Cutting tools

Abstract

A cutting tool according to one embodiment of the present disclosure includes a shank and two or more major cutting edge portions. The shank extends along a central axis. The shank has an outer peripheral surface. The outer peripheral surface surrounds the central axis. The two or more major cutting edge portions are arranged spirally on the outer peripheral surface. The major cutting edge portion has a major cutting edge. The major cutting edge has a helix angle. In a direction along the central axis, the major cutting edge portion has at least one or more first nick portions and one or more second nick portions in a portion from the center of the region within ±30% of the cutting edge length of the region. The major cutting edge portions are formed in the region. The first nick portion and the second nick portion have helix angles in opposite directions to the helix angle. The relationship between the first nick portion and the second nick portion satisfies at least one of a first condition and a second condition. The first condition is that the width of the first nick portion is different from the width of the second nick portion. The second condition is that the depth of the first nick portion is different from the depth of the second nick portion.

Description

Technical Field

[0001] This disclosure relates to a cutting tool.

Background Art

[0002] Conventionally, a cutting tool is known that includes a rotatable body, a main cutting edge having a twist angle on the outer periphery of the body, and a nick-shaped cutting edge arranged with a reverse twist angle with respect to the twist angle of the main cutting edge (see, for example, Japanese Patent Application Laid-Open No. 2011-20248).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] A cutting tool according to an aspect of this disclosure includes a shaft portion and at least two or more main cutting edge portions. The shaft portion extends along a central axis. The shaft portion has an outer peripheral surface. The outer peripheral surface surrounds the central axis. The two or more main cutting edge portions are spirally arranged on the outer peripheral surface. The main cutting edge portion has a main cutting edge. The main cutting edge has a twist angle. In the direction along the central axis, in a portion within ±30% of the blade length of the region from the center of the region, the main cutting edge portion has at least one or more first nick portions and second nick portions. The main cutting edge portion is formed in the region. The first nick portion and the second nick portion have a twist angle in the opposite direction to the twist angle. The relationship between the first nick portion and the second nick portion satisfies at least one of the first condition and the second condition. The first condition is the case where the width of the first nick portion is different from the width of the second nick portion. The second condition is the case where the depth of the first nick portion is different from the depth of the second nick portion.

Brief Description of the Drawings

[0005] [Figure 1] FIG. 1 is a plan view of a cutting tool according to Embodiment 1 of the present invention. [Figure 2]Figure 2 is a partially enlarged plan view of region II in Figure 1. [Figure 3] Figure 3 is a cross-sectional view along the line segment III-III in Figure 2. [Figure 4] Figure 4 is a schematic diagram of a partially enlarged cross-section of region IV in Figure 2. [Figure 5] Figure 5 is a partially enlarged plan view showing a modified example 1 of the cutting tool according to this embodiment 1. [Figure 6] Figure 6 is a schematic diagram of a partially enlarged cross-section of region VI in Figure 5. [Figure 7] Figure 7 is a partially enlarged plan view showing a modified example 2 of the cutting tool according to this embodiment 1. [Figure 8] Figure 8 is a schematic diagram of a partially enlarged cross-section of region VIII in Figure 7. [Modes for carrying out the invention]

[0006] [Issues this disclosure aims to address]

[0007] In conventional cutting tools, the number of grooves in the nick-shaped cutting edge differs from the number of cutting edges in the main cutting edge, thereby suppressing vibration of the workpiece and obtaining a workpiece with a good cutting surface. However, there are limits to the suppression of vibration of the workpiece.

[0008] This disclosure was made to solve the problems described above. More specifically, it provides a cutting tool that can suppress vibration of the workpiece during machining.

[0009] [Effects of this disclosure]

[0010] The cutting tool described herein can suppress vibrations of the workpiece during machining.

[0011] [Summary of the Embodiment]

[0012] First, the embodiments of this disclosure will be listed and described.

[0013] (1) A cutting tool according to one aspect of the present disclosure comprises a shaft portion and at least two or more main cutting edge portions. The shaft portion extends along a central axis. The shaft portion has an outer circumferential surface. The outer circumferential surface surrounds the central axis. The two or more main cutting edge portions are arranged spirally on the outer circumferential surface. The main cutting edge portions have main cutting edges. The main cutting edges have a helix angle. In the direction along the central axis, within ±30% of the cutting edge length of the region from the center of the region, the main cutting edge portion has at least one first nick portion and a second nick portion. The main cutting edge portion is formed in the region. The first nick portion and the second nick portion have a helix angle opposite to the helix angle. The relationship between the first nick portion and the second nick portion satisfies at least one of the first and second conditions. The first condition is that the width of the first nick portion is different from the width of the second nick portion. The second condition is that the depth of the first nick portion is different from the depth of the second nick portion.

[0014] (2) In the cutting tool described in (1) above, the first condition is that the width of the first nick portion may be 2 times or more but 10 times or less the width of the second nick portion. The second condition is that the depth of the first nick portion may be 2 times or more but 15 times or less the depth of the second nick portion.

[0015] (3) In the cutting tool described in (1) or (2) above, the cross-sectional area of ​​the first nick portion may be 5 times or more and 120 times or less the cross-sectional area of ​​the second nick portion.

[0016] (4) In the cutting tools described in (1) to (3) above, the number of main cutting edges may be greater than the number of first nicks contained in each of the main cutting edges.

[0017] (5) In the cutting tools described in (1) to (4) above, the helix angle of the main cutting edge may be 30° or more and 50° or less. The helix angle in the opposite direction to the helix angle of the first nick and the second nick may be 30° or more and 50° or less.

[0018] (6) In the cutting tool according to (1) to (5) above, the main cutting edge portion may include at least two or more first nick portions. The second nick portion may be disposed at an intermediate position between the two first nick portions.

[0019] (7) The cutting tool according to (1) to (6) above may be coated with diamond.

[0020] [Details of Embodiment]

[0021] Details of the embodiment of the present disclosure will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant descriptions will not be repeated.

[0022] (Embodiment 1)

[0023] <Configuration of Cutting Tool 1>

[0024] FIG. 1 is a plan view of a cutting tool 1 according to the present embodiment. FIG. 2 is a partially enlarged plan view of region II in FIG. 1. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. FIG. 4 is a partially enlarged cross-sectional schematic view of region IV in FIG. 2.

[0025] As shown in FIGS. 1 to 4, a cutting tool 1 according to an aspect of the present disclosure is a tool for cutting an FRP (Fiber Reinforced Plastic) material such as carbon fiber reinforced plastic, and mainly includes a shaft portion 30 and at least two or more main cutting edge portions 11. In the present embodiment, the number of the main cutting edge portions 11 is 5. The shape of the shaft portion (30) is substantially cylindrical. The shaft portion 30 extends along the central axis R. The shaft portion 30 has a tip surface 2a, a rear end surface 2b, and an outer peripheral surface 2. The rear end surface 2b is located on the side opposite to the tip surface 2a. The outer peripheral surface 2 is a surface that connects the tip surface 2a and the rear end surface 2b. That is, the outer peripheral surface 2 surrounds the central axis R. The shaft portion 30 is rotatable about the central axis R.

[0026] The shaft portion 30 further includes a shank portion 20 and a cutting portion 10. The cutting portion 10 has a front end surface 2a. The shank portion 20 has a rear end surface 2b. In other words, the cutting portion 10 is connected to the shank portion 20. In Figure 1, the blade length W of the cutting portion 10 is the distance in the first direction X from the front end surface 2a to the end of the main cutting edge portion 11 on the rear end surface 2b side, assuming that the direction in which the central axis R extends is the first direction X. The front end surface 2a and the rear end surface 2b are surfaces perpendicular to the central axis R. In other words, the front end surface 2a and the rear end surface 2b are surfaces perpendicular to the outer circumferential surface 2. The cutting diameter is, for example, 10 mm. The cutting diameter may be, for example, 2 mm or more and 20 mm or less, or 3 mm.

[0027] In the cutting section 10, five main cutting edge sections 11 are formed on the outer circumferential surface 2. The main cutting edge sections 11 are arranged spirally on the outer circumferential surface 2. As shown in Figure 3, the main cutting edge section 11 has a main rake face 11b, a main relief face 11c, and a main cutting edge 11a. The main cutting edge 11a is positioned on the outer circumferential surface 2. The main rake face 11b is formed to extend from the main cutting edge 11a in the direction toward the central axis R. The main relief face 11c is located on the opposite side of the main rake face 11b when viewed from the main cutting edge 11a. The main rake face 11b is connected to the main relief face 11c via the main cutting edge 11a.

[0028] The main cutting edge 11a has a main helix angle θ1. As shown in Figure 1, in a plan view taken from a direction perpendicular to the central axis R, the main helix angle θ1 is the narrowest angle between the tangent to the main cutting edge 11a and the central axis R at the point where the main cutting edge 11a intersects with the central axis R.

[0029] As shown in Figures 2 and 4, the first nick section 13 has a first nick rake face 13b, a first nick face 13c, a first nick cutting edge 13a, and a first nick connector 13e. The first nick rake face 13b and the first nick face 13c are connected to the main rake face 11b and the main flank face 11c, respectively. The first nick rake face 13b is connected to the main flank face 11c via the first nick cutting edge 13a. The first nick face 13c is connected to the main flank face 11c via the first nick connector 13e. The main cutting edge 11a and the first nick cutting edge 13a intersect at a first intersection p1. The first nick connector 13e and the main cutting edge 11a intersect at a third intersection p3. That is, as shown in Figure 3, the first intersection p1 is located on the outer circumferential surface 2. The third intersection p3 is located on the outer circumferential surface 2.

[0030] Region IV shown in Figure 2 is the cross-sectional region of the main cutting edge portion 11, cut from a line segment along the main cutting edge 11a in a direction perpendicular to the central axis R. In other words, region IV is the cross-sectional region of the main cutting edge portion 11 that includes the first intersection p1, the second intersection p2, the third intersection p3, and the fourth intersection p4. Figure 4 is a partially enlarged schematic cross-sectional view of the cross-sectional region of the main cutting edge portion 11 in region IV. The schematic cross-sectional view shown in Figure 4 schematically shows the main cutting edge portion 11 including the first nick portion 13 and the second nick portion 14, which will be described later. The actual main cutting edge 11a is arranged in a helical shape and is therefore curved, but in Figure 4, the main cutting edge 11a is shown as a straight line for explanatory purposes. Also, the vertical direction in Figure 4 indicates the radial direction around the central axis R of the cutting tool 1.

[0031] As shown in Figure 4, the first nick rake face 13b and the first nick face 13c are formed to extend from the main cutting edge 11a in the direction of the central axis R. The first nick rake face 13b and the first nick face 13c are connected via the first nick base 13d. The first nick base 13d is the part of the first nick portion 13 closest to the central axis R. In other words, in the first nick portion 13, the first nick base 13d is the point furthest from the outer surface 2 in the direction of the central axis R. The distance from the outer surface 2 to the first nick base 13d is the depth h1. As shown in Figure 4, the width w1 of the first nick portion 13 is the length of the line segment connecting the first intersection p1 and the third intersection p3 of the first nick portion 13. The cross-sectional area A1 of the first nick portion 13 is the area of ​​the region enclosed by the straight line connecting the first intersection p1 and the third intersection p3 shown in Figure 4, the first nick rake face 13b, and the first nick face 13c. The width w1 of the first nick portion 13 may be, for example, 0.35 mm or more and 4.2 mm or less. The depth h1 of the first nick portion 13 may be, for example, 0.1 mm or more and 3.4 mm or less.

[0032] The first nick cutting edge 13a has a reverse helix angle θ2. As shown in Figure 1, in a plan view taken from a direction perpendicular to the central axis R, the reverse helix angle θ2 is the narrowest angle between the tangent to the first nick cutting edge 13a and the central axis R at the point where the central axis R and the first nick cutting edge 13a intersect. As shown in Figure 1, in a plan view, the reverse helix angle θ2 of the first nick cutting edge 13a is a helix angle in the opposite direction to the main helix angle θ1 of the main cutting edge 11a when viewed from the central axis R. Thus, the main cutting edge portion 11 has a first nick portion 13. Having such a first nick portion 13 suppresses the generation of vibration and reduces cutting resistance when cutting the workpiece.

[0033] Here, a feature of the cutting tool 1 according to this embodiment 1 is that, as shown in Figures 1 to 4, the main cutting edge portion 11 of the cutting tool 1 has a second nick portion 14. Specifically, as shown in Figure 1, in each of the main cutting edge portions 11, the second nick portion 14 is arranged so as to be sandwiched between two first nick portions 13 in the first direction X. The second nick portion 14 may be arranged, for example, at an intermediate position between the two first nick portions 13. As long as the strength of the cutting tool 1 is ensured, the second nick portion 14 may be arranged, for example, at a position other than the intermediate position between the two first nick portions 13. For example, multiple (for example, two) second nick portions 14 may be provided between the two first nick portions 13.

[0034] As shown in Figure 4, the second nick portion 14 has a different shape from the first nick portion 13. Specifically, the relationship between the first nick portion 13 and the second nick portion 14 satisfies at least one of the first and second conditions. The first condition is that the width w1 of the first nick portion 13 is different from the width w2 of the second nick portion 14. The second condition is that the depth h1 of the first nick portion 13 is different from the depth h2 of the second nick portion 14. By providing the second nick portion 14, which has a different shape from the first nick portion 13, on the main cutting edge portion 11, vibrations generated during cutting can be significantly suppressed. As a result, the finish quality of the machined surface of the workpiece cut by the cutting tool 1 is improved.

[0035] As shown in Figure 1, the second nick portion 14 is located within the first region A. The first region A is the portion within ±30% of the blade length W of region B from the center C of region B where the main cutting edge portion 11 is formed, in the first direction X. Specifically, region B where the main cutting edge portion 11 is formed is the region from the tip surface 2a of the cutting portion 10 to a position at a distance of blade length W in the first direction X. The center C is a position at a distance of half the blade length W from the tip surface 2a in the first direction X. In other words, if we take the direction in which the tip surface 2a is located in the first direction X as positive, with the center C as the reference point, then the tip surface 2a is the surface that is advanced from the center C in the first direction X by a distance of +50% of the blade length W of the cutting portion 10. From a different perspective, the first region A is the region within ±30% of the blade length W of the cutting portion 10 from the center C in the first direction X, with the center C as the reference point. In other words, the second nick portion 14 is positioned on the outer circumferential surface 2 of the cutting portion 10 in the first region A. The second nick portion 14 may also be formed in regions other than the first region A within region B where the main cutting edge portion 11 is formed. However, due to manufacturing issues, it may be more difficult to form the second nick portion 14 closer to the tip surface 2a and the shank portion 20.

[0036] As shown in Figures 2 and 4, the second nick section 14 has a second nick rake face 14b, a second nick face 14c, a second nick cutting edge 14a, and a second nick connector 14e. The second nick rake face 14b and the second nick face 14c are connected to the main rake face 11b and the main relief face 11c, respectively. The second nick rake face 14b is connected to the main relief face 11c via the second nick cutting edge 14a. The second nick face 14c is connected to the main relief face 11c via the second nick connector 14e. The main cutting edge 11a and the second nick cutting edge 14a intersect at the second intersection p2. The second nick connector 14e and the main cutting edge 11a intersect at the fourth intersection p4. That is, as shown in Figure 3, the second intersection p2 is located on the outer circumferential surface 2. The fourth intersection p4 is located on the outer circumferential surface 2.

[0037] As shown in Figure 4, the second nick rake face 14b and the second nick face 14c are formed to extend from the main cutting edge 11a in the direction of the central axis R. The second nick rake face 14b and the second nick face 14c are connected via the second nick base 14d. The second nick base 14d is the part of the second nick 14 closest to the central axis R. In other words, in the second nick 14, the second nick base 14d is the point furthest from the outer surface 2 in the direction of the central axis R. The distance from the outer surface 2 to the second nick base 14d is the depth h2. As shown in Figure 4, the width w2 of the second nick 14 is the length of the line segment connecting the second intersection p2 and the fourth intersection p4 of the second nick 14. The cross-sectional area A2 of the second nick 14 is the area of ​​the region enclosed by the straight line connecting the second intersection p2 and the fourth intersection p4 shown in Figure 4, the second nick rake face 14b, and the second nick opposite face 14c.

[0038] The width w1 and depth h1 of the first nick 13, and the width w2 and depth h2 of the second nick 14 are measured from the profile shapes of the first nick 13 and the second nick 14. The profile shapes of the first nick 13 and the second nick 14 may also be measured using a non-contact three-dimensional measuring machine manufactured by Bruker Alicona. The cross-sectional area A1 of the first nick 13 and the cross-sectional area A2 of the second nick 14 can be calculated from the profile shapes of the first nick 13 and the second nick 14 as described above.

[0039] The second nick cutting edge 14a has a reverse helix angle θ3. As shown in Figure 1, in a plan view taken from a direction perpendicular to the central axis R, the reverse helix angle θ3 is the narrowest angle between the tangent to the second nick cutting edge 14a and the central axis R at the point where the central axis R and the second nick cutting edge 14a intersect. As shown in Figure 1, in a plan view, the reverse helix angle θ3 of the second nick cutting edge 14a is a helix angle in the opposite direction to the main helix angle θ1 of the main cutting edge 11a when viewed from the central axis R. Thus, the main cutting edge portion 11 has a second nick portion 14.

[0040] In each of the main cutting edge portions 11, the number of first nick portions 13 may be, for example, one or more. The number of first nick portions 13 may be two or three. Furthermore, it is preferable that the number of first nick portions 13 contained in each of the main cutting edge portions 11 is smaller than the number of main cutting edge portions 11 that the cutting tool 1 has. From a different perspective, it is preferable that the number of main cutting edge portions 11 is greater than the number of first nick portions 13 contained in each of the main cutting edge portions 11. By making the number of main cutting edge portions 11 and the number of first nick portions 13 different in this way, the first nick portions 13 can be easily arranged so that they do not overlap in the rotational direction of the cutting tool 1, thereby preventing the occurrence of areas on the cutting surface of the workpiece that are not cut when the cutting tool 1 rotates once while cutting the workpiece.

[0041] The number of second nicks 14 on each of the main cutting edges 11 may be, for example, one or more. The number of second nicks 14 on each of the main cutting edges 11 may be two or three. If the number of first nicks 13 and second nicks 14 on each of the main cutting edges 11 is large, the generation of vibration will be further suppressed and the cutting resistance will be further reduced when the workpiece is cut by the cutting tool 1.

[0042] However, providing the second nick portion 14 may reduce the strength and tool life of the main cutting edge portion 11. Therefore, the cutting tool 1 may be coated with diamond. In this way, the strength and tool life of the cutting tool 1 can be improved.

[0043] <Effects and Effects>

[0044] A cutting tool 1 according to this disclosure comprises a shaft portion 30 and at least two main cutting edge portions 11. The shaft portion 30 extends along a central axis R. The shaft portion 30 has an outer circumferential surface 2. The outer circumferential surface 2 surrounds the central axis R. The two or more main cutting edge portions 11 are arranged spirally on the outer circumferential surface 2. Each main cutting edge portion 11 has a main cutting edge 11a. The main cutting edge 11a has a helix angle θ1. In the direction along the central axis R, within ±30% of the blade length W of region B from the center C of region B, the main cutting edge portion 11 has at least one first nick portion 13 and a second nick portion 14. The main cutting edge portion 11 is formed in region B. The first nick portion 13 and the second nick portion 14 have helix angles θ2 and θ3 opposite to the helix angle θ1. The relationship between the first nick 13 and the second nick 14 satisfies at least one of the first and second conditions. The first condition is that the width w1 of the first nick 13 is different from the width w2 of the second nick 14. The second condition is that the depth h1 of the first nick 13 is different from the depth h2 of the second nick 14.

[0045] This method significantly suppresses vibrations generated during cutting. As a result, the finish of the machined surface of the workpiece cut by the cutting tool 1 is greatly improved.

[0046] In the above cutting tool 1, the first condition is that the width w1 of the first nick portion 13 may be 2 times or more but 10 times or less the width w2 of the second nick portion 14. The second condition is that the depth h1 of the first nick portion 13 may be 2 times or more but 15 times or less the depth h2 of the second nick portion 14.

[0047] This method significantly suppresses vibrations generated during cutting and ensures adequate chip evacuation. As a result, chips do not clog the second nick portion 14 during cutting, and the finish quality of the machined surface of the workpiece is greatly improved.

[0048] In the cutting tool 1 described above, the cross-sectional area A1 of the first nick portion 13 may be 5 to 120 times the cross-sectional area A2 of the second nick portion 14. This significantly suppresses vibrations generated during cutting and ensures sufficient chip evacuation. As a result, chips do not clog the second nick portion 14 during cutting, and the finish quality of the machined surface of the workpiece is greatly improved.

[0049] In the cutting tool 1 described above, the number of main cutting edges 11 may be greater than the number of first nick portions 13 contained within each of the main cutting edges 11. In this way, when the cutting tool 1 rotates once during cutting, the generation of uncut material can be suppressed.

[0050] In the cutting tool 1 described above, the helix angle θ1 of the main cutting edge 11a may be 30° or more and 50° or less. The helix angles θ2 and θ3 of the first nick portion 13 and the second nick portion 14, respectively, which are in the opposite direction to the helix angle θ1, may be 30° or more and 50° or less. In this way, as will be described later, the generation of vibration during cutting is suppressed, cutting resistance is reduced, and the finish quality of the machined surface is improved.

[0051] In the cutting tool 1 described above, the main cutting edge portion 11 may include at least two or more first nick portions 13. The second nick portion 14 may be positioned midway between the two first nick portions 13. In this way, the reduction in strength of the main cutting edge portion 11 due to the provision of the second nick portion 14 can be minimized.

[0052] The cutting tool 1 described above may be coated with diamond. This can improve the strength and tool life of the cutting tool 1.

[0053] To verify the effectiveness of the cutting tool 1 according to this embodiment 1 as described above, the following tests were conducted. (Test 1)

[0054] <Target of Examination>

[0055] In Test 1, the finish of the cut surface of the workpiece, chip evacuation, and tool life of the cutting tool 1 were evaluated based on the presence or absence of the second nick portion 14. The test subjects were three types of cutting tools 1, from Sample 1 to Sample 3. The cutting diameter of the cutting tools 1 for Samples 1 to 3 was 10 mm, and the number of main cutting edges 11 was 5. The number of first nick portions 13 in one main cutting edge portion 11 was 6. In Samples 1 and 2, the main cutting edge portion 11 had the first nick portion 13 but not the second nick portion 14. On the other hand, in Sample 3, the main cutting edge portion 11 had both the first nick portion 13 and the second nick portion 14. In Sample 3, the number of second nick portions 14 in the first region A of one main cutting edge portion 11 was 6. The width w1 of the first nick portion 13 of the cutting tool 1 for Sample 2 was smaller than the width w1 of the first nick portion 13 of the cutting tool 1 for Samples 1 and 3. The width W1 of the first nick 13 in Sample 1 and Sample 3 is 2.0 mm, and the depth h1 is 1.5 mm. In Sample 2, the width W1 of the first nick 13 is 1.0 mm, and the depth h1 is 0.6 mm. In Sample 3, the width W2 of the second nick 14 is 0.5 mm, and the depth h2 is 0.3 mm. In this way, the influence of the width w1 of the first nick 13 and the influence of the presence or absence of the second nick 14 were investigated.

[0056] <Test Conditions>

[0057] The workpiece being machined is CFRP (carbon fiber reinforced polymer). The thickness of the CFRP is 6 mm. The cutting conditions were as follows: the rotational speed of cutting tool 1 was 4000 rpm, and the machining speed was 400 mm / min.

[0058] <Result> [Table 1]

[0059] The test results are shown in Table 1. In Table 1, from left to right, the conditions are listed as the width w1 of the first nick 13 and the presence or absence of the second nick 14. The test results are listed as the finish of the cut surface of the workpiece, the chip evacuation performance, and the tool life of the cutting tool 1. In Table 1, A, B, and C indicate the evaluation of each item for the finish of the cut surface, chip evacuation performance, and tool life of the cutting tool 1. B indicates that it is better than C. A indicates that it is better than B. In other words, A indicates the best evaluation result among A, B, and C. In particular, good chip evacuation performance indicates that clogging due to chips is suppressed.

[0060] As can be seen from Table 1, the test results of cutting tool 1 for Sample 1 and Sample 2 show that reducing the width w1 of the first nick reduces the cross-sectional area A1 of the first nick 13, worsening chip evacuation. When chips get stuck in the first nick 13, the cutting resistance of the cutting tool 1 increases, which in turn leads to a decrease in the tool life of the cutting tool 1.

[0061] Test results for cutting tool 1 related to Sample 1 and Sample 3 show that adding a second nick 14 to the main cutting edge 11 in addition to the first nick 13 improves the finish of the cutting surface. This is thought to be because vibrations generated during cutting are reduced, resulting in an improved finish of the cutting surface. By providing the second nick 14, the area for chip evacuation increases, thus improving chip evacuation. As a result, it is thought that the tool life remained good without decreasing despite the provision of the second nick 14. (Exam 2)

[0062] <Target of Examination>

[0063] In Test 2, the finish of the cut surface of the workpiece, the chip evacuation performance, and the tool life of the cutting tool 1 were evaluated based on the shape of the second nick portion 14. The test subjects were 10 types of cutting tools 1, from Sample 4 to Sample 13. In the cutting tool 1 of Sample 4, the main cutting edge portion 11 has a first nick portion 13, but does not have a second nick portion 14. On the other hand, in the cutting tools 1 of Samples 5 to 13, the main cutting edge portion 11 has both a first nick portion 13 and a second nick portion 14. In particular, the effects of changing the width ratio (w1 / w2), depth ratio (h1 / h2), and cross-sectional area ratio (A1 / A2) were investigated in the cutting tools 1 of Samples 5 to 13. The width ratio is the value obtained by dividing the width w1 of the first nick portion 13 by the width w2 of the second nick portion 14. The depth ratio is the value obtained by dividing the depth h1 of the first nick portion 13 by the depth h2 of the second nick portion 14. The cross-sectional area ratio is the value obtained by dividing the cross-sectional area A1 of the first nick portion 13 by the cross-sectional area A2 of the second nick portion 14.

[0064] The cutting diameter of the cutting tool 1 for samples 4 to 10, and the cutting tool 1 for sample 13, is 10 mm. The cutting diameter of the cutting tool 1 for samples 11 and 12 is 3 mm. In the cutting tool 1 for samples 4 to 6, the main helix angle θ1 of the main cutting edge 11a is 45°. On the other hand, in each of the cutting tool 1 for samples 7 to 10, the main helix angle θ1 of the main cutting edge 11a is different, ranging from 20° to 50°. In the cutting tool 1 for samples 4 to 12, the cutting tool 1 is diamond coated. On the other hand, in the cutting tool 1 for sample 13, the cutting tool 1 is not diamond coated. Furthermore, for the cutting tool 1 for samples 4 to 10, and the cutting tool 1 for sample 13, which have a cutting diameter of 10 mm, the number of main cutting edge portions 11 is 5, and the number of first nick portions 13 and second nick portions 14 in one main cutting edge portion 11 is 6, each. On the other hand, for the cutting tools 1 of samples 11 and 12, which have a cutting diameter of 3 mm, the number of main cutting edges 11 is 3, and the number of first nicks 13 and second nicks 14 in one main cutting edge 11 is 4, each.

[0065] <Test Conditions>

[0066] The workpiece being machined is CFRP (carbon fiber reinforced polymer). The thickness of the CFRP is 6 mm. The cutting conditions were as follows: the rotational speed of cutting tool 1 was 8000 rpm, and the machining speed was 1600 mm / min.

[0067] <Result> [Table 2]

[0068] The test results are shown in Table 2. In Table 1, the conditions listed from left to right are the width ratio, depth ratio, cross-sectional area ratio, principal helix angle θ1, and presence or absence of diamond coating. The test results are the finish of the cut surface of the workpiece, chip evacuation performance, and tool life of the cutting tool 1. In Table 2, A, B, C, and D indicate the evaluation for each item: finish of the cut surface, chip evacuation performance, and tool life of the cutting tool 1. C indicates a better result than D. B indicates a better result than C. A indicates a better result than B. In other words, A indicates the best evaluation result among A, B, and C.

[0069] As can be seen from Table 2, the finish of the cutting surface of cutting tool 1 for samples 5 to 13 is improved compared to the finish of the cutting surface of cutting tool 1 for sample 4. The chip evacuation performance of cutting tool 1 for samples 5 to 13 is also improved compared to the chip evacuation performance of cutting tool 1 for sample 4. This indicates that by adding a second nick portion 14 to the main cutting edge portion 11 in addition to the first nick portion 13, both the finish of the cutting surface and the chip evacuation performance are improved. In this respect, it can be said that Test 2 yielded the same results as Test 1. In particular, from the test results of cutting tool 1 for samples 5 and 6, it was found that as the width ratio and depth ratio increase, the cross-sectional area ratio increases, so not only the finish of the cutting surface but also the chip evacuation performance is significantly improved.

[0070] The width ratio of the cutting tool 1 in Samples 7 and 9 is 11 times. As a result, the length of the main cutting edge 11a becomes insufficient, and the finish of the cutting surface deteriorates. Therefore, a width ratio of 10 times or less is preferable. The cutting tool 1 in Sample 8 has a weak twist design with a main helix angle θ1 of 30° for the main cutting edge, but the finish of the cutting surface and chip evacuation are improved.

[0071] The cutting tool 1 in sample 10 has a depth ratio of 17. As a result, the rigidity of the cutting tool 1 is low. Therefore, it is preferable that the depth ratio be 16 or less. From the above results, it is preferable that the width w1 of the first nick portion 13 is 2 times or more and 10 times or less the width w2 of the second nick portion 14. It is preferable that the depth h1 of the first nick portion 13 is 2 times or more and 15 times or less the depth h2 of the second nick portion 14. From another point of view, it is preferable that the cross-sectional area A1 of the first nick portion 13 is 5 times or more and 120 times or less the cross-sectional area A2 of the second nick portion 14.

[0072] Test results for cutting tool 1 with samples 11 and 12, which have a cutting diameter of 3 mm, show that by providing a second nick portion 14 on the main cutting edge portion 11, the finish of the cutting surface and chip evacuation are improved, similar to the cutting tool 1 with a cutting diameter of 10 mm.

[0073] However, providing a second nick portion 14 on the main cutting edge portion 11 may reduce the tool life of the cutting tool 1. From the test results of the cutting tool 1 for Sample 6 and Sample 13, it can be seen that the tool life of the cutting tool 1 is significantly improved by coating it with diamond.

[0074] (Modification 1 of Embodiment 1)

[0075] <Structure of the variation>

[0076] Figure 5 is a partially enlarged plan view showing a modified example 1 of the cutting tool 1 according to Embodiment 1. Figure 5 corresponds to Figure 2. Figure 6 is a partially enlarged schematic cross-sectional view of region VI in Figure 5. Figure 6 corresponds to Figure 4.

[0077] The cutting tool 1 shown in Figures 5 and 6 has basically the same configuration as the cutting tool 1 shown in Figures 1 to 4, but differs in that two second nick portions 14 are formed between two first nick portions 13. Specifically, as shown in Figure 6, the two second nick portions 14 are formed on the main cutting edge portion 11 so as to be sandwiched between the two first nick portions 13. The number of second nick portions 14 is not limited to two. For example, three second nick portions 14 may be formed on the main cutting edge portion 11 so as to be sandwiched between the two first nick portions 13. By forming multiple second nick portions 14 between the two first nick portions 13 in this way, vibrations generated during cutting can be further suppressed. As a result, the finish quality of the machined surface of the workpiece cut with the cutting tool 1 is further improved.

[0078] (Modification 2 of Embodiment 1)

[0079] <Structure of the variation>

[0080] Figure 7 is a partially enlarged plan view showing a modified example 2 of the cutting tool 1 according to Embodiment 1. Figure 7 corresponds to Figure 2. Figure 8 is a partially enlarged schematic cross-sectional view of region VIII in Figure 7. Figure 8 corresponds to Figure 4.

[0081] The cutting tool 1 shown in Figures 7 and 8 basically has the same configuration as the cutting tool 1 shown in Figures 1 to 4, but differs in that the width w2 of the second nick portion 14 is greater than the width w1 of the first nick portion 13. To ensure chip evacuation, the depth h1 of the first nick portion 13 should be greater than the depth h2 of the second nick portion 14. Alternatively, the width w1 of the first nick portion 13 should be greater than the width w2 of the second nick portion 14. Specifically, from the results of the above-described test 2, the relationship between the first nick portion 13 and the second nick portion 14 satisfies at least one of the first and second conditions. The first condition is that the width w1 of the first nick portion 13 is between 2 and 10 times the width w2 of the second nick portion 14. The second condition is that the depth h1 of the first nick portion 13 is between 2 and 15 times the depth h2 of the second nick portion 14.

[0082] In this way, the cutting tool 1 can ensure chip evacuation while suppressing vibrations generated during cutting.

[0083] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The basic scope of the invention is indicated by the claims rather than by the embodiments described above, and all modifications within the meaning and scope of the claims are intended to be included. [Explanation of Symbols]

[0084] 1 Cutting tool, 2 Outer surface, 2a Front surface, 2b Rear surface, 10 Cutting section, 11 Main cutting edge section, 11a Main cutting edge, 11b Main rake face, 11c Main relief face, 13 First nick section, 13a First nick cutting edge, 13b First nick rake face, 13c Opposite side of first nick, 13d Bottom of first nick, 13e First nick connection section, 14 Second nick section, 14a Second nick cutting edge, 14b Second nick rake face, 14c Opposite side of second nick, 14d Bottom of second nick, 14e Second nick connection section, 20 Shank section, 30 Axis section, A First region, A1, A2 Cross-sectional area, B Region, C Center, R Central axis, W Blade length, X First direction, h1, h2 Depth, w1, w2 Width, p1 First intersection, p2 2nd intersection, p3 3rd intersection, p4 4th intersection.

Claims

1. A shaft portion having an outer circumferential surface extending along a central axis and surrounding the central axis; At least two or more main cutting edges are arranged in a spiral on the outer circumferential surface, The main cutting edge portion has a main cutting edge having a helix angle, In a direction along the central axis, from the center of the region in which the main cutting edge portion is formed, in a portion within ±30% of the cutting edge length of the region, The main cutting edge portion includes at least one first nick portion and one second nick portion having a helix angle in an opposite direction to the helix angle, The first condition is that the width of the first nick portion is different from the width of the second nick portion, The second condition is that when the depth of the first nick portion is different from the depth of the second nick portion, A cutting tool, wherein the relationship between the first nick portion and the second nick portion satisfies at least one of the first condition and the second condition.

2. The first condition is that the width of the first nick portion is equal to or greater than 2 times and equal to or less than 10 times the width of the second nick portion, The cutting tool according to claim 1 , wherein the second condition is that the depth of the first nick portion is between 2 and 15 times the depth of the second nick portion.

3. The cutting tool according to claim 1 or 2, wherein a cross-sectional area of ​​the first nick portion is 5 to 120 times a cross-sectional area of ​​the second nick portion.

4. The cutting tool according to claim 1 or 2, wherein the number of the main cutting edge portions is greater than the number of the first nick portions included in each of the main cutting edge portions.

5. The helix angle of the main cutting edge is equal to or greater than 30° and equal to or less than 50°, 3. The cutting tool according to claim 1, wherein the twist angle in the opposite direction to the twist angle in each of the first nick portion and the second nick portion is greater than or equal to 30° and less than or equal to 50°.

6. The main cutting edge portion includes at least two of the first nick portions, The cutting tool according to claim 1 or 2, wherein the second nick portion is disposed at an intermediate position between two of the first nick portions.

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