End mill

Abstract

While ensuring a certain rigidity at the front end of the tool body, the chip discharge property of the chips passing through the center grooves located on the front side in the rotation direction of each of the multiple cutting edges to the chip discharge groove is made good. The end mill has, on the front end side in the direction of the rotation axis (O) of the tool body: multiple cutting edges that are continuous in the range from the center side in the radial direction to the outer peripheral side and are arranged adjacent to each other in the rotation direction (r) of the tool body; center grooves formed on the front side in the rotation direction of each cutting edge; and chip discharge grooves continuous with the center grooves. The center grooves are constituted by front side concave surfaces (8, 9) formed along a front side axis (P1) that forms an acute angle (θ1) with the rotation axis (O), and rear side concave surfaces (10, 11) formed along a rear side axis (P2) that forms a smaller acute angle (θ2) with the rotation axis (O) than the front side axis (P1), and the front side concave surfaces (8, 9) and the rear side concave surfaces (10, 11) are formed in an overlapping shape with each other.

Description

Technical Field

[0001] The present invention relates to an end mill that ensures a certain rigidity at the front end of a tool body while enabling good chip discharge from a central groove located on the front side in the rotational direction of each of a plurality of cutting edges to a chip discharge groove. Background Art

[0002] Chips cut by a cutting edge such as a bottom edge of an end mill are discharged to a chip discharge groove through a central groove continuously formed on the front side in the rotational direction of the rake face of the cutting edge. Due to the formation of this central groove, the rigidity of the front end of the end mill is liable to be reduced relative to the rigidity of the formation section of the chip discharge groove. Therefore, suppressing the reduction of the rigidity of the front end has become an issue in the manufacture of end mills.

[0003] The reduction of the rigidity of the front end can be suppressed to a certain extent by, for example, forming the central groove in two stages on the front end side and the rear side, and making the center groove surfaces of the respective central grooves have an angle such that the boundary line between the two-stage central grooves protrudes on the surface side (see Patent Documents 1 and 2). In this case, the boundary line between the central grooves protrudes, and compared with the case of being recessed, the wall thickness of the central groove forming portion of the tool body increases, and accordingly, it is easy to ensure rigidity.

[0004] However, in Patent Documents 1 and 2, the surfaces of the respective central grooves are flat (paragraph 0017 of Patent Document 1, Figure 1 ,, paragraph Figure 3 of Patent Document 2), and thus the chip accommodating capacity of each central groove itself is not high. Therefore, if chips exceeding the accommodating capacity in each central groove are generated, blockage may occur.

[0005] In response to this, if the two-stage central groove in front of the bottom edge is formed in a concave curved surface shape (see Patent Document 3), the volume of each central groove increases, and thus an improvement in the chip accommodating capacity in each central groove can be expected (paragraphs 0020 and 0040 of Patent Document 3).

[0006] Prior Art Documents

[0007] Patent Documents

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 2006-15418 (Claim 1, paragraphs 0011 to 0019, Figure 1 ,, Figure 2 ).

[0009] Patent Document 2: Japanese Patent Application Laid-Open No. 2007-296588 (Claim 1, paragraphs 0006 to 0008, Figure 1 ,, Figure 2 ).

[0010] Patent Document 3: International Publication No. 2016 / 152611 (Claims 1, paragraphs 0010 to 0047, Figures 2 to 4 ) Summary of the Invention

[0011] Problems to be Solved by the Invention

[0012] However, even if the shape of each center groove surface is set to a concave curved surface as in Patent Document 3 to increase the chip accommodation capacity in each center groove, there are still problems (possibilities) with the chip dischargeability of the center grooves in this method.

[0013] Based on the above background, the present invention focuses on the flow of chips in adjacent center grooves, and proposes an end mill that ensures a certain rigidity at the front end of the tool body and has good dischargeability of chips passing through the center grooves located on the front side in the rotation direction of each cutting edge to the chip discharge groove.

[0014] Solutions to Solve the Problems

[0015] The end mill according to the invention described in Technical Solution 1 is characterized in that the end mill has, on the front end side in the rotation axis direction of the tool body: a plurality of cutting edges that are continuous in the range from the center side in the radial direction to the outer peripheral side when observing the front end from the front end face side in the rotation axis direction, and are arranged adjacent to each other in the rotation direction of the tool body; center grooves formed on the front side in the rotation direction of each cutting edge; and a chip discharge groove that is continuous from the center groove to the rear side in the rotation axis direction,

[0016] The center groove includes: a front side concave surface formed along a front side axis that forms an acute angle with the rotation axis; and a rear side concave surface that is adjacent to the rear side in the rotation axis direction of the front side concave surface and is formed along a rear side axis that forms a smaller acute angle with the rotation axis than the front side axis,

[0017] The front side concave surface and the rear side concave surface form curved surfaces of the same shape and are in an overlapping shape with each other.

[0018] In Technical Solution 1, the "front end face" in "observing the front end from the front end face side in the rotation axis direction (axial direction)" refers to Figure 1 , Figure 4 the end face when observing the end mill body (tool body) from the front end side toward the opposite side of the shank 3 in the direction of the rotation axis O as shown. In the following description, the "rotation axis O direction" will also be simply referred to as the "axial direction", and the "front end face" will also be simply referred to as the "end face". The "front end" is the cutting edge portion 2.

[0019] The "cutting edge" of Technical Solution 1 mainly refers to the bottom edge 4 that is continuous from the center side in the radial direction to the outer peripheral side when observing the front end of the tool body from the front end face side, including the rounded edge 5 in the case of being continuous with the outer peripheral side in the radial direction of the bottom edge 4. The outer peripheral edge 6 is continuous with the outer peripheral side of the rounded edge 5. When the bottom edge 4 has a rounded edge 5, the end mill 1 becomes a rounded end mill as shown in the figure, and when there is no rounded edge 5 and the outer peripheral edge 6 is continuous with the outer peripheral side of the bottom edge 4, the end mill 1 becomes a right-angle end mill.

[0020] There are cases where the bottom edge 4 is divided as shown in the figure into a main edge where the end on the center side in the radial direction of the bottom edge 4 is relatively near the center, and a sub-edge where the end on the center side of the bottom edge 4 is located on the outer peripheral side in the radial direction relative to the end near the center of the main edge, and cases where it is not divided. In any case, the bottom edge 4 (cutting edge) is formed to be paired or point-symmetrical about the rotation axis (center in the radial direction) O. Therefore, the number (number of pieces) of the bottom edges 4 is mainly 4 pieces, but there are also cases where it is more. In the drawings, an example of a four-edge rounded end mill is shown where both the main edge (main bottom edge 41) and the sub-edge (sub-bottom edge 42) are 2 pieces, and the rounded edge 5 is continuous with the bottom edge 4. In the following description, the center O in the radial direction is also referred to as the center O and the rotation axis O. The reference numeral 4 representing the bottom edge includes the reference numeral 41 representing the main bottom edge and the reference numeral 42 representing the sub-bottom edge in the drawings.

[0021] The "center groove formed on the front side in the rotation direction of each cutting edge arranged adjacent to each other in the rotation direction of the tool body" means that the center groove is located on the front side in the rotation direction of each bottom edge 4 (cutting edge). The "chip discharge groove continuous with the center groove on the rear side in the rotation axis direction" means that the chip discharge groove 7 is continuous with the center groove on the rear side in the rotation axis direction. The "rear side in the rotation axis direction" refers to the rear side (shank 3 side) when observing the tool body along the rotation axis O direction.

[0022] The statement that "the center groove includes a front-side concave surface and a rear-side concave surface" means that the center groove has two surfaces, namely the front-side concave surfaces 8, 9 and the rear-side concave surfaces 10, 11, and includes the transition surfaces 12, 13 from the front-side concave surfaces 8, 9 to the rear-side concave surfaces 10, 11. The "transition surfaces 12, 13" Figure 7 refers to the part represented by the curve on the obtuse angle side of the intersection of the line L3 and the line L4. The "center groove formed on the front side in the rotation direction of each cutting edge" refers to the part combining the front-side concave surface 8 and the rear-side concave surface 10, and the part combining the front-side concave surface 9 and the rear-side concave surface 11. The concave surface refers to the surface of the center groove.

[0023] "The rear concave surface adjacent to the rear side of the rotation axis direction of the front-end concave surface" means that when observing the tool body from the direction of the rotation axis O, the rear concave surfaces 10 and 11 are located on the rear side of the front-end concave surfaces 8 and 9. When observing the front end of the tool body from the end face side, the front-end concave surfaces 8 and 9 are located on the center side in the radial direction, and the rear concave surfaces 10 and 11 are located on the outer peripheral side in the radial direction of the front-end concave surfaces 8 and 9 (chip discharge groove 7 side). The front-end concave surfaces 8 and 9 are the "front-end center grooves 8 and 9" in the embodiment, and the rear concave surfaces 10 and 11 are the "rear-end center grooves 10 and 11" in the embodiment. The front-end concave surfaces 8 and 9 may or may not form a part of the rake face that forms the cutting edge. The rear concave surfaces 10 and 11 form a part of the rake face that forms the cutting edge.

[0024] The cutting edge (bottom edge 4) and the outer peripheral edge 6 are formed in the range from the front end side to the rear side of the tool body, and the center groove is also formed in the range from the front end side to the rear side of the tool body. In this relationship, when observing the tool body in the axial direction, the front-end concave surfaces 8 and 9 located on the center side in the radial direction are located on the front end side of the tool body, and the rear concave surfaces 10 and 11 located on the outer peripheral side in the radial direction are located on the rear side of the tool body (handle 3 side). By forming the rear concave surfaces 10 and 11 on the chip discharge groove 7 side of the front-end concave surfaces 8 and 9, the chips located in each front-end concave surface 8 and 9 enter (transfer to) each rear concave surface 10 and 11 located on the outer peripheral side in the radial direction, and the chips located in each rear concave surface 10 and 11 are discharged to the chip discharge groove 7. The rear concave surfaces 10 and 11 communicate with the front-end concave surfaces 8 and 9 and the chip discharge groove 7.

[0025] The "acute angle" of the "front-end axis P1 that forms an acute angle with the rotation axis O" in Technical Solution 1 means the angle θ1 on the acute angle side rather than the obtuse angle side when it is assumed that the front-end axis P1 intersects the rotation axis O or when observed in an intersecting manner. The front-end axis P1 may or may not intersect the rotation axis O or its extension line (located in a twisted position). The "acute angle" of the "rear-end axis P2 that forms a smaller angle with the rotation axis O than the front-end axis P1" also means the angle θ2 on the acute angle side when it is assumed that the rear-end axis P2 intersects the rotation axis O or when observed in an intersecting manner. The rear-end axis P2 may or may not intersect the rotation axis O or its extension line (located in a twisted position). The front-end axis P1 and the rear-end axis P2 are basically straight lines.

[0026] "The front-side concave surface formed along the front-side axis" means that there is a distance between the front-side concave surfaces 8, 9 and the front-side axis P1, and the straight line that is assumed to exist on the concave surface is parallel or nearly parallel to the front-side axis P1, for example. "Concave surface" mainly refers to a concave curved surface and includes a plane. The same applies to "the rear-side concave surface formed along the rear-side axis", which means that there is a certain distance, for example, between the rear-side concave surfaces 10, 11 and the rear-side axis P2.

[0027] In the first technical solution, "the front-side concave surfaces 8, 9 and the rear-side concave surfaces 10, 11 are in an overlapping shape with each other" means that when the front-side concave surface 8 (9) and the rear-side concave surface 10 (11) are respectively extracted and overlapped, they have a shape in which the concave surfaces overlap without gaps. As long as the front-side concave surface 8 (9) and the rear-side concave surface 10 (11) have a part that overlaps without gaps when the two are overlapped, there may also be a case where one concave surface has a part (extending out) extending from the overlapping part with the other concave surface on the extension plane of the concave surface. The concave surface also includes a combination of a curved surface and a plane.

[0028] In other words, it means that the shape (curve) of the cross-section of the front-side concave surface 8 (9) on the plane orthogonal to the axis in the moving direction when the concave line (concave curve) determining the reference of the front-side concave surface 8 (9) is translated in parallel, and the shape (curve) of the cross-section of the rear-side concave surface 10 (11) on the plane orthogonal to the axis in the moving direction when the concave line (concave curve) determining the reference of the rear-side concave surface 10 (11) is translated in parallel overlap. When the concave line of one side is overlapped with the concave line of the other side, if there is an overlapping part with each other, there may also be a case where one concave line has a part (extending out) extending from the overlapping part with the concave line of the other side on the extension line of the concave line. The concave line also includes a combination of a curve and a straight line.

[0029] In other words again, it means that the front-side concave surface 8 (9) and the rear-side concave surface 10 (11) continuous with it on the outer peripheral side in the radial direction form a curved surface with the same shape. Specifically, regardless of whether there are morphological differences between the front-side concave surface 8 and the front-side concave surface 9, and between the rear-side concave surface 10 and the rear-side concave surface 11, the circumferential shape (curvature, change in curvature) of the front-side concave surface 8 and the circumferential shape (curvature, change in curvature) of the rear-side concave surface 10 have the same shape.

[0030] The statement that "the front-side concave surfaces 8 and 9 and the rear-side concave surfaces 10 and 11 have morphological differences" means that there are differences in depth, length, radial inclination, etc. between the front-side concave surface 8 and the rear-side concave surfaces 10, and between the front-side concave surface 9 and the rear-side concave surfaces 11. For example, it means that there is a difference in the depth between the front-side concave surface 8 (9) and the rear-side concave surface 10 (11), or a difference in the length in the direction of the front-side axis P1 of the front-side concave surface 8 (9) and the length in the direction of the rear-side axis P2 of the rear-side concave surface 10 (11), or there are differences in the axial inclination and circumferential inclination between the front-side concave surface 8 (9) and the rear-side concave surface 10 (11). In addition, for example, it means that the bottom edge 4 is divided into a main bottom edge 41 and a sub-bottom edge 42, and there is a difference in length between the bottom edge 4 (main bottom edge 41) formed on the rear side in the rotational direction of the front-side concave surface 8 or the rear-side concave surface 10, and the bottom edge 4 (sub-bottom edge 42) formed on the rear side in the rotational direction of the front-side concave surface 9 or the rear-side concave surface 11.

[0031] "Forming curved surfaces of the same shape" means that, taking as an example the case where it is assumed that the front-side concave surfaces 8 (9) and the rear-side concave surfaces 10 (11) constitute a part of a cylindrical surface, Figure 6 in other words, a part of either the front-side concave surface 8 (9) or the rear-side concave surface 10 (11) overlaps with a part of the other. The overlapping area is the circumferential direction and the cylindrical axis direction of the cylindrical surface. There is also a case where the concave surface on the side with a smaller area of either the front-side concave surface 8 (9) or the rear-side concave surface 10 (11) overlaps with the concave surface on the side with a larger area, and there is an area on the concave surface with a larger area that does not overlap with the concave surface on the smaller side.

[0032] For example Figure 6 in, if the trajectories when the lines (curves) L1 and L2 represented by thick solid lines are translated parallel to the front-side axis P1 and the rear-side axis P2 respectively, that is, the belt-shaped areas represented by thin solid lines, are set as either the front-side concave surface 8 (9) or the rear-side concave surface 10 (11), then the other becomes a belt-shaped area that includes this belt-shaped area. Sometimes the belt-shaped area of one side and the belt-shaped area of the other side are exactly the same.

[0033] Indicates Figure 6 in, the thin curved surface that is the trajectory when the curve L1 represented by a thick line is translated parallel to the front-side axis P1 while keeping the distance from the front-side axis P1 constant becomes a part of the side surface of a cylindrical surface, that is, a cylinder. This curved surface fictitiously represents the front-side concave surfaces 8 and 9. Indicates Figure 6 in, the thin curved surface that is the trajectory when the curve L2 represented by a thick line is translated parallel to the rear-side axis P2 while keeping the distance from the rear-side axis P2 constant becomes a part of the side surface of a cylindrical surface, that is, a cylinder. This curved surface fictitiously represents the rear-side concave surfaces 10 and 11.

[0034] Figure 6 The surface represented by a solid line with a thin line is a surface formed as the rotating body Q of the grinding tool moves parallel in a direction inclined with respect to the rotation axis O (the directions of the generatrices L3 and L4) or the like. Since this surface forms the surfaces of the front-side concave surfaces 8 and 9 and the rear-side concave surfaces 10 and 11, the surfaces of the front-side concave surfaces 8 and 9 and the rear-side concave surfaces 10 and 11 form surfaces of the same shape (Technical Solution 1). "Surfaces of the same shape" means that the surfaces of the front-side concave surfaces 8 and 9 and the rear-side concave surfaces 10 and 11 have shapes that can overlap with each other, and there are cases where one surface completely coincides with the other surface and cases where one surface forms a part of the other surface.

[0035] The line L1 is Figure 6 a line that has an axis (front-side axis) P1 and protrudes toward the rear side (the shank 3 side) of the inner side of the bottom surface of the cylindrical surface (cylinder) represented by a double-dashed line, corresponding to the "line that protrudes toward the rear side in the direction of the rotation axis of the tool body" described later (Technical Solution 5). The line L2 is a thick line that has an axis (rear-side axis) P2 and protrudes toward the rotation axis O side within the upper bottom surface of the cylindrical surface (cylinder) represented by a double-dashed line, corresponding to the "line that protrudes toward the rotation axis side" described later (Technical Solution 5). The line L2 can also be said to be a curved line that protrudes toward the rear side of the tool body.

[0036] Figure 6 The shown cylindrical surface is only an example of the surface formed by the surfaces of the front-side concave surfaces 8 and 9 and the rear-side concave surfaces 10 and 11. For the surface, there are regular surfaces and irregular surfaces, and the shape is arbitrary. The surface includes a plane. However, since the surfaces of the front-side concave surfaces 8 and 9 and the rear-side concave surfaces 10 and 11 form surfaces of the same shape (Technical Solution 1), if the surface of the front-side concave surface 8 or 9 is a part of the side surface of a cylinder, the surface of the rear-side concave surfaces 10 and 11 also becomes a part of the side surface of a cylinder of the same size.

[0037] Specifically, like this, the front-side concave surfaces 8 and 9 of Technical Solution 1 form a surface when the line L1 that protrudes toward the rear side in the direction of the rotation axis O of the tool body moves parallel along the front-side axis P1 while keeping the distance from the front-side axis P1 at an acute angle with respect to the rotation axis O constant (Technical Solution 5). The rear-side concave surfaces 10 and 11 form a surface when the line L2 that protrudes toward the rotation axis O side moves parallel along the rear-side axis P2 while keeping the distance from the rear-side axis P2 at an acute angle smaller than that of the front-side axis P1 with respect to the rotation axis O constant (Technical Solution 5).

[0038] The direction in which the curve L1 moves parallel to the front-end side axis P1 is the direction of parallel movement when the rotating body Q as the grinding tool moves in parallel. "The locus when the curve L1 moves parallel to the front-end side axis P1" is the trace drawn when the curve L1 moves in parallel. The curved surface formed by the front-end side concave surfaces 8 and 9 forms a curved surface that bulges toward the rear side of the tool body, and the surfaces of the front-end side concave surfaces 8 and 9 themselves form concave curved surfaces. The direction in which the curve L2 moves parallel to the rear-end side axis P2 is also the direction of parallel movement when the rotating body Q as the grinding tool moves in parallel. The curved surface formed by the surfaces of the rear-end side concave surfaces 10 and 11 forms a curved surface that bulges toward the rear side of the tool body or toward the rotation axis O side, and the surfaces of the front-end side concave surfaces 8 and 9 themselves form concave curved surfaces.

[0039] As Figure 7 shown, if we focus on the aspect of the curved surfaces that form each center groove when the rotating body Q as the grinding tool moves in parallel, then compared with the generatrix L3 of the curved surface (cylindrical surface) that forms the front-end side concave surfaces 8 and 9 or the acute angle θ1 formed by the front-end side axis P1 and the rotation axis O, the generatrix L4 of the curved surface that forms the rear-end side concave surfaces 10 and 11 or the acute angle θ2 formed by the rear-end side axis P2 and the rotation axis O is smaller (θ1 > θ2) (Technical Solution 1). By having the front-end side concave surfaces 8 and 9 and the rear-end side concave surfaces 10 and 11 satisfy this requirement, compared with the case where this requirement is not met, the core thickness of the front end of the tool body (end mill) with the front-end side concave surfaces 8 and 9 formed becomes relatively larger, and the rigidity of the front end of the tool body is improved. In this relationship, the moving direction (P2) when the rotating body Q forms the rear-end side concave surfaces 10 and 11 is closer to the direction of the rotation axis O than the moving direction (P1) when forming the front-end side concave surfaces 8 and 9. It should be noted that Figure 6 , Figure 7 it is shown assuming that the front-end side concave surfaces 8 and 9 and the rear-end side concave surfaces 10 and 11 form part of a cylindrical surface, but the front-end side concave surface 8 (9) and the rear-end side concave surface 10 (11) are not limited to forming part of a cylindrical surface.

[0040] If the front-end side concave surfaces 8 (9) and the rear-end side concave surfaces 10 (11) form curved surfaces of the same shape, and the curved surfaces of the front-end side concave surfaces 8 and 9 and the rear-end side concave surfaces 10 and 11 are observed in a cross-section orthogonal to the generatrices L3 and L4, then there are cases where the respective curves are the same as shown in Figure 8 of (a) and (b), and cases where one curve is part of the other curve. It should be noted that the cross-sectional shape of the front-end side concave surface 8 (9) orthogonal to the generatrix L3 and the cross-sectional shape of the rear-end side concave surface 10 (11) orthogonal to the generatrix L4 are strictly ellipses, but in Figure 8 it is shown as a circular cross-section for convenience. Figure 7Illustrate the relationship between the generatrices L3 and L4 and the tool body when the rotating body Q moves parallel while changing its angle in two stages with respect to the rotation axis O.

[0041] During the parallel movement of the rotating body Q, if it approaches the rotation axis O side, the curves (L1, L2) of the center groove cross-section become longer, and if it moves away from the rotation axis O, the curves of the center groove cross-section become shorter. Since the shorter curve becomes a part of the longer curve, there are cases similar to those where one curve L1 (L2) is a part of the other curve L2 (L1), and there are cases similar to those where one surface forms a part of the other surface. The curves L1 and L2 include straight lines.

[0042] Regarding the above-mentioned "surface represented by the thin line when the curves L1 and L2 move parallel along the axes P1 and P2 while keeping the distances from the axes P1 and P2 constant", Figure 6 For the illustrated cylindrical surface, it can also be said that it is a part of the surface formed when the generatrices L3 and L4, which are at a distance from the axes P1 and P2, rotate with the axes P1 and P2 as the reference. It should be noted that Figure 6 The illustrated cylindrical surface is an example. Therefore, the generatrices L3 and L4 that move with the axes P1 and P2 as the reference are not limited to straight lines, and sometimes they move parallel with the axes P1 and P2 as the reference, etc.

[0043] The surface formed when the curves L1 and L2 move parallel along the axes P1 and P2 is also the surface formed when the surface of the rotating body Q (rotating around the rotation axis C of the rotating body Q) that is used to grind the tool body to form the center groove on the tool body moves parallel. At this time, the direction of the parallel movement becomes the direction of the generatrices L3 and L4. Figure 7 The surface formed when the surface of the rotating body Q (rotating around the rotation axis C of the rotating body Q) that is used to grind the tool body to form the center groove on the tool body moves parallel. At this time, the direction of the parallel movement becomes the direction of the generatrices L3 and L4.

[0044] When the surface of each center groove-forming surface is the Figure 7 surface formed by the parallel movement of the rotating body Q shown, Figure 8 when observing the surfaces of the front-side concave surfaces 8 and 9 shown in (a) and the surfaces of the rear-side concave surfaces 10 and 11 shown in (b) that are continuous with them in a cross-section orthogonal to the parallel movement direction, the curves have overlapping shapes. That is, if the Figure 8 curves shown in (a) and the curves shown in (b) are overlapped, within the curves shown in (a) and the curves shown in (b), the total length of the shorter-side curve ((b)) becomes a part of the longer-side curve ((a)). Figure 8 The curves of the front-side concave surfaces 8 and 9 shown in (a) of Figure 6 correspond to the curve L1 shown in Figure 6 shown, and the curves of the rear-side concave surfaces 10 and 11 shown in (b) correspond to the curve L2 shown inFigure 6 Among them, the curved surfaces of the front-side concave surfaces 8 and 9 are represented by a cylindrical surface having a generatrix L3, and the curved surfaces of the rear-side concave surfaces 10 and 11 are represented by a cylindrical surface having a generatrix L4.

[0045] Figure 8 The curve representing the front-side concave surfaces 8 and 9 shown in (a) and the curve representing the rear-side concave surfaces 10 and 11 shown in (b) are a combination of lines that are connected to both circumferential sides of a part of an arc by curves with a curvature smaller than that of the arc and are connected to a straight line at their front ends. The center in the circumferential direction of each of the arcs shown in (a) and (b) is a line L5 passing through the deepest position of the surface of the front-side concave surfaces 8 and 9 described later and a line L6 passing through the deepest position of the surface of the rear-side concave surfaces 10 and 11 (Technical Solution 4), and the center (curvature center) of each arc becomes Figure 6 the front-side axis P1 and the rear-side axis P2 shown.

[0046] Here, if attention is paid to the above-mentioned Patent Document 3, when observing the front end of the tool body from the front end face side in the direction of the rotation axis O, it becomes a state in which most of the section in the radial direction (the length direction of the sub-bottom cutting edge) of the sub-bottom cutting edge rake face faces the chip discharge groove ( Figure 2 ). As a result, the core thickness of the part near the front end face of the tool body becomes smaller, and thus the rigidity against the vibration of the end mill front end is likely to decrease.

[0047] In response to this, in the present invention, by forming the front-side concave surfaces 8 and 9 and the rear-side concave surfaces 10 and 11 on the front side in the rotation direction of each cutting edge, the chip discharge groove 7 does not become a shape that penetrates near the center O of the front end face. As a result, compared with Patent Document 3, the volume (chip pocket) of the entire center groove becomes smaller, and thus the rigidity of the end mill 1 against vibration during cutting increases.

[0048] Moreover, in the present invention, compared with the angle θ1 of the acute angle formed by the front-side axis P1, which is the reference for the curve L1 forming the front-side concave surfaces 8 and 9, and the rotation axis O, the angle θ2 of the acute angle formed by the rear-side axis P2, which is the reference for the curve L2 forming the rear-side concave surfaces 10 and 11, and the rotation axis O is smaller (θ1 > θ2). Thus, compared with the case where the two angles θ1 and θ2 are equal (θ1 = θ2), the total volume of the two center grooves becomes smaller, and thus a decrease in rigidity can be suppressed. This means that even when the total volume is the same, the rigidity of the front end of the tool body is improved. The angle θ1 is also the angle formed by the generatrix L3 of the curved surface forming the front-side concave surfaces 8 and 9 and the rotation axis O, and the angle θ2 is also the angle formed by the generatrix L4 of the curved surface forming the rear-side concave surfaces 10 and 11 and the rotation axis O.

[0049] In addition, by forming concave curved surfaces of the same shape with the front-side concave surfaces 8 and 9 and the rear-side concave surfaces 10 and 11 (Technical Solution 1), chips that are cut by the cutting edge and enter the front-side concave surfaces 8 and 9 are easily guided to the rear-side concave surfaces 10 and 11, and the chips that enter the rear-side concave surfaces 10 and 11 are easily guided to the chip discharge groove 7. Therefore, the discharge of chips from the front-side concave surfaces 8 and 9 to the rear-side concave surfaces 10 and 11 and the discharge of chips from the rear-side concave surfaces 10 and 11 to the chip discharge groove 7 become easy.

[0050] Specifically, since the front-side concave surfaces 8 and 9 and the rear-side concave surfaces 10 and 11 are concave curved surfaces of the same shape, the magnitude of the resistance that the chips moving (flowing) in the front-side concave surfaces 8 and 9 receive from the front-side concave surfaces 8 and 9 and the magnitude of the resistance that the chips moving in the rear-side concave surfaces 10 and 11 receive from the rear-side concave surfaces 10 and 11 are equal or of the same degree. As a result, it is not easy to generate a difference in the flow of chips between the two concave surfaces. Even after the chips move from the front-side concave surfaces 8 and 9 to the rear-side concave surfaces 10 and 11, the advancing directions of the respective chips in the rear-side concave surfaces 10 and 11 are the same. Therefore, it is not easy to generate an obstruction in the travel routes between the chips. In other words, the moving distance of each chip until it is transferred to the chip discharge groove 7 is shortened, so the chip discharge performance of the entire center groove is improved.

[0051] In particular, if it is connected by a continuous curved surface within the range from the front-side concave surfaces 8 and 9 to the rear-side concave surfaces 10 and 11 (Technical Solution 2), the movement of the chips in the front-side concave surfaces 8 and 9 to the rear-side concave surfaces 10 and 11 and the subsequent discharge to the chip discharge groove 7 become further smooth. "Connected by a continuous curved surface" means that there is no protruding boundary line between the surfaces of the front-side concave surfaces 8 and 9 and the surfaces of the rear-side concave surfaces 10 and 11. If it is explained by the case of the parallel movement of the rotating body Q, the "continuous curved surface" is a curve depicted as the transfer surfaces 12 and 13 when the parallel movement of the rotating body Q at the time of forming the front-side concave surfaces 8 and 9 is transferred to the parallel movement of the rotating body Q at the time of forming the rear-side concave surfaces 10 and 11, rather than a straight line. Figure 7 The transfer surfaces 12 and 13 form a curved surface protruding toward the surface side in the longitudinal section of the tool body.

[0052] In addition, if the front-side axis P1 and the rear-side axis P2, which are the references for the curves L1 and L2 that translate in parallel, are located in the same plane (Technical Solution 3), then in the valley portions of the surfaces of the front-side concave surfaces 8 and 9 and the rear-side concave surfaces 10 and 11, the path from the center side in the radial direction of the front end portion of the tool body toward the outer peripheral side when viewed from the front end face side becomes a same straight line shape, and the moving distance of the chip is further shortened. Therefore, the discharge of the chip is promoted more rapidly and smoothly. "Located in the same plane" means that the front-side axis P1 and the rear-side axis P2 exist on one plane, and when viewed in the in-plane direction of the plane, it means that the front-side axis P1 and the rear-side axis P2 are located on the same straight line. In this case, regarding the surfaces of the respective center grooves, not limited to the valley portions, looking at any portion other than the valley portions, a same straight line shape path from the center side in the radial direction of the tool body toward the outer peripheral side is also formed.

[0053] In the case where the center groove is a simple concave curved surface such as in Patent Document 3, the chips in each center groove are discharged to the center groove side adjacent to the chip discharge groove side or the chip discharge groove side without passing through the shortest distance. When the boundary line 31 formed between the first center groove 7 (corresponding to the front-side concave surface) and the second center groove 8 (corresponding to the rear-side concave surface) of Patent Document 3 is a ridge line that protrudes more than the concave curved surfaces of the first center groove 7 and the second center groove 8 (paragraph 0038), the chips in the first center groove 7 move along the concave curved surface (concave curve) of the first center groove 7 until reaching the boundary line 31 and then enter the second center groove 8 via the boundary line 31. Therefore, it is not the shortest distance until the boundary line 31. If viewed in a cross-section passing through the rotation axis O of the tool body, the chips move along the concave curve in the first center groove 7 and then cross the boundary line 31.

[0054] In contrast, if the front-side axis P1 and the rear-side axis P2 are located in the same plane (Technical Solution 3), then regardless of whether there is a clear boundary line between the front-side concave surfaces 8 and 9 and the rear-side concave surfaces 10 and 11, the chips in the front-side concave surfaces 8 and 9 move in a straight line from the front-side concave surfaces 8 and 9 to the boundary line and enter the rear-side concave surfaces 10 and 11. Similarly, regardless of whether there is a clear boundary line between the rear-side concave surfaces 10 and 11 and the chip discharge groove 7, the chips in the rear-side concave surfaces 10 and 11 move in a straight line from the rear-side concave surfaces 10 and 11 to the boundary line and enter the chip discharge groove 7. By the chips moving in a straight line, the chips in any space move the shortest distance and transfer to the adjacent space.

[0055] At least regardless of whether there is a clear boundary line between the front-side concave surfaces 8 and 9 and the rear-side concave surfaces 10 and 11, as long as the front-side axis P1 and the rear-side axis P2 are in the same plane (Technical Solution 3), the boundary line will not become a ridge line that protrudes from the surfaces of the front-side concave surfaces 8 and 9 and the rear-side concave surfaces 10 and 11. Therefore, the chips in the front-side concave surfaces 8 and 9 will not be resisted by the boundary line when passing through the boundary line, and thus the chips can pass through the boundary line without resistance.

[0056] Moreover, when observing in the in-plane direction of the plane containing the front-side axis P1 and the rear-side axis P2, if the line L5 passing through the deepest position (near the shank 3) of the surface of the front-side concave surfaces 8 and 9 and the line L6 passing through the deepest position (near the rotation axis O) of the surface of the rear-side concave surfaces 10 and 11 are on the same straight line (Technical Solution 4), the movement of the chips in the front-side concave surfaces 8 and 9 to the rear-side concave surfaces 10 and 11 and the subsequent discharge to the chip discharge groove 7 become smoother, and the discharge efficiency of the chips is further improved. The lines L5 and L6 passing through the deepest positions of the surface of the center groove are substantially straight lines containing the lines passing through the deepest positions of the surface of the center groove.

[0057] The above end mill is manufactured as follows. For a cylindrical tool body, while rotating a grinding tool as a rotating body Q around the rotation axis C of the rotating body Q, the surface of the grinding tool is moved parallel to the front-side axis P1 to form the front-side concave surfaces 8 and 9, and in this state, while rotating the grinding tool around the rotation axis C of the rotating body Q, the surface of the grinding tool is moved parallel to the rear-side axis P2 to form the rear-side concave surfaces 10 and 11 (Technical Solution 6).

[0058] Advantages of the Invention

[0059] A front-side concave surface is formed on the center side in the radial direction on the front side in the rotation direction of the cutting edge, a rear-side concave surface is formed on the chip discharge groove side of the front-side concave surface, and the front-side concave surface and the rear-side concave surface are formed in an overlapping shape with each other. Therefore, it is easy to guide the chips cut by the cutting edge into the front-side concave surface to the rear-side concave surface, and it is easy to guide the chips that enter the rear-side concave surface to the chip discharge groove. In particular, the flow of the chips passing through the front-side concave surface is consistent with the flow of the chips passing through the rear-side concave surface, and the chips do not interfere with each other's travel routes and flow smoothly. Therefore, the chips can be quickly discharged to the chip discharge groove.

[0060] In addition, compared with the acute angle formed between the front-side axis, which is the reference for the curve of the surface forming the front-side concave surface, and the rotation axis, the acute angle formed between the rear-side axis, which is the reference for the curve of the surface forming the rear-side concave surface, and the rotation axis is smaller. Thus, even if the shape is such that the volume of the front-side concave surface becomes relatively smaller than the volume of the rear-side concave surface, retention of chips in the front-side concave surface can be suppressed. Therefore, while maintaining the rigidity of the tool tip, chip evacuation performance can be improved compared to the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 is an end view showing the front face of the end mill.

[0062] Figure 2 is a perspective view when observing the end mill shown Figure 1 in the direction of the x-x line.

[0063] Figure 3 is a perspective view when observing the end mill shown Figure 1 in the direction of the y-y line.

[0064] Figure 4 is a side view showing the entirety of the end mill of the present invention including the shank.

[0065] Figure 5 is a perspective view showing the relationship between the angle θ1 formed between the line passing through the deepest position of the surface of the front-side concave surface and the rotation axis, and the angle θ2 formed between the line passing through the deepest position of the surface of the rear-side concave surface and the rotation axis.

[0066] Figure 6 is a perspective view showing the relationship between the surface formed when the curves L1 and L2 are assumed to be translated in parallel along the axes (front-side axis and rear-side axis) P1 and P2 inclined with respect to the rotation axis O of the tool body, which is the cylindrical surface formed when the rotating body as the grinding tool is translated in parallel, and the rotation axis O.

[0067] Figure 7 is a schematic elevation view showing the relationship between the surface of the front-side concave surface and the surface of the rear-side concave surface formed by the parallel translation of the rotating body as the grinding tool.

[0068] Figure 8 (a) of Figure 7 is a cross-sectional view taken along the a-a line in Figure 7 and (b) is a cross-sectional view taken along the b-b line in DETAILED DESCRIPTION OF THE INVENTION

[0069] Figures 1 to 3This is a production example of an end mill 1 having a cutting edge portion 2 provided on the front end side in the direction of the rotation axis O of the tool body. The cutting edge portion 2 has a bottom edge 4 as multiple cutting edges that are continuous within the range from the center side in the radial direction to the outer peripheral side when observing the front end portion from the front end face side in the direction of the rotation axis O and are arranged adjacent to each other in the rotation direction r of the tool body. Chip discharge grooves 7 are formed on the front side in the rotation direction r of each cutting edge (bottom edge 4) adjacent to each other in the rotation direction r of the tool body. Hereinafter, the cutting edge will be referred to as the bottom edge 4. The center in the radial direction is also the rotation axis O.

[0070] Front side center grooves 8 and 9 as front side concave surfaces are formed on the center side in the radial direction on the front side in the rotation direction r of each bottom edge 4, and rear side center grooves 10 and 11 as rear side concave surfaces are formed on the outer peripheral side in the radial direction on the front side in the rotation direction r of each bottom edge 4. The rear side center grooves 10 and 11 are located on the chip discharge groove 7 side of the front side center grooves 8 and 9 and communicate with the front side center grooves 8 and 9 and the chip discharge groove 7. In the drawings, an example is shown in which the bottom edge 4 is divided into a main bottom edge 41 in which the end portion on the center side in the radial direction of the bottom edge 4 is relatively located near the center, and a sub-bottom edge 42 in which the end portion on the center side of the bottom edge 4 is located on the outer peripheral side in the radial direction relative to the end portion near the center of the main bottom edge 41, but there may sometimes be no difference between the main bottom edge 41 and the sub-bottom edge 42. In the following description, an example of the case where the bottom edge 4 is divided into the main bottom edge 41 and the sub-bottom edge 42 will be described.

[0071] In the drawings, an example of a small-diameter end mill with a long neck length suitable for Figure 4 machining the corner portion of a die as shown is also shown, but the end mill 1 of the present invention is not limited to Figure 4 the manner shown. Figures 1 to 3 Showing the front end portion on the cutting edge portion 2 side after removing the shank portion 3 on the opposite side in the axial direction of the cutting edge portion 2 shown Figure 4 In the drawings, an example of the case where the end mill 1 is a corner end mill having a rounded corner edge 5 continuous with both the bottom edges 41 and 42 and the outer peripheral edge 6 is particularly shown, but there is also a case where the end mill 1 is a right-angle end mill without the rounded corner edge 5.

[0072] In the illustrated example, corresponding to the bottom edge 4 being divided into the main bottom edge 41 and the sub-bottom edge 42, the front side center grooves 8 and 9 are divided into a main edge front side center groove 8 located on the front side in the rotation direction r of the main bottom edge 41 and a sub-edge front side center groove 9 located on the front side in the rotation direction r of the sub-bottom edge 42. In addition, the rear side center grooves 10 and 11 are divided into a main edge rear side center groove 10 continuous with the chip discharge groove 7 side of the main edge front side center groove 8 and a sub-edge rear side center groove 11 continuous with the chip discharge groove 7 side of the sub-edge front side center groove 9.

[0073] AsFigure 1 As shown, the main bottom edge 41 extends continuously from the center (rotation axis) O or its vicinity in the radial direction to the outer peripheral side when observing the cutting edge portion 2 from the front end face side in the direction of the rotation axis O as Figure 1 shown. The "front end face in the direction of the rotation axis O" refers to the front end face of the tool body (end mill 1). In the following description, the "direction of the rotation axis O" is also referred to as the "axial direction", and the "front end face" is also referred to as the "end face". The sub-bottom edge 42 is spaced apart from the main bottom edge 41 in the rotation direction r of the tool body and is continuous within the range from a position closer to the outer periphery than the center O side when observing the cutting edge portion 2 from the end face side in the axial direction to the outer peripheral side.

[0074] The main bottom edge 41 and the sub-bottom edge 42 are formed to be paired (point-symmetrical) with respect to the center (rotation axis) O. Since the portion on the center O side of the main bottom edge 41 is continuous to the center O or its vicinity, in the drawings, when observing the front end portion of the tool body from the end face side, the flank face 41b of the main bottom edge 41 (hereinafter, the main bottom edge flank face 41b) is continuously formed in a band shape to the main bottom edge flank face 41b located on the side separated by the center O. In this case, the main bottom edge flank faces 41b, 41b located on both sides of the center O are continuous in a state having a width in the rotation direction r, thereby ensuring a certain rigidity in the main bottom edge 41. In the illustrated example, the "main bottom edge flank face 41b" is the second face of the main bottom edge.

[0075] As Figure 1 , Figure 2 shown, the main cutting edge front end side center groove 8 is formed between the rake face 41a of the main bottom edge 41 (hereinafter, the main bottom edge rake face 41a) and the flank face 42b of the sub-bottom edge 42 (hereinafter, the sub-bottom edge flank face 42b) adjacent to the main bottom edge 41 on the front side in the rotation direction r. The main cutting edge front end side center groove 8 faces the main bottom edge rake face 41a and is continuous with the main bottom edge rake face 41a. In the illustrated example, the "sub-bottom edge flank face 42b" is the second face of the sub-bottom edge.

[0076] In the case where the rounded edge 5 is formed, as Figure 2 , Figure 3As shown, the rake face 5a of the rounded corner edge 5 is continuous with the outer peripheral side in the radial direction of the rake face 41a of the main bottom edge. The rake face 6a of the outer peripheral edge 6 is continuous with the outer peripheral side in the radial direction of the rake face 5a. The rake face 5a of the rounded corner edge 5 is also continuous with the outer peripheral side in the radial direction of the rake face 42a of the sub-bottom edge 42 described later. The rake face 6a of the outer peripheral edge 6 is continuous with the outer peripheral side in the radial direction of the rake face 5a. A flank face (second face) 6b is formed on the rear side in the rotation direction of the outer peripheral edge 6. The rake face 41a of the main bottom edge and the continuous rake face 5a constitute a continuous same face (including a plane and a curved surface) without a boundary (boundary line). The rake face 42a of the sub-bottom edge 42 and the continuous rake face 5a also constitute a continuous same face (including a plane and a curved surface) without a boundary (boundary line).

[0077] The center groove 8 on the front end side of the main edge is composed of the rake face 41a of the main bottom edge and the front end side center groove face 8a formed on the rear side in the rotation direction r of the flank face 42b of the sub-bottom edge located on the front side in the rotation direction r of the main bottom edge 41. Figures 1 to 3 Examples are shown where the front end side center groove face 8a is clearly shown or not clearly shown as a concave curved surface within the center groove 8 on the front end side of the main edge, and becomes a part of the center groove 8 on the front end side of the main edge that constitutes a concave curved surface as a whole.

[0078] As Figure 2 shown, the front end side center groove face 8a is formed across the flank face 42b of the sub-bottom edge and the third face 42c (hereinafter, the third face 42c of the sub-bottom edge) formed on the rear side in the rotation direction of the flank face 42b of the sub-bottom edge. The third face 42c of the sub-bottom edge is located on the rear side in the rotation direction of the flank face (second face) 5b of the rounded corner edge 5 continuous with the sub-bottom edge 42, and thus also serves as the third face of the rounded corner edge 5.

[0079] As Figure 1 shown, on the front side in the rotation direction of the sub-bottom edge 42 and on the front side in the rotation direction of the center groove 8 on the front end side of the main edge, a center groove 9 on the front end side of the sub-edge is formed, which communicates with the center groove 8 on the front end side of the main edge. In other words, as Figure 3 shown, the center groove 9 on the front end side of the sub-edge is basically formed between the rake face 42a of the sub-bottom edge (hereinafter, the rake face 42a of the sub-bottom edge) or the face (curved surface) on the front side in the rotation direction of the part that is continuous with the center side in the radial direction thereof and the flank face 41b of the main bottom edge adjacent to the sub-bottom edge 42 on the front side in the rotation direction r. Figure 1 、 Figure 3 shown, the center groove 9 on the front end side of the sub-edge is located at a position closer to the center O in the radial direction than the rake face 42a of the sub-bottom edge, and is adjacent to the front side in the rotation direction r of the center groove 8 on the front end side of the main edge.

[0080] The central groove 9 on the front end side of the sub-edge is located on the front side in the rotation direction r of the central groove 8 on the front end side of the main edge. As a result, a part of the chip cut by the main bottom edge 41 and entering the central groove 8 on the front end side of the main edge can enter (wind into) the central groove 9 on the front end side of the sub-edge. Therefore, the chip in the central groove 8 on the front end side of the main edge can be dispersed to the central groove 10 on the rear side of the main edge and the central groove 9 on the front end side of the sub-edge, which are adjacent to the chip discharge groove 7 side of the central groove 8 on the front end side of the main edge, as described later.

[0081] In the illustrated example, the bottom edge 4 is divided into a main bottom edge 41 and a sub-bottom edge 42. The sub-bottom edge 42 is formed at a position closer to the outer circumference than the center O in the radial direction. Correspondingly, as Figures 1 to 3 shown, between the central groove 8 on the front end side of the main edge and the central groove 9 on the front end side of the sub-edge, a boundary line 81 forming a convex ridge line is shown on the front end face side. The aforementioned "portion continuous with the center side in the radial direction of the rake face 42a of the sub-bottom edge" is the boundary line 81 between the central groove 8 on the front end side of the main edge and the central groove 9 on the front end side of the sub-edge.

[0082] The central groove 9 on the front end side of the sub-edge is composed of the rake face 42a of the sub-bottom edge or the surface (curved surface) on the front side in the rotation direction of the boundary line 81, and the front end side central groove surface 9a formed on the rear side in the rotation direction r of the flank 41b of the main bottom edge located on the front side in the rotation direction r of the sub-bottom edge 42. As Figure 3 shown, there are cases where the central groove 9 on the front end side of the sub-edge does not face the rake face 42a of the sub-bottom edge and is not directly continuous with it, and cases where it faces the rake face 42a of the sub-bottom edge and is continuous with the rake face 42a of the sub-bottom edge.

[0083] Figure 1 An example showing a case where the front end side central groove surface 9a is not clearly shown as a surface (including a plane and a curved surface) in the central groove 9 on the front end side of the sub-edge is shown. As Figure 3 shown, the front end side central groove surface 9a is formed across the flank (second surface) 41b of the main bottom edge and the third surface 41d (hereinafter, the third surface 41d of the main bottom edge) formed on the rear side in the rotation direction of the flank 41b of the main bottom edge. The third surface 41d of the main bottom edge is located on the rear side in the rotation direction of the flank 5b of the rounded edge 5 continuous with the main bottom edge 41, and thus also serves as the third surface of the rounded edge 5. In the case where the flank 41b of the main bottom edge is divided into, for example, a second surface and a third surface, the third surface 41d of the main bottom edge mentioned here becomes the fourth surface.

[0084] The center groove 9 on the front end side of the sub-edge is formed along the boundary line 41c on the sub-edge 42 side of the rear flank 41b of the main bottom edge. The longer the length of the section along the boundary line 41c, the larger the planar area of the center groove 9 on the front end side of the sub-edge, that is, the center groove 9 on the front end side of the sub-edge when observing the end face of the front end part (cutting edge part 2), and the chip accommodating capacity increases. Therefore, in terms of increasing the chip accommodating capacity, it is appropriate to form it in a longer section along the boundary line 41c, for example, at least more than half of the entire length of the boundary line 41c. In the drawings, an example is shown where the center groove 9 on the front end side of the sub-edge is formed along the entire length of the boundary line 41c, that is, the case where the entire length of the boundary line 41c is the boundary line between the rear flank 41b of the main bottom edge and the center groove 9 on the front end side of the sub-edge.

[0085] A center groove 11 on the rear side of the sub-edge is formed on the chip discharge groove 7 side of the center groove 9 on the front end side of the sub-edge. As Figure 3 shown, the center groove 11 on the rear side of the sub-edge is spatially continuous with the center groove 9 on the front end side of the sub-edge and the chip discharge groove 7, and constitutes a surface different from the center groove 9 on the front end side of the sub-edge. The center groove 11 on the rear side of the sub-edge is located on the front side in the rotational direction of the sub-bottom edge 42 and constitutes the rake face 42a of the sub-bottom edge. Similarly, a center groove 10 on the rear side of the main edge is formed on the chip discharge groove 7 side of the center groove 8 on the front end side of the main edge. As Figure 2 shown, the center groove 10 on the rear side of the main edge is spatially continuous with the center groove 8 on the front end side of the main edge and the chip discharge groove 7, and constitutes a surface different from the center groove 8 on the front end side of the main edge. The center groove 10 on the rear side of the main edge is located on the front side in the rotational direction of the main bottom edge 41 and constitutes the rake face 41a of the main bottom edge.

[0086] Basically, no clear boundary line is shown between the center groove 9 on the front end side of the sub-edge and the center groove 11 on the rear side of the sub-edge. However, in Figures 1 to 3 in order to distinguish the area of the center groove 9 on the front end side of the sub-edge and the area of the center groove 11 on the rear side of the sub-edge, a line equivalent to the boundary line is shown by a double-dot dash line for convenience. Basically, no clear boundary line is shown between the center groove 8 on the front end side of the main edge and the center groove 10 on the rear side of the main edge either. However, in the drawings, a line equivalent to the boundary line between the center groove 8 on the front end side of the main edge and the center groove 10 on the rear side of the main edge is shown by a dotted line.

[0087] It can also be said that no clear boundary line is shown between the center groove 9 on the front end side of the sub-edge and the center groove 11 on the rear side of the sub-edge, and between the center groove 8 on the front end side of the main edge and the center groove 10 on the rear side of the main edge, and they are connected by a continuous curved surface within the range from the surface of the front end side center grooves 8 and 9 to the surface of the rear side center grooves 10 and 11. This matter can also be, as Figure 7As shown, the front-side axis P1 and the rear-side axis P2 of the cylindrical surface described later, and the generatrix L3 and the generatrix L4 intersect without forming an angle. In the manner of depicting the curve shown by the double-dot chain line, the front-side axis P1 is transferred to the rear-side axis P2, and the generatrix L3 is transferred to the generatrix L4. "Continuous surface" includes a surface with a constant curvature and a surface with a continuously changing curvature. Figure 7 The curve shown by the double-dot chain line in [reference] represents the transfer surfaces 12 and 13 from the surfaces of the front-side center grooves 8 and 9 to the rear-side center grooves 10 and 11.

[0088] The rear-side center groove 11 of the sub-edge faces the front tool face 42a of the sub-bottom edge. Therefore, it is composed of the front tool face 42a of the sub-bottom edge and the rear-side center groove face 11a on the side of the chip discharge groove 7 formed in the front-side center groove 9 of the sub-edge or the front-side center groove surface 9a. Figure 1 An example is shown where the rear-side center groove face 11a is not necessarily clearly shown as a surface (including a plane and a curved surface) within the rear-side center groove 11 of the sub-edge. The rear-side center groove 10 of the main edge faces the front tool face 41a of the main bottom edge. Therefore, it is composed of the front tool face 41a of the main bottom edge and the rear-side center groove face 10a on the side of the chip discharge groove 7 formed in the front-side center groove 8 of the main edge. Figure 1 An example is shown where the rear-side center groove face 10a is not necessarily clearly shown as a surface (including a plane and a curved surface) within the rear-side center groove 10 of the main edge.

[0089] Figure 1 As shown in Figure 3 An example is shown where a part (a portion) of the sub-bottom edge 42 side of the front-side center groove 9 of the sub-edge is formed to face the front tool face 42a of the sub-bottom edge or is continuous with the front tool face 42a of the sub-bottom edge. In this example, a part of the chip that is to be discharged along the front tool face 42a of the sub-bottom edge by the cutting of the sub-bottom edge 42 can temporarily enter the front-side center groove 9 of the sub-edge. Therefore, it is easy to suppress the chip clogging caused by the chips cut by the sub-bottom edge 42 concentrating and entering the rear-side center groove 11 of the sub-edge.

[0090] In addition, in Figure 1 the example shown, as Figure 2 shown, a part of the main-bottom edge 41 side of the rear-side center groove 10 of the main edge is formed to face the front tool face 41a of the main bottom edge. In this example, a part of the chip that is to be discharged along the front tool face 41a of the main bottom edge by the cutting of the main bottom edge 41 can directly enter the rear-side center groove 10 of the main edge. Therefore, the chips cut by the main bottom edge 41 are easily dispersed to the front-side center groove 8 and the rear-side center groove 10 of the main edge. Therefore, it is easy to suppress the chip clogging caused by the chips concentrating and entering either the front-side center groove 8 or the rear-side center groove 10 of the main edge.

[0091] InFigure 1 In the embodiment, the sub-edge rear side center groove 11 is formed in such a manner that the boundary line 91 between the sub-edge rear side center groove 11 and the chip discharge groove 7 intersects the sub-edge 42 at a position closer to the periphery than the midpoint in the length direction of the sub-edge 42 when the cutting edge portion 2 is observed from the front end face side. In this case, when the cutting edge portion 2 is observed from the front end face side, the portion of the chip discharge groove 7 close to the front end face of the tool body does not extend toward the radial center O side of the cutting edge portion 2, but stays at a position close to the rounded edge 5, so that the rigidity of the front end portion of the end mill 1, i.e., the cutting edge portion 2, is improved compared to the case where the chip discharge groove 7 extends toward the center O side.

[0092] When the front end of the tool body is viewed from the front end surface side in the direction of the rotation axis O, Figure 6 , Figure 8 As shown in (a) and (b), the surfaces of the main blade front end center groove 8 and the main blade rear end center groove 10 form concave curved surfaces of the same shape. Similarly, the surfaces of the sub-blade front end center groove 9 and the sub-blade rear end center groove 11 also form concave curved surfaces of the same shape. In order to facilitate the understanding of the "same shape curved surfaces", for convenience, use Figure 6 The curved surface is explained by assuming that a cylindrical surface (cylinder) is a curved surface which is a part of the surface forming the center groove.

[0093] like Figure 6 As shown, the curved surface of the front end side center grooves 8 and 9 is a curved surface formed by the trajectory of the curve L1 protruding toward the rear side (shank 3 side) in the direction of the rotation axis O of the tool body while maintaining a constant distance from the front end side axis P1 that forms an acute angle θ1 with respect to the rotation axis O when moving parallel to the front end side axis P1. The curved surface of the rear side center grooves 10 and 11 is a curved surface formed by the trajectory of the curve L2 protruding toward the rotation axis O side while maintaining a constant distance from the rear side axis P2 that forms an acute angle θ2 with respect to the rotation axis O that is smaller than the front end side axis P1 when moving parallel to the rear side axis P2.

[0094] In addition, for simplicity, Figure 6 The figure shows a case where the curved surface forming the surface of the front-end center grooves 8, 9 and the rear-end center grooves 10, 11 is assumed (hypothetically) to be a cylindrical surface (cylindrical surface) having axes P1, P2 inclined relative to the rotation axis O, and the generatrix L3, L4 of the curved surface (cylindrical surface) is inclined relative to the rotation axis O. The axis and generatrix of the cylindrical surface forming the curved surface of the front-end center grooves 8, 9 are P1, L3, respectively, and the axis and generatrix of the cylindrical surface forming the curved surface of the rear-end center grooves 10, 11 are P2, L4, respectively. It should be noted that when the generatrix L3, L4 moves parallel to the axes P1, P2 as the center, the curved surface formed (drawn) by the generatrix L3, L4 or described by the trajectory of the generatrix L3, L4 is Figure 6 The cylindrical surface shown.

[0095] Figure 6 The front-side axis P1 and the rear-side axis P2 shown become Figure 7 the locus when the rotation axis C of the rotating body Q as the grinding tool shown moves in parallel. In Figure 6 , Figure 7 , for simplicity, it is described that the axes P1, P2 and the generatrices L3, L4 (the parallel movement direction of the rotating body Q) intersect the rotation axis O, but the axes P1, P2 and the generatrices L3, L4 do not necessarily intersect the rotation axis O. The rotating body Q is equivalent to a grinding tool assumed to grind the tool body and form a center groove.

[0096] As described above, when observing the front end of the tool body from the front end face side in the direction of the rotation axis O, the shapes of the surfaces of the center groove 8 on the front side of the main cutting edge and the center groove 10 on the rear side of the main cutting edge that are continuous in the radial direction, and the shapes of the surfaces of the center groove 9 on the front side of the sub-cutting edge and the center groove 11 on the rear side of the sub-cutting edge form the same curved surface. In this relationship, Figure 6 the cylindrical surfaces having the front-side axis P1 of the assumed front-side center grooves 8, 9 shown are the same size as the cylindrical surfaces having the rear-side axis P2 of the assumed rear-side center grooves 10, 11. The case where the surfaces of the front-side center grooves 8, 9 and the surfaces of the rear-side center grooves 10, 11 both form curved surfaces of the same shape is shown in Figure 7 the cross-sectional view taken along the line a-a of Figure 8 (a) of Figure 7 and the cross-sectional view taken along the line b-b of Figure 8 (b) of

[0097] Figure 8 (a) shows the cross-section in the direction orthogonal to the front-side axis P1 (generatrix L3) of the surfaces of the front-side center grooves 8, 9, and (b) shows the cross-section in the direction orthogonal to the rear-side axis P2 (generatrix L4) of the surfaces of the rear-side center grooves 10, 11. As shown here, the curved surface formed by the surfaces of the rear-side center grooves 10, 11 becomes a part of the curved surface formed by the surfaces of the front-side center grooves 8, 9, and the surfaces (curved surfaces) of the rear-side center grooves 10, 11 are in a shape that overlaps with the surfaces (curved surfaces) of the front-side center grooves 8, 9. In Figure 7 the cross-section along the line a-a and the cross-section along the line b-b, the cross-sectional shape of the tool body strictly speaking becomes an ellipse, but in Figure 8 , for simplicity, it is shown as a circular cross-section.

[0098] In this way, the surfaces of the front-side central grooves 8 and 9 and the surfaces of the rear-side central grooves 10 and 11 are determined according to the shape of the rotating body Q and the direction of translation, and become a shape in which the surfaces (curved surfaces) of the rear-side central grooves 10 and 11 overlap with the surfaces (curved surfaces) of the front-side central grooves 8 and 9. Other than this, the shape of the curved surface is arbitrary. The "overlapping shape" does not refer to the state of the overlapping configuration, but refers to the shape that overlaps when assuming that each surface is taken out and they are overlapped. It is not that the entire surface (curved surface) overlaps, but at least a part overlaps.

[0099] By making the surfaces (curved surfaces) of the rear-side central grooves 10 and 11 overlap with the surfaces (curved surfaces) of the front-side central grooves 8 and 9, the flow of the chips passing through the front-side central grooves 8 and 9 is consistent with the flow of the chips passing through the rear-side central grooves 10 and 11. The chips do not interfere with each other's travel routes, and each chip flows smoothly and is quickly discharged to the chip discharge groove 7. Therefore, even if it is formed to have a relatively larger core thickness of the front-side central grooves 8 and 9 than that of the rear-side central grooves 10 and 11 and a relatively smaller volume of the front-side central grooves 8 and 9 than that of the rear-side central grooves 10 and 11 for the purpose of ensuring the rigidity of the front end portion of the tool body, the retention of the chips in the front-side central grooves 8 and 9 can be suppressed, and the chip discharge performance can be improved compared to the past while maintaining the rigidity of the front end portion of the tool body.

[0100] In particular, if the front-side axis P1 and the rear-side axis P2, which are the reference for the curved surfaces forming the surfaces of the front-side central grooves 8 and 9 and the rear-side central grooves 10 and 11 as described above, are located in the same plane, the chips in the front-side central grooves 8 and 9 are discharged to the chip discharge groove 7 through the shortest distance. In addition, when observing in the in-plane direction of the plane including the front-side axis P1 and the rear-side axis P2, if Figure 8 as shown in (a) and (b) of, the line L5 passing through the deepest position of the surface of the front-side central grooves 8 and 9 and the line L6 passing through the deepest position of the surface of the rear-side central grooves 10 and 11 are located on the same straight line, then the line L5 and the line L6 become a straight line. Therefore, the chips in the front-side central grooves 8 and 9 are discharged to the chip discharge groove 7 through an even shorter distance. The line L5 and the line L6 are also the generatrixes L3 and L4 respectively, so they are basically straight lines.

[0101] The curved surfaces of the front-side central grooves 8 and 9 and the curved surfaces of the rear-side central grooves 10 and 11 are not limited to cylindrical surfaces. Therefore, the curvature of each curved surface, or Figure 8The curvature of the curve on the cross-section shown is not limited to being constant. However, for example, if the curvature is the largest at the deepest part of the center groove, the volume of the center groove increases, and thus the chip accommodating capacity increases. In addition, it is easy to determine the straight line of the line L5 that includes the deepest position of the surface passing through the front-side center grooves 8 and 9, and the straight line of the line L6 that includes the deepest position of the surface passing through the rear-side center grooves 10 and 11, and it is easy to make the line L5 and the line L6 lie on the same line. Therefore, it is easy to improve the chip dischargeability in the front-side center grooves 8 and 9 and in the rear-side center grooves 10 and 11.

[0102] As described above, Figure 6 The two cylindrical surfaces shown by the double-dashed line in the figure represent the surfaces formed by the rotation of the rotating body Q as an abrasive tool while the rotating body Q moves parallel in a state where the rotation axis C of the rotating body Q with respect to the rotation axis O of the tool body maintains a constant angle, and the tool body is drawn (slid) and cut by the surface of the rotating body Q. The locus when the rotation axis C of the rotating body Q moves parallel is Figure 7 The axes P1 and P2. When the rotating body Q moves parallel, it is assumed that the rotating body Q when the surface drawn is a cylindrical surface is a sphere, but the shape of the actual rotating body Q (abrasive tool) is arbitrary, and there are also conical shapes, shapes deformed from conical shapes, etc. Figure 6

[0103] Figure 7 The situation during the formation of the front-side center grooves 8 and 9 and the rear-side center grooves 10 and 11 is shown assuming that the surfaces forming the front-side center grooves 8 and 9 and the rear-side center grooves 10 and 11 are formed by the parallel movement of the rotating body Q (abrasive tool).

[0104] Figure 7 In Figure 7 an example in which the rotation axis C of the rotating body Q is in the direction orthogonal to the rotation axis O of the tool body is shown, but the direction (angle) of the rotation axis C with respect to the direction of the rotation axis O is arbitrary. In addition, when observing in the in-plane direction of the plane including the front-side axis P1 and the rear-side axis P2 as described above, when the straight line of the line L5 that includes the deepest position of the surface passing through the front-side center grooves 8 and 9 and the straight line of the line L6 that includes the deepest position of the surface passing through the rear-side center grooves 10 and 11 lie on the same line, the axis P1 and the axis P2, or the generatrix L3 and the generatrix L4 in

[0105] lie in the same plane, but this is not necessarily the case, and there are also cases where they lie in different planes. As Figure 7As shown, the direction of the parallel movement of the rotation axis C when the rotating body Q forms the front-side center grooves 8 and 9 is different from the direction of the parallel movement of the rotation axis C when forming the rear-side center grooves 10 and 11. The angle formed by the direction of the parallel movement when forming the rear-side center grooves 10 and 11 and the rotation axis O is smaller. This is because the angle is gradually changed to guide the chips in the front-side center grooves 8 and 9 into the chip discharge groove 7.

[0106] When the rotating body Q forms the front-side center grooves 8 and 9, the direction of the parallel movement of the rotation axis C is Figure 6 the direction of the axis P1 of the cylindrical surface shown. When the rotating body Q forms the rear-side center grooves 10 and 11, the direction of the parallel movement of the rotation axis C is Figure 6 the direction of the axis P2 of the cylindrical surface shown. The acute angle formed by the direction of the parallel movement when the rotating body Q forms the front-side center grooves 8 and 9 and the rotation axis O is as Figure 5 、 Figure 7 shown as θ1, and the acute angle formed by the direction of the parallel movement when forming the rear-side center grooves 10 and 11 and the rotation axis O is θ2. For reference, if the angle formed by the straight line L7 including the deepest position of the surface passing through the chip discharge groove 7 and the rotation axis O is set as θ3 as Figure 7 shown, then θ3 < θ2. After sorting, the relationship of the angles becomes θ3 < θ2 < θ1. Figure 2 、 Figure 3 shown, then θ3 < θ2. After sorting, the relationship of the angles becomes θ3 < θ2 < θ1.

[0107] Explanation of reference numerals:

[0108] 1... End mill (tool body),

[0109] 2... Cutting edge part, 3... Shank part,

[0110] 41... Main bottom edge, 41a... Front cutting surface of the main bottom edge, 41b... Rear cutting surface (second surface) of the main bottom edge, 41c... Boundary line of the rear cutting surface 41b of the main bottom edge 41 on the side of the sub-bottom edge 42, 41d... Third surface of the main bottom edge,

[0111] 42... Sub-bottom edge, 42a... Front cutting surface of the sub-bottom edge, 42b... Rear cutting surface (second surface) of the sub-bottom edge, 42c... Third surface of the sub-bottom edge,

[0112] 5... Fillet edge, 5a... Front cutting surface of the fillet edge, 5b... Rear cutting surface of the fillet edge,

[0113] 6... Outer peripheral edge, 6a... Front cutting surface of the outer peripheral edge, 6b... Rear cutting surface of the outer peripheral edge,

[0114] 7... Chip discharge groove, 71... Boundary line on the side of the cutting edge part 2 of the chip discharge groove 7,

[0115] 8... Center groove on the front end side of the main cutting edge (concave surface on the front end side of the main cutting edge), 8a... Center groove surface on the front end side, 81... Boundary line of the center groove 8 on the front end side of the main cutting edge near the center groove 9 on the front end side of the sub-cutting edge (between the center groove 8 on the front end side of the main cutting edge and the center groove 9 on the front end side of the sub-cutting edge).

[0116] 9... Center groove on the front end side of the sub-cutting edge (concave surface on the front end side of the sub-cutting edge), 9a... Center groove surface on the front end side, 91... Boundary line between the center groove 11 on the rear side of the sub-cutting edge and the chip discharge groove 7 when observing the cutting edge portion 2 from the front end face side.

[0117] 10... Center groove on the rear end side of the main cutting edge (concave surface on the rear end side of the main cutting edge), 10a... Center groove surface on the rear end side.

[0118] 11... Center groove on the rear end side of the sub-cutting edge (concave surface on the rear end side of the sub-cutting edge), 11a... Center groove surface on the rear end side.

[0119] 12... Transfer surface from the concave surface on the front end side of the main cutting edge (center groove on the front end side of the main cutting edge) 8 to the concave surface on the rear end side of the main cutting edge (center groove on the rear end side of the main cutting edge) 10.

[0120] 13... Transfer surface from the concave surface on the front end side of the sub-cutting edge (center groove on the front end side of the sub-cutting edge) 9 to the concave surface on the rear end side of the sub-cutting edge (center groove on the rear end side of the sub-cutting edge) 11.

[0121] P1... Axis (front end side axis) of the curved surface (cylindrical surface) of the assumed center grooves 8 and 9 on the front end side, L1... Curve protruding rearward in the direction of the rotation axis O, L3... Generatrix of the curved surface (cylindrical surface) of the assumed center grooves 8 and 9 on the front end side.

[0122] P2... Axis (rear end side axis) of the curved surface (cylindrical surface) of the assumed center grooves 10 and 11 on the rear end side, L2... Curve protruding toward the rotation axis O side, L4... Generatrix of the curved surface (cylindrical surface) of the assumed center grooves 10 and 11 on the rear end side.

[0123] Q... Rotating body, C... Rotation axis of the rotating body.

[0124] L5... Line passing through the deepest position of the surface of the center grooves 8 and 9 on the front end side.

[0125] L6... Line passing through the deepest position of the surface of the center grooves 10 and 11 on the rear end side.

[0126] L7... Straight line including the line passing through the deepest position of the surface of the chip discharge groove 7.

Claims

1. A end mill, characterized in that on the front end side in the rotation axis direction of the tool body of the end mill, there are provided: a plurality of cutting edges that are continuous in the range from the center side in the radial direction to the outer peripheral side when observing the front end portion from the front end face side in the rotation axis direction, and are arranged adjacent to each other in the rotation direction of the tool body; a center groove formed on the front side in the rotation direction of each of the cutting edges; and a chip discharge groove that is continuous from the center groove to the rear side in the rotation axis direction, the center groove includes: a front end side concave surface formed along a front end side axis that forms an acute angle with the rotation axis; and a rear side concave surface that is adjacent to the rear side in the rotation axis direction of the front end side concave surface and is formed along a rear side axis that forms a smaller acute angle with the rotation axis compared to the front end side axis, the front end side concave surface and the rear side concave surface form curved surfaces of the same shape and are in an overlapping shape with each other.

2. The end mill according to claim 1, characterized in that the front end side concave surface and the rear side concave surface are connected by a continuous curved surface.

3. The end mill according to claim 1, characterized in that the front end side axis and the rear side axis are located in the same plane.

4. The end mill according to claim 3, characterized in that when observing in the in-plane direction of the plane including the front end side axis and the rear side axis, the line passing through the deepest position of the surface of the front end side concave surface and the line passing through the deepest position of the surface of the rear side concave surface are located on the same straight line.

5. The end mill according to claim 1, characterized in that the front end side concave surface is formed as a curved surface when a curve protruding toward the rear side in the rotation axis direction of the tool body moves parallel to the front end side axis while keeping the distance from the front end side axis at an angle that forms an acute angle with the rotation axis constant, the rear side concave surface is formed as a curved surface when a curve protruding toward the rotation axis side moves parallel to the rear side axis while keeping the distance from the rear side axis at an angle that forms a smaller acute angle with the rotation axis compared to the front end side axis constant.

6. A method for manufacturing an end mill, which is used to manufacture the end mill according to any one of claims 1 to 5, characterized in that in the method for manufacturing the end mill, for a cylindrical tool body, while rotating a grinding tool as a rotating body around the rotation axis of the rotating body, the surface of the grinding tool is moved parallel to the front end side axis to form the front end side concave surface, and in this state, while rotating the grinding tool around the rotation axis of the rotating body, the surface of the grinding tool is moved parallel to the rear side axis to form the rear side concave surface, thereby manufacturing the end mill according to any one of claims 1 to 5.

Images