Ball end mill

Abstract

Provided is a ball end mill which is suitable for finish machining and which, in cutting machining using a plane perpendicular to the tool rotation axis, such as the bottom surface of a die at the tip of a tool, can obtain a machined surface having excellent glossiness, and can omit a polishing step or reduce the number of polishing steps. In the present invention, a plurality of chip discharge grooves (2) are formed on the outer periphery of a tool body (1), the chip discharge grooves (2) being open at the tip and facing the tool base end side from the tool tip end side, and a ball blade (5) is provided at each of the ridge lines where the rake surfaces (3) of the chip discharge grooves (2) intersect with the tip flank surfaces (4) of the tool body (1). The tool tip is provided with a convex tip surface (6) that intersects the tool rotation axis (a) of the tool body (1), and the intersecting ridge section between the tip surface (6) and the rake surface (3) constitutes a center-side cutting edge (7) that is provided so as to be connected to the ball edge (5).

Description

Technical Field

[0001] The invention relates to a ball end mill. Background Art

[0002] Ball-end mills are widely used in the fields of mold processing and component processing. The front end of the tool has a ball-end blade with a hemispherical arc-shaped rotation trajectory. The ball-end blade with appropriately designed rake angle and back angle is used to cut complex curved surfaces or the draft surface (inclined plane) of the mold, thereby obtaining a good processed surface.

[0003] However, there is a problem that the front end portion of the ball end mill (the top of the arc-shaped ball end blade and its vicinity) has poorer cutting performance than the outer peripheral portion of the ball end blade, making it difficult to obtain a good machined surface when machining a plane perpendicular to the tool rotation axis, such as the bottom surface of a mold.

[0004] Therefore, a ball end mill for finishing, as shown in Patent Document 1, has been proposed for the purpose of obtaining a glossy and good finished surface even when machining a plane perpendicular to the tool rotation axis, such as the bottom surface of a mold.

[0005] Patent Document 1: Japanese Patent Application Publication No. 2000-233311

[0006] In the ball end mill of the above-mentioned patent document 1, the two-edged ball end cutting edge is arranged at an upper eccentric position, and the chisel edge angle of the chisel edge (chiseledge) formed by the back cutting surface of the two-edged ball end cutting edge is set to be greater than 155 degrees, or the ratio of the interval between the inner edges of the front cutting surface of the two cutting edges formed by the cut on the ball end cutting edge and the chisel edge length is set to 1 / 7 to 1 / 3, and cutting processing is performed on a plane perpendicular to the tool rotation axis, such as the bottom surface of the mold, by the cutting action based on the chisel edge.

[0007] However, ball-end mills with chisel edges have been widely used. Since the chisel edge is a cross ridge where the back cutting surfaces of the ball-end cutting edges intersect each other at a large obtuse angle, its rake angle forms a large negative rake angle, causing gnawing on the machined surface. Therefore, even if the angle (chisel edge angle) and length of the chisel edge are adjusted to appropriate values ​​as disclosed in the above-mentioned patent document 1, it is difficult to obtain a machined surface (plane) with excellent gloss to the extent that the grinding process (finishing treatment) can be omitted. Therefore, the current situation is that the grinding process (finishing treatment) must be performed after the cutting process. Summary of the invention

[0008] The present invention has been completed in view of the current situation, and its purpose is to provide a ball nose end mill suitable for finishing, which can obtain a machined surface with excellent glossiness during cutting of a plane perpendicular to the tool rotation axis, such as the bottom surface of a mold at the front end of the tool, and can omit the grinding process or reduce the grinding processing time.

[0009] The gist of the present invention will be described with reference to the accompanying drawings.

[0010] A ball-end milling cutter, which has a plurality of chip discharge grooves 2 formed on the outer periphery of a tool body 1, which are open at the front end and extend from the front end side of the tool toward the base end side of the tool, and the front cutting edge 3 of the chip discharge groove 2 and the front end back cutting edge 4 of the tool body 1 are respectively provided with ball-end cutting edges 5. It is characterized in that the ball-end milling cutter is provided with a convex front end face 6 intersecting with the tool rotation axis a of the tool body 1 at the front end portion of the tool, and the front end face 6 and the intersecting ridgeline of the front cutting edge 3 constitute a center side cutting edge 7 connected to the ball-end cutting edge 5.

[0011] In addition, the ball end mill according to technical solution 1 is characterized in that the front end face 6 is arranged to be connected to the front end back cutting face 4 and the respective front cutting face 3 between the respective front end back cutting face 4 of a pair of the ball end cutting edges 5 which are arranged 180 degrees rotationally symmetrically relative to the tool rotation axis a.

[0012] In addition, the ball end mill according to technical solution 2 is characterized in that the front end face 6 is constructed to include the tool rotation axis a, and when observed from the front end of the tool, the contour obtained by connecting any point on the center side cutting edge 7 on one side with any point on the center side cutting edge 7 on the other side with a straight line is a mountain shape, wherein the center side cutting edge 7 on one side is connected to one of the pair of ball end cutting edges 5 passing through the vicinity of the tool rotation axis a, and the center side cutting edge 7 on the other side is connected to the other of the pair of ball end cutting edges 5 passing through the vicinity of the tool rotation axis a.

[0013] In addition, the ball end mill according to technical solution 3 is characterized in that the front end face 6 is constructed to include the tool rotation axis a, and when observed from the front end of the tool, the contour obtained by connecting the intersection of the center side cutting edge 7 on one side and the ridge line 10 on one side and the intersection of the center side cutting edge 7 on the other side and the ridge line 10 on the other side with a straight line is a mountain shape, and the maximum height of the mountain shape is less than 6 μm, wherein the center side cutting edge 7 on one side is connected to one of the pair of ball end cutting edges 5, the ridge line 10 on one side is formed by the front end face 6 and the front end back cutting edge 4 on one side, and the center side cutting edge 7 on the other side is connected to the other of the pair of ball end cutting edges 5, and the ridge line 10 on the other side is formed by the front end face 6 and the front end back cutting edge 4 on the other side.

[0014] In addition, the ball end mill according to any one of technical solutions 1 to 4 is characterized in that the center side cutting edge 7 is set near the tool rotation axis a.

[0015] In addition, the ball-end milling cutter according to any one of technical solutions 1 to 4 is characterized in that the front end face 6 is connected to the front end back cutting edge 4, and the front end face 6 is set in any of the following ways: when observed from the front end of the tool, when the ball end cutting edge 5 side connected to the center side cutting edge 7 is set as the positive side and the opposite side is set as the negative side relative to the center side cutting edge 7 or the extension line 8 of the center side cutting edge 7 passing through the tool rotation axis a, the intersection P2 exists on the negative side, or exists on the direction of the intersection P1 and the intersection P2 along the center side cutting edge 7. The upward spacing distance X is the positive side that is greater than 0% and less than 10% of the outer diameter of the tool, wherein the intersection P1 is the intersection of the center side cutting edge 7 or the extension line 8 of the center side cutting edge 7 when viewed from the front end of the tool and the perpendicular line 9 to the center side cutting edge 7 or the extension line 8 of the center side cutting edge 7 passing through the tool rotation axis a, and the intersection P2 is the intersection of the ridge line 10 on the side away from the ball head cutting edge 5 among the ridge lines 10 formed by the front end face 6 and the front end back cutting edge 4 when viewed from the front end of the tool and the edge of the front end of the chip discharge groove 2 having the ball head cutting edge 5 and the center side cutting edge 7 connected to the ball head cutting edge 5.

[0016] In addition, the ball-end milling cutter according to technical solution 5 is characterized in that the front end face 6 is connected to the front end flank face 4, and the front end face 6 is set in any of the following ways: when viewed from the front end of the tool, when the ball-end edge 5 side connected to the center side cutting edge 7 is set as the positive side and the opposite side is set as the negative side relative to the perpendicular line 9 passing through the center side cutting edge 7 or the extension line 8 of the center side cutting edge 7 passing through the tool rotation axis a, the intersection point P2 exists on the negative side, or exists between the intersection point P1 and the intersection point P2 in the direction along the center side cutting edge 7. The positive side at a spacing X of more than 0% and less than 10% of the outer diameter of the tool, wherein the intersection P1 is the intersection of the center side cutting edge 7 or the extension line 8 of the center side cutting edge 7 when viewed from the front end of the tool and the perpendicular line 9 to the center side cutting edge 7 or the extension line 8 of the center side cutting edge 7 passing through the tool rotation axis a, and the intersection P2 is the intersection of the ridge line 10 on the side away from the ball end cutting edge 5 among the ridge lines 10 formed by the front end face 6 and the front end back cutting edge 4 when viewed from the front end of the tool and the edge of the front end of the chip discharge groove 2 having the ball end cutting edge 5 and the center side cutting edge 7 connected to the ball end cutting edge 5.

[0017] In addition, the ball-end mill according to any one of technical solutions 1 to 4 is characterized in that, in the front end face 6, when observed from the front end of the tool, the opposing intervals of the two ridges 10 formed by the front end face 6 and the front end back cutting surfaces 4 of each of the pair of ball-end cutting edges 5 arranged 180 degrees rotationally symmetrically relative to the tool rotation axis a are set to the width W of the front end face 6, and the front end face 6 is constructed so that the width W is 0.005 mm≦W≦0.2D, wherein D is the outer diameter of the tool.

[0018] In addition, the ball-end milling cutter according to technical solution 5 is characterized in that, in the front end face 6, when observed from the front end of the tool, the opposing intervals of the two ridges 10 formed by the front end face 6 and the front end back cutting surfaces 4 of each of the pair of ball-end cutting edges 5 arranged 180 degrees rotationally symmetrically relative to the tool rotation axis a are set to the width W of the front end face 6, and the front end face 6 is constructed so that the width W is 0.005mm≦W≦0.2D, wherein D is the outer diameter of the tool.

[0019] In addition, the ball-end milling cutter according to technical solution 6 is characterized in that, in the front end face 6, when observed from the front end of the tool, the opposing intervals of the two ridges 10 formed by the front end face 6 and the front end back cutting surfaces 4 of each of the pair of ball-end cutting edges 5 arranged 180 degrees rotationally symmetrically relative to the tool rotation axis a are set to the width W of the front end face 6, and the front end face 6 is constructed so that the width W is 0.005mm≦W≦0.2D, wherein D is the outer diameter of the tool.

[0020] In addition, the ball-end milling cutter according to technical solution 7 is characterized in that, in the front end face 6, when observed from the front end of the tool, the opposing intervals of the two ridges 10 formed by the front end face 6 and the front end back cutting surfaces 4 of each of the pair of ball-end cutting edges 5 arranged 180 degrees rotationally symmetrically relative to the tool rotation axis a are set to the width W of the front end face 6, and the front end face 6 is constructed so that the width W is 0.005mm≦W≦0.2D, wherein D is the outer diameter of the tool.

[0021] In addition, the ball end mill according to technical solution 8 is characterized in that In the case of, the width W of the front end face 6 is set to 0.01mm≦W≦0.3mm. In the case of , the width W of the front end surface 6 is set to 0.01 mm≦W≦0.2D, where D is the outer diameter of the tool.

[0022] In addition, the ball end mill according to technical solution 9 is characterized in that In the case of, the width W of the front end face 6 is set to 0.01mm≦W≦0.3mm. In the case of , the width W of the front end surface 6 is set to 0.01 mm≦W≦0.2D, where D is the outer diameter of the tool.

[0023] In addition, the ball end mill according to technical solution 10 is characterized in that In the case of, the width W of the front end face 6 is set to 0.01mm≦W≦0.3mm. In the case of , the width W of the front end surface 6 is set to 0.01 mm≦W≦0.2D, where D is the outer diameter of the tool.

[0024] In addition, the ball end mill according to technical solution 11 is characterized in that In the case of, the width W of the front end face 6 is set to 0.01mm≦W≦0.3mm. In the case of , the width W of the front end surface 6 is set to 0.01 mm≦W≦0.2D, where D is the outer diameter of the tool.

[0025] The present invention is constructed as described above, and thus becomes a ball end mill suitable for finishing. This ball end mill can obtain a machined surface with excellent glossiness during cutting of a plane perpendicular to the tool rotation axis, such as the bottom surface of a mold at the front end of the tool, and can omit the grinding process or reduce the grinding processing time. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is an explanatory plan view showing the main parts of this embodiment, viewed from the front end of the tool.

[0027] Figure 2 (a) is an explanatory left side view showing the main parts of this embodiment, Figure 2 (b) is an explanatory front view showing the main parts of this embodiment.

[0028] Figure 3 This is an explanatory plan view showing the main parts of another example 1 of the present embodiment, viewed from the front end of the tool.

[0029] Figure 4 (a) is an explanatory left side view showing the main part of another example 1 of the present embodiment, Figure 4 (b) is an explanatory front view showing the main parts of another example 1 of the present embodiment.

[0030] Figure 5 This is an explanatory plan view showing the main parts of another example 2 of the present embodiment, viewed from the front end of the tool.

[0031] Figure 6 (a) is an explanatory left side view showing the main parts of another example 2 of the present embodiment, Figure 6 (b) is an explanatory front view showing the main parts of another example 2 of the present embodiment.

[0032] Figure 7 This is an explanatory diagram for defining the convex outer shape (contour) of the front end surface of this embodiment.

[0033] Figure 8 This is an explanatory diagram for defining the convex amount of the convex outer shape (contour) of the front end face of this embodiment.

[0034] Fig. 9 This is an example of outline data showing the convex outer shape (outline) of the front end surface of this embodiment.

[0035] Fig.10 1 is an explanatory diagram showing the positive side, the negative side, the spacing distance X, and the width W of the front end surface in this embodiment, viewed from the front end of the tool.

[0036] Fig.11 This is a schematic diagram when viewed from the front end of the tool when the intersection point P2 in this embodiment exists on the positive side and the negative side.

[0037] Fig.12 These are an explanatory plan view and an explanatory front view showing a structural example of the front end surface of this embodiment.

[0038] Fig.13This is a photograph showing an example of the evaluation results of glossiness in Experimental Example 1.

[0039] Fig.14 This is a graph showing the evaluation results of the surface roughness in Experimental Example 1 (measurement results of the arithmetic mean roughness Ra).

[0040] Fig.15 These are photographs showing the results of observation of the processed surface in Experimental Example 1.

[0041] Fig.16 These are photographs showing the evaluation results of the glossiness of the 0° surface of each of the present example and the conventional product in Experimental Example 4.

[0042] Fig.17 This is a graph showing the evaluation results (measurement results of the arithmetic mean roughness Ra) of the surface roughness of the 0° surface at processing times of 20 minutes and 60 minutes for each of the present example and the conventional product in Experimental Example 4.

[0043] Fig.18 This is a graph showing the evaluation results (measurement results of the arithmetic mean roughness Ra) of the surface roughness of the 0° surface and the 45° surface in Experimental Example 4 when the processing time was 20 minutes for each of the present embodiment and the conventional product.

[0044] Description of symbols

[0045] 1: Tool body; 2: Chip discharge groove; 3: Rake face; 4: Front flank face; 5: Ball-end edge; 6: Front face; 7: Center side cutting edge; 8: Extension line; 9: Vertical line; 10: Ridge line; a: Tool rotation axis; X: Spacing distance. DETAILED DESCRIPTION

[0046] The effects of the present invention will be shown with reference to the drawings and preferred embodiments of the present invention will be briefly described.

[0047] In the present invention, since a convex front end face 6 intersecting the tool rotation axis a of the tool body 1 is provided at the front end of the tool, there is no chisel edge with a large negative rake angle, and gnawing due to the chisel edge can be prevented as much as possible.

[0048] In addition, in the present invention, since the intersection ridgeline portion of the front end face 6 and the front cutting edge 3 constitutes a center side cutting edge 7 connected to the ball end cutting edge 5, the center side cutting edge 7 has the same rake angle as the ball end cutting edge 5 and exerts the same high cutting performance as the ball end cutting edge 5.

[0049] Moreover, in the present invention, since the front end face 6 is formed in a convex shape, during the plane processing perpendicular to the tool rotation axis a, even if the perpendicularity of the tool rotation axis a relative to the plane is offset (for example, even if the tool is bent due to cutting resistance and the tool rotation axis a is slightly inclined relative to the plane), the front end face 6 is in contact with the plane, thereby exerting the polishing effect brought about by the sliding contact of the front end face 6 with the cutting surface.

[0050] Thus, in the present invention, in the plane processing perpendicular to or intersecting the tool rotation axis a, the generation of cutting marks caused by the center side cutting edge 7 during cutting processing can be suppressed by the higher cutting performance of the center side cutting edge 7 and the polishing effect based on the sliding contact action of the front end face 6 to the cutting surface, and a processed surface with excellent gloss equal to or higher than that of the case of cutting processing using the ball head edge 5 can be obtained.

[0051] [Example]

[0052] Specific embodiments of the present invention will be described below with reference to the accompanying drawings.

[0053] The present embodiment is a ball-end milling cutter having a plurality of chip discharge grooves 2 formed on the outer periphery of a tool body 1, which are open at the front end and extend from the front end side of the tool toward the base end side of the tool, and ball-end cutting edges 5 are respectively provided at the intersection ridges of the front cutting edge faces 3 of the chip discharge grooves 2 and the front end rear cutting edge 4 of the tool body 1, wherein a convex front end face 6 is provided at the front end portion of the tool, which intersects with the tool rotation axis a of the tool body 1 and protrudes toward the front end side in the direction of the tool rotation axis a, and the intersection ridges of the front cutting edge 6 and the front cutting edge 3 constitute a center side cutting edge 7 connected to the ball-end cutting edge 5.

[0054] Specifically, this embodiment is a case where the ball end mill of the present invention is configured as a double-edged ball end mill (a ball end mill having a pair of ball end cutting edges 5): Figure 1 , Figure 2 As shown, two spiral chip discharge grooves 2 are provided, and ball-end cutting edges 5 are provided at the intersection of two rake faces 3 formed at the front end of the chip discharge groove 2 and the front end clearance face 4 of the tool body 1.

[0055] In addition, the present embodiment is not limited to the structure of the double-edged ball end mill described above, and a multi-edged ball end mill having more than three ball end edges may be formed by providing a ball end edge in addition to a pair (two pieces) of ball end edges 5. In addition, in the figure, the arrow marked with the symbol T indicates the direction of tool rotation.

[0056] More specifically, in the present embodiment, a cutout 11 as a part of the chip discharge groove 2 is formed at the front end of the rake face 3 (the wall surface facing the front side in the rotation direction of the tool) of the chip discharge groove 2, and a cutout surface 12 facing the front side in the rotation direction of the tool is provided, and the cutout surface 12 serves as the rake face 3 at the front end of the tool.

[0057] In addition, in addition to the above structure, this embodiment can also be Figure 3 , Figure 4 As shown in another example 1, a so-called straight-edged ball-end mill is constructed as follows: a linear chip discharge groove 2 is provided without a cutout 11, that is, a cutout surface 12 is not provided and the wall surface of the chip discharge groove 2 facing the front side of the tool rotation direction is constructed as the front cutting edge 3 of the front end of the tool.

[0058] In addition, the present embodiment is configured in a so-called upper eccentric shape in which the center-side cutting edge 7 near the tool rotation axis a is arranged forward in the tool rotation direction relative to the tool rotation axis a when viewed from the tool front end.

[0059] Specifically, the present embodiment is configured as an upper eccentric shape as follows: when viewed from the front end of the tool, the chip discharge groove 2 (cut 11) open at the front end is separated outwardly relative to the tool rotation axis a in a manner that a core portion remains around the tool rotation axis a from the outer peripheral side of the tool, and a center side cutting edge 7 is provided near the tool rotation axis a at the edge of the front end of the chip discharge groove 2 (cut 11).

[0060] Furthermore, the chip discharge groove 2 (notch 11) constituting the upper eccentric shape may be provided from the outer peripheral side of the tool across the tool rotation axis a, or may be provided without crossing the tool rotation axis a.

[0061] In addition, this embodiment is not limited to the structure described, that is, not limited to Figure 1 to Figure 4 The structure of the upper eccentric shape shown, for example, can also be like Figure 5 , Figure 6 As in the other example 2 shown, when viewed from the front end of the tool, the center-side cutting edge 7 near the tool rotation axis a is arranged on the rear side in the tool rotation direction relative to the tool rotation axis a, which is a so-called lower eccentric shape.

[0062] The following is a detailed description of the structure of each part of this embodiment.

[0063] like Figure 1 , Figure 2As shown, the front end relief face 4 of the present embodiment is composed of a first relief face 4a inclined at a specified angle relative to the tool rotation axis a, a second relief face 4b arranged on the rear side of the tool rotation direction of the first relief face 4a and inclined at an angle different from that of the first relief face 4a, and a third relief face 4c arranged on the rear side of the tool rotation direction of the second relief face 4b and inclined at an angle different from that of the second relief face 4b.

[0064] In addition, each ball-end cutting edge 5 (a pair of ball-end cutting edges 5) is provided at the intersection of the first flank surface 4a of each front end flank surface 4 and the rake surface 3 (cut surface 12) facing the front side in the tool rotation direction, as shown in FIG. Figure 1 As shown, each ball-end cutting edge 5 is arranged to be rotationally symmetrical by 180 degrees with respect to the tool rotation axis a.

[0065] As described above, the front end surface 6 is configured as a convex surface that intersects the tool rotation axis a at the tool front end portion and convexly projects toward the front end side in the direction of the tool rotation axis a.

[0066] Specifically, if Figure 1 As shown, the front end face 6 is formed between the front end flank faces 4 (first flank faces 4a) of each ball end cutting edge 5 as a convex surface connected to these front end flank faces 4 (first flank faces 4a) and the front faces 3 of each ball end cutting edge 5, and further, the front end face 6 is connected to the ball end cutting edge 5 at the intersection ridge portion of the front face 3 of each ball end cutting edge 5, and the intersection ridge portion is formed as a center side cutting edge 7 with the same front angle as that of the ball end cutting edge 5.

[0067] In this embodiment, a pair of the center side cutting edges 7 are provided in a 180 degree rotationally symmetrical manner with respect to the tool rotation axis a.

[0068] In addition, the front end surface 6 includes the tool rotation axis a in the plane and is configured as follows: Figure 7 The convex surface as shown, regarding which, when observed from the front end of the tool, the outer shape (contour) obtained by passing through the vicinity of the tool rotation axis a from an arbitrary point A on the center side cutting edge 7 of one side connected to the ball end cutting edge 5 of one of a pair of ball end cutting edges 5 and connecting with a straight line an arbitrary point B on the center side cutting edge 7 of the other side connected to the other ball end cutting edge 5 is in a mountain shape.

[0069] Specifically, the front end face 6 is configured such that the outer shape (outline) is a mountain shape, and the maximum height of the mountain shape is 6 μm or less.

[0070] In addition, in this embodiment, Figure 8 As shown, with the line segment L connecting the point A and the point B as a reference, the difference between the line segment L and the top of the outer shape (contour) is taken as the maximum height (convexity) of the mountain shape.

[0071] In this embodiment, the outer shape (contour) of the front end face 6 is obtained by measurement using a laser microscope. Fig. 9 The outline data shown in the figure is used as the outer shape (outline) of the front end face 6.

[0072] Specifically, Fig. 9 The outer shape (contour) of the front end face 6 as shown is measured by a laser microscope in the direction of a straight line connecting the point A on the center side cutting edge 7 on one side and the point B on the center side cutting edge 7 on the other side when observed from the front end of the tool, and the difference in distance in the direction of the tool rotation axis a from any appropriate position is plotted as data, that is, the outer shape (contour) of the front end face 6 represents the shape obtained by capturing the front end face 6 from the lateral direction of the tool (the direction at right angles to the tool rotation axis a).

[0073] Thus, it can be confirmed that the outer shape (contour) of the front end face 6 is a mountain-shaped shape protruding from the center side cutting edge 7 side toward the tool center side (tool rotation axis a side), and the front end face 6 is a convex surface protruding toward the front end side in the direction of the tool rotation axis a.

[0074] In addition, the front end surface 6 is configured such that the center side cutting edge 7 is formed near the tool rotation axis a. Therefore, in the present embodiment, a machined surface with less grinding and excellent glossiness can be obtained in plane machining perpendicular to the tool rotation axis a.

[0075] Specifically, in this embodiment, as described above, the front end face 6 is connected to the front end flank face 4 (first flank face 4a), and, as Fig.10 As shown, when viewed from the front end of the tool, with respect to the center side cutting edge 7 or the extended line 8 of the center side cutting edge 7 passing through the tool rotation axis a, the side of the ball-end cutting edge 5 connected to the center side cutting edge 7 is set as the positive side and the opposite side is set as the negative side, the front end face 6 is provided with a contact point P2 (when viewed from the front end of the tool, the ridge line 10 on the side away from the ball-end cutting edge 5 among the ridge lines 10 formed by the front end face 6 and the front end flank face 4 and the chip row having the ball-end cutting edge 5 and the center side cutting edge 7 connected to the ball-end cutting edge 5). The front end face 6 is configured such that the center side cutting edge 7 is located near the tool rotation axis a, and the spacing X between the intersection P1 (the intersection of the center side cutting edge 7 or the extension line 8 of the center side cutting edge 7 and the perpendicular line 9 passing through the tool rotation axis a) and the intersection P2 in the direction of the center side cutting edge 7 is greater than 0% and less than 10% of the tool outer diameter, thereby, the front end face 6 is configured such that the center side cutting edge 7 is set near the tool rotation axis a.

[0076] Here, in this embodiment, Fig.10 , Fig.11 As shown, the center side cutting edge 7 is formed as a straight line at the intersection ridgeline portion of the front face 6 and the front cutting edge 3 (notch surface 12) facing the front side of the tool rotation direction. The center side cutting edge 7 can be formed as a straight line in its entire area, or can be formed as a straight line in a part. For example, it can also be formed as a straight line from the intersection point Q of the center side cutting edge 7 and the connected ball-end cutting edge 5 (the intersection of the ridgeline 10 formed by the front face 6 and the front rear cutting edge 4 (first rear cutting edge 4a) close to the ball-end cutting edge 5 and the edge of the front end of the chip discharge groove 2 having the ball-end cutting edge 5 and the center side cutting edge 7 connected to the ball-end cutting edge 5) toward the inside of the tool (the opposite direction to the ball-end cutting edge 5, that is, the negative side). The following Fig.11 (b) is an example of a method in which a portion is linear. In this case, the linear portion can be captured, the extension line 8 of the center side cutting edge 7 and the direction along the center side cutting edge 7 can be determined, and the spacing distance X can be confirmed.

[0077] in addition, Fig.11 It is a schematic diagram showing the case where the intersection point P2 exists on the positive side and the case where it exists on the negative side when viewed from the front end of the tool of this embodiment in which the center side cutting edge 7 is formed in a straight line. Fig.11 (a) Fig.11 (b) is a schematic diagram of the case where the intersection point P2 exists on the positive side. Fig.11 (c) Fig.11 (d) is a schematic diagram of a case where the intersection point P2 exists on the negative side.

[0078] Specifically, Fig.11 (a) and Fig.11 (b) is an example in which the intersection point P2 exists at the edge of the front end of the chip discharge groove 2 having the center side cutting edge 7 and exists at the edge on the positive side of the front end of the wall surface (rake face 3) facing the front side of the tool rotation direction. Fig.11 (b) is an example in which the center side cutting edge 7 is formed by a straight line portion extending from the intersection Q of the center side cutting edge 7 and the connected ball-end cutting edge 5 toward the inner side of the tool (the opposite direction to the ball-end cutting edge 5, i.e., the negative side) and a curved line portion connected to the edge of the wall surface toward the rear side of the tool rotation direction, and the intersection point P2 exists in the curved line portion.

[0079] in addition, Fig.11 (c) is an example in which the intersection point P2 exists at the edge of the front end of the chip discharge groove 2 having the center side cutting edge 7 and exists at the edge on the negative side of the front end of the same surface as the wall surface (front cutting edge 3) facing the front side of the tool rotation direction. Fig.11(d) is an example in which the intersection point P2 exists at the edge of the front end of the chip discharge flute 2 having the center side cutting edge 7 and exists at the edge of the front end of the wall surface facing the rear side in the tool rotation direction existing on the negative side.

[0080] As described above, the spacing distance X in this embodiment is one of the inventive elements (indicators) used when the intersection point P2 exists on the positive side. In order to help understand the contents of Experimental Examples 2 and 3 described later, Fig.11 (c) Fig.11 In (d), a portion corresponding to the interval distance X is described in parentheses. In this case, X takes a negative value.

[0081] In addition, the center side cutting edge 7 is not limited to a straight line, and can also be formed into a curved line. Fig.10 and Fig.11 As shown in (a), when the intersection point P2 exists on the positive side, in these figures, the center side cutting edge 7 is formed as a straight line having end points at the intersection point Q and the intersection point P2, but the center side cutting edge 7 can also be formed as a curved line that bends toward the front side of the tool rotation direction or the rear side of the tool rotation direction, and can also be formed as a wavy line. In this case, as long as the imaginary straight line connecting the intersection point Q and the intersection point P2 is regarded as the center side cutting edge 7, the extension line 8 of the center side cutting edge 7 and the direction along the center side cutting edge 7 are determined, and the spacing distance X is confirmed.

[0082] In addition, in the front end face 6 of the present embodiment, as shown in FIG. Fig.10 As shown, when observed from the front end of the tool, the opposing intervals of two ridges 10 formed by the front end face 6 and the front end back cutting faces 4 (first back cutting faces 4a) of a pair of ball-end cutting edges 5 arranged 180 degrees rotationally symmetrically relative to the tool rotation axis a are set to be the width W of the front end face 6, and the front end face 6 is constructed so that its width W is 0.005mm≦W≦0.2D (D is the outer diameter of the tool).

[0083] Specifically, as a more preferred specification, the front end face 6 of the present embodiment is configured to be larger than the tool outer diameter. In the case of , the width W is 0.01mm≦W≦0.3mm. In addition, when the tool outer diameter is In the following cases, the width W satisfies 0.01 mm≦W≦0.2D (D is the tool outer diameter).

[0084] The effects of the present embodiment configured as described above will be described below.

[0085] In this embodiment, a convex front end face 6 intersecting the tool rotation axis a of the tool body 1 is provided at the front end of the tool, so there is no chisel edge with a large negative front angle, and gnawing due to the influence of the chisel edge can be prevented as much as possible.

[0086] In addition, in this embodiment, since the intersection ridge portion of the front end face 6 and the front cutting edge 3 constitutes a center side cutting edge 7 connected to the ball end cutting edge 5, the center side cutting edge 7 has the same rake angle as the ball end cutting edge 5 and exerts the same high cutting performance as the ball end cutting edge 5.

[0087] Moreover, since the front end face 6 of the present embodiment is formed into a convex shape, during the plane processing perpendicular to the tool rotation axis a, even if the perpendicularity of the tool rotation axis a relative to the plane is offset (for example, even if the tool is bent due to cutting resistance and the tool rotation axis a is slightly inclined relative to the plane), the front end face 6 is in contact with the plane, thereby exerting the polishing effect brought about by the sliding contact of the front end face 6 with the cutting surface.

[0088] Thus, in this embodiment, in the plane processing perpendicular to or intersecting the tool rotation axis a, the generation of cutting marks caused by the center side cutting edge 7 during cutting can be suppressed by the higher cutting performance based on the center side cutting edge 7 and the polishing effect based on the sliding contact action of the front end face 6 to the cutting surface, and a processed surface with excellent gloss equal to or better than that of the case of cutting using the ball head edge 5 can be obtained.

[0089] In addition, in the present embodiment, the front end face 6 is connected to the front end flank face 4 (first flank face 4a), and when viewed from the front end of the tool, with the ball-end cutting edge 5 connected to the center side cutting edge 7 being the positive side and the opposite side being the negative side relative to the perpendicular line 9 passing through the center side cutting edge 7 or the extension line 8 of the center side cutting edge 7 of the tool rotation axis a, the front end face 6 is provided with a crossing point P2 (when viewed from the front end of the tool, the ridgeline 10 on the side away from the ball-end cutting edge 5 among the ridgelines 10 formed by the front end face 6 and the front end flank face 4 (first flank face 4a) and the ball-end cutting edge 5 and the center side cutting edge 7 connected to the ball-end cutting edge 5 are connected). The intersection of the edge of the front end of the chip discharge groove 2 of the cutting edge 7 exists on the negative side, or exists at the intersection P1 (the intersection of the center side cutting edge 7 or the extension line 8 of the center side cutting edge 7 and the perpendicular line 9 passing through the center side cutting edge 7 or the extension line 8 of the center side cutting edge 7 passing through the tool rotation axis a when viewed from the front end of the tool) and the intersection P2, and the spacing distance X in the direction of the center side cutting edge 7 is greater than 0% and less than 10% of the outer diameter of the tool. Therefore, the center side cutting edge 7 is set near the tool rotation axis a, thereby, it is possible to obtain a processed surface with less erosion in the plane processing perpendicular to or intersecting the tool rotation axis a.

[0090] In this embodiment, the width W of the front end face 6 is formed to be 0.005 mm ≤ W ≤ 0.2D (D is the tool outer diameter). In the case of the width W is 0.01mm≦W≦0.3mm, the tool outer diameter is In the following case, the width W is constituted to be 0.01mm≦W≦0.2D (D is the outer diameter of the tool), thereby being able to suppress the occurrence of gnawing and chip welding due to the increase in cutting resistance, and being able to suppress the progression of wear on the front end face 6, and being able to obtain a machined surface with excellent glossiness equal to or greater than that of the case of finishing with a ball-end cutting edge 5.

[0091] In this way, this embodiment becomes a ball end mill suitable for finishing, which can obtain a machined surface with excellent glossiness when cutting a plane perpendicular to the tool rotation axis a, such as the bottom surface of the mold at the front end of the tool, and can omit the grinding process or reduce the grinding processing time.

[0092] In this embodiment, the shape of the front end face 6 is configured as follows: Fig.12 The conical shape shown in (a) of FIG. 1 is shown in FIG. 1 , but in addition, in the structure Fig.12 A quadrangular pyramid shape as shown in (b), Fig.12 A gable roof shape consisting of two surfaces as shown in (c), and Fig.12 The above-mentioned effects can also be obtained in the case where a flat truncated cone is provided on the top of the convex surface as shown in (d).

[0093] Specifically, Fig.12 The shape (truncated cone shape) of the front end face 6 shown in (d) is configured so that Fig.12 Although not shown in the figure, an example of a truncated cone obtained by providing a flat surface on the top of a conical convex surface as shown in (a) of FIG. Fig.12 A flat truncated pyramid is provided on the top of the convex surface of the quadrangular pyramid as shown in (b).

[0094] In addition, in the actual product of this embodiment, the convex amount is small, so when observing from the front end of the tool, it is sometimes difficult to visually confirm clearly. Fig.12 Similarly, sometimes it is not possible to clearly visually confirm the vertex of the cone shape (a). Fig.12 (b)~ Fig.12 The intersecting ridge lines of the front end faces 6 as shown in the top view (seen from the front end of the tool) in (d).

[0095] Whether in Fig.12 (a)~ Fig.12 In either case of (d), the outer shape (contour) of the front end face 6 is a mountain-shaped shape protruding from the center side cutting edge 7 side toward the tool center side (tool rotation axis a side). Specifically, Fig.12 (a)~ Fig.12In (c), it becomes a triangular mountain shape. Fig.12 In (d), the shape becomes a trapezoidal mountain.

[0096] Although not shown in the figure, the shape of the front end face 6 is replaced with a curved surface that is convex toward the front end side in the direction of the tool rotation axis a, and Fig.12 The above-mentioned effects can also be obtained when the flat surface at the top of the frustum as shown in (d) is replaced with a curved surface convex toward the front end side in the direction of the tool rotation axis a.

[0097] Next, an experimental example for demonstrating the effect of this embodiment will be described.

[0098] <Experimental Example 1>

[0099] Experimental Example 1 is an example for confirming the state of the convexity of the finished surface relative to the front end face 6. Multiple samples are prepared in which the convexity of the outer shape of the front end face 6 (the maximum height of the contour shape of the front end face 6) obtained by changing any point on the two center side cutting edges 7 connected and passing through the vicinity of the tool rotation axis a is changed. Each sample is used to evaluate the glossiness of the machined surface when the workpiece is cut under the following processing conditions.

[0100] Specifically, when setting Tool Specification to Tool OD: Shank Diameter: Effective length: 30mm Case and tool outer diameter: Shank Diameter: When the effective length is 12 mm, the machining time is set to 20 minutes and the tool outer diameter is set to In the case of the tool outer diameter being set to , the glossiness of the machined surface was evaluated by visual appearance (appearance of the reflected image) when the tool tip was used to machine a plane perpendicular to the tool rotation axis a. In addition to setting the tool outer diameter to In addition to the above-mentioned visual inspection of the appearance, the surface roughness was evaluated and the processed surface was observed.

[0101] Specifically, in the visual evaluation of the appearance, a plurality of clear ○ marks are repeatedly arranged along the length direction on the back of a ruler (metal ruler), and the ruler is set on the processed surface in such a manner that the surface on which the ○ marks are repeatedly arranged is perpendicular to each processed surface, and the appearance of the ○ marks (reflected images) reflected on the processed surface is compared and evaluated.

[0102] In the evaluation of the surface roughness, the arithmetic mean roughness Ra was measured, and in the observation and evaluation of the processed surface, the processed surface was magnified to observe the cutting marks or gnawing of the processed surface.

[0103] In addition, when a plurality of samples having a desired convex amount are produced as shown in Table 1 below, The width W of the front end face 6 is appropriately set within the range of 0.01 mm to 0.100 mm, and the spacing distance X is appropriately set within the range of -0.038 mm to 0.055 mm. For the sample, the width W of the front end surface 6 is appropriately set within the range of 0.01 mm to 0.100 mm, and the spacing distance X is appropriately set within the range of -0.029 mm to 0.028 mm.

[0104] [Set tool outer diameter to Processing conditions at

[0105] Cutting material: Pre-hardened steel (30HRC)

[0106] Rotation speed: 13,000min -1

[0107] Feed speed: 1,500 mm / min

[0108] Axial cutting depth: 0.05mm

[0109] Radial cutting depth: 0.1mm

[0110] Coolant: water-soluble cutting fluid

[0111] [Set tool outer diameter to Processing conditions at

[0112] Cutting material: Pre-hardened steel (30HRC)

[0113] Rotation speed: 19,000min -1

[0114] Feed speed: 950mm / min

[0115] Axial cutting depth: 0.05mm

[0116] Radial cutting depth: 0.05mm

[0117] Coolant: water-soluble cutting fluid

[0118] [result]

[0119] Table 1 below shows the tool outer diameter and tool outer diameter The evaluation results of glossiness of each sample are shown in FIG.

[0120] In addition, regarding the evaluation results of glossiness, ◎ indicates excellent glossiness equal to or better than that of the processed surface after finishing with the ball-end cutting edge 5, ○ indicates glossiness better than that of the processed surface after finishing with the chisel edge of the existing product, and × indicates glossiness equal to that of the processed surface after finishing with the chisel edge of the existing product. In addition, the processed surface after finishing with the ball-end cutting edge 5 is a plane inclined at 45° with respect to the tool rotation axis a.

[0121] [Table 1]

[0122]

[0123] As shown in Table 1, it was confirmed that when the tool outer diameter was set to and setting the tool outer diameter to In any case, when the convex amount is 6.00 μm or less, a better gloss can be obtained than that of the processed surface after finishing using the chisel edge of the existing product. Fig.13 As shown, it was confirmed that when the convex amount was 4.00 μm or less, excellent glossiness equal to or greater than that of the processed surface after finishing with the ball-end cutting edge 5 could be obtained. Fig.13 The tool outer diameter is shown as The results of visual inspection (appearance of reflected image) when the tool outer diameter is set to The same is true for time.

[0124] In addition, the following Table 2 and Fig.14 The tool outer diameter is shown as Evaluation results of surface roughness (measurement results of arithmetic mean roughness Ra) at the time of .

[0125] [Table 2]

[0126]

[0127] As shown in Table 2, it was confirmed that the smaller the convex amount, the smaller the surface roughness (arithmetic mean roughness Ra).

[0128] in addition, Fig.15 The tool outer diameter is set to The observation results of the machined surface at the time of Fig.15 As shown in Table 2 and Table 3, in the observation of the machined surface, it was confirmed that the smaller the convexity, the smaller the cutting marks or gnawing of the machined surface, which is consistent with Table 2 and Table 3. Fig.14 The evaluation results of the surface roughness shown correspond to the results.

[0129] As described above, through Experimental Example 1, it has been confirmed that by constructing the front end face 6 so that the convexity of the outer shape of the front end face 6 (the maximum height of the contour shape of the front end face 6) is less than 6.00 μm, a machined surface with good glossiness can be obtained. Preferably, by constructing the front end face 6 so that the convexity is less than 4.00 μm, a machined surface with excellent glossiness equal to or greater than that of the machined surface after finishing with the ball-end cutting edge 5 can be obtained, wherein the outer shape of the front end face 6 is obtained by connecting arbitrary points on the two center side cutting edges 7 near the tool rotation axis a.

[0130] <Experimental Example 2>

[0131] Experimental Example 2 is an example for confirming the appropriate formation range of the front end face 6 according to the position of the center side cutting edge 7 formed by setting the front end face 6. Fig.10 As shown, when observed from the front end of the tool, by changing the spacing distance X between the intersection point P1 and the intersection point P2 in the direction of the center side cutting edge 7, a sample with a changed position of the center side cutting edge 7 is produced, and each sample is used to evaluate the glossiness of the machined surface when the workpiece is cut under the following processing conditions, wherein the intersection point P1 is the intersection of the center side cutting edge 7 or the extension line 8 of the center side cutting edge 7 and the perpendicular line 9 to the center side cutting edge 7 or the extension line 8 of the center side cutting edge 7 passing through the tool rotation axis a, and the intersection point P2 is the intersection of the ridge line 10 formed by the front end face 6 and the front end back cutting edge 4 (first back cutting edge 4a) on the side away from the ball end cutting edge 5 and the edge of the front end of the chip discharge groove 2 having the ball end cutting edge 5 and the center side cutting edge 7 connected to the ball end cutting edge 5.

[0132] Specifically, when setting Tool Specification to Tool OD: Shank Diameter: Effective length: 30mm Case and tool outer diameter: Shank Diameter: When the effective length was 12 mm, the machining time was set to 20 minutes and 60 minutes respectively, and the glossiness of the machined surface when the plane perpendicular to the tool rotation axis a was machined by the tool tip was evaluated by visual appearance.

[0133] In addition, regarding the tool specifications, the convex amount of the front end surface 6 of each sample was set to 0.30 μm based on the results of Experimental Example 1. In the case of Fig.10 In the embodiment, the opposing interval of the two ridges 10 formed by the front end face 6 and the front end flank faces 4 (first flank faces 4a) of each of the pair of ball-end cutting edges 5 is set to 0.02 mm. In the case of , the width W of the front end face 6 is set to 0.01 mm. In the manufacture of the tool, when the diameter ratio X / D (D: tool outer diameter, hereinafter referred to as "diameter ratio X / D") of the spacing distance X to the tool outer diameter = 0, that is, when the spacing distance X = 0.00, the tool outer diameter is set to In the case of W = 0.1 mm, when the tool outer diameter is set to In the case of W = 0.05 mm, in addition, when the diameter ratio X / D = -0.01, the tool outer diameter is set to In the case of W = 0.2mm, when the tool outer diameter is set to In this case, W=0.1mm.

[0134] [Set tool outer diameter to Processing conditions at

[0135] Cutting material: Pre-hardened steel (30HRC)

[0136] Rotation speed: 13,000min -1

[0137] Feed speed: 1,500 mm / min

[0138] Axial cutting depth: 0.05mm

[0139] Radial cutting depth: 0.1mm

[0140] Coolant: water-soluble cutting fluid

[0141] [Set tool outer diameter to Processing conditions at

[0142] Cutting material: Pre-hardened steel (30HRC)

[0143] Rotation speed: 19,000min -1

[0144] Feed speed: 950mm / min

[0145] Axial cutting depth: 0.05mm

[0146] Radial cutting depth: 0.05mm

[0147] Coolant: water-soluble cutting fluid

[0148] [result]

[0149] Table 3 below shows the tool outer diameter as The specifications (spacing distance X, diameter ratio X / D) of each sample and the evaluation results of glossiness are shown in Table 4 below when the tool outer diameter is set to The specifications of each sample (separation distance X, diameter ratio X / D) and the evaluation results of glossiness.

[0150] In addition, regarding the spacing distance X in the following Tables 3 and 4, a negative number is used to indicate that the intersection point P2 is on the negative side relative to the perpendicular line 9 passing through the center side cutting edge 7 or the extension line 8 of the center side cutting edge 7 of the tool rotation axis a. In addition, the spacing distance X when the intersection point P2 coincides with the intersection point P1 is indicated by 0.00.

[0151] In addition, regarding the evaluation results of glossiness, ◎ indicates excellent glossiness equal to or better than that of the processed surface after finishing with the ball-end cutting edge 5, ○ indicates glossiness better than that of the processed surface after finishing with the chisel edge of the existing product, and × indicates glossiness equal to that of the processed surface after finishing with the chisel edge of the existing product. In addition, in this experimental example, the processed surface after finishing with the ball-end cutting edge 5 is a plane inclined at 45° relative to the tool rotation axis a.

[0152] [Table 3]

[0153]

[0154] [Table 4]

[0155]

[0156]

[0157] As shown in Tables 3 and 4, when the tool outer diameter is set to and setting the tool outer diameter to In any of the cases, it was confirmed that in the specification where the diameter ratio X / D was greater than 0.1, that is, the spacing distance X was greater than 10% of the tool outer diameter, the glossiness was equal to that of the case where the chisel edge of the existing product was used for finishing, regardless of whether the processing time was 20 minutes or 60 minutes. It can be considered that this is because: since the spacing distance X was greater than 10% of the tool outer diameter, the center side cutting edge 7 with higher cutting performance was located at a position away from the tool rotation axis a. In contrast, in the area on the tool rotation axis a side, the ridgeline 10 of the front end face 6 and the front end back face 4 (first back face 4a) acted as a cutting edge with a large negative front angle, causing the processed surface to be gnawed, and even through the sliding contact of the front end face 6 to the cutting surface, a sufficient polishing effect could not be obtained.

[0158] In addition, it was confirmed that in the specification where the diameter ratio X / D was 0.1 or less, that is, the spacing distance X was 10% or less of the tool outer diameter, the glossiness of the processed surface was better than that of the surface finished by the chisel edge of the conventional product, regardless of whether the processing time was 20 minutes or 60 minutes. In particular, in the specification where the diameter ratio X / D was 0.08 or less, that is, the spacing distance X was 8% or less of the tool outer diameter, the glossiness was excellent, which was equal to or better than that of the surface finished by the ball-end cutting edge 5.

[0159] As described above, through Experimental Example 2, it was confirmed that a processed surface with excellent glossiness can be obtained by providing the front end surface 6 in a structure in which the center-side cutting edge 7 is provided in the vicinity of the tool rotation axis a.

[0160] Specifically, it was confirmed that when observed from the front end of the tool, when the ball-end cutting edge 5 side connected to the center side cutting edge 7 is set as the positive side and the opposite side is set as the negative side relative to the perpendicular line 9 passing through the center side cutting edge 7 or the extension line 8 of the center side cutting edge 7 of the tool rotation axis a, the intersection P2 exists on the negative side, or the spacing distance X between the intersection P1 and the intersection P2 along the direction of the center side cutting edge 7 is greater than 0% and less than 10% of the tool outer diameter (less than 0.1D (D: tool outer diameter)), preferably greater than 0% and less than 8% (less than 0.08D (D: tool outer diameter)) The front end face 6 is set in any manner on the positive side, and an excellent glossy processed surface can be obtained.

[0161] <Experimental Example 3>

[0162] Experimental Example 3 is an example for confirming the appropriate formation range of the front end face 6 based on the width W of the front end face 6. Fig.10 As shown, when observed from the front end of the tool, the opposing interval between the two ridges 10 formed by the front end face 6 and the front end back cutting surfaces 4 (first back cutting surfaces 4a) of a pair of ball-end cutting edges 5 is set to the width W of the front end face 6, and samples with the width W of the front end face 6 changed are prepared, and each sample is used to evaluate the glossiness of the machined surface when the cut workpiece is cut under the following processing conditions.

[0163] Specifically, when setting Tool Specification to Tool OD: Shank Diameter: Effective length: 30mm, tool outer diameter: Shank Diameter: Effective length: 12mm and tool outer diameter: Shank Diameter: In the case of an effective length of 6 mm, the machining time was set to 20 minutes and 60 minutes respectively, and the glossiness of the machined surface when a plane perpendicular to the tool rotation axis a was machined by the tool tip was evaluated by visual appearance.

[0164] In addition, regarding the tool specifications, the convex amount of the front end surface 6 of each sample was set to 0.30 μm, similar to Experimental Example 2. In addition, the spacing distance X was set to an appropriate value for each sample as shown in Tables 5 to 7 below.

[0165] [Set tool outer diameter to Processing conditions at

[0166] Cutting material: Pre-hardened steel (30HRC)

[0167] Rotation speed: 13,000min -1

[0168] Feed speed: 1,500 mm / min

[0169] Axial cutting depth: 0.05mm

[0170] Radial cutting depth: 0.1mm

[0171] Coolant: water-soluble cutting fluid

[0172] [Set tool outer diameter to Processing conditions at

[0173] Cutting material: Pre-hardened steel (30HRC)

[0174] Rotation speed: 19,000min -1

[0175] Feed speed: 950mm / min

[0176] Axial cutting depth: 0.05mm

[0177] Radial cutting depth: 0.05mm

[0178] Coolant: water-soluble cutting fluid

[0179] [Set tool outer diameter to Processing conditions at

[0180] Cutting material: Pre-hardened steel (30HRC)

[0181] Rotation speed: 20,000min -1

[0182] Feed speed: 400mm / min

[0183] Axial cutting depth: 0.015mm

[0184] Radial cutting depth: 0.03mm

[0185] Coolant: water-soluble cutting fluid

[0186] [result]

[0187] Table 5 below shows the tool outer diameter as The specifications of each sample when the tool outer diameter is set to 0.0400, the width W of the front end face 6, the diameter ratio W / D (D: tool outer diameter, hereinafter referred to as "diameter ratio W / D") of the width W of the front end face 6 to the tool outer diameter, the spacing distance X) and the gloss evaluation results are shown in Table 6 below. The specifications of each sample (width W of the front end face 6, diameter ratio W / D, spacing distance X) and the evaluation results of glossiness are shown in Table 7 below when the tool outer diameter is set to The specifications of each sample (width W of the front end face 6, diameter ratio W / D, spacing distance X) and the evaluation results of glossiness at the time of .

[0188] In addition, regarding the spacing distance X in Tables 5 to 7 below, a negative number is used to indicate that the intersection point P2 is on the negative side relative to the perpendicular line 9 passing through the center side cutting edge 7 or the extension line 8 of the center side cutting edge 7 through the tool rotation axis a. In addition, regarding the evaluation results of glossiness, ◎ indicates excellent glossiness equal to or better than that of the processed surface after finishing with the ball-end cutting edge 5, ○ indicates glossiness better than that of the processed surface after finishing with the chisel edge of the existing product, and × indicates glossiness equal to that of the processed surface after finishing with the chisel edge of the existing product. In addition, in this experimental example 4, the processed surface after finishing with the ball-end cutting edge 5 is a plane inclined 45° relative to the tool rotation axis a.

[0189] [Table 5]

[0190]

[0191]

[0192] [Table 6]

[0193]

[0194] [Table 7]

[0195]

[0196]

[0197] As shown in Tables 5 to 7, when the tool outer diameter is set to In the case of and setting the tool outer diameter to In any of the cases, it was confirmed that in the specification where the width W of the front end face 6 was 0.002 mm, regardless of whether the processing time was 20 minutes or 60 minutes, gnawing occurred and the glossiness was equivalent to that of the processed surface after finishing with the chisel edge of the existing product, but it was confirmed that in the specification where the width W of the front end face 6 was 0.005 mm, the glossiness was better than that of the processed surface after finishing with the chisel edge of the existing product. It is believed that this is because: when the width W of the front end face 6 is less than 0.005 mm, the polishing effect brought about by the sliding contact of the front end face 6 becomes smaller.

[0198] In addition, as shown in Tables 5 and 6, when the tool outer diameter is set to and setting the tool outer diameter to In the case of the present invention, it was confirmed that in the specification where the width W of the front end face 6 is 0.01 mm or more and the diameter ratio W / D is 0.2 or less (i.e., the width W of the front end face 6 is 20% or less of the tool outer diameter), the glossiness of the processed surface is better than that of the processed surface after finishing with the chisel edge of the existing product. In particular, it was confirmed that in the specification of the width W at the initial stage of processing (processing time of 20 minutes) and in the specification where the width W of the front end face 6 is 0.01 mm or more and 0.3 mm or less when the processing time is 60 minutes, the glossiness is equal to or better than that of the processed surface after finishing with the ball-end cutting edge 5.

[0199] In addition, as shown in Table 7, when the tool outer diameter is set to In the case of the above, it was confirmed that when the width W of the front end face 6 is greater than 0.01 mm and the diameter ratio W / D is less than 0.2 (i.e., the width W of the front end face 6 is less than 20% of the outer diameter of the tool, so the width W of the front end face 6 is less than 0.3 mm), the glossiness is excellent, which is equal to or greater than that of the machined surface after finishing with the ball-end cutting edge 5, regardless of whether the processing time is 20 minutes or 60 minutes.

[0200] In addition, when the tool outer diameter is set to In the case of and setting the tool outer diameter to In any of the cases, it was confirmed that in the specification where the diameter ratio W / D was greater than 0.2, that is, the width W of the front end face 6 was greater than 20% of the outer diameter of the tool, the glossiness was better than that of the machined surface after finishing with the chisel edge of the existing product at the initial stage of processing (processing time was 20 minutes), but it was confirmed that when the processing time was 60 minutes, the glossiness decreased and became the same as that of the machined surface after finishing with the chisel edge of the existing product. It is believed that this is because: since the width W of the front end face 6 became greater than 20% of the outer diameter of the tool, the cutting resistance increased, and gnawing or welding of chips was induced from the initial stage of processing, and even through the sliding contact of the front end face 6 to the cutting surface, a sufficient polishing effect could not be obtained.

[0201] As described above, Experimental Example 3 confirmed that a processed surface with excellent glossiness can be obtained by forming the front end face 6 so that the width W of the front end face 6 satisfies 0.005 mm≦W≦0.2D (D: tool outer diameter).

[0202] In addition, it is preferred that when the tool outer diameter is greater than In the case of the front end face 6, the width W of the front end face 6 is formed so as to be 0.01 mm≦W≦0.3 mm, and the tool outer diameter is In the following case, by forming the front end face 6 so that the width W of the front end face 6 satisfies 0.01 mm≦W≦0.2D (D: tool outer diameter), a processed surface with better glossiness can be obtained.

[0203] In addition, although not shown in Tables 5 to 7, it was confirmed during the implementation of the above-mentioned Experimental Example 3 that even if the width W of the front end face 6 is a specification confirmed to have an excellent glossiness equal to or greater than that of the processed surface after finishing using the above-mentioned ball-end cutting edge 5 (evaluated as ◎), when observed from the front end of the tool, by making the diameter of the circle serving as the rotation trajectory of the front end face 6 a value larger than 35% of the outer diameter of the tool, it does not necessarily become an excellent glossiness equal to or greater than that of the processed surface after finishing using the ball-end cutting edge 5 (evaluated as ◎), and there is a case where the glossiness is better than that of the processed surface after finishing using the chisel edge of the existing product (evaluated as ○).

[0204] This is presumably because: by making the diameter of the circle serving as the rotation trajectory of the front end face 6 larger than 35% of the outer diameter of the tool, the cutting resistance increases and a good cutting surface cannot be obtained. Therefore, even through the subsequent sliding contact of the front end face 6 against the cutting surface, a sufficient polishing effect to obtain a machined surface with excellent gloss cannot be obtained.

[0205] Based on the above, it is preferred that the front end face 6 is formed in such a manner that the diameter of the circle serving as the rotation trajectory of the front end face 6 is less than 35% of the outer diameter of the tool when observed from the front end of the tool, that is, the longest distance between the tool rotation axis a which is the radius of the largest circle serving as the rotation trajectory of the front end face 6 and the outer edge of the front end face 6 is less than 17.5% of the outer diameter of the tool.

[0206] <Experimental Example 4>

[0207] Experimental Example 4 is a comparative evaluation of this embodiment and an existing product (a ball-end end mill with a front end shape having a chisel edge at the front end of the tool). In this embodiment, the convex amount of the front end face 6 is set to 1.00μm, the width W of the front end face 6 is set to 0.025mm, and the spacing distance X is set to 0.005mm. The difference between this embodiment and the existing product is only that the front end face 6 or the chisel edge is provided at the front end of the tool, that is, the ball-end edge 5 and other parts are of the same specifications. The present embodiment and the existing product of this specification are used to evaluate the glossiness and surface roughness of the machined surface when the workpiece is cut under the following processing conditions.

[0208] Specifically, the tool specifications of this embodiment and the existing product are tool outer diameter: Shank Diameter: Effective length: 12 mm. The glossiness of the machined surface when a plane perpendicular to the tool rotation axis a (hereinafter referred to as the "0° plane") was machined for 20 minutes and 60 minutes using the tool tip, and the glossiness of the machined surface when a plane inclined at 45° relative to the tool rotation axis a (hereinafter referred to as the "45° plane") was machined for 20 minutes and 60 minutes using the ball-end cutting edge 5 were evaluated by visual appearance (appearance of reflected image). In addition, the surface roughness was evaluated by measuring the arithmetic mean roughness Ra.

[0209] [Processing conditions]

[0210] Cutting material: Pre-hardened steel (30HRC)

[0211] Rotation speed: 19,000min -1

[0212] Feed speed: 950mm / min

[0213] Axial cutting depth: 0.05mm

[0214] Radial cutting depth: 0.05mm

[0215] Coolant: water-soluble cutting fluid

[0216] [result]

[0217] Fig.16The results of the evaluation of the glossiness of the 0° surface of each of the present embodiment and the existing product are shown. Specifically, on the back of the ruler (metal ruler) in the upper part of the figure, a plurality of clear ○ marks are repeatedly arranged along the length direction of the ruler (metal ruler), and the surface with the repeated ○ marks is placed on each processed surface (0° surface), and the appearance of the ○ marks (reflected images) reflected on the processed surface (0° surface) is compared and evaluated. Fig.16 As shown, regarding the 0° surface, in the present embodiment, regardless of whether the processing time is 20 minutes or 60 minutes, a processed surface with excellent glossiness can be obtained, to the extent that a clear reflected image (○ mark) can be visually confirmed. In contrast, in conventional products, no reflected image (○ mark) can be confirmed, but a processed surface without gloss is obtained.

[0218] In addition, with respect to the 45° surface (the surface processed using the ball-end cutting edge 5), the processing time was set to 20 minutes and the present embodiment was compared with the existing product. The results confirmed that since the ball-end cutting edge 5 was of the same specification, no difference was found between the two. Although not shown in the figure, both were able to obtain a processed surface with excellent glossiness to the extent that a clear reflected image could be visually confirmed.

[0219] in addition, Fig.17 : is a graph showing the measurement results of the arithmetic mean roughness Ra of the 0° surface when the processing time is 20 minutes and 60 minutes for each of the present embodiment and the conventional product, Fig.18 This is a graph showing the measurement results of the arithmetic mean roughness Ra of the 0° surface and the 45° surface when the processing time is 20 minutes for each of the present example and the conventional product.

[0220] like Fig.17 As shown, it was confirmed that the value of the arithmetic mean roughness Ra of the processed surface of this example was smaller than that of the conventional product.

[0221] In addition, if Fig.18 As shown, in general, as in the conventional products, the surface roughness of the 0° surface processed by the chisel edge at the front end of the tool is greater than the surface roughness of the 45° surface processed by the ball-end edge. However, in this embodiment, Fig.18 As shown, it was confirmed that both the 45° surface and the 0° surface had good surface roughness, and that the 0° surface processed by the tool tip having the front end surface 6 had better surface roughness than the 45° surface processed by the ball-end cutting edge 5 .

[0222] As described above, according to Experimental Example 4, in this embodiment, by setting the front end face 6 in a manner that forms a structure in which the center side cutting edge 7 is set near the tool rotation axis a at the front end of the tool, even in plane processing perpendicular to the tool rotation axis a using the front end of the tool, a processed surface with a glossiness that is equal to or better than that of a processed surface using a ball-end cutting edge 5 can be obtained.

[0223] In addition, the present invention is not limited to the present embodiment, and the specific structure of each component can be designed appropriately.

Claims

1. A ball-end milling cutter, wherein a plurality of chip discharge grooves are formed on the outer periphery of a tool body, the plurality of chip discharge grooves are open at the front end and extend from the front end side of the tool toward the base end side of the tool, and a ball-end cutting edge is provided at the intersection of the rake face of the chip discharge groove and the front end flank face of the tool body, characterized in that: A convex front end surface intersecting the tool rotation axis of the tool body is provided at the tool front end portion, and an intersecting ridgeline portion between the front end surface and the rake face constitutes a center side cutting edge connected to the ball-end cutting edge.

2. The ball end mill according to claim 1, characterized in that: The front end surface is provided between the front end flank surfaces of each of the pair of ball-end cutting edges provided 180 degrees rotationally symmetrically with respect to the tool rotation axis so as to be connected to the front end flank surface and the respective rake surfaces.

3. The ball end mill according to claim 2, characterized in that: The front end face is constructed to include the tool rotation axis, and when observed from the front end of the tool, the contour obtained by connecting an arbitrary point on the center side cutting edge on one side with an arbitrary point on the center side cutting edge on the other side with a straight line is a mountain shape, wherein the center side cutting edge on one side is connected to one of the pair of ball-end cutting edges passing near the tool rotation axis, and the center side cutting edge on the other side is connected to the other of the pair of ball-end cutting edges passing near the tool rotation axis.

4. The ball end mill according to claim 3, characterized in that: The front end face is configured to include the tool rotation axis, and when observed from the front end of the tool, the outline obtained by connecting the intersection of the center side cutting edge on one side and the ridgeline on one side and the intersection of the center side cutting edge on the other side and the ridgeline on the other side with a straight line is a mountain shape, and the maximum height of the mountain shape is less than 6 μm, wherein the center side cutting edge on one side is connected to one of the pair of ball-end cutting edges, the ridgeline on one side is formed by the front end face and the front end back blade of one side, and the center side cutting edge on the other side is connected to the other of the pair of ball-end cutting edges, and the ridgeline on the other side is formed by the front end face and the front end back blade of the other side.

5. The ball end mill according to any one of claims 1 to 4, characterized in that: The center side cutting edge is disposed adjacent to the tool rotation axis.

6. The ball end mill according to any one of claims 1 to 4, characterized in that: The front end face is connected to the front end flank face, and the front end face is set in any of the following ways: when viewed from the front end of the tool, when the ball-end cutting edge side connected to the center side cutting edge is set as the positive side and the opposite side is set as the negative side relative to the perpendicular line passing through the center side cutting edge or the extension line of the center side cutting edge passing through the tool rotation axis, the intersection point P2 exists on the negative side, or exists on the positive side where the spacing distance between the intersection point P1 and the intersection point P2 in the direction along the center side cutting edge is greater than 0% and less than 10% of the tool outer diameter, wherein the intersection point P1 is the intersection of the center side cutting edge or the extension line of the center side cutting edge and the perpendicular line passing through the tool rotation axis when viewed from the front end of the tool, and the intersection point P2 is the intersection of the ridgeline on the side away from the ball-end cutting edge among the ridgelines formed by the front end face and the front end flank face when viewed from the front end of the tool and the edge of the front end of the chip discharge groove having the ball-end cutting edge and the center side cutting edge connected to the ball-end cutting edge.

7. The ball end mill according to claim 5, characterized in that: The front end face is connected to the front end flank face, and the front end face is set in any of the following ways: when viewed from the front end of the tool, when the ball-end cutting edge side connected to the center side cutting edge is set as the positive side and the opposite side is set as the negative side relative to the perpendicular line passing through the center side cutting edge or the extension line of the center side cutting edge passing through the tool rotation axis, the intersection point P2 exists on the negative side, or exists on the positive side where the spacing distance between the intersection point P1 and the intersection point P2 in the direction along the center side cutting edge is greater than 0% and less than 10% of the tool outer diameter, wherein the intersection point P1 is the intersection of the center side cutting edge or the extension line of the center side cutting edge and the perpendicular line passing through the tool rotation axis when viewed from the front end of the tool, and the intersection point P2 is the intersection of the ridgeline on the side away from the ball-end cutting edge among the ridgelines formed by the front end face and the front end flank face when viewed from the front end of the tool and the edge of the front end of the chip discharge groove having the ball-end cutting edge and the center side cutting edge connected to the ball-end cutting edge.

8. The ball end mill according to any one of claims 1 to 4, characterized in that: In the front end face, when observed from the front end of the tool, the opposing intervals of two ridges formed by the front end face and the front end back cutting surfaces of each of the pair of ball-end cutting edges arranged 180 degrees rotationally symmetrically relative to the rotation axis of the tool are set as the width W of the front end face, and the front end face is constructed so that the width W is 0.005mm≦W≦0.2D, where D is the outer diameter of the tool.

9. The ball end mill according to claim 5, characterized in that: In the front end face, when observed from the front end of the tool, the opposing intervals of two ridges formed by the front end face and the front end back cutting surfaces of each of the pair of ball-end cutting edges arranged 180 degrees rotationally symmetrically relative to the rotation axis of the tool are set as the width W of the front end face, and the front end face is constructed so that the width W is 0.005mm≦W≦0.2D, where D is the outer diameter of the tool.

10. The ball end mill according to claim 6, characterized in that: In the front end face, when observed from the front end of the tool, the opposing intervals of two ridges formed by the front end face and the front end back cutting surfaces of each of the pair of ball-end cutting edges arranged 180 degrees rotationally symmetrically relative to the rotation axis of the tool are set as the width W of the front end face, and the front end face is constructed so that the width W is 0.005mm≦W≦0.2D, where D is the outer diameter of the tool.

11. The ball end mill according to claim 7, characterized in that: In the front end face, when observed from the front end of the tool, the opposing intervals of two ridges formed by the front end face and the front end back cutting surfaces of each of the pair of ball-end cutting edges arranged 180 degrees rotationally symmetrically relative to the rotation axis of the tool are set as the width W of the front end face, and the front end face is constructed so that the width W is 0.005mm≦W≦0.2D, where D is the outer diameter of the tool.

12. The ball end mill according to claim 8, characterized in that: When the tool outer diameter is greater than φ1.5 mm, the width W of the front end surface is set to 0.01 mm≦W≦0.3 mm. When the tool outer diameter is ≦φ1.5 mm, the width W of the front end surface is set to 0.01 mm≦W≦0.2D, where D is the tool outer diameter.

13. The ball end mill according to claim 9, characterized in that: When the tool outer diameter is greater than φ1.5 mm, the width W of the front end surface is set to 0.01 mm≦W≦0.3 mm. When the tool outer diameter is ≦φ1.5 mm, the width W of the front end surface is set to 0.01 mm≦W≦0.2D, where D is the tool outer diameter.

14. The ball end mill according to claim 10, characterized in that: When the tool outer diameter is greater than φ1.5 mm, the width W of the front end surface is set to 0.01 mm≦W≦0.3 mm. When the tool outer diameter is ≦φ1.5 mm, the width W of the front end surface is set to 0.01 mm≦W≦0.2D, where D is the tool outer diameter.

15. The ball end mill according to claim 11, characterized in that: When the tool outer diameter is greater than φ1.5 mm, the width W of the front end surface is set to 0.01 mm≦W≦0.3 mm. When the tool outer diameter is ≦φ1.5 mm, the width W of the front end surface is set to 0.01 mm≦W≦0.2D, where D is the tool outer diameter.

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