Point tap

Abstract

A point tap (10) is provided with a threaded part (14) and a groove (20). The threaded part (14) is provided with a chamfer part (16) and a full thread part (18). The groove (20) is provided with a primary groove (21) and a secondary groove (22). The primary groove (21) is provided in the full thread part (18). The secondary groove (22) is provided in the chamfer part (16). The secondary groove (22) is twisted in a direction opposite to the rotation direction of the threaded part (14). The primary groove (21) is twisted in the same direction as the rotation direction of the point tap (10). The threaded part (14) is provided with a back taper and an eccentric relief. The effective diameter of the threaded part (14) decreases toward a shank part (12) side.

Description

Point Tap

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

[0002] The thread portion of a point tap has a chamfer portion and a full thread portion (see, for example, Patent Document 1). The full thread portion has a linear primary flute. The chamfer portion has a secondary flute. The secondary flute twists in the opposite direction to the rotation of the thread portion. Therefore, the secondary flute pushes chips forward and discharges them.

[0003] U.S. Patent No. 7,144,208

[0004] The reaction force generated when chips are ejected acts on the point tap in the opposite direction to its forward movement. Because the point tap is pushed back against the workpiece, it creates a female thread with a delay compared to its original lead. This causes the slope of the point tap's threads on the base side to rub against the female thread in a stepped manner. This makes the threads of the point tap prone to wear, potentially affecting tool life.

[0005] An object of the present invention is to provide a point tap that can be expected to extend the tool life.

[0006] The point tap of the present invention comprises a thread portion having a chamfer portion and a full thread portion, a primary groove provided in the full thread portion, and a secondary groove provided in the chamfer portion and twisted in a direction opposite to the rotational direction of the thread portion or tilted in a direction opposite to the rotational direction, wherein the primary groove twists in the rotational direction or tilts toward the rotational direction with respect to the axial direction, and the thread portion is provided with a back taper in which the outer diameter and effective diameter decrease from the tip end to the rear end of the tool, and an eccentric relief that continuously reduces from the cutting edge to the backside of the cutting edge in the cutting thickness, and wherein the effective diameter of the thread portion decreases toward the rear end.

[0007] According to the present invention, the point tap has a driving force due to the twist in the rotational direction at the full thread portion. Therefore, a force acts on the point tap in the direction in which the point tap itself moves forward. The force acting on the point tap is offset by the return force generated by cutting in the secondary groove of the chamfer portion. Therefore, the point tap can achieve stable cutting.

[0008] In addition, because the point tap advances along its original lead, the threaded portion makes proper contact with the workpiece, thereby suppressing abnormal wear and chipping of the point tap.

[0009] The thread portion also has a back taper and eccentric relief. The back taper is a shape in which the outer diameter and effective diameter decrease from the tip to the rear end of the tool. The eccentric relief is a shape in which the cutting edge is continuously relieved from the tip to the rear end of the cutting edge. These two processes are applied to the thread portion, and the effective diameter of the thread portion decreases toward the rear end. This allows the point tap to minimize contact with the female thread when cutting a female thread into a workpiece. Therefore, the point tap can effectively reduce contact friction with the female thread, improving wear resistance.

[0010] The twist angle or inclination angle of the primary groove may be 1° or more and 7° or less. Therefore, the point tap can more effectively obtain the effect described in claim 1.

[0011] The connecting portion between the primary groove and the secondary groove may be located opposite the first complete crest at the most distal end of the complete crest portion. This allows the forward force generated by the primary groove and the return force generated by the secondary groove to be offset in a balanced manner, thereby enabling the point tap to achieve more stable cutting.

[0012] The point tap may be a right-hand cutting edge that rotates clockwise when viewed from the rear end in the axial direction, the secondary grooves may be left-handed or inclined in the direction of left rotation relative to the axial direction, and the primary grooves may be right-handed or inclined in the direction of right rotation relative to the axial direction. Therefore, the right-hand cutting edge point tap can achieve the effect described in claim 1.

[0013] The point tap may be a left-handed blade that rotates leftward when viewed from the rear end side in the axial direction, the secondary grooves may be right-handed helical or inclined in the direction of right rotation with respect to the axial direction, and the primary grooves may be left-handed helical or inclined in the direction of left rotation with respect to the axial direction. Therefore, the left-handed point tap can achieve the effect described in claim 1.

[0014] 1 is a perspective view of the point tap 10; FIG. 2 is a side view of the point tap 10 (helix angle θ1 = 1°); FIG. 3 is a side view of the point tap 30 (helix angle θ2 = 5°); FIG. 4 is a diagram illustrating the principle of enlarging an internal thread when cutting with a conventional point tap 100; FIG. 5 is a front view of the point tap 10 as viewed from the tip side; FIG. 6 is a side view of the tip side of the point tap 10; FIG. 7 is a conceptual diagram illustrating the direction of the back taper and the relief direction of the thread portion; FIG. 8 is a conceptual diagram illustrating the arrangement of cutting edges when a primary groove is formed in a thread portion, and the arrangement of cutting edges when a secondary groove is formed after the primary groove; FIG. 9 is a photograph of the workpiece surface after machining with a conventional product; FIG. 10 is a photograph of the workpiece surface after machining with a product of the present invention; FIG. 11 is a graph showing test results comparing average torque; FIG. 12 is a graph showing test results comparing average thrust; FIG. 13 is a side view of the point tap 300 (helix angle θ1 = 1°).

[0015] An embodiment of the present invention will be described. In the following description, in the axial direction along the axis AX of the point tap 10 shown in Figure 1, the threaded portion 14 side is the leading end side of the point tap 10, and the shank portion 12 side is the rear end side of the point tap 10. To clarify the description of this embodiment, some parts in the drawings are shown with dimensional ratios that differ from the actual dimensional ratios. Therefore, the present invention should not be interpreted as being limited to the shapes in the drawings.

[0016] The configuration of a point tap 10 will be described with reference to Figures 1 and 2. The point tap 10 is a tool used to cut a female thread into a pilot hole. The pilot hole is a through hole that is pre-formed in a workpiece (shown). The point tap 10 comprises a shank portion 12 and a threaded portion 14. The shank portion 12 is attached to a machine spindle (not shown) or the like and is driven to rotate. A male thread is formed in the threaded portion 14. The male thread has a thread shape that corresponds to the thread groove of the female thread.

[0017] The thread portion 14 has a chamfering portion 16 and a full thread portion 18. The diameter of the chamfering portion 16 decreases toward the tip. The diameter of the full thread portion 18 is approximately constant. As shown in FIG. 2 , the slope on the leading side of the male thread 15 is a leading flank surface 151. The slope on the following side of the thread 15 is a following flank surface 152.

[0018] Five grooves 20 are provided in the threaded portion 14 in the axial direction. The axial direction is a direction parallel to the axis AX. The five grooves 20 extend from the tip of the threaded portion 14 to the tip side of the shank portion 12. The five grooves 20 divide the external thread of the threaded portion 14 into five parts in the circumferential direction. A cutting edge 25 is formed at one end of the divided thread, i.e., the end in the counterclockwise direction as viewed from the tip side in Figure 2. The rotation direction R of the point tap 10 is the clockwise direction as viewed from the rear end side of the point tap 10. The point tap 10 is a right-handed tool and has a right-handed blade.

[0019] The groove 20 includes a primary groove 21 and a secondary groove 22. The primary groove 21 is formed in the complete thread portion 18 of the thread portion 14. The primary groove 21 supplies cutting oil to the tip side of the point tap 10. The secondary groove 22 is formed in the chamfer portion 16 of the thread portion 14. The secondary groove 22 is a helical groove that is helical in the direction opposite to the rotation direction R of the point tap 10, and in this embodiment, is a left-handed helix. The secondary groove 22 is formed by obliquely cutting away several threads from the groove 20 on the cutting edge 25 side of the chamfer portion 16. Therefore, during cutting with the point tap 10, chips are discharged in the direction of advancement in the pilot hole. Note that although the secondary groove 22 is twisted in the direction opposite to the rotation direction, it may also be inclined in the direction opposite to the rotation direction with respect to the axis AX, for example. The connection Q between the primary groove 21 and the secondary groove 22 is located opposite the first complete thread 17, which is located at the most distal end of the complete thread portion 18.

[0020] The primary grooves 21 are helical grooves that are twisted in the same direction as the rotational direction of the point tap 10. Therefore, the primary grooves 21 are right-handed. For example, the helix angle θ1 of the primary grooves 21 of the point tap 10 shown in FIG. 2 is 1°. The helix angle θ2 of the primary grooves 21 of the point tap 30 shown in FIG. 3 is 5°. The helix angles θ1 and θ2 are the angles between the primary groove 21 and a line P that passes through a point on the primary groove 21 and is parallel to the axis AX. Note that although the primary grooves 21 are twisted in the same direction as the rotational direction, they may be inclined toward the rotational direction with respect to the axis AX, for example.

[0021] The thread portion 14 is further provided with a back taper and an eccentric relief. The effective diameter of the thread portion 14 decreases from the tip end to the rear end of the tool. The back taper, eccentric relief, and effective diameter of the thread portion 14 will be described later.

[0022] The principle of enlargement of a female thread using a conventional product will be described with reference to Figure 4. Point tap 100 is a conventional product. Point tap 100 includes a shank portion 12, a thread portion 14, and a groove 200. The primary groove 211 of groove 200 is a straight groove. Enlargement of a female thread refers to a state in which, for example, after cutting a workpiece W with point tap 100, the quality of the female thread 60 is inspected using a thread plug gauge, and the no-thread side thread plug gauge is threaded in more than two turns.

[0023] The point tap 100 cuts a female thread 60 into a pilot hole 40 that has been pre-drilled in a workpiece W. A thread 61 of the formed female thread 60 has an entry flank surface 62 and an exit flank surface 63 formed thereon.

[0024] During cutting, the point tap 100 must advance accurately along its intended lead. However, due to the reaction force generated when chips are discharged from the secondary groove 221, a strong thrust force acts on the point tap 100 in the direction opposite to its advance. This causes the point tap 100 to be pushed back in the opposite direction. Since the point tap 100 no longer advances along its intended lead, excessive cutting of the internal thread 60 occurs.

[0025] Specifically, when the first cutting edge contacts and cuts the workpiece W, the next cutting edge overcuts the entry flank surface 62 of the workpiece W due to the opposite thrust force, later than the specified lead. Then, the next cutting edge overcuts the entry flank surface 62 of the workpiece W, later than the lead again. This is repeated, and a step is formed on the entry flank surface 62 of the thread 61. Therefore, collapse occurs on the mouth side of the internal thread 60, causing the internal thread to widen.

[0026] Furthermore, a strong thrust force acts on the conventional point tap 100 in the direction opposite to the direction of advance. Therefore, the point tap 100 performs machining in a state where the trailing flank of the thread 14 (see trailing flank 152 shown in FIG. 2 ) rubs against the exit flank 63 of the internal thread 60. Therefore, wear on the trailing flank of the thread 14 progresses faster than wear on the exit flank. This also creates the problem of a shorter tool life for the point tap 100.

[0027] Furthermore, the primary flutes of the conventional point tap 100 are straight. Therefore, when the point tap 100 rotates forward, the multiple threads that make up the full thread portion 18 begin to rotate in the same phase. In other words, if an imaginary line parallel to the axis AX (see imaginary line K in Figure 1) is drawn on the workpiece W, the multiple threads will pass through that imaginary line simultaneously. Therefore, the resistance received from the workpiece W tends to concentrate when multiple threads come into contact with the workpiece W at the same time.

[0028] The effect of the twist of the primary grooves 21 in the point tap 10 will now be described. As described above, the primary grooves 21 of the point tap 10 twist in the same direction as the rotational direction R. Therefore, the point tap 10 receives a thrust force with the same twist as the rotational direction R. Therefore, a thrust force in the forward direction acts on the point tap 10. The thrust force in the forward direction generated by the primary grooves 21 is offset by the opposite thrust force generated by the secondary grooves 22. Therefore, the point tap 10 can proceed accurately along its original lead during cutting, thereby suppressing the expansion of the internal thread 60 described above.

[0029] Furthermore, a thrust force acts on the point tap 10 in the direction of advance. The leading flank surface 151 of the point tap 10 contacts the entry flank surface 62 of the internal thread 60. The trailing flank surface 152 of the point tap 10 contacts the exit flank surface 63 of the internal thread 60 with the same amount of force as when the leading flank surface 151 contacts the entry flank surface 62. Therefore, the leading flank surface 151 and the trailing flank surface 152 of the point tap 10 wear to the same extent. Therefore, the point tap 10 can be expected to have an extended tool life. Internal thread

[0030] The back taper and eccentric relief applied to the thread portion 14 will be described with reference to Figures 5 to 8. As shown in Figures 5 and 6, the thread portion 14 is provided with a back taper and eccentric relief. The back taper is a shape in which the outer diameter and effective diameter decrease from the front end to the rear end of the point tap 10. The effective diameter is the diameter of an imaginary cylinder in which the groove width of the thread groove and the width of the thread are the same.

[0031] The eccentric relief is a shape in which the thread of the thread portion 14 is continuously relieved from the cutting edge to the backside of the thread. Specifically, it is a shape in which the amount of relief continuously increases from the cutting edge to the backside of the thread in the cutting thickness. The amount of relief is the amount of gap formed between the relief face of the thread and the contact surface of the female thread. The relief direction of the thread portion 14 is opposite to the rotation direction R.

[0032] 7 conceptually illustrates multiple cutting edges aligned in the back taper direction and multiple cutting edges aligned in the relief direction of the thread portion. For ease of explanation, the shapes of the cutting edges are made identical. The back taper direction is from the tip side of the tool toward the rear end side. The cutting edge C at the forefront of the tool is the cutting edge that first comes into contact with the internal thread. The height of the cutting edge is the radial distance between the apex of the cutting edge and the axis of the tool. In this embodiment, the height of the cutting edge C at the forefront of the tool is taken as the reference height. In the back taper direction, the height of the cutting edge gradually decreases from the reference height toward the rear end side.

[0033] The cutting edge of the eccentric relief continuously moves away from the female thread from the cutting edge to the backside of the cutting edge. Therefore, in the direction of the movement, the height of the cutting edge gradually decreases from the reference height toward the downstream side.

[0034] Figure 8 shows the arrangement of cutting edges when primary grooves are formed in the thread portion, and the arrangement of cutting edges when secondary grooves are formed after the primary grooves. The two-dot chain line in Figure 8 indicates the direction in which the secondary grooves are formed. Note that in Figure 8, the inclination angle of the secondary grooves relative to the axis is shown larger than in the example to make it easier to understand the position in which the secondary grooves are formed.

[0035] The arrangement of the cutting edges when a primary groove is formed in the thread portion is the arrangement of cutting edges A1 to A7. The arrangement of the cutting edges when a secondary groove is formed after the primary groove is the arrangement of cutting edges B1 to B7. The cutting edges B1 to B7 are arranged along the secondary groove. The arrangement of the cutting edges B1 to B7 is the arrangement of the cutting edges in the chamfer 16 of the point tap 10 of this embodiment.

[0036] The cutting edges B1 to B7 arranged along the secondary flutes are ground so that they become lower from the tip to the rear end of the tool. Therefore, the height of the cutting edges B1 to B7 decreases from the tip to the rear end of the tool. Therefore, the effective diameter of the thread portion 14 of the point tap 10 decreases from the tip to the rear end of the tool.

[0037] This minimizes contact with the female thread when cutting the female thread into the workpiece, thereby effectively reducing contact friction between the point tap 10 and the female thread, thereby improving the wear resistance of the point tap 10.

[0038] Next, a comparative test was conducted on the workpiece surface after cutting using the point tap. In this test, a female thread was machined into each workpiece using the product of the present invention and a conventional product, and the state of the female thread surface after machining was compared. The product of the present invention is the point tap 10 of the present invention (see Figure 2) with a primary flute helix angle of 1°. The conventional product is the point tap 100 (see Figure 4) with a primary flute helix angle of 0°. The machining conditions were as follows: Point tap diameter = M14X1.5 Workpiece = S50C Cutting speed = 36 m / min Feed rate = 1.5 mm / rev

[0039] The results will be explained with reference to Figures 9 and 10. Figure 9 is a photograph of the surface of the internal thread, taken from the inlet side of the workpiece, after internal thread machining using a conventional product. Looking at the surface of the internal thread after machining, many thin, streaky chatter marks were visible. This is presumably because machining was performed in a state in which the follow-up flank surface of the point tap 100 rubbed against the outlet flank surface 63 of the internal thread 60, causing chatter in the point tap 100 and making the internal thread machining unstable.

[0040] Figure 10 is a photograph of the surface of a thread, viewed from the entry side of the workpiece, after the thread was machined using the product of the present invention. Looking at the surface of the thread after machining, chatter marks were almost completely eliminated compared to the surface of the thread made with a conventional product. This is presumably because the point tap 10 advanced accurately along its original lead, and the leading flank 151 and the trailing flank 152 of the point tap 10 made equal contact with the entry flank 62 and the exit flank 63 of the thread, suppressing chatter and stabilizing the cutting process. These results demonstrate that the product of the present invention can perform more stable machining than conventional products.

[0041] Referring to Figure 11, a torque test of the point tap during cutting will be described. In this test, five types of point taps (product of the present invention) with primary flute helix angles of 1°, 3°, 5°, 7°, and 9° were prepared, as well as a conventional product. In this test, the torque of the point tap was measured when cutting a female thread into a pilot hole (through hole) formed in the workpiece. The test was performed twice and the average values ​​were compared. The conventional product is a point tap with a straight primary flute (helical angle = 0°). The cutting conditions were as follows: Point tap diameter = M14X1.5 Workpiece = S50C Cutting speed = 36 m / min Feed rate = 1.5 mm / rev

[0042] The results will be explained. As shown in Figure 11, the average torque of the conventional product was 1353 (Ncm). The average torque of the 1° twist point tap was 779 (Ncm). The average torque of the 3° twist point tap was 887 (Ncm). The average torque of the 5° twist point tap was 916 (Ncm). The average torque of the 7° twist point tap was 900 (Ncm). The average torque of the 9° twist point tap was 877 (Ncm). Among the products of the present invention, the 1° twist had the lowest average torque.

[0043] From these results, it is presumed that the torque increased with the conventional product because the cutting was performed with the trailing flank rubbing against the inclined surface of the female thread. On the other hand, with the product of the present invention, the average torque during cutting was lower than that of the conventional product for all five types of twisted primary grooves. This is presumed to be because the point tap advanced along its original lead, as thrust force acted in the direction of advancement with all of the products of the present invention. Therefore, it was confirmed that the product of the present invention had a torque reduction effect compared to the conventional product at all twist angles from 1° to 9°.

[0044] Referring to Figure 12, a thrust test of a point tap during cutting will be described. Five types of point taps (the present invention) with primary flute helix angles of 1°, 3°, 5°, 7°, and 9° were prepared for this test, along with a conventional point tap. In this test, the thrust of the point tap was measured when a pilot hole (through hole) formed in the workpiece was threaded. The test was performed twice and the average values ​​were compared. The conventional point tap had a straight primary flute (helical angle = 0°). The machining conditions were the same as those for the torque test. Note that the positive side of the average thrust (N) in the graph shown in Figure 12 represents the thrust in the direction opposite to the direction of advance, and the negative side represents the thrust in the direction of advance.

[0045] The results will be explained below. As shown in Figure 12, the average thrust of the conventional product was 187 (N). The average thrust of the 1° helix point tap was 148 (N). The average thrust of the 3° helix point tap was 103 (N). The average thrust of the 5° helix point tap was 68 (N). The average thrust of the 7° helix point tap was 32 (N). The average thrust of the 9° helix point tap was -15 (N).

[0046] These results show that the average thrust during cutting was lower than that of the conventional product in all cases where the twist angle was 1° to 9°. This is presumably due to the thrust force acting in the direction of advancement.

[0047] However, at a 9° helix, the thrust reversed to the direction of advance. This is presumably because the twist of the primary groove was large, causing excessive thrust force in the direction of advance, causing the point tap to advance further in the direction of advance than its intended lead. Therefore, the product of the present invention was confirmed to have a reduced thrust effect compared to the conventional product at any helix between 1° and 9°, and it was also confirmed that a helix between 1° and 7° was more preferable.

[0048] As described above, the point tap 10 of this embodiment includes a threaded portion 14 and a groove 20. The threaded portion 14 includes a chamfer 16 and a full thread portion 18. The groove 20 includes a primary groove 21 and a secondary groove 22. The primary groove 21 is provided in the full thread portion 18. The secondary groove 22 is provided in the chamfer 16 and twists in the opposite direction to the rotational direction of the threaded portion 14. The primary groove 21 twists in the same direction as the rotational direction of the point tap 10. Therefore, the point tap 10 has a driving force due to the twist in the rotational direction at the full thread portion 18. A force acts on the point tap 10 in the direction in which the point tap 10 itself advances. The force acting on the point tap 10 is offset by a return force generated by cutting in the secondary groove 22 of the chamfer 16. Therefore, the point tap 10 can achieve stable cutting. Furthermore, because the point tap 10 advances along its original lead, the threaded portion 14 appropriately contacts the workpiece. This prevents abnormal wear and chipping of the point tap 10. Furthermore, when the point tap 10 rotates forward, there is a difference in the passage time between the first complete thread 17 on the leading edge side and the complete thread 19 on the trailing edge side of the full thread portion 18. This distributes the resistance received from the workpiece, allowing the point tap 10 to achieve stable cutting.

[0049] The thread portion 14 is provided with a back taper and an eccentric relief. The back taper is a shape in which the outer diameter and effective diameter decrease from the tip side of the tool toward the rear end. The eccentric relief is a shape in which the cutting edge is continuously relieved from the cutting edge to the back side of the cutting edge. These two processes are applied to the thread portion, and the effective diameter of the thread portion 14 decreases toward the rear end. This allows the point tap 10 to minimize contact with the female thread when cutting a female thread into a workpiece. Therefore, the point tap 10 can effectively reduce contact friction with the female thread, improving the wear resistance of the point tap 10.

[0050] By setting the helix angle of the primary groove 21 to be between 1° and 7°, the point tap 10 can be prevented from lagging behind or overleading its original lead during cutting. Therefore, the point tap 10 can achieve stable cutting.

[0051] The connection portion Q between the primary groove 21 and the secondary groove 22 is located opposite the first complete crest 17 located at the most distal end of the complete crest portion 18. Therefore, the forward force of the primary groove 21 and the return force of the secondary groove 22 are offset in a balanced manner, allowing the point tap 10 to achieve more stable cutting.

[0052] The present invention is not limited to the above embodiment and various modifications are possible. The point tap 10 in this embodiment has a right-hand blade, the secondary flutes 22 are left-hand helix, and the primary flutes 21 are right-hand helix. For example, the present invention can be applied to a left-hand blade such as the point tap 300 shown in FIG. 13 . The rotation direction R of the point tap 300 is left-hand (counterclockwise) when viewed from the rear end of the point tap 300. In this configuration, the secondary flutes 122 are right-hand helix, and the primary flutes 121 are left-hand helix. The helix angle θ3 of the primary flutes 121 is 1°. The cutting edge 125 is formed at one end of the thread divided by the flutes 120, at the end in the clockwise direction when viewed from the front end. Even with this left-hand blade point tap 300, the same effects as those of the above embodiment can be achieved.

[0053] Although the primary grooves 21 of the point tap 10 are right-handed, they may be inclined in a clockwise direction relative to the axial direction parallel to the axis AX. Also, if the point tap is a left-handed cutting edge and the secondary grooves are right-handed or inclined in a clockwise direction relative to the axial direction, the primary grooves may be left-handed or inclined in a counterclockwise direction relative to the axial direction.

[0054] Furthermore, the connection Q between the primary groove 21 and the secondary groove 22 is located opposite the first complete crest 17 , and specifically, it is desirable that the connection Q be within 0.5 crests of the first complete crest 17 .

[0055] Although the point tap 10 has five grooves 20, the number of grooves may be other than this, for example, two to four grooves, or six or more grooves.

Claims

1. A point tap comprising: a threaded portion having a chamfer portion and a full thread portion; a primary groove provided in the full thread portion; and a secondary groove provided in the chamfer portion and twisted in a direction opposite to the rotational direction of the threaded portion or tilted in a direction opposite to the rotational direction, wherein the primary groove twists in the rotational direction or tilts toward the rotational direction with respect to the axial direction, and wherein the threaded portion is provided with a back taper in which the outer diameter and effective diameter decrease from the tip side to the rear end of the tool, and an eccentric relief that continuously reduces from the cutting edge to the backside of the cutting edge in the cutting thickness, and wherein the effective diameter of the threaded portion decreases as it moves toward the rear end.

2. The point tap according to claim 1, characterized in that the twist angle or inclination angle of the primary groove is between 1° and 7°.

3. A point tap as claimed in claim 1 or 2, characterized in that the connection between the primary groove and the secondary groove is positioned opposite the first complete crest at the most distal end of the complete crest portion.

4. The point tap according to claim 1, wherein the point tap is a right-hand blade that rotates clockwise when viewed from the rear end in the axial direction, the secondary grooves are left-handed or inclined in the direction of left-handed rotation relative to the axial direction, and the primary grooves are right-handed or inclined in the direction of right-handed rotation relative to the axial direction.

5. The point tap according to claim 1, wherein the point tap is a left-handed blade that rotates left when viewed from the rear end side in the axial direction, the secondary grooves are right-handed helical or inclined in the direction of right-handed rotation relative to the axial direction, and the primary grooves are left-handed helical or inclined in the direction of left-handed rotation relative to the axial direction.

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