Double-sided indexable insert with plunge milling capacity and milling cutter with cutting insert

Abstract

Double-sided indexable insert (10) for a milling cutter, comprising: a first surface (12), a second surface (14) opposite the first surface, a first pair of opposed side surfaces (16, 18) and a second pair of opposed side surfaces (20, 22), the first surface (12) having a seating surface (78) defining a plane (90); a main cutting edge (24, 26, 28, 30) defined on an intersection curve between each first and second surface (12, 14) and each first pair of opposed side surfaces (16, 18) for a total of four main cutting edges; a minor cutting edge (58, 60, 62, 64) defined at an intersection curve between each first and second surface (12, 14) and a first planar facet surface (48, 54) of each second pair of opposing side surfaces (20, 22) for a total of four minor cutting edges; and a plunge cutting edge (66, 68, 70, 72) defined at the intersection curve between each first and second surface (12, 14) and a second planar facet surface (50, 56) of each second pair of opposing side surfaces (20, 22) for a total of four plunge cutting edges; wherein the minor cutting edges (58, 60, 62, 64) are formed at a positive angle (82) with respect to a plane (84) parallel to a central longitudinal axis (11) of the indexable cutting insert (10); and wherein each second pair of opposing side surfaces (20, 22) comprises the first planar facet surface (48, 54) and the second planar facet surface (50, 56), the second planar facet surface (50, 56) extending radially inwardly with respect to the first planar facet surface (48, 54).

Description

BACKGROUND OF THE INVENTIONThe invention relates to a cutting insert for a cutting operation, and more particularly to a double-sided indexable cutting insert capable of performing milling and plunge milling operations.Cutters for performing manufacturing work on metal workpieces are well known in the art. Such cutters typically comprise a cylindrical or plate-shaped body which is removably connectable to a rotating drive shaft. Cutting inserts are mounted around the outer periphery of the cutter body to produce a series of metal cutting cuts on a workpiece.DE 10 2011 088 318 A1 discloses a double-sided indexable insert which is embodied as rectangular in a plan view, wherein, in a side view, diagonally opposite corners of one pair are arranged higher than the diagonally opposite corners of another pair. The short side surfaces are provided with a concave recess.EP 1 960 141 B1 discloses a milling tool with a cutting insert which is designed as a positive cutting tip with a plunge milling edge. It is also mentioned that the cutting tip can be designed as a negative indexable cutting tip in that cutting edges can also be formed at the intersection of the bearing surface and the flank.Furthermore, cutting inserts for milling cutters are shown in DE 691 11 688 T2, U.S. Pat. No. 6,196,770 B1, U.S. Pat. No. 5,078,550 A, WO 2011 086 544 A1, U.S. Pat. No. 2005 0 169 716 A1 and WO 2012 / 020 784 A1.Conventional indexable milling cutter inserts with plunge milling capacity can only perform plunge milling operations at a very low or shallow angle. As a result, conventional indexable milling cutter inserts with plunge milling capacity perform the plunge milling operations only very poorly.Accordingly, there is a need for an improved cutting insert that can adequately perform both milling and plunge milling operations.SUMMARY OF THE INVENTIONThe object is achieved by a double-sided indexable cutting insert according to claim 1 and by a milling cutter according to claim 9.The inventors of the invention have thereby solved the problem of a cutting insert which cannot adequately perform milling and plunge milling operations by providing a milling cutter having a lower seating surface formed at a positive angle with respect to a central axis of rotation of the milling cutter and by providing a clearance between the seating surface and the cutting edges of the cutting insert.In one aspect, a double-sided indexable cutting insert (hereinafter abbreviated as a cutting insert) for a milling cutter therefore includes a first surface, a second surface opposite the first surface, a first pair of opposing side surfaces, and a second pair of opposing side surfaces, the first surface having a seating surface defining a plane. A major cutting edge is defined at an intersection between each first and second surfaces and the first pair of opposing side surfaces for a total of four major cutting edges. A minor cutting edge is defined at an intersection between the first and second surfaces and a first planar facet surface of each second pair of opposing side surfaces for a total of four minor cutting edges, the minor cutting edges being formed at a positive angle with respect to a plane parallel to a central longitudinal axis of the indexable cutting insert.In another aspect, a bur includes a shank and an upper portion having an insert seat. The plate seat has a lower seating surface, a radial seating surface, and an axial seating surface. A cutting insert is disposed in the insert seat. The cutting insert has a first surface having a seating surface defining a plane, a second surface opposite the first surface, a first pair of opposing side surfaces, and a second pair of opposing side surfaces. The cutting insert further includes a major cutting edge defined on an intersection between each first and second surfaces and each first pair of opposing side surfaces for a total of four major cutting edges. A minor cutting edge is defined at an intersection between each first and each second surface and a first planar facet surface of each second pair of opposing side surfaces for a total of four minor cutting edges, the minor cutting edges being formed at a positive angle with respect to a plane parallel to a central longitudinal axis of the indexable insert. The lower seat surface of the plate seat is formed at a positive angle with respect to a central axis of rotation of the milling cutter.BRIEF DESCRIPTION OF THE DRAWINGSWhile various embodiments of the invention are illustrated, the specific embodiments shown are not intended to limit the claims in any way. It is to be understood that various changes and modifications may be made without departing from the scope of the invention. FIG. 1 is an isometric view of a cutting insert such as a milling insert according to an embodiment of the invention; FIG. 2 is another isometric view of the cutting insert of FIG. 1 rotated 90 degrees about the Y-axis; FIG. 3 is a side view of the cutting insert of FIG. 1 ; FIG. 4 is a front view of the cutting insert of FIG. 1 (the rear view is identical to the front view); FIG. 5 is a plan view of the cutting insert of FIG. 1 ; FIG. 6 is an isometric view of a milling cutter according to an embodiment of the invention, wherein the cutting inserts are not disposed in the insert seats for clarity; FIG. 7 is another isometric view of the milling cutter of FIG. 6 with the cutting inserts disposed in the insert seats; FIG. 8 is a side view of the milling cutter of FIG. 6 without the cutting inserts disposed in the insert seats for clarity; and FIG. 9 is a side view of the milling cutter of FIG. 6 with the cutting inserts disposed in the insert seats.DETAILED DESCRIPTION OF THE INVENTIONReferring now to the drawings, wherein like reference numerals refer to like elements, FIGS. 1-5 show a cutting insert 10 generally having a first surface 12, a second surface 14 opposite the first surface 12, and side surfaces 16, 18, 20, 22 that serve as seating surfaces when the cutting insert 10 is disposed in a cutting tool such as a milling cutter described below. It should be noted that the cutting insert 10 is a double-sided insert in which the first surface 12 is substantially identical to the second surface 14. Therefore, for brevity, only the first surface 12 will be described below. As is known in the art, the first surface 12 may be the top surface and the second surface may be the bottom surface when disposed in a tool holder (not shown), and vice versa. The cutting insert 10 has a central longitudinal axis 11 (Z axis), a second axis 13 (Y axis) that is perpendicular to the central longitudinal axis 11, and a third axis 15 (X axis) that is perpendicular to both the central longitudinal axis 11 and the second axis 13.The cutting insert 10 has a first major cutting edge 24 on the cutting curve between the side surface 16 and the first surface 12 and a second major cutting edge 26 on the cutting curve between the side surface 18 and the first surface 12. Similarly, the cutting insert 10 has a third major cutting edge 28 on the cutting curve between the side surface 16 and the second surface 14 and a fourth major cutting edge 30 on the cutting curve between the side surface 18 and the second surface 14.A corner radius 32, 34 connects the side surfaces 16, 18 and the side surfaces 20, 22. a point of contact 36 describes the transition between the substantially planar side surface 16 and the curved corner radius 32, and a point of contact 38 describes the transition between the substantially planar side surface 16 and the curved corner radius 34.The side surface 20 includes a planar (for better distinguishability: "first") facet surface 48 extending radially inward starting at the corner radius 32, and a planar (for better distinguishability: "second") facet surface 50 extending radially inward starting at the planar facet surface 48 to a planar seating surface 52. Similarly, a planar facet surface 54 extends radially inward from the corner radius 40 and a planar facet surface 56 extends inward from the planar facet surface 54 toward the planar seating surface 52.It will be appreciated that the cutting insert 10 is mirror symmetrical about the X axis. Although not shown in FIGS. 1-5, it will be understood that the side surface 22 of the cutting insert 10 has a planar facet surface extending radially inward from the corner radius 34 and a planar facet surface extending radially inward from the planar facet surface to a planar seating surface. Similarly, a planar facet surface extends radially inward from the corner radius 42 and a planar facet surface extends radially inward from the planar facet surface toward the planar seating surface.The cutting insert 10 has a mirror cutting edge 58 at the intersection between the planar facet surface 48 and the second surface 12 and a mirror cutting edge 60 at the intersection between the planar facet surface 54 and the first surface 12. Therefore, the double-sided cutting insert 10 has a total of four minor cutting edges 58, 60, 62, 64.In one aspect of the invention, the cutting insert 10 also has a plunge milling cutting edge 66 on the intersection between the planar facet surface 50 and the second surface 14 and a plunge milling cutting edge 68 on the intersection between the planar facet surface 56 and the first surface 12. Thus, the double-sided cutting insert 10 has a total of four dip milling cutting edges 66, 68, 70, 72 extending radially inward with respect to the mirror cutting edges 58, 60, 62, 64. The plunge milling cutting edges enable the cutting insert 10 of the invention to adequately perform two different types of cutting operations, namely, plunge milling and milling operations.The first surface 12 has a comb surface 74 extending inward from the major cutting edge 24, with a comb surface 76 extending inward from the major cutting edge 26, and a planar seating surface 78 between the comb surfaces 74, 76. Since the cutting insert 10 is mirror symmetric on the X axis, it will be appreciated that the second surface 14 of the cutting insert 10 has two comb surfaces and a planar seating surface. A counterbore 80 extends completely through the cutting insert 10 from the planar seating surface 78 on the first surface 12 to the planar seating surface on the second surface 14. The countersunk head bore 80 is centrally located in the planar seating surface 78 and the axis 11 which is parallel to the Z axis and passes through the center of the countersunk head bore 80, and the axes 13, 15 intersect the axis 11 at the center of the countersunk head bore 80 as shown in FIG. 4. Thus, all three X, Y and Z axes intersect at the center of the countersunk head bore 80.Another aspect of the invention is that the minor cutting edges 58, 60, 62, and 64 of the cutting insert 10 are formed at a positive clearance angle 82 with respect to a plane 84 that is substantially parallel to the axis 11 (parallel to the Z axis), as shown in FIG. 3. This aspect of the invention enables the cutting insert 10, when disposed in the milling cutter 100 at an angle 118, to have a sufficient clearance 120 between the surface 48 and the workpiece 130. In addition, the major cutting edges 24, 26, 28, and 30 are formed at a positive angle 86 with respect to the axis 13 (parallel to the Y axis), as shown in FIG. 3.Another aspect of the invention is that a distance 88 between a plane 90 defined by the seating surface 78 and the contact point 36 is greater than a distance 92 between the plane 90 and the contact point 44, as shown in FIG. 5. By this aspect of the invention, when positioned in the cutting device 100 at the angle 118, the cutting insert 10 has sufficient clearance 120 between the surface 54 and the workpiece 130 when the dip milling is performed using the cutting edge 66. Since the cutting insert 10 is mirror symmetrical to the axis 15 (parallel to the X axis), it will be appreciated that the distance between the plane defined by the seating surface of the second surface 14 and the point of contact describing the corner radius 32 from the second surface 14 is greater than the distance between the plane and the point of contact describing the corner radius 42 from the second surface 14.Referring to Figs. 6 to 9, there is shown a milling cutter 100 capable of receiving a cutting insert 10 of the invention. Generally, the bur 100 includes a shank 102, an upper portion 104, and a transition surface 106 between the shank 102 and the upper portion 104. The cutting apparatus 100 is preferably made of heat treated steel, such as H13 tool steel or other materials known to those skilled in the art. The specific material used will vary depending on the desired design characteristics of the cutting apparatus 100. The cutting device 100 is rotated about a central axis 108. The cutting apparatus 100 further includes a disk seat, generally shown at 110, formed on the leading edge of the upper portion 104 of the cutting apparatus 100. As shown in FIG. 6, the plate seat 110 includes a lower seating surface 112, a radial seating surface 116, and an axial seating surface 114. Therefore, the cutting insert 10 is disposed in the insert seat 110 with three contact points.In the illustrated embodiment, the milling cutter 100 may receive five cutting inserts 10 in the respective insert seat 110. However, it will be appreciated that the milling cutter 100 is not limited by the number of indexable cutting inserts 10 that may be disposed in the insert seats 110, and that the invention may be practiced with any desired number of cutting inserts and is limited only by the physical constraints on the material properties of the milling cutter.In one aspect of the invention, the lower seating surface 112 of the plate seat 110 is formed at a positive angle 118 with respect to the central axis of rotation 108 of the milling cutter 100, as shown in FIG. 8. The angle 118 is greater than 0 degrees and is at most 10 degrees. It should be noted that the angle 118 is less than the angle 86 between the major cutting edges 24, 26, 28, and 30 and the axis 13 (parallel to the Y axis). The angle 118 of the lower seating surface 112 causes the portion of the cutting insert 10 to engage the workpiece 130 to tilt rearward (toward the central axis 108), whereby the cutting insert 10 can perform dip milling operations at a more aggressive angle than that of conventional inserts.Additionally, a clearance 120 is provided between the minor cutting edges 58, 60, 62, and 64 and the seating surface 52 of the cutting insert 10, as shown in FIG. 9. This clearance 120 also allows the cutting insert 10 to perform dip milling operations at a more aggressive angle than conventional inserts.As described above, the cutting insert 10 of the invention has various aspects by which the cutting insert 10 can perform both milling and plunge milling operations with excellent performance as compared to conventional inserts. One aspect is that the cutting insert 10 has a plurality of plunge milling cutting edges at the intersection between the planar facet surface and the first and second surfaces. Another aspect of the invention is that the minor cutting edges 58, 60, 62, and 64 of the cutting insert 10 are formed at a positive clearance angle 82 with respect to the plane 84 which is substantially parallel to the axis 11 (parallel to the Z axis). Another aspect of the invention is that the distance 88 between the plane 90 defined by the seating surface 78 and the contact point 36 is greater than the distance 92 between the plane 88 and the contact point 44. In yet another aspect of the invention, the clearance 120 is formed between the minor cutting edges 58, 60, 62, and 64 and the seating surface 52 of the cutting apparatus 10. Together, these aspects of the invention enable the cutting insert and milling cutter to provide excellent cutting performance in both milling and dip milling operations.The patents and other documents cited herein are hereby incorporated by reference in their entirety. Other embodiments of the invention will be apparent to one skilled in the art upon consideration of the specification or practice of the invention disclosed herein. The specification and examples are merely illustrative and are not intended to limit the scope of the invention in any way. The true scope and spirit of the invention are set forth in the following claims.

Claims

A double-sided indexable cutting insert (10) for a milling cutter comprising: a first surface (12), a second surface (14) opposite the first surface, a first pair of opposing side surfaces (16, 18), and a second pair of opposing side surfaces (20, 22), the first surface (12) having a seating surface (78) defining a plane (90); a major cutting edge (24, 26, 28, 30) defined at an intersection between each first and each second surface (12, 14) and each first pair of opposing side surfaces (16, 18) for a total of four major cutting edges; a minor cutting edge (58, 60, 62, 64) defined at an intersection between each first and second surface (12, 14) and a first planar facet surface (48, 54) of each second pair of opposing side surfaces (20, 22) for a total of four minor cutting edges; and a dip milling cutting edge (66, 68, 70, 72) defined at the intersection between each first and second surfaces (12, 14) and a second planar facet surface (50, 56) of each second pair of opposing side surfaces (20, 22) for a total of four dip milling cutting edges; wherein the minor cutting edges (58, 60, 62, 64) are formed at a positive angle (82) with respect to a plane (84) that is parallel to a central longitudinal axis (11) of the indexable cutting insert (10); and wherein each second pair of opposing side surfaces (20, 22) has the first planar facet surface (48, 54) and the second planar facet surface (50, 56), the second planar facet surface (50, 56) extending radially inward with respect to the first planar facet surface (48, 54).The indexable cutting insert of claim 1, wherein the indexable cutting insert (10) is capable of performing both milling and plunge milling operations.The indexable cutting insert of claim 1 or 2, wherein the indexable cutting insert (10) has a corner radius (32, 34, 40, 42) connecting each first pair of opposing side surfaces (16, 18) to each second pair of opposing side surfaces (20, 22) and a contact point (36, 38, 44, 46) defining (16, 18) the corner radius of each first pair of opposing side surfaces.The indexable cutting insert of claim 3, wherein a distance (88) between the plane (90) of the seating surface (78) and the point of contact (36) of one of the opposing pairs of side surfaces is greater than the distance (92) between the plane (90) of the seating surface (78) and the point of contact (44) of the other pair of opposing side surfaces.Indexable cutting insert according to one of the preceding claims, wherein the main cutting edges (24, 26, 28, 30) are formed at a positive angle (86) with respect to an axis (13) which runs perpendicular to a central longitudinal axis of the indexable cutting insert (10).The indexable cutting insert of any preceding claim, further comprising a planar seating surface formed on the second pair of opposing side surfaces (20, 22).The indexable cutting insert of any preceding claim, further comprising a comb surface (74, 76) extending downwardly with respect to the major cutting edge.The indexable cutting insert of any preceding claim, further comprising a countersunk head bore (80) extending entirely through the indexable cutting insert (10) from the first surface (12) to the second surface (14).A milling cutter (100) comprising: a shank (102); an upper portion (104) having an insert seat (110), the insert seat (110) having a lower seating surface (112), a radial seating surface (116), and an axial seating surface (114); a double-sided indexable cutting insert (10) mounted in the insert seat, the indexable cutting insert (10) having a first surface (12) having a seating surface (78) defining a plane (90), a second surface (14) opposite the first surface (12), a first pair of opposing side surfaces (16, 18), and a second pair of opposing side surfaces (20, 22), the indexable cutting insert (10) further having a major cutting edge (24, 26, 28, 30) disposed at an intersection between each of the first and second surfaces (12, 14) and each of the first pair of opposing side surfaces (16, 22), A method of forming a secondary blade of the type described above in which the secondary blade of the type described above is defined for a total of four major cutting edges, wherein a minor blade (58, 60, 62, 64) is defined on an intersection between each first and second surfaces (12, 14) and a first planar facet surface (48, 54) of each second pair of opposing side surfaces (20, 22) for a total of four minor cutting edges, wherein a dip milling blade (66, 68, 70, 72) defined on the intersection between each first and second surfaces (12, 14) and a second planar facet surface (50, 56) of each second pair of opposing side surfaces (20, 22) is defined for a total of four dip milling blades, wherein the minor blades (58, 60, 62, 64) are formed at a positive angle (82) with respect to a plane (84) parallel to a central longitudinal axis (11) of the indexable cutting insert (10), wherein each second pair of opposing side surfaces (20, 20), The method of the present invention includes the first planar facet surface (48, 54) and the second planar facet surface (50, 56), wherein the second planar facet surface (50, 56) extends radially inward with respect to the first planar facet surface (48, 54), and wherein the bottom seating surface (112) of the plate seat (110) is formed at a positive angle (118) with respect to a center axis of rotation (108) of the milling cutter.The milling cutter of claim 9, wherein the indexable cutting insert (10) further comprises a corner radius (32, 34, 40, 42) connecting each first pair of opposing side surfaces (16, 18) to each second pair of opposing side surfaces (20, 22) and a contact point (36, 38, 44, 46) describing (16, 18) the corner radius (32, 34, 40, 42) of the first pair of opposing side surfaces.The bur of claim 10, wherein a distance (88) between the plane (90) of the seating surface (78) and the point of contact (36) of one of the opposing pairs of side surfaces is greater than the distance (92) between the plane (90) of the seating surface (78) and the point of contact (44) of the other pair of opposing side surfaces.The milling cutter according to any one of claims 9 to 11, wherein the main cutting edges (24, 26, 28, 30) are formed at a positive angle (86) with respect to an axis (13) extending perpendicular to a central longitudinal axis (11) of the indexable cutting insert (10).The milling cutter according to any one of claims 9 to 12, wherein the indexable cutting insert (10) is capable of performing both milling and plunge milling operations.The milling cutter of any of claims 9 to 13, wherein the indexable cutting insert (10) further comprises a countersunk head bore (80) extending entirely through the indexable cutting insert (10) from the first surface (12) to the second surface (14).

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