingly right-handed. The invention can also be applied to left-handed tools. The chip flutes 5, which extend along the longitudinal axis L at a twist angle, are located in front of the main cutting edge 2 in each case relative to the direction of rotation R.

[0059] Furthermore, an outlet opening of the internal coolant line IK is shown, which may optionally be present.

[0060] The forwardmost point of the transverse cutting edge 6 constitutes the drill head 3 which lies on the longitudinal axis L.

[0061] In particular, the drilling tool 1 has been divided into equal parts, that is to say the main cutting edges 2 are distributed along 180°. The connection of the opposite cutting corners 9 accommodates the drill bit 3 .

[0062] Furthermore, the two main cutting edges 2 are preferably constructed identically; that is to say, a symmetrical drilling tool 1 divided into equal parts.

[0063] A drill web 7 has been formed between the flutes 5. A land 8 is located on the outer periphery of the drill web. In this embodiment, a guide chamfer 13 is formed on the drill diameter D. Opposite this, the land 8 is reset on the land diameter DR.

[0064] A flank 11 adjoins each main cutting edge 2 behind it with respect to the direction of rotation R. In the present embodiment, the drill rake face 4 has a conical surface grind, that is to say the flank 11 is formed by a section of a conical surface.

[0065] On the drill rake face 4 , a drill core thinning 12 is introduced in the relief face 11 , by means of which the transverse cutting edge 6 has been reduced to a desired size.

[0066] The flank 11 extends peripherally from the cutting corner 9 to the clearance corner 10, where it merges into the chip flute 5, thereby forming a cutting edge. In other words, in a front view of the drill rake face 4, the clearance corner 10 is the point on the outer periphery where the margin 8 and the profile 14 of the drill core thin portion 12 intersect. The intersection line between the drill core thin portion 12 and the flank 11 is designated as the profile 14 of the drill core thin portion 12.

[0067] The contour 14 of the drill core thin section 12 also marks the transition of the flank 11 into the chip flute 5 , to which the drill core thin section 12 is considered to belong.

[0068] In the present front view of the drill rake face 4, the aperture angle of the chip flute 5 can be defined on the drill rake face 4, the aperture angle spanning between:

[0069] The imaginary connection of the drill bit 3 with the cutting corner 9 of the main cutting edge 2 and the subsequent rotation direction R,

[0070] The imaginary connection of the drill 3 with the clearance angle 10 formed on the edge 8 at the transition from the flank 11 to the chip flute 5,

[0071] The opening angle is 85° to 95°.

[0072] This definition of the opening angle applies to drilling tools with a conical surface grind. The opening angle is preferably 90°±2°.

[0073] In this embodiment, more preferably, the opening angle is equal to 90°.

[0074] It should be noted that in this embodiment, the thin portion 12 of the drill core is produced along the curved course of the profile 14 due to the conical shape of the drill rake face 4. During the introduction of the thin portion 12 of the drill core by grinding, the grinding disc preferably performs a straight path from the radial inside to the outside and is preferably at a constant height relative to the longitudinal axis L.

[0075] For further observation, a dividing surface E is defined which divides the drilling tool in the middle and which contains the longitudinal axis L and the connection of the cutting corners 9 .

[0076] The core thin portion 12 begins at an intersection point, designated as transition point U, between the main cutting edge 2 and the transverse cutting edge 6 adjoining the core thin portion 12 .

[0077] The thin core portion 12 is formed so that, relative to the normal spacing from the imaginary connection of the drill bit 3 to the cutting corner 9, it extends in the direction of the center (that is, in the direction of the interface E of the drilling tool 1) by at least the same distance as the transition point U. Specifically, the thin core portion 12 extends further in the direction of the imaginary connection of the drill bit 3 to the cutting corner 9 than the transition point U. In other words, the thin core portion 12 protrudes further in the direction of the interface E than the transition point U connected to the thin core portion 12. In other words, the thin core portion 12 protrudes further in the direction of the interface E than the transverse cutting edge.

[0078] Due to the pronounced thinness of the drill core 12, additional chip space is created close to the center.

[0079] Furthermore, an advantageous chip removal can be achieved by the combination of the opening angle and the special geometry of the thin drill core section 12 .

[0080] Since the thin core portion 12 extends deep into the center and has the greatest curvature near the center, the chips undergo a large deflection near the center and are directed into the near-center chip flutes 5. As a result, a significant portion of the chip deflection occurs at low trajectory speeds and generates little force.

[0081] The favorable removal of chips in combination with the enlarged chip space in the center of the drilling tool 1 leads to significantly lower cutting forces and thus to reduced mechanical loads on the tool and workpiece.

[0082] In the region of the transverse cutting edge 6, the core thinning 12 preferably emerges from the main cutting edge 2 without twisting, in particular tangentially. In other words, at the transition point U, the core thinning 12 adjoins the adjacent main cutting edge 2 without kinking, in particular tangentially.

[0083] According to this preferred refinement, a “tangential” transition means that the main cutting edge 2 and the contour 14 of the core thin section 12 have the same tangent at the transition point U.

[0084] The non-torsionally tangential transition between the main cutting edge 2 and the drill core thin section 12 ensures a particularly gentle and uniform chip formation.

[0085] Figure 1b Shown Figure 1a 1. In this view, the clearance angle 10 can advantageously be defined as the intersection of the trailing edge 15 of the land 8 and the contour 14 of the thin portion 12 of the drill core, which marks the transition of the flank 11 into the chip flute 5.

[0086] exist Figure 1b In FIG. 1 , the axial angle of the thin core portion 12 measured relative to the longitudinal drilling axis L has also been inscribed.

[0087] The present invention preferably provides that the axial angle of the thin core portion 12 is between 30° and 40°. In particular, the axial angle of the thin core portion reaches 35°±2°, more preferably 35°±1°. This axial angle is measured in particular in the region of the thin core portion 12 in which the thin core portion 12 extends radially outward, in particular along a straight section.

[0088] Figure 1c Shown Figure 1a Detailed view of the view shown in , that is to say a front view of the drill rake face 4 along the longitudinal axis L.

[0089] By means of this detailed view, the clarity of the thin portion 12 of the drill core according to the invention becomes even more apparent.

[0090] According to the invention, the thin core portion 12 extends so far toward the center that the normal spacing NA of an inner point of the thin core portion 12 from the imaginary connection of the drill head 3 to the cutting corner 9 is less than or equal to the normal spacing NU (no longer in the image) of the transition point U between the main cutting edge 2 and the transverse cutting edge 6 adjacent to the thin core portion 12 from the imaginary connection of the drill head 3 to the cutting corner 9.

[0091] In other words, the profile 14 of the thin core portion 12 extends into the center of the drilling tool 1 at least as far as the transition point U adjacent to the thin core portion 12. The profile 14 of the thin core portion 12 leads further toward the center than the transition point U. In other words, the thin core portion extends as far "behind" the transverse cutting edge 6. The normal distance from the interface E is measured by measuring the distance from the center, not necessarily the distance from the drill head 3.

[0092] Furthermore, the main extension direction of the core thin portion 12 can be defined as:

[0093] The core thin portion 12 exhibits a vertex S near the center at which the curvature of the profile 14 of the core thin portion 12 may have a maximum. If the core thin portion 12 is continuously curved near the center, for example along a radius of curvature, a vertex S in the middle of a continuous curvature progression may be established.

[0094] The tangent line T may be established at the vertex S. The tangent normal line TN extending perpendicularly to the tangent line T determines the main extension direction of the core thin portion 12 .

[0095] At the transition point U between the designated main cutting edge 2 and the transverse cutting edge 6, at which transition point U the core thin section 12 adjoins the main cutting edge 2 in a twist-free manner, the main cutting edge 2 and the core thin section 12 having a common tangent line TU at the transition point U (as evident from the contour 14 with respect to the selected front view).

[0096] Figure 1d The same embodiment is shown again in a front view of the drill rake face 4. For the sake of clarity, further aspects of the invention will be explained with the aid of this separate figure. Likewise, for the sake of clarity, not all reference symbols are marked.

[0097] Therefore, the thin core portion 12 exhibits a concave shape having a curvature radius near its center. The curvature radius r of the thin core portion 12 at its vertex S is preferably 0.06 to 0.09 × D, where D is the drill hole diameter. More preferably, the curvature radius r of the thin core portion 12 is between 0.07 and 0.08 × D, particularly 0.075 × D. Optionally, the associated curvature circle having the curvature radius r is inscribed in the radius.

[0098] The tangent line TU of the main cutting edge 2 at the transition point U and the imaginary connection between the drill 3 and the cutting corner 9 preferably present an angle α between 10° and 30°. TU , more preferably presenting an angle α between 15° and 25° TU , yet more preferably presenting an angle α between 17° and 23° TU In particular, the angle α TU Equal to 20°±2°.

[0099] The main extension direction of the thin core portion 12 determined by the tangent normal TN includes an angle α between 30° and 60° with the tangent TU at the transition point U. TU , in particular an angle α between 40° and 50° TU , more preferably an angle α between 42° and 48° TU Angle α of 45°±2° TU This has proven to be particularly advantageous, in particular with regard to removing chips from the radially inner section of the main cutting edge 2 .

[0100] More preferably, the main extension direction of the drill core thin portion 12 established by the tangent normal TN includes an angle between 60° and 70° with the imaginary connection between the drill head 3 and the cutting corner 9. In particular, the angle is 65°±2°.

[0101] This orientation has proven to be particularly advantageous for near-center chip deflection and chip removal.

[0102] Furthermore, the beyond-center dimension a of the thin core portion 12 can be specified:

[0103] The over-center dimension a specifies how far the core thin portion 12 extends on the equatorial plane A, which extends at 90° compared to the dividing plane E and contains the longitudinal axis L.

[0104] In this example, with an opening angle of 90°, the locus of the equatorial plane A coincides with the connection of the two opposite relief corners 10 .

[0105] The over-center dimension a of the thin drill core portion 12 preferably amounts to between 5% and 15% of the drill hole diameter D, and more preferably amounts to 10%±2% of the drill hole diameter D.

[0106] The main cutting edge 2 preferably extends via a straight section into the transition point U. The main cutting edge 2 and the transverse cutting edge 6 therefore form a kink at the transition point U.

[0107] The transverse cutting edge 6 preferably presents, together with an imaginary connection between the drill head 3 and the cutting corner 9 , an angle between 50° and 70°, in particular an angle of 60°±2°.

[0108] Together with the already discussed preferred orientation of the main cutting edge 2 at the transition point U, it follows that it is particularly preferred that the main cutting edge 2 and the transverse cutting edge 6 at the transition point U exhibit an outer angle of 140°±4°.

[0109] In particular, the drilling tool 1 has a symmetrical structure, that is to say the geometric features in question apply to both chip flutes 5. In other words, the drilling tool 1 can be indexed into itself by being rotated along the longitudinal axis L by 180°.

[0110] Figure 2a and 2b Different views of a drilling tool 1 according to another embodiment are shown.

[0111] Figure 2a A front view of the drill rake face 4 of the drilling tool 1 according to the present invention is shown.

[0112] In this embodiment, so-called four-side grinding is formed on the drill rake face 4 .

[0113] In the case of four-sided grinding, the flank surface 11 comprises two partial lands 11a and 11b. The partial lands 11a, 11b of the flank surface 11 exhibit different clearance angles. The partial lands 11a, 11b of the flank surface 11 are preferably flat, that is, not curved.

[0114] For grinding with flat flank lands, as in the case of 4-side grinding here, the opening angle is defined as spanning between:

[0115] - an imaginary connection of the drill bit 3 with the cutting corner 9 of the designated main cutting edge 2, and

[0116] - a radially outwardly extending portion of the profile 14 of the core thin portion 12,

[0117] The opening angle is 85° to 95°. The opening angle is preferably 90°±2°. In this embodiment, more preferably, the opening angle is equal to 90°.

[0118] By “a radially outwardly extending portion of the profile 14 of the core thin portion 12 ” is understood a specific portion of the core thin portion 12 that is adjacent to the subcentral curvature of the core thin portion 12 and that extends substantially in a radially straight line under planar flank face grinding conditions.

[0119] The invention preferably provides that in the case of a drilling tool 1 with surface grinding, the profile 14 of the thin drill core portion 12 at least partially exhibits a straight run in a front view of the drill rake face 4, in which case this straight portion is preferably drawn as a second shank for defining the opening angle

[0120] For example, during the production of the drill core thin section 12 by means of a grinding tool, such a straight run is produced by means of a straight grinding path.

[0121] In particular, the profile 14 of the core thin portion 12 presents a radially outer straight section 14a.

[0122] The “radially outer straight section 14 a of the core thin portion 12 ” refers to the straight section 14 a of the profile 14 of the core thin portion 12 , via which the core thin portion 12 leads to the relief angle 10 .

[0123] Then, when determining the opening angle When the handle is pulled out, the straight section 14a is pulled out as a second handle.

[0124] For a better understanding, it should be explained that the thin core portion 12 is introduced in particular in such a way that the grinding disc first reproduces the radially inner rounding of the thin core portion 12 and then produces the remaining contour 14 of the thin core portion 12 along a straight path from the radial inner side to the outer side and preferably at a constant height relative to the longitudinal axis L. Since the thin core portion 12 in the present embodiment has already been introduced into the planar relief surface 11, the straight path of the grinding disc is also reproduced as a straight portion of the contour 14 of the thin core portion 12.

[0125] For this practical form of grinding with a flat flank land, the over-center dimension a of the thin core portion 12 can also be specified:

[0126] The over-center dimension a specifies how far the core thin portion 12 extends on the equatorial plane A, which extends at 90° compared to the dividing plane E and contains the longitudinal axis L.

[0127] The over-center dimension a of the thin drill core portion 12 preferably amounts to between 5% and 15% of the drill hole diameter D, and more preferably amounts to 10%±2% of the drill hole diameter D.

[0128] The construction of the drill core thin portion 12 is similar to the embodiment with a conical surface grind discussed previously. In particular, the details regarding the curvature, main extension direction and preferred dimensions of the drill core thin portion 12 apply to all practical forms, whether it is a drilling tool 1 with a conical surface grind or a drilling tool with a surface grind of a flat relief face.

[0129] exist Figure 2b In FIG. 1 , the axial angle of the thin core portion 12 measured relative to the longitudinal drilling axis L has also been inscribed.

[0130] The invention preferably provides that the axial angle γ of the thin core portion 12 is between 30° and 40°. In particular, the axial angle of the thin core portion amounts to 35°±1°. The axial angle of the thin core portion is a measure of the axial “steepness” of the thin core portion.

[0131] All improvements and advantages discussed apply equally to all embodiments.

[0132] Figure 3 Figures a to f show a preferred method for introducing a thin core section 12 in a drilling tool 1 having a conical surface. For a better understanding, the outline of the thin core section 12 has been engraved from the beginning. It is understood that the outline of the thin core section 12 is generated solely by the sequence of operations for introducing the thin core section 12 shown here. For the sake of clarity, only reference numerals are assigned to the individual figures.

[0133] The grinding tool 16, in the present case a grinding disk, is first moved in the direction of the drill head 3. The grinding tool 16 is moved along the axis of rotation DS Rotate.

[0134] Subsequently, the central portion of the thin core portion 12 is ground in such a way that its apex S is located “behind” the intersection of the transverse cutting edge 6 and the main cutting edge 2 in steps d)-e) relative to the dividing surface E.

[0135] Finally, in step f) shown, the grinding tool 16 is guided radially outwards along a straight grinding path.

[0136] Figure 4 Figures af show a preferred method for introducing the drill core thinning 12 in the case of a drilling tool 1 with a 4-surface grind.

[0137] The order of operations is similar to that with Figure 3 The method of af explanation is performed in a manner such that repetition of reference symbols is omitted.

[0138] Due to the flat flank surface, the radially tapering profile 14 of the thin drill core portion 12 appears here as a straight line segment.

[0139] List of reference marks used:

[0140] 1 drilling tool

[0141] 2 main cutting edges

[0142] 3 drill bits

[0143] 4 drill rake face

[0144] 5 chip flutes

[0145] 6 lateral cutting edges

[0146] 7 Drill core

[0147] 8-edge band

[0148] 9. Cutting corners

[0149] 10 rear angle

[0150] 11 Flank

[0151] 12 Drilling the thin part of the core

[0152] 13 Guide chamfer

[0153] 14. Profile of the thin part of the drill core

[0154] 15 trailing edge of the margin

[0155] 16 Grinding tools

Claims

1. A drilling tool comprising: Two main cutting edges (2), which at least partially have an arc-shaped run and are connected to each other by a transverse cutting edge (6), a drill rake face (4), a longitudinal drill axis (L), about which the drilling tool (1) is rotatable in a rotational direction (R), a drill bit (3) located on said longitudinal drilling axis (L), Two chip flutes (5) extending along the longitudinal drilling axis (L), The drill core (7) formed between the chip flutes (5) forms a land (8) in the circumferential direction. A thin drill core piece (12) is introduced into the drill rake face (4), wherein, relative to a front view of the drill rake face (4), an opening angle (α) of a chip flute (5) is formed on the drill rake face (4), and the opening angle (α) is: In the case of the conical surface grinding of the drill rake face (4), it is defined as being limited between: - an imaginary connection between the drill bit (3) and the cutting corner (9) of the main cutting edge (2), and - an imaginary connection of the drill bit (3) with the clearance angle (10) formed on the land (8) at the transition from the flank (11) to the chip flute (5), In the case of surface grinding of the drill rake face (4), it is defined as being limited between: - an imaginary connection between the drill bit (3) and the cutting corner (9) of the main cutting edge (2), and - a radially outwardly extending section of the profile (14) of the core sheet (12), The opening angle (α) is between 85° and 95°, and the drill core thin piece (12) has been introduced into the drill rake face (4) so ​​that the normal distance (NA) of the inner point of the drill core thin piece (12) from the imaginary connection of the drill head (3) to the cutting corner (9) is less than or equal to the normal distance (NU) of the transition point (U) between the main cutting edge (2) and the transverse cutting edge (6) adjacent to the drill core thin piece (12) from the imaginary connection of the drill head (3) to the cutting corner (9), The thin core portion (12) starts at the transition point (U) and adjoins the adjacent main cutting edge (2) in a kink-free manner.

2. The drilling tool (1) according to claim 1, wherein The drill core thin portion (12) extends further in the direction of an imaginary connection of the drill head (3) to the cutting corner (9) than a transition point (U) between the main cutting edge (2) and the transverse cutting edge (6) adjacent to the drill core thin portion (12).

3. The drilling tool (1) according to claim 1 or 2, wherein: The drill core thin portion (12) at least partially presents an arcuate run with a vertex (S) in a front view relative to the drill rake face (4), the radial position of the vertex (S) relative to the drill bit (3) being between 0.1×BR and 0.33×BR, where BR is half the borehole diameter (D).

4. The drilling tool (1) according to any one of the preceding claims, wherein The transition point (U) between the main cutting edge (2) and the transverse cutting edge (6) forms an inflection point relative to the curvature of the drill core thin portion (12).

5. The drilling tool (1) according to any one of the preceding claims, wherein The drill core thin portion (12) and the main cutting edge (2) present a common tangent line (TU) at a transition point (U) between the main cutting edge (2) and the transverse cutting edge (6).

6. Drilling tool (1) according to any one of the preceding claims, wherein A tangent can be constructed at the vertex (S) of the drill core thin portion (12), the tangent normal (TN) of which establishes the main direction of extension of the drill core thin portion (12), which forms an angle (α) between 30° and 60° with the tangent (TU) at the transition point (U) between the main cutting edge (2) and the transverse cutting edge (6). TN ).

7. Drilling tool (1) according to any one of the preceding claims, wherein A tangent can be constructed at the vertex (S) of the drill core thin portion (12), the tangent normal (TN) of which establishes the main direction of extension of the drill core thin portion (12), which presents an angle between 60° and 70° relative to an imaginary connection of the drill head (3) to the cutting corner (9).

8. Drilling tool (1) according to any one of the preceding claims, wherein The tangent line (TU) of the main cutting edge (2) at the transition point (U) between the main cutting edge (2) and the transverse cutting edge (6) forms an angle (α) between 10° and 30° with the imaginary connection between the drill bit (3) and the cutting corner (9). TU ).

9. The drilling tool (1) according to any one of the preceding claims, wherein The drill core thin portion (12) exhibits a maximum curvature near the center, wherein the radius of curvature (r) is between 0.06×D and 0.09×D, wherein D is the drill hole diameter.

10. The drilling tool (1) according to any one of the preceding claims, wherein The thin drill core portion (12) is single-sided.

11. The drilling tool (1) according to any one of the preceding claims, wherein The axial angle (γ) of the drill core thin portion (12) measured relative to the longitudinal drill axis (L) is between 30° and 40°.

12. A method for producing a drilling tool (1), in particular a drilling tool (1) according to any one of the preceding claims, wherein The introduction of a drill core thin piece (12) on the drill rake face (4) comprises the following grinding steps using a grinding tool (16): i) forming a thin drill core portion (12) near the center, said thin drill core portion having an apex (S) at which the tangent normal (TN) presents an angle between 60° and 70°; ii) The adjacent portion of the drill core thin portion (12) is formed by moving the grinding tool (16) outward in the direction of the pencil diameter.

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