cutting inserts

Abstract

A cutting insert is provided that reduces chipping and roughens the workpiece surface during back-turning. The cutting insert comprises a rake face, a peripheral side surface, a front cutting edge provided on a ridgeline between the rake face and the peripheral side surface, and a main cutting edge provided on the ridgeline and continuous with the front cutting edge. The main cutting edge extends in a direction that forms an obtuse angle with the direction in which the front cutting edge extends. The main cutting edge is curved in a U-shape over the entire length of an effective edge region that functions as a cutting edge, with its deepest point located closer to the corner side than a position where a straight line connecting the ends of the main cutting edge is divided 2:1 from the corner side adjacent to the front cutting edge.

Description

Technical Field

[0001] The present invention relates to a cutting insert. Background Art

[0002] One of the requirements for improvement of cutting inserts for back turning in automatic lathes is chip handleability (for example, see Patent Document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Publication No. 2019-104088

[0006] Technical issues

[0007] Post-turning tends to cause chips to lengthen, but these long chips can come into contact with the workpiece surface, roughening it. In particular, post-turning requires a high level of chip management because the groove end faces formed during grooving and the outer diameter surface formed during outer diameter machining become the machined surfaces.

[0008] The present invention has been made to solve such a problem, and provides a cutting insert that produces less chips during post-turning and thus roughens the machined surface of a workpiece. Summary of the Invention

[0009] One aspect of the present invention relates to a cutting insert comprising a rake face, a peripheral side surface, a front cutting edge disposed on a ridgeline between the rake face and the peripheral side surface, and a main cutting edge disposed on the ridgeline and continuous with the front cutting edge. The main cutting edge extends in a direction that forms an obtuse angle with the direction of extension of the front cutting edge. The main cutting edge is curved into a U-shape over the entire length of its effective cutting edge region, with its deepest point located closer to the corner side adjacent to the front cutting edge than a position where a straight line connecting the two ends of the main cutting edge is divided 2:1 from the corner side. This cutting insert, constructed in this manner, creates an offset curved portion in the chip cross section during external diameter machining, where chips tend to become longer and with greater depth of cut. Its rigidity prevents chip distortion. Consequently, when a chip collides with the wall of a chip breaker, the force applied to the chip from the wall of the chip breaker tends to bend the chip rather than causing it to twist. This bending force results in finer chips. Compared to long spiral chips, finer chips are less likely to roughen the machined surface.

[0010] According to the present invention, a cutting insert can be provided which produces less roughening of the machined surface of a workpiece due to chips during post-turning. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is an overall perspective view of a cutting tool to which the cutting insert according to the present embodiment is attached.

[0012] Figure 2 This is a diagram illustrating the cutting process.

[0013] Figure 3 It is an overall three-dimensional view of the cutting blade.

[0014] Figure 4 This is a partial enlarged view of the cutting edge of the cutting insert.

[0015] Figure 5 It is a part of the top view of the cutting insert.

[0016] Figure 6 This is a partial enlarged view showing the periphery of the main cutting edge.

[0017] Figure 7 This is a diagram explaining chips generated by the main cutting edge.

[0018] Figure 8 It is a cross-sectional view through the main cutting edge.

[0019] Figure 9 It is a partial enlarged view showing the periphery of the front cutting edge.

[0020] Description of main component symbols

[0021] Cutting insert 100

[0022] Front cutting edge 110

[0023] Front cutting edge flank 111

[0024] Front rake face 112

[0025] Main cutting edge 120

[0026] Main cutting edge flank 121

[0027] Transverse rake face 122

[0028] Top surface 130

[0029] Chip breaker wall 131

[0030] Chip breaker surface 132

[0031] First side 133

[0032] Second side 134

[0033] First Corner 141

[0034] Second corner 142

[0035] The third corner 143

[0036] Mounting hole 190

[0037] Recess 191

[0038] Cutting Tools 200

[0039] Main body 210

[0040] Mounting Block 220

[0041] Grip 230

[0042] Mounting screw 300

[0043] Workpiece 900

[0044] Groove end face 910

[0045] Outer diameter surface 920

[0046] Chips 990

[0047] Section 991

[0048] Variation Section 992 DETAILED DESCRIPTION

[0049] Embodiments of the present invention will be described with reference to the accompanying drawings. In each figure, identical or similar components are designated by the same reference numerals. Furthermore, in each figure, when multiple components with identical or similar components are depicted, some may be designated by the same reference numerals to avoid clutter. Furthermore, not all components described in the embodiments are essential for solving the problems.

[0050] Figure 1 This is an overall perspective view of a cutting tool 200 equipped with a cutting insert 100 according to this embodiment. The cutting tool 200 according to this embodiment is a cutting tool for a lathe, particularly for back-turning. A main body 210 includes a mounting seat 220 for mounting the cutting insert 100 and two grips 230 for clamping the cutting insert 100.

[0051] The mounting seat 220 is a mounting surface for the cutting insert 100, located near the front end of the main body 210. The mounting seat 220 is provided with an internally threaded hole. When the cutting insert 100 is mounted, the internally threaded hole is coaxial with the mounting hole 190, which is located approximately at the center of the cutting insert 100. The cutting insert 100 is secured to the mounting seat 220 by a mounting screw 300, which is threadedly engaged with the internally threaded hole 190 through the mounting hole 190.

[0052] The two grips 230 are shaped to protrude from the mounting seat 220 and face each other. The two recesses 191 provided in the middle of the cutting insert 100 allow the cutting insert 100 placed on the mounting seat 220 to engage with the grips 230 to prevent the cutting insert 100 from rotating and shaking.

[0053] Furthermore, as shown in the figure, the X-axis, Y-axis, and Z-axis are defined. That is, the direction in which the gripping portion 230 holds the cutting insert 100 is the Y-axis direction, the direction in which the mounting hole 190 is positioned when the cutting insert 100 is mounted on the mounting seat 220 is the Z-axis direction, and the direction perpendicular to the Y-axis and Z-axis directions is the X-axis direction. Figure 1 The orientation of the components shown in the various drawings is shown with reference to the illustrated mounted state of the cutting insert 100 and the same coordinate axes.

[0054] Figure 2 This is a diagram illustrating the machining process of cutting. In particular, Figure 2 (A) shows the state of slotting processing, Figure 2 (B) shows the state of outer diameter machining (post-turning machining). In either machining, the workpiece 900 is fixed to the chuck of the lathe and rotated in the direction of arrow RD around the rotation axis WA.

[0055] exist Figure 2 In the grooving process shown in (A), the cutting insert 100 fixed to the main body 210 is fed toward the rotation axis WA of the workpiece 900 as indicated by the white arrow. The front cutting edge 110, which acts primarily in the feed direction, cuts the workpiece 900 to form a groove. The chips generated by the cutting by the front cutting edge 110 are guided by the chip breaker groove surface 132 and discharged to the outside in the direction of the dotted arrow.

[0056] When the target depth is reached, the grooving process is completed and the outer diameter processing is continued. Figure 2 In the outer diameter machining process shown in (B), the cutting insert 100 is fed in the direction of the rotation axis WA of the workpiece 900, as indicated by the white arrow. The main cutting edge 120, acting primarily in this feed direction, cuts the workpiece 900, expanding the groove in the back-turning direction. The chips generated by the cutting by the main cutting edge 120 are guided by the chip breaker surface 132 and discharged to the outside in the direction of the dotted arrow.

[0057] Through these machining steps, a groove end face 910 and an outer diameter surface 920 are formed on the workpiece 900. Furthermore, during outer diameter machining, the outer diameter surface 920 is also machined by the front cutting edge 110. The groove end face 910 and outer diameter surface 920 thus formed are the surfaces machined by the cutting insert 100. To prevent generated chips from coming into contact with these machined surfaces and causing them to become rough, the cutting insert 100 of this embodiment has been designed with respect to the shapes of the front cutting edge 110 and the main cutting edge 120. These features will be described below.

[0058] Figure 3 1 is an overall perspective view of the cutting insert 100. The cutting insert 100 has a generally plate-like parallelogram shape, with a mounting hole 190 provided at its center for insertion of the mounting screw 300. As described above, a recess 191 is provided in the vertical direction (Y-axis direction) of the mounting hole 190, into which the grip 230 of the mounting seat 220 is inserted.

[0059] Within the generally parallelogram-shaped insert, the front cutting edge 110 and the main cutting edge 120 are located at the ends of the upper and lower edges, respectively, which intersect the beveled edge at an acute angle. In other words, a single cutting insert 100 is provided with two sets of front cutting edges 110 and main cutting edges 120. If one cutting edge reaches its limit of use, the other cutting edge can be reinstalled by rotating it 180° about the central axis Za of the mounting hole 190.

[0060] Figure 4 1 is a partial enlarged view of the edge of the cutting insert 100. Specifically, Figure 3 An enlarged view of part A of Figure 4 (A) is a perspective view of the cutting insert 100 when it is mounted on the mounting seat 220, viewed from the mounting surface side. Figure 4 (B) is a perspective view viewed from the side opposite to the mounting surface side.

[0061] The front cutting edge 110 and the main cutting edge 120 are surrounded by an upper surface 130 parallel to the XZ plane and four peripheral side surfaces intersecting the upper surface 130 at angles approximately 90 degrees. The four peripheral side surfaces include: a first side surface 133, which is the surface opposite the mounting surface that contacts the mounting seat 220; a main cutting edge flank 121, which is continuous with the first side surface 133 and serves as the flank of the main cutting edge; a front cutting edge flank 111, which is continuous with the main cutting edge flank 121 and serves as the flank of the front cutting edge 110; and a second side surface 134, which is continuous with the front cutting edge flank 111 and serves as the mounting surface that contacts the mounting seat 220. Furthermore, in this embodiment, although the main cutting edge flank 121 and the front cutting edge flank 111, as well as the front cutting edge flank 111 and the second side surface 134, are connected by R-curved surfaces, and the front cutting edge flank 111 is composed of two flat surfaces, the adoption of these structures is optional.

[0062] A recessed portion serving as a chip breaker is excavated from the upper surface 130. Specifically, the recessed portion comprises a curved transverse rake face 122, a front rake face 112, a chip breaker wall surface 131, and a chip breaker surface 132. The main cutting edge 120 is formed on the ridgeline between the main cutting edge flank face 121 and the transverse rake face 122. The front cutting edge 110 is formed on the ridgeline between the front cutting edge flank face 111 and the front rake face 112.

[0063] The first corner 141 is the boundary point between the main cutting edge 120 and the front cutting edge 110. The second corner 142 is the end of the front cutting edge 110 on the side opposite to the first corner 141. The third corner 143 is the end of the main cutting edge 120 on the side opposite to the first corner 141. In other words, the ridgeline from the first corner 141 to the second corner 142 is the effective edge area of ​​the front cutting edge 110, and the ridgeline from the first corner 141 to the third corner 143 is the effective edge area of ​​the main cutting edge 120. The effective edge area is the area that functions as a cutting edge. The cutting edge can be formed by grinding. The main cutting edge 120 and the front cutting edge 110 are arranged continuously, and the first corner 141 is sandwiched between the main cutting edge 120 and the front cutting edge 110. The extension direction of the main cutting edge 120 and the extension direction of the front cutting edge 110 form an obtuse angle at the first corner 141.

[0064] In this embodiment, since an R-curved surface is provided between the front cutting edge flank 111 and the main cutting edge flank 121, the first corner 141 is located on the ridgeline between the R-curved surface and the recess. Here, the first corner 141 is defined as the midpoint on this ridgeline. Furthermore, an R-curved surface is provided between the front cutting edge flank 111 and the second side surface 134. Similar to the first corner 141, the second corner 142 is defined as the midpoint on the ridgeline between the R-curved surface and the recess. Furthermore, when no R-curved surface is provided, each corner can be simply defined as the point where adjacent ridgelines intersect.

[0065] The lateral rake face 122 and the front rake face 112 are adjacent to each other and together form an inclined surface that descends toward the chip breaker surface 132. The chip breaker surface 132 forms a generally J-shaped groove bottom surface that continues from the portion adjacent to the lateral rake face 122 to the portion adjacent to the front rake face 112. The chip breaker wall surface 131 forms a wall surface that continues from the chip breaker surface 132 and rises to the boundary of the upper surface 130. Like the chip breaker surface 132, the chip breaker wall surface 131 is generally J-shaped.

[0066] The chips produced by the front cutting edge 110 slide on the front rake face 112 and collide with the chip breaker surface 132, thereby being broken intermittently by force. Figure 2Similarly, the chips generated by the main cutting edge 120 slide on the transverse rake face 122 and collide with the chip breaker surface 132, thereby being broken intermittently by force. Figure 2 The shown chip is discharged to the outside along the chip breaker surface 132.

[0067] Figure 5 This is a portion of a top view of the cutting insert 100. Features of the cutting insert 100 are described in sequence using view B, which shows the main cutting edge 120 viewed from the front, a CC cross-sectional view taken along a plane perpendicular to the main cutting edge 120, and view D, which shows the front cutting edge 110 viewed from the front.

[0068] Figure 6 yes Figure 5 View B is a partial enlarged view showing the periphery of the main cutting edge 120. As shown in the figure, the main cutting edge 120 is bent into a U-shape over the entire length of the effective cutting edge area. The deepest point of the bottom of the U-shape is located in an area closer to the first corner 141 side than the position where the straight line connecting the first corner 141 and the third corner 153, which are the two ends of the main cutting edge 120, is divided from the first corner 141 side at a ratio of 2:1. In addition, the deepest point is preferably located in an area closer to the third corner 143 side than the position where the straight line connecting the first corner 141 and the third corner 143 is divided at a ratio of 1:1. The U-shaped bend can be a convex downward as a whole, and the entire bend can be composed of a curve or a portion of a straight line.

[0069] Figure 7 1 and 2 are diagrams illustrating chips 990 generated by the major cutting edge 120. Here, it is assumed that the cutting depth into the workpiece is greater than the deepest point of the U-shape of the major cutting edge 120.

[0070] For the chips 990 generated by the main cutting edge 120 bent into a U-shape, the portion corresponding to the deepest point of the U-shape in the cross section 991 is the curved portion 992. That is, in the cross section 991, the curved portion 992 appears near the third corner 143. The rigidity generated by the bending of the cross section 991 in this way plays the role of preventing the chips 99 from twisting in the direction toward the chip breaker groove wall 131. Therefore, when the chips 990 collide with the chip breaker groove wall 131, the force that the chips 990 receive from the chip breaker groove wall 131 tends to become a force that bends the chips 990, rather than promoting the twisting of the chips 990. Through this bending force, the generated chips 990 are broken into small pieces. Compared with long spiral chips, the small chips 990 are less likely to cause the machined surface to become rough.

[0071] Figure 8 yes Figure 5CC cross-sectional view. As shown, the concave portion is connected to the upper surface 130 via a continuous lateral rake face 122, a chip breaker surface 132, and a chip breaker wall 131. As described above, the chips 990 with a curved cross-section collide with the chip breaker wall 131 and break off intermittently. They are then pushed by the chips generated from the front cutting edge 110 and discharged to the outside along the chip breaker surface 132.

[0072] Figure 9 yes Figure 5 The D view is a partial enlarged view showing the periphery of the front cutting edge 110. As shown in the figure, the front cutting edge 110 is also curved into a U-shape over the entire length of the effective cutting edge area. During machining, the front cutting edge 110 mostly uses the entire effective cutting edge area to cut the workpiece, thus almost always producing chips with a curved cross-section. Chips with a curved cross-section are less likely to twist and more likely to break than uncurved chips.

[0073] In addition, the straight line connecting the first corner 141 and the second corner 142, which are both ends of the front cutting edge 110, has an inclination angle of θ° toward the deep side of the U-shape with respect to the straight line parallel to the central axis Za of the mounting hole 190 and passing through one end on the side of the first corner 141. In other words, the straight line connecting the first corner 141 and the second corner 142 has an intersection angle of θ° with respect to the direction of the rotation axis WA of the workpiece 900, so that the end on the side of the first corner 141 becomes the rotation upstream side of the workpiece 900. θ is greater than 2 and less than 8, preferably greater than 3.5 and less than 8. When having such an inclination angle, the front cutting edge 110 cuts the workpiece 900 from the side of the first corner 141, so that the chips are naturally discharged in a direction away from the machined surface. That is, the possibility of roughening the machined surface can be reduced.

[0074] An example of the present embodiment has been described above, but the present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the purpose of the present invention.

Claims

1. A cutting insert comprising: Rake face; peripheral side; a front cutting edge provided on the rake face and the ridge line of the outer peripheral side surface; as well as A main cutting edge is provided on the ridge line and is continuous with the front cutting edge, wherein an extension direction of the main cutting edge forms an obtuse angle with an extension direction of the front cutting edge. In the front view of the peripheral side surface with the main cutting edge as the ridgeline, the main cutting edge is concave and curved into a U-shape over the entire length of the effective edge area that functions as a cutting edge, and its deepest point is located in an area closer to the corner side than a position obtained by dividing a straight line connecting the two ends of the main cutting edge from the corner side adjacent to the front cutting edge at a ratio of 2:1, and is located in an area farther away from the corner side than a position obtained by dividing the straight line at a ratio of 1:

1.

2. The cutting insert according to claim 1, wherein The front cutting edge is bent into a U-shape over the entire length of an effective edge region functioning as a cutting edge.

3. The cutting insert according to claim 2, wherein A straight line connecting both ends of the front cutting edge has an inclination angle of 2° to 8° toward the deep side of the U shape relative to a straight line parallel to the central axis of the mounting hole for mounting the cutting tool and passing through one end on the corner side.

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