TOOL AND METHOD FOR GENERATING A THREADED HOLE, THE TOOL HAVING CHIP DIVIDERS

Abstract

A tool for generating a threaded hole is rotatable in a rotational movement about a tool axis extending through the tool, and is movable in an axial forward direction axially of the tool axis. The tool comprises at least one thread generation area and at least one drilling area, which are rigidly motion-coupled to each other. The drilling area is provided for generating a core hole and is arranged axially offset to the tool axis with respect to the thread generation area. The thread generation area projects radially to the tool axis, runs along a helical line, and a predetermined winding sense of the thread to be generated, and has a working profile which corresponds to the thread profile of the thread to be generated. The drilling area has a drilling edge, and at least one chip divider is arranged on the drilling edge, interrupts the drilling edge.

Claims

1-21. (canceled)

22. A tool for generating a threaded hole, wherein: a) the tool is rotatable in a working movement in a rotational movement with a predetermined direction of rotation about a tool axis (A) extending through the tool and at the same time is movable in an axial forward direction axially of the tool axis, b) said tool comprises at least one thread generation area and at least one drilling area which are rigidly motion-coupled to each other, c) the drilling area is provided for generating a core hole and is arranged axially offset to the tool axis with respect to the thread generation area and/or is arranged in an area of the tool lying further forward in the forward direction, in particular at a front or free end, than the thread generation area, d) the thread generation area projects radially to the tool axis further outwards than the drilling area, e) the thread generation area runs along a helical line or thread helix with a predetermined thread pitch angle and a predetermined winding sense of the thread to be generated and has a working profile which corresponds to the thread profile of the thread to be generated, f) the drilling area has at least one drilling edge, and g) at least one chip divider is arranged on the drilling edge, which forms an interruption of the drilling edge.

23. The tool according to claim 22, wherein: the drilling area has a number n of at least two drilling edges which are arranged offset to one another in the direction of rotation, in particular by a pitch angle of 360°/n; at least one chip divider is arranged on each of the n drilling edges; and/or the radial diameter of the drilling area relative to the tool axis is at most 10 mm.

24. The tool according to claim 22, wherein: the radial distances of the chip dividers from the tool axis are different at different drilling edges in such a way that in a rotational projection or in the direction of rotation around the tool axis, an interruption formed by a chip divider at a first drilling edge is followed by a cutting area or a drill part cutting edge of a second drilling edge.

25. The tool according to claim 22, wherein the axial depth of the chip divider measured in the axial direction to the tool axis from the interruption of the cutting edge lies essentially in a range of 0.5/n to 1.1/n times, in particular 1/n times, the thread pitch of the thread generation area.

26. The tool according to claim 22, wherein: a radial width (b1, b2) of a chip divider interruption ranges from 0.05 times to 0.25 times the diameter (d) of the drilling area; and/or the rake face at each drilling edge is not provided with a chip forming surface or chip forming step.

27. The tool according to claim 22, wherein at least one chip divider is designed as a chip divider groove, which forms an interruption at the respective drilling edge.

28. The tool according to claim 27, wherein: at least one chip divider groove of the respective chip divider extends from the respective drilling edge, in particular into an adjacent free area or sequence of free areas, in particular with a substantially linear course or a sequence of at least two or three inclined to each other, in particular linear sections inclined inwards towards the tool axis, the linear extension of the chip groove or its sections running in particular in each case tangentially to a circle around the tool axis, or also with a course which is curved at least in sections, preferably convexly curved towards the tool axis

29. The tool according to claim 22, wherein at least one chip divider or chip divider groove has a cross-section in the shape of a triangle or trapezoid or dovetail or rectangle or double wave or rounding, in particular a semicircle, possibly with extended linear side walls.

30. The tool according to claim 22, wherein at least one chip divider is designed as a chip divider step or is designed as a chip divider groove extending on the rake face of the respective drilling edge

31. The tool according to claim 22, wherein: each drilling edge is arranged and/or formed on an associated drill web; at least one first free area, which adjoins the drilling edge, is formed on each drill web, in particular on an end face of the drill web; in particular the clearance angle of the first free areas in a radially outer area is selected between 3° to 15° or between 5° to 15°, in particular 6° or 10°, and preferably increases radially inwards, in particular up to a maximum of 40°; and/or the first free area is in particular cone-shaped or even.

32. The tool according to claim 31, wherein: at least one second free are, which adjoins the rear side of the first free area remote from the drilling edge, is formed on each drill web, in particular on an end face of the drill web; the second free area is more strongly exposed or is arranged at a larger clearance angle than the first free area; the clearance angle of the second free areas is selected in a radially outer area preferably in a range between 15° and 40° or between 20° and 40°, in particular 32°, and/or the second free areas are curved or flat.

33. The tool according to claim 22, wherein: at least one chip divider groove of the respective chip divider extends from the respective drilling edge into the first free area(s) lying behind it and usually also into the second free area, a length (l1, l2) of the extension of the chip divider groove being adjustable in particular by the clearance angle of the first and/or second free area.

34. The tool according to claim 22, wherein at least one or the chip groove extends to an outlet for coolant and/or lubricant in the associated drill web.

35. The tool according to claim 22, comprising: at least one and preferably at least two chip removal grooves, which start in the drilling area and continue through the thread generation area into a chip area which, viewed axially to the tool axis (A), directly adjoins the thread generation area on the side opposite the drilling area, webs being arranged and formed between the chip removal grooves at least in the chip area.

36. The tool according to claim 35, wherein: the chip removal grooves and the webs between them run twisted around the tool axis, in particular at a constant or variable twist angle, typically in an interval of 0° to 50°, in particular 20° to 35°, for example 30°; and/or on the webs in the front area, there is firstly one drilling web of the drilling area and then the thread tooth or teeth of the thread generation area.

37. The tool according to claim 35, wherein: the axial length of the chip removal grooves is greater than the maximum hole depth or penetration depth T.sub.max of the tool, so that the chip removal grooves always extend into an area above or outside the workpiece surface and can evacuate the chips from the threaded hole.

38. The tool according 35, wherein: web edges are formed at the outer transition areas between the webs and the chip removal grooves, at least in the chip removal area directly adjoining the thread generation area, which web edges are generally blunt or non-cutting and in particular follow the course of the chip removal grooves; and/or the radial diameter (d′) of the webs and thus of the web edges in the chip area is equal to or slightly smaller than the diameter (d) of the drilling area and thus of the core hole wall produced, in particular between 90% and 100%, for example 99.8%, of this diameter.

39. A method for generating a thread with a predetermined thread pitch and with a predetermined thread profile in a workpiece, comprising: a) using a tool for generating a threaded hole, wherein: (i) the tool is rotatable in a working movement in a rotational movement with a predetermined direction of rotation about a tool axis (A) extending through the tool and at the same time is movable in an axial forward direction axially of the tool axis, (ii) said tool comprises at least one thread generation area and at least one drilling area which are rigidly motion-coupled to each other, (iii) the drilling area is provided for generating a core hole and is arranged axially offset to the tool axis with respect to the thread generation area and/or is arranged in an area of the tool lying further forward in the forward direction, in particular at a front or free end, than the thread generation area, (iv) the thread generation area projects radially to the tool axis further outwards than the drilling area, (v) the thread generation area runs along a helical line or thread helix with a predetermined thread pitch angle and a predetermined winding sense of the thread to be generated and has a working profile which corresponds to the thread profile of the thread to be generated, (vi) the drilling area has at least one drilling edge, and (vii) at least one chip divider is arranged on the drilling edge, which forms an interruption of the drilling edge; wherein: b) the tool is moved into the workpiece in one working movement during first work phase, c) the working movement comprises a rotational movement with a predetermined direction of rotation about the tool axis of the tool and an axial feed movement of the tool in an axial forward direction axially of the tool axis, synchronised with the rotational movement according to the thread pitch of the thread generation area, such that a full rotation of the tool about the tool axis corresponds to an axial feed of the tool by the predetermined thread pitch, d) during the working movement, the drilling area of the tool generates a core hole in the workpiece and the thread generation area generates phase a thread in the inner wall of the core hole produced by the drilling area in the first working, the thread running under the predetermined thread pitch, the drilling area and the thread generation area executing the working movement together without changing their relative position to each other.

40. The method according to claim 39, wherein: a) in a deceleration movement following the working movement, the tool is moved further into the workpiece in the same forward direction as the working movement to a reversal point during a second working phase; and b) after reaching the reversal point, a reversing movement of the tool is initiated, with which the tool is moved out of the workpiece, wherein: c) the reversing movement comprises firstly a first reversing phase, during which the thread generation area of the tool is guided back into the thread of the generated thread, and then a second reversing phase, during which the thread generation area is guided out of the workpiece through the thread.

41. The method according to claim 39, wherein: a) the axial feed of the tool in relation to a full revolution, at least during part of the deceleration movement, is smaller than the thread pitch and is zero at the reversal point; and b) the thread generation area generates at least one, in particular closed or annular, circular or circumferential groove in the workpiece during the deceleration movement.

42. The method according to claim 39, wherein: a) the tool further comprises at least one and preferably at least two chip removal grooves, which start in the drilling area and continue through the thread generation area into a chip area which, viewed axially to the tool axis, directly adjoins the thread generation area on the side opposite the drilling area, webs (being arranged and formed between the chip removal grooves at least in the chip area; b) band chips produced in the drilling area due to the chip dividers are guided through the chip removal grooves, in particular are not already broken in the drilling area, and are broken between the webs, in particular the web edges, of the chip area on the one hand and the threaded hole wall provided with the thread produced by the thread generation area on the other hand; and c) the broken pieces of the band chips are guided through the chip removal grooves to the outside of the threaded hole.

Description

[0083] The invention is further explained below by means of exemplary embodiment. Reference is also made to the drawings in which

[0084] FIG. 1a shows a combined drilling and thread generating tool while generating a threaded hole,

[0085] FIGS. 2 to 10 show the generation of a threaded hole with a combined drilling and thread generating tool in successive process phases,

[0086] FIGS. 11 to 27 show different embodiments of a drilling area of a combined drilling and thread generating tool for the generation of a threaded hole, wherein each are shown schematically. Parts and sizes corresponding to each other are marked with the same reference signs in FIGS. 1 to 27.

[0087] First exemplary embodiments of the tool and process according to the invention are explained below using FIGS. 1 to 10.

[0088] A tool 2 is used to generate a threaded hole 5 in a workpiece 6. Tool 2 is a combination tool and generates both the core hole in the workpiece with the specified core hole diameter of the thread (in the solid material or in an already prefabricated, for example predrilled, or in a pre-drilled hole produced during the primary forming process such as casting or 3D printing) and the internal thread in the core hole, i.e. a thread turn 50 of an internal thread in the jacket wall or inner wall of the core hole. For this purpose, the tool is moved into the workpiece 6 in a working movement (or: a working stroke or thread generation movement), which is composed of a rotational movement around the tool axis on the one hand and an axial feed movement along the tool axis on the other hand.

[0089] Tool 2 is on the one hand rotatable or rotationally movable around a tool axis A running through tool 2 and on the other hand axially or translationally movable along or axially to tool axis A. These two movements are coordinated or synchronised, preferably by a control unit, in particular a machine control or NC control, while tool 2 penetrates a surface 60 of workpiece 6 and up to a hole depth TL into workpiece 6. The tool axis A remains stationary or in a constant position relative to the workpiece 6 during the generation of the threaded hole 5. The thread centre axis M of the threaded hole 5 is coaxial with the tool axis A or coincides with it during the process. The axial penetration depth (or: the axial feed) in the direction of the tool axis A measured from the workpiece surface 60 is designated T.

[0090] Tool 2 can preferably be driven by means of a coupling area on a tool shank 24 running 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, rotationally or in a rotary movement about its tool axis A in a forward direction of rotation VD and in an opposite reverse direction of rotation RD. Furthermore, tool 2 is axially movable in an axial forward movement VB or an opposite axial backward movement RB 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.

[0091] A working area 20 is provided at a free end area of tool 2 facing away from the coupling area of shank 21. The working area 20 comprises a drilling area 3 at the front end of the tool 2 and a thread generation area 4 axially offset with respect to the tool axis A to the rear of the drilling area 3 or to the shank 24 as well as preferably also chip removal grooves 25.

[0092] In the exemplary embodiments shown, the chip removal grooves 25 start in the drilling area 3 and continue through the thread generation area 4 into a cutting area 7, which, seen axially to the tool axis A, directly adjoins the thread generation area 4 on the side opposite to the drilling area 3. Between the chip removal grooves 25 webs (or: backs; or: ridges) 27 are arranged and formed, on which in the front area firstly drill webs of the drilling area 3 and then thread teeth or thread webs of the thread generation area 4 are formed. However, the individual areas such as the webs 27 and the chip removal grooves 25 and the drilling area 3 and the thread generation area 4 need not be integrated in this way, but can also be formed separately.

[0093] Preferably, the chip removal grooves 25 and the webs 27 in between run twisted around the tool axis A under a constant or variable twist 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 selected to be greater than the maximum hole depth or penetration depth T.sub.max of tool 2, i.e. in FIGS. 1 to 10 the chip removal grooves 25 always extend into an area above or outside the workpiece surface 60, in particular to a certain distance from the shank 24. In this way, at every stage of the process, the chips produced can be led out of the hole produced in the workpiece through the chip removal grooves 25.

[0094] In the exemplary embodiments shown, drilling area 3 includes frontal drill (main) cutting edges 31 and 32, which can be arranged in particular obliquely or conically, running axially forwards and can run towards or in a drill tip 33, in particular in a cone tapering towards the drill tip 33. These frontal drilling edges 31 and 32 are designed to cut in the forward direction of rotation VD, in the embodiment example shown they are right-cutting and remove material of the workpiece 6, which is axially in front of tool 2, during the forward movement VB with simultaneous rotation in the forward direction of rotation VD.

[0095] The drilling area 3 thus has an outer diameter or drill diameter d and generates a hole or core hole with this inner diameter d in the workpiece 6. The drilling edges 31 and 32 can also be called core hole cutting edges, as they generate the core hole of the threaded hole 5. The outermost dimension of the drill or core hole cutting edges 31 and 32, radial to the tool axis A, determines the core hole inner diameter d.

[0096] Drilling area 3 has two drill (main) cutting edges 31 and 32 in the exemplary embodiments shown in FIGS. 1 to 25. However, one or more than two, e.g. three or four, drilling edges may also be provided.

[0097] Located axially behind the drilling area 3 or the drilling edges 31 and 32 or axially offset in the opposite direction to the axial forward movement VB, the tool 2 comprises a thread generation area 4, which runs or is formed along a helix (or: helix, thread pitch), the pitch of which corresponds to the thread pitch P and the winding sense of which corresponds to the winding sense of the internal thread or thread turn 50 to be generated. In this sense, the helix is to be understood technically and not as a purely mathematical one-dimensional line. It also has a certain extension at right angles to the mathematical line, which corresponds to the corresponding dimension of the thread generation area 4.

[0098] The thread generation area 4 is motion-coupled with the drilling area 3 and thus the drilling area 3 and the thread generation area 4 move synchronously to each other and thus also in the working movement, which is composed of the axial movement VB or RB and the rotary movement VD or RD.

[0099] The winding sense of the thread generation area 4 as right-hand thread (or left-hand thread) corresponds to the winding sense resulting from the superposition of axial forward movement VB and forward rotary movement VD.

[0100] The thread generation area 4 generally projects further outwards radially to the tool axis A or has a greater radial outer distance to the tool axis A than the drilling area 3 or has a greater outer diameter D than the outer diameter d of the drilling area 3.

[0101] The thread generation area 4 comprises one or more, i.e. a number n greater than or equal to 1, thread teeth which are cutting and/or forming. Each thread tooth is formed or aligned or arranged along the helix. Each thread tooth has a thread tooth profile as an active profile, which is generally the outermost dimension or external profile of the thread tooth in a projection along the helix and which is formed or reflected in the workpiece during the thread forming movement, whether by cutting or by shaping or indenting.

[0102] If several (n>1) thread teeth are included in the thread generation area 4, these thread teeth are at least approximately offset from each other along the helical line (or in the axial direction). Such an arrangement along the helical line also includes embodiments in which the thread teeth are slightly laterally offset from an ideal line, for example in order to realise thread profiles with different machining on the thread free areas or a different division or superposition of the thread profiles on or to the overall thread profile. With regard to this arrangement of the thread teeth, it is only important that their arrangement is reflected in the working movement on a thread turn 50 in workpiece 6 with the same thread pitch P.

[0103] In the exemplary embodiments shown, two thread teeth 41 and 42 are provided, which are axially offset to each other, for example by half a thread pitch P/2, i.e. they are offset in the angular direction by half a turn or by 180°. However, it is also possible to have only one thread tooth or a number n>2, i.e. more than two thread teeth, which can in particular be offset to each other axially by P/n and circumferentially by 360°/n.

[0104] The thread teeth, in particular 41 and 42, project radially outwards from the tool axis A further than the drilling edges 31 and 32. The outside diameter D of the thread generation area 4 corresponds to the diameter of the generated thread turn 50 and thus of the threaded hole 5. The radial difference between the outermost dimension of the thread generating teeth and the outermost radial dimension of the core hole cutting edges corresponds in particular to the profile depth of the thread profile of the internal thread to be produced or, in other words, the difference between the radius D/2 of the thread root and the radius of the core hole d/2.

[0105] The thread profile of the internal thread, i.e. the cross-section through the thread turn 50, is produced by the thread profile composed of or superimposed by the individual active profiles of the thread teeth, e.g. 40 and 41, when the thread passes completely through the workpiece.

[0106] At the outer transition areas between the webs 27 and the chip removal grooves 25, web edges 28 are formed, at least in the chip area 7 directly adjoining the thread generation area 4, which are generally blunt or non-cutting and in particular follow the course of the chip removal grooves 25.

[0107] The diameter d′ of the webs 27 and thus of the web edges 28 arranged on the outside of the webs 27 in the chip area 7 is slightly smaller than the diameter d of the drilling area 3 and thus of the generated bore or core hole wall, for example between 90% and 98% of d, on the one hand to prevent chips from the chip removal grooves from entering the space between the webs 27 and the core hole wall, on the other hand to prevent chips from entering the space between the web edges 28 or and the threaded hole wall provided with thread 5, on the other hand to break (or: divide) long chips, in particular band chips, which are produced during the process, as will be explained later.

[0108] First of all, the process will be explained in more detail.

[0109] During a first working phase of the working movement (or: thread generation phase), tool 2 is used to generate the core hole by means of the drilling area 3 and immediately axially behind it and at least partially at the same time the thread turn 50 is generated in the core hole wall by means of the thread generation area 4. In this first working phase, the axial feed rate v along the tool axis A is adjusted and synchronised with the rotational speed for the rotary movement around the tool axis A in such a way that for one full revolution the axial feed corresponds to the thread pitch P.

[0110] In the FIGS. 2 to 6, tool 2 moves in the working movement of the first working phase in the axial forward movement VB and at the same time in a rotary movement in the forward direction of rotation VD.

[0111] As shown in FIG. 2, tool 2 with its drill tip 33 is first placed on the workpiece surface 60 and the drilling process is started (so-called spot drilling).

[0112] In FIG. 3, the drilling edges 31 and 32 have already penetrated into workpiece 6 and generate an upper area of the core hole, but the thread generation area 4 is still outside the workpiece 2.

[0113] In FIG. 4, the drilling edges 31 and 32 continue to cut the core hole and at the same time (or: synchronously) the thread generation area 4 now joins the process and begins to generate the thread here first with thread tooth 41 and shortly afterwards with thread tooth 42 in the core hole wall of the core hole already previously generated by drilling area 3.

[0114] In FIG. 5, this thread generation process is already more advanced and a threaded hole 5 of hole depth TL has already been produced and a thread turn 50 of thread generation area 4 has been produced.

[0115] Now, in a second working phase immediately following the first working phase, tool 2 is braked in a deceleration process (or: in a deceleration movement) in a rotation angle interval in such a way that the axial feed V at a rotation angle of 360°, i.e. at one full revolution, of tool 2 is smaller than the thread pitch P and decreases to zero. As a rule, the deceleration process or the second working phase starts at an axial feed related to a rotation angle of 360°, which corresponds to the thread pitch P of the first working phase, i.e. V=P, and then reduces the axial feed per 360° rotation angle to values below the thread pitch P, i.e. V<P. The deceleration process is to be understood as deceleration from the initial thread pitch V=P to zero at the end or at a reversal point, i.e. V=0, and does not have to involve a reduction of the axial feed V depending on the angle of rotation (deceleration acceleration) over the entire rotation angle interval. Rather, rotation angle intervals are also possible in which the axial feed is zero in relation to the rotation angle or is even temporarily negative, i.e. reverses its direction.

[0116] In a preferred embodiment this deceleration process is carried out in defined partial steps.

[0117] This deceleration movement in the second work phase leads to the fact that the thread generation area 4 now—in what is actually an atypical or non-functional way—generates at least a circular groove or circumferential groove or undercut in the core hole wall. The shape and number of circumferential grooves depends on the number and formation and distribution of the thread teeth. The process in the second work phase can therefore be described not only as a deceleration process but also as circular groove or circumferential groove or undercut generation movement, or in the case of a purely cutting tool also as a free cutting movement.

[0118] It would also be possible to carry out the undercut or deceleration movement, for example by suitable selection of the movement parameters or also by additional axial levelling movements, in such a way that the outer width on the thread profile, in particular the free areas, are no longer visible in the circumferential groove or disappear and/or the circumferential groove only has a cylindrical shape. This could improve or enable the screwability of the generated workpiece thread.

[0119] FIG. 6 shows the transition from the first working phase, in which the maximum thread depth T.sub.G is reached, to the second working phase.

[0120] The total depth or hole depth or total axial dimension of the threaded hole 5 after the second working phase is designated T.sub.max.

[0121] When the total depth or maximum threaded hole depth T.sub.max of threaded hole 5 is reached, tool 2 stops and reaches a reversal point.

[0122] In FIG. 7 this position is shown at the reversal point. One can see the circular groove 51, which was generated during the second working phase, for example, composed of two partial grooves.

[0123] A reversing or backward movement is now immediately initiated at the reversal point. The reversing or backward movement comprises an axial backward movement RB, which is directed in the opposite direction to the forward movement VB and a rotational movement in a backward direction of rotation RD, which is opposite to the forward direction of rotation, recognisable by the reversed arrow directions.

[0124] First of all, tool 2 is moved back through the circumferential groove(s) 51 to thread turn 50 in a first reversing phase, which is shown for example in FIG. 8.

[0125] Then, in a second reversing phase, tool 2 is moved or unthreaded outwards through the thread or thread turn 50 out of the threaded hole 5 and then the workpiece 6. Due to the smaller diameter d, the thread is not damaged by the drilling area 3 even during the reversing movement.

[0126] In the second reversing phase of the reverse movement RB, the axial feed and the rotary movement of tool 2 are again synchronised with each other according to the thread pitch P in order not to damage the thread.

[0127] A snapshot during the second reversing phase is shown in FIG. 9.

[0128] In FIG. 10, tool 2 has already completely left threaded hole 5. The threaded hole 5 is completely visible with its thread turn 50 of thread depth T.sub.G, the axially downwardly adjoining circumferential groove 51 and the further axially adjoining residual hole 53, which is only produced by the drill tip 33. The total maximum thread hole depth T.sub.max of the threaded hole 5 consists of the axial dimensions of the thread turn 50, i.e. the thread depth T.sub.G, and the circumferential groove 51 and the residual drill hole 53.

[0129] The thread axis or central axis of the thread with thread turn 50 is marked M and coincides with or is coaxial with tool axis A of tool 2 during the whole working movement, i.e. both in the first working phase and in the second working phase, and also during the reversing movement, i.e. both in the first reversing phase and in the second reversing phase.

[0130] Embodiments of the drilling area 3 are explained in the following with reference to further exemplary embodiments and FIGS. 11 to 27.

[0131] A first cutting edge 31 is formed on a first drill web 35 and a second cutting edge 32 on a second drill web 36.

[0132] A first chip removal groove 61 runs between the drill webs 35 and 36, seen in the forward direction of rotation VD, and a second chip removal groove 62 runs between the drill web 36 and the first drill web 35, again seen in the forward direction of rotation VD. The first drilling edge 31 is located on the first chip removal groove 61 and the second drilling edge 32 on the second chip removal groove 62.

[0133] The transition between the drilling edge 31 or 32 and the corresponding chip removal groove 61 or 62 forms a rake face (81 and 82 in FIGS. 11 and 12) on the drilling edge 31 or 32. The rake angles of these rake faces (81 and 82) on the drilling edges 31 and 32 are preferably selected in a range between −10° and +45°, whereby the rake angles preferably increase from the inside to the outside in relation to the tool axis, and can lie closer to the tool axis in a range between −10° and +10° and in the outer range lie in particular between 15° and 45°, preferably corresponding to the helix angle of the twisted chip removal grooves.

[0134] On the rear side of the drilling edge 31 or 32, which is turned away from the rake face or the associated chip removal groove 61 or 62, a first free area 63 or 64 is attached to the front face of the associated drill web 35 or 36. The rear side of the first free area 63 or 64 facing away from the drilling edge 31 or 32 is immediately followed by a second free areas 65 or 66, which is more strongly exposed than the first free area 63 or 64 or is arranged at a larger clearance angle, and which in particular essentially forms the remaining front face of the associated drill web 35 or 36 not already covered by the first free area 63 or 64.

[0135] The clearance angles of the first free areas 63 and 64 and the second free areas 65 and 66, i.e. the angles between the free area and a transverse plane running tangentially through the drilling edge perpendicular to the tool axis A, are generally selected so that, despite the high axial feed in accordance with the thread pitch P, friction of the end faces of the drill webs 35 and 36 formed by these free areas on workpiece 6 is avoided. The minimum clearance angle at a certain radius r can be calculated approximately according to the formula arctan ((axial feed per revolution/(2r π)), in this case arctan (P/(4r π)), i.e. it increases from the outside to the inside. As a rule, however, a larger clearance angle is selected to reliably prevent friction.

[0136] The clearance angle of the first free areas 63 and 64 directly adjacent to the drilling edges 31 and 32 is preferably selected between 5° to 15°, in particular 10°, in a radially outer area and increases radially inwards, in particular up to a −90°, corresponding to the roof angle of the drill tip 33. This ensures a stable drilling edge 31 or 32. The first free area 63 and 64 can be particularly cone-shaped or ground by cone-shaped grinding or can also be flat.

[0137] The clearance angle of the second free areas 65 and 66, on the other hand, is larger than that of the first free areas 63 and 64 and is preferably selected in a range between 20° and 40°, for example 32°. The second free areas 65 and 66 can also be generated with a curvature or even.

[0138] However, instead of the differently exposed free areas 63 and 65 or 64 and 66, a uniform free area with a correspondingly continuously variable clearance angle can also be provided.

[0139] In every second free area 65 and 66, an outlet 67 and 68 of a fluid channel, running through the drill web 35 and 36 respectively, discharges, for the supply of coolant and/or lubricant, which can run axially or also twisted.

[0140] The chip removal grooves 61 and 62 of the drilling area 3 preferably merge into (or: form the front area) of one chip removal groove 25 each and are preferably twisted as well. Correspondingly, the drill webs 35 and 36 preferably merge into (or:

[0141] form the front area) one web 27 each, preferably over one web of the thread generation area 4.

[0142] The drilling edges 31 and 32 are generally at least largely linear, but can also have a slightly curved, in particular in the forward direction of rotation VD convex, course at least in part. Preferably, the drilling edges 31 and 32 run at least partially parallel to each other.

[0143] The two drilling edges 31 and 32 of the shown drilling area 3 are located in particular on opposite sides of an axially running centre plane containing the tool axis A, i.e. slightly offset from the centre plane. The two drilling edges 31 and 32, for example, are arranged and designed essentially rotationally symmetrical about an angle of rotation of 180° or point-symmetrical to tool axis A.

[0144] The drilling edges 31 and 32 can run towards each other in the form of cross cuts towards the drill tip 33, which is located at the central tool axis A. In the centre or in the area of the cross-cutting edges, the rake angle and clearance angle approach each other. An angle of inclination a of the two drilling edges 31 and 32 to the tool axis A is preferably the same and can, for example, be between 90° and 135°, in particular 120°.

[0145] The tool is now equipped with chip dividers on the drilling edges, which break up the chips produced by the drilling edges and thus make them narrower. Surprisingly, this makes it possible to reduce the loads on the drilling edges that occur at the tool and during the process, in particular during the deceleration process during the second work phase, to such an extent that no tool breakage occurs. In addition, greater drilling depths can be achieved.

[0146] A first chip divider 11 is now arranged at the first drilling edge 31, in particular in the FIGS. 11 to 21, and a second chip divider 12 at the second drilling edge 32.

[0147] Each chip divider 11 or 12 forms a—dashed shown—interruption 21 or 22 of the respective drilling edge 31 or 32 and thus divides or separates these drilling edges 31 and 32 into an inner drill part cutting edge 31A in the inner area towards tool axis A and an outer drill part cutting edge 31B in the outer area away from tool axis A.

[0148] The radial distance r1 of the first chip divider 11 from the tool axis A is different, in the example of the figures smaller, selected than the radial distance r2 of the second chip divider 12. The radial distances r1 and r2 are preferably selected in such a way that there is no overlap between the chip dividers 11 and 12 in a rotary projection, i.e. they are still slightly spaced from each other. This means that the chips are divided differently and scoring at the bottom of the hole is avoided.

[0149] A radial width b1 of interruption 21 of chip divider 11 and a radial width b2 of interruption 22 of chip divider 12 are preferably chosen to be equal and/or preferably such that r1+b1<r2, thus avoiding radial overlapping of interruptions 21 and 22.

[0150] Preferred values are for the radial widths b1 and b2 a range of 0.05 d to 0.25 d and for the radial distance r1 a range of 0.05 d to 0.25 d and for the radial distance r2 a range of 0.25 d to 0.4 d.

[0151] In the FIGS. 11 to 21, the chip dividers 11 and 12 are designed as chip divider grooves, which extend at the front side of the drill webs 35 and 36 from the respective drilling edge 31 or 32 into the free area(s) 63 or 64 behind them and usually also into the free areas 65 and 66.

[0152] The lengths of the chip divider grooves or chip dividers 11 and 12 are designated 11 and 12 respectively and can be selected equal to each other and/or variable, in particular by varying the clearance angles or position of the free areas.

[0153] For a given depth t1 or t2, the length l1 or l2 of the chip divider grooves of chip dividers 11 and 12 can be adjusted, in particular, by how the free area 65 or 66 is inclined, i.e. which clearance angle is selected. With steeper orientation or larger clearance angles the length of the chip grooves is shorter and with smaller clearance angles or less steep orientation of the free areas the length of the chip grooves is greater. The free areas 65 and 66 and their comparatively large clearance angles ensure that the rear edges of the chip grooves do not rub against the workpiece.

[0154] The length or extension of the chip dividers or chip divider grooves is preferably selected so 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. This allows coolant and/or lubricant to be fed through the chip divider grooves to the cutting edge.

[0155] Depending on the radial distance r1 and r2 of the chip divider grooves of the chip dividers 11 and 12 on the one hand and the radial distances and cross-sections of the outlets 67 and 68 on the other hand, the chip divider groove can only extend up to the vicinity of the outlet as shown for the chip divider groove 12 e.g. in FIGS. 12 to 15 or even run directly into or through the outlet as shown for the chip divider groove 11 and the outlet 67 in FIGS. 12 to 15. Even in an arrangement close to the outlet a significant part of the coolant and/or lubricant already reaches the cutting edge through the chip groove and can develop a cooling or lubricating effect there, in addition to the coolant and/or lubricant already reaching the cutting edge from the outside or via the outer sides.

[0156] The extension of the chip divider groove from the drilling edge into the free areas or also into the chip surface can be designed in completely different shapes and lengths.

[0157] Thus, as for example in FIGS. 12 to 14, a linear extension can be selected which has the advantage of being easily produced 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.

[0158] Furthermore, a curved course of the extension of the chip grooves is also possible, as shown for example in FIG. 15. Here, for example, one can choose a course along a circle around the tool axis A or another curved curve.

[0159] The length of a curved course is then to be determined as the arc length, although only a tangential length l1 or l2 is drawn in FIG. 15.

[0160] In an embodiment not shown, at least one of the chip grooves or each chip groove may extend from the drilling edge into the free area or into the rake face, also in the form of two, three or more linear sections, which are inclined to each other or arranged at an angle to each other. 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. In this way the chip divider groove can be approximated to a course along the circumference or along a curvature, in particular a circular curvature, in particular around the tool axis A, in the manner of a partial polygon. Each linear section can now preferably be generated again by a linear movement of a grinding wheel.

[0161] For example, the linear chip divider groove of chip divider 11 shown in FIG. 13 can be extended by another linear chip divider groove inclined inwards towards the tool axis A at an angle to it, which adjoins behind the chip divider groove 11 and can, for example, partially run through outlet 67. The chip divider grooves obtained now form linear sections of a common connected chip divider groove. A further linear chip groove can also be connected to the linear chip groove 12.

[0162] In addition, chip grooves with consecutive linear and curved sections can also be provided.

[0163] The axial depths t1 and t2 of the chip divider grooves of chip dividers 11 and 12 measured in axial direction to the tool axis A from interruption 21 or 22 can be selected in a wide range and are preferably equal to each other.

[0164] In an advantageous embodiment, the axial depths t1 and t2 of the chip divider grooves of the chip dividers 11 and 12 are adjusted within a range of exactly or approximately the axial feed P/2 of the tool between the two drilling edges 31 and 32 and thus the chip thickness, so that the chip can be completely divided or at least weakened sufficiently so that it can then be broken. In general with a number n of drilling edges, the axial depth of the chip divider at the interruption of the drilling edge is essentially in a range of P×0.5/n to P×1.1/n, in particular P×0.8/n to P×1/n, preferably at P/n.

[0165] The chip divider 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.

[0166] The position, shape and length as well as the cross-section of the chip divider grooves can be selected within wide limits depending on the desired chip pitch and other functions and parameters. Thus the chip formation can be influenced in different ways by different tearing and compression and also the wear can be positively influenced.

[0167] A preferred embodiment with an almost triangular or narrow trapezoidal cross-section of the chip divider grooves of chip dividers 11 and 12 is shown in FIGS. 11 to 15. These straight chip grooves with such a cross section according to FIG. 11 could be produced with a thread grinding wheel already used when generating the thread generation area, which would be a simplification from the manufacturing point of view.

[0168] However, a dovetail-shaped cross-section of the chip grooves of chip dividers 11 and 12 in the form of an undercut trapezoid as shown in FIG. 16 is also possible, or a rectangular cross-section of the chip grooves of chip dividers 11 and 12 as shown in FIG. 17, or a trapezoidal cross-section of the chip grooves of chip dividers 11 and 12 with a wider groove base as shown in FIG. 18.

[0169] FIG. 19 shows an embodiment of a wave-shaped double groove as chip divider 11 and 12.

[0170] FIG. 20 shows an embodiment with a round, in particular semi-circular, cross-section of the chip divider grooves of chip dividers 11 and 12.

[0171] FIG. 21 shows an embodiment form with a cross-section of the chip grooves of chip dividers 11 and 12 which is round in the groove base, in particular semi-circular, and continues linearly and parallel to each other on the groove side walls.

[0172] FIGS. 22 and 23 now show an embodiment of drilling area 3, in which the chip dividers 11 and 12 each have two chip divider grooves 11A and 11B or 12A and 12B extending from the chip removal groove 61 or 62 or the rake face 81 or 82 into the drilling edge 31 or 32, by which the drilling edge 31 or 32 is divided into three partial cutting edges 11A, 11B and 11C and 12A, 12B and 12C respectively.

[0173] Finally, in the embodiment according to FIGS. 24 and 25, chip divider 11 or 12 comprises a chip divider step instead of a chip divider groove, which can be produced by an approximately 90° face grinding. Here the chip divider step forms the interruption of the drilling edge, which divides it into two partial cutting edges, whereby the drill chip is also divided.

[0174] FIG. 26 shows in a superposition the drilling area according to FIG. 11 in two positions rotated 180° against each other and offset by a corresponding axial feed of P/2. One can see the radially offset chip dividers 11 and 12 and that the area recessed by one chip divider is then removed by the following drilling edge. It can also be seen that the chip dividers 11 and 12 can completely cut through the chips due to their axial depth of about P/2. However, if necessary, weakening the chips by a furrow at a lower axial depth of the chip dividers than P/2 would also be sufficient to divide the chips in their radial dimension.

[0175] In FIG. 27 a special and advantageous embodiment is shown, in which a first clearance angle of the first free area(s) immediately behind the drilling edge(s) of 6° is selected, whereby only the first free area 63 is visible behind the drilling edge 31, and a second clearance angle of the second free area(s) behind the respective first free area of 32° is selected, whereby only the second free area 65 is visible behind the first free area 63. Furthermore, the preferred angle of twist of the chip removal grooves, drawn at the chip removal groove 61, is 30°.

[0176] Continuous drilling edges without chip dividers generate short and curled up drill chips (comma chips) which are well suited for the process. These typically have the length of the circumferential distance or pitch angle between successive drilling edges and curl up at different radii due to different cutting speeds and path lengths. However, tests have shown that these smaller drill chips can become entangled and jammed in the thread turn 50 produced by the thread generation area 4, thereby disrupting or even making the process impossible, so that the desired thread depths of 2 to 2.5 times the diameter D could not be achieved, and tool breakage frequently occurred.

[0177] However, the chip dividers according to the invention and the described embodiments now generate additional band chips in drilling area 3, i.e. long continuous and little curled up drill chips, which are actually useless for the process and can lead to tool breakage, at least the desired ones. Thus, an person skilled in the art would not consider chip splitters for this combined tool, because they would even aggravate the chip problem from the expectation and from the experience of the expert, instead of improving it.

[0178] The invention is now based on the surprising observation that, nevertheless, the combined tool and process according to the invention practically no band chips are generated or discharged from the chip removal grooves 25. Investigations into why this is so have not yet been completed. From the present point of view, the inventors explain these extremely surprising observations as follows. Due to their size, the band chips produced in the drilling area 3 due to the chip dividers do not settle in thread turn 50. Rather, the band chips moving through the chip removal grooves 25 between the webs 27, in particular the web edges 28, the chip area 7 and the core hole wall provided with the thread turn 50, i.e. not smooth, are strongly deformed and thus broken. The thread turn 50 thus appears to act as a kind of chip divider for the band chips. With a smooth wall, the band chips would not be able to be broken. This results in broken band chips or broken pieces of band chips which become so small that they are harmless for the process. This unexpected effect and surprising but pleasing finding has now led to the fact that the desired thread depths can easily be achieved with the chip dividers.

[0179] Drilling area 3 can also have guide areas on its outer wall, which can serve to guide tool 2 in the generated hole and for this purpose are either adjacent to the core hole wall or only slightly spaced from it. Instead of or in addition to the guide areas, circumferential cutting edges or jacket cutting edges can also be provided, which machine or prepare the jacket wall of the core hole by removing material from areas of the workpiece 6 that are radially outwardly adjacent to the tool axis A. These shell cutting edges can be used to achieve a sufficient surface quality also of the shell wall or the inner wall of the core hole and run in particular mainly parallel or slightly inclined backwards (to reduce friction) to the tool axis A at a radial distance d/2 from the tool axis A, which corresponds to half the inner diameter of the core hole. The guide areas or circumferential or jacket cutting edges can be designed and/or arranged directly adjacent to the frontal drilling edges or can be slightly offset axially from these.

[0180] In particular, a cylindrical guide area can be arranged on the radially outwardly projecting outer surfaces of the drill webs 35 and 36, at least in the area of the first free areas 63 and 64. This serves to stabilise the axially comparatively short drilling area 3.

[0181] In an embodiment not shown, the drill tip 33 can also be designed as a centring tip.

LIST OF REFERENCE SIGNS

[0182] 2 Tool [0183] 3 Drilling area [0184] 4 Thread generation area [0185] 5 Threaded hole [0186] 6 Workpiece [0187] 7 Chip area [0188] 11, 12 Chip divider [0189] 11A, 11B Chip groove [0190] 12A, 12B Chip groove [0191] 20 Working area [0192] 21, 22 Interruption [0193] 24 Shank [0194] 25 Chip removal groove [0195] 27 Web [0196] 28 Web edge [0197] 31, 32 Drilling edges [0198] 31A, 31B Drill part cutting edge [0199] 31C Drill part cutting edge [0200] 32A, 32B Drill part cutting edge [0201] 32C Drill part cutting edge [0202] 33 Drill tip [0203] 41, 42 Thread tooth [0204] 50 Thread turn [0205] 51 Circumferential groove [0206] 53 Drill hole [0207] 60 Workpiece surface [0208] 61, 62 Chip removal groove [0209] 63, 64 Free area [0210] 65, 66 Free area [0211] 67, 68 Outlet [0212] 81, 82 Rake face [0213] A Tool axis [0214] b1, b2 Width (of the chip divider) [0215] d Core hole diameter [0216] D Threaded hole diameter [0217] l1, l2 Length (of the chip divider) [0218] M Thread centre axis [0219] P Thread pitch [0220] RB Backward movement [0221] RD Reverse direction of rotation [0222] T Penetration depth [0223] T.sub.G Thread depth [0224] T.sub.L Threaded hole depth [0225] t1, t2 Depth (of the chip divider) [0226] VB Forward movement [0227] VD Forward direction of rotation [0228] α Angle of inclination