Drilling tool and method for creating a hole

Abstract

Drilling tool for creating a bore with a cylindrical inner wall, a) wherein the drilling tool is rotatable in a rotary motion with a predetermined direction of rotation (VD) about a tool axis (A) passing through the drilling tool and at the same time is movable in an axial forward motion (VB) in a forward direction axial to the tool axis, b) wherein the drilling tool comprises at least one drilling area (3) which is arranged in a forward-directed area of ​​the drilling tool at a front or free end and has a drill tip (35), c) wherein the drilling area has a number n ≥ 3, i.e. at least three, drilling cutting edges (31, 32, 33) which are arranged offset from each other in the direction of rotation, where n is a natural number, d) wherein each of the n cutting edges (31, 32, 33), viewed radially to the tool axis (A), has an outer cutting edge (31A, 32A, 33A) and an inner cutting edge (31B, 32B, 33B), e) wherein the outer cutting edge of the drill (31A, 32A, 33A) is substantially perpendicular to the tool axis (A) and f) wherein the inner cutting edge of the drill (31B, 32B, 33B), viewed in the axial forward direction, rises towards the tool axis (A) towards the drill tip (35), g) wherein at least one chip divider (11, 12, 13) is arranged on each of the n cutting edges, forming an interruption of the respective cutting edge. h) wherein at least one, preferably two, of the n drilling cutting edges (31, 32) the associated at least one chip divider (11, 12) is arranged on the associated outer drilling cutting edge (31A, 32A) and i) on at least one, preferably exactly one, of the n drill cutting edges (33) the associated at least one chip divider (13) is arranged on the associated inner drill cutting edge (33B).

Description

[0001] The invention relates to a drilling tool and a method for producing a bore.

[0002] From DE 10 2021 105 703 A1, a drilling tool, in particular a twist drill, and a method for producing a bore with a cylindrical inner wall are known. The drilling tool has at least one drilling section, which is arranged in a forward-direction area at a front or free end of the drilling tool and has a number n of cutting edges that are offset from one another in the direction of rotation, where n is a natural number with n ≥ 1, preferably n ≥ 2. At least one or each of the n cutting edges has at least one chip breaker, in particular a chip breaker groove, which forms an interruption of the respective cutting edge.The axial depth of each chip divider, measured in the axial direction relative to the tool axis from the associated drill cutting edge, is selected from a range of 0.5 to 1.1 times the axial feed of the associated drill cutting edge relative to the immediately preceding drill cutting edge in the direction of rotation, and preferably at least approximately equal to this axial feed of the associated drill cutting edge. This is particularly advantageous with unequal pitch. Alternatively, the axial depth of each chip divider, measured in the axial direction relative to the tool axis, is selected from a range of 0.5 / n to 1.1 / n, preferably at least approximately 1 / n, multiplied by the axial feed of the drill tool per revolution. This is particularly advantageous with equal pitch.In an advantageous embodiment, the radial distances of the chip dividers from the tool axis at at least two of the n cutting edges are different from each other, such that in a rotational projection in the specified direction of rotation about the tool axis, a cutting area of ​​a subsequent second cutting edge follows a chip divider at a first cutting edge, and / or such that the radial distance of the chip divider at one of the two cutting edges at its innermost point closest to the tool axis is greater than the radial distance of the chip divider at the other of the two cutting edges at its outermost point furthest from the tool axis, and / or such that the outer radial distance of the chip divider at one of the two cutting edges is smaller than the inner radial distance of the chip divider at the other of the two cutting edges.The radial width of a chip breaker, particularly at the interruption of the associated drill cutting edge, is preferably selected from a range of 0.05 to 0.25 times the diameter of the drilling section. In the method known from DE 10 2021 105 703 A1, a high axial drilling feed per revolution of at least 9% of the diameter of the drilling section of the drill tool per revolution is achieved, in particular at least 0.5 mm per revolution for a diameter of 5.5 mm, and in particular at least 15% of the diameter of the drilling section of the drill tool per revolution, in particular at least 0.8 mm per revolution for a diameter of 5.5 mm. The feed per drill cutting edge is then obtained by multiplying the drilling feed f per revolution (360°) by the ratio of the pitch angle to 360°.

[0003] In an embodiment according to DE 10 2021 105 703 A1, the drilling area comprises two end-face (main) cutting edges, which can be arranged, in particular, obliquely or conically, or with a predetermined curvature, extending axially forward and converging in a drill tip, in particular in a cone tapering towards the drill tip and / or via a transverse cutting edge connecting the two cutting edges over the drill tip. The drill tip can also be designed as a centering tip.

[0004] US 2005 / 0053438 A1 discloses a twist drill with an outer cutting section and a central pilot tip extending axially in front of the outer cutting section, wherein the pilot tip is formed with at least one pair of minor cutting edges arranged on opposite sides of the axis, and the outer cutting section is formed with a pair of main cutting edges arranged thereon on opposite sides of the axis.

[0005] DE 20 2010 001 892 U1 discloses a drill with a centering section and two or three outer main cutting edges.

[0006] The invention is based on the objective of further developing the drilling tool and method known from DE 10 2021 105 703 A1 for producing a hole in a workpiece. In particular, it should also be possible to re-drill a pre-produced hole in a workpiece to a predetermined hole diameter with high accuracy and high speed.

[0007] Suitable embodiments and objects according to the invention for solving this problem are specified in particular in the claims, which are directed to a drilling tool, in particular with the features of independent claim 1, and a method for producing a bore using such a tool, in particular with the features of claim 18.

[0008] Further embodiments and developments according to the invention result from the respective dependent patent claims.

[0009] The claimable combinations of features and subject matter according to the invention are not limited to the chosen wording and cross-references of the claims. Rather, any feature of one claim category, for example, of a tool, can also be claimed in another claim category, for example, of a method. Furthermore, any feature in the claims, even independently of their cross-references, can be claimed in any combination with one or more other features in the claims. Moreover, any feature described or disclosed in the description or drawing can be claimed on its own, independently or separately from the context in which it appears, alone or in any combination with one or more other features described or disclosed in the claims or in the description or drawing.

[0010] According to claim 1, a drilling tool is proposed which is suitable and intended for producing a bore with a cylindrical inner wall, a) wherein the drilling tool is rotatable in a rotary motion with a predetermined direction of rotation about a tool axis passing through the drilling tool and at the same time is movable in an axial forward motion in a forward direction to the tool axis, b) wherein the drilling tool comprises at least one drilling area which is arranged in a forward-facing area at a front or free end of the drilling tool and which has a drill tip, c) wherein the drilling area has a number n of drill cutting edges which are arranged offset from each other in the direction of rotation, where n is a natural number with n ≥ 3, d) wherein each of the n cutting edges, viewed radially to the tool axis, has an outer cutting edge and an inner cutting edge, e) wherein the outer cutting edge of the drill section is substantially perpendicular to the tool axis and f) wherein the inner cutting edge of the drill, viewed in the axial forward direction, rises towards the tool axis towards the drill tip, g) wherein at least one chip divider is arranged on each of the n cutting edges, forming an interruption of the respective cutting edge, h) wherein at least one chip divider is arranged on at least one of the n drilling cutting edges and i) on at least one of the n drill cutting edges the associated at least one chip divider is arranged on the associated inner drill cutting edge.

[0011] In general, the at least three cutting edges are arranged offset from each other in the direction of rotation by a pitch angle of 360° / n if the pitch is the same, or by different pitch angles if the pitch is unequal.

[0012] In a particularly advantageous embodiment, three cutting edges are provided, each with a chip divider, and on two of the three cutting edges the associated chip divider is arranged on the associated outer cutting edge of the cutting edge, and on exactly one of the three cutting edges the associated chip divider is arranged on the associated inner cutting edge of the cutting edge.

[0013] The outer and inner cutting edges of each drill bit preferably enclose an angle greater than 100° and less than 170°, in particular 150° to 165°, preferably 160°. The inner cutting edge preferably encloses, viewed in the axial forward direction, a cutting angle between 100° and 170°, in particular 105° to 120°, preferably 110°, relative to the tool axis.

[0014] In an advantageous embodiment, the axial depth of each chip divider, measured in the axial direction relative to the tool axis from the associated drill cutting edge, is selected from a range of 0.5 to 1.1 times the axial feed of the associated drill cutting edge relative to the immediately preceding drill cutting edge in the direction of rotation, and preferably at least approximately equal to this axial feed of the associated drill cutting edge. This is particularly advantageous in the case of unequal pitch.

[0015] In a further advantageous embodiment, the axial depth of the chip divider(s), measured in the axial direction to the tool axis, is selected from a range of values ​​from 0.5 / n to 1.1 / n, preferably at least approximately 1 / n, multiplied by the axial feed of the drilling tool per revolution. This is particularly advantageous with equal pitch.

[0016] These advantageous measures ensure that the axial depth of the chip dividers is within the range of the chip thickness, allowing the chip to be completely divided or at least sufficiently weakened to be divided.

[0017] In an advantageous embodiment, the radial distances of the chip dividers from the tool axis at at least two, preferably all, of the n cutting edges are different from each other, such that in a rotational projection in the specified direction of rotation about the tool axis, a cutting area of ​​a subsequent second cutting edge follows a chip divider at a first cutting edge, and / or such that the radial distance of the chip divider at one of the two cutting edges at its innermost point closest to the tool axis is greater than the radial distance of the chip divider at the other of the two cutting edges at its outermost point furthest from the tool axis, and / or such that the outer radial distance of the chip divider at one of the two cutting edges is smaller than the inner radial distance of the chip divider at the other of the two cutting edges.Preferably, the radial distances are also chosen so that an approximately uniform distribution of the chip dividers is achieved, either radially or along the cutting edge length.

[0018] A radial width of a chip divider, particularly at the interruption of the associated drill cutting edge, is preferably selected from a range of 0.05 times to 0.25 times the diameter of the drilling area.

[0019] Advantageously, at least one or every chip divider is designed as a chip divider groove that forms an interruption at the respective drilling edge.

[0020] In one embodiment, at least one chip-part groove of the respective chip divider extends from the respective drill cutting edge into an adjacent clearance surface or sequence of clearance surfaces. The length of the chip-part groove extension is adjustable, in particular by the clearance angle or the position of the clearance surface(s).

[0021] The chip groove can also extend along the rake face of the respective drill cutting edge in another embodiment.

[0022] The extension of the chip-part groove(s) preferably follows a substantially linear path or a sequence of at least two or three linear groove sections inclined towards each other, in particular inclined inwards towards the tool axis (or convexly). The linear extension of the chip-part groove or its sections can, in particular, each run tangentially to a circle around the tool axis.

[0023] Furthermore, a curve in the extent of the chip section groove(s) that is at least partially curved, preferably convex to the tool axis, is also possible.

[0024] In a preferred embodiment, at least one or each chip section groove of the respective chip divider can have a substantially linear profile or a sequence of at least two or three linear sections inclined towards each other, particularly inclined inwards towards the tool axis, wherein the linear extent of the chip section groove or its sections is particularly tangential to a circle around the tool axis. However, the chip section groove can also have a profile that is at least partially curved, preferably convex to the tool axis.

[0025] It has proven advantageous for at least one or each chip section groove to have a cross-section in the form of a trapezoid, the trapezoid preferably opening in the forward direction or towards the cutting edge, in particular with an opening angle of between 45° and 90°, preferably at least approximately 60°.

[0026] In various embodiments, at least one chip divider or chip divider groove can also have a cross-section in the form of a triangle or trapezoid or dovetail or rectangle or a double shaft or a curve, in particular a semicircle, optionally with extended linear side walls.

[0027] At least one chip divider can also be designed as a chip divider step.

[0028] In general, each cutting edge is arranged and / or formed on an associated web, wherein at least one clearance face adjoins each cutting edge on each web, particularly on an end face of the web. The clearance angle of the clearance face is preferably in a radially outer range between 3° and 15° or between 5° and 15°, particularly 6° or 10°, and preferably increases radially inwards, particularly to a value of up to a maximum of 40°.

[0029] The free surface is in particular conical in shape or produced with a conical grinding, but can also be flat or even.

[0030] Preferably, the drilling tool includes at least one chip removal groove(s) starting in the drilling area for removing the drill chips. The axial length of the chip removal grooves is generally greater than the maximum hole depth or penetration depth of the tool, so that the chip removal grooves always extend into an area above or outside the workpiece surface and can remove the chips from the borehole. Preferably, one of the webs runs between each pair of chip removal grooves.

[0031] Chip removal grooves and / or webs preferably run spirally around the tool axis, in particular at a constant or variable spiral angle, which is typically in an interval of 0° to 50°, in particular 20° to 35°, for example 30°.

[0032] In advantageous embodiments, at least one chip groove extends to an outlet for cooling and / or lubricating medium in the associated web, wherein the outlet is preferably connected to a channel running in an associated web or represents its opening.

[0033] The radial diameter of the drilling area relative to the tool axis is preferably a maximum of 20 mm (i.e. a size at which chip dividers are not normally used in twist drills).

[0034] In all embodiments, the rake face on each drill cutting edge is preferably not provided with a protruding chip-forming surface or chip-forming step, but rather runs continuously with a comparatively small curvature. This allows the drilling area to be designed more compactly and axially shorter.

[0035] Another advantageous embodiment provides a guide area on the outer circumference of the drill bit, which is axially offset from the drilling area. The guide area has a diameter that corresponds to the outer diameter of the drilling area or is only slightly smaller, for example by 0.5 to 2%. This guide area preferably serves to guide the drill bit within the bore. The guide area is preferably divided into individual guide sections, each provided on one of the webs. The guide area, preferably each guide section on each web, can have at least one circumferentially extending lubrication groove, preferably at least two axially spaced lubrication grooves, for supplying lubricant, in particular oil, to the guide area during the drilling process.Preferably, each lubrication groove(s) runs along a helix with a pitch corresponding to the axial feed per revolution or per drill cutting edge.

[0036] In a particular embodiment, a corner chamfer is provided on the outer edges of the drill cutting edges. The chamfer angle relative to the radial direction can be selected in the range of 0° to 60°, preferably between 15° and 30°, and / or the angle of the chamfer (70) relative to the tool axis (A) can be selected from an interval between 0° and the magnitude of the helix angle, in particular of the chip removal grooves (25), preferably 0°. The radially measured chamfer width is preferably between 0.05 mm and 0.4 mm.

[0037] The method according to the invention, in particular according to claim 15, is provided for producing a bore with a cylindrical inner wall, especially without threads. A drilling tool according to the invention is used, and the following process steps – typical for a drilling operation – are carried out with it: - When creating the bore, the drilling tool is rotated in a predetermined forward direction around the tool axis passing through the drilling tool in a forward rotary motion and simultaneously moved axially to the tool axis in a forward direction. - Subsequently, the drilling tool is moved out of the created hole in an axial reverse direction, opposite to the forward direction, while continuing to rotate in the forward direction. This prevents thread formation.

[0038] In contrast to known drilling methods using twist drills, the invention preferably employs a high axial drilling feed f of the forward movement of the drilling tool per revolution, amounting to at least 9% of the diameter of the drilling area of ​​the drilling tool per revolution, in particular at least 0.5 mm per revolution for a diameter of 5.5 mm, and in particular at least 15% of the diameter of the drilling area of ​​the drilling tool per revolution, in particular at least 0.8 mm per revolution for a diameter of 5.5 mm. The feed fz per drill cutting edge is then obtained by multiplying the drilling feed f per revolution (360°) by the ratio of the pitch angle to 360°.

[0039] The rotational speed of the drilling tool, at least during the drilling process, is preferably selected from a range between 1000 rpm and 20,000 rpm. The axial speed when withdrawing the drilling tool from the bore is generally higher, preferably at least five times higher, than during the axial forward movement.

[0040] The invention will be further explained below with reference to exemplary embodiments. Reference will also be made to the drawings, in which Fig. 1 a drilling tool in a perspective side view, Fig. 2 a front view of the drilling area of ​​the drilling tool according to Fig. 1, Fig. 3 an enlarged perspective side view of the drilling area of ​​the drilling tool according to Fig. 1, Fig. 4 an enlarged, compared to Fig. 3 Rotated perspective front view of the drilling area of ​​the drilling tool according to Fig. 1 and Fig. 5 an enlarged, once again opposite Fig. 4 Rotated perspective front view of the drilling area of ​​the drilling tool according to Fig. 1 are each shown schematically. Corresponding parts and sizes are shown in the Fig. Label numbers 1 to 5 with the same reference symbols.

[0041] The drilling tool designated by 2 (hereinafter also referred to as tool) is used to create a cylindrical bore, in particular a blind hole or through hole, and is designed with a drilling area 3 for this purpose.

[0042] The drilling tool 2 is preferably driven rotaryally or in a forward direction VD about its tool axis A by means of a coupling area on a tool shank 24 extending or formed axially to the tool axis A by means of a rotary drive (not shown), in particular a machine tool and / or drive or machine tool spindle. Furthermore, the tool 2 is axially movable in an axial forward movement VB and in an opposite axial return movement axially to the tool axis A, in particular by means of an axial drive, which in turn may be provided in the machine tool and / or drive or machine tool spindle. An outer diameter of the shank 24 is designated d2.

[0043] The drilling section 3 is provided at a free end region or end face of the drilling tool 2, facing away from the coupling area of ​​the shank 24. The drilling section 3 has an outer diameter or drilling diameter d1 and creates a bore with this inner diameter d1 in the workpiece (not shown). The drilling section 3 of the rotating tool 2 is placed on the workpiece surface with its drill tip 35, and the drilling process is started.

[0044] To create the hole, the drilling tool 2 is moved into a workpiece (not shown) in a working motion composed of the rotary motion VD about the tool axis on the one hand and the axial feed motion VB along the tool axis A on the other, and the drilling area 3 creates the hole by machining. During this drilling process, the tool axis A typically coincides with the central axis of the hole.

[0045] When the bottom of the bore or the maximum drilling depth is reached, the drill bit 2 is withdrawn from the bore in an axial retraction movement opposite to the forward direction of the working motion. During this retraction movement, a significantly higher axial speed is generally selected than during the working motion of drilling, for example, an axial speed 5 to 50 times higher. The drill bit continues to rotate during the retraction movement, and its direction of rotation remains unchanged compared to the working motion, i.e., it corresponds to the forward direction of rotation VD. The rotational speed during drilling is generally between 1000 rpm (revolutions per minute) and 20 rpm.A speed of 000 rpm is selected, usually depending on the machine tool, the workpiece, and the diameter of the drilling tool, for example, such that tangential peripheral speeds at the outer diameter of between 30 and 300 m / min are achieved. While the speed can be lowered when withdrawing the tool from the bore, it is generally maintained.

[0046] The present drilling tool 2 according to the invention is particularly suitable and intended for high axial drilling feed rates f. In the preferred embodiment, the axial feed rate f of the drilling tool during the axial feed movement during drilling (drilling feed) is selected to be at least 0.5 mm, preferably at least 0.8 mm, per revolution for a diameter d1 = 5.5 mm (generally 9% or 15% of the diameter d1) and can, without limiting generality, reach up to 1.5 mm and even up to 2 mm per revolution. The drilling feed rate f can be adapted to the diameter d1 of the drilling area 3 of the drilling tool 2, whereby, as a rule, a larger drilling feed rate f is also selected or can be selected.

[0047] Such a significantly higher drilling feed rate compared to known spiral drills is made possible by the special design of the drilling tool according to the invention, which will be further explained below using exemplary embodiments.

[0048] In the illustrated embodiments, the drilling area 3 comprises three end-face drill cutting edges 31, 32, and 33. Generally, two, four, or more drill cutting edges can also be provided, i.e., generally a number n ≥ 2 of drill cutting edges. The drill cutting edges are arranged offset from one another in the direction of rotation VD, in particular at the same pitch by a pitch angle of 360° / n, i.e., 360° / 3 = 120° for the three drill cutting edges 31, 32, and 33, or also at unequal pitches with different pitch angles. The end-face drill cutting edges 31, 32, and 33 are designed to cut in the forward direction of rotation VD, in the illustrated embodiment right-hand cutting, and remove material from the workpiece, which lies axially in front of the drilling tool 2, by chip removal during the forward movement VB with simultaneous rotation in the forward direction of rotation VD.

[0049] Each drilling cutting edge 31, 32, and 33 is formed or composed of an outer drilling cutting edge 31A, 32A, and 33A, respectively, located further outwards radially to the tool axis A, and an inner drilling cutting edge 31B, 32BA, and 33B, respectively, located radially closer to the tool axis A. The radial extent of the outer drilling cutting edge 31A, 32A, and 33A, measured radially to the tool axis A, is preferably greater than the radial extent of the corresponding inner drilling cutting edge 31B, 32BA, and 33B, in particular by a factor between 1.2 and 2, preferably 1.8. When a pilot hole is re-drilled, the radial extent of the corresponding inner cutting edge 31B or 32B or 33B is typically between 2.5% and 12.5%, preferably about 7.5%, smaller than the diameter of the pilot hole.

[0050] The three inner cutting edges 31B, 32B, and 33B preferably converge at or within the drill tip 33, particularly in a cone tapering towards the drill tip 35. The inner cutting edges 31B, 32B, and 33B thus run obliquely in the forward direction VB or at an angle of inclination β, which is an angle enclosed between the inner cutting edge 31B, 32B, or 33B, viewed in the axial forward direction, and the tool axis A. This angle can generally be between 100° and 170°, and in the illustrated embodiment, where a tip angle of 140° is achieved at the drill tip 35, it is, for example, 110°.

[0051] In contrast, the outer cutting edges 31A, 32A and 33A are arranged or formed at a cutting angle α to the tool axis A, which is preferably 90°, so that the outer cutting edges 31A, 32A and 33A run orthogonally, preferably in a common normal plane, to the tool axis A. This prevents radial deflection forces or lever moments from occurring at the outer cutting edges 31A, 32A and 33A during drilling, particularly when re-drilling misaligned pilot holes.

[0052] The inner cutting edge 31B, 32B, and 33B of each cutting edge 31, 32, and 33 thus encloses an angle γ with the corresponding outer cutting edge 31A, 32A, and 33A, for which the following applies: γ = 270° - β when α = 90°, which is therefore selected from an interval between 100° and 170°. In the illustrated embodiment with β = 110°, γ = 160° is selected.

[0053] Furthermore, chip removal grooves 25 are provided on the tool 2, which begin in the drilling area 3 and extend into the shank 24. Drill webs (or: backs) 41, 42 and 43 are arranged and formed between the chip removal grooves 25. The first drill cutting edge 31 is formed on the first drill web 41, the second drill cutting edge 32 on the second drill web 42, and the third drill cutting edge 33 on the third drill web 43, each in the front area or on the end face of the respective drill web.

[0054] Preferably, the chip removal flutes 25 and the intervening drill webs 41, 42, and 43 are spiraled around the tool axis A at a constant or variable helix angle, typically in an interval of 0° to 50°, particularly 20° to 35°, for example, 30° (twist drills), but can also run parallel or axially to the tool axis A. The axial length of the chip removal flutes 25 is preferably greater than the maximum hole depth or penetration depth of the tool 2, i.e., the chip removal flutes 25 extend into an area above or outside the workpiece surface. This allows the chips generated in the hole in the workpiece to be guided outwards through the chip removal flutes 25 at every stage of the process.

[0055] On each cutting edge 31, 32, or 33, the associated chip evacuation groove 25 forms a corresponding rake face. The rake angles of these rake faces on the cutting edges 31, 32, and 33 are preferably selected in a range between -10° and +45°, wherein the rake angles preferably increase from the inside out with respect to the tool axis A, and can be located closer to the tool axis A in a range between -10° and +10°, and in the outer region in particular between 15° and 45°, preferably corresponding to the helix angle of the helical chip evacuation grooves 25.

[0056] On the rear side of the drill cutting edge 31, 32, and 33, facing away from the rake face or associated chip removal groove 25, a clearance surface (e.g., 51, 52) is attached to each of these, which is also arranged on the end face of the associated drill web 41, 42, or 43, respectively. The clearance angles of the clearance surfaces, i.e., the angles between the clearance surface and a transverse plane running tangentially through the drill cutting edge perpendicular to the tool axis A, are generally selected such that, despite the preferably high axial feed rate f, friction between the end faces of the drill webs 41 to 43 formed by these clearance surfaces and the workpiece 2 is avoided. The minimum clearance angle for a specific radius r can be approximately calculated according to the formula arctan(axial feed per revolution / (2rπ)), i.e., arctan(f / (2rπ)), and thus increases from the outside to the inside. However, a larger clearance angle is usually chosen to reliably prevent friction.The clearance angle is preferably selected in a clearance area directly adjacent to the drill cutting edges 31, 32 and 33, in a radially outer region, preferably between 5° and 15°, particularly 10°, and increases radially inwards, particularly up to the roof angle of the drill tip 35. This ensures a stable drill cutting edge 31, 32, or 33. The clearance area can be conical, produced by conical grinding, or flat.

[0057] Furthermore, on the end face of each drill web 41, 42 and 43 there is, for example, a round or convex cross-section outlet 60 of a fluid channel running through the respective drill web for supplying coolant and / or lubricant, which, like the drill web, can run axially or spirally.

[0058] According to the invention, the drilling tool is equipped with chip dividers, preferably exactly one chip divider per cutting edge, which divide and narrow the chips produced by the cutting edges, thereby generating ribbon chips in particular. These ribbon chips are presumably broken during removal due to the high feed rates and possibly also the brittleness of the material; in any case, the expected process problems with ribbon chips were not observed during investigations. However, chip dividers need not be provided on all cutting edges, and / or more than one chip divider can be provided on a single cutting edge.

[0059] In the illustrated embodiments, a first chip divider 11 is arranged on the first drilling edge 31, a second chip divider 12 on the second drilling edge 32, and a third chip divider 13 on the third drilling edge 33. Each chip divider 11, 12, and 13 forms an interruption of the respective drilling edge 31, 32, and 33, respectively.

[0060] Preferably, each chip divider is arranged in only one of the two partial cutting edges of each drill bit, i.e., not overlapping in rotational projection. In the advantageous embodiments shown, chip divider 11 is located in the outer partial cutting edge 31A of the drill bit 31 at a radial distance r1 from the tool axis A, and chip divider 12 is located in the outer partial cutting edge 32A of the drill bit 32 at a radial distance r2 from the tool axis A. The third chip divider 13, on the other hand, is located in the inclined inner partial cutting edge 33A of the third drill bit 33 at a radial distance r3.

[0061] The radial distances r1, r2, and r3 of the chip dividers 11, 12, and 13 are preferably different from one another and are preferably selected such that, in a rotational projection opposite to the direction of rotation of the tool 2, there is no overlap between immediately adjacent chip dividers 11 and 12 or 12 and 13, i.e., they are still slightly radially spaced apart. This means that, in a rotational projection, a subsequent cutting edge lies behind a chip divider of a drill bit, and the chips are thus divided differently and limited in length. Furthermore, scoring at the bottom of the bore is also prevented.

[0062] Preferably, the radial distances r1, r2, and r3 are chosen such that an approximately uniform distribution of the chip dividers is achieved radially or over the cutting edge length, for example by making r2-r1 at least approximately equal to r1-r3.

[0063] A radial width b1 of the chip divider 11 and a radial width b2 of the chip divider 12 as well as a radial width b3 of the chip divider 13 are preferably chosen to be the same and / or preferably chosen such that the outer radial distance r3 = r2 + b2 of the more inwardly located chip divider 12 is smaller than the inner radial distance r1 of the other chip divider 11, thereby avoiding an overlap of the interruptions of the chip dividers in the rotational projection.

[0064] Preferred values ​​are selected for the radial widths b1 and b2 from a range of 0.05 d1 to 0.25 d1, for the radial distance r1 from a range of 0.05 d1 to 0.25 d1, for the radial distance r2 from a range of 0.25 d1 to 0.4 d1, and for the radial distance r3 from a range of 0.1 d1 to 0.2 d1.

[0065] In a preferred embodiment, the chip dividers 11, 12, and 13 are designed as chip divider grooves extending from the respective drill cutting edge 31, 32, and 33, respectively, into the clearance surfaces behind them on the end face of the drill webs 41, 42, and 43. The chip divider groove of each chip divider 11, 12, and 13 has a groove base 11A, 12A, and 13A, respectively, and two groove flanks 11B, 12B, and 13B, which extend from the groove base 11A, 12A, and 13A, respectively, to the associated drill cutting edge 11, 12, and 13, respectively. The leading edges of the chip divider grooves, or of the groove base and the groove flanks, viewed in the direction of rotation, also form cutting edges for separating the chips.

[0066] The lengths of the chip dividers or chip slots 11 and 12 can be chosen to be equal to each other and / or variable, in particular by varying the clearance angles or the position of the clearance surfaces. For a given depth t1 or t2, the length of the chip dividers' slots 11 and 12 can be adjusted, in particular, by the inclination of the clearance surface, i.e., by selecting the clearance angles. With a steeper orientation or larger clearance angles, the length of the chip dividers is shorter, and with smaller clearance angles or a less steep orientation of the clearance surfaces, the length of the chip dividers is greater. The clearance surfaces and their comparatively large clearance angles ensure that the trailing edges of the chip dividers do not rub against the workpiece.

[0067] Preferably, the length or extent of at least a portion of the chip dividers or chip divider grooves is selected such that they extend as close as possible to, or even directly into, the outlet for the coolant and / or lubricant, in particular the outlets 60 in the drill webs 41, 42, and 43 (see, for example, chip dividers 11 and 13). This allows coolant and / or lubricant to be guided to the drill cutting edges through the chip divider grooves. Even with an arrangement close to the outlet, a significant portion of the coolant and / or lubricant reaches the drill cutting edge through the chip guide groove and can exert a cooling or lubricating effect there, in addition to the coolant and / or lubricant already reaching the drill cutting edge from the outside or via the outer surfaces.

[0068] The extension of the chip-forming groove from the drill cutting edge into the flank faces or rake face can be formed in a variety of shapes and lengths. As shown, a linear extension can be chosen, which has the advantage of being easily produced with a grinding wheel. This linear extension can be tangential to a circle around the tool axis A or oblique to a tangential direction, with the length I1 or I2 measured along the linear extension. Furthermore, a curved path for the chip-forming groove is also possible. Here, for example, a path along a circle around the tool axis A or another curved path can be chosen. The length of a curved path is then determined, in particular, as the arc length.In general, the chip divider grooves should be designed so that the material that remains can move freely through the chip divider, i.e., it does not "contact" at any point after the cutting edge, whether axially or radially.

[0069] In an embodiment not shown, at least one or each chip groove can extend from the drill cutting edge into the clearance faces or the rake face in the form of two, three, or more, particularly linear, successive sections, which are arranged, in particular, inclined to one another or at an angle to one another. The linear extension of each section of the chip groove(s) can be tangential to a circle around the tool axis A or oblique to a tangential direction. This allows the chip groove to approximate a path along the circumference or along a curve, particularly circular curvature, especially around the tool axis A, in the manner of a partial polygon. Each linear section can then preferably be generated by a linear movement of a grinding wheel. Furthermore, chip grooves with successive linear and curved sections can also be provided.

[0070] The axial depths t1 and t2 of the chip part grooves of the chip dividers 11 and 12, measured in the axial direction from the interruption to the tool axis A, can be selected within a wide range and are preferably equal to each other.

[0071] In a particularly advantageous embodiment, the axial depths t1 and t2 of the chip-dividing grooves of the chip dividers 11 and 12 are set in a range of exactly or approximately half the axial feed (axial drilling feed) f of the drilling tool, particularly when the drill cutting edges are evenly distributed or arranged at the same pitch angles. Generally, with a number n of drill cutting edges, the axial depth of the chip divider at the drill cutting edge lies essentially in a range of fx 0.5 / n to fx 1.1 / n, particularly fx 0.8 / n to fx 1 / n, preferably at f / n.

[0072] Alternatively, the axial depth of each chip divider is set within a range of 0.5 to 1.1 times the axial feed fz of the associated drill bit relative to the immediately preceding drill bit in the direction of rotation. Preferably, the axial depth of the chip divider is at least approximately equal to this axial feed fz per drill bit. This is particularly advantageous in the case of unequal pitching, i.e., when the drill bits are not arranged at the same pitch angle to each other.

[0073] In these embodiments, the axial depth of the chip dividers is thus set in the range of the chip thickness, so that the chip can be completely divided or at least weakened sufficiently so that it can then be easily reshaped or broken.

[0074] The chip section grooves or chip dividers 11 and 12 preferably also have a clearance angle, in particular an axial clearance angle and / or a radial clearance angle, preferably from a range of 0° to 20°, in particular 14°, which also affects the axial depth.

[0075] The position, shape, length, and cross-section of the chip-cutting grooves can be selected within wide limits, depending on the desired chip pitch and other functions and parameters. This allows for varying degrees of chip formation through different tearing and upsetting characteristics, and also positively influences wear.

[0076] In a preferred embodiment, the chip-part grooves of the chip dividers 11, 12, and 13, in particular their groove base and groove flanks, have a trapezoidal cross-section, at least at the cutting edge 31, 32, and 33, respectively, but preferably also continuously. This trapezoid opens towards the end face or in the forward direction with an opening angle that is preferably selected from a range of 45° to 90°, and preferably at approximately 60°. This design has proven advantageous with regard to clearance in the feed direction.

[0077] However, a dovetail-shaped cross-section of the chip section grooves of the chip dividers 11 and 12 in the form of an undercut trapezoid is also possible, or a rectangular cross-section of the chip section grooves of the chip dividers 11 and 12, or a triangular cross-section, or at least a partially convex curved or round cross-section, or a cross-section comparable to a roughing tooth on milling cutters.

[0078] The cutting edges of the drill bits 31, 32, and 33 are generally at least largely linear, but can also have a slightly curved profile, particularly a convex curve in the forward direction of rotation VD. Preferably, the drill bits 31, 32, and 33 run at least partially in a common plane to each other.

[0079] The cutting edges 31, 32, and 33 can also converge towards the drill tip 35, which is located at the central tool axis A, via cross-cutting edges. In the center or in the area of ​​the cross-cutting edges, the rake angle and clearance angle approach each other.

[0080] The drilling tool, or at least the drilling section 3, can be made of carbide, HSSE, or PCD. The chip removal flutes can be at least partially polished, especially on the rake faces. The drilling tool can be manufactured at least partially using additive manufacturing. The cutting edges of the drill bits can be rounded. Reference symbol list 2 Drilling tools 3 Drilling area 11, 12, 13 Chip dividers 11A, 12A, 13A Groove 11B, 12B, 13B groove flank 24 shaft 25 Chip removal groove 31, 32, 33 Drill cutting edge 31A, 31B Drilling part cutting edge 32A, 32B Drilling part cutting edge 33A, 33B Drilling part cutting edge 35 drill bit 41, 42, 43 Drilling platform 51, 52 Open space 60 Exit A tool axis b1, b2, b3 width (the chip divider) d1, d2 diameter t1, t2, t3 axial depth (of the chip divider) VB forward movement VD Direction of Rotation α Cutting angle β Cutting angle γ Cutting angle

Claims

[1] Drilling tool for producing a bore with a cylindrical inner wall, a) wherein the drilling tool is rotatable in a rotary motion with a predetermined direction of rotation (VD) about a tool axis (A) passing through the drilling tool and at the same time is movable in an axial forward motion (VB) in a forward direction axial to the tool axis, b) wherein the drilling tool comprises at least one drilling area (3) which is arranged in a forward-directed area of ​​the drilling tool at a front or free end and has a drill tip (35), c) wherein the drilling area has a number n ≥ 3, i.e. at least three, drilling cutting edges (31, 32, 33) which are arranged offset from each other in the direction of rotation, where n is a natural number, d) wherein each of the n cutting edges (31, 32, 33), viewed radially to the tool axis (A), has an outer cutting edge (31A, 32A, 33A) and an inner cutting edge (31B, 32B, 33B), e) wherein the outer cutting edge of the drill (31A, 32A, 33A) is substantially perpendicular to the tool axis (A) and f) wherein the inner cutting edge of the drill (31B, 32B, 33B), viewed in the axial forward direction, rises towards the tool axis (A) towards the drill tip (35), g) wherein at least one chip divider (11, 12, 13) is arranged on each of the n cutting edges, forming an interruption of the respective cutting edge. h) wherein at least one, preferably two, of the n drilling cutting edges (31, 32) the associated at least one chip divider (11, 12) is arranged on the associated outer drilling cutting edge (31A, 32A) and i) on at least one, preferably exactly one, of the n drill cutting edges (33) the associated at least one chip divider (13) is arranged on the associated inner drill cutting edge (33B). [2] Drilling tool according to claim 1, wherein the n drilling cutting edges are arranged offset from each other in the direction of rotation by a pitch angle of 360° / n if the pitch is the same or by different pitch angles if the pitch is unequal. [3] Drilling tool according to claim 1 or claim 2, wherein three (n = 3) drill cutting edges (31, 32, 33) are provided with each a chip divider (11, 12, 13) and on two of the three drill cutting edges (31, 32) the associated chip divider (11) is arranged on the associated outer drill cutting edge (31A, 32A) and on one of the three drill cutting edges (33) the associated chip divider (13) is arranged on the associated inner drill cutting edge (33B). [4] Drilling tool according to one of the preceding claims, wherein the outer cutting edge (31A, 32A, 33A) and the inner cutting edge (31B, 32B, 33B) of each drilling cutting edge enclose an included angle (γ) from a range between 100° and 170°, in particular 150° to 165°, preferably 160°, or the inner cutting edge (31B, 32B, 33B), viewed in the axial forward direction, to the tool axis (A) encloses an included cutting angle (β) between 100° and 170°, in particular 105° to 120°, preferably 110°. [5] Drilling tool according to one of the preceding claims, wherein the axial depth of the or each chip divider, measured in the axial direction to the tool axis from the associated drill cutting edge, is selected from a range of 0.5 times to 1.1 times the axial feed of the associated drill cutting edge relative to the immediately preceding drill cutting edge in the direction of rotation, preferably at least approximately equal to this axial feed of the associated drill cutting edge. [6] Drilling tool according to one of the preceding claims, wherein the axial depth of the or each chip divider, measured in the axial direction to the tool axis, is selected from a range of 0.5 / n to 1.1 / n, preferably at least approximately 1 / n, multiplied by the axial feed of the drilling tool per revolution. [7] Drilling tool according to one of the preceding claims, wherein the radial distances (r1, r2, r3) of the chip dividers (11, 12) from the tool axis (A) are different at at least two of the n cutting edges (31, 32), such that in a rotational projection in the specified direction of rotation about the tool axis, a cutting area of ​​a subsequent second cutting edge follows a chip divider at a first cutting edge, and / or such that the radial distance of the chip divider at one of the two cutting edges at its innermost point closest to the tool axis is greater than the radial distance of the chip divider at the other of the two cutting edges at its outermost point furthest from the tool axis, and / or such that the outer radial distance (r3) of the chip divider (12) at one of the two cutting edges (32) is smaller than the inner radial distance (r1) of the chip divider (11) at the other of the two cutting edges (31). [8] Drilling tool according to one of the preceding claims, wherein a radial width (b1, b2) of a chip divider, in particular at the interruption of the associated drill cutting edge, is selected from a range of 0.05 times to 0.25 times the diameter (d1) of the drilling area. [9] Drilling tool according to one of the preceding claims, in which at least one or each chip divider (11, 12, 13) is designed as a chip divider groove which forms an interruption at the respective drilling cutting edge (31, 32, 33), wherein preferably the at least one or each chip divider groove of the respective chip divider (11, 12, 13) has a substantially linear progression or a sequence of at least two or three linear sections inclined to each other, in particular inclined inwards towards the tool axis, wherein the linear extent of the chip divider groove or its sections in particular extends tangentially to a circle around the tool axis, or also has a progression that is at least partially curved, preferably convex to the tool axis. [10] Drilling tool according to claim 9, wherein at least one or each chip section groove (11, 12, 13) has a cross-section in the form of a trapezoid, wherein the trapezoid preferably opens in the forward direction or towards the drill cutting edge, in particular with an opening angle of between 45° and 90°, preferably at least approximately 60° and / or wherein at least one or each chip part groove of the respective chip divider (11, 12, 13) extends from the respective drilling cutting edge (31, 32, 33) into an adjacent clearance surface and optionally further clearance surface(s), wherein in particular the length of the extension of the chip part groove is adjustable by the clearance angle or the position of the clearance surface(s). [11] Drilling tool according to one of the preceding claims, wherein each cutting edge (31, 32, 33) is arranged and / or formed on an associated web (41, 42, 43), wherein at least one clearance surface adjoins each cutting edge on each web, in particular on an end face of the web, wherein in particular the clearance angle of the clearance surface is selected in a radially outer area between 3° and 15° or between 5° and 15°, in particular 6° or 10°, and preferably increases radially inwards, in particular to a value of a maximum of 40°, and / or wherein the clearance surface is in particular conical or produced with a conical surface grinding or is flat. [12] Drilling tool according to one of the preceding claims, comprising at least one and preferably at least two chip removal grooves (25) which begin in the drilling area (3) and / or whose axial length is greater than the maximum penetration depth of the drilling tool, so that the chip removal grooves can extend at any time into an area above or outside the workpiece surface and can remove the chips from the bore, wherein preferably one of the webs (41, 42, 43) runs between each pair of chip removal grooves (25) and / or wherein the chip removal grooves (25) and / or the webs (41, 42, 43) are spiraled around the tool axis, in particular at a constant or variable spiral angle, which is typically in an interval of 0° to 50°, in particular 20° to 35°, for example 30°. [13] Drilling tool according to one of the preceding claims, wherein at least one of the chip dividers, in particular at least one or each chip divider groove (11, 12), extends to an outlet (60) for coolant and / or lubricant, wherein the outlet (60) is preferably connected to a channel running in an associated web (41, 42, 43). [14] Drilling tool according to one of the preceding claims, wherein the diameter (d1) of the drilling area with respect to the tool axis is a maximum of 10 mm and / or in which a rake face is connected to each drilling cutting edge and the rake face is not provided with a chip forming surface or chip forming step. [15] Method for producing a bore with a cylindrical inner wall without threads, a) in which a drilling tool according to one of the preceding claims is used, b) in which the drilling tool is rotated in a predetermined forward direction (VD) about the tool axis (A) passing through the drilling tool during the creation of the bore and is simultaneously moved axially to the tool axis in a forward direction (VB) during an axial forward movement, c) in which the drilling tool is moved out of the created bore in an axial reverse direction opposite to the forward direction and continues to rotate in the forward direction (VD) during this process d) wherein an axial drilling feed of the forward movement of the drilling tool per revolution is set to at least 9% of the diameter of the drilling area of ​​the drilling tool per revolution, in particular at least 0.5 mm per revolution for a diameter of 5.5 mm, and in particular at least 15% of the diameter of the drilling area of ​​the drilling tool per revolution, in particular at least 0.8 mm per revolution for a diameter of 5.5 mm, and e) wherein a rotational speed for the rotation of the drilling tool is selected from a range between 1000 rpm and 20,000 rpm and / or wherein the axial speed when moving the drilling tool out of the bore is greater, preferably at least five times greater, than during the axial forward movement (VB).

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