Method for machining threaded holes of workpieces

Abstract

The invention relates to a method for machining a threaded hole (1) of a workpiece by means of a thread drilling tool, the method having: a drilling stroke (B), in which a rotating thread drilling tool is advanced into the workpiece (5) in the drilling direction up to a nominal hole depth (t<subgt;B< / subgt;), specifically in the case of forming a threadless bottom hole (51); and a tapping stroke (G), in which the thread drilling tool machines an internal thread (9) in the bottom hole (51) with a tapping feed rate (v<subgt;f< / subgt>) and a tapping rotational speed (n) synchronized therewith. According to the invention, a reverse stroke (R1) is carried out after the drilling stroke (B), in which the thread drilling tool is withdrawn from the bottom hole (51) to such an extent in a reverse direction opposite to the drilling direction. Immediately thereafter, in an offset stroke (V1), the thread drilling tool is radially adjusted by a radial offset amount (Δr<subgt;1< / subgt>). Subsequently, in the tapping stroke (G), the radially adjusted rotating thread drilling tool is guided in a circumferential rotational movement along a circular path (53) around the hole axis (A).

Description

Technical Field

[0001] The invention relates to a method for machining a threaded hole in a workpiece and a threaded hole drilling tool. Background Art

[0002] In this type of method, when producing a threaded hole in a workpiece, a drilling stroke is first performed, during which a rotating threading tool is driven into the workpiece without a base in the drilling direction to the desired hole depth, specifically, forming a base without threads. Furthermore, this method performs a tapping stroke, during which the threading tool produces an internal thread in the base hole at a tapping feed rate and a synchronous tapping speed.

[0003] For example, this method can be implemented as a so-called tapping process, in which the predrilling (i.e., drilling the bottom hole) and the internal thread are produced in a common tool stroke. In this case, the drilling stroke and the tapping stroke overlap in time. This results in high tool loads and can shorten the tool's service life.

[0004] This tapping process is known from WO 2019 / 029850 A1. At the end of the tapping stroke, the direction of rotation of the rotating tool is reversed. The tool is then guided load-free out of the threaded hole during the reverse stroke, specifically at a reverse speed synchronized with the reverse feed rate. At this reverse speed, the threading teeth of the tapping tool move load-free in the inter-tooth grooves of the threaded hole in the workpiece. Summary of the Invention

[0005] The object of the present invention is to provide a method for machining a threaded hole in a workpiece and a threaded hole drilling tool, in which the tool load is reduced compared to the prior art and the threaded hole can be machined in a shorter process time.

[0006] Unlike the above-mentioned WO 2019 / 029850A1, according to the present invention, in the drilling stroke, not only the bottom hole but also the internal thread is no longer processed simultaneously, which brings high tool load. On the contrary, in the present invention, the threaded hole drilling tool is designed to only perform bottom hole processing in the drilling stroke. Subsequently, in the tapping stroke that is unrelated to this, the internal thread is processed. According to the features of the characterizing part of claim 1, in order to prepare for the tapping stroke, a reverse stroke is performed after the drilling stroke, in which the threaded hole drilling tool is completely guided out of the bottom hole in the reverse direction opposite to the drilling direction. In the offset stroke, the threaded hole drilling tool guided out of the bottom hole is adjusted radially outward by a radial offset. Subsequently, the radially adjusted threaded hole drilling tool is guided in a circular rotational motion along a circular trajectory around the hole axis, and then the tapping stroke begins.

[0007] It should be emphasized that, according to the present invention, internal thread machining is not performed during the reverse stroke. In this case, in order to prepare for internal thread machining, time is required to adjust the rotational speed of the thread drilling tool. During this rotational speed adjustment, the thread drilling tool must be adjusted from the drilling rotational speed (of the above-mentioned drilling stroke) to the tapping rotational speed (for subsequent internal thread machining). In addition, during this internal thread machining, the thread drilling tool is loaded with a pulling force, whereby the tool is subjected to less load.

[0008] According to the present invention, the tapping stroke and the drilling stroke can have the same stroke direction. During the drilling stroke, the tool axis around which the thread drilling tool rotates and the hole axis are coaxial with each other. In addition, during the drilling stroke, the drilling section of the thread drilling tool engages in cutting with the workpiece, while the thread machining section is guided together without load.

[0009] In a preferred implementation variant, as the rated thread depth is reached, the tapping stroke can be extended with a free cutting stroke. During the free cutting stroke, the feed rate and the rotational speed of the thread drilling tool are no longer synchronized with each other, whereby a circumferential relief groove adjacent to the internal thread is machined without a pitch. During the tapping stroke, the tool axis and the hole axis are parallel to each other axially, and more precisely, they have an axial distance corresponding to the radial offset. During the offset stroke, the thread drilling tool is adjusted radially by this radial offset.

[0010] After machining the circumferential relief groove during the free cutting stroke, a second offset stroke can be performed. During the second offset stroke, the thread drilling tool is radially displaced from the internal thread or the relief groove by the radial offset amount. Thereby, it is achieved that during the subsequent reverse stroke, the thread drilling tool can be guided out of the workpiece thread hole without load, that is, without thread engagement or cutting engagement.

[0011] To prepare for the tapping stroke, the rotational direction of the thread drilling tool can be reversed as needed. For example, the rotational direction can be reversed when performing the first reverse stroke.

[0012] If necessary, after performing the drilling stroke, the rotational speed of the thread drilling tool can be decelerated to zero and the first reverse stroke can be started.

[0013] The process steps for machining the thread hole are performed by means of a receiving part in which the tool can be mechanically adjusted. Before the tapping stroke, during the first reverse stroke, the rotational direction of the thread drilling tool is reversed, and this rotational direction reversal serves as a signal for adjusting the radial offset amount.

[0014] During the tapping stroke, by rotating around the outer diameter d of the thread in the xy plane ACenter synchronous internal feed and perform thread cutting by simultaneously synchronously moving along the hole axis (or tool axis) at a feed rate of one pitch per revolution. The time (n W ) for the thread drilling tool to make one revolution corresponds to the time (n G ) for the center to make one revolution around the outer diameter of the thread. The feed along the hole axis (thread feed) performed during this time corresponds to the pitch.

[0015] In the first offset stroke (i.e., between the first reverse stroke and the tapping stroke), the rotating thread drilling tool is adjusted by a radial offset and guided in a circumferential rotational movement along a circular path around the hole axis.

[0016] The thread drilling tool is designed such that, during the drilling stroke, the tool thread machining section (required for machining the internal thread) remains unloaded and disengaged from the bottom hole wall. Conversely, during the subsequent tapping stroke, the tool hole drilling section (required for machining the bottom hole) remains unloaded and disengaged from the machined internal thread. During the tapping stroke, the tool hole drilling section moves radially within the thread crest inside the radial interior of the internal thread using its drilling cutting part. The tapping stroke is performed with the tool axis parallel to the hole axis.

[0017] The thread drilling tool has at least one first drilling cutting part and a second drilling cutting part, which are spaced from each other by a wedge angle in the circumferential direction of the tool. The size of the wedge angle is designed such that the two drilling cutting parts are guided out of the workpiece thread hole unloaded and disengaged from the machined internal thread during the tapping stroke.

[0018] In one technical implementation, the thread machining section constructed on the thread drilling tool is arranged in the circumferential direction of the tool outside the angular region enclosed by the two drilling cutting parts.

[0019] The outer cutting profiles of the two drilling cutting parts move on the circular path of the drilling cutting parts when the tool rotates. In the same way, when the tool rotates, the profile of the tool thread machining section moves on a profile circular path with a profile diameter. To assist the thread drilling tool in retracting radially and during the second reverse stroke without profile interference, the profile diameter is designed to be smaller than the cutting profile diameter. In this way, a radial tool free space is obtained between the circular path of the drilling cutting parts and the profile circular path. During retraction, this tool free space is partially utilized radially.

[0020] The wedge angle enclosed between the first drilling cutting part and the second drilling cutting part can be designed, merely by way of example, to be less than 180° and, for example, in the range of 120°.

[0021] Each of the drilling cutting parts may have at least one laterally cutting edge constructed on the end side at the tool tip. The laterally cutting edge of each drilling cutting part may transition into the longitudinal cutting edge of the drilling cutting part at the radially outer cutting tip. Furthermore, in a specific implementation variant, the drilling cutting parts may be respectively constructed on a drill bridge portion extending in the tool longitudinal direction. The two drill bridge portions may be spaced apart from each other in the tool circumferential direction by a chip flute. The cutting surface defining the chip flue may transition (in the tool circumferential direction) into the circumferential drill bridge portion free surface at the longitudinal cutting edge. Radially outwardly directed guide edges may respectively project from each of the two circumferential drill bridge portion free surfaces. Furthermore, a tool thread machining section may be constructed on each of the two circumferential drill bridge portion free surfaces.

[0022] On the tool tip of the drill and thread tool, the cutting surface defining the chip flue may transition into the end side free surface at the laterally cutting edge on the end side, and the end side free surface tapers in the direction towards the tool axis. With regard to a uniform load on the drilling cutting parts, it is preferred that the first and second drilling cutting parts are arranged at different height positions in the tool axial direction, that is, there is an axial height offset between them. The axial height offset between the two drilling cutting parts (especially their laterally cutting edges with subordinate cutting tips) may be designed such that the load on the drilling cutting parts of each drilling cutting part is almost the same during the drilling stroke. When there is an axial height offset of the drilling cutting parts, an almost uniform load on the drilling cutting parts can be achieved, although the drilling cutting parts are not diagonally opposite with respect to the tool axis (as is the case in a conventional drill and thread tool), so that the tooth feed of each drilling cutting part is almost the same. In particular, the two laterally cutting edges on the end sides of the drilling cutting parts may be axially height offset from each other. Description of the Drawings

[0023] Next, embodiments of the present invention will be described with reference to the drawings.

[0024] Wherein:

[0025] Figure 1 A threaded blind hole - hole constructed in a workpiece is shown in a side sectional view;

[0026] Figure 2 And Figure 3 Different views of the drill and thread tool are shown;

[0027] Figure 4 To Figure 8 respectively show views illustrating the machining of the threaded blind hole - hole shown in Figure 1 during a process;

[0028] Figure 9 And 10 Conventional drilling tools are shown in different views;

[0029] Figures 11 to 14 shows an embodiment of the present invention; and

[0030] Figures 15 to 18 shows another embodiment of the present invention. Detailed Description

[0031] In Figure 1 the finished threaded blind hole - hole 1 is shown. The hole 1 with its hole bottom 3 is machined into the workpiece 5 by a process up to the rated hole depth t B , which will be explained later according to Figure 4 to 8. The threaded hole 1 has a circumferential thread recess 7 at its hole opening, which transitions downwards into the internal thread 9 in its further extension. The internal thread 9 extends along the hole axis A to the available rated thread depth t G . As can also be obtained from Figure 1 , the thread flutes of the internal thread 9 lead into an annularly surrounding free channel or relief groove 13. In Figure 1 , the thread core of the internal thread 9 is on the bottom hole diameter d K . The thread root of the internal thread 9 is on the thread outer diameter d A .

[0032] The threaded blind hole - hole 1 shown in Figure 2 and 3 is machined by means of a thread - drilling tool described later according to Figure 1 . Thus, in Figure 2 , the tool has a clamping shank 15, to which a thread - hole drill body 17 is connected. In Figure 3 , a first drilling cutting part S1 and a second drilling cutting part S2 are formed on the thread - hole drill body 17, and the drilling cutting parts are spaced from each other by a wedge angle α in the circumferential direction u of the tool. In Figure 3 , the thread - drilling tool has two hole - drill bridging parts 14 extending in the longitudinal direction of the tool. On each of the two hole - drill bridging parts 14, a drilling cutting part S1, S2 is respectively formed. The two hole - drill bridging parts 14 are spaced from each other by a chip - fluting groove 23 in the circumferential direction u of the tool ( Figure 3 ). Each of the drilling cutting parts S1, S2 has a longitudinal cutting edge 27 extending in the longitudinal direction of the tool (only indicated in Figure 12 and 14 ) and a transverse cutting edge 29 on the end side formed at the tip of the tool. The transverse cutting edge 29 on the end side transitions into the longitudinal cutting edge 27 at the radially outer cutting tip 33.

[0033] The cutting surface defining the chip - fluting groove 23 transitions into the circumferential hole - drill bridging part free surface 35 at the longitudinal cutting edge 27 ( Figure 3) In the middle. At the free surface 35 of the hole drilling bridging part on the circumferential side, laterally protruding guiding edges 37 are respectively constructed. In addition, a tool thread machining section 39 is constructed at the wide hole drilling bridging part 14 (specifically at its free surface 35 of the hole drilling bridging part). In Figure 3 , the tool thread machining section consists of a total of three machining teeth, namely, a pre-machining tooth 40, an intermediate tooth 41, and a finishing tooth 42. Alternatively or additionally, other teeth (such as the tooth 43 shown in Figure 1 ) can also be provided. In Figure 3 , the teeth 40 to 42 are successively arranged on the tool circumference u and are arranged, for example, at the same height axially. However, alternatively, the tool thread machining section 39 is not limited to this specific implementation variant. On the contrary, fewer or more cutting teeth can also be provided and / or the cutting teeth can also be arranged axially offset from each other on the free surface 35 of the hole drilling bridging part.

[0034] In addition, when viewed axially, the thread machining section 39 has circumferential cylindrically extending support bridging parts 44 ([[]] Figure 3 and Figure 4 ) on both sides of the machining teeth 40, 41, 42. When machining the thread (see Figure 7 ), the outer diameter of the support bridging part is approximately the bottom hole diameter d VB , so that the support bridging part (44) of the drill thread hole tool abuts against the bottom hole wall when machining the thread.

[0035] As can also be obtained from Figure 3 , the outer cutting profiles of the first and second drilling cutting parts S1, S2 move on a circular trajectory 45 of the drilling cutting part with a cutting profile diameter (equal to the bottom hole diameter d K ) when the tool rotates. In the same way, the tooth profile of the tool thread machining section 39 moves on a circular trajectory or envelope 47 of the tooth profile with a tooth profile diameter ( Figure 3 and 4 ) when the tool rotates. In Figure 3 or 4, the tooth profile diameter is designed to be smaller than the cutting profile diameter (the same as the bottom hole diameter d K ). Thus, a radial tool free space 49 ( Figure 3 or 4) is obtained between the circular trajectory 45 of the drilling cutting part and the circular trajectory 47 of the tooth profile. This tool free space 49 is required in the retraction step F ( Figure 8b ) described later.

[0036] Next, the machining of the thread by means of the drill thread hole tool according to the present invention will be described with reference to Figure 4 to FIG. 8: Therefore, in the drilling stroke B ( Figure 4 and 5)In the case of forming the bottom hole 51, the rotating thread drilling tool is advanced into the workpiece 5 without a bottom hole until the rated hole depth t B . During the drilling stroke B, the two drilling cutting parts S1, S2 are in cutting engagement with the workpiece 5, while the tool threading section 39 remains unloaded and disengaged from the bottom hole wall. The tool axis W is oriented coaxially with the hole axis A, and the feed rate v of the thread drilling tool can be freely selected f and the rotational speed n. In Figure 4 , the drilling process is carried out, for example, in the left-handed direction in the drawn rotation direction 38

[0037] After the drilling stroke ( Figure 5 ), the tapping stroke G ( Figure 8a ) is prepared by the following process steps: That is, after the drilling stroke B, first a reverse stroke R1 ( Figure 6 ) is carried out. In the reverse stroke, the thread drilling tool is withdrawn from the bottom hole 51 to such an extent in the reverse direction opposite to the drilling direction that a first offset stroke V1 ( Figure 7 ) can be carried out. In the first offset stroke V1, the thread drilling tool withdrawn from the bottom hole 51 is radially adjusted by a radial offset amount Δr1

[0038] Subsequently, the tapping stroke ( Figure 8a ) is started. In the tapping stroke, the radially adjusted rotating thread drilling tool is guided along a circular path 53 around the hole axis A to perform a circular motion ( Figure 7 ), and the thread drilling tool is introduced into the bottom hole 51 with a tapping feed rate and a tapping rotational speed synchronized therewith. In the tapping stroke G, tool rotation and tool circular motion are carried out not only in the same co-rotating direction but also at the same rotational speed, as shown, for example, in Figure 7

[0039] In the tapping stroke G ( Figure 8a ), the threading section 39 of the thread drilling tool machines the internal thread 9 until the rated thread depth t G . As the rated thread depth t G is reached, the tapping stroke G is extended into the free cutting stroke F ( Figure 8a ). In the free cutting stroke F, the feed rate v f and the rotational speed n of the thread drilling tool are no longer synchronized with each other. Therefore, the surrounding relief groove 13 following the internal thread 9 is machined without a pitch

[0040] After machining the surrounding relief groove 13, a second offset stroke V2 ( Figure 8b ) is carried out. In the second offset stroke, the thread drilling tool is radially displaced from the relief groove 13 by a radial offset amount Δr2. This enables a second reverse stroke R2​Figure 8b ) In the second reverse stroke, the tool for drilling a threaded hole can be guided out of the workpiece threaded hole 1 without load, that is, without thread engagement and without cutting engagement.

[0041] The following description particularly relates to the drilling process steps and the drilling section of the tool for drilling a threaded hole: Generally, when designing the drilling process steps, the process parameters (that is, the rotational speed n of the drilling tool and the feed rate v f ) are coordinated with the positions of the drilling cutting parts S1, S2 on the drilling tool so that the drilling cutting part loads of each drilling cutting part S1, S2 are almost the same, that is, ideally the feed rate v of each drilling cutting part S1, S2 fz (tooth feed rate) is the same. In traditional tools for drilling threaded holes ( Figure 9 and 10 ), this is achieved by a constant pitch between the drilling cutting parts S1, S2. Therefore, in Figure 9 , the drilling cutting parts S1, S2 are diagonally opposite to each other with respect to the tool axis W, so that the feed rate (tooth feed rate) of each drilling cutting part S1, S2 is almost the same, which is obtained from Figure 10 . In Figure 10 , the peripheral surface of a traditional drilling tool is shown in an improved version. Accordingly, the drilling cutting parts S1, S2 are positioned at the same axial height H. In Figure 10 , the drilling cutting parts S1, S2 are in cutting engagement with the inner wall of the workpiece hole through the same cutting width s respectively. In Figure 10 , the cutting strokes w1 and w2 of the two drilling cutting parts S1, S2 obtained during the drilling process are shown. The cutting strokes w1 and w2 extend helically along the inner wall of the hole at a lift angle β, so that in this improved version ( Figure 10 ), a linear extension of the cutting strokes w1 and w2 is obtained. In Figure 10 , the cutting strokes w1 and w2 do not overlap, but instead transition into each other axially without overlap.

[0042] In Figures 11 to 14 's embodiment, (differently from the prior art according to Figure 9 and Figure 10 ) the pitch between the two drilling cutting parts S1, S2 is no longer the same, but different. Accordingly, in Figure 12 , for each drilling cutting part, the feed rate f of each drilling cut fz is no longer the same, but different. That is, in Figure 12 , the drilling cutting parts S1, S2 are no longer uniformly but differently loaded during the drilling process. According to Figure 12 , the maximum feed rate v of each drilling cut is assigned to the first drilling cutting part S1fz , that is to say, the first drilling cutting part S1 is exposed to a relatively large cutting load. In Figure 12 , the two drilling cutting parts S1, S2 are positioned at the same height H without an axial height offset ΔH. According to Figure 13 and 14 , each transverse cutting edge 29 of each drilling cutting part S1, S2 encloses an acute angle β1, β2 with the tool axis W. In Figure (as in a conventional drilling tool with a symmetric distribution of drilling cutting parts), the acute angles β1, β2 of the two drilling cutting parts S1, S2 are designed to be the same. At this time, the acute angles β1, β2 are selected such that on the circumferential side of the tool, that is to say, an axial height offset ΔH is obtained at the cutting tips 33 of the two drilling cutting parts S1, S2, that is to say, different height positions H1, H2 of the drilling cutting parts S1, S2, as shown in ​ .

[0043] Although the distance intervals are different, in order to ensure an approximately uniform load on the drilling cutting parts S1, S2, in the embodiment according to ​ , the drilling cutting parts S1, S2 are no longer positioned at the same axial heights H1, H2, but instead are arranged at different height positions H1 and H2. The height positions H1 and H2 are selected such that compared with ​ and 12 , a more uniform load on the drilling cutting parts of the two drilling cutting parts S1, S2 is obtained. The height positions H1 and H2 are selected according to the process parameters during the drilling process (that is to say, the tool rotation speed, the tool feed rate) and according to the corresponding step distance.

[0044] As can be obtained from ​ , the drilling cutting parts S1, S2 (similarly to ​ and 10 ) are respectively in cutting engagement with the inner wall of the hole through the same cutting width s. In addition, in ​ , the cutting strokes w1 and w2 do not overlap with each other, but instead transition into each other without overlap.

[0045] According to ​ and ​ , each transverse cutting edge 29 of each drilling cutting part S1, S2 encloses an acute angle β1, β2 with the tool axis W. In ​In this case, the acute angles β1, β2 of the two drilling cutting parts S1, S2 (as in a conventional drilling tool with a symmetric distribution of drilling cutting parts) are designed not to be the same, but rather to be different from each other. At this time, the acute angles β1, β2 are selected such that an axial height displacement ΔH is obtained on the peripheral side of the tool, that is, at the cutting edges 33 of the two drilling cutting parts S1, S2, that is, different height positions H1, H2 of the drilling cutting parts S1, S2, as shown in ​ as shown therein.

[0046] List of Reference Signs

[0047] 1 threaded hole

[0048] 3 hole bottom

[0049] 5 workpiece

[0050] 7 thread undercut

[0051] 8 flank / land

[0052] 9 internal thread

[0053] 13 circumferential relief groove

[0054] 14 hole drill bridging part

[0055] 15 clamping handle

[0056] 17 tool body

[0057] 14, 16 hole drill bridging part

[0058] S1, S2 drilling cutting part

[0059] 23 chip flute

[0060] 25 longitudinal cutting edge

[0061] 29 transverse cutting edge

[0062] 30 end-side free surface

[0063] 33 cutting edge

[0064] 35 hole drill bridging part free surface

[0065] 37 guiding edge

[0066] 38 rotational direction during drilling stroke

[0067] 39 tool thread machining section

[0068] 40, 41, 42 cutting teeth of thread machining section

[0069] 43 alternative cutting teeth

[0070] 44 Basic support

[0071] 45 Circular trajectory of the drilling cutting part

[0072] 47 Envelope of the thread machining section 39

[0073] 49 Tool free space

[0074] 51 Pilot hole

[0075] [[ID="15"]]53 Circumferential circular trajectory

[0076] t B Rated hole depth

[0077] d K Bottom diameter

[0078] u Tool circumferential

[0079] α Wedge angle

[0080] A Hole axis

[0081] W Tool axis

[0082] B Drilling stroke

[0083] G Tapping stroke

[0084] F Free cutting stroke

[0085] V1, V2 Offset stroke

[0086] Δr1, Δr2 Radial offset

[0087] ΔH Height misalignment

[0088] H1, H2 Height position

[0089] β1, β2 Acute angle

[0090] v f Feed rate

[0091] t G Rated thread depth

Claims

1. A method for machining a threaded hole (1) of a workpiece by means of a tool for drilling threaded holes, the method comprising: Drilling stroke (B), in which, when forming a threadless bottom hole (51), the rotating thread-drilling tool is advanced into the workpiece (5) in the drilling direction up to the rated hole depth (t B ); tapping stroke (G), in which the thread-drilling tool machines an internal thread (9) in the bottom hole (51) with a tapping feed rate (v f ) and a tapping rotational speed (n) synchronized therewith, wherein, to prepare for the tapping stroke (G), a reverse stroke (R1) is carried out after the drilling stroke (B), in which the thread-drilling tool is withdrawn from the bottom hole (51) to such an extent in the reverse direction opposite to the drilling direction, wherein, in an offset stroke (V1), the thread-drilling tool is radially adjusted by a radial offset amount (Δr1), and in the tapping stroke (G), the radially adjusted rotating thread-drilling tool is guided in a circumferential rotational movement along a circular trajectory (53) around the hole axis (A), characterized in that, in the tapping stroke (G), the tool rotation and the tool circumferential movement are carried out in a co-directional rotational movement and at the same rotational speed.

2. The method according to claim 1, wherein The tapping stroke (G) and the drilling stroke (B) have the same stroke direction, and / or during the tapping stroke (G), the threading section (39) of the tool for drilling the threaded hole machines the internal thread (9) up to the nominal thread depth (t G ), and as the nominal thread depth (t G ) is reached, the tapping stroke (G) is extended by a free-cutting stroke (F) during which the feed rate (v f ) and the rotational speed (n) of the tool for drilling the threaded hole are no longer synchronized with each other, and the circumferential relief groove (13) following the internal thread (9) is machined without a pitch.

3. The method according to claim 2, wherein After completion of the free cutting stroke (F), a second offset stroke (V2) is carried out in order to prepare the reverse stroke (R2), in which the thread drilling tool is radially displaced by a radial offset (Δr2) out of the internal thread (9) or the relief groove (13) so that in the reverse stroke (R2), the thread drilling tool can be guided out of the workpiece thread hole (1) without load, that is to say without thread engagement or cutting engagement.

4. The method according to any one of the above claims, characterized in that, In the drilling stroke (B), the drilling sections (S1, S2) of the thread drilling tool are in cutting engagement with the workpiece (5) and the thread machining section (39) is guided along without load, and / or in the tapping stroke (G), the thread machining section (39) is in engagement with the shape of the inner wall of the pilot hole and / or in cutting engagement and the drilling sections (S1, S2) are guided along without load.

5. The method according to any one of claims 1 to 3, characterized in that In the drilling stroke (B), the drill tool axis (W) and the hole axis (A) are coaxial with each other, and / or in the tapping stroke (G), the tool axis (W) and the hole axis (A) are parallel to each other axially and have an axial distance corresponding to the radial offset (Δr1).

6. The method according to claim 1, characterized in that The drilling sections (S1, S2) of the thread drilling tool have at least a first drilling cutting part (S1) and a second drilling cutting part (S2), the first and the second drilling cutting parts being spaced from each other by a wedge angle (α) in the circumferential direction (u) of the tool, the size of the wedge angle (α) being designed such that the two drilling cutting parts (S1, S2) can be introduced into the workpiece thread hole (1) without load and disengaged from the machined internal thread (9) during the tapping stroke (G).

7. The method according to claim 6, wherein The tool thread machining section (39) is arranged in the circumferential direction (u) of the tool outside the rotational angle region (α) enclosed by the two drilling cutting parts (S1, S2).

8. The method according to claim 6 or 7, characterized in that The first and second drilling cutting parts (S1, S2) move on a common circular path (45) of the drilling cutting part diameter (d K ) during tool rotation. During the drilling stroke (B), the tool threading section (39) moves on an outer diameter smaller than the bottom hole diameter (d VB ).

9. The method according to claim 2, characterized in that The tool thread machining section (39) has at least one or more thread machining teeth (40, 41, 42), and / or each machining tooth (40, 41, 42) is located on its own profile diameter, where the difference in profile diameter represents the allowance between two successive thread machining teeth, and / or the last machining tooth (42) in the direction of rotation (38) is a finishing tooth, the profile diameter of which is greater than the profile diameters of the previous machining teeth (41, 42), and / or the thread machining teeth (40, 41, 42) are located on the envelope (Figure 4; 47).

10. The method according to claim 9, characterized in that, The cutting geometry of the machining teeth (40, 41, 42) is designed and machined such that the machining teeth (40, 41, 42) are embedded in the material of the bottom hole wall when machining the thread. Thus, the thread drilling tool is loaded with a lateral deflection force, and in order to balance the deflection force, the tool thread machining section (39) has at least one circumferentially arranged base support (44), and the outer diameter of the base support is approximately located at the bottom hole diameter (d VB ) during thread machining, so that the base support (44) of the thread drilling tool abuts against the bottom hole wall during thread machining.

11. The method according to claim 10, wherein Viewed axially, at least one basic support (44) is constructed on each side of the machining teeth (40, 41, 42).

12. The method according to claim 6, wherein The first and second drilling cutting parts (S1, S2) are arranged at different height positions (H1, H2) in the axial direction of the tool, that is to say they have an axial height offset (ΔH) with respect to each other, and the size of the axial height offset (ΔH) between the drilling cutting parts (S1, S2) is designed such that the drilling cutting part loads of each drilling cutting part (S1, S2) are substantially the same during the drilling stroke (B).

13. The method according to claim 6, characterized in that, Each drilling cutting part (S1, S2) has at least one axially lateral cutting edge (29) configured on the tool tip, and the lateral cutting edges (29) of the two drilling cutting parts (S1, S2) are axially offset from each other by a height offset (ΔH).

14. The method according to claim 13, characterized in that, The lateral cutting edge (29) of each drilling cutting part (S1, S2) transitions into a longitudinal cutting edge (FIG. 14: 27) at a radially outer cutting tip (33), and / or the drilling cutting parts (S1, S2) are respectively configured on a hole drilling bridging part (14) extending in the tool longitudinal direction, and the hole drilling bridging parts (14) are spaced apart from each other in the tool circumferential direction (u) by chip flutes (23), and / or the cutting surface defining the chip flute (23) transitions into a circumferential hole drilling bridging part free surface (35) at the longitudinal cutting edge (27), and / or the guiding edges (37) respectively project from the circumferential hole drilling bridging part free surface (35), and / or a tool thread machining section (39) is configured on the circumferential hole drilling bridging part free surface (35).

15. The method according to claim 14, characterized in that The lateral cutting edge (29) of each drilling cutting part (S1, S2) encloses an acute angle (β1, β2) with the tool axis (W), and the acute angles (β1, β2) of the drilling cutting parts (S1, S2) are the same, or the acute angles (β1, β2) of the drilling cutting parts (S1, S2) are different, whereby an axial height offset (ΔH) is obtained on the tool circumference.

16. The method according to claim 15, wherein On the tool tip, the cutting surface defining the chip flute (23) transitions into an end-side free surface (30) at the axially lateral cutting edge (29), and the end-side free surface tapers in the direction towards the tool axis (W).

17. The method according to any one of claims 1 to 3, characterized in that, The process steps for machining a threaded hole are carried out by means of a CNC control device.

18. The method according to any one of claims 1 to 3, characterized in that, The process steps for machining a threaded hole are carried out by means of a receiving part in which the tool can be mechanically adjusted. Before the tapping stroke (G), during a first reverse stroke (R1), the rotational direction of the drill for the threaded hole is reversed, and the rotational direction reversal serves as a signal for adjusting the radial offset (Δr1).

19. A tool for drilling threaded holes (1) in a workpiece, comprising: Drilling stroke (B), in which, when forming a bottom hole (51) without threads, the rotating tool for drilling a threaded hole is advanced into the workpiece (5) in the drilling direction up to the rated hole depth (t B ); tapping stroke (G), in which the tool for drilling a threaded hole machines an internal thread (9) in the bottom hole (51) with a tapping feed rate (v f ) and a tapping rotational speed (n) synchronized therewith, wherein, to prepare for the tapping stroke (G), a reverse stroke (R1) is carried out after the drilling stroke (B), in which the tool for drilling a threaded hole is withdrawn from the bottom hole (51) to such an extent in the reverse direction opposite to the drilling direction, wherein, in an offset stroke (V1), the tool for drilling a threaded hole is adjusted radially by a radial offset amount (Δr1), and in the tapping stroke (G), the radially adjusted rotating tool for drilling a threaded hole is guided in a circumferential rotational motion along a circular path (53) around the hole axis (A), characterized in that, in the tapping stroke (G), the tool rotation and the tool circumferential motion are carried out with a co-directional rotational motion and at the same rotational speed; and in the drilling stroke (B), the drilling sections (S1, S2) of the tool for drilling a threaded hole are in cutting engagement with the workpiece (5), and the thread machining section (39) is guided together without load, and in the tapping stroke (G), the thread machining section (39) is in shape and / or cutting engagement with the inner wall of the bottom hole, and the drilling sections (S1, S2) are guided together without load.

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