Process arrangement and method for producing at least one workpiece threaded hole

Abstract

Process arrangement for producing at least one workpiece threaded hole (1), comprising a pre-drilling tool (17) which produces a workpiece pre-drilling hole (33) in a pre-drilling step, and comprising at least one thread-producing tool (19) which produces an internal thread (9) in the workpiece pre-drilling hole (33) in a thread-producing step, wherein the pre-drilling tool (17) can be used as a universal drill with which pre-drilling steps can produce pre-drilling holes (33) of different pre-drilling diameters and / or different drilling depths in the workpiece (5), and wherein, in the thread production step, the internal thread (9) can be produced in the pre-drilling hole (33) with a thread production tool (19) that is suitable for the produced pre-drilling hole (33), characterized by the fact that the pre-drilling tool (17) is a stepped pre-drilling tool and the thread-forming tool (19) has a face-facing reaming cutting edge (29) on its tool face, such that in the pre-drilling step the stepped pre-drilling tool (17) produces a stepped pre-drilling hole (33) with bore steps (B1, B2, B3) that are expanded in a step-like manner from the bore base (3) towards the bore opening edge, namely with a small-diameter, bottom-side bore step (B1) and at least one large-diameter bore step (B2, B3) following in the opposite direction to the drilling direction, in particular a bore step (B2) on the opening edge, and that in the thread-forming step the thread-forming tool (19) with its reaming cutting edge (29) reams the pre-drilling steps (B1, B2, B3) to a uniform diameter, in particular thread core diameter, and with its reaming cutting edge (29) the thread generation profile (31) lags in the direction of drilling to produce the internal thread (9).

Description

[0001] The invention relates to a process arrangement and a method for producing at least one workpiece threaded bore according to the preamble of claim 1 and claim 9, and a thread-producing tool according to the preamble of claim 8.

[0002] In a typical process, thread tapping, particularly with harder materials such as gray cast iron, is performed in two stages: a pre-drilling step followed by a thread-forming step. In the pre-drilling step, a pilot hole is created using a pilot drill. In the subsequent thread-forming step, an internal thread is created in the pre-drilled hole using a thread-forming tool.

[0003] When manufacturing a large number of workpiece threaded holes of varying thread sizes, current technology requires a separate pre-drilling tool and a separate thread-forming tool for each thread size. These tools must be inserted into or removed from the tool holder of a machine tool depending on whether the pre-drilling or thread-forming step is performed. Therefore, manufacturing such a large number of threaded holes of different sizes is associated with significant tooling costs and considerable time expenditure.

[0004] DE 10 2016 009 738 A1 discloses a generic method and a tool for producing an internal thread in a workpiece pilot hole. EP 3 458 219 B1 discloses a method for producing a threaded hole. This method is implemented as a single-shot thread-cutting process in which a single-shot thread-cutting tool performs both core drilling and internal thread cutting in a single tool stroke. Such a single-shot thread-cutting process is only feasible with a sufficiently soft material, such as aluminum. With a harder material, such as gray cast iron, tool breakage can occur, especially with excessively high feed rates. DE 10 2006 005 887 A1 discloses a method for producing a threaded hole with a countersink. DE 200 07 664 U1 discloses a milling thread cutter.

[0005] The object of the invention is to provide a process arrangement and a method in which the production of threaded bores of different thread sizes can be carried out with reduced tooling effort and time expenditure compared to the prior art.

[0006] The problem is solved by the features of claim 1, 8, or 9. Preferred embodiments of the invention are disclosed in the dependent claims.

[0007] The invention relates to a process arrangement for producing at least one workpiece threaded hole. The process arrangement comprises a pre-drilling tool and at least one thread-forming tool. In a pre-drilling step, the pre-drilling tool produces a workpiece pre-hole. In a subsequent thread-forming step, an internal thread is produced in the workpiece pre-hole using the thread-forming tool. According to the invention, the pre-drilling tool can be a stepped pre-drilling tool. Furthermore, the thread-forming tool has a finishing cutting edge on its end face. In the pre-drilling step, a stepped pre-hole with bore steps can be produced using the stepped pre-drilling tool.These steps widen from the bottom of the bore towards the bore opening edge, with a small-diameter step at the bottom and at least one larger-diameter step following the direction of drilling, particularly a step at the opening edge. In the subsequent thread-forming step, the thread-forming tool uses its reaming cutting edge to enlarge the pre-drilled steps to a uniform diameter, specifically a thread core diameter. Simultaneously, its thread-forming profile, which trails the reaming cutting edge in the drilling direction, creates the internal thread of the threaded bore.

[0008] The stepped pilot drill is used as a universal drill for creating pilot holes from which a group of tapped holes of different thread sizes can be produced. In this way, tapped holes of different thread sizes can be assigned to a single pilot drill. During the pilot drilling step, the same pilot drill can therefore prepare pilot holes for different thread sizes. This allows the pilot drilling step, which is performed during the production of a number of tapped holes of different thread sizes, to be carried out without time-consuming tool changes. In the subsequent threading step, the tapped hole can be produced using a suitable threading tool for each thread size.

[0009] In one technical implementation, the stepped drill bit can have cutting steps that widen in a stepped fashion from the tool face in the opposite direction of drilling. The stepped drill bit can have a small-diameter cutting step at its tool face, followed in the opposite direction of drilling by at least one larger-diameter cutting step. At least one, and in particular all, of the cutting steps can terminate with a countersinking edge towards the tool shank, by means of which a thread countersink can be produced at the opening edge of the workpiece threaded hole to be drilled.

[0010] In the pre-drilling step, the pre-drilling tool creates multiple pilot holes of varying depths in the workpiece. These can include, for example, a stepless pilot hole created solely by the small-diameter, face-mounted cutting edge of the pre-drilling tool. Alternatively, a single- or multi-stage pilot hole can be created using the small-diameter, face-mounted cutting edge and at least one additional cutting edge of the pre-drilling tool.

[0011] Specifically, in a process for producing multiple threaded holes of varying sizes in a workpiece, the process setup may include a set of thread-forming tools for different thread sizes. Before the thread-forming step is performed, a selection step is carried out in which a thread-forming tool is chosen from the set of tools. The selected thread-forming tool matches the diameter of the opening-edge-side bore step of a pre-drilled hole in the workpiece. The thread-forming step is then performed using the selected thread-forming tool.

[0012] In a preferred embodiment, the thread forming step is divided as follows: First, a threading stroke is performed, in which the thread forming tool is driven into the pilot hole with a thread forming feed and a thread forming rotational speed synchronized with it. Subsequently, a reversing stroke is performed, in which the thread forming tool is withdrawn from the threaded hole in a reversing direction with a reversing feed and a reversing rotational speed synchronized with it. In this way, the thread forming profile can preferably be withdrawn from the threaded hole in the thread of the internal thread without any load.

[0013] At the end of the threading stroke, the tool's direction of rotation is reversed so that the thread-forming tool can be withdrawn from the threaded hole during the subsequent reversing stroke. To prevent damage to the thread-forming tool during the change of direction, a circumferential relief cut can be performed. In this relief cut, the threading stroke in the drilling direction is extended by one relief cut stroke to create a circumferential relief cut adjacent to the internal thread, within which the thread-forming profile can rotate without load. This ensures that the change of the tool's direction of rotation can be carried out without damage.

[0014] Furthermore, the thread-forming tool can have a countersinking edge, which allows for the creation of a circumferential thread countersink in the opening edge of the threaded hole during the relief cut. The countersinking edge of the thread-forming tool and at least one countersinking edge of the pilot drill can have different cutting geometries. Accordingly, as required, either the countersinking edge of the pilot drill or the countersinking edge of the thread-forming tool can create the thread countersink in the threaded hole.

[0015] When producing threaded holes in a workpiece, there may be a requirement to machine the opening edge of the threaded hole, which may also serve a sealing function. To meet this requirement, the thread-forming tool can be part of a two-piece countersinking tool, in which the thread-forming tool is guided through a countersinking sleeve. The countersinking sleeve has at least one countersinking sleeve cutting edge on its end face facing the tool face. This cutting edge is set back from the tool face by an axial offset. The countersinking sleeve cutting edge is used to machine the opening edge of the threaded hole.

[0016] Exemplary embodiments of the invention are described below with reference to the accompanying figures.

[0017] They show: Fig. Figures 1 to 10 show different views, illustrating the structure and function of the process arrangement according to the invention.

[0018] In the Fig. Figure 1 shows a workpiece 5 with a total of three threaded holes 1, each with a different thread depth and thread size. The example shown in the Fig. The left-hand threaded bore 1 has an M6 thread 9, the middle threaded bore 1 an M7 thread 9, and the right-hand threaded bore 1 an M8 thread 9. Each internal thread 9 terminates with a thread runout into a circumferential relief 13. This relief does not widen the thread pitch and, viewed in the axial direction, is located between the internal thread 9 and a bore bottom 3.

[0019] Each of these threaded bores 1 is produced by means of a process arrangement which includes a common pre-drilling tool 17 ( Fig. 2) as well as a set 10 ( Fig. 3) of thread forming tools 19, namely an M6 thread forming tool 19, an M7 thread forming tool 19 and an M8 thread forming tool 19.

[0020] The common pre-drilling tool 17 ( Fig. 2) is designed as a stepped universal drill with a total of three cutting stages S1, S2, S3, the diameters of which are expanded in a stepped fashion from the tool face against the drilling direction, specifically with a small-diameter, face-side cutting stage S1, a medium-diameter cutting stage S2, and a large-diameter cutting stage S3. Each of the cutting stages S1, S2, S3 terminates in the direction of the tool shank 21 with a countersink 23, 25, 27. Using the respective countersink 23, 25, 27, the circumferential chamfer 7 (or alternatively according to Fig. 10 the circumferential sinking 8) can be produced.

[0021] Each of the three in the Fig. The thread forming tool 19 shown in Figure 3 has a transverse, face-mounted boring edge 29 on its tool face. The thread forming tool 19 also has a thread forming profile 31 that lags behind the boring edge 29 in one drilling direction.

[0022] The process for producing the in the Fig. The threaded holes shown in step 1 are in a pre-drilling step ( Fig. 4 and Fig. 5) and into a thread generation step ( Fig. subdivided into 6 to 8. In the pre-drilling step ( Fig. 4) The pre-drilling tool 33 initially generates the (in the) at a process time t1. Fig. 1 left) M6 threaded bore 1 a stepless pilot bore 33 in which only the small-diameter end-face cutting step S1 of the pilot drill 17 is driven into the workpiece 5, while the other two cutting steps S2, S3 of the pilot drill 33 remain out of engagement with the material. This results according to the Fig. 5 a stepless pre-drilling 33 with the chamfer 7, which is machined by means of the countersinking edge 23 ( Fig. 2) of the pre-drilling tool 19 is produced.

[0023] In the further course of the process, during the pre-drilling step at a process time t2 ( Fig. 4) with the common pre-drilling tool 17 for the (in the Fig. 1 medium) M7 threaded hole 1 creates a single-stage pre-drilling hole 33, in which not only the smaller diameter end-face cutting step S1, but also the larger diameter middle cutting step S2 is driven into the workpiece 5, while the largest diameter cutting step S3 of the pre-drilling tool 17 remains out of material engagement. This results in a single-stage pre-drilling hole 33 with a bottom-face, smaller diameter drilling step B1 and a drilling step B2 on the opening edge side, following the direction of drilling. The opening edge of the single-stage pre-drilling hole 33 is formed with the chamfer 7, which is formed by means of the countersinking cutting edge 25 ( Fig. 2) of the pre-drilling tool 19 is formed.

[0024] In the further course of the process, at process time t3 ( Fig. 4) for the (in the Fig. 1 right-hand) M8 threaded hole 1 creates a two-stage pre-drilling hole 33, in which the smaller diameter end-face cutting step S1, the medium cutting step S2, and the largest diameter cutting step S3 of the pre-drilling tool 19 are driven into the workpiece 5. This results in the two-stage pre-drilling hole 33 with the chamfer 7, which is countersunk by means of the countersinking edge 27 ( Fig. 2) of the pre-drilling tool 19 is formed.

[0025] Of the three different pilot holes 33, the M6 ​​pilot hole 33 for the M6 ​​threaded hole 1, for example, has a thread core diameter. Similarly, the M7 pilot hole 33 and the M8 pilot hole 33, with their opening-edge bore steps B2, each already have the thread core diameter.

[0026] Before the thread generation step is carried out, a selection step is performed in which a selection is made from set 10 ( Fig. 3) of thread forming tools 19 a thread forming tool 19 is selected which fits the diameter of the respective opening-edge side drilling step B1, B2 of the workpiece pre-bores 33 to be machined.

[0027] Thread production is carried out during the process in which Fig. 5 left M6 pilot holes 33 are drilled using an M6 threading tool 19. The process sequence for M6 threading is illustrated below using the following example. Fig. 6 to 8 are described. The M7 and M8 thread production processes are identical. Thus, the M6 ​​thread production tool 19 is first inserted into a thread stroke G ( Fig. 6) driven into the M6 ​​pilot hole 33 in the drilling direction, with a thread-forming feed and a thread-forming rotational speed synchronized to it. After completion of the thread stroke G, a clearance cut is made ( Fig. 7), in which the thread stroke G is extended in the drilling direction by a relief stroke N, to form the circumferential relief 13 adjoining the internal thread 9, in which the thread forming profile 31 can rotate without load. If necessary, during the relief cutting, the countersinking edge 35 of the thread forming tool can machine the circumferential chamfer 7 in the opening edge of the M6 ​​pilot hole 33, as shown in the Fig. 7 is shown.

[0028] After the cutting is complete, a reversing stroke R is performed ( Fig. 8), in which the thread forming tool 19 is led out of the threaded bore 1 in a reversing direction, with a reversing feed and a reversing rotation speed synchronized therewith.

[0029] Using the boring cutting edges 29 of the M7 thread-making tool 19 and the M8 thread-making tool 19, the bore stages B1 and B3 are bored to a uniform diameter. The boring process is carried out by chip removal of excess material 30, which is located in the Fig. The M7 pilot hole 33 in the middle and the M8 pilot hole on the right are highlighted by hatching. Simultaneously with the drilling process, the internal thread 9 is produced by the thread-forming profile 31, which lags behind the respective drilling cutting edge 29 in the drilling direction.

[0030] In the Fig.Figure 9 shows a thread-forming tool 19 according to a further embodiment. In this embodiment, the thread-forming tool is a component of a countersinking tool 37, in which the thread-forming tool 19 is guided through a countersinking sleeve 39. This sleeve has two countersinking cutting edges 41 on its end face facing the tool face, positioned opposite each other with respect to the axis of rotation R. These cutting edges are set back from the tool face of the thread-forming tool 19 by an axial distance a. The countersinking cutting edges 41 allow the opening edge region of the workpiece 5 to be machined to a specified dimension. REFERENCE MARK LIST: 1 threaded hole 3. Borehole bottom 5 workpieces 7th phase 8 Lowering 9 internal threads 10-piece set of thread-making tools 13 Free-cut groove 17 Pre-drilling tool 19 Thread forming tool 21 Tool shaft 23, 25, 27 Countersinking of the pre-drilling tool 17 29 Drilling cutter 30 surplus material 31 Thread generation profile 33 Pre-drilling 35 Countersinking cutting edge of the thread forming tool 37 Countersinking tool 39 Countersink sleeve 41 Countersink sleeve cutting edge S1, S2, S3 cutting stages B1, B2, B3 drilling stages a axial distance

Claims

[1] Process arrangement for producing at least one workpiece threaded hole (1), comprising a pre-drilling tool (17) which produces a workpiece pre-drilling hole (33) in a pre-drilling step, and comprising at least one thread-producing tool (19) which produces an internal thread (9) in the workpiece pre-drilling hole (33) in a thread-producing step, wherein the pre-drilling tool (17) can be used as a universal drill with which pre-drilling steps can produce pre-drilling holes (33) of different pre-drilling diameters and / or different drilling depths in the workpiece (5), and wherein, in the thread production step, the internal thread (9) can be produced in the pre-drilling hole (33) with a thread production tool (19) that is suitable for the produced pre-drilling hole (33), characterized by , that the pre-drilling tool (17) is a stepped pre-drilling tool and the thread-forming tool (19) has a face-facing reaming cutting edge (29) on its tool face, such that in the pre-drilling step the stepped pre-drilling tool (17) produces a stepped pre-drilling hole (33) with bore steps (B1, B2, B3) that are expanded in a step-like manner from the bore base (3) towards the bore opening edge, namely with a small-diameter, bottom-side bore step (B1) and at least one large-diameter bore step (B2, B3) following in the opposite direction to the drilling direction, in particular a bore step (B2) on the opening edge, and that in the thread-forming step the thread-forming tool (19) with its reaming cutting edge (29) reams the pre-drilling steps (B1, B2, B3) to a uniform diameter, in particular thread core diameter, and with its reaming cutting edge (29) the thread generation profile (31) lags in the direction of drilling to produce the internal thread (9). [2] Process arrangement according to claim 1, characterized by , that the stepped pre-drilling tool (17) has cutting steps (S1, S2, S3) which are expanded in a step-like manner from the tool tip in the opposite direction of drilling, namely with a small-diameter, face-side cutting step (S1) and at least one large-diameter cutting step (S2, S3) following in the opposite direction of drilling, and that in particular at least one of the cutting steps (S1, S2, S3) terminates in the direction of the tool shank (21) with a countersinking edge (23, 25, 27) by means of which a chamfer (7) or a thread countersink (8) can be produced at the opening edge of the workpiece threaded bore (1). [3] Process arrangement according to claim 1 or 2, characterized by , that In the pre-drilling step, the pre-drilling tool (17) creates a plurality of pre-drilled holes (33) of different drilling depths in the workpiece (5), namely - a stepless pre-drilling (33) which can be produced solely by means of the small-diameter, face-side cutting step (S1) of the pre-drilling tool (17), and - a single- or multi-stage pre-drilling (33) which can be produced by means of the small-diameter, face-side cutting step (S1) and at least one further cutting step (S2, S3) of the pre-drilling tool (17), and / or that the process arrangement includes a set (10) of thread forming tools (19) for different thread sizes (M6, M7, M8), and that prior to carrying out the thread forming step a selection step is performed in which a thread forming tool (19) is selected from the set (10) of thread forming tools (19) that matches the diameter and depth of the opening-edge side bore step (B2) of a workpiece pre-bore (33) to be machined, and that the thread forming step is carried out with the selected thread forming tool (19). [4] Process arrangement according to one of the preceding claims, characterized by , that The thread production step is divided into - a thread stroke (G) in which the thread forming tool (19) can be driven into the pilot bore (33) with a thread forming feed and a thread forming rotational speed synchronized therewith, and - a reversing stroke (R) in which the thread forming tool (19) is led out of the threaded bore (1) in a reversing direction (R), with a reversing feed and a reversing speed synchronized therewith, so that the thread forming profile (31) is preferably led out of the threaded bore (1) in the thread of the internal thread (9) without load, and that in particular A circumferential clearance cut is made between the thread stroke (G) and the reversing stroke (R), in which the thread stroke (G) is extended in the drilling direction by a clearance cut stroke (N) to form a circumferential clearance cut (13) adjoining the internal thread (9), in which the thread generation profile (31) can rotate without load. [5] Process arrangement according to claim 4, characterized by , that the thread forming tool (19) has a countersinking cutting edge (35) by means of which a circumferential thread countersink (8) or a chamfer (7) can be produced in the opening edge of the threaded bore (1). [6] Process arrangement according to claim 5, characterized by, that the countersinking cutting edge (35) of the thread forming tool (17) and the at least one countersinking cutting edge (35) of the pilot drilling tool (17) have different cutting geometries, so that, as required, either the countersinking cutting edge (23, 25, 27) of the pilot drilling tool (17) or the countersinking cutting edge (35) of the thread forming tool (19) produces the thread countersink (8) of the threaded bore (1). [7] Process arrangement according to one of the preceding claims, characterized by , that the thread forming tool (19) is a component of a countersinking tool (37) in which the thread forming tool (19) is guided through a countersinking sleeve (39) which has at least one countersinking sleeve cutting edge (41) on its end face facing the tool face, which is set back from the tool face by an axial offset (a), and that in particular an opening edge area or a slug of the workpiece (5) is machined to a nominal dimension by means of the countersinking sleeve cutting edge (41). [8] Thread forming tool (19) for a process arrangement according to one of the preceding claims, characterized by , that the thread forming tool (19) has a boring edge (29) on its particularly flat tool face, the cutting width of which is slightly larger than a diameter difference between the bore stages (B1, B2, B3) of the pilot bore (33), and / or that the thread forming tool (19) with its thread forming profile (31) which lags behind the boring cutting edge (29) in the drilling direction produces the internal thread (9), and that in particular the thread forming tool (19) is part of a countersinking tool (37) in which the thread forming tool (19) is guided through a countersinking sleeve (39) which has at least one countersinking sleeve cutting edge (41) on its end face facing the tool face, which is set back from the tool face by an axial offset (a), and that preferably an opening edge area or a slug of the workpiece (5) is machined to a nominal dimension by means of the countersinking sleeve cutting edge (41). [9] Method for producing at least one workpiece threaded hole (1), in particular in a process arrangement according to one of claims 1 to 7, comprising a pre-drilling tool (17) which produces a workpiece pre-drilling hole (33) in a pre-drilling step, and comprising at least one thread-producing tool (19) which produces an internal thread (9) in the workpiece pre-drilling hole (33) in a thread-producing step, wherein the pre-drilling tool (17) is used as a universal drill with which pre-drilling steps are performed to create pre-drilling holes (33) of different pre-drilling diameters and / or different drilling depths in the workpiece (5), and wherein, in the thread-making step, the internal thread (9) is produced in the pre-drilling hole (33) using a thread-making tool (19) that is suitable for the pre-drilling hole (33). characterized by , that the pre-drilling tool (17) is a stepped pre-drilling tool and the thread-forming tool (19) has a face-facing reaming cutting edge (29) on its tool face, such that in the pre-drilling step the stepped pre-drilling tool (17) produces a stepped pre-drilling hole (33) with bore steps (B1, B2, B3) that are expanded in a step-like manner from the bore bottom (3) towards the bore opening edge, namely with a small-diameter, bottom-side bore step (B1) and at least one large-diameter bore step (B2, B3) following in the opposite direction to the drilling direction, in particular a bore step (B2) on the opening edge, and that in the thread-forming step the thread-forming tool (19) with its reaming cutting edge (29) reams the pre-drilling steps (B1, B2, B3) to a uniform diameter, in particular thread core diameter, and with its reaming cutting edge (29) the thread generation profile (31) lags in the direction of drilling to produce the internal thread (9).

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