Tap tool

Abstract

To prevent a deformation such as the deflection or tilt of a tap tool from deflecting when the cutting edge of the chamfer of a tap tool tip cuts into a workpiece.SOLUTION: A tap tool 10 has a shank part 12 having a center axis Om and a cutter body 14 coupled with one end of the shank part, where the cutter body has a screw part 16 engaged with a prepared hole H formed in a workpiece W, and a non-engagement part 18 not engaged with the prepared hole, and where the screw part comprises a complete thread part 22 on the base end side and an incomplete thread part 20 formed continuously to the tip side of the complete thread part. The incomplete thread part comprises a cutting edge 16a which works the prepared hole and a guide pad part 16b located rearward in the rotation direction of the cutting edge, where the outer peripheral surface of the guide pad part is formed from a cylindrical surface having a cutting edge radius related with the center axis.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a tap tool for machining a pilot hole provided in a workpiece into a threaded hole.

Background Art

[0002] When performing tapping using a machining center and a tap tool mounted thereon, so-called synchronous tapping is performed in which rotation and linear feed are synchronized. In synchronous tapping, it is also necessary to synchronize rotation and feed when pulling out the tap tool from the machined threaded hole. Therefore, the time required to pull out the tap tool is almost equal to the time required to advance the tap tool to machine the thread groove.

[0003] Patent Document 1 describes a tap tool including a threaded portion having a cutting edge portion for machining a thread groove of a threaded hole, a pad portion that engages with the thread groove machined by the cutting edge portion, and a non-engaging portion that forms a space with the threaded hole in a cross-sectional view in which the rotation axis and the central axis of the threaded hole are aligned.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the tap tool of Patent Document 1, since a space is formed between the non-engaging portion and the threaded hole, after the threading is completed, from a state where the rotation axis and the central axis of the threaded hole are aligned, the tap tool is shifted in a direction perpendicular to the rotation axis within the threaded hole, and the engagement between the threaded portion and the thread groove and the engagement between the pad portion and the thread groove are simultaneously released, making it possible to axially pull out the tap tool from the threaded hole.

[0006] In the tapping tool of Patent Document 1, when the cutting edge of the biting portion at the tip of the tapping tool first cuts in, the biting portion cannot be sufficiently supported at the entrance of the pilot hole, and the tapping tool may be deformed such as bending or falling, causing the tapping tool to bend. Furthermore, since the tapping tool of Patent Document 1 is provided with a relief angle on the cutting edge, there is a problem that deformation such as bending or falling is likely to occur particularly when the tapping tool first cuts in.

[0007] The present invention is an improved invention of Prior Document 1, which is a prior application of the present applicant, and aims to solve such problems of the prior art. That is, in a tapping tool capable of shifting the tapping tool in a direction perpendicular to the rotation axis in the screw hole after the machining is completed and then axially pulling out the tapping tool from the screw hole, when the cutting edge of the biting portion at the tip of the tapping tool cuts into the workpiece, an object is to provide a tapping tool in which deformation such as bending or falling does not cause bending.

Means for Solving the Problems

[0008] In order to achieve the above object, according to the present invention, in a tapping tool for machining a pilot hole formed in a workpiece into a screw hole, it comprises a shank portion having a central axis, and a cutter body coupled to one end of the shank portion, the cutter body has a screw portion engaged with the pilot hole formed in the workpiece and a non-engaging portion not engaged with the pilot hole, the screw portion includes a complete screw portion on the base end side and an incomplete screw portion continuously formed on the tip side of the complete screw portion, the incomplete screw portion includes a cutting edge for machining the pilot hole and a guide pad portion located behind the cutting edge in the rotation direction, and an outer peripheral surface of the guide pad portion is a cylindrical surface parallel to the central axis and is formed from a cylindrical surface having a radius equal to the distance from the central axis to the cutting edge. A tapping tool is provided.

Effects of the Invention

[0009] According to the present invention, the outer peripheral surface of the guide pad portion of the incomplete thread portion is a cylindrical surface parallel to the central axis, and is formed from a cylindrical surface having a radius equal to the distance from the central axis to the cutting edge. Therefore, 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 cuts in), the outer peripheral surface of the guide pad supports the cutting resistance, so that the tap tool can be prevented from deflecting.

Brief Description of the Drawings

[0010]

Fig. 1

Fig. 2

Fig. 3

Fig. 4

Fig. 5

Fig. 6

Fig. 7

Fig. 8

Fig. 9

Fig. 10

Fig. 11

Embodiments for Carrying Out the Invention

[0011] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. Referring to FIG. 1, a machine tool 100 to which the tapping tool and tapping method of the present invention are applied is illustrated. In FIG. 1, the machine tool 100 includes a bed 102 as a base fixed to the floor of the factory. On the upper surface of the bed 102, a Y-axis guide rail 118 extends in the horizontal front-rear direction or the Y-axis direction (left-right direction in FIG. 1), and a table 104 is provided so as to be reciprocally movable along the Y-axis guide rail 118. A workpiece W is clamped and fixed to the table 104. As a Y-axis driving device for reciprocally driving the table 104 in the Y-axis direction, the machine tool 100 includes a Y-axis servo motor (not shown). Further, the machine tool 100 includes a Y-axis digital scale (not shown) for detecting the Y-axis coordinate of the table 104.

[0012] On the upper surface of the rear end side of the bed 102, a column 108 is erected. On the front surface of the column 108, an X-axis guide rail 120 extends in the horizontal left-right direction or the X-axis direction (a direction perpendicular to the paper surface in FIG. 1), and an X-axis slider 110 is provided so as to be reciprocally movable along the X-axis guide rail 120. As an X-axis driving device for reciprocally driving the X-axis slider 110 in the X-axis direction, the machine tool 100 includes an X-axis servo motor (not shown). Further, the machine tool 100 includes an X-axis digital scale (not shown) for detecting the X-axis coordinate of the X-axis slider 110.

[0013] On the front surface of the X-axis slider 110, a Z-axis guide rail 122 extends in the vertical direction or the Z-axis direction, and a headstock 112 is provided so as to be reciprocally movable along the Z-axis guide rail 122. As a Z-axis driving device for reciprocally driving the headstock 112 in the Z-axis direction, the machine tool 100 includes a Z-axis servo motor (not shown). Further, the machine tool 100 includes a Z-axis digital scale (not shown) for detecting the Z-axis coordinate of the headstock 112.

[0014] The headstock 112 is attached with a spindle head 116 that rotatably supports a spindle 114 about a vertical axis of rotation Om. At the tip of the spindle 114, a rotary tool T such as an end mill, a face mill, or a drill can be mounted, particularly a tap tool 10 to be described later. The spindle head 116 includes a spindle servo motor 124 that rotationally drives the spindle 114 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 around the axis of rotation Om. The rotational position detection device can be, for example, a rotary encoder 126 attached to the spindle servo motor 124.

[0015] The machine tool 100 can further be a machining center including a tool magazine (not shown) that stores a plurality of tools used for machining, an automatic tool changer (not shown) that exchanges tools between the tool magazine and the spindle 114, and a coolant supply device (not shown) that supplies coolant to the machining area of the machine tool 100. These peripheral devices are housed together with the machine tool 100 inside a cover (not shown).

[0016] The machine tool 100 further includes a control device 130 that controls the machine tool 100. The control device 130 can be composed of a computer including a CPU (central processing unit), a memory device such as a RAM (random access memory) and a ROM (read only memory), a storage device such as an HDD (hard disk drive) and an SSD (solid state drive), an input / output port, and a bidirectional bus that interconnects these, and related software. The control device 130 can particularly be formed by an NC control device that controls an X-axis servo motor, a Y-axis servo motor, a Z-axis servo motor, and the spindle servo motor 124.

[0017] The machine tool 100 controls the X-axis servo motor, the Y-axis servo motor, the Z-axis servo motor, and the spindle servo motor 124 according to a machining program supplied to the control device 130, and relatively moves the rotary tool T mounted at the tip of the spindle in the three orthogonal axis directions of X, Y, and Z with respect to the workpiece W fixed to the table 104 to machine the workpiece W.

[0018] The machine tool 100 performs tapping by synchronizing the rotation of the main shaft 114 and the feed in the Z-axis direction. In this specification, the linear movement in the Z-axis direction in which the tap tool 10 performs tapping is referred to as the forward movement, and the linear movement in the Z-axis direction in which the tap tool 10 is pulled out from the screw hole 6 is referred to as the backward movement.

[0019] The tap tool 10 performs tapping, that is, the process of forming the under hole H into the screw hole 6, with its central axis Ot aligned with the central axis Oh of the under hole H formed in the workpiece W. In FIGS. 8 to 10, reference numeral 8 indicates the inner circumference of the screw hole 6, and the inner circumference of the screw hole 6 coincides with the under hole H. Further, reference numeral 6 indicates the groove of the screw hole 6 corresponding to the nominal diameter of the tap tool 10. The tap tool 10 rotates in the direction of arrow A.

[0020] The tap tool 10 has a rod-shaped shank portion 12 extending along the central axis Ot and a cutter body 14 coupled to the end portion on the tip side of the shank portion 12. The shank portion 12 is formed to be mounted on the tip of the main shaft 114. The shank portion 12 can be formed to be directly mounted in a mounting hole (not shown) formed in the tip of the main shaft 114. Alternatively, the tap tool 10 can mount the shank portion 12 so as to be mountable on a tool holder (not shown) or a tool chuck (not shown), and be mounted on the tip of the main shaft 114 via the tool holder or the tool chuck.

[0021] The cutter body 14 is formed asymmetrically with respect to the central axis Ot, and has a male screw-shaped thread portion 16 that engages with the inner peripheral surface of the under hole H formed in the workpiece W in advance to machine a thread groove, and a non-engagement portion 18 that does not engage with the inner peripheral surface of the under hole H. The thread portion 16 has a plurality of threads 24, 26, 28, 30 (see FIGS. 6 and 7) arranged at a predetermined thread pitch in the longitudinal direction. In this embodiment, the tap tool 10 forms a thread groove of a triangular thread.

[0022] Referring to FIGS. 8 and 9, each thread of the threaded portion 16 has a cutting edge 16a formed at the tip in the rotation direction of the tap tool 10 and a guide pad portion 16b which is a portion extending rearward of the cutting edge 16a in the rotation direction. The guide pad portion 16b is a portion from the cutting edge 16a to the rear end 16d in FIGS. 8 to 10 and has an outer peripheral surface 16c. In the present embodiment, the outer peripheral surface 16c is formed from a part of a cylindrical surface having the same radius as the cutting edge 16a (the distance between the central axis Ot and the cutting edge 16a). That is, in the present embodiment, the threaded portion 16 is not provided with a relief angle at the cutting edge 16a, and in the present embodiment, the tangent line at the cutting edge 16a coincides with the tangent line at the cutting edge 16a with respect to the circumference drawn by the cutting edge 16a.

[0023] The threaded portion 16 has an incomplete threaded portion 20 forming a biting portion formed at the tip portion and a complete threaded portion 22 on the base end side. In the present embodiment, the incomplete threaded portion 20 has three threads 24, 26, and 28. The complete threaded portion 22 has a plurality of threads 30. Referring to FIG. 6, the three threads 24, 26, and 28 of the incomplete threaded portion 20 are arranged at a predetermined thread pitch in the axial direction of the tap tool 10 and have outer peripheral surfaces 24a, 26a, 28a and flank surfaces 24b, 26b, 28b. The flank surfaces 24b, 26b, 28b are arranged substantially symmetrically in the axial direction on both sides of the outer peripheral surfaces 24a, 26a, 28a.

[0024] In the present embodiment, the outer peripheral surfaces 24a, 26a, 28a are each formed from a part of a cylindrical surface, and the outer peripheral surfaces 24a, 26a, 28a are parallel to the central axis Ot. The outer peripheral surface 28a on the tip side of the tap tool 10 has the smallest radius and is thus formed to be the widest in the axial direction. On the other hand, the outer peripheral surface 24a on the base end side has the largest radius and is thus the narrowest in the axial direction. Thus, the incomplete threaded portion 20 is formed such that the outer peripheral surfaces 24a, 26a, 28a are stepped from the outer peripheral surface 24a on the tip side to the outer peripheral surface 28a on the base end side when viewed in the longitudinal cross-section or when the incomplete threaded portion 20 is projected onto a plane.

[0025] On the other hand, in the prior art tap tool, as shown in FIG. 7, in the incomplete thread portion 50 that forms the biting portion, the three threads 52, 54, and 56 are arranged at predetermined thread pitches in the axial direction, and have outer peripheral surfaces 52a, 54a, 56a and flank surfaces 52b, 52c; 54b, 54c; 56b, 56c. The outer peripheral surfaces 52a, 54a, 56a are arranged within a common conical surface. Therefore, the incomplete thread portion 50 is formed in a tapered shape that tapers toward the tip. Thus, in each of the threads 52, 54, and 56, the flank surfaces 52b, 54b, 56b on the base end side are wider than the flank surfaces 52c, 54c, 56c on the tip end side, and a larger machining load acts on the flank surfaces 52b, 54b, 56b on the base end side than on the flank surfaces 52c, 54c, 56c on the tip end side during machining.

[0026] Due to the difference in the sizes of the flank surfaces on the base end side and the tip end side of the thread of the incomplete thread portion that forms this biting portion, in the prior art tap tool, a problem occurs in that the tap tool falls and deforms by bending during machining. In contrast, in the present embodiment, since the flank surfaces 24b, 26b, 28b are arranged substantially symmetrically in the axial direction on both side portions of the outer peripheral surfaces 24a, 26a, 28a, during machining, particularly when the incomplete thread portion 20 of the tap tool 10 begins to engage with the counterbore H of the workpiece W, the tap tool 10 is prevented from falling and bending.

[0027] The complete thread portion 22 has a plurality of, in this embodiment, seven threads 30. The threads 30 have flank surfaces 30b and outer peripheral surfaces 30a, and the flank surfaces 30b are arranged symmetrically in the axial direction on both side portions of the outer peripheral surfaces 30a. The complete thread portion 22 has a shape that matches the valley shape of the internal thread to be machined.

[0028] The non-engaging portion 18 has a smooth curved surface and can be formed, for example, as a part of a cylindrical surface with a radius smaller than that of the shank portion 12. A space 4 is formed between the non-engaging portion 18 and the inner peripheral surface 8 of the threaded hole 6 machined in the workpiece W. When the tap tool 10 moves (shifts) in a direction perpendicular to the rotation axis Om from a position coinciding with the central axis Oh of the threaded hole 6 of the workpiece W as shown by the arrow S in FIG. 10, the engagement between the threaded portion 16 and the female thread machined in the workpiece W is released, that is, the thread flanks 24, 26, 28, 30 of the threaded portion 16 have a size that can completely separate from the inner peripheral surface 8 of the female thread of the workpiece W. In FIG. 10, the arrow S is a vector indicating the moving direction and the moving amount of the main shaft 114.

[0029] It is desirable to form the size of the space 4 slightly larger with a safety margin. Also, during cutting, the space 4 serves as a path for supplying cutting fluid to the cutting edge 16a and a path for discharging the chips generated by cutting, which has the effect of improving the quality of the machined surface and extending the tool life.

[0030] As shown in FIG. 10, when the engagement between the threaded portion 16 and the thread groove of the workpiece W is released by shifting the main shaft 114, the tap tool 10 can be withdrawn from the threaded hole 6 by a retracting movement along the rotation axis Om (upward movement along the Z axis in FIG. 1). Since the withdrawal of this tap tool 10 does not include a rotational movement as in the conventional case, it can be performed at high speed.

[0031] In the following description, the 3 o'clock direction in FIG. 8 is taken as the origin of the rotational position around the rotation axis Om of the main shaft 114 (the position where the rotation angle θ = 0°). In FIG. 8, the rotation angle (hereinafter referred to as the "phase angle") of the tap tool 10 is illustrated as 180 degrees as the phase angle of the cutting edge 16a. The phase angle of the tap tool 10 that has stopped after machining is different for each threaded hole 6 because the number of rotations of the tap tool 10 required for machining differs if the depth of the threaded hole 6 is different. Therefore, the direction of the shift S of the tap tool 10 also differs for each threaded hole 6.

[0032] In order to determine the direction in which the main shaft 114 is shifted, in this embodiment, when positioning the tap tool 10 at the machining start point (not shown), the main shaft 114 is set to a predetermined phase angle. Then, when it stops after machining, the control device 130 calculates the phase angle of the tap tool 10 based on the information from the rotary encoder 126 of the main shaft servo motor 124. Based on the calculated phase angle of the tap tool 10, the control device 130 calculates the direction of shift of the main shaft 114 (angle θ in FIG. 0). On the other hand, since the required shift amount is determined by the cross-sectional shape of the tap tool 10, it can be stored in the control device 130 in advance.

[0033] An example of tapping performed using the tap tool 10 according to an embodiment of the present invention and a vertical machine tool 100 as shown in FIG. 1 will be described below. First, after mounting the tap tool 10 on the main shaft 114, it is positioned at the machining start point. That is, the rotation axis Om of the main shaft 114 of the machine tool on which the tap tool 10 is mounted is aligned with the central axis Oh of the pilot hole H provided in the workpiece, and the tip of the tap tool 10 is positioned at the machining start point at a predetermined height in the Z-axis direction. At this time, the main shaft 114 is rotationally fed to a predetermined phase angle so that the cutting edge 16a is arranged at a predetermined rotational position.

[0034] Next, the rotational speed of the main shaft 114 and the feed speed in the Z-axis direction are synchronized according to the pitch of the screw, and synchronous tapping is performed. When the tap tool 10 moves a predetermined distance in the Z-axis direction and reaches the commanded screw depth, the rotation of the main shaft 114 and the feed in the Z-axis direction stop. Thereby, the pilot hole H of the workpiece is machined into a screw hole 6.

[0035] Next, the tap tool 10 is shifted in a direction perpendicular to the rotation axis Om. The shift direction of the tap tool 10 (the direction represented by the arrow S in FIG. 10) is calculated based on the phase angle of the tap tool 10 (the rotational position of the cutting edge 16a) calculated based on the information from the rotary encoder 126 of the main shaft servo motor 124. As the shift amount, a value registered in the control device 130 in advance is used. By this process, the engagement between the screw portion 16 of the tap tool 10 and the screw groove of the screw hole 6 is completely released.

[0036] Next, without rotating the tapping tool 10, it is retracted upward to the machining start point. At this time, the feed speed of the main shaft 114 in the Z-axis direction can be made more than twice as fast as the feed speed during machining, that is, during forward movement. In this way, the tapping of one screw hole 6 is completed.

[0037] According to the present embodiment, a space 4 is formed between the non-engaging portion 18 of the tapping tool 10 and the inner diameter of the screw hole 6, and the space 4 has a size that releases the engagement between the thread portion 16 and the thread groove when the tapping tool 10 moves in a direction perpendicular to the rotation axis Om. Therefore, after machining, the tapping tool 10 whose engagement with the thread groove of the screw hole 6 has been released can be quickly withdrawn in the direction of the rotation axis from the screw hole 6 without rotating.

[0038] Also, referring to FIG. 9, while the tapping tool 10 is rotating for tapping, the cutting resistance Rc acting on the cutting edge 16a of the tapping tool 10 as a reaction force to the cutting force, its back component force Rb, and the main component force Rp are shown as vectors. Since the main component force Rp is larger than the back component force Rb, the resultant cutting resistance Rc acts toward the guide pad portion 16b behind the rotation direction of the cutting edge 16a. The outer peripheral surface of each thread crest of the guide pad portion 16b is a cylindrical surface parallel to the center line Ot and is formed from a cylindrical surface having 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 the contact of the cylindrical surface on the outer periphery of the guide pad portion 16b with the workpiece W. Thus, according to the present embodiment, since the outer peripheral surface 16c of the guide pad portion 16b is formed from a part of a cylindrical surface having a radius equal to the radius of the cutting edge 16a, the cutting resistance Rc is supported by the surface of the screw hole 6, particularly the thread groove (valley) formed in the workpiece W, through the outer peripheral surface 16c of the guide pad portion 16b. As a result, the tapping tool 10 does not fall or bend due to the cutting resistance Rc, and the machining accuracy is equivalent to that when using a conventional ordinary tapping tool.

[0039] Although it has been described that the radius of the outer peripheral surface 16c of the guide pad portion 16b is equal to the radius of the cutting edge 16a, "equal" does not mean exactly the same in a strict sense. In the present invention, "equal radius" includes the same radius or a radius smaller by several μm to several tens of μm. That is, "equal radius" includes "substantially equal radius". For example, "equal radius" may include machining errors within an appropriate range.

[0040] Furthermore, in order to lubricate the space between the outer peripheral surface 16c of the guide pad portion 16b and the surface of the thread groove (valley) formed in the workpiece W with a coolant, or in order to prevent the cutting resistance Rc from increasing excessively, within a range where the guide pad portion 16b can support the cutting resistance Rc to prevent the tap tool 10 from deflecting, the radius of the outer peripheral surface 16c of the guide pad portion 16b may be made smaller than the radius of the cutting edge 16a so that a gap is formed between the outer peripheral surface 16c of the guide pad portion 16b and the workpiece W. This gap can be, for example, 100 μm or less, preferably several tens of μm or less, more preferably 50 μm or less.

[0041] Alternatively, the radius of the outer peripheral surface 16c of the guide pad portion 16b may be gradually reduced in the circumferential direction from the cutting edge 16b toward the rear end 16d so that a gap is formed between the outer peripheral surface 16c and the workpiece W. This gap can be, at the rear end 16d of the guide pad portion 16b, for example, 100 μm or less, preferably several tens of μm or less, more preferably 50 μm or less.

[0042] If the radius of the outer peripheral surface 16c of the guide pad portion 16b is smaller than the radius of the cutting edge 16a, a gap is formed between the outer peripheral cylindrical surface 16c of the guide pad portion 16b and the workpiece W, and there is a concern that the tap tool 10 may deflect. However, by the flank surfaces 24b, 26b, 28b of the thread flanks 24, 26, 28 coming into contact with the thread flanks of the female thread formed in the workpiece W, the cutting resistance Rc can be supported, and if the difference in radius is in the range of several μm to several tens of μm, deflection of the tap tool 10 can be prevented.

[0043] The widths GW1, GW2, and GW3 of the outer peripheral surface 16c of the guide pad portion 16b can be made 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 flank surfaces 24b, 26b, and 28b of the threads 24, 26, and 28 of the incomplete thread portion 20, further enhancing the effect of preventing the tap tool 10 from deflecting.

[0044] 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 gradually increase slightly in the circumferential direction, that is, the cutting edge 16a may have a slight relief angle.

[0045] Further, the thread portion 16 may have one or a plurality of groove portions extending in the axial direction. Referring to FIG. 11, the tap tool 60, like the tap tool 10, has a shank portion 62 and a cutter body 64 coupled to an end portion on the tip side of the shank portion 62. The cutter body 64 is formed asymmetrically with respect to the central axis Ot, and has a male-threaded thread portion 66 that engages with the inner peripheral surface of the pilot hole H previously formed in the workpiece W to machine a thread groove, and a non-engaging portion (not shown) that does not engage with the inner peripheral surface of the pilot hole H. The thread portion 66 has an incomplete thread portion 68 that forms a biting portion formed at the tip portion, and a complete thread portion 70 on the base end side. In the present embodiment, the tap tool 10 is provided with two axially extending grooves 72 formed in the thread portion 66. By providing the grooves 72, lubrication by the coolant and discharge of chips are further improved.

Description of reference numerals

[0046] 6 Thread hole 8 Inner peripheral surface 10 Tap tool 12 Shank portion 14 Cutter body 16 Thread portion 16a Cutting edge 16b Guide pad portion 16c Outer peripheral surface 18 Non-engaging portion 20 Incomplete thread portion 22 Complete thread portion 24, 26, 28, 30 Threads 24a, 26a, 28a, 30a Outer peripheral surface 24b, 26b, 28b, 30b Flank surface

Claims

1. In a tap tool for machining a drilled hole formed in a workpiece into a threaded hole, it comprises a shank portion having a central axis, and a cutter body coupled to one end of the shank portion, wherein the cutter body has a threaded portion engaging with the drilled hole formed in the workpiece and a non-engaging portion not engaging with the drilled hole, the threaded portion includes a complete thread portion on the base end side and an incomplete thread portion continuously formed on the tip end side of the complete thread portion, the incomplete thread portion includes a cutting edge for machining the drilled hole and a guide pad portion positioned rearward in the rotational direction of the cutting edge, A tap tool, characterized in that an outer peripheral surface of the guide pad portion is a cylindrical surface parallel to the central axis and is formed from a cylindrical surface having a radius equal to a distance from the central axis to the cutting edge.

2. The tap tool according to claim 1, wherein an outer peripheral surface of the incomplete thread portion is formed from a part of a cylindrical surface parallel to the central axis.

3. The tap tool according to claim 2, wherein outer peripheral surfaces of the plurality of threads are formed in a stepped shape such that a radius gradually increases from the thread on the tip end side to the thread on the base end side.

4. The tap tool according to claim 2, wherein an axial width of the outer peripheral surface of the guide pad portion is constant in the circumferential direction.

5. The tap tool according to claim 1, wherein the threaded portion has a groove extending in the axial direction.

Images