Boosting Tap

Abstract

To provide a cold forming tap capable of reducing shape collapsing of a crest of a rolled female screw.SOLUTION: A cold forming tap 1 comprises: a male screw 3; a groove; and an inner-diameter finishing blade 61. A chamfer 31 of the male screw 3 is provided connected to a complete crest 32 and becomes smaller in a diameter toward a tip. The groove is provided in parallel with an axial center over the complete crest 32 and the chamfer 31 so as to divide a screw crest 71 of the male screw 3. The inner-diameter finishing blade 61 is provided along an opening end opposite to a rotation direction of the cold forming tap 1 of the groove in the chamfer 31 and the complete crest 32. The inner-diameter finishing blade 61 cuts and removes a top part of the screw crest of the female screw formed on a surface layer of a lower hole 90. A height of a first-stage finishing blade 611 of the inner-diameter finishing blade 61 located in the chamfer 31 is lower than that of a second-stage finishing blade 612 of the inner-diameter finishing blade 61 formed in a part corresponding to the screw crest 71 of the tip in the complete crest 32.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present invention relates to a raising tap.

Background Art

[0002] Patent Document 1 discloses a raising tap with an internal diameter finishing edge (hereinafter referred to as "raising tap"). The thread portion of the raising tap includes a full thread portion and an engaging portion. The engaging portion is provided continuously with the full thread portion and has a smaller diameter toward the tip. From the engaging portion to the first full thread (the thread at the very tip of the full thread portion), a protruding portion and a relief portion are provided alternately. The protruding portion sequentially bites into the inner peripheral surface of the pilot hole and plastically deform it to form an internal thread. The raising tap is provided with at least one groove so as to divide the thread of the male thread portion in the axial direction. The groove straddles the full thread portion and the engaging portion and is parallel to the axis. An internal diameter finishing edge is provided on the full thread portion so that the inner wall surface of the groove functions as a rake face. The internal diameter finishing edge cuts and removes the top portion of the thread of the internally threaded portion raised by plastic deformation.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the raising tap reverses and returns after the forging of the internal thread is completed, there is a possibility that the internal diameter finishing edge contacts the inner diameter portion of the thread and rubs against it from the opposite direction of the rake face, crushing or shaving the shape of the processed thread crest.

[0005] Furthermore, the above-mentioned friction phenomenon could potentially exacerbate abrasive wear on the relief surface of the internal finishing edge of the build-up tap. In the case of soft materials, it could also potentially cause workpiece adhesion. The internal finishing edge is sometimes formed with a slight back taper so that it is approximately the same diameter as the cutting portion at the tip of the build-up tap. In this case, the actual finishing of the internal diameter is performed by the internal finishing edge near the first complete peak after the plastic deformation of the build-up tap is complete. The internal finishing edge at the cutting portion may be cut during the build-up process, but it does not finish the final internal diameter dimension. However, since it is approximately the same diameter as the complete peak (with a diameter larger by the amount of the back taper), there was a possibility that the internal finishing edge at the cutting portion would experience friction when the build-up tap reversed and returned.

[0006] The objective of the present invention is to provide a raised tap that can reduce deformation of the thread crest shape of a roll-formed female screw. [Means for solving the problem]

[0007] This invention The One embodiment of a spool tap is a spool tap that forms a female thread by plastically deforming a pilot hole in a workpiece, comprising: a male thread portion having a complete crest portion and a cutting portion that is continuous with the complete crest portion and becomes smaller in diameter towards the tip; a groove provided parallel to the axis, spanning the complete crest portion and the cutting portion so as to divide the thread of the male thread portion; and an internal diameter finishing blade provided along the opening end of the groove opposite to the rotation direction of the spool tap in the cutting portion and the complete crest portion, for cutting off the top portion of the thread of the female thread, wherein, when the height of the internal diameter finishing blade is the distance from the axis of the spool tap, the height on the cutting portion side is lower than the height of the portion corresponding to the very tip of the thread in the complete crest portion. Furthermore, a stepped portion is provided between the cutting portion and the leading edge of the complete thread portion, such that the height of the cutting portion is lower than the height of the complete thread portion. This is characterized by the fact that, when the raised tap is removed from the workpiece during reverse rotation, the interference of the inner diameter finishing blade at the cutting portion with the threads of the formed female thread, which can cause the threads to collapse, can be reduced.

[0008] Furthermore, foodAttached part And finished All Mountain Department The most Between the threads at the tip established Step department Furthermore, with a raised tap, the height of the cutting portion can be easily reduced compared to the height of the portion corresponding to the leading edge of the thread in the complete thread section of the internal diameter finishing blade.

[0009]

[0010] A second embodiment of the present invention is a build-up tap that forms a female thread by plastically deforming a pilot hole in a workpiece, comprising: a male thread portion having a complete crest portion and a cutting portion that is continuous with the complete crest portion and becomes smaller in diameter towards the tip; a groove provided parallel to the axis and spanning the complete crest portion and the cutting portion so as to divide the thread of the male thread portion; and an internal diameter finishing blade provided along the opening end of the groove on the opposite side of the rotation direction of the build-up tap in the cutting portion and the complete crest portion, for cutting off the top portion of the thread of the female thread, wherein, when the height of the internal diameter finishing blade is the distance from the axis of the build-up tap, the height on the cutting portion side is lower than the height of the portion corresponding to the leading edge of the thread in the complete crest portion, and the internal diameter finishing blade is provided with a back taper in which the height decreases from the portion corresponding to the leading edge of the thread in the complete crest portion toward the rear end. This reduces the risk of the internal diameter finishing blade at the cutting edge interfering with the threads of the formed female screw when the tap is removed from the workpiece during reverse rotation, thus preventing the threads from being damaged. For diameter finishing blades established Back tape Pani This reduces friction with the workpiece during both forward and reverse rotation, thereby reducing the heat generated when the inner diameter finishing blade comes into contact with the workpiece. [Brief explanation of the drawing]

[0011] [Figure 1] This is a perspective view of the "More Tap 1" feature. [Figure 2] This is a front view of the raised tap 1. [Figure 3] This is a rear view of the raised tap 1. [Figure 4] This is a plan view (viewed from the tip side) of the raised tap 1. [Figure 5] This is a cross-sectional perspective view of the tip end of the raised tap 1. [Figure 6] Figure 5 shows the raised tap 1 as viewed from the tip side. [Figure 7] This is a cross-sectional view taken in the direction of line II shown in Figure 1. [Figure 8] This figure shows the state before rolling the pilot hole 90 with the build-up tap 1. [Figure 9] This diagram shows the state in which the build-up tap 1 has been inserted into the pilot hole 90. [Figure 10] This diagram shows the state after the raised tap 1 has been removed from the female thread. [Figure 11] This figure shows an inner diameter finishing blade 65 formed on the male thread portion 3 of a modified raised tap 100. [Figure 12]This is a photograph showing the shape of a conventional product and its results in the confirmation test. [Figure 13] This is a photograph showing the shape of the product of the present invention and its results in the confirmation test. [Figure 14] This is a diagram showing the cutting edge shape of the raised tap 101 which is a modified example. [Figure 15] This is a diagram showing the cutting edge shape of the raised tap 102 which is a modified example.

Embodiments for Carrying Out the Invention

[0012] An embodiment of the present invention will be described. In the following description, in the axial direction along the axis AX of the raised tap 1 shown in FIG. 1, the male thread portion 3 side is the tip side and the shank 2 side is the rear end side. For the sake of convenience in explanation, the directions of front (tip), rear (rear end), front (front), back (back), right, and left shown in the figure are used for the orientation of the raised tap 1. Also, for the sake of clarity in explanation, there are some places in the drawings that are shown with dimensional ratios different from the actual dimensional ratios, but the present invention is not construed as being limited to its shape thereby.

[0013] Referring to FIGS. 1 to 7, the configuration of the raised tap 1 will be described. The raised tap 1 shown in FIG. 1 is a tool for plastically deforming the surface layer of the pilot hole 90 (see FIG. 8) provided in the workpiece W to form an internal thread 40 (see FIGS. 9 and 10). When the raised tap 1 is viewed from the tip side, the raised tap 1 rotates counterclockwise about the axis AX (see the rotation direction T shown in FIGS. 1 and 4).

[0014] As shown in Figures 1 to 3, the shank tap 1 comprises a shank 2, a male thread portion 3, four oil grooves 4 (see Figure 4), and one groove 6. The shank 2 is cylindrical with an axis AX. The material of the shank 2 is, for example, high-speed tool steel. The shank 2 has a square portion 21 on its rear end. The square portion 21 has a substantially square cross-section. A tool holder (not shown) is attached to the square portion 21. The tool holder that supports the shank tap 1 is mounted on the spindle (not shown) of a machine tool and rotates integrally with the spindle. In the following description, "the shank tap 1 is mounted on the spindle" means the same thing as "the tool holder that holds the shank tap 1 is mounted on the spindle."

[0015] The male threaded portion 3 is provided coaxially (axis AX) with the shank 2 and is formed integrally with the shank 2. The male threaded portion 3 is substantially cylindrical in shape. The outer circumferential surface of the male threaded portion 3 is provided with threads 71 ​​and roots 72. The threads 71 ​​are formed along a winding wire with a substantially uniform height from the roots 72 and a predetermined lead angle.

[0016] The male thread portion 3 comprises a cutting portion 31 and a complete thread portion 32. The cutting portion 31 is located on the tip side of the male thread portion 3 and its diameter decreases towards the tip side along the axis AX. Therefore, the height of the threads 71 ​​of the cutting portion 31 from the axis AX is lower than the height of the threads 71 ​​of the complete thread portion 32 from the axis AX. The cutting portion 31 bites into the surface layer of the pilot hole 90 provided in the workpiece W and causes plastic deformation of the surface layer. The cutting portion 31 corresponds to several pitches (for example, 2 to 5 pitches) from the tip side of the male thread portion 3. Pitch is the distance between the centers of two adjacent threads 71 ​​in the axial direction (see distance P shown in Figures 1 and 2).

[0017] The complete thread section 32 is provided on the rear end side of the male thread section 3, and its diameter is approximately constant at the axis AX. The shape of the threads 71 ​​and roots 72 of the complete thread section 32 is approximately the same as the shape of the threads and roots of the female thread 40 to be roll-formed on the surface of the pilot hole 90 of the workpiece W (see Figure 10). During the rolling process, the complete thread section 32 finishes the surface of the female thread 40 and generates a driving force in the screwing direction.

[0018] As shown in Figures 4 and 6, five protrusions 51 to 55 are formed on the thread 71 of the male thread portion 3 in one cross-section. The protrusions 51 to 55 project radially outward and are provided along the winding wire. When the raised tap 1 is viewed from the tip side, the protrusions 51 to 55 are arranged sequentially at equal intervals of 60° in a clockwise direction within a range of approximately 240° (see θ in Figure 4) around the axis AX. Therefore, the protrusions 51 to 55 are adjacent to each other at one lead (one rotation) of the winding wire along a direction parallel to the axial direction.

[0019] The four oil grooves 4 are provided between protrusions 51 and 52, between protrusions 52 and 53, between protrusions 53 and 54, and between protrusions 54 and 55, respectively. The oil grooves 4 are formed in a straight line parallel to the axis AX from the tip side to the rear end side, spanning the complete crest 32 and the engagement portion 31 (see Figures 1 to 3). The cross-section of the oil grooves 4 is approximately U-shaped (see Figure 6). The oil grooves 4 supply cutting fluid to the rolling surface of the workpiece W. The cutting fluid enhances the lubrication effect, cooling effect, etc., during rolling.

[0020] In the male thread portion 3, the distance between adjacent projections 51 and 55 in the circumferential direction is 120° around the axis AX, which is wider than the distance between other pairs of adjacent projections in the circumferential direction (see Figures 4 and 6). A grinding surface 60 is provided between projections 51 and 55. The grinding surface 60 is the surface obtained by removing the threads between projections 51 and 55 by planar cutting, and extends parallel to the axial direction. The grinding surface 60 is perpendicular to the radial direction of the male thread portion 3. The diameter of the rotational trajectory of the cutting edge of the grinding surface 60 coincides with the inner diameter of the female thread 40 to be roll-formed.

[0021] As shown in Figures 1 and 3, a stepped portion 603 is provided on the grinding surface 60 at a position corresponding to the boundary between the cutting portion 31 and the complete peak portion 32. A first grinding surface 601 is formed on the cutting portion 31 side of the stepped portion 603, and a second grinding surface 602 is formed on the complete peak portion 32 side of the stepped portion 603. The stepped portion 603 connects the rear end of the first grinding surface 601 and the front end of the second grinding surface 602 in the radial direction. The height of the first grinding surface 601 is lower than the height of the second grinding surface 602. The height of the grinding surface 60 is the distance from the axis AX and is the diameter of the rotation trajectory. A groove 6 (an example of the "groove" of the present invention) is provided at a position adjacent to the protrusion 55 of the grinding surface 60. The groove 6 is formed in a straight line parallel to the axis AX from the tip to the rear end of the male thread portion 3, and has a roughly semicircular cross-sectional shape that is larger than the other oil grooves 4 (see Figure 6).

[0022] An inner diameter finishing blade 61 is formed on the ridge line of the grinding surface 60 with the groove 6. The ridge line of the grinding surface 60 with the groove 6 is also the open end opposite to the rotational direction T of the groove 6. Therefore, the inner diameter finishing blade 61 is oriented in the rotational direction T. The height of the inner diameter finishing blade 61 is the same as the height of the grinding surface 60. The height of the inner diameter finishing blade 61 is the radial distance from the axis AX. The inner diameter finishing blade 61 cuts away the crest portion of the threads of the female screw 40 that has been raised by plastic deformation caused by the protrusions 51-55, i.e., the incomplete shape of the crests that occur in the threads of the female screw 40, and finishes the inner diameter portion 41 of the female screw 40 (see Figure 10). The inner wall surface of the groove 6 functions as the "rake face" of the inner diameter finishing blade 61. The specific shape of the inner diameter finishing blade 61 will be described later.

[0023] As shown in Figures 5 to 7, an oil passage 7 is provided inside the raised tap 1. The oil passage 7 extends linearly along the axis AX and passes through the center of the rear end and the center of the front end of the raised tap 1 (see Figure 7). The oil passage 7 opens in a circular shape at the center of the front end of the raised tap 1 (see Figure 3). Cutting fluid is supplied to the oil passage 7 from the rear end side. The cutting fluid flows through the oil passage 7 toward the front end and is discharged from the opening at the front end toward the surface of the pilot hole 90.

[0024] The shape of the internal diameter finishing blade 61 will be specifically described with reference to Figures 3, 8, and 9. Figures 8 and 9 show a part of the cross-section along the axis AX of the male thread portion 3, indicating the height position of the internal diameter finishing blade 61 relative to the multiple threads 71 ​​in the protruding portion 55. The internal diameter finishing blade 61 extends in a substantially straight line in a front view from the tip side to the base side of the male thread portion 3 (see Figure 1). The internal diameter finishing blade 61 has a slight back taper. In this embodiment, the back taper means that the height from the axis AX decreases as it moves from the cutting portion 31 side to the complete thread portion 32 side, so that the internal diameter finishing blade 61 has substantially the same diameter from the cutting portion 31 side to the complete thread portion 32 side. Therefore, the contact area of ​​the internal diameter finishing blade 61 with the internal diameter portion 41 of the female thread 40 that is roll-formed on the surface of the pilot hole 90 can be reduced. In Figures 9 and 10, the height position Q shown by the dotted line indicates the height of the internal diameter portion 41 of the female thread 40. The inner diameter finishing blade 61 becomes lower relative to the height position Q as it approaches the complete thread portion 32. Therefore, friction due to contact between the inner diameter finishing blade 61 and the inner diameter portion 41 of the female thread 40 can be reduced during forward and reverse rotation of the grooving tap 1.

[0025] As shown in Figures 3 and 8, the inner diameter finishing blade 61 is a two-stage cutting edge, corresponding to the stepped shape of the grinding surface 60. The inner diameter finishing blade 61 comprises a first-stage finishing blade 611, a second-stage finishing blade 612, and a stepped portion 613. The first-stage finishing blade 611 is formed on the ridge line with the groove 6 of the first grinding surface 601 and corresponds to the engagement portion 31. The axial length of the first-stage finishing blade 611 is approximately the same as the axial length of the engagement portion 31. The second-stage finishing blade 612 is formed on the ridge line with the groove 6 of the second grinding surface 602 and corresponds to the complete peak portion 32. The stepped portion 613 is formed on the ridge line with the groove 6 of the stepped portion 603 and corresponds to the boundary between the engagement portion 31 and the complete peak portion 32.

[0026] Here, as shown in Figure 9, the height of the first finishing blade 611 is set lower than the height of the tip 615 of the complete thread portion 32. The tip 615 of the second finishing blade 612 is positioned corresponding to the portion on the cutting side 31 from the apex 711 of the most advanced thread 71A in the complete thread portion 32. The height of the tip 615 of the second finishing blade 612 is set to a position corresponding to the inner diameter of the female thread 40 to be roll-formed (see height position Q in Figure 9). The stepped portion 613 connects the rear end of the first finishing blade 611 and the tip 615 of the second finishing blade 612 in the radial direction. The second finishing blade 612 gradually becomes lower from the stepped portion 613 toward the rear end of the male thread portion 3 due to a back taper.

[0027] Referring to Figures 8 to 10, the method of forming a female thread 40 using a build-up tap 1 will be explained. As shown in Figure 8, a pilot hole 90 is formed in advance in the workpiece W. The build-up tap 1 is mounted on the spindle (not shown) of a machine tool and positioned in a preparation position in front of the pilot hole 90 by the movement of the spindle. The machine tool starts the forward rotation of the build-up tap 1 together with the spindle and is inserted into the pilot hole 90 from the preparation position. As shown in Figure 9, the engagement portion 31 of the build-up tap 1 screws into the surface of the pilot hole 90 in the workpiece W. Plastic deformation of the surface begins, and the complete crest portion 32 screws further inward following the engagement portion 31. As the plastic deformation progresses, a female thread 40 is formed on the surface. Excess material 34 is pushed out in the circumferential direction from the crest of the female thread 40 formed on the surface. Subsequently, the excess material 34 is cut and removed by the passage of the internal diameter finishing blade 61. Therefore, the build-up tap 1 can roll-form a female thread 40 with high internal diameter accuracy. After the female thread 40 is formed, the machine tool stops rotating the spool tap 1.

[0028] Next, in order to remove the rake tap 1 from the female thread 40, the machine tool, along with the spindle, begins to reverse the rotation of the rake tap 1. The rake tap 1 moves toward the preparation position while reversing. As described above, the inner diameter finishing blade 61 has a back taper, but the first finishing blade 611 of the inner diameter finishing blade 611 is located lower than the tip 615 of the second finishing blade 612. Therefore, in the process of the rake tap 1 reversing and returning to the preparation position, the first grinding surface 601 corresponding to the first finishing blade 611 does not interfere with the inner diameter portion 41 of the female thread 40. The first grinding surface 601 is the part of the first finishing blade 611 that is opposite to the rake face (inner wall surface of the groove 6). The machine tool stops the spindle at the preparation position and stops the rotation of the rake tap 1 (see Figure 10). Therefore, when the ridge tap 1 is removed in reverse from the female thread 40 formed in the workpiece W, the inner diameter finishing blade 61 does not interfere with the inner diameter portion 41 of the female thread 40 from the opposite direction to the rake face, thus reducing the collapse of the inner diameter portion 41.

[0029] Referring to Figure 11, a modified example of the raised tap 1 will be described. The inner diameter finishing blade 61 of the raised tap 1 is a two-stage cutting blade in which the portion corresponding to the boundary between the cutting portion 31 and the complete thread portion 32 has a stepped shape. The inner diameter finishing blade is not limited to a stepped shape as long as the height of the inner diameter finishing blade in the portion corresponding to the cutting portion 31 is lower than the height of the inner diameter finishing blade formed in the portion corresponding to the leading edge of the thread in the complete thread portion 32.

[0030] For example, the raised tap 100 shown in Figure 11 is a modified version of the raised tap 1, and is equipped with an inner diameter finishing blade 65 instead of an inner diameter finishing blade 61. The inner diameter finishing blade 65 has a substantially inverted V shape with the boundary between the cutting portion 31 and the complete crest portion 32 as its apex. Although not described in detail here, the grinding surface forming the inner diameter finishing blade 65 is formed in a substantially inverted V shape in cross-section, corresponding to the shape of the inner diameter finishing blade 65.

[0031] The internal diameter finishing blade 65 comprises a first-stage finishing blade 651, a second-stage finishing blade 652, and a top section 653. The first-stage finishing blade 651 corresponds to the cutting portion 31. The second-stage finishing blade 652 corresponds to the complete crest portion 32. The top section 653 corresponds to the boundary between the cutting portion 31 and the complete crest portion 32. The height position of the top section 653 is set to the position corresponding to the internal diameter portion 41 of the female thread 40 to be roll-formed (see height position Q in Figure 11). The first-stage finishing blade 651 is inclined to become lower from the top section 653 toward the tip side of the male thread portion 3. The second-stage finishing blade 652 has the same back taper as the internal diameter finishing blade 61. Therefore, the second-stage finishing blade 652 is inclined to become lower from the top section 653 toward the rear end side of the male thread portion 3. The first-stage finishing blade 651 may also have the same back taper.

[0032] In this internal diameter finishing blade 65, as with the internal diameter finishing blade 61 of this embodiment, the first-stage finishing blade 651 corresponding to the cutting portion 31 is located lower than the tip of the second-stage finishing blade 652, i.e., the top portion 653. Therefore, even when the sculpting tap 100 is reversed and withdrawn from the female thread 40, the grinding surface (not shown) corresponding to the first-stage finishing blade 651 does not interfere with the internal diameter portion 41 of the female thread 40. Consequently, as with the sculpting tap 1, when the sculpting tap 100 is reversed and withdrawn from the female thread 40 formed in the workpiece W, the internal diameter finishing blade 65 does not interfere with the internal diameter portion 41 of the female thread 40 from the opposite direction to the rake face, thus reducing the collapse of the internal diameter portion 41.

[0033] Next, a verification test was conducted to confirm the effectiveness of the present invention. In this verification test, a female thread was roll-formed using the present invention in a pre-formed pilot hole in a workpiece, and the quality of the female thread after roll-forming was compared with that of a conventional product. As an example of the present invention, a raised tap 100 shown in Figure 11 was used. Conventional raised taps only have a back taper applied to a straight inner diameter finishing blade 161.

[0034] The processing environment is as follows: • Workpiece: ADC12 (10mm thick) • Screw size; M14x1 • Machine tools: Vertical machining centers • Cutting fluid: Water-soluble cutting fluid (emulsion, dilution ratio 10x, internal lubrication at 3MPa) • Tool holder: Milling chuck • Pilot hole: φ13.4mm (drill), actual measurement = 13.395mm Effective thread length: 10mm (through) ·Cutting speed: 44m / min(1000min-1)

[0035] The results for the conventional product will be explained. Figure 12(A) is a photograph of a part of the tip side of the conventional product. The inner diameter finishing blade 161 has a back taper that decreases in height from the cutting portion 31 side toward the complete crest portion 32 side (see the direction of the arrow in Figure 12(A)). Figure 12(B) is a magnified photograph of the female thread formed by rolling in the conventional product. The build-up tap is removed from the roll-formed female thread in the direction of arrow K shown in Figure 12(B). The circled area in Figure 12(B) is the part that contacted the inner diameter finishing blade 161 from the opposite side of the rake face when the build-up tap was reversed. Figure 12(C) is a magnified view of the circled area in Figure 12(B). As shown by the arrow in Figure 12(C), it can be seen that the crest portion of the female thread is crushed.

[0036] The results of the present invention will now be explained. Figure 13(A) is a photograph of a part of the tip side of the present invention. The first finishing blade 651 of the inner diameter finishing blade 65 slopes downward from the top 653 toward the tip, and the second finishing blade 652 slopes downward from the top 653 toward the rear end. Figure 13(B) is a magnified photograph of the female thread formed by rolling with the present invention. As can be seen in comparison with the conventional product, the circled part in Figure 13(B) is not crushed. This is because when the raising tap 100 was reversed, the part of the first finishing blade 651 opposite to the rake face did not interfere with the inner diameter part of the rolled female thread. From these results, it has been demonstrated that, compared to the conventional product, the collapse of the threads of the formed female thread can be reduced when the raising tap 100 is removed from the female thread after rolling.

[0037] As described above, the thread-forming tap 1 of this embodiment is a tool that forms an internal thread by plastically deforming the pilot hole 90 of the workpiece W. The thread-forming tap 1 comprises a male thread portion 3, a groove 6, and an internal diameter finishing blade 61. The male thread portion 3 comprises a complete crest portion 32 and a cutting portion 31. The cutting portion 31 is provided continuously with the complete crest portion 32 and becomes smaller in diameter towards the tip. The groove 6 is provided parallel to the axis, straddling the complete crest portion 32 and the cutting portion 31 so as to divide the thread 71 of the male thread portion 3.

[0038] The internal finishing blade 61 is provided along the opening end of the groove 6 opposite to the rotation direction T of the reinforcing tap 1, in the engagement portion 31 and the complete thread portion 32. The internal finishing blade 61 cuts off the top portion of the threads of the female screw formed on the surface of the pilot hole 90. When the height is taken from the axis AX of the reinforcing tap 1, the height of the first finishing blade 611 of the internal finishing blade 61 in the engagement portion 31 is lower than the height of the second finishing blade 612 of the internal finishing blade 61 formed in the portion corresponding to the leading edge thread 71 in the complete thread portion 32. As a result, when the reinforcing tap 1 is removed from the workpiece during reverse rotation, the internal finishing blade 61 in the engagement portion 31 does not interfere with the threads of the female screw formed. Therefore, the reinforcing tap 1 can reduce the collapse of the threads of the female screw formed in the pilot hole 90.

[0039] In the internal diameter finishing blade 61, a stepped portion 613 is provided between the cutting portion 31 and the leading edge thread 71 of the complete thread portion 32. In the stepped portion 613, the height on the cutting portion 31 side is lower than the height on the complete thread portion 32 side. Therefore, the raised tap 1 can make the height of the internal diameter finishing blade 61 on the cutting portion 31 lower than the height of the internal diameter finishing blade 61 formed on the leading edge thread 71 of the complete thread portion 32.

[0040] The internal finishing blade 61 is provided with a back taper, at least from the portion corresponding to the leading edge thread 71 in the complete thread section 32 toward the rear end, with the height decreasing accordingly. Therefore, the raised tap 1 can reduce friction with the workpiece during forward and reverse rotation. This reduces the heat generated by the internal finishing blade 61 contacting the workpiece.

[0041] The present invention is not limited to the above embodiments, and various modifications are possible. The material of the shank 2 of the build-up tap 1 may be a material other than high-speed tool steel, for example, cemented carbide. The inner diameter finishing blade 61 has a back taper on all parts, but it may be applied only to the second-stage finishing blade 612. Also, the inner diameter finishing blade 61 does not need to have a back taper. The oil grooves 4 are not limited to four, and may be more or fewer. The oil grooves 4 and oil passages 7 may be omitted. The build-up tap 1 is a left-rotating tool that rotates counterclockwise when viewed from the tip side, but it may also be a right-rotating tool that rotates clockwise.

[0042] The raised tap 1 has one internal diameter finishing blade 61, but it may have two or more. For example, the raised tap 101 shown in Figure 14 has four protrusions 15, two oil grooves 14, two grooves 16, and two internal diameter finishing blades 161 on the male thread portion, and has a point-symmetric shape around the axis AX. The raised tap 102 shown in Figure 15 has three protrusions 15, three grooves 16, and three internal diameter finishing blades 161. Even with these modified structures, the same effects as the above embodiment can be obtained.

[0043] As shown in Figure 8, in the axial direction, the stepped portion 613 is located on the side of the gripping portion 31 to the boundary between the gripping portion 31 and the complete peak portion 32, but it may also be located at the same position as the boundary between the gripping portion 31 and the complete peak portion 32. [Explanation of symbols]

[0044] 1. Booster Tap 3 Male threaded section 6 grooves 31. Food portion 32 Complete Mountain Club 61 Inner diameter finishing blade 65 Inner diameter finishing blade 71 threads 100 Booster Tap 611 First-stage finishing blade 612 Second-stage finishing blade 613 Stepped section 651 First-stage finishing blade 652 Second level official blade AX axis

Claims

1. In a build-up tap that forms an internal thread by plastically deforming a pilot hole in a workpiece, A male thread having a complete thread section and a cutting section that is provided continuously with the complete thread section and whose diameter decreases towards the tip, A groove is provided parallel to the axis, spanning the complete thread portion and the engagement portion, so as to divide the threads of the male thread portion, In the aforementioned cutting portion and the complete thread portion, an internal diameter finishing blade is provided along the open end of the groove opposite to the rotation direction of the raised tap, which cuts off the top portion of the thread of the female screw. Equipped with, In the aforementioned internal diameter finishing blade, when the distance from the axis of the raised tap is defined as the height of the internal diameter finishing blade, the height of the cutting portion is lower than the height of the portion corresponding to the leading edge of the thread in the complete thread portion. Between the cutting portion and the leading edge of the complete thread portion, a stepped portion is provided where the height of the cutting portion is lower than the height of the complete thread portion. thing A tap featuring a raised design.

2. A build-up tap that forms an internal thread by plastically deforming a pilot hole in a workpiece, A male thread having a complete thread section and a cutting section that is provided continuously with the complete thread section and whose diameter decreases towards the tip, A groove is provided parallel to the axis, spanning the complete thread portion and the engagement portion, so as to divide the threads of the male thread portion, In the aforementioned cutting portion and the complete thread portion, an internal diameter finishing blade is provided along the open end of the groove opposite to the rotation direction of the raised tap, which cuts off the top portion of the thread of the female screw. Equipped with, In the aforementioned internal diameter finishing blade, when the distance from the axis of the raised tap is defined as the height of the internal diameter finishing blade, the height of the cutting portion is lower than the height of the portion corresponding to the leading edge of the thread in the complete thread portion. The inner diameter finishing blade is provided with a back taper, at least, such that the height decreases from the portion corresponding to the leading edge of the thread in the complete thread portion toward the rear end. A tap featuring a raised design.

Images