Deep drilling tool 2-edged

Abstract

Deep drilling tool with 2 cutting edges, consisting of: a drill head (10) made of hard metal or ceramic, with a roof-shaped (10 a) or conical (10 b) end geometry, with two main cutting edges (10 c) offset from one another by 180° on the front, with at least two inner channels (10 d) for the coolant supply to these and two free spaces (10 e) for the removal of the chips, a round drill pipe with a conical opening (12) and an intermediate carrier (11) which directs the coolant, which primarily flows back from the two free spaces (10 e) on the drill head (10) and is mixed with chips, through two channels (11 b) into the interior of the pipe (12), and divides the coolant flow supplied on the outside of the drill pipe (12) into direct supply to the cutting area via outer channels (10 f), and indirect supply to the inner channels (10 d), all connected by means of gluing, soldering or welding.

Description

Technical area:

[0001] Deep hole drilling tools are primarily used in task-specific machine tools for drilling holes whose drilling depth is usually much greater than the hole diameter. They are generally designed so that a continuous coolant flow ensures uninterrupted removal of the drilling chips, thus eliminating the need for repeated chip preparation or removal. Deep hole drilling tools are used primarily in metallic applications, but occasionally also in non-metallic applications. Relevant state of the art:

[0002] Deep hole drilling tools have been around for a long time and are primarily named after the drilling processes for which they were designed. A distinction is made between the ELB process for holes in the smaller diameter range, the BTA process for more powerful drilling and reaming operations, and the ejector process for special chip removal.

[0003] The advantages of the ELB drill are its simple design, good guidance properties, and the easily and frequently resharpenable head geometry. The disadvantage is that the long drill shank is asymmetrical due to the chips flowing outwards, making it less torsionally rigid.

[0004] The BTA process, thanks to the use of round drill pipes, provides optimal torsional rigidity. However, the drill head design is more complex, and disadvantages may also include the increased machine complexity required for this process.

[0005] The ejector application requires lower coolant pressures, but due to the double-pipe technology, it leads to difficulties in geometric implementation as the bore diameter decreases.

[0006] The 2-flute version, also known as a "double-flute drill," plays a special role in the field of so-called ELB drilling technology, although the ELB would then more correctly be referred to as ZLB drilling technology. Here, too, the coolant is supplied through the interior of the drill pipe, and chip evacuation and coolant return take place on the outer surface of the drill pipe. However, since two cutting areas now have to be "served," and the drill pipe is deformed twice for this purpose, this drilling tool is actually a blatant contradiction in terms. On the one hand, one expects approximately twice the cutting performance, which results in a much greater torsional load on the drill pipe - and on the other hand, one weakens precisely this pipe cross-section by further constricting it.A further disadvantage is that each of the two chip spaces has a smaller cross-section than that of the classic ELB drill, which is why this type of drill is more likely to be found in the field of shorter-chipping materials. Publications considered:

[0007] DE 102009031193 A1: It merely mentions that the cutting geometry features primarily applicable to single-flute drills could also be applied to double-fluted tools. Only a schematic illustration is shown in Fig. 2.

[0008] DE 102010051248 A1: Concerns only chipbreaker grooves on the main cutting plane of a single-lip drill, whereby an improvement in chip breakage is promised by introducing similar grooves on the opposite surface of the chip space. It is mentioned that this also applies equally to the two chip spaces of a double-lip drill. A corresponding illustration is missing.

[0009] DE 102012215420 A1: Here, a marking line on the main cutting plane is presented as relevant to the invention. This line is intended to help reliably maintain the tip geometry when resharpening the partial cutting edges, which would of course also be applicable to the double-edged tool. However, a specific illustration of the double-fluted drill is also missing.

[0010] DE 60 2005 005 578 T2: This publication does not deal with the area of single-lip / double-lip drilling technology, but rather (in two variants) a combination tool for drilling machines on which no guide bushing can be fitted to accommodate the drill head for the pilot drilling in front of the drilling point. The guiding function is to be taken over by a short, centrally mounted pilot drill (20) modeled on a twist drill, which is intended to protect the drill head from otherwise unavoidable lateral vibration when the main cutting plane enters. This is really only an emergency solution, with correspondingly modest pilot drilling accuracy and surface quality of the hole - actually only suitable for use with materials that are otherwise easy to machine. The suitability for difficult-to-machine materials, such as, for example,Titanium is questionable, as deep hole drills for such applications are designed differently based on the current state of the art for a reason. The two cooling holes (24) in the pilot drill are probably only modeled on twist drills, or more precisely, helical drills with internal cooling channels, which were already state of the art. In this case, they are useless because the pressure around the pilot drill prevents any coolant from flowing effectively. The cited "roof-shaped end geometry" probably refers to the shape of the drill tip, and in the field of single-lip drilling / double-lip drilling, end geometry basically refers to the rear end of a drill head; the tip is always referred to as the tip or cutting geometry.

[0011] DE 20 2005 016 055 U1: This document deals solely (and only in the area of "single-lip drills") with the mechanical interchangeability of the drill head, which is possible through appropriate design, and with very general features in the claims, e.g., with regard to shape or material. An example is claim 8, which should never have been accepted in such a general way, since in drilling technology, almost all drills have always had a steel drill shaft.

[0012] What all the cited publications have in common is that none of them goes into detail about the actual strengths and weaknesses of a two-lip drill. Task:

[0013] The invention is therefore based on the object of creating a drilling tool for the "double-lip drill" sector that combines the essential advantages of the three most common types of deep drilling tools (as referred to in the "state of the art") in a single tool, with the optimal torsion-resistant round drill pipe from BTA drilling technology being particularly advantageous in accordance with the higher cutting performance. However, the connection options between the front structure of the tool and the drill pipe are essentially identical to those of the "single-lip drill" sector, as already mentioned and illustrated in connection with DE 102017006188 A1, and are therefore not part of this patent application. Disclosure of the invention:

[0014] This object is achieved by the features of the independent claims, according to which a deep drilling tool is provided which consists of a double-edged drill head (10), an intermediate support (11) oriented thereon, and a drill pipe (12). Further advantageous embodiments are set out in the dependent claims and explained in the description. Character list: Fig. Figure 1 shows the basic design of a double-edged deep hole drilling tool with a homogeneous drill head (10), also known from the ZLB process, and preferably made of hard metal or ceramic, an intermediate support (11), and the drill pipe (12), both usually made of steel. The type and number of coolant passages in the drill head can vary, but two holes (10d) are commonly used. The drill head is roof-shaped (10a) or conical (10b) at the rear end, the latter being easier to pre-center when connecting to the intermediate support (gluing / soldering / welding). The connection between the intermediate support (11) and the drill pipe (12) (gluing / soldering / welding) is conical, with the cone length being selected so that, depending on the connecting material used, no weak points arise and the torsional rigidity at the connection is not inferior to that of the drill pipe itself.In addition to the internal coolant passage (10d), each cutting side also has an external channel (10f), which continues in the same position in the intermediate support (11) to its end (11c). The depth of the channel is determined by the outer diameter of the drill pipe (12). The two chip spaces (10e) are maintained through two recesses (11b) of at least the same cross-section all the way to the inner pipe. The diagram shows that the drill head (10) and intermediate support (11) can form a common part (13), hereinafter referred to as the base body. Fig. Figure 2 illustrates the inventive function of the intermediate support (11) in that, in addition to the BTA-typical coolant supply via the outer channels (10 f), further partial flows are distributed equally into the two cutting areas via recesses (20), recesses (21), and inner channels (22 / 10 d), and additionally, to enhance backwash, via channel extensions (23) to the interior of the pipe. This backflow amplifies (and accelerates) the coolant flowing back from the machining area together with the drilling chips, thus reducing the risk of chip jams at the transition from the intermediate support (11) to the drill pipe (12). Fig. Figure 3 shows the bore bottom (30) created jointly by the two cutting areas, the two main cutting edges (33 and 34), a partially recessed outer cutting edge (31), an opposite, uncut outer cutting edge with a so-called chamfer (32), and the center cutting edge (35) located inside. The taper of the drill head, typical for such deep hole drilling tools, means that the chamfer (32), which is located further forward in the drilling direction, makes this cutting side the diameter-determining side. If the center cutting edge (35) is widened so far in the direction of the adjacent main cutting edge (34) that the radially acting component of all cutting forces, in total, results in a preponderance towards the diameter-determining side, the values of a pure single-lip drilling tool are also achieved in terms of guidance stability, diameter accuracy, and surface quality.However, the profile overlaps of the two cutting planes must also be taken into account, because the outer area of the chamfer (32 a) and the outer part of the opposite cutting edge (33 b) each have to bear the cutting load alone, despite the two-edged system, and must therefore be kept as narrow as possible in order to mitigate the heat input into the cutting edges. On the active part of the chamfer (32 a), this is also supported by the bevel and the resulting thinner chip, and slightly increased wear can also be tolerated on the opposite side, since this corner (33 b) does not form the surface. With the center cutting edge (35), the sole share in the machining is less problematic anyway due to the lower cutting speed. However, it will not be possible to do without profile overlaps entirely if one wants to avoid influences from the main cutting edge (34), e.g.through so-called built-up edges, can have an impact extending into the area of the surface-forming skiving bevel (32). The "thread chips" that may occur with some materials, such as those found in stepped skiving bevels, are unlikely to cause problems due to the higher coolant flow rate. Fig.Figure 4 shows a general view of a drilling tool with a round drill pipe together with peripherally common machine elements. The drill head (40a), which projects through the coolant supply area (40), is guided during drilling in a bushing (40b), which is held in a housing with a coolant connection (40c). The drill pipe itself is supported and guided at the other end of the supply area by sealing elements (40d) and clamped into the head of a drive spindle using suitable clamping elements such as a collet (40e). This arrangement is also known as the BTA drilling process and has long been established as state of the art. For limited drilling depths, the drill pipe can also be inserted into a somewhat thicker hollow shaft (41a), whereby the hollow shaft itself can be supported at its front end by a sealing and guide bushing and provided at the rear with a standardized clamping sleeve (41c) for clamping.For drilling machines without an internal spindle through-hole, the tool is provided with a clamping sleeve with a side outlet (42 a) and a rear closure (42 b). An additional splash guard (42 c) can be installed within a machine room to prevent the coolant from escaping freely, as with single-lip drilling technology, and contaminated with chips. Advantages of the invention:

[0015] In addition to the simple design and the resulting cost-effective manufacturing, regrinding, and retooling options, it should be mentioned that this tool design allows the cutting capacity of the 2-flute deep hole drilling technology to be implemented much more effectively. The head cross-section no longer has to be aligned with the twice-grooved tube, meaning that the two chip removal channels can be at least as large as with the previous solid carbide version. And the peripheral coolant supply, in conjunction with possible ejector partial flows, also achieves the necessary flushing in an energy-saving manner with a much lower pressure requirement. The round drill tube is simply more resilient and can be guided more precisely in support steady rests, and even the vibration damping that is often essential for long drill tubes is easier to implement on the round tube.But even for shorter drilling depths, the variant with hollow shank reinforcement (also known as the plunge spindle method) can increasingly be used in areas that were previously reserved for single-lip drills, such as drilling dies or suction rolls. This design is even feasible on older drilling machines without spindles with internal through-holes or rotating coolant supply.

Claims

[1] Deep drilling tool with 2 cutting edges, consisting of: a drill head (10) made of hard metal or ceramic, with a roof-shaped (10 a) or conical (10 b) end geometry, with two main cutting edges (10 c) offset from one another by 180° on the front, with at least two inner channels (10 d) for the coolant supply to these and two free spaces (10 e) for the removal of the chips, a round drill pipe with a conical opening (12) and an intermediate carrier (11) which directs the coolant, which primarily flows back from the two free spaces (10 e) on the drill head (10) and is mixed with chips, through two channels (11 b) into the interior of the pipe (12), and divides the coolant flow supplied on the outside of the drill pipe (12) into direct supply to the cutting area via outer channels (10 f), and indirect supply to the inner channels (10 d), all connected by means of gluing, soldering or welding. [2] Deep drilling tool with 2 cutting edges according to claim 1, characterized by , that: - on one main cutting edge (10c) the outer edge is slightly recessed (31), whereby the opposite main cutting edge becomes the diameter-determining cutting edge. - the diameter-determining cutting edge has a so-called chamfer (32) with or without rounding on its outer edge. - the outer end of the chamfer (32) is located in front of the recessed outer edge of the opposite side (31) when viewed in the drilling direction. - the diameter-determining cutting edge has an inner cutting edge (35) in the central area, the width of which is so large that the radially acting component of all cutting forces results in a preponderance in the direction of the diameter-determining cutting edge, whereby a guiding stability is achieved similar to that in the single-lip drilling technique. [3] Deep drilling tool with 2 cutting edges according to claim 1, characterized by , that: - the drill head (10) has at least two outer channels (10f) whose depth extends radially to the outer surface of the drill pipe (12). - the outer channels (10f) are realized beyond the intermediate support (11) (11c). - the intermediate support (11), in addition to the geometric adaptation to the drill head end (11 a), has two recesses (11 b) as a continuation of the chip removal channels (10 e) with at least the same cross-section into the interior of the pipe. - the intermediate carrier (11) due to its geometric design distributes coolant and chips from both chip spaces of the drill head (10e) via the recesses (11b) into the interior of the drill pipe and at the same time distributes coolant flowing along the outer casing of the drill pipe in the drilling direction via the outer channels (10f) and inner channels (22 / 10d) in equal parts to the two cutting planes and via channel extensions (23) for backflushing reinforcement into the interior of the pipe. [4] Deep drilling tool with 2 cutting edges according to claims 1 and 3, characterized by that the intermediate support (11) consists of steel or is constructed by means of an additive manufacturing process from a suitable material whose properties are comparable to steel. [5] Deep drilling tool with 2 cutting edges according to claims 1 and 3, characterized by that the drill head (10) and intermediate carrier (11) form a common part (13), hereinafter referred to as the base body. [6] Deep drilling tool with 2 cutting edges according to claim 5, characterized by that the base body (13) is provided with soldered or screwed cutting and guiding elements (14). [7] Deep drilling tool with 2 cutting edges according to claim 5, characterized by that the base body (13) is constructed by means of an additive manufacturing process from a material suitable for this purpose and comparable to steel and is provided with wear-resistant inserts, coatings or deposits only in the cutting and guide zones. [8] Deep drilling tool with 2 cutting edges according to claim 5, characterized bythat the base body (13) is constructed entirely from a wear-resistant and cuttable material by means of an additive manufacturing process. [9] Deep drilling tool with 2 cutting edges according to claim 1, characterized by , that: - for limited drilling depths, the drill pipe (12) ends in a thicker hollow shaft (41 a). - the hollow shaft (41 a) is larger in diameter than the drill head (10). - the hollow shaft (41 a) is provided at its end with a standardised clamping sleeve (41 c) for the purpose of clamping it into a drilling spindle. - for drilling spindles without internal passage, the shaft end has a lateral outlet for the removal of chips and coolant (42 a).

Images