Extrusion screw tap

Abstract

According to the present invention, it is possible to provide an extrusion tap (10) having a screw part (14) that includes a complete thread part (24) and an introduction part (22) that is provided continuously with the complete thread part (24) and that has a diameter that decreases toward the tip, and that has a plurality of bead parts (18) provided in the circumferential direction, the bead parts (18) each including a pressing part (18a), a thread top part (18b), and a relief part (18c), in each of the bead portions (18), a tooth shape (28a) in a cross section including the axis (C) direction of the extrusion tap (10) at the pressing portion (18a) varies in the circumferential direction, and therefore, the contact state of the bead portions (18) and a workpiece is improved, cooling performance is improved, and as a result, durability is high.

Description

Technical Field

[0001] This invention relates to extrusion taps, and more particularly to extrusion taps with less wear and improved durability. Background Technology

[0002] A known forming tap has a threaded portion comprising a complete tooth and a guide portion whose diameter decreases towards the front end, continuously arranged with the complete tooth. Multiple ridges are evenly spaced in the circumferential direction on the threaded portion (see Patent Document 1). In such a forming tap, when screwed into a bottom hole in a workpiece from the guide portion side, the multiple ridges engage with the inner wall surface of the bottom hole, causing plastic deformation and forming an internal thread. Therefore, chips are not ejected, and chip blockage or entanglement is avoided. Furthermore, high-strength internal threads can be machined with reduced dimensional accuracy deviations. This simplifies chip removal from the machined internal thread.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent No. 6420515

[0006] Patent Document 2: Japanese Patent Application Publication No. 2001-252827

[0007] Patent Document 3: Japanese Patent Application Publication No. 2004-001103 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] However, the protruding edge of such an extrusion tap contacts the workpiece at a predetermined tooth angle, making it prone to chipping and wear, thus shortening tool life. In contrast, Patent Document 1 reduces load torque by gradually changing the shape of the machining teeth in the guide portion. Furthermore, Patent Document 2 improves tool life by making the depth of the tooth root of the guide portion equal to and constant with the depth of the tooth root of the parallel thread portion of the complete tooth portion. Moreover, Patent Document 3 mitigates the extrusion forming resistance of the portion prone to thread chipping by making the thread crest cut height of the guide portion greater than that of the parallel thread portion of the complete tooth portion. All of the technologies in Patent Documents 1 to 3 define the axial variation of the thread tooth shape and slope.

[0010] The present invention was made against the background described above, and its object is to provide an extrusion tap that reduces the load on the tooth crest portion of the convex ridge and improves durability during plastic forming of internal threads.

[0011] Methods for solving problems

[0012] To achieve this objective, the extrusion tap of the first invention is characterized in that (a) it has a threaded portion and a plurality of ridges are provided circumferentially on the threaded portion, the threaded portion including a complete tooth portion and a guide portion, the guide portion being continuously provided with the complete tooth portion and decreasing in diameter toward the front end, in the extrusion tap, (b) each of the ridges includes a pressing portion, a tooth tip and a clearance portion circumferentially within one of the ridges, and (c) in each of the ridges, in at least one of the pressing portion and the clearance portion, the tooth shape in the cross section containing the shaft of the extrusion tap varies circumferentially.

[0013] The effects of the invention

[0014] In the forming tap of the first invention, there is a threaded portion, and multiple ridges are provided circumferentially on the threaded portion. The threaded portion includes a complete tooth portion and a guide portion, which are continuously arranged with the complete tooth portion and decrease in diameter towards the front end. In the forming tap, each ridge includes a pressing portion, a tooth tip, and a clearance portion. In each of the ridges, in at least one of the pressing portion and the clearance portion, the tooth shape in the cross-section of the axis containing the forming tap changes circumferentially. Therefore, a shape that improves rigidity can be formed at each thread tooth, and the contact state between the ridge and the workpiece material can also be improved. In addition, improved cooling performance can be achieved, resulting in a forming tap with high durability.

[0015] The second invention is characterized in that, in the extrusion tap of the first invention, in each of the convex ridges, the tooth shape in the pressing portion varies circumferentially. This further improves the contact state between the convex ridges and the workable material, and also enhances cooling performance, resulting in a highly durable extrusion tap.

[0016] The third invention is characterized in that, in the forming tap of either the first or second invention, the root diameter clearance in the threaded portion is smaller than the crest diameter clearance. This prevents a portion of the tap's cross-sectional shape from being removed at the root, thus reducing the cross-sectional area and improving the tap's rigidity and breakage strength. Furthermore, the flow of lubricating / cooling oil (coolant) is less obstructed at the root, resulting in better propagation towards the machining point and improved cooling performance. Consequently, a highly durable forming tap can be provided.

[0017] The fourth invention is characterized in that, in the forming tap of either the first or second invention, the clearance of the crest diameter in the threaded portion is greater than the clearance of the intermediate diameter. This further improves the contact between the protrusion and the workable material, and also enhances cooling performance, resulting in a highly durable forming tap. Attached Figure Description

[0018] Figure 1 This is a front view illustrating the structure of an extrusion tap as an embodiment of the present invention.

[0019] Figure 2 It is a section cut by a plane including axis C. Figure 1 A cross-sectional view shown as a portion of the extrusion tap.

[0020] Figure 3 This is an explanation Figure 1 A diagram showing the cross-sectional shape of the thread teeth in the convex part of the extrusion tap.

[0021] Figure 4 It is a diagram that defines the range of variations in the tooth shape in the threaded section.

[0022] Figure 5 This is a diagram illustrating the change in the tooth shape of the convex portion in the comparative example extrusion tap.

[0023] Figure 6 This is a diagram illustrating the relationship between the change in tooth shape and the rectangular shape in the extrusion tap of the comparative example.

[0024] Figure 7 This is a diagram illustrating the relationship between the change in tooth shape and the rectangular shape in the extrusion tap of this embodiment.

[0025] Figure 8 These are photographs showing the forming tap of this embodiment and the forming tap of the comparative example when not in use.

[0026] Figure 9 This is a graph showing the results of a tapping durability comparison test conducted on the extrusion tap of this embodiment and the extrusion tap of the comparative example, respectively.

[0027] Figure 10 These are photographs showing the side views of the forming tap of this embodiment and the forming tap of the comparative example after a tapping durability comparison test.

[0028] Figure 11 These are enlarged views showing the wear patterns of the protruding ridge of the extrusion tap in this embodiment and the protruding ridge of the extrusion tap in the comparative example, respectively.

[0029] Figure 12This is a diagram illustrating the cross-sectional shape of the thread teeth in the convex portion of the extrusion tap according to another embodiment of the present invention, which is equivalent to... Figure 3 The image.

[0030] Figure 13 This is a diagram illustrating the cross-sectional shape of the thread teeth in the convex portion of the extrusion tap in another embodiment of the present invention, which is equivalent to... Figure 3 The image.

[0031] Figure 14 This is a diagram illustrating the cross-sectional shape of the thread teeth in the convex portion of the extrusion tap in another embodiment of the present invention, which is equivalent to... Figure 3 The image.

[0032] Figure 15 This is a diagram illustrating the cross-sectional shape of the thread teeth in the convex portion of the extrusion tap in another embodiment of the present invention, which is equivalent to... Figure 3 The image.

[0033] Figure 16 This is a diagram illustrating the cross-sectional shape of the thread teeth in the convex portion of the extrusion tap in another embodiment of the present invention, which is equivalent to... Figure 3 The image.

[0034] Figure 17 This is a diagram illustrating the cross-sectional shape of the thread teeth in the convex portion of the extrusion tap in another embodiment of the present invention, which is equivalent to... Figure 3 The image. Detailed Implementation

[0035] Preferably, the thread tooth, when viewed from its axial direction, has a generally polygonal cross-section, with the positions of each vertex of the polygon serving as the edge portions protruding radially, and clearance portions with diameters smaller than the edge portions provided between these edge portions. For example, the thread tooth, when viewed from its axial direction, has a generally quadrilateral cross-section, with the positions of the four vertices of the quadrilateral serving as the edge portions protruding radially. That is, four edge portions are provided radially in the circumferential direction. However, it is also possible, for example, that the thread tooth has a generally triangular cross-section when viewed from its axial direction, with three edge portions protruding radially in the circumferential direction. Alternatively, five or more edge portions may be provided radially in the circumferential direction. Alternatively, two portions at the major axis of a generally elliptical shape may protrude radially as edge portions.

[0036] Preferably, the forming tap has an oil groove formed on the outer periphery of the thread teeth, substantially parallel to the axis of the forming tap. This oil groove is used to supply oil to the machining part during tapping with the forming tap. This oil groove is suitable for forming on forming taps with larger diameters, and is not necessary on forming taps with smaller diameters.

[0037] The forming tap is preferably configured to have a cylindrical shank and a threaded portion coaxially disposed on the front end of the shank. The threaded portion is preferably integral with the shank, but it can also be configured to be detachable, allowing the threaded portion to be mounted on the shank for use during tapping operations. Preferably, the forming tap is used with the shank mounted on a tapping machine.

[0038] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Furthermore, for ease of explanation, the dimensions and proportions of the parts used in the following description may not be accurately depicted.

[0039] Example 1

[0040] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0041] Figure 1 This is a front view illustrating the structure of the extrusion tap 10 as an embodiment of the present invention. Figure 2 This is a cross-sectional view showing a portion of the extrusion tap 10 cut along a plane including the axis C. Figure 1 (See the sectional view along line II-II shown). As shown in these figures, the forming tap 10 of this embodiment is configured to have a cylindrical shank 12 and a threaded portion 14 integrally formed on the front end side of the shank 12, coaxial with the shank 12 (on a common axis C). Thread teeth (external threads) 16 corresponding to the internal thread to be machined (the internal thread that the forming tap 10 is machining) are formed on the outer circumferential side of the threaded portion 14. The threaded portion 14 is preferably integrally formed with the shank 12, but it can also be configured to be detachable from the shank 12. In this configuration, during the machining of the internal thread by the forming tap 10, the threaded portion 14 is integrally fixed at the front end of the shank 12.

[0042] The thread teeth 16 are provided with radially protruding ridges 18 at equal intervals in the circumferential direction, and are formed into an external thread shape along a helix corresponding to a predetermined lead angle. These ridges 18 correspond to the portion that bites into the bottom hole (surface portion) of the workpiece during internal thread machining using the extrusion tap 10. In other words, the ridges 18 are equivalent to the functional parts used to plastically deform the bottom hole of the workpiece during internal thread machining using the extrusion tap 10, and are protrusions (ridges, shoulders) that match the shape of the internal thread being machined and are provided radially.

[0043] The protruding ridge 18 is configured to include an inlet portion 18a, a tooth crest 18b, and a clearance portion 18c. The diameters of the pressing portion 18a and the clearance portion 18c are smaller than the diameter of the tooth crest 18b. The protruding ridge 18 is formed circumferentially on the external thread, and therefore the tooth crest 18b, the clearance portion 18c with a diameter smaller than that of the tooth crest 18b, and the pressing portion 18a are sequentially arranged therein. For example, Figure 2 As shown, the threaded tooth 16 has a generally quadrilateral cross section (observation section) when viewed from the axis C. The positions corresponding to the four vertices of the quadrilateral are provided as the tooth tips 18b in the radial direction, and between these tooth tips 18b are clearance portions 18c and pressing portions 18a with a diameter smaller than the protruding ridge portion 18.

[0044] like Figure 1 As shown, the threaded portion 14 is configured to include: a guide portion 22, which is tapered with a diameter that gradually decreases towards the front end (the diameter becomes smaller towards the front end); and a complete tooth portion 24, which is cylindrical with a substantially constant diameter. The guide portion 22 is used in the machining of the internal thread by the extrusion tap 10 to roll-form the internal thread by plastically deforming the surface portion of the bottom hole in the workpiece, corresponding to a structure of several teeth (e.g., 2 to 8 teeth) starting from the front end of the thread tooth 16. The complete tooth portion 24 is used in the machining of the internal thread by the extrusion tap 10 to finish the surface of the internal thread formed by the guide portion 22, improving the self-guiding property of the threaded portion 14. The complete tooth portion 24 is formed to have a shape substantially consistent with the shape of the thread tooth of the internal thread that is the object of machining by the extrusion tap 10. Unless otherwise specified in this embodiment, one or more oil grooves may be formed in the threaded portion 14 along the axial direction C. Alternatively, oil holes may be provided.

[0045] In the extrusion tap 10 configured as described above, an internal thread is formed (extruded) by causing the protruding ridge 18 of the thread tooth 16 to bite into the surface portion of the bottom hole formed in the workpiece, based on the plastic deformation of the surface portion. For example, the extrusion tap 10 is mounted on a tapping machine at its shank 12, which is axially guided to rotate, for example, to the right when viewed from the shank 12 side, relative to the bottom hole to which the internal thread is to be formed, thereby screwing the thread portion 14 provided at the front end of the shank 12 into the bottom hole. As a result, the pressing portion 18a of the protruding ridge 18 located at the guide portion 22 bites into the surface portion (inner circumferential surface) of the bottom hole, causing the surface portion to plastically deform, thereby rolling and forming the internal thread, and the surface of the formed internal thread is finished by the complete tooth portion 24, forming the internal thread to be formed in the bottom hole. The processing based on such a forming tap 10 is suitable for forming internal threads in materials with excellent ductility. It has the advantage of forming high-precision internal threads without producing chips. On the other hand, in forming this internal thread, a relatively large torque is applied to the forming tap 10.

[0046] Figure 3 This is a diagram illustrating the cross-sectional shape (tooth shape) of the threaded teeth in the protruding ridge 18. Figure 3 (a) is a diagram illustrating the changes in the cross-sectional shape of the circumferentially continuous pressing part 18a, the tooth tip 18b, and the clearance part 18c of the tap. Figure 3 (b) is a diagram showing cross-sections 28a, 28b, and 28c of the pressing part 18a, the tooth tip 18b, and the clearance part 18c in the plane containing the axis C (shaft) of the tap. Furthermore, in Figure 3 In (b), a single-dotted line is marked at a position corresponding to the root diameter of the tooth crest 18b, showing the radial relative positional relationship of the sections 28a, 28b, and 28c of the pressing part 18a, the tooth crest 18b, and the clearance part 18c from the axis C of the tap. Additionally, in Figure 3 In (a), the solid line represents the ridge line from the pressing part 18a through the tooth top 18b to the avoidance part 18c.

[0047] In the extrusion tap 10 of this embodiment, as Figure 3 (a) and Figure 3 As shown in (b), in the thread tooth 16 of the tap, the root diameter remains unchanged. In a ridge 18, in the pressing portion 18a, the height of the thread tooth 16 from the root 26 increases as it moves towards the tooth crest 18b. Conversely, in the clearance portion 18c, the height of the thread tooth 16 from the root diameter decreases as it moves away from the tooth crest 18b. Thus, in each ridge 18, the tooth shape 28 in the section containing the pressing portion 18a along the axis C of the tap 10 changes circumferentially. Furthermore, in the clearance portion 18c, the tooth shape 28 also changes circumferentially.

[0048] Figure 4 This is a diagram defining the range of variation of the tooth shape 28. Figure 4 The tooth shape 28 is shown in a cross section of the shaft C containing the extrusion tap 10, with the tooth tip 18b of the protruding ridge 18 as shown. Figure 4 The rectangular shape 30 surrounding the tooth crest 18b is defined as the upper limit (maximum region) of the variation range of the tooth shape 28. The upper side 30a and lower side 30b of the rectangular shape 30 are parallel to the axis C of the forming tap 10. Furthermore, the upper side 30a is positioned at the tooth crest 18b, and the lower side 30b is positioned at the lower of the two tooth bases 26 located on either side of the tooth crest 18b, in other words, the tooth base closer to the axis C. Additionally, Figure 4 The lateral length w of the rectangular shape 30, in other words, the length of the upper side 30a and the lower side 30b, is also the distance between the left side (i.e., the guide portion 22 side) 30c and the right side (i.e., the complete tooth side) 30d, which is equivalent to the pitch of the thread lead of the thread tooth 16. At this time, the left side 30c and the right side 30d are respectively located at the center of the tooth base 26 on both sides of the thread tooth 16 in the direction of axis C. The above is the definition related to the tooth crest 18b, but regarding the pressing portion 18a or the relief portion 18c, the upper side 30a and the lower side 30b are based on the tooth crest in the cross section containing their respective axes. The distance between the upper and lower sides is equal to the distance between the upper and lower sides in the tooth crest 18b. Therefore, the deformation range of the pressing portion 18a and the relief portion 18c is equal in area to the tooth crest 18b, and only the position of the deformation range moves according to the tooth crest height.

[0049] As described above, in this embodiment, the root diameter of the threaded tooth remains unchanged in one of the protruding portions 18. On the other hand, in the pressing portion 18a, the height of the threaded tooth 16 from the root diameter increases as it moves towards the tooth crest 18b, while in the clearance portion 18c, the height of the threaded tooth 16 from the root diameter decreases as it moves away from the tooth crest 18b. Therefore, the tooth shape 28a of the pressing portion 18a and the tooth shape 28c of the clearance portion 18c change continuously in the circumferential direction. Moreover, the maximum size of the changing tooth shapes 28a and 28b is the tooth shape 28b of the tooth crest 18b in the protruding portion 18. Therefore, the changes in the tooth shapes 28a and 28c in the pressing portion 18a and the clearance portion 18c are within the range of the rectangular shape 30 defined based on the cross-sectional shape 28b of the tooth crest 18b. In addition, the changes in the tooth shapes 28a and 28c mentioned here refer to continuous changes and do not include discontinuous shape changes such as the tooth partially disappearing due to the oil groove provided in the tap.

[0050] Figure 5 This diagram illustrates the change in the tooth shape 66 of the convex portion 68 in the comparative example extrusion tap 60, and is consistent with the aforementioned... Figure 3The corresponding diagram. (and) Figure 3 Similarly, Figure 5 (a) is a diagram illustrating the changes in the cross-sectional shape of the circumferentially continuous pressing part 68a, the tooth tip 68b, and the clearance part 68c of the tap. Figure 5 (b) is a cross-sectional view of the pressing part 68a, the tooth tip 68b, and the clearance part 68c in the plane containing the axis C of the tap. Furthermore, in Figure 5 (b) also with Figure 3 (b) Similarly, a single-dotted line is marked at a position corresponding to the root diameter of the tooth crest 18b, showing the radial relative positional relationship of the cross sections 28a, 28b, and 28c of the pressing portion 18a, the tooth crest 18b, and the clearance portion 18c from the axis C of the tap. In this comparative example, the pressing tap 60, in the portion of the convex portion 68 other than the tooth crest 68b, constitutes a clearance portion by making the root diameter smaller than that of the tooth crest 18b. On the other hand, the difference between the tooth crest diameter and the root diameter is approximately the same value in any of the pressing portion 68a, the tooth crest 68b, and the clearance portion 68c.

[0051] Figure 6 as well as Figure 7 The figures illustrate the relationship between the changes in tooth shapes 26 and 66 in the forming tap 10 of this embodiment and the forming tap 60 of the comparative example and the rectangular shape 30. Figure 6 (b) is a diagram illustrating the change in tooth shape 66 of the comparative example extrusion tap 60, equivalent to Figure 5 (b). Figure 6 (a) is a cross-sectional view perpendicular to the axis of tap 60, and is an enlarged view showing a convex ridge. Figure 6 (a) shows Figure 6 (b) shows the positions of tooth shapes 66a, 66b, and 66c within tap 60. Additionally, Figure 7 (b) is a diagram illustrating the change in the tooth shape 26 of the extrusion tap 10 in this embodiment, equivalent to Figure 3 (b). Figure 7 (a) is a cross-sectional view perpendicular to the axis of tap 10, and is an enlarged view showing a convex ridge. Figure 7 (a) shows Figure 7 (b) shows the positions of tooth shapes 28a, 28b, and 28c in tap 10. Furthermore, in Figure 6 (b) and Figure 7 (b) The blackened parts show the parts outside the scope of the definition of shape change.

[0052] exist Figure 6 as well as Figure 7In this design, the diameter of the imaginary cylinder in the tooth crest section containing the shaft, which is connected to the crest of the threaded tooth of the tap and coaxial with the axis of the tap, is represented as the crest diameter. The diameter of the imaginary cylinder in the tooth crest section containing the shaft, whose width is equal to the width of the threaded tooth and coaxial with the axis of the tap, is represented as the intermediate diameter. The diameter of the imaginary cylinder in the tooth crest section containing the shaft, which is connected to the root of the tooth and coaxial with the axis of the tap, is represented as the root diameter. The crest diameter is represented by a dashed line, the intermediate diameter by a dotted line, and the root diameter by a single-dotted line. Additionally, the rectangular shape 30 corresponding to the tooth shapes of the crests 18b and 68b is shown as a rectangle with double-dotted lines. In the comparative example extrusion tap 60, as... Figure 6 As shown in (b), before and after the tooth tip 68b, the tooth shape 66 does not change within the range of the rectangular shape 30. On the other hand, in the extrusion tap 10 of this embodiment, as... Figure 7 As shown in (b), the tooth shape 28 varies within the range of the rectangular shape 30 before and after the tooth crest 18b.

[0053] Figure 8 These are photographs showing the forming tap 10 of this embodiment and the forming tap 60 of the comparative example in their unused state. Figure 8 (a) is the side view of the comparative example extrusion tap 60. Figure 8 (b) is the side surface of the extrusion tap 10 in this embodiment. Additionally, Figure 8 (c) is an oblique view of the front end of the comparative example extrusion tap 60. Figure 8 (d) is a view of the front end of the extrusion tap 10 of this embodiment taken at an angle.

[0054] Next, the results of the durability test of the extrusion tap 10 of this embodiment conducted by the inventors of the present invention will be explained.

[0055] Figure 9 This figure shows the results of a comparative tapping durability test conducted on a common machining material for the forming tap 10 of this embodiment and the forming tap 60 of the comparative example, respectively. In this test, the forming tap 10 of this embodiment and the forming tap 60 of the comparative example were tapped under the following test conditions, and the resulting internal threads were verified by a feeler gauge. The number of holes machined by each sample was compared until the feeler gauge could not pass through (GP-OUT). This test was performed twice for each forming tap 10 and 60.

[0056] [Experimental Conditions]

[0057] • Processing material: Carbon steel S50C (JIS)

[0058] Processing speed: 10m / min

[0059] Hole depth: 12mm

[0060] • Bottom hole diameter: 5.54mm

[0061] • Bottom hole shape: Through hole

[0062] • Machine used: Vertical machining center

[0063] • Oil-based: Water-soluble oil-based

[0064] • Size: M6×1 (4 protruding edges)

[0065] like Figure 9 As shown, in the comparative example's forming tap 60, the forming tap 60 wore down at approximately 1400 holes and approximately 2800 holes, respectively, resulting in defective internal threads. In the forming tap 10 of this embodiment, one forming tap 10 wore down at approximately 4000 holes, resulting in defective internal threads, while the other did not wear down even after more than 4000 holes, remaining in a state where further processing could continue. Therefore, it can be seen that the wear resistance of the forming tap 10 of this embodiment is significantly improved. Furthermore, the tool base material of the forming tap 10 of this embodiment is fused HSS (High Speed ​​Steel) with a hardness of 64 HRC, while the tool base material of the forming tap 60 of the comparative example is powdered HSS (High Speed ​​Steel) with a hardness of 67 HRC.

[0066] Figure 10 These are photographs showing the side views of the extrusion tap 10 of this embodiment and the extrusion tap 60 of the comparative example during the tapping durability comparison test. Figure 10 (a) shows the side profile of the comparative example forming tap 60 after machining 1400 holes. (As shown) Figure 10 As shown by the arrow in (a), the wear of the protruding part 68 is significant, reaching the durability limit. Figure 10 (b) shows the side of the extrusion tap 10 of this embodiment after machining 2800 holes. No wear was found on the protrusion 18.

[0067] in addition, Figure 11 This is an enlarged view showing the wear patterns of the protruding ridge 18 of the forming tap 10 and the protruding ridge 68 of the forming tap 60 of the comparative example at time points of 4000 holes and 1400 holes, respectively, for a specification where the change in the tooth crest diameter is greater than the change in the intermediate diameter in one embodiment. Figure 11 (a) shows the ridge 68 of the comparative example extrusion tap 60. Wear is concentrated at the tooth tip, and severe wear is observed particularly at the tooth tip of the ridge of the complete tooth near the inlet. Figure 11(b) shows the convex portion 18 of the extrusion tap 10 of this embodiment. Friction marks are not concentrated at the tooth tip but are dispersed over a large area on the side. It can be confirmed that the contact state between the pressing portion and the workpiece material is improved, and the load is not concentrated at the tooth tip of the convex portion, thus achieving dispersion.

[0068] The forming tap 10 according to this embodiment has a threaded portion 14, which includes a complete tooth portion 24 and a guide portion 22 continuously disposed with the complete tooth portion 24 and whose diameter decreases towards the tip. A plurality of protruding ridges 18 are provided circumferentially on the threaded portion 14, and each protruding ridge 18 includes a pressing portion 18a, a tooth tip 18b, and a clearance portion 18c. At the pressing portion 18a, the tooth shape 28a of each protruding ridge 18 in the cross-section including the axial direction C of the forming tap 10 changes circumferentially. Therefore, the rigidity of the thread tooth is improved, suppressing vibration during machining. Furthermore, improved cooling performance can be achieved, resulting in a forming tap 10 with high durability.

[0069] Furthermore, in the extrusion tap 10 according to this embodiment, in each of the convex ridges 18, at the clearance portion 18c, the tooth shape 28c changes in the circumferential direction, thus ensuring sufficient clearance while suppressing damage to the rigidity of the thread teeth, and improving cooling performance. As a result, a highly durable extrusion tap 10 can be provided.

[0070] Furthermore, according to the extrusion tap 10 of this embodiment, since the clearance of the crest diameter in the thread portion 14 is greater than the clearance of the root diameter, it does not hinder the intrusion of lubricating / cooling oil (coolant), thus improving the cooling performance. As a result, an extrusion tap 10 with high durability can be provided.

[0071] Furthermore, according to the extrusion tap 10 of this embodiment, since the outer diameter clearance of the threaded portion 14 is greater than the intermediate diameter clearance, the contact state between the protrusion and the workpiece material can be further improved. In addition, the cooling performance can be improved, resulting in an extrusion tap 10 with high durability.

[0072] Next, other embodiments of the present invention will be described. Furthermore, in the following description, common parts of the embodiments will be labeled with the same reference numerals and their descriptions will be omitted.

[0073] Example 2

[0074] Figure 12 This is a diagram illustrating the cross-sectional shape 98 of the protruding ridge 88 in another embodiment of the present invention, which is different from that in the aforementioned embodiment 1. Figure 3 The corresponding diagram. Figure 12(a) is a diagram illustrating the changes in the cross-sectional shape of the circumferentially continuous pressing part 88a, the tooth tip 88b, and the clearance part 88c of the tap. Figure 12 (b) is a diagram showing the cross-sections 98a, 98b, and 98c of the pressing part 88a, the tooth tip 88b, and the clearance part 88c in the plane containing the axis C of the tap. Figure 12 (b) also with Figure 3 (b) Similarly, a single-dotted line is marked at a position corresponding to the root diameter of the tooth crest 88b, showing the radial relative position of the sections 98a, 98b, and 98c of the pressing part 88a, the tooth crest 88b, and the clearance part 88c from the axis C of the tap.

[0075] like Figure 12 As shown, in the convex ridge 88 of this embodiment, the angle of the tooth crest portion having a triangular tooth shape 98 does not change. On the other hand, the amount of protrusion from a position corresponding to the root diameter increases as the tooth shape 98a in the pressing portion 88a moves towards the tooth crest 88b, and decreases at the clearance portion 88c as the tooth shape 98c moves away from the tooth crest 88b. That is, the amount of triangular protrusion is greatest at the tooth crest 88b.

[0076] In the extrusion tap 10 having the protruding ridge 118 of this embodiment, the same effect as in the aforementioned embodiment can also be obtained.

[0077] Example 3

[0078] Figure 13 This is a diagram illustrating the cross-sectional shape 128 of the protruding ridge 118 in another embodiment of the present invention, which is different from that in the aforementioned embodiment 1. Figure 3 The corresponding diagram. Figure 13 (a) is a diagram illustrating the changes in the cross-sectional shape of the circumferentially continuous pressing part 128a, the tooth tip 128b, and the clearance part 128c of the tap. Figure 13 (b) is a cross-sectional view of the pressing part 128a, the tooth tip 128b, and the clearance part 128c in the plane containing the axis C of the tap. Figure 13 (b) also with Figure 3 (b) Similarly, a single-dotted line is marked at a position corresponding to the root diameter of the tooth crest 118b, showing the radial relative position of the sections 128a, 128b, and 128c of the pressing part 118a, the tooth crest 118b, and the clearance part 118c from the axis C of the tap.

[0079] like Figure 13As shown, in the convex portion 118 of this embodiment, the angle of the tooth tip portion with a triangular tooth shape 128 changes, thereby changing the tooth shape 128a in the pressing portion 118a as it moves toward the tooth tip 118b, and in the avoidance portion 128c, the tooth shape 128c also changes as it moves away from the tooth tip 118b. That is, it has the sharpest angle at the tooth tip 118b.

[0080] In the extrusion tap 10 having the protruding ridge 118 of this embodiment, the same effect as in the aforementioned embodiment can also be obtained.

[0081] Example 4

[0082] Figure 14 This is a diagram illustrating the cross-sectional shape 228 of the protruding ridge 218 in another embodiment of the present invention, which is different from that in the aforementioned embodiment 1. Figure 3 The corresponding diagram. Figure 14 (a) is a diagram illustrating the changes in the cross-sectional shape of the circumferentially continuous pressing part 228a, the tooth tip 228b, and the clearance part 228c of the tap. Figure 14 (b) is a cross-sectional view of the pressing part 228a, the tooth tip 228b, and the clearance part 228c in the plane containing the axis C of the tap. Figure 14 (b) also with Figure 3 (b) Similarly, a single-dotted line is marked at a position corresponding to the root diameter of the tooth crest 218b, showing the radial relative position of the sections 228a, 228b, and 228c of the pressing part 218a, the tooth crest 218b, and the clearance part 118c from the axis C of the tap.

[0083] like Figure 14 As shown, in the convex portion 218 of this embodiment, the tooth shape 228, which has a generally triangular shape, has a curved tip. Due to the change in its radius of curvature, the tooth shape 228a in the pressing portion 218a changes as it moves towards the tooth tip 218b, and in the clearance portion 228c, the tooth shape 228c also changes as it moves away from the tooth tip 218b. That is, it has the smallest radius of curvature at the tooth tip 218b.

[0084] In the extrusion tap 10 having the protruding ridge 218 of this embodiment, the same effect as in the aforementioned embodiment can also be obtained.

[0085] Example 5

[0086] Figure 15 This is a diagram illustrating the cross-sectional shape 328 of the protruding ridge 318 in another embodiment of the present invention, which is different from that in the aforementioned embodiment 1. Figure 3 The corresponding diagram. Figure 15(a) is a diagram illustrating the changes in the cross-sectional shape of the circumferentially continuous pressing part 328a, the tooth tip 328b, and the clearance part 328c of the tap. Figure 15 (b) is a sectional view of the pressing part 328a, the tooth tip 328b, and the clearance part 328c in the plane containing the axis C of the tap. Figure 15 (b) also with Figure 3 (b) Similarly, a single-dotted line is marked at a position corresponding to the root diameter of the tooth crest 318b, showing the radial relative position of the sections 328a, 328b, and 328c of the pressing part 318a, the tooth crest 318b, and the clearance part 318c from the axis C of the tap.

[0087] like Figure 15 As shown, in the protruding ridge 318 of this embodiment, the size of the removal varies in the tooth shape 328, which has a trapezoidal shape with the top removed from the triangle. Thus, the tooth shape 328a in the pressing portion 318a changes as it moves towards the tooth tip 318b, and in the clearance portion 328c, the tooth shape 328c also changes as it moves away from the tooth tip 318b. That is, the amount removed is minimal at the tooth tip 318b. It should be noted that the removal mentioned here is for illustrative purposes only and does not refer to the manufacturing method.

[0088] In the extrusion tap 10 having the protruding ridge 318 of this embodiment, the same effect as in the aforementioned embodiment can also be obtained.

[0089] Example 6

[0090] Figure 16 This is a diagram illustrating the cross-sectional shape 428 of the protruding ridge 418 in another embodiment of the present invention, which is different from that in the aforementioned embodiment 1. Figure 3 The corresponding diagram. Figure 16 (a) is a diagram illustrating the changes in the cross-sectional shape of the circumferentially continuous pressing part 428a, the tooth tip 428b, and the clearance part 428c of the tap. Figure 16 (b) is a sectional view of the pressing part 428a, the tooth tip 428b, and the clearance part 428c in the plane containing the axis C of the tap. Figure 16 (b) also with Figure 3 (b) Similarly, a single-dotted line is marked at a position corresponding to the root diameter of the tooth crest 418b, showing the radial relative position of the sections 428a, 428b, and 428c of the pressing part 418a, the tooth crest 418b, and the clearance part 418c from the axis C of the tap.

[0091] like Figure 16As shown, in this embodiment, the tooth shape 428a of the pressing part 418a changes in a different way than the tooth shape 428c of the avoidance part 418c. The change in the tooth shape 428a of the pressing part 418a is different from that described above. Figure 13 The embodiment shown is the same, except that the angle of the tooth crest portion of the triangular tooth shape 428a changes so that it becomes the sharpest angle at the tooth crest 418b. Furthermore, the change in the tooth shape 428c of the clearance portion 418c is the same as described above. Figure 14 The same embodiment is shown, in a tooth shape 428 having a generally triangular shape, the tooth crest has a curve, and the tooth shape 428c at the relief portion 428c changes by the variation of its radius of curvature. Specifically, the radius of curvature that is minimum at the tooth crest 418b increases as it moves away from the tooth crest 418b at the relief portion 428c.

[0092] In the extrusion tap 10 having the protruding ridge 418 of this embodiment, the same effect as in the aforementioned embodiment can also be obtained.

[0093] Furthermore, in this embodiment, the change in the tooth shape 428a of the pressing part 418a is equivalent to the aforementioned... Figure 14 In the embodiment, the change in the tooth shape 428c of the avoidance part 418c is equivalent to Figure 15 This is one embodiment, but not a limitation thereof. In other words, the combination is not limited as long as the change in the tooth shape 428a of the pressing part 418a and the change in the tooth shape 428c of the avoidance part 418c are different from each other.

[0094] Example 7

[0095] Figure 17 This is a diagram illustrating the cross-sectional shape 528 of the protruding ridge 518 in another embodiment of the present invention, which is different from that in the aforementioned embodiment 1. Figure 3 The corresponding diagram. Figure 17 (a) is a diagram illustrating the changes in the cross-sectional shapes 528a, 528b, and 528c of the circumferentially continuous pressing part 518a, tooth tip 518b, and clearance part 518c of the tap. Figure 17 (b) is a cross-sectional view of the pressing part 518a, the tooth tip 518b, and the clearance part 518c in the plane containing the axis C of the tap. Figure 17 (b) also with Figure 3 (b) Similarly, a single-dotted line is marked at a position corresponding to the root diameter of the tooth crest 518b, showing the radial relative position of the sections 528a, 528b, and 528c of the pressing part 518a, the tooth crest 518b, and the clearance part 518c from the axis C of the tap.

[0096] like Figure 17 As shown, in the protruding ridge 518 of this embodiment, and Figure 16 The embodiment shown is the same, but the way the tooth shape 528a of the pressing part 518a changes is different from the way the tooth shape 528c of the avoidance part 518c changes. That is, the change in the tooth shape 528a in the pressing part 518a is different from that described above. Figure 13 The embodiment shown is the same, except that the angle of the tooth crest portion of the triangular tooth shape 528a changes so that it becomes the sharpest angle at the tooth crest 518b. Furthermore, the change in tooth shape 528c in the clearance portion 518c is the same as described above. Figure 15 Similar to the embodiment shown, in the tooth shape 528 having a generally triangular shape, the tooth crest has a curve, and the tooth shape 528c in the clearance portion 528c changes by varying its radius of curvature. Specifically, the radius of curvature, which is smallest in the tooth crest 518b, increases in the clearance portion 528c as it moves away from the tooth crest 518b. Furthermore, Figure 16 The top of the tooth shape 428 of the convex ridge 418 shown extends from the pressing portion 418a through the tooth tip 418b to the clearance portion 418c. Figure 16 (b) is located near the center in the left-right direction, in contrast, Figure 17 The convex ridge 518 shown has a tooth-shaped ridge 528 whose top is eccentrically oriented in either direction. Specifically, in Figure 17 In the example, at the pressing part 518a, the top of the triangle 528a is located at... Figure 17 In (b), the position is on the left side; on the other hand, at the tooth crest 518b, the apex of triangle 528b is located... Figure 17 (b) is located on the right side. Furthermore, at the avoidance section 518c, the apex of triangle 528c is again located... Figure 17 (b) is located on the left side. Thus, from the pressing part 518a, via the tooth tip 518b, to the clearance part 518c, the apex of the triangle 528 is... Figure 17 (b) Move to the opposite side via the center of triangle 528 in the left-right direction (in other words, the axis of the tap).

[0097] In the extrusion tap 10 having the protruding ridge 518 of this embodiment, the same effect as in the aforementioned embodiment can also be obtained.

[0098] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, this is only one implementation method. The present invention can be implemented in various ways with modifications and improvements based on the knowledge of those skilled in the art.

[0099] For example, in the aforementioned embodiments 1-2, the clearance of the root diameter is 0, but it is not limited to this. At the threaded portion 14, it can also be varied under the condition that the clearance is smaller than that of the crest diameter and / or smaller than that of the intermediate diameter. In this way, it can contribute to the structure of the extrusion tap with high durability.

[0100] Furthermore, in the aforementioned embodiments 1-7, each triangle is bilaterally symmetrical, but this is not a limitation. For example, it can also be as follows: Figure 7 As shown in the embodiment, the tooth shape 528a in the pressing part 518a, the tooth shape 528b in the tooth tip 518b, and the tooth shape 528c in the clearance part 518c are all asymmetrical in either direction of the axis C with the tip close to the tap 10. In this way, for example, it is possible to process internal threads corresponding to sawtooth threads.

[0101] The extrusion tap of the present invention is used in such a way that, by screwing it into a bottom hole provided in the workpiece from the inlet side, the protrusion bites into the inner wall surface of the bottom hole, causing it to plastically deform, thereby forming an internal thread. Various methods can be employed, for example, by integrally providing a drill bit or reamer for machining the bottom hole on the front end side of the tap, and by integrally providing an inner diameter finishing edge or pressing ridge for finishing the internal thread.

[0102] The forming tap preferably has three or more rows of protrusions arranged at equal intervals around the axis in a continuous manner parallel to the axis. However, various other arrangements are also possible, such as arranging the protrusions in a continuous spiral shape that twists around the axis, or arranging them at unequal intervals around the axis. If necessary, the oil groove for supplying cutting fluid can also be arranged axially with the external thread cut off.

[0103] Since extrusion taps do not produce chips, they can effectively tap both blind and through holes to form internal threads. According to the present invention, even when extruding internal threads under conditions prone to melting, such as high-speed machining and the use of low-lubricating oils (water-soluble lubricants, etc.), frictional torque and heat generation can be reduced and melting suppressed without compromising the durability of the protrusions, thus improving tool life. However, extrusion can also be performed at low speeds or using non-water-soluble lubricating oils with high lubricity.

[0104] This invention relates to the shape of the protruding part of an external thread, and its manufacturing method is not particularly limited. This invention can also be applied when the external thread of a forming tap is formed using manufacturing techniques other than grinding wheels.

[0105] The extrusion tap of the present invention is not limited to the aforementioned base material, but may also be made of tool materials such as superhard alloys and ceramics. In addition, it can also be coated with compound films such as TiN, TiCN, TiAlN, CrN, DLC (Diamond Like Carbon) films, diamond films, etc., or subjected to water vapor treatment, nitriding treatment, etc., as needed.

[0106] Explanation of reference numerals in the attached figures

[0107] 10 forming tap

[0108] 12 handles

[0109] 14 Threaded section

[0110] 16 threads

[0111] 18 protruding ridges

[0112] 18a Pressing Part

[0113] 18b tooth top

[0114] 18c avoidance section

[0115] 22 Import Section

[0116] 24 complete teeth

[0117] 26 teeth bottom

[0118] 28 teeth shape

[0119] 28a (pressing part) tooth shape

[0120] 28b (tooth tip) tooth shape

[0121] 28c (avoidance part) tooth shape

[0122] The upper limit of the variation range of 30 tooth shapes (rectangular shape).

[0123] 30a top

[0124] 30b below

[0125] 30c left

[0126] 30d right

Claims

1. A forming tap having a threaded portion and having a plurality of convex ridges arranged circumferentially on the threaded portion, the threaded portion comprising a complete tooth portion and a guide portion, the guide portion being continuously disposed from the complete tooth portion and decreasing in diameter toward the front end, characterized in that, The protruding ridges each include a pressing part, a tooth tip, and a clearance part along the circumferential direction within one ridge. In each of the protruding ridges, in at least one of the pressing portion and the clearance portion, the tooth shape in the cross section of the shaft containing the extrusion tap varies in the circumferential direction.

2. The forming tap according to claim 1, characterized in that, In each of the protruding ridges, in the pressing portion, the tooth shape varies in the circumferential direction.

3. The forming tap according to claim 1 or 2, characterized in that, The clearance at the root diameter of the threaded portion is less than the clearance at the crest diameter.

4. The forming tap according to claim 1 or 2, characterized in that, The clearance of the crest diameter in the threaded section is greater than the clearance of the intermediate diameter.

Images