Tapping tool and method for producing a threaded bore

Abstract

A tapping tool for producing a threaded bore having an internal thread in a workpiece. The tapping tool has a main cutting edge on its drill tip and a thread profile trailing in a tapping direction. The method has a tapping stroke in which the tapping tool is driven into the workpiece at a tapping feed rate in the tapping direction and at a tapping speed synchronized therewith and the main cutting edge of the tool produces a core hole bore and the tool thread profile forms an internal thread on the inner wall of the core hole bore. Chips are produced in the tapping stroke, which are conveyed out of the threaded bore in a chip removal direction opposite to the tapping direction and collide with thread flanks of the internal thread facing toward the chips to be removed.

Claims

1. A tapping tool for producing a threaded bore having an internal thread in a workpiece, wherein the tapping tool can be driven into the workpiece in a tapping stroke, and the tapping tool can be led out of the threaded bore in a reversing stroke, the tapping tool comprising: a clamping shaft and an adjoining tapping body, along the longitudinal axis of the tapping body at least one flute extends up to a frontal main cutting edge on the drill tip, on which main cutting edge a rake face delimiting the flute and a frontal free surface of the drill tip converge, wherein the flute is delimited by at least one drill web in the circumferential direction of the tool and the rake face of the flute merges into an outer circumferential rear face of the drill web while forming a secondary cutting edge, and wherein the secondary cutting edge and the frontal main cutting edge converge at a radially outer main cutting edge corner, wherein a thread profile having at least one thread profile tooth is formed on the outer circumferential rear face of the drill web, wherein the tool thread profile has at least one reversing tooth having a thread flank cutting/forming edge, by which a flank allowance can be removed and/or formed from a plurality of thread flanks, which face toward the chips to be removed in the tapping stroke, of the internal thread to be produced during the reversing stroke.

2. The tapping tool as claimed in claim 1, wherein in the tapping stroke, the tapping tool can be driven into the workpiece at a tapping feed rate in the tapping direction and at a tapping speed synchronized therewith, and the tool main cutting edge produces a core hole bore and the tool thread profile forms the internal thread on the inner wall of the core hole bore, and/or in the reversing stroke, the tapping tool can be led out of the threaded bore in the reversing direction at opposing reversing feed rate and reversing speed synchronized therewith, so that the tool thread profile can be led in the thread turn of the internal thread out of the threaded bore, and/or chips are produced in the tapping stroke, which are conveyed out of the threaded bore in a chip removal direction opposite to the tapping direction and collide with the thread flanks of the internal thread, which face toward the chips to be removed.

3. The tapping tool as claimed claim 1, wherein the reversing tooth formed on the drill web rear face protrudes radially outward beyond the main cutting edge corner by a reversing tooth height, and/or the thread flank cutting edge of the reversing tooth merges into a reversing cutting edge at a radially inner cutting edge inside corner, and the inner thread vertex is deburred by the reversing cutting edge in the reversing stroke.

4. The tapping tool as claimed in claim 3, wherein the reversing cutting edge extends in the drill longitudinal direction, and/or the outer circumferential drill web rear face and the rake face of the flute converge at the reversing cutting edge, and/or the reversing cutting edge and the secondary cutting edge are formed on drill web longitudinal edges which lie opposite in the drill circumferential direction.

5. The tapping tool as claimed in claim 1, wherein a tooth web formed on the drill web rear face adjoins the at least one thread profile tooth and/or the reversing tooth in the drill circumferential direction, and/or the thread profile teeth and/or the reversing tooth are each formed as a forming tooth having corresponding forming edges and/or as a cutting tooth having corresponding chip-removing cutting edges or as a combination thereof.

6. The tapping tool as claimed in claim 1, wherein the reversing tooth and the thread profile tooth are connected to one another via a tooth web formed on the drill web rear face, and/or the tooth web has end faces facing away from one another in the drill circumferential direction, which respectively form the thread profile tooth and the reversing tooth.

7. Tapping tool as claimed in claim 1, wherein the tooth web has a has a radially outer web vertex surface and a web flank surface facing toward the drill tip and a web flank surface facing away from the drill tip, and/or the web surfaces are at least partially formed as free surfaces, which are inoperative in the tapping stroke and/or in the reversing stroke, and the web vertex surface merges at a first circumferential web edge into the web flank surface facing toward the drill tip, and/or the web vertex surface merges at a second circumferential web edge into the web flank surface facing away from the drill tip, and at least one of the two circumferential web edges is formed as a circumferential groove cutting edge, by which the circumferential groove adjoining the bore internal thread is formed, by cutting, in the groove forming stroke.

8. A method for producing a threaded bore in a workpiece by a tapping tool as claimed in claim 1, comprising driving the tapping tool into the workpiece in a tapping stroke, and leading the tapping tool out of the threaded bore in a reversing stroke.

9. The method as claimed in claim 8, wherein a groove forming step takes place between the tapping stroke and the reversing stroke, in which the tapping stroke in the tapping direction is lengthened by a groove forming stroke, namely with the formation of a circumferential groove adjoining the internal thread without a thread pitch, in which the thread profile of the internal thread can rotate without load, and/or by providing the circumferential groove, it is also possible for the tapping tool to produce a circumferential thread countersink in the bore opening of the bore using a cutting edge, wherein the circumferential thread countersink is produced during the above groove forming step.

10. A tapping tool for producing a threaded bore having an internal thread in a workpiece, wherein the tapping tool can be driven into the workpiece in a tapping stroke, and the tapping tool can be led out of the threaded bore in a reversing stroke, wherein a groove forming step takes place between the tapping stroke and the reversing stroke, in which the tapping stroke is extended by a groove forming stroke in a tapping direction, the tapping tool comprising: a clamping shaft and an adjoining tapping body, and at least one flute extends along the longitudinal axis of the tapping body up to a frontal main cutting edge on the drill tip, on which main cutting edge a rake face delimiting the flute and a frontal free surface of the drill tip converge, wherein the flute is delimited by at least one drill web in the circumferential direction of the tool and the rake face of the flute merges into an outer circumferential rear face of the drill web while forming a secondary cutting edge, and wherein the secondary cutting edge and the frontal main cutting edge converge at a radially outer main cutting edge corner, wherein a thread profile having at least one thread profile tooth is formed on the outer circumferential rear face of the drill web, wherein the tool thread profile is formed having at least one circumferential groove cutting edge, by which the circumferential groove adjoining the bore internal thread is formed in the groove forming stroke.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) The invention and its advantageous designs and refinements and the advantages thereof are explained in greater detail hereinafter on the basis of drawings.

(2) In the figures:

(3) FIG. 1 shows a threaded blind hole formed in a workpiece in a side sectional view;

(4) FIG. 2 shows a view from the front of a tapping tool;

(5) FIG. 3 a side view of the tapping tool;

(6) FIG. 4 another side view of the tapping tool

(7) FIG. 5 views which illustrate method steps for producing the threaded blind hole shown in FIG. 1;

(8) FIG. 6 additional views which illustrate method steps for producing the threaded blind hole shown in FIG. 1;

(9) FIG. 7 additional views which illustrate method steps for producing the threaded blind hole shown in FIG. 1;

(10) FIG. 8 additional views which illustrate method steps for producing the threaded blind hole shown in FIG. 1;

(11) FIG. 9 shows an enlarged partial view in which a chip removal during the tapping stroke is illustrated;

(12) FIG. 10 shows an enlarged partial view in which a material removal during the reversing stroke is illustrated;

(13) FIG. 11 shows views of a tapping tool according to a further exemplary embodiment;

(14) FIG. 12 shows views of a tapping tool according to a further exemplary embodiment;

(15) FIG. 13 shows views of a tapping tool according to a further exemplary embodiment;

(16) FIG. 14 shows views of a tapping tool according to a further exemplary embodiment; and

(17) FIG. 15 shows a view corresponding to FIG. 10.

(18) A finished threaded blind hole bore 1 is shown in FIG. 1. The hole 1 is machined with its bore base 3 to a target drilling depth t.sub.B in a workpiece 5 by means of so-called one-shot drilling, which will be explained later with reference to FIGS. 5 to 8. The bore 1 has a circumferential thread countersink 7 at its bore opening, which merges into an internal thread 9 in the further downward course. The internal thread 9 extends along the bore axis A to a usable target thread depth t.sub.G. As can also be seen from FIG. 1, a thread turn 15 of the internal thread 9 opens with a thread runout 11 into a circumferential groove 13. This groove does not have a thread pitch and is formed between the internal thread 9 and the bore base 3, viewed in the axial direction. The thread 15 has a radially outer thread base 17 as well as lateral upper and lower thread flanks 18, 19, which merge radially on the inside into an inner thread vertex 21. The upper thread flanks 19 in FIG. 1 are the chip-facing thread flanks described later with reference to FIGS. 9 and 10, while the lower thread flanks 18 in FIG. 1 are the chip-averted thread flanks.

(19) The threaded blind hole bore 1 shown in FIG. 1 is carried out with the aid of a tapping tool 23 described hereinafter on the basis of FIGS. 2 to 4. Accordingly, the tool 23 in FIG. 2 has, on its drill tip 25, three uniformly circumferentially distributed, frontal main cutting edges 27 and a thread profile 29 trailing in the tapping direction I (FIG. 5 or 6).

(20) The tool 23 is constructed having a clamping shaft 24 and an adjoining tapping body 26, along the bore axis A of which a total of three circumferentially distributed flutes 28 extend up to the respective frontal main cutting edge 27 on the drill tip 25.

(21) At each main cutting edge 27, a rake face 31 delimiting the flute 28 and a frontal free face 33 of the drill bit 25 converge. In the circumferential direction of the tool, the respective flute 28 is delimited by a drill web 35. Overall, the tapping tool 23 shown in the figures has three drill webs 35. The rake face 31 of the flute 28 merges with the formation of a secondary cutting edge 36 into an outer circumferential rear face 37 of the respective drill web 35. The secondary cutting edge 36 and the frontal main cutting edge 27 converge at a radially outer main cutting edge 39.

(22) On the outer circumferential rear faces 37 of the three drill webs 35, the thread profile 29 has respectively a preliminary cutting tooth 41, a middle cutting tooth 42, and a finishing cutting tooth 43. Each of the cutting teeth 41, 42, 43 is formed having a radially outer thread base cutting edge 45 and thread flank cutting edges 47 in order to cut/form the thread turn 15 shown in FIG. 1. The cutting teeth 41 to 43 are embodied in different geometries and are spaced apart from the drill tip 25 at different axial distances Aa (only indicated in FIG. 5) in order to cut the thread turn 15 of the internal thread 9 shown in FIG. 1. In addition, the preliminary, middle, and finishing cutting teeth 41, 42, 43 can have different tooth heights Ari, Are, Ara (FIG. 2) in the radial direction. As an example, the preliminary, middle, and finishing cutting teeth 41, 42, 43 can become axially larger in the circumferential direction. The finishing cutting tooth 43 then cuts the entire internal thread contour. Alternatively to this, the finishing cutting tooth 43 can also be embodied as a forming tooth in order to increase the thread strength.

(23) The tapping tool 23 also has a cutting edge 49 at the transition between the tapping body 26 and the clamping shaft 24 for forming the thread countersink 7 shown in FIG. 1

(24) The method for producing the threaded blind hole bore 1 shown in FIG. 1 is described hereinafter with reference to FIGS. 5 to 8: Accordingly, in FIG. 5, the tapping tool 23 is guided in a tapping direction I to the not yet predrilled tool 5 and a one-shot bore is carried out. In a tapping stroke G, the main cutting edges 27 produce a core hole bore and the trailing thread profile 29 produces the internal thread 9 on the inner wall of the core hole bore. The tapping stroke G takes place at a tapping feed rate f.sub.G and at a tapping speed n.sub.G synchronized therewith in a tapping rotational direction, namely until the target thread depth t.sub.G is reached (FIG. 6).

(25) Immediately thereafter, a groove forming step (FIG. 7) is carried out in which the tapping stroke G in the tapping direction I is extended by a groove forming stroke N. In contrast to the thread-forming stroke G, in the groove-forming stroke H, the groove-forming feed rate f.sub.N and the groove-forming speed n.sub.N of the tapping tool 23 are not synchronized with one another, and are different from the previous tapping feed rate f.sub.G and the tapping speed n.sub.G.

(26) In this way, the thread profile 29 produces, using its preliminary, middle, and finishing cutting teeth 41, 42, 43, the circumferential groove 13 shown in FIG. 7, in which the thread profile 29 can rotate without load. The groove forming feed rate f.sub.N and the groove forming speed n.sub.N are designed in such a way that excessive cutting edge load of the cutting teeth 41 to 43 is prevented.

(27) When the target bore depth t.sub.B is reached, both the groove forming feed rate f.sub.N and the groove forming speed n.sub.N are reduced to 0. A rotational direction is then reversed in preparation for a reversing stroke R (FIG. 8). In the reversing stroke R (FIG. 8), the tapping tool 23 is led out of the threaded bore 1 in a reversing direction II (FIG. 8), specifically at an opposite reversing feed rate f.sub.R and a reversing speed n.sub.R synchronized with it. These parameters are dimensioned in such a way that the thread profile 29 of the tapping tool 23 is not led out of the threaded bore 1 without load, but under a chip-removing load in the thread turn 15 of the internal thread 9. In this way, as will be described later, a collision contour 53 (FIG. 9 or 10) that is still formed on the thread flanks 19 of the internal thread 9 is removed.

(28) At the start of the reversing stroke R, the tapping tool 23 is controlled by the production system in such a way that the cutting teeth 41, 42, 43 are each moved into the thread runout 11, which opens into the circumferential groove 13, under chip-removing load. In the further course of the reversing stroke R, the thread profile 29 of the tapping tool 23 is then rotated outwards through the thread turn 15 of the internal thread 9 under chip-removing load (that is, the collision contour 53 is removed).

(29) The tapping stroke G illustrated in FIG. 6 is shown in detail in FIG. 9. Accordingly, the tapping tool 23 is driven into the workpiece 5 in the tapping direction I at the predefined tapping feed rate f.sub.G and at the tapping speed n.sub.G synchronized therewith. In the process, chips 51 are produced, which are pressed out of the threaded bore 1 in a chip removal direction S opposite to the tapping direction I. The chips 51 conveyed in the chip removal direction S out of the threaded bore 1 collide with the chip-facing thread flanks 19 of the internal thread 5.

(30) According to the invention, in the tapping stroke I—with the exception of the chip-facing thread flanks 19 of the internal thread 9—the complete internal thread geometry is already produced at the finished dimension, specifically in detail the chip-averted thread flanks 18, the radially inner thread inner vertex 21, and the radially outer thread base 17. In contrast to this, after the tapping stroke I, the chip-facing thread flanks 19 of the internal thread 9 are not yet produced to a finished dimension, but rather are produced having an additional flank allowance Δx (FIG. 9). In this way, a collision contour 53 is provided on the chip-facing thread flanks 19, with which the chips 51 to be removed collide.

(31) The above collision contour 53 on the chip-facing thread flanks 19 is removed in the subsequent reversing stroke R down to the finished dimension. For this purpose, the tapping tool is positioned in the axial direction in the groove forming step in such a way that at the start of the reversing stroke R, the tapping tool 23 is controlled in such a way that the thread profile 29 is introduced the thread turn runout 11, which opens into the circumferential groove, under chip-removing load, i.e. with material removal (FIG. 1).

(32) By accordingly setting the reversing feed rate f.sub.R and the reversing speed r.sub.R synchronized with it, a reversing thread pitch α.sub.R for the chip-facing thread flanks 19 in the internal thread 9 results in the reversing stroke R. The reversing thread pitch α.sub.R of the chip-facing thread flank 19 can be identical to the tapping thread pitch α.sub.G or different therefrom in order to achieve a load-optimized internal thread design, if necessary.

(33) In this way, different flank diameters can be set for different alloys of the workpiece 5, wherein the respective flank diameter is specifically adapted in each case to the workpiece alloy used. In addition, it is also possible to regrind the thread teeth of the thread profile as part of a tool post-processing. In this case, the axial offset by which the tool is to be adjusted in the axial direction in the groove forming step at the beginning of the reversing stroke R in order to achieve a corresponding material engagement in the chip-facing thread flanks 19 would increase.

(34) The structure and the mode of operation of a tapping tool according to a further exemplary embodiment are described hereinafter with reference to FIGS. 11 to 15. The tapping tool shown in FIG. 11 basically corresponds to that of the preceding figures. Therefore, reference is made to the previous description. The tapping tool shown in FIG. 11 additionally has a reversing tooth 57, using which the flank allowance Δx is removed from the chip-facing thread flank 19 in an operationally-reliable manner in the reversing stroke R described later with reference to FIG. 15.

(35) FIGS. 12 to 14 relate to different side views of the tapping tool. In FIG. 12, the preliminary machining tooth 41, the finishing tooth 43, and the reversing tooth 57 are shown. In FIG. 13, the middle tooth 42 and the finishing tooth 43 are shown, while in FIG. 14, the finishing tooth 43, the reversing tooth 57, and the preliminary machining tooth 41 are shown.

(36) The reversing tooth 57 is shown in FIGS. 12, 14, and 15 designed having a thread flank cutting/forming edge 59. In the reversing stroke R, the tapping tool is controlled in such a way that its thread flank cutting/forming edge 59 removes or forms the flank allowance Δx from the chip-facing thread flanks 19 to the finished dimension.

(37) The reversing tooth 57, like the thread profile teeth 41, 42, 43, is formed on the drill web rear face 37. The reversing tooth 57 protrudes radially outward beyond the main cutting edge 39 by a reversing tooth height Δr.sub.R (FIG. 11). The thread flank cutting edge 59 of the reversing tooth 57 merges in FIG. 14 or 15 into a reversing cutting edge 61, which is also active in the reversing stroke H, at a radially inner cutting edge inside corner 60. Therefore, in the reversing stroke R, there is not only machining (for example, cutting machining) of the chip-facing thread flanks 19 of the bore internal thread 9, but rather simultaneously also deburring of the inner thread vertex 21 of the internal thread 9, as indicated in FIG. 15. With this deburring, burr formation on the inner thread vertex 21 is avoided, which would otherwise result during the machining of the chip-facing thread flanks 19.

(38) As can also be seen from FIGS. 12 to 15, the outer circumferential drill web rear face 37 and the rake face 31 of the flute 28 converge at the reversing cutting edge 61. The reversing cutting edge 61 and the secondary cutting edge 36 therefore both extend along the drill longitudinal direction and are formed on drill web longitudinal edges K1, K2 (FIG. 14) which lie opposite in the drill circumferential direction.

(39) In order to form a stable thread profile 29 on the tapping tool, a tooth web 63 adjoins each thread profile tooth 41, 42, 43 and the reversing tooth 57. This is formed in each case on the drill web rear face 37. The respective thread profile tooth 41, 42, 43 and the reversing tooth 57 is thus protected from premature tool breakage in the tapping stroke G and/or in the reversing stroke R. As can be seen from FIG. 14, the thread profile tooth 43 and the reversing tooth 57 are connected to one another via a tooth web 63 formed on the drill web rear face 37. The tooth web 63 has a radially outer web vertex surface 65 and a web flank surface 67 facing toward the drill tip 25 and a web flank surface 69 facing away from the drill tip 25. To reduce the tool load during the tapping stroke G and/or during the reversing stroke R, the above-mentioned web surfaces 65, 67, 69 can be formed at least partially as free surfaces, which are essentially inoperative in the tapping stroke G and/or in the reversing stroke R.

(40) According to FIGS. 12 to 14, the web vertex surface 65 of the tooth web 63 merges at a first circumferential web edge 71 into the web flank surface 67 facing toward the drill tip 25. Moreover, the web vertex surface 65 merges at a second circumferential web edge 72 into the web flank surface 69 facing away from the drill tip 25. With respect to a reduced tool load during the groove forming stroke N, the tapping tool has a circumferential groove cutting edge US (FIGS. 12 to 14) to produce the circumferential groove 13 in the groove forming stroke N. In the embodiment variant shown, the circumferential groove cutting edge US is implemented especially by means of second circumferential web edge 72.