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 located at a front or free end, but preferably does not have a thread-forming area, 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 ≥ 2, d) wherein at least one chip divider is arranged on at least one or each of the n cutting edges, forming an interruption of the respective cutting edge and e) 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 multiplied by the axial feed of the drilling tool per revolution or from a range of 0.5 to 1.1 multiplied by the axial feed of the associated cutting edge relative to the immediately preceding cutting edge in the direction of rotation.

Description

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

[0002] Drilling tools, especially twist drills, for creating holes (without threads) are usually designed with continuous cutting edges running from the inside to the outside (see, for example, DE 10 2016 221 363 A1). This creates shorter, curling drill chips because the radially varying cutting speeds and circumferential lengths of the removed material across the cutting edge lead to deformation and curling of the chip. These shorter chips are generally well suited for the drilling process. Drill chips are divided into spiral chips or spiral chip pieces, spiral chips or spiral chip pieces, and comma chips.

[0003] In rather rare applications with larger drilling diameters, where particularly wide drilling chips are produced, so-called chip dividers can be provided in the cutting edges of drilling tools, which are combined with downstream chip forming stages or chip breakers (see e.g. DE 37 04 196 A1, DE 10 2009 024 256 A1 or US 3,076,357).

[0004] The chip breakers form interruptions in the cutting edges and can be designed as grooves or recesses or even as steps on the respective cutting edge.

[0005] Such chip breakers divide the particularly wide drilling chips associated with large drill diameters into narrower chips. However, this results in significantly longer and less curled chips, known as ribbon chips. Such ribbon chips are unusable for most processes, particularly because they can become trapped between the tool and the bore wall, causing damage and even tool breakage. Therefore, in drilling tools with chip breakers, the state-of-the-art chip breakers are combined with downstream chip forming stages or chip breakers to simultaneously reshape and break the ribbon chips.

[0006] EP 3 199 279 A1 discloses a drilling tool with chip breakers, which is primarily intended for drilling holes in workpieces made of carbon fiber reinforced plastics, particularly in the aircraft industry. With these carbon fiber reinforced plastics, there is a risk of delamination of fiber layers due to the feed load during drilling and of drill burrs and fiber projections, which in particular cause fraying of the hole edge. The drilling tool of EP 3 199 279 A1 is intended to counteract this problem. The known drilling tool according to EP 3 199 279 A1 is designed in the manner of a twist drill with a drill tip and two tip cutting edges tapering at an angle to the central drill tip. As shown, for example, in the Fig. As shown in Figures 1 to 6 of EP 3 199 279 A1, each of the two front-side cutting edges 7 is divided into three partial cutting edges 21, 22 and 23. The first inner partial cutting edge 21 and the outermost third partial cutting edge 23 are separated from one another by a recess or groove 8 with a triangular cross-section, i.e. a V-shape. At the end of the groove 8, a second partial cutting edge is formed, which runs inwards from the third partial cutting edge and is connected to the first partial cutting edge 21 via a ridge 16, which is not designed to be cutting. The three partial cutting edges 21, 22 and 23 each run in a straight line, the first partial cutting edge 21 and the third partial cutting edge 23 on a common straight line and the second partial cutting edge 22 on a straight line inclined inwards thereto. The reduced feed forces acting on the recess due to this cutting edge design and the inclined partial cutting edges are in Fig. 5 and the associated figure description of EP 3 199 279 A1. The recess 8 runs from the frontal cutting edge with the three partial cutting edges in a straight line backwards into the back or the flank 6 of the respective area of ​​the drilling tool. A spiral chip groove 2, which forms a cutting surface 2a, runs along the partial cutting edges 21, 22 and 23. The radial distances between the recesses on the two different cutting edges are chosen to be the same in most embodiments, thus completely overlapping in a rotational projection. In the embodiment of Fig. 28, the radial distances between the recesses of the two cutting edges are slightly different, but the two recesses still partially overlap in a rotational projection around the tool axis, ie the innermost radial distance of the recess located radially further outwards is smaller than the outer radial distance of the recess located radially further inwards. Fig. The axial depth of the recess 8 shown schematically in Figure 5 is approximately equal to the axial drilling feed fr and the Fig. The axial depth of the recess 18 shown schematically in Figure 24 is approximately twice as large as the axial drilling feed fr.

[0007] Typical values ​​for the axial drilling feed for known twist drills are between 0.1 and 0.3 mm per revolution.

[0008] From DE 77 10 873 U1, another drilling tool with chip breakers is known, the cutting head of which has at least two main cutting edges arranged at equal angular distances from one another in the circumferential direction and aligned with a 0° rake angle parallel to the central axis of the cutting head, each of which is formed by an outer cutting edge and an inner cutting edge extending at an obtuse angle to the central axis, which each converge in axial cutting edge tips, which are all arranged at equal radial distances from the central axis and at the same height in the axial direction, wherein the inner cutting edge of at least one main cutting edge extends in the radial direction beyond the central axis and the outer cutting edge of each main cutting edge has a recess acting as a chip breaker,All chip breaker recesses have a triangular contour of equal cross-section. The triangular edge closest to the cutting edge is straight and aligned at least substantially parallel to the central axis, while the other triangular edge, forming the base of the recess, extends approximately within a radial plane. The outer corners of the chip breaker recesses formed in the intersection area of ​​the axially parallel triangular edge with the outer cutting edge are all arranged at the same radial distance from the central axis and at the same axial height, as are the inner corners formed in the intersection area of ​​the two triangular edges inside the recesses.

[0009] The invention is based on the object of providing a drilling tool and a method for creating a hole in a workpiece, each of which allows for high drilling feed rates. In particular, drilling feed rates of at least 9% of the diameter of the drilling area of ​​the drilling tool per revolution, in particular 0.5 mm for a diameter of 5.5 mm, and even more, are to be achieved.

[0010] Suitable embodiments and objects according to the invention for achieving this object are specified in particular in the patent claims, which are directed to a drilling tool, in particular having the features of independent patent claim 1, and to a method for producing a bore using such a tool, in particular having the features of patent claim 18.

[0011] Further embodiments and developments according to the invention result from the respective dependent patent claims.

[0012] The claimable feature combinations and subject-matter according to the invention are not limited to the selected wording and the selected references to the patent claims. Rather, any feature of one claim category, for example a tool, can also be claimed in another claim category, for example a method. Furthermore, any feature in the patent claims, regardless of their references, can be claimed in any combination with one or more other features in the patent claims. Furthermore, any feature described or disclosed in the description or drawing can be claimed on its own, independently or detached from the context in which it appears, alone or in any combination with one or more other features described or disclosed in the patent claims or in the description or drawing.

[0013] 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 movement with a predetermined direction of rotation about a tool axis extending through the drilling tool and is simultaneously movable in an axial forward movement in a forward direction axially to the tool axis, b) wherein the drilling tool comprises at least one drilling region which is arranged in a region of the drilling tool lying in the forward direction at a front or free end, but preferably does not have a thread-generating region, c) wherein the drilling area has a number n of drilling cutting edges which are arranged offset from one another in the direction of rotation, where n is a natural number with n ≥ 2, and d) wherein at least one chip splitter is arranged on at least one or each of the n drilling cutting edges, which forms an interruption of the respective drilling cutting edge.

[0014] The drilling area therefore has a number n ≥ 2, i.e. at least two, drilling cutting edges which are arranged offset from one another in the direction of rotation, in particular with the same pitch by a pitch angle of 360° / n or with unequal pitch with different pitch angles.

[0015] According to claim 1, in a further variant, the axial depth of the or each chip breaker, measured in the axial direction relative to the tool axis from the associated cutting edge, is selected from a value range of 0.5 to 1.1 times the axial feed of the associated cutting edge relative to the immediately preceding cutting edge in the direction of rotation. This is particularly useful in the case of unequal pitch.

[0016] In a further variant according to claim 1, the axial depth of the or each chip breaker, measured in the axial direction relative to the tool axis, is selected from a value range of 0.5 / n to 1.1 / n multiplied by the axial feed of the drilling tool per revolution. This is particularly useful for equal pitches.

[0017] In a particularly advantageous embodiment, the axial depth of the or each chip splitter, measured in the axial direction to the tool axis, from the associated cutting edge is selected to be at least approximately equal to the axial feed of the associated cutting edge relative to the immediately preceding cutting edge in the direction of rotation

[0018] In a further advantageous embodiment, the axial depth of the or each chip breaker, measured in the axial direction relative to the tool axis, is selected to be at least approximately 1 / n multiplied by the axial feed rate of the drilling tool per revolution. This is particularly useful for equal pitches.

[0019] Thanks to these advantageous measures, the axial depth of the chip splitters is in the range of the chip thickness and the chip can be completely split or at least weakened sufficiently to then be split.

[0020] In an advantageous embodiment, the radial distances of the chip splitters from the tool axis on at least two of the n cutting edges are different from one another, specifically in such a way that in a rotational projection in the predetermined direction of rotation about the tool axis, a chip splitter on a first cutting edge is followed by a cutting area of ​​a subsequent second cutting edge, and / or in such a way that the radial distance of the chip splitter on one of the two cutting edges at its innermost point closest to the tool axis is greater than the radial distance of the chip splitter on the other of the two cutting edges at its outermost point furthest away from the tool axis, and / or in such a way that the outer radial distance of the chip splitter on one of the two cutting edges is smaller than the inner radial distance of the chip splitter on the other of the two cutting edges.

[0021] A radial width of a chip splitter, in particular at the interruption of the associated drilling cutting edge, is preferably selected from a range of 0.05 times to 0.25 times the diameter of the drilling area.

[0022] Advantageously, at least one or each chip splitter is designed as a chip splitter groove which forms an interruption at the respective cutting edge.

[0023] In one embodiment, at least one chip-splitting groove of the respective chip splitter extends from the respective cutting edge into an adjacent flank or sequence of flanks. The length of the chip-splitting groove can now be adjusted, in particular, by the clearance angle or the position of the flank(s).

[0024] In another embodiment, the chip groove can also extend along the chip surface of the respective cutting edge.

[0025] The extension of the chip-cutting groove(s) preferably follows a substantially linear course or a sequence of at least two or three linear groove sections inclined relative to one another, in particular inclined inward toward the tool axis (or convexly). The linear extension of the chip-cutting groove or its sections can, in particular, each run tangentially to a circle around the tool axis.

[0026] Furthermore, a course of the extension of the chip part groove(s) that is at least partially curved, preferably convex to the tool axis, is also possible.

[0027] In a preferred embodiment, at least one or each chip-splitting groove of the respective chip splitter can have a substantially linear profile or a sequence of at least two or three linear sections inclined relative to one another, in particular inclined inward toward the tool axis, wherein the linear extension of the chip-splitting groove or its sections runs, in particular, tangentially to a circle around the tool axis. However, the chip-splitting groove can also have a profile that is curved, at least in sections, preferably convexly curved toward the tool axis.

[0028] It has been found to be expedient that at least one or each chip-parting groove has a cross-section in the form of a trapezoid, wherein the trapezoid preferably opens 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°.

[0029] In various embodiments, at least one chip splitter or chip splitter groove may also have a cross-section in the form of a triangle or trapezoid or dovetail or rectangle or a double wave or a curve, in particular a semicircle, optionally with extended linear side walls.

[0030] At least one chip splitter can also be designed as a chip splitter step.

[0031] In general, each cutting edge is arranged and / or formed on an associated web, with at least one flank adjoining each cutting edge on each web, in particular on an end face of the web. The flank angle of the flank is preferably in a radially outer region between 3° and 15° or between 5° and 15°, in particular 6° or 10°, and preferably increases radially inward, in particular to a value of up to a maximum of 40°. The flank is in particular conical or produced with a conical surface grind, but can also be planar or flat.

[0032] Preferably, the drilling tool comprises at least one and preferably at least two chip removal groove(s) beginning in the drilling area for removing the drilling chips

[0033] 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 can extend into an area above or outside the workpiece surface at any time and remove the chips from the drilled hole.

[0034] One of the webs now preferably runs between each two chip removal grooves.

[0035] Chip removal grooves and / or webs preferably run in a spiral manner 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°.

[0036] In advantageous embodiments, at least one chip-parting groove extends to an outlet for coolant and / or lubricant in the associated web, wherein the outlet is preferably connected to a channel running in an associated web or represents its mouth.

[0037] The radial diameter of the drilling area relative to the tool axis is preferably a maximum of 10 mm (i.e. a size for which chip breakers are not normally used in twist drills).

[0038] In all embodiments, the chip surface on each cutting edge is preferably not provided with a protruding chip-forming surface or chip-forming step, but rather runs continuously with a comparatively slight curvature. This allows the drilling area to be designed more compactly and axially shorter.

[0039] A further advantageous embodiment provides a guide region on the outer circumference of the drilling tool, particularly one that is axially offset from the drilling region. The guide region has a diameter that corresponds to the outer diameter of the drilling region or is only slightly smaller than it, for example, by 0.5 to 2%. Thus, the guide region preferably serves to guide the drilling tool itself in the created bore.

[0040] The guide area is preferably divided into individual guide sections, each of which is provided on one of the webs.

[0041] Preferably, the guide area, preferably each guide section on each web, has at least one circumferentially extending lubrication groove, preferably at least two axially spaced-apart 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.

[0042] In a particular embodiment, a corner break is provided on the outer areas of the cutting edges. The corner break angle of the corner break relative to the radial direction can be selected within a range of 0° to 60°, preferably between 15° and 30°, and / or an angle of the corner break (70) relative to the tool axis (A) can be selected from an interval between 0° and the amount of the helix angle, in particular of the chip removal grooves (25), preferably 0°. A radially measured corner break width of the corner break is preferably between 0.05 mm and 0.4 mm.

[0043] The method according to the invention, in particular claim 19, is intended for producing a bore with a cylindrical inner wall, in particular without a thread. A drilling tool according to the invention is used, and the following method steps—typical for a drilling process per se—are performed with it: - the drilling tool is rotated in a forward rotational movement in a predetermined forward direction around the tool axis passing through the drilling tool when creating the hole and is simultaneously moved in an axial forward movement in a forward direction axially to the tool axis, - The drilling tool is then 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 makes thread creation impossible.

[0044] In contrast to known drilling methods using twist drills, according to the invention, a high axial drilling feed f of the forward movement of the drilling tool per revolution of 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 of 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, is preferably used. The feed fz per drilling cutting edge is then obtained by multiplying the drilling feed f per revolution (360°) by the ratio of the pitch angle and 360°.

[0045] The rotational speed of the drilling tool, at least during the creation of the bore, is preferably selected from a range between 1,000 rpm and 20,000 rpm. The axial speed when moving the drilling tool out of the bore is generally greater, preferably at least five times greater, than during the axial forward movement.

[0046] The invention will be further explained below with reference to exemplary embodiments. Reference is also made to the drawings, in which Fig. 1 a drilling tool in a perspective side view, Fig. 2 an enlarged perspective side view of the drilling area of ​​the drilling tool according to Fig. 1, Fig. 3 an enlarged perspective side view of the drilling area with subsequent guide area of ​​the drilling tool according to Fig. 1, Fig. 4 an enlarged perspective front view of the drilling area of ​​the drilling tool according to Fig. 1, Fig. 5 a sectional view of the drilling area of ​​the drilling tool according to Fig. 1 according to the Fig. 1 cross-section marked BB, Fig. 6 a sectional view of the drilling area of ​​the drilling tool according to Fig. 1 according to the Fig. 1 cross-section marked CC, Fig. 7 a perspective front view of the drilling area of ​​a drilling tool with a corner break protection and Fig. 8 a perspective side view of the drilling area of ​​the drilling tool according to Fig. 7 are shown schematically. Corresponding parts and sizes are shown in the Fig. 1 to 8 are provided with the same reference numerals.

[0047] The drilling tool (hereinafter also referred to as the tool) is designated 2 and is used to create a cylindrical bore, in particular a blind hole or through hole, and is designed for this purpose with a drilling area 3, but generally does not include a thread-generating area. If the created bore is to be provided with a thread, a subsequent step can be performed using a separate thread-generating tool.

[0048] The drilling tool 2 is preferably driven in a rotational or rotary motion about its tool axis A in a forward rotational direction VD by means of a coupling region 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 can be provided in the machine tool and / or drive or machine tool spindle. An outer diameter of the shank 24 is designated d2.

[0049] A drilling area 3 is provided at a free end area or front end of the drilling tool 2 facing away from the coupling area of ​​the shaft 24. The drilling area 3 has an outer diameter or bore diameter d1 and creates a bore with this inner diameter d1 in the workpiece (not shown). With its drill tip 33, the drilling area 3 of the rotating tool 2 is placed on the workpiece surface, and the drilling process is started.

[0050] The drilling tool 2 is, on the one hand, rotatable or rotationally movable about a tool axis A running through the drilling tool 2 and, on the other hand, axially or translationally movable along or axially to the tool axis A.

[0051] To create the hole, the drilling tool 2 is moved into a workpiece (not shown) in a working movement consisting of a rotational movement around the tool axis and an axial feed movement along the tool axis A. The drilling area 3 creates the hole by machining. During this drilling process, the tool axis A generally coincides with the center axis of the hole.

[0052] When the bottom of the hole or the maximum drilling depth is reached, the drilling tool 2 is moved out of the created hole in a return movement in the axial reverse direction opposite to the forward direction of the working movement. During the return movement or when moving the drilling tool out of the hole, a significantly higher axial speed is generally selected than during the working movement during drilling, for example, an axial speed 5 to 50 times higher. The drilling tool continues to rotate during the return movement, and the direction of rotation of the drilling tool remains unchanged during the return movement compared to the working movement, thus corresponding to the forward direction of rotation VD.

[0053] The rotational speed N during drilling is generally selected between 1,000 rpm (revolutions per minute) and 20,000 rpm, usually depending on the machine tool and the workpiece, as well as the diameter of the drilling tool. For example, tangential peripheral speeds at the outer diameter of between 30 and 300 m / min are achieved. During withdrawal from the hole, the rotational speed can be selected lower, but is generally simply maintained.

[0054] The present drilling tool 2 according to the invention is particularly suitable and intended for high axial drilling feeds f.

[0055] The axial feed f of the drilling tool during the axial feed movement during drilling (drilling feed) is, in the preferred embodiment, 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 diameter d1) and can, without restriction of generality, reach up to 1.5 mm and even up to 2 mm per revolution. The drilling feed f can be adapted to the diameter d1 of the drilling area 3 of the drilling tool 2; with a larger diameter d1, the drilling feed f is or can generally be selected to be larger.

[0056] Such a significantly higher drilling feed rate compared to known twist drills is made possible by the special design of the drilling tool according to the invention, which is explained in more detail below using exemplary embodiments.

[0057] In the illustrated embodiments, the drilling area 3 comprises two end-face drilling (main) cutting edges 31 and 32, which can be arranged, in particular, obliquely or conically or with a predetermined curvature, extending axially forward and can run towards or in a drill tip 33, in particular in a cone tapering towards the drill tip 33 and / or via a transverse cutting edge 34 connecting the two drilling edges 31 and 32 via the drill tip 33. These end-face drilling edges 31 and 32 are designed to cut in the forward direction of rotation VD, right-cutting in the illustrated embodiment, and during the forward movement VB with simultaneous rotational movement in the forward direction of rotation VD, they remove material from the workpiece 6, which lies axially in front of the drilling tool 2, by machining. In an embodiment not shown, the drill tip 33 can also be designed as a centering tip.

[0058] Furthermore, chip removal grooves 25 are provided on the tool 2, which begin in the drilling area 3 and continue into the shank 24. Webs (or ridges) 35 and 36 are arranged and formed between the chip removal grooves 25. The first drilling edge 31 is formed on the first drilling land 35, and the second drilling edge 32 is formed on the second drilling land 36, in each case in the front area or on the end face of the respective land 35 or 36.

[0059] Preferably, the chip removal grooves 25 and the intermediate webs 35 and 36 run spirally around the tool axis A at a constant or variable helix angle, which typically lies in an interval of 0° to 50°, in particular 20° to 35°, for example 30°, but can also run parallel or axially to the tool axis A. The axial length of the chip removal grooves 25 is preferably selected to be greater than the maximum hole depth or penetration depth of the tool 2, i.e. the chip removal grooves 25 extend into an area above or outside the workpiece surface. As a result, the chips produced can be guided outwards from the hole created in the workpiece through the chip removal grooves 25 at any stage of the process.

[0060] On each cutting edge 31 or 32, the associated chip removal groove 25 forms a corresponding chip face. The chip angles of these chip faces on the cutting edges 31 and 32 are preferably selected in a range between -10° and +45°, with the chip angles preferably increasing from the inside to the outside relative to the tool axis, and closer to the tool axis, they can be in a range between -10° and +10°, and in the outer region, they are in particular between 15° and 45°, preferably corresponding to the helix angle of the helix chip removal grooves 25.

[0061] On the rear side of the cutting edge 31 or 32 facing away from the chip surface or associated chip removal groove 25, there is a clearance surface 63 or 64, which is arranged on the front surface of the associated drill web 35 or 36.

[0062] The clearance angles of the flank surfaces 63 and 64, i.e. the angles between the flank surface and a transverse plane running tangentially through the cutting edge perpendicular to the tool axis A, are generally selected such that, despite the preferably high axial feed f, friction between the end faces of the drill webs 35 and 36 formed by these flank surfaces and the workpiece 2 is avoided. The minimum clearance angle at a specific radius r can be approximately calculated using the formula arctan (axial feed per revolution / (2r π)), i.e. here arctan (f / (4r π)), and thus increases from the outside to the inside. However, a larger clearance angle is generally selected to reliably prevent friction.

[0063] The clearance angle of the first flanks 63 and 64 adjacent to the cutting edges 31 and 32 is preferably selected between 5° and 15°, in particular 10°, in a radially outer region and increases radially inward, in particular up to the roof angle of the drill tip 33. This ensures a stable cutting edge 31 or 32. The flanks 63 and 64 can, in particular, be conical in shape or be produced by conical grinding or even be flat.

[0064] The flanks 63 and 64 are kept comparatively narrow by a respective frontal recess 61 and 62 created behind them in the direction of rotation in the associated web 35 or 36, so that they lie in particular in an angular segment of a maximum of 12° each around the tool axis A. The recesses 61 and 62 form further flanks adjoining the flanks 63 and 64, each having a larger clearance angle than the flanks 63 and 64. However, in an embodiment not shown, a further preferably flat flank can also be provided directly behind the flank 63 or 64 and in front of the recess 61 or 62, having a larger clearance angle, for example 20° to 40°, in particular 30°, than the flank 63 or 64.

[0065] In each of the recesses 61 and 62 there opens an outlet 67 or 68, for example of a round or convex cross-section, of a fluid channel running through the respective web 35 or 36 for supplying coolant and / or lubricant, which, like the web 35 or 36, can run axially or also in a twisted manner.

[0066] According to the invention, the drilling tool now features chip breakers on the cutting edges. These break up the chips generated by the cutting edges, thereby narrowing them and, in particular, producing strip chips. These strip 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 processing problems with strip chips were not observed during investigations.

[0067] A first chip splitter 11 is arranged on the first drilling cutting edge 31 and a second chip splitter 12 is arranged on the second drilling cutting edge 32.

[0068] However, chip breakers do not have to be provided on all drilling cutting edges and / or more than one chip breaker can be provided on one drilling cutting edge.

[0069] Each chip splitter 11 or 12 forms an interruption 21 or 22 of the respective drilling cutting edge 31 or 32. In the illustrated embodiments, the chip splitter 11 or 12 divides or separates the associated drilling cutting edge 31 and 32 into an inner drilling cutting edge 31A or 32A in the inner region towards the tool axis A and an outer drilling cutting edge 31B or 32B in the outer region away from the tool axis A.

[0070] The radial distance r1 of the first chip splitter 11 from the tool axis A is selected to be different from the radial distance r2 of the second chip splitter 12. The radial distances r1 and r2 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 splitters 11 and 12, i.e., they are still somewhat radially spaced from one another. As a result, in the rotational projection, a drilling cutting edge of the subsequent drilling cutting edge lies behind a chip splitter of a drilling cutting edge, and the chips are thus divided differently and their length is limited. Furthermore, scoring at the bottom of the hole is avoided.

[0071] A radial width b1 of the interruption 21 of the chip splitter 11 and a radial width b2 of the interruption 22 of the chip splitter 12 are preferably selected to be equal and / or preferably selected such that the outer radial distance r3 = r2 + b2 of the further inner chip splitter 12 is smaller than the inner radial distance r1 of the other chip splitter 11, thereby avoiding an overlap of the interruptions 21 and 22 in the rotational projection.

[0072] Preferred values ​​are selected for the radial widths b1 and b2 from a range of 0.05 d1 to 0.25 d1 and for the radial distance r1 from a range of 0.05 d1 to 0.25 d1 and for the radial distance r2 from a range of 0.25 d1 to 0.4 d1.

[0073] In a preferred embodiment, the chip dividers 11 and 12 are designed as chip-dividing grooves which extend on the end face of the drill webs 35 and 36 from the respective drill cutting edge 31 and 32 into the free surfaces 63 and 64 behind them and, as a rule, also into the recesses 61 and 62 and open there.

[0074] The lengths of the chip-parting grooves or chip dividers 11 and 12 are designated l1 and l2 respectively and can be selected to be equal to one another and / or to be variable, in particular by varying the clearance angles or the position of the flanks 63 and 64 as well as the position and depth of the recesses 61 and 62.

[0075] For a given depth t1 or t2, the length l1 or l2 of the chip-splitting grooves of chip breakers 11 and 12 can be adjusted, in particular, by the inclination of the flank surface 63 or 64, i.e., the selected clearance angle. With a steeper orientation or larger clearance angles, the length of the chip-splitting grooves is shorter, and with smaller clearance angles or a less steep orientation of the flank surfaces, the length of the chip-splitting grooves is longer. The flank surfaces 63 and 64 and their comparatively large clearance angles, as well as the recesses 61 and 62, ensure that the rear edges of the chip-splitting grooves do not rub against the workpiece.

[0076] Preferably, the length or extent of the chip splitters or chip splitter grooves is selected such that they extend as close as possible to the outlet for the coolant and / or lubricant, in particular the outlets 67 and 68 in the drill webs 35 and 36, respectively. As a result, coolant and / or lubricant can be guided through the chip splitter grooves to the drill cutting edge.

[0077] Depending on the radial distance r1 and r2 of the chip-parting grooves of the chip dividers 11 and 12 on the one hand and the radial distances and cross sections of the exits 67 and 68 on the other hand, the chip-parting groove can only extend to the vicinity of the exit, as in the case of the chip-parting groove 11 in Fig. 4 or even directly into the exit or through the exit as in the chip part groove 11 and the exit 67 in Fig. 4. Even when arranged near the outlet, a significant portion of the coolant and / or lubricant already reaches the cutting edge through the chip guide groove and can exert a cooling or lubricating effect there, in addition to the coolant and / or lubricant that already reaches the cutting edge from the outside or via the outer sides.

[0078] The extension of the chip groove from the cutting edge into the flanks or into the chip face can be designed in very different shapes and lengths.

[0079] For example, as in Fig. 4, a linear extension can be selected which has the advantage of being easy to produce with a grinding wheel, whereby the linear extension can be tangential to a circle around the tool axis A or also oblique to a tangential direction and the length l1 or l2 is measured along the linear extension.

[0080] Furthermore, a curved profile for the chip breaker grooves is also possible. For example, one can choose a profile along a circle around the tool axis A or another curved curve. The length of a curved profile should then be determined, in particular, as an arc length.

[0081] In an embodiment not shown, at least one of the chip-shaping grooves or each chip-shaping groove can extend from the cutting edge into the flanks or into the rake face, also in the form of two, three, or more, particularly linear, consecutive sections, which are particularly inclined to one another or arranged at an angle to one another. The linear extension of each section of the chip-shaping groove(s) can be tangential to a circle around the tool axis A or oblique to a tangential direction.

[0082] This allows the chip-cutting groove to be approximated to a course along the circumference or along a curve, in particular a circular curve, particularly around the tool axis A, in the manner of a partial polygon. Each linear section can then preferably be generated again by a linear movement of a grinding wheel. Chip-cutting grooves with successive linear and curved sections can also be provided.

[0083] The axial depths t1 and t2 of the chip separating grooves of the chip separators 11 and 12 measured in the axial direction to the tool axis A from the interruption 21 or 22 can be selected within a wide range and are preferably equal to one another.

[0084] According to the invention, the axial depths t1 and t2 of the chip-splitting grooves of the chip breakers 11 and 12 are set within a range of exactly or approximately half the axial feed (axial drilling feed) f of the drilling tool, particularly with evenly distributed drill cutting edges or arranged at the same pitch angles. Generally, with a number n of drill cutting edges, the axial depth of the chip breaker at the drill cutting edge is essentially in a range from fx 0.5 / n to fx 1.1 / n, in particular fx 0.8 / n to fx 1 / n, preferably f / n.

[0085] Alternatively, the axial depth of each chip breaker is set in a range of 0.5 to 1.1 times the axial feed fz of the associated cutting edge relative to the immediately preceding cutting edge in the direction of rotation. Preferably, the axial depth of the chip breaker is at least approximately equal to this axial feed fz per cutting edge. This is particularly useful in the case of unequal pitch, i.e., when the cutting edges are not arranged at the same pitch angle to each other.

[0086] In these variants according to the invention, the axial depth of the chip splitters is thus adjusted in the range of the chip thickness, so that the chip can be completely split or at least sufficiently weakened so that it can then be easily formed or broken.

[0087] The chip-parting 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.

[0088] 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 chip formation to be influenced differently by varying degrees of tearing and compression, and wear can also be positively influenced.

[0089] In a preferred embodiment, the chip-splitting grooves of the chip breakers 11 and 12 have a trapezoidal cross-section, at least at the cutting edge 31 and 32, respectively, but in particular also throughout. This trapezoid opens toward the front or in the forward direction with an opening angle φ, which is selected in particular from a range of 45° to 90°, preferably approximately 60°. This configuration has proven advantageous with regard to clearance in the feed direction.

[0090] However, a dovetail-shaped cross-section of the chip-parting 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-parting grooves of the chip dividers 11 and 12, or a triangular cross-section or an at least partially convexly curved or round cross-section, also a cross-section comparable to a roughing toothing on milling cutters.

[0091] In a preferred embodiment, the drilling tool 2 has a guide region 4 on its outer circumference, which is axially set back from the drilling region 3 and is formed along a substantially cylindrical surface and / or has a diameter that corresponds to the outer diameter d1 of the drilling region 3 or is only slightly smaller, for example by 0.5 to 2%. This guide region 4 thus serves to guide the drilling tool 2 in the created bore and prevents or reduces deflections of the tool that can occur due to the high drilling feed and the resulting higher deformation forces. The guide region 4 is divided into individual guide sub-regions, one on each of the webs 35 and 36, which are separated from one another by the chip removal grooves 25.

[0092] To reduce the frictional heat due to the sliding of the guide region 4 on the inner bore wall, the guide region 4 has at least one circumferentially extending lubrication groove on each web 35 and 36 in each guide sub-region; in the illustrated embodiments, two axially spaced-apart lubrication grooves 41 and 42. Each lubrication groove(s) can run along a helix, in particular at the pitch angle resulting from the axial feed f or fz, i.e., a helix with the axial feed f per revolution or fz per cutting edge as the pitch. Another course, including a pitch-free course of the lubrication groove(s), is also possible.

[0093] Through the lubrication grooves 41 and 42, the guide area 4 is sufficiently lubricated with the lubricant, in particular oil, supplied during the drilling process, particularly by forming a hydrodynamic lubricating film. The frictional heat between the sliding surfaces of the guide area 4 of the drilling tool 2 and the inner wall of the workpiece bore is thereby significantly reduced. The lubricant flows, in particular, from the chip removal grooves 25 through the lubrication grooves 41 and 42 to the outer surface of the guide area 4.

[0094] Instead of or in addition to the guide areas, circumferential cutting edges or shell cutting edges can also be provided, which machine or prepare the shell wall of the bore by machining areas of the workpiece 6 that adjoin radially to the outside of the tool axis A. These shell cutting edges can serve to achieve a sufficient surface quality of the shell wall of the bore and, in particular, run predominantly parallel or slightly inclined backwards (to reduce friction) to the tool axis A at a radial distance d1 / 2 from the tool axis A, which corresponds to half the bore diameter. The guide areas or circumferential or shell cutting edges can be formed and / or arranged directly adjacent to the front-side drilling cutting edges or can also be slightly offset axially from them.

[0095] The cutting edges 31 and 32 are generally at least largely linear, but may also have a slightly curved profile, at least in part, particularly a convex curve in the forward direction of rotation VD. Preferably, the cutting edges 31 and 32 run at least partially parallel to each other.

[0096] The two drilling edges 31 and 32 of the illustrated drilling area 3 are located, in particular, on opposite sides of an axially extending center plane containing the tool axis A. The two drilling edges 31 and 32 are arranged and configured, for example, essentially rotationally symmetrical about a rotation angle of 180° or point-symmetrical to the tool axis A, except, of course, for the differently arranged chip breakers 11 and 12, respectively.

[0097] In embodiments not shown, only one drilling cutting edge or more than two, for example three or four or five or six, drilling cutting edges may be provided, i.e. generally n ≥ 1 drilling cutting edges.

[0098] The cutting edges 31 and 32 can extend toward the drill tip 33 located near the central tool axis A via cross-cutting edges, such as the cross-cutting edge 34. In the center or in the area of ​​the cross-cutting edges, the rake angle and clearance angle approach each other. The angle of inclination of the two cutting edges 31 and 32 relative to the tool axis A is preferably the same and can be, for example, between 90° and 135°, in particular 120°.

[0099] The drilling tool or at least the drilling area 3 can be made, in particular, of hard metal or HSSE or PCD and / or coated with a diamond coating (diamond-like carbon) as a sliding layer. The chip removal grooves can be polished smooth, at least partially, particularly on the chip surfaces. The drilling tool can be manufactured at least partially using additive manufacturing. The cutting edges can be provided with a rounded edge.

[0100] In order to protect the cutting edge in the outer area of ​​the cutting edge and thus increase the service life and reduce wear, in the embodiment according to Fig. 7 and Fig.8, a corner break 70 is attached or provided. A corner break angle β of the corner break 70 to the radial direction is in the range of 0° to 60°, preferably between 15° and 30°. A radially measured corner break width e of the corner break 70 is preferably between 0.05 mm and 0.4 mm. The corner break 70 is preferably ground in the axial direction and preferably does not follow the helix. Therefore, an angle to the axial direction or tool axis A of 0° is preferred. In general, angles to the tool axis A between 0° and the amount of the helix angle, in particular of the chip removal grooves 25, are possible. List of reference symbols 2 drilling tools 3 Drilling area 4 Management area 7 chip area 11, 12 chip splitters 11A, 11B chip groove 12A, 12B chip groove 20 work area 21, 22 Interruption 24 shaft 25 chip removal groove 31, 32 drilling cutting edges 31A, 31B Drilling part cutting edge 32A, 32B drilling part cutting edge 33 drill bit 34 Cross cutting edge 35, 36 Drilling bridge 41, 42 Lubrication groove 61, 62 recess 63, 64 open space 67, 68 Exit 70 Corner break A tool axis b1, b2 width (of the chip breaker) d1, d2 diameter e corner break width f axial drilling feed l1, l2 length (of the chip breaker) t1, t2 axial depth (of the chip breaker) VB forward movement VD direction of rotation φ opening angle β corner break angle

Claims

[1] Drilling tool for producing a hole with a cylindrical inner wall, a) wherein the drilling tool is rotatable in a rotary movement with a predetermined direction of rotation (VD) about a tool axis (A) extending through the drilling tool and at the same time is movable in an axial forward movement (VB) in a forward direction axially to the tool axis, b) wherein the drilling tool comprises at least one drilling region (3) which is arranged in a region of the drilling tool lying in the forward direction at a front or free end, but preferably does not have a thread-generating region, c) wherein the drilling area has a number n of drilling cutting edges which are arranged offset from one another in the direction of rotation, where n is a natural number with n ≥ 2, d) wherein at least one chip splitter is arranged on at least one or each of the n cutting edges, which forms an interruption of the respective cutting edge and e) wherein the axial depth of the or each chip breaker, measured in the axial direction to the tool axis, is selected from a range of 0.5 / n to 1.1 / n multiplied by the axial feed of the drilling tool per revolution or from a range of 0.5 to 1.1 multiplied by the axial feed of the associated drilling cutting edge relative to the immediately preceding drilling cutting edge in the direction of rotation. [2] Drilling tool according to claim 1, in which the drilling cutting edges are arranged offset from one another in the direction of rotation by a pitch angle of 360° / n in the case of the same pitch or with different pitch angles in the case of unequal pitch. [3] Drilling tool according to claim 1 or 2, in which the axial depth of the or each chip splitter, measured in the direction axial to the tool axis from the associated drilling cutting edge, is selected to be at least approximately equal to the axial feed of the associated drilling cutting edge relative to the immediately preceding drilling cutting edge in the direction of rotation. [4] Drilling tool according to one of claims 1 to 3, in which the axial depth of the or each chip splitter measured in the direction axial to the tool axis is selected to be at least approximately 1 / n multiplied by the axial feed of the drilling tool per revolution. [5] Drilling tool according to one of the preceding claims, in which the radial distances (r1, r2, r3) of the chip splitters (11, 12) from the tool axis (A) are different on at least two of the n cutting edges (31, 32), such that in a rotational projection in the predetermined direction of rotation about the tool axis, a chip splitter on a first cutting edge is followed by a cutting area of ​​a subsequent second cutting edge, and / or such that the radial distance of the chip splitter on one of the two cutting edges at its innermost point closest to the tool axis is greater than the radial distance of the chip splitter on 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 splitter (12) on one of the two cutting edges (32) is smaller than the inner radial distance (r1) of the chip splitter (11) on the other of the two cutting edges (31). [6] Drilling tool according to one of the preceding claims, in which a radial width (b1, b2) of a chip splitter, in particular at the interruption of the associated drilling cutting edge, is selected from a range of 0.05 times to 0.25 times the diameter (d1) of the drilling area. [7] Drilling tool according to one of the preceding claims, in which at least one or each chip splitter (11 and 12) is designed as a chip splitter groove which forms an interruption at the respective drilling cutting edge (31, 32). [8] Drilling tool according to claim 7, in which at least one or each chip-parting groove of the respective chip splitter (11 and 12) has a substantially linear course or a sequence of at least two or three linear sections inclined towards one another, in particular inclined inwards towards the tool axis, wherein the linear extension of the chip-parting groove or its sections in particular runs tangentially to a circle around the tool axis, or also has a course which is at least partially curved, preferably convexly curved to the tool axis. [9] Drilling tool according to one of claims 7 and 8, in which at least one or each chip-parting groove (11 and 12) has a cross-section in the form of a trapezoid, wherein the trapezoid preferably opens 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°. [10] Drilling tool according to one of claims 7 to 9, in which at least one or each chip-parting groove of the respective chip splitter (11 and 12) extends from the respective cutting edge into an adjacent flank and optionally further flank(s), wherein in particular a length (l1, l2) of the extension of the chip-parting groove is adjustable by the clearance angle or the position of the flank(s) (65 or 66). [11] Drilling tool according to one of the preceding claims, in which each drilling cutting edge (31, 32) is arranged and / or formed on an associated web (35, 36), wherein at least one flank (63, 64) adjoins each drilling cutting edge (31, 32) on each web (35, 36), in particular on an end face of the web, wherein in particular the clearance angle of the flank (63, 64) is selected in a radially outer region between 3° to 15° or between 5° to 15°, in particular 6° or 10°, and preferably increases radially inwards, in particular to a value of a maximum of 40°, and / or in which the flank is in particular conical or produced with a conical surface grind 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 or 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. [13] Drilling tool according to claim 11 or claim 12, in which one of the webs (35, 36) runs between each two chip removal grooves (25) and / or in which the chip removal grooves (25) and / or the webs (35, 36) run twisted around the tool axis, in particular at a constant or variable twist angle, which is typically in an interval of 0° to 50°, in particular 20° to 35°, for example 30°. [14] Drilling tool according to one of the preceding claims, in which at least one or each chip-parting groove (11, 12) extends to an outlet (67, 68) for coolant and / or lubricant, wherein the outlet (67, 68) is preferably connected to a channel running in an associated web (35 or 36). [15] Drilling tool according to one of the preceding claims, in which the diameter (d1) of the drilling area relative to the tool axis is a maximum of 10 mm and / or in which a chip surface adjoins each cutting edge and the chip surface is not provided with a chip forming surface or chip forming step. [16] Drilling tool according to one of the preceding claims, further comprising a guide region (4), in particular axially offset from the drilling region (3), on its outer circumference, which guide region has a diameter which corresponds to the outer diameter (d1) of the drilling region (3) or is only slightly smaller than this, for example by 0.5 to 2%, wherein the guide region (4) preferably serves for the self-guiding of the drilling tool (2) in the bore produced and / or is preferably divided into individual guide sub-regions, each of which is provided on one of the webs (35 and 36). [17] Drilling tool according to claim 16, wherein the guide region (4), preferably each guide section on each web (35 and 36), has at least one lubrication groove running in the circumferential direction, preferably at least two lubrication grooves (41 and 42) spaced axially from one another, for supplying lubricant, in particular oil, into the guide region (4) during the drilling process, wherein preferably each lubrication groove(s) runs along a helix with a pitch corresponding to the axial feed per revolution or per cutting edge. [18] Drilling tool according to one of the preceding claims, in which a corner break (70) is provided on the outer regions of the cutting edges (31 and 32), wherein in particular a corner break angle (β) of the corner break (70) to the radial direction is in the range from 0° to 60°, preferably between 15° and 30°, and / or a radially measured corner break width (e) of the corner break (70) is preferably between 0.05 mm and 0.4 mm and / or an angle of the corner break (70) to the tool axis (A) is selected from an interval of 0° and the amount of the helix angle, in particular of the chip removal grooves (25), preferably at 0°. [19] Method for producing a bore with a cylindrical inner wall without thread, 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 forward rotational movement in a predetermined forward direction of rotation (VD) around the tool axis (A) extending through the drilling tool when producing the bore and is simultaneously moved in an axial forward movement (VB) in a forward direction axially to the tool axis, c) in which the drilling tool is moved out of the produced bore in an axial backward direction opposite to the forward direction and is meanwhile still rotated in the forward direction of rotation (VD). [20] Method according to claim 19, wherein an axial drilling feed of the forward movement of the drilling tool per revolution of 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 of 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, is set. [21] Method according to claim 19 or 20, in which a speed for the rotation of the drilling tool is selected from a range between 1000 rpm and 20,000 rpm and / or in which 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).

Images