Cutting tools

Abstract

The cutting tool comprises a shaft portion. The shaft portion has a flank. The shaft portion has a main groove portion and a nick portion. The main groove portion includes a first main groove and a second main groove. Each of the first and second main grooves includes a main rake face and a main face. The main face faces the main rake face. Each of the main rake face of the first main groove and the main face of the second main groove is connected to the flank. The nick portion includes a secondary rake face. The ridge between the flank face and the main rake face constitutes a main cutting edge having a main helix angle. The ridge between the flank face and the secondary rake face constitutes a secondary cutting edge. The secondary cutting edge has a reverse helix angle opposite to the main helix angle. The flank angle at the ridge between the flank face and the main rake face of the first main groove is defined as the first flank angle. The flank angle at the ridge between the flank face and the main face of the second main groove is defined as the second flank angle. The second escape angle is larger than the first escape angle.

Description

[[Technical Field]]

[0001] The present disclosure relates to a cutting tool. [[Background Art]]

[0002] As disclosed in Patent Document 1, there is known a cutting tool including a main cutting edge having a helix angle, and nick-shaped cutting edges arranged at a reverse helix angle relative to the helix angle of the main cutting edge. [[Prior Art Documents]] [[Patent Documents]]

[0003] [[Patent Document 1]] Japanese Unexamined Patent Application Publication No. 2011-20248 [[Summary of the Invention]]

[0004] The cutting tool according to the present disclosure includes a shaft portion. The shaft portion has a flank. A main groove portion and a nick portion are formed in the shaft portion. The main groove portion includes a first main groove and a second main groove. Each of the first main groove and the second main groove includes a main rake face and a main opposing face. The main opposing face faces the main rake face. Each of the main rake face of the first main groove and the main opposing face of the second main groove is continuous with the flank. The nick portion includes a sub-rake face. A ridge line between the flank and the main rake face constitutes a main cutting edge having a main helix angle. A ridge line between the flank and the sub-rake face constitutes a sub-cutting edge. The sub-cutting edge has a reverse helix angle in a direction opposite to the main helix angle. A clearance angle at the ridge line between the flank and the main rake face of the first main groove is defined as a first clearance angle. A clearance angle at the ridge line between the flank and the main opposing face of the second main groove is defined as a second clearance angle. The second clearance angle is larger than the first clearance angle. [[Brief Description of the Drawings]]

[0005] [Figure 1] FIG. 1 is a perspective view of the cutting tool according to Embodiment 1. [Figure 2] FIG. 2 is a front view of the cutting tool according to Embodiment 1. [Figure 3]Figure 3 is a partially enlarged front view of area III in Figure 2. [Figure 4] Figure 4 is a cross-sectional view along the line segment IV-IV in Figure 3. [Figure 5] Figure 5 is a schematic diagram showing the positional relationship of the nicks provided on the main rake face. [Figure 6] Figure 6 is a partially enlarged cross-sectional view showing the first relief angle. [Figure 7] Figure 7 is a partially enlarged cross-sectional view showing the second relief angle. [Modes for carrying out the invention]

[0006] However, there is room for improvement in suppressing the vibrations of the workpiece that occur when it is being machined.

[0007] The purpose of this disclosure is to provide a cutting tool that suppresses vibration of the workpiece. According to this disclosure, it is possible to provide a cutting tool that suppresses vibration of the workpiece.

[0008] First, the embodiments of this disclosure will be listed and described. (1) The cutting tool according to the present disclosure comprises a shaft portion. The shaft portion has a flank surface. The shaft portion has a main groove portion and a nick portion. The main groove portion includes a first main groove and a second main groove. Each of the first and second main grooves includes a main rake face and a main face. The main face faces the main rake face. Each of the main rake face of the first main groove and the main face of the second main groove is connected to the flank surface. The nick portion includes a secondary rake face. The ridge between the flank surface and the main rake face constitutes a main cutting edge having a main helix angle. The ridge between the flank surface and the secondary rake face constitutes a secondary cutting edge. The secondary cutting edge has a reverse helix angle in the opposite direction to the main helix angle. The flank angle at the ridge between the flank surface and the main rake face of the first main groove is defined as the first flank angle. The flank angle at the ridge between the flank surface and the main face of the second main groove is defined as the second flank angle. The second escape angle is larger than the first escape angle.

[0009] According to the cutting tool described herein, the second relief angle becomes larger than the first relief angle, which increases the length of the secondary cutting edge and suppresses vibrations of the workpiece that occur during cutting. As a result, the finish quality of the machined surface of the workpiece cut with the cutting tool is improved.

[0010] (2) In the case of the cutting tool described in (1) above, the first relief angle may be greater than 0° and 6° or less. The second relief angle may be greater than 6° and 12° or less. In this way, vibrations of the cutting tool generated during cutting are suppressed by the process damping effect. As a result, chipping of the cutting tool is suppressed.

[0011] (3) In the case of the cutting tool according to (1) or (2) above, the second relief angle may be 1.5 times or more and 2 times or less of the first relief angle. In this way, while suppressing the increase in cutting resistance, vibration of the cutting tool generated during cutting is suppressed by the process damping effect.

[0012] (4) In the case of a cutting tool according to any of (1) to (3) above, the main groove portion may include multiple main grooves. The nick portion may include multiple nicks. Multiple nicks may be arranged to constitute multiple nick grooves. The number of main grooves may be greater than the number of nick grooves. In this way, the occurrence of areas in the workpiece that are not cut is reduced.

[0013] (5) With respect to any of the cutting tools described in (1) to (4) above, the principal helix angle may be 10° or more and 25° or less. The reverse helix angle may be 30° or more and 45° or less. In this way, vibrations of the workpiece generated during cutting are suppressed.

[0014] The embodiments of this disclosure will be described in detail 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.

[0015] (Embodiment 1) <Cutting tool configuration> FIG. 1 is a perspective view of a cutting tool 100 according to Embodiment 1. FIG. 2 is a front view of the cutting tool 100 according to Embodiment 1.

[0016] As shown in FIG. 1 and FIG. 2, the cutting tool 100 according to the first embodiment is, for example, a tool for cutting a workpiece, and mainly includes a shaft portion 1. The shaft portion 1 extends along a central axis A. The cutting tool 100 is capable of rotating about the central axis A.

[0017] The cutting tool 100 according to the first embodiment may be used for cutting FRP (Fiber Reinforced Plastic) materials such as carbon fiber reinforced plastic as a workpiece, may be used for cutting a thin plate having a thickness of 5 mm or less, for example, and may be used for finish machining a workpiece.

[0018] The shaft portion 1 has a tip end portion 11 and a rear end portion 12. A direction along the central axis A is defined as an axial direction z. The rear end portion 12 is located opposite to the tip end portion 11 in the axial direction z. That is, the shaft portion 1 extends from the rear end portion 12 toward the tip end portion 11.

[0019] The shape of the shaft portion 1 is a columnar shape. As shown in FIG. 2, a direction perpendicular to the axial direction z is defined as a radial direction r. A cutting diameter of the cutting tool 100 according to the first embodiment may be, for example, 2 mm or more and 20 mm or less, or 3 mm or more and 10 mm or less.

[0020] A main groove portion 4 and a nick portion 5 are formed in the shaft portion 1. Specifically, the shaft portion 1 includes a cutting portion 2 and a shank portion 3. The shank portion 3 is connected to the cutting portion 2. The main groove portion 4 is provided in the cutting portion 2, and is formed in a spiral shape from the tip end portion 11 toward the shank portion 3. The cutting tool 100 is fixed by holding the shank portion 3 with a chuck or the like.

[0021] As shown in Fig. 1, the main flute portion 4 includes a plurality of main flutes 40. The number of the main flutes 40 is 12. The nick portion 5 includes a plurality of nicks 50. The plurality of nicks 50 are arranged so as to form a plurality of nick flutes 17. The main flute portion 4 and the nick flutes 17 are formed in a spiral shape.

[0022] Fig. 3 is a partially enlarged front view of region III in Fig. 2. Fig. 4 is a cross-sectional view taken along line IV-IV in Fig. 3. The shaft portion 1 has a flank 10. The flank 10 is disposed on the cutting portion 2.

[0023] The main flute portion 4 includes, for example, a first main flute 40a and a second main flute 40b. Each of the main flutes of the main flute portion 4 (each of the first main flute 40a and the second main flute 40b) includes a main rake face 41 and a main opposing face 42. The main opposing face 42 faces the main rake face 41. As shown in Fig. 4, in the main flute portion 4, the main rake face 41 and the main opposing face 42 are connected at the position closest to the central axis A in the radial direction r.

[0024] As shown in Fig. 3, the main rake face 41 of the first main flute 40a is connected to the flank 10. A ridge between the flank 10 and the main rake face 41 constitutes a main cutting edge 14. The main cutting edge 14 has a main helix angle θ1. When viewed from a direction perpendicular to the central axis A, the main helix angle θ1 is the narrow angle formed between the tangent to the main cutting edge 14 at the intersection point of the central axis A and the main cutting edge 14 and the central axis A.

[0025] If the main helix angle θ1 is less than 10°, chatter may occur during cutting. If the main helix angle θ1 exceeds 25°, the force with which the main cutting edge 14 lifts the work material during cutting increases, which may lead to increased vibration of the work material. Therefore, the main helix angle θ1 may be 10° or more and 25° or less.

[0026] As shown in Fig. 4, the main cutting edge 14 is located on the outermost peripheral surface 16 of the cutting portion 2. The outermost peripheral surface 16 is an imaginary surface of the cutting portion 2 that is farthest from the central axis A in the radial direction r.

[0027] The main face 42 of the second main groove 40b is connected to the flank face 10 at a position opposite to the ridge (main cutting edge 14) between the flank face 10 and the main rake face 41 of the first main groove 40a. In other words, the main face 42 of the second main groove 40b is positioned behind the ridge (main cutting edge 14) between the flank face 10 and the main rake face 41 of the first main groove 40a in the rotational direction of the cutting tool 100. Thus, the flank face 10 is sandwiched between the pair of main grooves 40 (first main groove 40a and second main groove 40b) in the rotational direction of the cutting tool 100.

[0028] Figure 5 is a schematic diagram showing the positional relationship of the nicks 5 provided on the main rake face 41. The schematic diagram shown in Figure 5 schematically shows the main cutting edge 14 including the first nick 50a and the second nick 50b. In reality, the main cutting edge 14 extends spirally on the outermost surface 16, so the shape of the main cutting edge 14 is curved, but in Figure 5 it is shown as a straight line for illustrative purposes.

[0029] The nick portion 5 includes a first nick 50a and a second nick 50b. Each of the first nick 50a and the second nick 50b is formed to open, for example, to the main rake face 41 of the first main groove 40a and the main face 42 of the second main groove 40b. In the direction in which the main cutting edge 14 extends, the second nick 50b is positioned adjacent to the first nick 50a.

[0030] Each of the nick sections 5 (first nick 50a and second nick 50b) includes a secondary rake face 51 and a secondary face 52. The secondary face 52 faces the secondary rake face 51. In the nick section 5, the secondary rake face 51 and the secondary face 52 are connected to the central axis A at the closest position in the radial direction r.

[0031] The secondary rake face 51 of the first nick 50a is connected to the flank face 10. The ridge line between the flank face 10 and the secondary rake face 51 constitutes the secondary cutting edge 15. As shown in Figure 3, the secondary cutting edge 15 has a reverse helix angle θ2. Each reverse helix θ2 is a helix angle in the opposite direction to the main helix angle θ1. As shown in Figure 3, when viewed from a direction perpendicular to the central axis A, the reverse helix angle θ2 is the narrowest angle between the tangent of the secondary cutting edge 15 and the central axis A at the point where the secondary cutting edge 15 intersects with the central axis A. At the outermost surface 16, the secondary cutting edge 15 intersects with the main cutting edge 14.

[0032] If the reverse helix angle θ2 is less than 30°, the force with which the secondary cutting edge 15 holds down the workpiece during machining may be insufficient, potentially leading to increased vibration of the workpiece. Therefore, the reverse helix angle θ2 may be between 30° and 45°.

[0033] As shown in Figure 5, the secondary facet 52 of the second nick 50b is connected to the flank surface 10 at a position opposite to the ridge (secondary cutting edge 15) between the secondary rake face 51 of the first nick 50a and the flank surface 10 in the direction in which the main cutting edge 14 extends. In this way, the flank surface 10 is sandwiched between the pair of nicks 50 (first nick 50a and second nick 50b) in the direction in which the main cutting edge 14 extends.

[0034] The sizes of the first nick 50a and the second nick 50b may differ from each other. Specifically, the width w1 of the first nick 50a in the direction in which the main cutting edge 14 extends may differ from the width w2 of the second nick 50b in the direction in which the main cutting edge 14 extends. The width w1 of the first nick 50a may be larger or smaller than the width w2 of the second nick 50b, as shown in Figure 5.

[0035] The depth h1 of the first nick 50a (the distance in the radial direction r from the outermost surface 16 to the bottom of the first nick 50a) may be different from the depth h2 of the second nick 50b (the distance in the radial direction r from the outermost surface 16 to the bottom of the second nick 50b). The depth h1 of the first nick 50a may be greater than or less than the depth h2 of the second nick 50b, as shown in Figure 5.

[0036] The opening area of ​​the first nick 50a (the area of ​​the region enclosed by the outermost surface 16, the secondary rake face 51 of the first nick 50a, and the secondary face 52 of the first nick 50a) may be different from the opening area of ​​the second nick 50b (the area of ​​the region enclosed by the outermost surface 16, the secondary rake face 51 of the second nick 50b, and the secondary face 52 of the second nick 50b). The opening area of ​​the first nick 50a may be larger or smaller than the opening area of ​​the second nick 50b, as shown in Figure 5.

[0037] Thus, the width, depth, and opening area of ​​the first nick 50a and the second nick 50b may differ from each other. As a result, by providing the main cutting edge 14 with a second nick 50b that has a different shape from the first nick 50a, vibrations of the workpiece 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 100 is improved.

[0038] The width w1 and depth h1 of the first nick 50a, and the width w2 and depth h2 of the second nick 50b are measured from the profile shapes of the first nick 50a and the second nick 50b. The profile shapes of the first nick 50a and the second nick 50b may also be measured using a non-contact three-dimensional measuring machine manufactured by Bruker Alicona. The opening area of ​​the first nick 50a and the opening area of ​​the second nick 50b can be calculated from the profile shapes of the first nick 50a and the second nick 50b as described above.

[0039] In one main rake face 41, the first nick 50a and the second nick 50b may be arranged alternately in the direction in which the main cutting edge 14 extends. That is, the second nick 50b may be positioned between two first nicks 50a. Multiple second nicks 50b (for example, two) may be provided between two first nicks 50a.

[0040] In a single main rake face 41, the first nick 50a and the second nick 50b do not have to be arranged at equal intervals. Specifically, as shown in Figure 5, the length of the main cutting edge 14 connecting the pair of first nicks 50a is defined as the first distance L1. The length of the main cutting edge 14 connecting the first nick 50a and the second nick 50b adjacent to the first nick 50a is defined as the second distance L2. The third distance L3 is defined as the second distance L2 plus half the width w2 of the second nick 50b. The third distance L3 may be 0.45 times or more and less than 0.5 times the first distance L1, or greater than 0.5 times and less than or equal to 0.55 times. In this way, in the direction in which the main cutting edge 14 extends, the second nick 50b does not have to be positioned in the middle of the pair of first nicks 50a. This suppresses chatter that occurs during cutting.

[0041] The number of main grooves 40 may be between 4 and 16. In the cutting tool 100 according to this embodiment 1, the number of main cutting edges 14 is 12. That is, the number of main grooves 40 is 12.

[0042] The number of nicks 50 contained in each of the main cutting edges 14 may be less than the number of main cutting edges 14 formed on the cutting tool 100. From a different perspective, the number of main grooves 40 may be greater than the number of nicks grooves 17. In this way, the multiple nicks 50 are arranged so as not to overlap with each other in the rotational direction of the cutting tool 100, thereby suppressing the occurrence of areas in the workpiece that are not cut.

[0043] The cutting tool 100 may be coated with diamond. This prevents the reduction in strength and tool life of the cutting tool 100 caused by the formation of nick portions 5 on the shaft portion 1.

[0044] Figure 6 is a partially enlarged cross-sectional view showing the first relief angle α1. Figure 7 is a partially enlarged cross-sectional view showing the second relief angle α2. Figures 6 and 7 are partially enlarged cross-sectional views of region VI in Figure 4.

[0045] As shown in Figure 4, the line passing through the central axis A and the main cutting edge 14 is defined as the perpendicular line VL. The line passing through the main cutting edge 14 and perpendicular to the perpendicular line VL is defined as the reference line HL. The reference line HL is the tangent to the outermost surface 16 at the main cutting edge 14 (the first point p1 shown in Figures 6 and 7).

[0046] The relief angle is the narrowest angle among the angles formed between the reference line HL and the tangent to the relief surface 10. As shown in Figure 6, the relief angle at the ridge line (main cutting edge 14) between the relief surface 10 and the main rake face 41 of the first main groove 40a is defined as the first relief angle α1. The tangent to the relief surface 10 at the main cutting edge 14 (the first point p1 shown in Figure 6) is defined as the first tangent TL1. The first relief angle α1 is the narrowest angle among the angles formed between the reference line HL and the first tangent TL1.

[0047] As shown in Figure 7, the relief angle at the ridge between the relief surface 10 and the main face 42 of the second main groove 40b is defined as the second relief angle α2. The tangent line of the relief surface 10 at the ridge between the relief surface 10 and the main face 42 of the second main groove 40b (the second point p2 shown in Figure 7) is defined as the second tangent line TL2. The second relief angle α2 is the narrowest angle among the angles made between the reference line HL and the second tangent line TL2.

[0048] Here, a feature of the cutting tool 100 according to this embodiment 1 is that the second relief angle α2 is larger than the first relief angle α1, as shown in Figures 6 and 7. The main cutting edge 14 may be formed such that the second relief angle α2 is larger than the first relief angle α1 in the entire area of ​​the cutting portion 2.

[0049] This increases the length of the secondary cutting edge 15. As a result, the area (secondary cutting edge 15) that holds down the workpiece during cutting increases, thus suppressing vibrations of the workpiece that occur during cutting. Consequently, the finish quality of the machined surface of the workpiece cut by the cutting tool 100 is improved.

[0050] Furthermore, by gradually increasing the relief angle, the increase in cutting resistance is suppressed, while the vibration of the cutting tool 100 generated during cutting is suppressed by the process damping effect. As a result, chipping of the cutting tool 100 is suppressed.

[0051] The relief surface 10 is formed such that the first relief angle α1 is minimized and the second relief angle α2 is maximized at the relief angle of the relief surface 10. In other words, the relief surface 10 is formed such that the relief angle does not decrease but increases monotonically from the first point p1 (main cutting edge 14) to the second point p2 (ridge line between the relief surface 10 and the main face 42 of the second main groove 40b).

[0052] The relief surface 10 may be formed, for example, by a curved surface, such that the first relief angle α1 is minimized and the second relief angle α2 is maximized. The relief surface 10 may be formed by, for example, a single curved surface, and the curvature at the second point p2 on the relief surface 10 may be the same as the curvature at the first point p1.

[0053] The relief surface 10 may be formed by two planes such that the first relief angle α1 is minimized and the second relief angle α2 is maximized. Specifically, the relief surface 10 may include a first region and a second region. The first region includes a first point p1 (main cutting edge 14). The second region includes a second point p2 (edge ​​between the relief surface 10 and the main face 42 of the second main groove 40b). The first and second regions are formed by planes. The second region may be inclined with respect to the first region. In this way, the relief surface 10 is formed such that the first relief angle α1 is minimized and the second relief angle α2 is maximized at the relief angle of the relief surface 10.

[0054] The second point p2 (the ridge line between the relief surface 10 and the main facing surface 42 of the second main groove 40b) may be located on the outermost surface 16. From a different perspective, the radial distance r from the central axis A to the second point p2 may be the same as the radial distance r from the central axis A to the first point p1 (main cutting edge 14). In other words, the distance from the central axis A to the second point p2 may be half the cutting diameter.

[0055] The second point p2 (the ridge line between the relief surface 10 and the main facing surface 42 of the second main groove 40b) may be located between the outermost surface 16 and the central axis A in the radial direction r. In other words, the distance from the central axis A to the second point p2 may be smaller than the distance from the central axis A to the first point p1 (main cutting edge 14).

[0056] The first relief angle α1 is, for example, greater than 0° and less than or equal to 6°. On the other hand, the second relief angle α2 is, for example, greater than 6° and less than or equal to 12°. In particular, the second relief angle α2 may be between 1.5 and 2 times the first relief angle α1.

[0057] The rake angle is defined as the narrowest angle between the tangent line of the main rake face 41 at the edge (main cutting edge 14) between the flank face 10 and the main rake face 41, and the perpendicular line VL. The rake angle may be 10° or more. In this way, even when the flank angle is small (for example, the flank angle is 10° or less), the workpiece, which is formed of fibers, can be cut well.

[0058] <Effects and Effects> The cutting tool 100 according to this disclosure comprises a shaft portion 1. The shaft portion 1 has a flank surface 10. A main groove portion 4 and a nick portion 5 are formed on the shaft portion 1. The main groove portion 4 includes a first main groove 40a and a second main groove 40b. Each of the first main groove 40a and the second main groove 40b includes a main rake face 41 and a main face 42. The main face 42 faces the main rake face 41. Each of the main rake face 41 of the first main groove 40a and the main face 42 of the second main groove 40b is connected to the flank surface 10. The nick portion 5 includes a secondary rake face 51. The ridge line between the flank surface 10 and the main rake face 41 constitutes a main cutting edge 14 having a main helix angle θ1. The ridge line between the flank surface 10 and the secondary rake face 51 constitutes a secondary cutting edge 15. The secondary cutting edge 15 has a reverse helix angle θ2 in the opposite direction to the main helix angle θ1. The first relief angle α1 is the relief angle at the ridge between the relief face 10 and the main rake face 41 of the first main groove 40a. The second relief angle α2 is the relief angle at the ridge between the relief face 10 and the main face 42 of the second main groove 40b. The second relief angle α2 is greater than the first relief angle α1.

[0059] In this way, the length of the secondary cutting edge 15 is increased, and vibrations of the workpiece generated during cutting are suppressed. As a result, the finish quality of the machined surface of the workpiece cut by the cutting tool 100 is improved.

[0060] According to the above cutting tool 100, the first relief angle α1 is greater than 0° and 6° or less. The second relief angle α2 is greater than 6° and 12° or less.

[0061] In this way, the vibration of the cutting tool 100 generated during machining is suppressed by the process damping effect. As a result, chipping of the cutting tool 100 is suppressed.

[0062] According to the cutting tool 100 described above, the second relief angle α2 is between 1.5 and 2 times the first relief angle α1.

[0063] In this way, while suppressing the increase in cutting resistance, the vibration of the cutting tool 100 that occurs during cutting is suppressed by the process damping effect.

[0064] According to the cutting tool 100 described above, the main groove section 4 includes a plurality of main grooves 40. The nick section 5 includes a plurality of nicks 50. The plurality of nicks 50 are arranged to constitute a plurality of nick grooves 17. The number of main grooves 40 is greater than the number of nick grooves 17.

[0065] This method reduces the occurrence of areas in the workpiece that are not cut. According to the above cutting tool 100, the principal helix angle θ1 is between 10° and 25°. The reverse helix angle θ2 is between 30° and 45°.

[0066] This method suppresses vibrations of the workpiece that occur during the cutting process. To verify the effectiveness of the cutting tool 100 according to this embodiment 1 as described above, the following tests were conducted.

[0067] (Target of the test) In this test, the finish of the machined surface of a workpiece and the tool life of the cutting tool 100 were evaluated when the workpiece was machined using the cutting tool 100. The test subjects were the cutting tools 100 from Sample 1 to Sample 9. Sample 1 is a comparative example, and the first relief angle α1 and the second relief angle α2 are the same. The cutting tools 100 from Sample 2 to Sample 9 are examples, and the second relief angle α2 is larger than the first relief angle α1.

[0068] Table 1 shows the specifications of the cutting tool 100 for Samples 1 through 9. In Table 1, the first relief angle α1, the second relief angle α2, the principal helix angle θ1, and the reverse helix angle θ2 are shown from left to right. Note that the cutting tool 100 for Samples 1 through 8 is coated with diamond. The cutting tool 100 for Sample 9 is not coated with diamond. The cutting diameter for the cutting tool 100 for Samples 1 through 9 is 10 mm.

[0069] [Table 1]

[0070] As shown in Table 1, in the cutting tool 100 for Sample 1, the first relief angle α1 and the second relief angle α2 are the same, both being 10°. In other words, the relief surface 10 in the cutting tool 100 for Sample 1 is a so-called linear relief, formed by a flat surface. On the other hand, in the cutting tools 100 for Samples 2 to 9, the second relief angle α2 is larger than the first relief angle α1. The relief surface 10 in the cutting tools 100 for Samples 2 to 9 is a so-called circular relief, formed by a curved surface.

[0071] (Cutting conditions) The workpiece to be machined is CFRP (Carbon Fiber Reinforced Plastics). The thickness of the CFRP is 2 mm. The cutting conditions were a cutting tool 100 with a rotational speed of 8000 rpm and a machining speed of 1000 mm / min.

[0072] (Test results)

[0073] [Table 2]

[0074] The test results are shown in Table 2. In Table 2, the finish of the machined surface of the workpiece and the tool life of the cutting tool 100 are shown from left to right. In the finish of the machined surface and the tool life of the cutting tool 100 shown in Table 2, A, B, and C indicate the evaluation results for each item. B indicates that it is better than C. A indicates that it is better than B. In other words, A indicates that it is the best evaluation result among A, B, and C.

[0075] As can be seen from Table 2, the surface finish of the cutting tool 100 according to Samples 2 to 9, which are examples, is better than that of the cutting tool 100 according to Sample 1, which is a comparative example. This indicates that the surface finish is improved when the second relief angle α2 is larger than the first relief angle α1.

[0076] In the cutting tools 100 for Samples 2, 3, 6, and 9, the first relief angle α1 was greater than 0° and 6° or less, the second relief angle α2 was greater than 6° and 12° or less, the principal helix angle θ1 was between 10° and 25°, and the reverse helix angle θ2 was between 30° and 45°. Therefore, as shown in Table 2, the surface finish of the machined areas and the tool life of each of the cutting tools 100 for Samples 2, 3, 6, and 9 were all rated A.

[0077] On the other hand, in the cutting tool 100 for sample 4, the first relief angle α1 was 9°, which is greater than 6°. In the cutting tool 100 for sample 5, the second relief angle α2 was 4°, which is 6° or less. In the cutting tool 100 for sample 7, the principal helix angle θ1 was 40°, which is greater than 25°. In the cutting tool 100 for sample 8, the reverse helix angle θ2 was 20°, which is less than 30°. Therefore, from Table 2, the surface finish of the machined areas and the tool life of the cutting tools 100 for each of the cutting tools 100 for samples 4, 5, 7, and 8 were all rated B.

[0078] As can be seen from Table 2, the tool life of the cutting tool 100 for Sample 2, Sample 3, and Sample 6 is improved compared to the tool life of the cutting tool 100 for Sample 4, Sample 5, and Samples 7 through 9.

[0079] The cutting tool 100 for Sample 2 is coated with diamond. Therefore, as shown in Table 2, the tool life of the cutting tool 100 for Sample 2 was A. On the other hand, the cutting tool 100 for Sample 9 is not coated with diamond. Therefore, as shown in Table 2, the tool life of the cutting tool 100 for Sample 9 was B. From this, it can be seen that the tool life of the cutting tool 100 is improved by the diamond coating.

[0080] It should be understood that at least one configuration or feature described in each embodiment and example can be combined with other embodiments and examples, or modified in various ways. The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The basic scope of this disclosure is indicated by the claims rather than the embodiments described above, and all modifications within the meaning and scope of the claims are intended to be included. [Explanation of symbols]

[0081] 1 Shank section, 2 Cutting section, 3 Shank section, 4 Main groove section, 5 Nick section, 10 Relief face, 11 Tip section, 12 Rear end section, 14 Main cutting edge, 15 Secondary cutting edge, 16 Outermost surface, 17 Nick groove, 40 Main groove, 40a First main groove, 40b Second main groove, 41 Main rake face, 42 Main opposite face, 50 Nick, 50a First nickname, 50b Second nickname, 51 Secondary rake face, 52 Secondary opposite face, 100 Cutting tool, A Center axis, HL Reference line, L1 First distance, L2 Second distance, L3 Third distance, p1 First point, p2 Second point, r Radial direction, TL1 First tangent, TL2 Second tangent, VL Perpendicular line, w1 Width, w2 Width, z Axis direction, α1 First relief angle, α2 Second relief angle, θ1 Principal angle of twist, θ2 reverse angle of twist.

Claims

1. It has a shaft portion with a relief surface, The shaft portion has a main groove and a nick portion formed therein. The main groove section includes a first main groove and a second main groove. Each of the first main groove and the second main groove includes a main rake face and a main face facing the main rake face, The main rake face of the first main groove and the main facing face of the second main groove are connected to the relief face, The aforementioned nick portion includes a secondary rake face, The ridge line between the relief face and the main rake face constitutes a main cutting edge having a main helix angle. The ridge line between the relief face and the secondary rake face constitutes a secondary cutting edge having a reverse helix angle in the opposite direction to the primary helix angle. The relief angle at the ridge between the relief surface and the main rake face of the first main groove is defined as the first relief angle. The relief angle at the ridge between the relief surface and the main face of the second main groove is defined as the second relief angle. The second relief angle is larger than the first relief angle. The first relief angle is greater than 0° and less than or equal to 6°. The cutting tool has a second relief angle greater than 6° and less than or equal to 12°.

2. The cutting tool according to claim 1, wherein the second relief angle is 1.5 times or more and 2 times or less the first relief angle.

3. The main groove section includes a plurality of main grooves, The aforementioned nick section includes multiple nicks, The aforementioned multiple nicks are arranged to form multiple nick grooves, The cutting tool according to claim 1, wherein the number of main grooves is greater than the number of nick grooves.

4. The aforementioned principal twist angle is 10° or more and 25° or less. The cutting tool according to any one of claims 1 to 3, wherein the reverse helix angle is 30° or more and 45° or less.

5. The first relief angle is 10° or less, The cutting tool according to any one of claims 1 to 3, wherein the rake angle at the ridge between the relief face and the main rake face is 10° or more.

6. The nick portion includes a first nick and a second nick having a different shape from the first nick, In the direction in which the main cutting edge extends, the first and second nicks are arranged alternately. The length of the main cutting edge connecting the pair of first nicks is defined as the first distance. The length of the main cutting edge connecting the first nick and the second nick adjacent to the first nick is defined as the second distance. If the third distance is obtained by adding half the width of the second nick to the second distance, The cutting tool according to any one of claims 1 to 3, wherein the third distance is 0.45 times or more but less than 0.5 times or more than 0.5 times or less than or equal to 0.55 times the first distance.

Images