tap tool

Abstract

A tap tool (10) has a shank (12) having a central axis (Om), and a blade (14) combined to one end of the shank, the blade having a thread portion (16) engaged with a bottom hole (H) formed in a workpiece (W), and a non-engagement portion (18) not engaged with the bottom hole, the thread portion having a full thread portion (22) on a base end side, and an incomplete thread portion (20) continuously formed on a distal end side of the full thread portion, the incomplete thread portion having a cutting edge (16a) machining the bottom hole, and a guide pad portion (16b) located behind the cutting edge in a rotation direction, an outer peripheral surface of the guide pad portion being formed by a cylindrical surface having a radius of the cutting edge with respect to the central axis.

Description

Technical Field

[0001] This invention relates to a tap tool for machining a bottom hole in a workpiece into a threaded hole. Background Technology

[0002] When tapping is performed using a machining center and a tap tool mounted on that machining center, it is called synchronous tapping, where rotation and linear feed are synchronized. In synchronous tapping, rotation and feed must also be synchronized when the tap tool is withdrawn from the machined threaded hole. Therefore, the time required to withdraw the tap tool needs to be approximately equal to the time required for the tap tool to advance and machine the thread groove.

[0003] Patent Document 1 describes a tap tool comprising: a threaded portion having a cutting edge having a threaded groove for machining a threaded hole; a pad portion engaging with the threaded groove machined by the cutting edge; and a non-engaging portion forming a space between the non-engaging portion and the threaded hole in a cross-sectional view in which the axis of rotation is aligned with the central axis of the threaded hole.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2020-168698 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] In the tap tool of Patent Document 1, since a space is formed between the non-engaging part and the threaded hole, after the threading is completed, the tap tool can be moved in the threaded hole in a direction orthogonal to the rotation axis from a state where the rotation axis is aligned with the central axis of the threaded hole, so as to simultaneously disengage the engagement between the threaded part and the thread groove and the engagement between the pad part and the thread groove, and pull the tap tool out of the threaded hole axially.

[0009] In the tap tool of Patent Document 1, when the cutting edge of the guide cutting part at the end of the tap tool initially cuts in, the guide cutting part cannot be adequately supported at the entrance of the bottom hole, resulting in tap tool deflection deformation such as bending or tilting. Furthermore, the tap tool of Patent Document 1, because it has a back angle on the cutting edge, is particularly prone to deformation such as bending or tilting during initial cutting.

[0010] This invention is an improvement upon the applicant's prior application, namely Patent Document 1, and its purpose is to solve the problems of this prior art. Specifically, its purpose is to provide a tap tool that, after machining, can be moved within the threaded hole in a direction orthogonal to the axis of rotation, and then the tap tool can be pulled out axially from the threaded hole, wherein when the cutting edge of the guide cutting part at the end of the tap tool cuts into the workpiece, no deformation such as deflection or tilting occurs.

[0011] Methods for solving problems

[0012] To achieve the above objectives, according to the present invention, a tap tool is provided for machining a bottom hole formed in a workpiece into a threaded hole. The tap tool comprises: a shank having a central axis, and a cutter body coupled to one end of the shank. The cutter body has a threaded portion that engages with the bottom hole formed in the workpiece, and a non-engaging portion that does not engage with the bottom hole. The threaded portion has a complete threaded portion at its base end and an incomplete threaded portion continuously formed at its end end. The incomplete threaded portion has a cutting edge for machining the bottom hole and a guide pad located behind the cutting edge in the direction of rotation. The outer peripheral surface of the guide pad is formed by a cylindrical surface parallel to the central axis and has a radius equal to the distance from the central axis to the cutting edge.

[0013] Invention Effects

[0014] According to the present invention, since the outer peripheral surface of the guide pad portion of the incomplete thread portion is formed by a cylindrical surface parallel to the central axis and having a radius equal to the distance from the central axis to the cutting edge, the outer peripheral surface of the guide pad portion bears cutting resistance during machining, especially when the incomplete thread portion of the tap tool begins to engage with the bottom hole of the workpiece (when the cutting edge is inserted), thus preventing the tap tool from deflecting. Attached Figure Description

[0015] Figure 1 This is a schematic diagram illustrating an example of a machine tool used for tapping with the tap tool of the present invention.

[0016] Figure 2 This is a front view of a tapping tool according to an embodiment of the present invention.

[0017] Figure 3 yes Figure 2 A side view of a tapping tool.

[0018] Figure 4 yes Figure 2 A view of the end face of the tap tool.

[0019] Figure 5 yes Figure 2 A 3D view of a tapping tool.

[0020] Figure 6 It means Figure 2 A partially enlarged sectional view of the incomplete threaded portion of a tap tool.

[0021] Figure 7 It is a partially enlarged sectional view showing the incomplete threaded portion of a tap tool in the prior art.

[0022] Figure 8 It is a cross-sectional view of the tap tool and the threaded hole it produces.

[0023] Figure 9 It represents the cutting resistance and its principal and back components. Figure 8 The same cross-sectional view.

[0024] Figure 10 It means from Figure 8 The state of the tap tool after it has been displaced is shown in the cross-sectional view of the tap tool and the threaded hole.

[0025] Figure 11 This is a front view of a tap tool with grooves. Detailed Implementation

[0026] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

[0027] Reference Figure 1 An example is shown of a machine tool 100 to which the tapping tool and tapping method of the present invention are applicable. Figure 1 In this machine tool 100, a bed 102 serves as a base fixed to the factory floor. On the upper surface of the bed 102, along the horizontal front-to-back direction or the Y-axis direction (… Figure 1 A Y-axis guide rail 118 extends from the center (in the left-right direction), and the worktable 104 is configured to reciprocate along the Y-axis guide rail 118. The workpiece W is fixed to the worktable 104 by a fixture. As a Y-axis drive device that reciprocates the worktable 104 along the Y-axis direction, the machine tool 100 includes a Y-axis servo motor (not shown). Additionally, the machine tool 100 includes a Y-axis digital scale (not shown) for detecting the Y-axis coordinates of the worktable 104.

[0028] A column 108 is erected on the upper surface of the rear end side of the bed 102. In front of the column 108, along the horizontal left-right direction or the X-axis direction (… Figure 1An X-axis guide rail 120 extends from the center (perpendicular to the plane of the paper), and an X-axis slider 110 is configured to reciprocate along the X-axis guide rail 120. As an X-axis drive device for reciprocating the X-axis slider 110 along the X-axis direction, the machine tool 100 includes an X-axis servo motor (not shown). Additionally, the machine tool 100 includes an X-axis digital scale (not shown) for detecting the X-axis coordinates of the X-axis slider 110.

[0029] A Z-axis guide rail 122 is provided in front of the X-axis slider 110, extending in the vertical or Z-axis direction, and the spindle head 112 is arranged to reciprocate along the Z-axis guide rail 122. As a Z-axis drive device that reciprocates the spindle head 112 along the Z-axis direction, the machine tool 100 includes a Z-axis servo motor (not shown). Additionally, the machine tool 100 includes a Z-axis digital scale (not shown) for detecting the Z-axis coordinates of the spindle head 112.

[0030] A spindle head 116 is mounted on the spindle box 112, supporting the spindle 114 in a manner that allows it to rotate around a vertical axis of rotation Om. At the end of the spindle 114, a rotary tool T, such as an end mill, face mill, or drill bit, can be mounted, particularly a tap tool 10 described later. The spindle head 116 has a spindle servo motor 124 that drives the spindle 114 to rotate around the axis of rotation Om. The machine tool 100 includes a rotational position detection device that detects the rotational position of the spindle 114 about the axis of rotation Om. The rotational position detection device can be, for example, a rotary encoder 126 mounted on the spindle servo motor 124.

[0031] The machine tool 100 can further be configured as a machining center, which includes: a tool magazine (not shown) for storing multiple tools used in machining, an automatic tool changer (not shown) for exchanging tools between the tool magazine and the spindle 114, and a coolant supply device (not shown) for supplying coolant to the machining area of ​​the machine tool 100. These peripheral devices are housed together with the machine tool 100 in a housing (not shown).

[0032] The machine tool 100 also includes a control device 130 for controlling the machine tool 100. The control device 130 may consist of a computer and related software, the computer including: a CPU (Central Processing Unit); a memory device such as RAM (Random Access Memory) or ROM (Read Only Memory); a storage device such as HDD (Hard Disk Drive) or SSD (Solid State Drive); input / output ports; and a bidirectional bus connecting them to each other. In particular, the control device 130 may be formed as an NC control device that controls the X-axis servo motor, Y-axis servo motor, Z-axis servo motor, and spindle servo motor 124.

[0033] The machine tool 100 controls the X-axis servo motor, Y-axis servo motor, Z-axis servo motor, and spindle servo motor 124 according to the machining program provided to the control device 130, so that the rotary tool T mounted at the end of the spindle moves relative to the workpiece W fixed on the worktable 104 along the three orthogonal X, Y, and Z axes to process the workpiece W.

[0034] The machine tool 100 synchronizes the rotation of the spindle 114 with the feed in the Z-axis direction to perform tapping. In this specification, the linear movement in the Z-axis direction for tapping the tap tool 10 is called forward movement, and the linear movement in the Z-axis direction for pulling the tap tool 10 out of the threaded hole 6 is called backward movement.

[0035] The tap tool 10 performs tapping operations, i.e., it performs the machining of the bottom hole H into a threaded hole 6, with its central axis Ot aligned with the central axis Oh of the bottom hole H formed in the workpiece W. Figures 8-10 In the attached drawing, reference numeral 8 indicates the inner circumference of the threaded hole 6, which coincides with the bottom hole H. Additionally, reference numeral 6 indicates the thread root of the threaded hole 6 corresponding to the nominal diameter of the tap tool 10. The tap tool 10 rotates in the direction of arrow A.

[0036] The tap tool 10 has a rod-shaped shank 12 extending along a central axis Ot, and a cutting body 14 attached to the end of the shank 12. The shank 12 is configured to be mounted on the end of a spindle 114. The shank 12 may be configured to be directly mounted in a mounting hole (not shown) formed in the end of the spindle 114. Alternatively, the tap tool 10 may mount the shank 12 in a mountable manner to a tool holder (not shown) or a tool chuck (not shown), and mount it to the end of the spindle 114 via the tool holder or tool chuck.

[0037] The cutter body 14 is formed asymmetrically with respect to the central axis Ot, and has: an externally threaded portion 16 that engages with the inner circumferential surface of the pre-formed bottom hole H in the workpiece W to machine a thread groove; and a non-engaging portion 18 that does not engage with the inner circumferential surface of the bottom hole H. The threaded portion 16 has a plurality of thread teeth 24, 26, 28, 30 (see reference) arranged at predetermined thread pitch intervals in the length direction. Figure 6 , 7 Furthermore, in this embodiment, the tap tool 10 is a tap tool that forms a thread groove with a triangular thread.

[0038] Reference Figure 8 , 9 Each thread of the threaded portion 16 has: a cutting edge 16a formed at the end of the tap tool 10 in the rotational direction; and a guide pad portion 16b that extends behind the cutting edge 16a in the rotational direction. The guide pad portion 16b in Figures 8-10 The portion extending from the cutting edge 16a to the rear end 16d has an outer peripheral surface 16c. In this embodiment, the outer peripheral surface 16c is formed from a portion of a cylindrical surface having a radius equal to that of the cutting edge 16a (the distance between the central axis Ot and the cutting edge 16a). That is, in this embodiment, the threaded portion 16 does not have a clearance angle on the cutting edge 16a, and in this embodiment, the tangent at the cutting edge 16a coincides with the tangent at the cutting edge 16a relative to the circumference depicted by the cutting edge 16a.

[0039] The threaded portion 16 includes: an incomplete threaded portion 20 formed as an introductory cutting portion at the end; and a complete threaded portion 22 on the base end side. In this embodiment, the incomplete threaded portion 20 has three thread teeth 24, 26, and 28. The complete threaded portion 22 has multiple thread teeth 30. (Refer to...) Figure 6 The three threads 24, 26, and 28 of the incomplete thread portion 20 are arranged at a predetermined thread pitch along the axial direction of the tap tool 10, and have outer peripheral surfaces 24a, 26a, and 28a, and tooth flanks 24b, 26b, and 28b. The tooth flanks 24b, 26b, and 28b are arranged approximately symmetrically on both sides of the outer peripheral surfaces 24a, 26a, and 28a in the axial direction.

[0040] In this embodiment, the outer peripheral surfaces 24a, 26a, and 28a are each formed from a portion of a cylindrical surface, and are parallel to the central axis Ot. The outer peripheral surface 28a on the end side of the tap tool 10 has the smallest radius, thus having the widest axial width. Conversely, the outer peripheral surface 24a on the base side has the largest radius, thus having the narrowest axial width. Thus, for the incomplete thread portion 20, when viewed in cross-section along its length, or when the incomplete thread portion 20 is projected onto a plane, the outer peripheral surfaces 24a, 26a, and 28a are formed in a stepped shape from the end side outer peripheral surface 24a to the base side outer peripheral surface 28a.

[0041] In contrast, in existing tap tools, such as Figure 7As shown, an incomplete threaded portion 50 forming the cutting section has three threaded teeth 52, 54, and 56 arranged axially at predetermined thread pitch intervals, and has outer peripheral surfaces 52a, 54a, and 56a, and tooth flanks 52b, 52c; 54b, 54c; 56b, and 56c. The outer peripheral surfaces 52a, 54a, and 56a are arranged within a common conical surface, thus the incomplete threaded portion 50 is formed as a tapered shape that tapers towards the end. Therefore, among each threaded tooth 52, 54, and 56, the tooth flanks 52b, 54b, and 56b on the base end side become wider than the tooth flanks 52c, 54c, and 56c on the end end side. During machining, the tooth flanks 52b, 54b, and 56b on the base end side experience a greater machining load than the tooth flanks 52c, 54c, and 56c on the end end side.

[0042] Because the flank faces of the base and end sides of the thread in the incomplete thread portion forming the cutting section are different in size, in existing tap tools, the tap tool tilts and flexes during machining. In contrast, in this embodiment, the flank faces 24b, 26b, and 28b are arranged approximately symmetrically on both sides of the outer peripheral surfaces 24a, 26a, and 28a in the axial direction. Therefore, during machining, especially when the incomplete thread portion 20 of the tap tool 10 begins to engage with the bottom hole H of the workpiece W, tilting and flexing of the tap tool 10 are prevented.

[0043] The complete threaded portion 22 has a plurality of thread teeth 30, specifically seven in this embodiment. Each thread tooth 30 has a tooth flank 30b and an outer peripheral surface 30a, with the tooth flank 30b symmetrically arranged on both sides of the outer peripheral surface 30a in the axial direction. The complete threaded portion 22 has a shape consistent with the root shape of the machined internal thread.

[0044] The non-engaging portion 18 has a smooth curved surface, for example, it can be formed from a portion of a cylindrical surface with a radius smaller than that of the shank 12. A space 4 is formed between the non-engaging portion 18 and the inner circumferential surface 8 of the threaded hole 6 machined in the workpiece W. The space 4 has the following size: when the tap tool 10 is used... Figure 8 , 9 As shown, starting from the position coinciding with the central axis Oh of the threaded hole 6 on the workpiece W, as... Figure 10 When the arrow S indicates that the threaded portion 16 has moved (displaced) in a direction orthogonal to the axis of rotation Om, the engagement between the threaded portion 16 and the internal thread machined on the workpiece W is disengaged; that is, the thread teeth 24, 26, 28, and 30 of the threaded portion 16 can be completely separated from the inner circumferential surface 8 of the internal thread of the workpiece W. Figure 10 In the diagram, arrow S becomes a vector representing the direction and amount of movement of the main axis 114.

[0045] The size of space 4 is preferably made slightly larger to allow for a safety margin. In addition, during the cutting process, space 4 serves as a path for supplying cutting fluid to the cutting edge 16a and for discharging chips generated by cutting, which improves the quality of the machined surface and extends tool life.

[0046] like Figure 10 As shown, when the engagement between the threaded portion 16 and the threaded groove of the workpiece W is released by displacing the spindle 114, the tap tool 10 can move backward along the rotation axis Om (in Figure 1 The tap tool 10 is pulled out of the threaded hole 6 by moving upward along the Z-axis. Since the extraction of this tap tool 10 does not involve rotational motion as in the past, it can be performed at high speed.

[0047] In the following explanation, Figure 8 The 3 o'clock position is taken as the origin (position where the rotation angle θ = 0°) of the main axis 114 about the rotation axis Om. Figure 8 In this diagram, the rotation angle (hereinafter referred to as the "phase angle") of the tap tool 10 is exemplified as 180 degrees, representing the phase angle of the cutting edge 16a. The phase angle of the tap tool 10 at rest after machining varies for each threaded hole 6 because the number of rotations required for machining differs depending on the depth of the threaded hole 6. Therefore, the direction of the displacement S of the tap tool 10 also differs for each threaded hole 6.

[0048] In order to determine the direction of spindle 114 displacement, in this embodiment, when the tap tool 10 is positioned at the machining start point (not shown), the spindle 114 is set at a predetermined phase angle. Furthermore, when the spindle is stationary after machining, the control device 130 calculates the phase angle of the tap tool 10 based on information from the rotary encoder 126 of the spindle servo motor 124. Based on the calculated phase angle of the tap tool 10, the control device 130 calculates the direction of spindle 114 displacement (angle θ in FIG. 0). On the other hand, since the required displacement amount is determined according to the cross-sectional shape of the tap tool 10, it can be pre-stored in the control device 130.

[0049] The following describes the tap tool 10 and the method of using embodiments of the present invention. Figure 1 An example of tapping operation performed by the vertical machine tool 100 shown will be explained.

[0050] First, after mounting the tap tool 10 on the spindle 114, position it at the machining start point. That is, align the rotation axis Om of the spindle 114 of the machine tool with the tap tool 10 mounted thereon with the center axis Oh of the bottom hole H on the workpiece, and position the end of the tap tool 10 at the machining start point at a specified height in the Z-axis direction. At this time, rotate the spindle 114 to feed a specified phase angle with the cutting edge 16a positioned in a specified rotational position.

[0051] Next, the rotational speed of the spindle 114 and the feed speed in the Z-axis direction are synchronized according to the thread pitch to perform synchronous tapping. When the tap tool 10 moves a specified distance along the Z-axis direction to reach the commanded thread depth, the rotation of the spindle 114 and the feed in the Z-axis direction stop. Thus, the bottom hole H of the workpiece is machined into a threaded hole 6.

[0052] Next, the tap tool 10 is moved along a direction orthogonal to the rotation axis Om. The direction of this movement of the tap tool 10 (in...) Figure 10 The direction indicated by arrow S is calculated based on the phase angle (rotational position of cutting edge 16a) of tap tool 10, which is calculated based on information from the rotary encoder 126 of spindle servo motor 124. The displacement amount uses a value pre-recorded in control device 130. Through this process, the engagement between the threaded portion 16 of tap tool 10 and the thread groove of threaded hole 6 is completely disengaged.

[0053] Next, without rotating the tap tool 10, it is moved upwards and backwards to the machining start point. At this time, the feed rate of the spindle 114 in the Z-axis direction can be set to more than twice the feed rate during machining, i.e., during forward movement. In this way, the tapping of one threaded hole 6 is completed.

[0054] According to this embodiment, a space 4 is formed between the non-engaging portion 18 of the tap tool 10 and the inner diameter of the threaded hole 6. This space 4 has a size such that when the tap tool 10 moves in a direction orthogonal to the rotation axis Om, the engagement between the threaded portion 16 and the thread groove is released. Therefore, after machining, the tap tool 10, having released its engagement with the thread groove of the threaded hole 6, can be pulled out of the threaded hole 6 at high speed along the rotation axis direction without rotating.

[0055] Additionally, refer to Figure 9During the tapping process, the cutting resistance Rc, its back component Rb, and its main component Rp, which act as a reaction force relative to the cutting force on the cutting edge 16a of the tap tool 10, are represented by a vector. Since the main component Rp is greater than the back component Rb, the cutting resistance Rc, as their resultant force, acts toward the guide pad 16b behind the cutting edge 16a in the direction of rotation. The outer peripheral surface of each thread tooth of the guide pad 16b is formed by a cylindrical surface parallel to the center line Ot and has a radius equal to the distance from the center line Ot to the cutting edge 16a. Therefore, the cutting resistance Rc is first supported by contact with the workpiece W through the cylindrical surface of the outer periphery of the guide pad 16b. Thus, according to this embodiment, since the outer peripheral surface 16c of the guide pad portion 16b is formed by a portion of a cylindrical surface having a radius equal to that of the cutting edge 16a, the cutting resistance Rc is supported by the surface of the threaded hole 6, particularly the thread groove (tooth root) formed on the workpiece W, via the outer peripheral surface 16c of the guide pad portion 16b. Therefore, the tap tool 10 will not tilt or bend due to the cutting resistance Rc, and as a result, the machining accuracy is the same as when using conventional tap tools.

[0056] Although it is stated that the radius of the outer peripheral surface 16c of the guide pad 16b is equal to the radius of the cutting edge 16a, "equal" does not mean completely identical in a strict sense. In the invention of this application, "equal radii" includes the same radius, or a radius from a decimal of μm to tens of μm. That is, "equal radii" includes "approximately equal radii". For example, "equal radii" may also include machining errors within a corresponding range.

[0057] Furthermore, in order to lubricate the surface between the outer peripheral surface 16c of the guide pad 16b and the surface of the thread groove (tooth root) formed on the workpiece W using coolant, or to prevent excessive increase in cutting resistance Rc, the radius of the outer peripheral surface 16c of the guide pad 16b can be smaller than the radius of the cutting edge 16a within a range that allows the guide pad 16b to support the cutting resistance Rc and prevent the tap tool 10 from deflecting, thereby forming a gap between the outer peripheral surface 16c of the guide pad 16b and the workpiece W. This gap can be, for example, 100 μm or less, preferably tens of μm or less, and more preferably 50 μm or less.

[0058] Alternatively, the radius of the outer peripheral surface 16c of the guide pad portion 16b can be gradually reduced in the circumferential direction from the cutting edge 16b toward the rear end 16d, forming a gap between the outer peripheral surface 16c and the workpiece W. This gap at the rear end 16d of the guide pad portion 16b can be, for example, less than 100 μm, preferably less than tens of μm, and more preferably less than 50 μm.

[0059] If the radius of the outer peripheral surface 16c of the guide pad 16b is smaller than the radius of the cutting edge 16a, a gap will be formed between the outer peripheral cylindrical surface 16c of the guide pad 16b and the workpiece W, which may cause the tap tool 10 to deflect. However, the cutting resistance Rc can be supported by the contact between the tooth lateral surfaces 24b, 26b, and 28b of the thread teeth 24, 26, and 28 and the thread teeth of the internal thread formed on the workpiece W. If the difference in radius is in the range of several μm to tens of μm, the deflection of the tap tool 10 can be prevented.

[0060] The widths GW1, GW2, and GW3 of the outer peripheral surface 16c of the guide pad portion 16b can be constant in the circumferential direction. As a result, the cutting resistance Rc is supported not only on the outer peripheral surface 16c but also on the tooth flanks 24b, 26b, and 28b of the thread teeth 24, 26, and 28 of the incomplete thread portion 20, thus further enhancing the anti-deflection effect of the tap tool 10.

[0061] As a preferred embodiment of the present invention, an example in which the radius of the outer peripheral surface 16c of the guide pad portion 16b is equal to the radius of the cutting edge 16a has been described. As another example, the widths GW1, GW2, and GW3 of the outer peripheral surface 16c of the guide pad portion 16b may also increase slightly in the circumferential direction, that is, the cutting edge 16a may also have a slight clearance angle.

[0062] Furthermore, the threaded portion 16 may also have one or more grooves extending axially. (See reference...) Figure 11 The tap tool 60, like the tap tool 10, has a shank 62 and a cutter body 64 attached to the end of the shank 62. The cutter body 64 is asymmetrically formed with respect to the central axis Ot, and has: an externally threaded portion 66 that engages with the inner circumferential surface of a pre-formed bore H in the workpiece W to machine a thread groove; and a non-engaging portion (not shown) that does not engage with the inner circumferential surface of the bore H. The threaded portion 66 has: an incomplete threaded portion 68 formed at the end portion to guide the cutting portion; and a complete threaded portion 70 at the base end. In this embodiment, the tap tool 10 has two axially extending grooves 72 formed in the threaded portion 66. By providing the grooves 72, lubrication by coolant and chip removal are improved.

[0063] Explanation of reference numerals in the attached figures

[0064] 6 Threaded holes

[0065] 8 Inner circumferential surface

[0066] 10. Taps

[0067] 12. Handle

[0068] 14. Blade Body

[0069] 16 Threaded section

[0070] 16a Cutting edge

[0071] 16b Guide pad

[0072] 16c outer periphery

[0073] 18 Non-engaging parts

[0074] 20 Incomplete thread section

[0075] 22 Complete threaded section

[0076] 24, 26, 28, 30 thread teeth

[0077] 24a, 26a, 28a, 30a outer peripheral surfaces

[0078] lateral surfaces of teeth 24b, 26b, 28b, and 30b

Claims

1. A tap tool for machining a bottom hole formed in a workpiece into a threaded hole, characterized in that, This tap tool has the following features: A handle with a central axis; and The blade body is attached to one end of the handle. The cutter body has a threaded portion that engages with a bottom hole formed in the workpiece, and a non-engaging portion that does not engage with the bottom hole. The threaded portion includes a complete threaded portion on the base end side and an incomplete threaded portion continuously formed on the end side of the complete threaded portion. The incomplete threaded portion includes a cutting edge for machining the bottom hole and a guide pad located behind the cutting edge in the direction of rotation. The outer peripheral surface of the guide pad is formed by a cylindrical surface parallel to the central axis and having a radius equal to the distance from the central axis to the cutting edge.

2. The tap tool as described in claim 1, wherein, The outer peripheral surface of the incomplete threaded portion is formed by a portion of a cylindrical surface parallel to the central axis.

3. The tap tool as described in claim 2, wherein, The outer circumferential surfaces of the plurality of thread teeth are formed in a stepped shape with the radius gradually increasing from the thread teeth at the end to the thread teeth at the base.

4. The tap tool as described in claim 2, wherein, The axial width of the outer peripheral surface of the guide pad is constant in the circumferential direction.

5. The tap tool as described in claim 1, wherein, The threaded portion has a groove that extends axially.

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