End mill

Abstract

The three peripheral cutting edges are provided with three kinds of cutting edges, i.e., a bending edge (BS), a left-hand edge (BL), and a right-hand edge (BR), and adjacent peripheral cutting edges are formed by different kinds of cutting edges. Therefore, the intervals of the adjacent peripheral cutting edges are unequal and continuously change in the axial direction, and the directions of the cutting forces are also different. Thus, resonance can be suppressed, and an anti-vibration effect can be appropriately obtained. In addition, by providing the bending edge (BS), compared with the case where only the right-hand edge (BR) and the left-hand edge (BL) are present, the generation of burrs and the like can be further appropriately suppressed, and since the cutting force acts in the direction of the inside of the bending shape, the vibration in the plate thickness direction of the workpiece can be suppressed. In addition, the bending edge (BS) forms a smooth bending shape, and thus, compared with a herringbone shape, the retention of chips can be suppressed, the restrictions on the machining conditions can be relaxed, and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to a end mill, and particularly to a new end mill effective for vibration prevention performance and suppression of burr and delamination. BACKGROUND

[0002] Carbon fiber reinforced materials such as CFRP (Carbon Fiber Reinforced Plastic) and CFRTP (Carbon Fiber Reinforced Thermoplastic) have a problem that burr and delamination (hereinafter, referred to as burr and the like.) are easily generated. In this regard, a so-called herringbone end mill in which two kinds of peripheral cutting edges having opposite twist directions are adjacently provided in a tool axis direction (refer to Patent Literature 1) has been proposed. According to the herringbone end mill, it is possible to make the peripheral cutting edges enter both upper and lower surfaces of a workpiece (a material to be cut) at an acute angle, and to suppress generation of burr and the like. In addition, an end mill in which right-handed right-handed edges and left-handed left-handed edges are alternately arranged in a circumferential direction as peripheral cutting edges (refer to Patent Literature 2) has also been proposed.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT LITERATURE

[0005] Patent Literature 1: Japanese Patent Application Publication No. 2013-22657

[0006] Patent Literature 2: WO 2009 / 122937 SUMMARY

[0007] PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] However, in the case of the end mill of Patent Literature 1, the shape of the overlapping portion of the two kinds of peripheral cutting edges having opposite twist directions is complicated, and chips are easily retained, so that the machining conditions can be limited. In Patent Literature 2 in which the right-handed edges and the left-handed edges are alternately arranged in the circumferential direction, there are portions in each spiral edge in which the peripheral cutting edge enters the surface of the workpiece at an obtuse angle, so that there are problems that the suppression effect of burr and the like is not sufficiently obtained, and that chatter is easily generated because the right-handed edges and the left-handed edges act forces in opposite directions in the thickness direction of the workpiece.

[0009] The present application has been achieved in light of the above circumstances, and aims to provide a new end mill effective for vibration prevention performance and suppression of burr and the like.

[0010] MEANS FOR SOLVING THE PROBLEMS

[0011] To achieve the object, the first invention is a ball end mill having a plurality of peripheral cutting edges, characterized in that (a) as the peripheral cutting edges, there are provided a right-hand cutting edge of right-hand twist, a left-hand cutting edge of left-hand twist, and a curved cutting edge of which the twist direction is reversed at the middle, and which forms a curved shape curved in a circular arc or bow shape in an unfolded view unfolded around an axis center, and which is provided with a cutting edge on a concave side of the curved shape, (b) adjacent peripheral cutting edges are composed of different kinds of cutting edges.

[0012] The second invention is the ball end mill of the first invention, characterized in that (a) the helix angle of the right-hand cutting edge is in a range of 1° to 15°, (b) the helix angle of the left-hand cutting edge is in a range of 1° to 15°. Further, the helix angle is positive, regardless of right-hand or left-hand, indicating the magnitude of the inclination angle of the cutting edge with respect to the direction parallel to the tool axis center.

[0013] The third invention is the ball end mill of the first invention or the second invention, characterized in that the plurality of peripheral cutting edges are composed of any one of a normal cutting edge, a nick cutting edge, and a roughing cutting edge. Further, the normal cutting edge is a smooth and ordinary cutting edge of constant outer diameter size without a nick (slot) or a roughing portion (waveform).

[0014] The fourth invention is the ball end mill of any one of the first invention to the third invention, characterized in that an equally divided position at which the peripheral cutting edge is equally divided in the circumferential direction exists in a range from a position at which the peripheral cutting edge is further distanced from the base edge side end portion of the cutting edge to a position at which the peripheral cutting edge is further distanced from the shank portion side end portion of the cutting edge by 1 / 4 of the cutting edge length in the tool axis direction, assuming that the peripheral cutting edge is elongated in the tool axis direction with a certain helix angle and a certain curvature.

[0015] The fifth invention is the ball end mill of any one of the first invention to the fourth invention, characterized in that the angle difference between the helix angle of the right-hand cutting edge and the helix angle of the left-hand cutting edge is within ±5°.

[0016] The sixth invention is the ball end mill of any one of the first invention to the fifth invention, characterized in that at least one of a plurality of base edges provided continuously with the peripheral cutting edges at the tool tip end has a center edge reaching the vicinity of the tool axis center.

[0017] The seventh invention is the ball end mill of any one of the first invention to the sixth invention, characterized in that the number of the peripheral cutting edges is three or more and six or less.

[0018] The eighth invention is the ball end mill of any one of the first invention to the seventh invention, characterized in that the surface of the edge portion in which the peripheral cutting edges are provided is coated with a diamond coating film.

[0019] The ninth invention is the end mill according to any one of the first to eighth inventions, characterized in that the end mill is composed of superhard alloy.

[0020] Effects of the invention

[0021] In such an end mill, as the peripheral cutting edges, three kinds of cutting edges, right-hand edges, left-hand edges, and curved edges are provided, and adjacent peripheral cutting edges are composed of different kinds of cutting edges, so that the intervals of the adjacent peripheral cutting edges are unequal intervals and continuously change in the axial direction, and the directions of the cutting forces are also different, so that resonance can be suppressed and the antivibration effect can be appropriately obtained. In addition, by providing the curved edges, compared with the case where only right-hand edges and left-hand edges are present, the generation of burrs and the like can be further appropriately suppressed, and since the cutting forces act in the direction of the inside of the curved shape, the chattering in the direction of the thickness of the workpiece can be suppressed. In addition, the curved edges form a smooth curved shape, so that compared with a chevron shape, the retention of chips can be suppressed, the restriction of the machining conditions can be relaxed, and the like.

[0022] In the second invention, the helix angle of the right-hand edges is in the range of 1° to 15°, and the helix angle of the left-hand edges is in the range of 1° to 15°, so that the antivibration effect, the suppression effect of burrs and the like, and the suppression effect of chattering can be appropriately obtained. That is, if the helix angle becomes large, burrs and the like are easily generated and chattering becomes large, so that it is difficult to appropriately suppress regardless of the presence or absence of the circular-arc edges.

[0023] In the third invention, in the case where the plurality of peripheral cutting edges are composed of any one of the ordinary edges, the notched edges, and the roughing edges, an end mill of a prescribed cutting edge shape can be adopted according to the use for finishing, semi-finishing, roughing, and the like, or the material of the workpiece, and the like.

[0024] In the fourth invention, the equisection position at which the peripheral cutting edges are equisectioned in the circumferential direction is present in the range from the position at which the blade length is separated by 1 / 4 from the end portion on the bottom edge side of the peripheral cutting edge toward the end portion on the front end side in the tool shaft direction to the position at which the blade length is separated by 1 / 4 from the end portion on the shank portion side of the peripheral cutting edge toward the shank portion side, and in this case, compared with the case where the range is outside, an excellent machined surface roughness can be obtained.

[0025] In the fifth invention, in the case where the angle difference between the helix angle of the right-hand edges and the helix angle of the left-hand edges is within ±5°, compared with the case where the angle difference exceeds ±5°, the width of the relief surface wear is small, and the tool life can be ensured while the antivibration effect due to the unequal sectioning and the suppression effect of burrs and the like due to the curved edges are obtained.

[0026] In the sixth invention, in the case where at least one of the plurality of bottom edges provided continuously with the peripheral cutting edge at the front end of the tool has a center edge reaching the vicinity of the tool axis, plunge milling can be performed, and the versatility of the tool is improved.

[0027] In the seventh invention, the number of edges of the peripheral cutting edge is three or more and six or less, and therefore, the present invention is preferably applied in which right-hand edges, left-hand edges, and curved edges are provided as the peripheral cutting edge.

[0028] In the eighth invention, the surface of the edge portion in which the peripheral cutting edge is provided is coated with a diamond coating film, and therefore, excellent cutting durability can be obtained.

[0029] In the ninth invention, the end mill is composed of superhard alloy, and therefore, excellent cutting durability can be obtained. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 is a perspective view showing an end mill as an embodiment of the present invention.

[0031] Figure 2 is a view showing the shape of three peripheral cutting edges provided in the end mill of Figure 1

[0032] Figure 3 is a view showing the curved shape of the curved edge of Figure 2

[0033] Figure 4 is a photograph showing various modes of the curved shape of the curved edge.

[0034] Figure 5 is a view showing other modes of the curved edge including the circular arc edge of Figure 3

[0035] Figure 6 is a view showing a combination of the circular arc edge, the right-hand edge, and the left-hand edge of the three-edge end mill.

[0036] Figure 7 is a view showing a combination of the circular arc edge, the right-hand edge, and the left-hand edge of the four-edge end mill.

[0037] Figure 8 is a view showing a combination of the circular arc edge, the right-hand edge, and the left-hand edge of the five-edge end mill.

[0038] Figure 9 is a view showing a combination of the circular arc edge, the right-hand edge, and the left-hand edge of the six-edge end mill.

[0039] Figure 10 ​​​This diagram illustrates a comparison between the case where the outer peripheral cutting edge of an end mill is composed of a notched edge or a roughing edge and a conventional edge.

[0040] Figure 11 This diagram illustrates the circumferential configuration of the three cutting edges of a 3-flute end mill: the circular arc cutting edge, the right-hand cutting edge, and the left-hand cutting edge.

[0041] Figure 12 This diagram illustrates the presence or absence of the center cutting edge at the bottom cutting edge of a 3-flute end mill.

[0042] Figure 13 This invention is described by comparing the product of this invention with a conventional product that does not have a bending edge. Figure 1 A diagram showing the direction and magnitude of the cutting forces generated by the three outer cutting edges of an end mill and their entry into the workpiece.

[0043] Figure 14 This is a diagram illustrating the positional offset of a conventional herringbone product relative to the material being cut.

[0044] Figure 15 This diagram illustrates the peripheral cutting edges of the five test specimens No.1 to No.5 used in the cutting test.

[0045] Figure 16 It is a diagram illustrating the resultant force of the resistance values ​​measured in the cutting test.

[0046] Figure 17 It is a diagram illustrating the positional relationship between the material being cut and the tool in a cutting experiment.

[0047] Figure 18 It is a graph illustrating the amplitude of the resultant force of the resistance values ​​measured in the cutting test.

[0048] Figure 19 This is a diagram illustrating the machining conditions for the cutting test.

[0049] Figure 20 This means that in Figure 19 The graph shows the amplitude and ratio of the resultant force of the resistance value measured under the machining conditions.

[0050] Figure 21 It is represented by a comparison of charts. Figure 20 The graph of the amplitude.

[0051] Figure 22 This is a diagram illustrating three test specimens No.1 to No.3 with different shapes of the outer peripheral cutting edge.

[0052] Figure 23 This is an instruction on how to use. Figure 22 The diagram shows the machining conditions for the cutting tests conducted on test specimens No.1 to No.3.

[0053] Figure 24 This is an explanation Figure 22 The graph shows the test results related to the cutting edge shape and burr generation of test samples No.1 to No.3.

[0054] Figure 25 This is a diagram illustrating the different helix angles α and β of right-handed and left-handed blades in six test specimens No.1 to No.6.

[0055] Figure 26 This is an instruction on how to use. Figure 25 The diagram shows the machining conditions for the cutting tests conducted on test specimens No.1 to No.6.

[0056] Figure 27 This means that in Figure 26 The figure shows the experimental results obtained by changing the cutting speed while performing cutting experiments under certain processing conditions.

[0057] Figure 28 This is an example in Figure 26 The image shows photographs of the chips produced when test specimens No1 and No2 were machined at a cutting speed of 400 m / min during the cutting test.

[0058] Figure 29 This is a diagram illustrating the three test samples No.1 to No.3.

[0059] Figure 30 This is an instruction on how to use. Figure 29 The diagram shows the machining conditions for the cutting tests conducted on test specimens No.1 to No.3.

[0060] Figure 31 This means that in Figure 30 The graph shows the test results obtained from cutting tests under certain processing conditions. It is a graph that compares the vibration waveform of the resultant force of the resistance value, the maximum value and amplitude of the resultant force, its ratio, and photographs of burrs.

[0061] Figure 32 The diagram illustrates five test specimens No.1 to No.5 with different equidistant division positions of the outer peripheral cutting edge.

[0062] Figure 33 This is a detailed explanation. Figure 32 A diagram with equally divided positions.

[0063] Figure 34 This is an instruction on how to use. Figure 32 The diagram shows the machining conditions for the cutting tests conducted on test specimens No.1 to No.3.

[0064] Figure 35 This is an explanation Figure 34The graph of the test results is a graph showing the measurement results of the surface roughness of the machined surface.

[0065] Figure 36 It is represented by a comparison of charts. Figure 35 A diagram showing the surface roughness of the machined surface.

[0066] Figure 37 This is a diagram illustrating the difference in helix angle δ between the right-handed and left-handed blades for four test specimens No.1 to No.4.

[0067] Figure 38 This is a detailed explanation. Figure 37 The diagram shows the cutting edge shapes of the four test samples No.1 to No.4.

[0068] Figure 39 This is an instruction on how to use. Figure 37 The diagram shows the machining conditions for the cutting tests conducted on test specimens No.1 to No.4.

[0069] Figure 40 This means that in Figure 39 The graph shows the test results obtained from cutting experiments under certain processing conditions. It is a graph that uses chart comparison to represent the wear width of the flank face. Detailed Implementation

[0070] The end mill of the present invention can be either a clockwise rotating end mill driven for cutting when viewed from the shank side, or a counterclockwise rotating end mill driven for cutting. When driven for cutting in a clockwise rotating manner when viewed from the shank side, the curved cutting edge is configured to form a curved shape that varies with the shank side being left-handed and the bottom cutting edge side being right-handed. When driven for cutting in a counterclockwise rotating manner when viewed from the shank side, the curved cutting edge is configured to form a curved shape that varies with the shank side being right-handed and the bottom cutting edge side being left-handed. The number of cutting edges is widely used for end mills from 3 to 6, but it can also be applied to end mills with 7 or more cutting edges.

[0071] The helix angle of the right-hand blade and the left-hand blade is preferably in the range of 1° to 15°, but can also be set to a helix angle of less than 1° or a helix angle of more than 15°. The equal division positions of the plurality of peripheral cutting edges, which are divided equally in the circumferential direction, are preferably in the range where, assuming that the peripheral cutting edges are each extended in the tool axis direction with a certain helix angle and a certain curvature, the range between the position where the distance from the bottom edge side end portion of the peripheral cutting edge to the front end side in the tool axis direction is 1 / 4 of the edge length and the position where the distance from the shank side end portion of the peripheral cutting edge to the shank side is 1 / 4 of the edge length, but as a more preferable range, the range where the distance from the bottom edge side end portion to the shank side is 1 / 4 to 3 / 4 of the edge length. The equal division positions can also be located at a position where the distance from the bottom edge side end portion to the front end side is more than 1 / 4 of the edge length or a position where the distance from the shank side end portion to the shank side is more than 1 / 4 of the edge length, and the plurality of peripheral cutting edges can also be arranged in a manner that is not equally divided. The angle difference between the helix angle of the right-hand blade and the helix angle of the left-hand blade is preferably within ±5°, but can also be set to an angle difference of more than ±5°. It is preferable that at least one of the plurality of bottom edges have a center edge, but all of the bottom edges can also not have a center edge.

[0072] The curved edge, which forms a curved shape in an expanded view expanded around the axis center, is, for example, a circular arc composed of a portion of a true circle, but can also be a circular arc composed of a portion of an ellipse, can be a shape in which a plurality of circular arcs having different curvatures are smoothly connected, can be a shape in which a straight portion is provided midway through the circular arc, or the like, and can be set in various ways. That is, between the shank side end portion and the bottom edge side end portion, the twist direction is changed from right-hand to left-hand or from left-hand to right-hand, and the twist direction is changed irreversibly and smoothly from one of the left and right directions to the other direction. Such a curved edge can be formed by grinding processing using a grinder, for example, using a 5-axis or the like compound grinding machine.

[0073] The most concave point P1 of the curved shape of the curved edge in the expanded view is preferably in the range where the distance from the bottom edge side end portion P2 in the tool axis direction is 5% to 95% of the edge length, but as long as the twist directions of the cutting edges of at least the two end portions are opposite, P1 can also be located at a position of less than 5% or more than 95%. When the bottom edge side end portion in the tool axis direction is set as P2 and the shank side end portion in the tool axis direction is set as P3, the width dimension a of the circumferential direction between P1 and P2 and the width dimension b of the circumferential direction between P1 and P3 are each preferably in the range of 0.0002 or more and 0.1300 or less of the edge length, but can also be a width dimension of less than 0.0002 or more than 0.1300 of the edge length. The curvature near the bottom edge side end portion P2 and the shank side end portion P3 of the curved edge is also related to the above width dimensions a and b, and the greater the width dimensions a and b, the greater the curvature in general. As the width dimensions a and b, for example, it is appropriate to be in the range of about 0.08 mm to 1.19 mm.

[0074] The notch blade or roughing blade can be provided with the concave-convex blade of the notch (groove) and roughing (wavy shape) over the entire region of the blade length, but can also be provided only in a portion of the blade length, such as 5% to 65% of the blade length in a range of 70% of the blade length from the handle portion side end toward the bottom blade side in the tool axis direction, 5% to 65% of the blade length in a range of 70% of the blade length from the bottom blade side end toward the handle portion side in the tool axis direction, or 5% to 65% of the blade length in a range of 35% of the blade length from the center of the blade length in the tool axis direction to both directions of the tool axis direction. In addition, the concave-convex blade can also be provided in a range less than 5% of the blade length or a range more than 65% of the blade length.

[0075] The end mill of the present application is preferably used, for example, for trimming (peripheral cutting) of FRP (fiber reinforced plastic) such as CFRP (carbon fiber reinforced plastic) and CFRTP (carbon fiber reinforced thermoplastic plastic), but can also be used for cutting of other machined materials such as steel materials. As the material of the end mill, super hard alloy or high hardness sintered body is preferably used, but other hard tool materials such as high speed tool steel can also be used, and a hard coating film can be applied as needed to improve cutting durability. As the hard coating film, diamond coating film is appropriate, and other hard coating films such as intermetallic compounds can also be used.

[0076] Example

[0077] Hereinafter, an example of the present application will be described in detail with reference to the drawings. In addition, in the following example, the drawings are appropriately simplified or modified for explanation, and the size ratio and shape of each part are not necessarily accurately drawn.

[0078] Figure 1 is a perspective view showing an end mill 10 as an example of the present application. The end mill 10 has a shank portion 12 and a blade portion 14 concentrically, and three peripheral cutting edges 20a, 20b, 20c (hereinafter, simply referred to as peripheral cutting edges 20 without particular distinction) are formed by providing three grooves in the blade portion 14. A bottom blade 22a, 22b, 22c (hereinafter, simply referred to as bottom blade 22 without particular distinction) is continuously provided at the tip of each of the three peripheral cutting edges 20a, 20b, 20c. The end mill 10 is driven to perform cutting by rotating in the clockwise direction when viewed from the shank portion 12 side. The end mill 10 is composed of super hard alloy, and a diamond coating film 24 is applied as a hard coating film on the surface of the blade portion 14. The diamond coating film 24 is single crystal diamond or polycrystal diamond. Figure 1 The diagonal portion of shows the diamond coating film 24.

[0079] The three peripheral cutting edges 20 are formed by Figure 2The three types of cutting edges BS, BL, and BR shown are used, and adjacent peripheral cutting edges 20 are defined as different types of cutting edges BS, BL, and BR. In the case of a three-flute end mill 10, the three peripheral cutting edges 20 are composed of the three types of cutting edges BS, BL, and BR. Cutting edge BS is a curved cutting edge whose torsional direction reverses left and right midway, and forms a curved shape in an arc or bow shape in the unfolded diagram around the axis, with the cutting edge provided on the concave side of the curved shape. Figure 1 In the end mill 10, the outer peripheral cutting edge 20a corresponds to the curved cutting edge BS. The cutting edge BL is a left-handed cutting edge that twists counterclockwise at a helix angle β, preferably within the range of 1° to 15°. Figure 1 In the end mill 10, the outer peripheral cutting edge 20b corresponds to a left-handed cutting edge BL. BR is a right-handed cutting edge that twists clockwise at a helix angle α, preferably within the range of 1° to 15°. Figure 1 In the end mill 10, the outer peripheral cutting edge 20c corresponds to the right-hand cutting edge BR. Furthermore, the angle difference δ (=α-β) between the helix angle α of the right-hand cutting edge BR and the helix angle β of the left-hand cutting edge BL is preferably within ±5°.

[0080] The aforementioned curved blade BS, for example, Figure 3 It is constructed as shown in the circular arc blades A to C. Figure 3 All are unfolded diagrams about the axis of the end mill 10. The circular arc cutting edges A to C are circular arc cutting edges whose curved shape is an arc formed by a part of a perfect circle in the unfolded diagram. Moreover, when the most concave point (concave point), that is, the point on the last side in the circumferential cutting rotation direction, is set as P1, the bottom cutting edge end in the tool axis direction is set as P2, and the shank end in the tool axis direction is set as P3, the circumferential width dimension (bottom cutting edge width dimension) a between the concave point P1 and the bottom cutting edge end P2 and the circumferential width dimension (shank end width dimension) b between the concave point P1 and the shank end P3 are preferably in the range of cutting length L × 0.0002 or more and cutting length L × 0.1300 or less, as shown in formulas (1) and (2). As for the specific dimensions of the width dimensions a and b, they are set to be in the range of about 0.08 mm to 1.19 mm. Furthermore, the tool axis dimension Lp1 from the bottom edge end P2 to the concave point P1 is preferably within the range of 5% to 95% of the blade length L, as shown in formula (3). In this embodiment, the bottom edge end P2 is set to right-hand rotation, and the shank end P3 is set to left-hand rotation. The curved blades A to C are all curved in the unfolded diagram as arcs, therefore, the tool axis position of the center point of the arc is consistent with the concave point P1. In addition, the curved blade A is a = b, the curved blade B is a > b, and the curved blade C is a < b.

[0081] L×0.0002≤a≤L×0.1300 ··· (1)

[0082] L x 0.0002 < b < L x 0.1300 (2)

[0083] L x 0.05 < Lpl < L x 0.95 (3)

[0084] Figure 4 is a photograph of the cutting edge shape in the case where the proportion of the dimension Lpl is 0%, 5%, 50%, 95%, 100%, and the left side is the front end side, i.e., the bottom edge 22 side. Also, in the case where the dimension Lpl is 0%, the end portion P2 on the bottom edge side becomes a straight edge parallel to the axis, and thus the effect of suppressing burrs and the like cannot be properly obtained on the bottom edge 22 side. Also, in the case where the dimension Lpl is 100%, the end portion P3 on the shank side becomes a straight edge parallel to the axis, and thus the effect of suppressing burrs and the like cannot be properly obtained on the shank 12 side. Figure 4 The white arrows of indicate the directions of the cutting forces at each portion of the cutting edge.

[0085] Figure 5 is a diagram illustrating other examples of the curved edge BS of Figure 2 The curved edges A to C are the same as the circular arc edges A to C of the above-described Figure 3 Edge D is the same as edge A in that the bottom edge side width dimension a and the shank side width dimension b are equal, but the curvature of the circular arc is small, i.e., the radius of the circular arc is large, and the width dimensions a, b are smaller than those of edge A. Edge E is the same as edge A in that the bottom edge side width dimension a and the shank side width dimension b are equal, but the curvature of the circular arc is large, i.e., the radius of the circular arc is small, and the width dimensions a, b are larger than those of edge A. Edge F is an example in which the curved shape is composed of a plurality of curves, and is a circular arc having the same curvature as edge A in the vicinity of the concave point Pl, but the curvature of the circular arc is large in the vicinity of the end portion P2 on the bottom edge side and the end portion P3 on the shank side, and the bottom edge side width dimension a and the shank side width dimension b are the same as each other and larger than the width dimensions a, b of the above-described edge A. Edge G is an example in which the curved shape is composed of a plurality of curves, and the curvature of the circular arc in the vicinity of the end portion P2 on the bottom edge side is larger than that of edge A, the shank side width dimension b is the same as the width dimension b of the above-described edge A, but the bottom edge side width dimension a is larger than the width dimension a of the above-described edge A. Edge H is the reverse of edge G, and the curvature of the circular arc in the vicinity of the end portion P3 on the shank side is larger than that of edge A, the bottom edge side width dimension a is the same as the width dimension a of the above-described edge A, but the shank side width dimension b is larger than the width dimension b of the above-described edge A.

[0086] The number of edges of the peripheral cutting edge 20 of such an end mill 10 is not limited to three, and as shown in Figures 6-9 application to three or more and six or less is preferable. Figures 6-9 is an example of Figure 2The figure showing the combination of the three kinds of blades BS, BL, and BR, here, "Arc" indicates the curved blade BS, "Left" indicates the left-handed blade BL, and "Right" indicates the right-handed blade BR, and No 1 to No 8 are specific examples. Blades 1 to 6 correspond to the peripheral cutting edges 20, Figure 6 In the case of 3 blades, Figure 7 In the case of 4 blades, Figure 8 In the case of 5 blades, Figure 9 In the case of 6 blades, any of the cases is set so that the adjacent blades 1 to 6 are different kinds of blades BS, BL, or BR, that is, so that "Arc", "Left", and "Right" are discontinuous. The number of blades of the peripheral cutting edges 20 of the end mill 10 can also be 7 or more, and set so that the adjacent peripheral cutting edges 20 are different kinds of blades BS, BL, or BR.

[0087] In addition, as shown in Figure 10 The peripheral cutting edges 20 of the end mill 10 can also be ordinary blades 30a to 30c (hereinafter, simply referred to as ordinary blades 30 without particular distinction.) that have neither a notch nor a roughened portion, but can also be set as notched blades 32a to 32c (hereinafter, simply referred to as notched blades 32 without particular distinction.) or as roughened blades 34a to 34c (hereinafter, simply referred to as roughened blades 34 without particular distinction.). Figure 10 The upper layer of the photograph is an enlarged view of the ordinary blades 30, notched blades 32, and roughened blades 34 viewed from the rake face side, and the lower layer is a photograph of the blade portion 14 viewed from the oblique nose side as Figure 1 The upper layer of the photograph is an enlarged view of the ordinary blades 30, notched blades 32, and roughened blades 34 viewed from the rake face side, and the lower layer is a photograph of the blade portion 14 viewed from the oblique nose side as Figure 10 The end mill 10 is 3 blades, and the ordinary blades 30a to 30c are composed of the three kinds of blades BS, BL, and BR shown in Figure 2 The notched blades 32a to 32c and the roughened blades 34a to 34c are structures in which a notch or a roughened portion is provided on the ordinary blades 30a to 30c, and for example, a notch or a roughened portion can be provided in the entire region of the blade length L, but can also be provided only in a part in the tool shaft direction. The position at which the notch or the roughened portion is provided can be the central portion of the blade length L, or can be the shank portion 12 side or the bottom blade 22 side, and is preferably provided at different positions. For example Figure 10The notched cutting edge 32a and the roughing cutting edge 34a have notches or roughing portions throughout the entire area of ​​the cutting edge length L. The notched cutting edge 32b and the roughing cutting edge 34b have notches or roughing portions on a portion of the shank 12 side. The notched cutting edge 32c and the roughing cutting edge 34c have notches or roughing portions on a portion of the bottom cutting edge 22 side. The notches or roughing portions are preferably provided, for example, within a range of 5% to 65% of the cutting edge length L in the tool axis direction from the shank side end P3 to the bottom cutting edge 22 side at a distance of 70% of the cutting edge length L; or within a range of 5% to 65% of the cutting edge length L in the range from the bottom cutting edge side end P2 to the shank 12 side at a distance of 70% of the cutting edge length L; or within a range of 5% to 65% of the cutting edge length L in the range from the center of the cutting edge length L in the tool axis direction to both directions at a distance of 35% of the cutting edge length L. For the above... Figures 7-9 The end mills 10 with 4 to 6 flutes shown, or end mills 10 with 7 or more flutes not shown, can also be set as notching or roughing flutes.

[0088] Figure 11 This is an unfolded diagram showing the outer peripheral cutting edge 20 of a 3-flute end mill 10 unfolded around its axis. The circular arc edge 2 corresponds to the outer peripheral cutting edge 20a, the left-hand spiral edge 3 corresponds to the outer peripheral cutting edge 20b, and the right-hand spiral edge 1 corresponds to the outer peripheral cutting edge 20c. Moreover, it is preferable to set the circumferential positions of edges 1 to 3 such that the equally divided positions of edges 1 to 3 in the circumferential direction exist within the following range: assuming that edges 1 to 3 are extended along the tool axis direction with a certain helix angle and a certain curvature (dashed line portion), the position is between a position further away from the bottom edge end P2 towards the front end and away from the cutting edge length L by 1 / 4, and a position further away from the shank end P3 towards the shank 12 and away from the cutting edge length L by 1 / 4. In other words, with the bottom edge end P2 as a reference, the direction towards the shank 12 is set positive and falls within the range of -0.25L to 1.25L. Specifically, the equal division position is the position where the interval between blade 1 and blade 2 is set to D1, the interval between blade 2 and blade 3 is set to D2, and the interval between blade 3 and blade 1 is set to D3, resulting in the position where D1 = D2 = D3. Figure 11 The circumferential positions of blades 1 to 3 are set at the center of blade length L, that is, at a distance of 0.5L from the bottom edge end P2, forming an equal division of D1 = D2 = D3.

[0089] The bottom cutting edge 22 of the end mill 10 is, for example, Figure 12 As shown in the diagram. Figure 12 The bottom edge 42a to 42c of the "no center edge" refers to the case where none of them have a center edge. Figure 12The bottom edges 44a to 44c of the left photograph of "having a center edge" are a case where one bottom edge 44c has a center edge reaching the vicinity of the tool axis, and the bottom edges 46a to 46c of the right photograph are a case where three bottom edges 46a to 46c all have a center edge reaching the vicinity of the tool axis. The bottom edge 22 of the end mill 10 can be any one of the bottom edges 42a to 42c, the bottom edges 44a to 44c, and the bottom edges 46a to 46c, Figure 1 are three bottom edges having a center edge.

[0090] According to such an end mill 10, as the peripheral cutting edges 20, there are provided Figure 2 three kinds of cutting edges of the curved edge BS, the left-hand edge BL, and the right-hand edge BR as illustrated, and adjacent peripheral cutting edges 20 are constituted by different kinds of cutting edges, so that the intervals of the adjacent peripheral cutting edges 20 are unequal intervals and continuously change in the axial direction, and the directions of the cutting forces are also different, so that resonance can be suppressed and an antivibration effect can be appropriately obtained. In addition, by providing the curved edge BS, compared with the case where there are only the right-hand edge BR and the left-hand edge BL, the generation of burrs and the like can be further appropriately suppressed, and since the cutting force acts in the direction of the inside of the curved shape, the chattering in the plate thickness direction of the workpiece can be suppressed. In addition, the curved edge BS forms a smooth curved shape, so that compared with a chevron shape, the retention of chips can be suppressed, the restriction of the machining conditions can be relaxed, and the like.

[0091] In addition, in a case where the helix angle a of the right-hand edge BR is in a range of 1° to 15° and the helix angle β of the left-hand edge BL is in a range of 1° to 15°, an antivibration effect, a suppression effect of burrs and the like, and a suppression effect of chattering can be appropriately obtained. That is, if the helix angles a and β are large, burrs and the like are easily generated and chattering becomes large, so that it is difficult to appropriately suppress regardless of the presence or absence of the curved edge BS.

[0092] In addition, as illustrated in Figure 10 in a case where the three peripheral cutting edges 20 are constituted by any one of the ordinary edge 30, the notched edge 32, and the roughing edge 34, an end mill 10 of an appropriate cutting edge shape can be adopted according to the use for finishing, semi-finishing, roughing, and the like, or the material of the workpiece, and the like. For example, in a case where the workpiece is CFRP or CFRTP, it is possible to flexibly use according to the kind of fiber, the fiber volume content rate, and the like.

[0093] In addition, for example, as illustrated in Figure 11As shown, the circumferential positions of cutting edges 1 to 3 are set such that the three outer peripheral cutting edges 20 (cutting edges 1 to 3) are equally divided in the circumferential direction. The equally divided positions exist in the tool axis direction between a position 1 / 4 away from the cutting edge length L from the bottom cutting edge end P2 towards the front end and a position 1 / 4 away from the cutting edge length L from the shank end P3 towards the shank 12. In other words, with the bottom cutting edge end P2 as the reference, the direction towards the shank 12 is set positive and located in the range of -0.25L to 1.25L. In this case, compared with the case outside this range, a superior surface roughness can be obtained.

[0094] Furthermore, when the angle difference δ between the helix angle α of the right-hand cutting edge BR and the helix angle β of the left-hand cutting edge BL is within ±5°, the back face wear width is smaller compared to cases where the angle difference δ exceeds ±5°. This ensures tool life while achieving the vibration damping effect from unequal division and the burr suppression effect from the curved cutting edge BS.

[0095] In addition, in such Figure 12 When at least one of the multiple bottom cutting edges 22 provided at the front end of the tool, such as bottom cutting edges 44a-44c or bottom cutting edges 46a-46c, has a center cutting edge that reaches near the tool axis, plunge milling can be performed, thus improving the versatility of the tool.

[0096] Furthermore, the end mill 10, which has three types of cutting edges as the outer peripheral cutting edge 20, such as the right-hand cutting edge BR, the left-hand cutting edge BL, and the curved cutting edge BS, is as follows: Figures 6-9 As shown, it is preferably applied when the number of cutting edges of the outer peripheral cutting edge 20 is 3 or more but less than 6.

[0097] In addition, the end mill 10 is made of superhard alloy, and the surface of the cutting edge 14 with the outer peripheral cutting edge 20 is covered with a diamond coating 24, thus achieving excellent cutting durability.

[0098] Figure 13 This diagram illustrates the positional relationships of the present invention, such as the end mill 10 described above, which has a right-handed cutting edge 1, a curved cutting edge 2, and a left-handed cutting edge 3, as well as a conventional product with four cutting edges that alternately have cutting edges 1 and 2 with different directions of twist. The cutting forces of each cutting edge 1 to 3 and each cutting edge 1 to 2 in the unfolded diagram are represented by white arrows, and the workpiece W is subjected to trimming (peripheral cutting). Figure 13 The direction of the white arrow shown on the upper layer indicates the direction of the cutting force, and the thickness indicates the magnitude of the cutting force. The direction and magnitude of the cutting force of the curved blade 2 of the product of this invention change depending on the axial position. Figure 13The positional relationship shown in the lower layer is that the workpiece W is on the near side (the front side of the paper), and the blades 1 to 3 or the tool having the blades 1 to 2 are on the inner side (the back side of the paper). The direction and magnitude of the cutting force of the three blades 1 to 3 of the product of the present application vary, and thus, the resonance can be suppressed, and the antivibration effect can be appropriately obtained as in the conventional product having the blades 1 and 2 having different twist directions. In addition, in the conventional product, the blade 1 of the right-hand blade is an obtuse angle on the upper surface side of the workpiece W, and the blade 2 of the left-hand blade is an obtuse angle on the lower surface side of the workpiece W, and thus, burrs and the like are easily generated in the portions indicated by asterisks, but according to the product of the present application, the curved blade 2 is cut at an acute angle with respect to both the upper and lower surfaces of the workpiece W, and thus, the burrs and the like generated on the side where the blades 1 and 3 are cut at an obtuse angle can be removed, and the generation of burrs and the like can be appropriately suppressed.

[0099] In addition, as shown in Figure 14 the conventional product in which the right-hand blade 50 and the left-hand blade 52 are adjacently provided in an alternating helical blade shape in a manner that they overlap each other in the tool axis direction, the chips are easily stagnated at the overlapping portions of the helical blades 50 and 52, and sometimes the machining conditions are limited due to the chip clogging. In addition, if the tool is shifted to the left-hand blade 52 side as in the position shift 1 and only the right-hand blade 50 performs the cutting machining, burrs and the like are likely to be generated on the upper surface of the workpiece W as indicated by asterisks, and if the tool is shifted to the right-hand blade 50 side as in the position shift 2 and only the left-hand blade 52 performs the cutting machining, burrs and the like are likely to be generated on the lower surface of the workpiece W as indicated by asterisks. In addition, if the movement is made on the curved surface portion by machining programming, it becomes up machining (Japanese: kakemodarigaki) or down machining (Japanese: kakemodarigaki), and thus, the tool is easily subjected to the blade winding.

[0100] Next, several cutting machining tests performed in order to specifically clarify the effects of the present application will be described.

[0101] Figure 15 is a drawing illustrating comparative products (test products No 1 to No 4) and the product of the present application (test product No 5) used when the cutting machining test was performed, and the blades 1 to 3 refer to three peripheral cutting blades. The product of the present application (test product No 5) is an end mill 10 in which the three blades 1 to 3 are constituted by the curved blade BS, the left-hand blade BL, and the right-hand blade BR described above. Figure 2 Figure 3 ​The three edges 1 to 3 of the test product No. 1 are straight edges, the three edges 1 to 3 of the test product No. 2 are right-hand edges, and the three edges 1 to 3 of the test product No. 3 are left-hand edges. In addition, the three edges 1 to 3 of the test product No. 4 are a straight edge, a left-hand edge, and a right-hand edge. The edge length L of the test products No. 1 to No. 5 is 12 mm, the edge diameter Φ is 6 mm, the material is superhard alloy, and the surface is coated with a diamond film 24. In addition, the helix angles α and β of the right-hand edges and the left-hand edges, including the product of the present application (test product No. 5), are 5°.

[0102] Figure 16 is a graph showing the resultant force F of the resistance values measured in the cutting test, the resultant force F of the feed component Fx in the tool feed direction, the main component Fy in the direction at right angles to the machined surface, and the back component Fz in the tool axis direction (the plate thickness direction of the machined material). The resultant force F corresponds to the load applied to the workpiece W. Figure 17 is a graph showing the positional relationship between the workpiece W and the tool T in the cutting test, and the outer peripheral surface of the workpiece W is deburred at a position protruding 30 mm from the workbench. Wf is the machined surface. Figure 18 is a graph showing the amplitude of the resultant force F measured in the cutting test, and the amplitude is the difference between the maximum value and the minimum value of the resultant force F.

[0103] Furthermore, the results of the cutting test and the measurement of the amplitude of the resultant force F under the machining conditions shown in Figure 19 Figure 20 . Figure 20 The ratio (%) is the value when the amplitude of the test product No. 1 is taken as 100%. In addition, Figure 21 is a graph showing the amplitude of the resultant force F measured in the cutting test, and the amplitude is the difference between the maximum value and the minimum value of the resultant force F. Figure 20 From the results, it is found that the amplitude of the product of the present application (test product No. 5) is about 28% smaller than that of the comparative product (test product No. 1) in which the three edges 1 to 3 are straight edges. The test product No. 2 in which the three edges 1 to 3 are right-hand edges and the test product No. 3 in which the three edges 1 to 3 are left-hand edges have a back component Fz in the axial direction, and thus the amplitude is about 23 to 24% larger than that of the test product No. 1. In addition, the test product No. 4 in which the three edges 1 to 3 are a straight edge, a left-hand edge, and a right-hand edge has an amplitude about 10% smaller than that of the test product No. 1, but the reduction is small compared with the product of the present application (test product No. 5).

[0104] Figures 22-24 is a graph showing the results obtained by performing other cutting tests, Figure 22 is a graph showing the three test products No. 1 to No. 3. The test product No. 1 is a 4-edge herringbone-shaped conventional product, the test product No. 2 is a 4-edge herringbone-shaped product in which the helix angles α and β of the right-hand edges and the left-hand edges are 5°, and the test product No. 3 is a 4-edge herringbone-shaped product in which the helix angles α and β of the right-hand edges and the left-hand edges are 10°. Figure 15 ​the same as the 3-blade comparative product of Test No. 4 of the above-mentioned Figure 15 the 3-blade product of the present application which is the same as Test No. 5 of the above-mentioned

[0105] Moreover, under the two machining conditions (Condition 1 and Condition 2) shown in Figure 23 , deburring machining was performed on CFRTP as the machined material, and the occurrence of burrs was investigated. In Condition 1 and Condition 2, the cutting speed and the feed per 1 blade were different, and in comparison with Condition 1, the cutting speed was faster and the feed per 1 blade was smaller in Condition 2. Figure 24 is a photograph showing the cutting edge shape and the occurrence of burrs of Test Nos. 1 to 3. Figure 22 From this result, it was found that in Condition 1, according to the product of the present application of Test No. 3, the burrs were greatly reduced in comparison with the herringbone-shaped conventional product (Test No. 1), and the burrs were also reduced in comparison with the comparative product of Test No. 2. In the case of Condition 2 in which the cutting speed was faster and the feed per 1 blade was smaller, in the herringbone-shaped conventional product (Test No. 1), chip jamming occurred at the intersection of the spiral blades and machining could not be performed. If the comparative product of Test No. 2 and the product of the present application of Test No. 3 are compared, as in the case of Condition 1, the burrs of the product of the present application were smaller.

[0106] Figures 25-28 is a graph showing the test results of other cutting machining tests, Figure 25 is a graph showing six kinds of Test Nos. 1 to 6. Test Nos. 1 to 6 are 3-blade, and Test Nos. 2 to 6 are products of the present application which are the same as Test No. 5 of the above-mentioned Figure 15 , and are provided with a circular-arc blade A of Figure 3 , and have a right-hand spiral blade BR and a left-hand spiral blade BL, and the spiral angles a, b of the right-hand spiral blade BR and the left-hand spiral blade BL are different in the range of 1° to 35°. The width dimension a = b of the circular-arc blade A is 0.08 mm. Test No. 1 is a comparative product which has the above-mentioned circular-arc blade A, and instead of the right-hand spiral blade BR and the left-hand spiral blade BL, has two straight blades whose spiral angles a, b are 0°. The blade length L of this Test No. 1 to No. 6 is 3 mm, the blade diameter Φ is 6 mm, the material is super-hard alloy, and the surface is coated with a diamond coating film 24.

[0107] Moreover, under the machining conditions shown in Figure 26 , cutting machining was performed while changing the cutting speed, the occurrence of chip winding and chatter was observed, and the results shown in Figure 27 were obtained. From Figure 27It is known that in the case of the comparative product of the test product No. 1 in which the helix angles a, β are 0°, the chips are difficult to curl, and the entanglement of the chips is observed at a cutting speed of 150 m / min or more. On the other hand, in the case of the test product No. 5 in which the helix angles a, β are 25°, the machining becomes impossible due to chatter when the cutting speed reaches 250 m / min or more, and in the case of the test product No. 6 in which the helix angles a, β are 35°, the machining becomes impossible due to chatter when the cutting speed reaches 150 m / min or more. That is, according to the test products No. 2 to No. 6 of the product of the present application having the right-hand cutting edge BR and the left-hand cutting edge BL in which the helix angles a, β are 1° or more, although the entanglement of the chips is not observed at all conditions of the cutting speed of 50 to 400 m / min, if the helix angles a, β exceed 15°, the chatter is easily generated, and therefore, the helix angles a, β of the right-hand cutting edge BR and the left-hand cutting edge BL are preferably in the range of 1° to 15°. Figure 28 is a photograph illustrating the chips in the case where the test product No. 1 in which the helix angles a, β are 0° and the test product No. 2 in which the helix angles a, β are 1° are subjected to the cutting machining at a cutting speed of 400 m / min, and in the case of the comparative product of the test product No. 1, the chips are difficult to curl, and therefore, the chips are entangled with each other to become large, and the dischargeability is deteriorated.

[0108] Figures 29-31 is a graph showing the results of other cutting machining tests, Figure 29 is a graph showing three 3-edge test products No. 1 to No. 3. The test products No. 1 to No. 3 are as shown in the tool image of Figure 10 , and as the peripheral cutting edges 20, the ordinary edges 30, the notched edges 32 or the rough machining edges 34 are provided, and all of them are the same product of the present application as the test product No. 5 of Figure 15 , and as the curved edge BS, the circular arc edge A of Figure 3 is provided, and further, the right-hand cutting edge BR and the left-hand cutting edge BL are provided. The edge length L of the test products No. 1 to No. 3 is 12 mm, the edge diameter Φ is 6 mm, the material is super hard alloy, and the surface is coated with a diamond coating film 24.

[0109] Further, the cutting machining is performed under the machining conditions shown in Figure 30 , the vibration waveform of the resistance value of the resultant force F, the maximum value and the amplitude of the resultant force F, the ratio in the case where the maximum value and the amplitude of the test product No. 1 are set to 100%, the generation condition of burrs on the upper surface side and the lower surface side of the machined surface are investigated, and Figure 31The results shown. From the results, it is known that, according to the test piece No 3 provided with the roughing blade 34, although the maximum value and amplitude of the resultant force F are about 49 to 50% smaller than those of the test piece No 1 of the ordinary blade 30, burrs on the upper surface side and the lower surface side are both larger, and it is preferable to be used for roughing, for example. According to the test piece No 2 provided with the notched blade 32, both the maximum value and amplitude of the resultant force F are about 43% smaller than those of the test piece No 1 of the ordinary blade 30, on the other hand, burrs on the upper surface side and the lower surface side are both larger, but smaller than those of the test piece No 3 of the roughing blade 34, and it is preferable to be used for semi-finishing, for example.

[0110] Figures 32-36 is a graph showing the results of other cutting test, Figure 32 and Figure 33 are graphs showing five test pieces No 1 to No 5 in which the three peripheral cutting edges 20 are divided into equal parts at different equal division positions. The test pieces No 1 to No 5 are all the products of the present application which are the same as the test piece No 5 of the above-mentioned Figure 15 , and are provided with the circular arc blade A of Figure 3 as the bending blade BS, and have the right-hand blade BR and the left-hand blade BL. Figure 33 The blade 1 to blade 3 correspond to the three peripheral cutting edges 20, the blade 1 is the right-hand blade BR, the blade 2 is the circular arc blade A, and the blade 3 is the left-hand blade BL. In the test piece No 1, the equal division position is at a position 2 / 4 of the blade length L from the bottom blade side end portion P2 toward the tip side, that is, at a position -0.5L in the direction toward the shank portion 12 side taken as positive with the bottom blade side end portion P2 as a reference, and the intervals D1=D2=D3 of the blade 1 to blade 3. In the test piece No 2, the equal division position is at a position 1 / 4 of the blade length L from the bottom blade side end portion P2 toward the tip side, that is, at a position -0.25L in the direction toward the shank portion 12 side taken as positive with the bottom blade side end portion P2 as a reference, and the intervals D1=D2=D3 of the blade 1 to blade 3. In the test piece No 3, the equal division position is at a position 2 / 4 of the blade length L from the bottom blade side end portion P2 toward the shank portion 12 side, that is, at the center of the blade length L, and the intervals D1=D2=D3 of the blade 1 to blade 3. In the test piece No 4, the equal division position is at a position 1 / 4 of the blade length L from the shank side end portion P3 toward the shank portion 12 side, that is, at a position 1.25L in the direction toward the shank portion 12 side taken as positive with the bottom blade side end portion P2 as a reference, and the intervals D1=D2=D3 of the blade 1 to blade 3. In the test piece No 5, the equal division position is at a position 2 / 4 of the blade length L from the shank side end portion P3 toward the shank portion 12 side, that is, at a position 1.5L in the direction toward the shank portion 12 side taken as positive with the bottom blade side end portion P2 as a reference, and the intervals D1=D2=D3 of the blade 1 to blade 3. Figure 33is a positional relationship in the case of the test piece No 3 in which the position is at 2 / 4 of the blade length L and becomes the interval D1=D2=D3. The blade length L of the test pieces No 1 to No 5 is 6 mm, the blade diameter Φ is 6 mm, the material is super hard alloy, and the surface is coated with a diamond coating film 24.

[0111] Moreover, in Figure 34 the processing conditions shown, cutting processing was performed while changing the feed amount per 1 blade, the maximum height Rz was measured as the roughness of the processed surface, and the results shown in Figure 35 and Figure 36 were obtained. Figure 36 is a graph showing the roughness of the processed surface by chart comparison. From this result, in the case of the test piece No 1 in which the equally divided position is at the position of -0.5L with the direction toward the shank portion 12 side being positive based on the end portion P2 of the bottom blade side and the test piece No 5 in which the equally divided position is at the position of 1.5L, the roughness of the processed surface was greater than 12 μm in all conditions in which the feed amount per 1 blade was 0.04 mm / t to 0.12 mm / t, and the roughness of the processed surface became worse as the feed amount per 1 blade was greater. On the contrary, in the case of the test pieces No 2 to No 4 in which the equally divided position was at -0.25L to 1.25L with the direction toward the shank portion 12 side being positive based on the end portion P2 of the bottom blade side, the roughness of the processed surface was in the range of about 5 μm to 8 μm in all conditions in which the feed amount per 1 blade was 0.04 mm / t to 0.12 mm / t, which was about 40% to 50% of the roughness of the test pieces No 1 and No 5. From this result, it was found that the equally divided position is preferably in the range of -0.25L to 1.25L with the direction toward the shank portion 12 side being positive based on the end portion P2 of the bottom blade side, that is, in the range between the position of 1 / 4 of the blade length L from the end portion P2 of the bottom blade side toward the tip side and the position of 1 / 4 of the blade length L from the end portion P3 of the shank side toward the shank portion 12 side.

[0112] Figures 37-40 is a graph showing the results of other cutting processing tests, Figure 37 and Figure 38 is a graph showing four kinds of test pieces No 1 to No 4 in which the angle difference δ of the helix angles α, β of the right-hand blade BR and the left-hand blade BL is different. The test pieces No 1 to No 4 are all the products of the present application which are the same as the test piece No 5 of the above Figure 15 , are provided with the circular arc blade A of Figure 3 as the curved blade BS, and have the right-hand blade BR and the left-hand blade BL. Figure 38Cutting edges 1 through 3 correspond to three outer circumferential cutting edges 20. Edge 1 is a right-handed cutting edge BR, edge 2 is an arc-shaped cutting edge A, and edge 3 is a left-handed cutting edge BL. The width of the arc-shaped cutting edge A is a = b = 0.26 mm. In test item No. 1, the helix angle α of the right-handed cutting edge BR is 5°, the helix angle β of the left-handed cutting edge BL is 5°, and the angle difference δ is 0°. In test item No. 2, the helix angle α of the right-handed cutting edge BR is 7.5°, the helix angle β of the left-handed cutting edge BL is 5°, and the angle difference δ is 2.5°. In test item No. 3, the helix angle α of the right-handed cutting edge BR is 10°, the helix angle β of the left-handed cutting edge BL is 5°, and the angle difference δ is 5°. In test item No. 4, the helix angle α of the right-handed cutting edge BR is 12.5°, the helix angle β of the left-handed cutting edge BL is 5°, and the angle difference δ is 7.5°. The test specimens No.1 to No.4 have a blade length L of 12mm, a blade diameter Φ of 6mm, are made of superhard alloy, and are coated with a diamond coating 24 on the surface.

[0113] Moreover, in Figure 39 Cutting was performed under the conditions shown, and the wear width of the flank was measured. Figure 40 The results are shown. From these test results, it can be seen that in the case of test specimen No.4 with an angle difference δ of 7.5°, the flank wear width is greater than 0.13 mm. In contrast, in the case of test specimens No.1 to No.3 with an angle difference δ of 0° to 5°, the flank wear width is less than 0.06 mm, which is less than 50% of that of test specimen No.4, resulting in excellent tool life. From these results, it is determined that the angle difference δ between the helix angles α and β of the right-hand cutting edge BR and the left-hand cutting edge BL is preferably set within ±5°.

[0114] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, these are only one embodiment, and the present invention can be implemented in various ways with modifications and improvements based on the knowledge of those skilled in the art.

[0115] Explanation of reference numerals in the attached figures

[0116] 10: End mill 12: Shank 14: Cutting edge 20a: Outer peripheral cutting edge (bent edge) 20b: Outer peripheral cutting edge (left-handed edge) 20c: Outer peripheral cutting edge (right-handed edge) 22a, 22b, 22c: Bottom cutting edge (with center cutting edge) 24: Diamond coated 30a, 30b, 30c: Standard cutting edge 32a, 32b, 32c: Notched cutting edge 34a, 34b, 34c: Roughing cutting edge 42a, 42b, 42c: Bottom cutting edge (without center cutting edge) 44a, 44b: Bottom cutting edge (without center cutting edge) 44c: Bottom cutting edge (with center cutting edge) 46a, 46b, 46c: Bottom cutting edge (with center cutting edge) BS: Bent edge BL: Left-handed edge BR: Right-handed edge α: Helix angle of the right-handed edge β: Helix angle of the left-handed edge δ: Angle difference L: Cutting edge length P2: Bottom cutting edge side end P3: Shank side end.

Claims

1. A ball end mill (10) having a plurality of peripheral cutting edges (20a, 20b, 20c) which, when machining a workpiece surface having two ends separated in the axial direction of the ball end mill (10), are moved in a direction substantially perpendicular to the axial direction, i.e., a feed direction, with respect to the workpiece surface while one of the shank side and the bottom edge side of the peripheral cutting edges (20a, 20b, 20c) is positioned at one of the two ends and the other of the shank side and the bottom edge side is positioned at the other of the two ends, characterized in that, as the peripheral cutting edges (20a, 20b, 20c), there are provided three kinds of cutting edges, a right-hand edge (20c, BR) which is right-hand, a left-hand edge (20b, BL) which is left-hand, and a curved edge (20a, BS) which changes in the middle of the twist direction from right-hand on the shank side to left-hand on the bottom edge side or from right-hand on the shank side to left-hand on the bottom edge side, the curved edge forming a curved shape curved in a circular arc or bow shape in an expanded view expanded around an axis center, and a cutting edge provided on the concave side of the curved shape, adjacent peripheral cutting edges (20a, 20b, 20c) are composed of different kinds of cutting edges.

2. The ball end mill (10) according to claim 1, characterized in that, the helix angle (α) of the right-hand edge (20c, BR) is in the range of 1° to 15°, the helix angle (β) of the left-hand edge (20b, BL) is in the range of 1° to 15°.

3. The ball end mill (10) according to claim 1 or 2, characterized in that, the plurality of peripheral cutting edges (20a, 20b, 20c) are composed of any one of a normal edge (30a, 30b, 30c), a notched edge (32a, 32b, 32c), and a roughing edge (34a, 34b, 34c).

4. The ball end mill (10) according to claim 1 or 2, characterized in that, equally divided positions at which the peripheral cutting edges (20a, 20b, 20c) are equally divided in the circumferential direction exist within a range from a position where the peripheral cutting edge (20a, 20b, 20c) is further distanced from the end side of the edge length (L) by 1 / 4 in the tool axis direction from the bottom edge side end portion (P2) of the peripheral cutting edge (20a, 20b, 20c) to a position where the peripheral cutting edge (20a, 20b, 20c) is further distanced from the shank side of the edge length (L) by 1 / 4 in the tool axis direction from the shank side end portion (P3) of the peripheral cutting edge (20a, 20b, 20c).

5. The ball end mill (10) according to claim 1 or 2, characterized in that, the angle difference (δ) between the helix angle (α) of the right-hand edge (20c, BR) and the helix angle (β) of the left-hand edge (20b, BL) is within ±5°.

6. The ball end mill (10) according to claim 1 or 2, characterized in that, At least one of a plurality of bottom edges (22a, 22b, 22c; 44a, 44b, 44c; 46a, 46b, 46c) provided continuously with the peripheral cutting edges (20a, 20b, 20c) at the front end of the tool has a center edge reaching the vicinity of the tool axis.

7. The end mill (10) according to claim 1 or 2, characterized in that The number of edges of the peripheral cutting edges (20a, 20b, 20c) is more than 3 and less than 6.

8. The end mill (10) according to claim 1 or 2, characterized in that The surface of an edge portion (14) in which the peripheral cutting edges (20a, 20b, 20c) are provided is coated with a diamond coating film (24).

9. The end mill (10) according to claim 1 or 2, characterized in that The end mill (10) is composed of super-hard alloy.

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