JP2015157337A - Cutting insert, cutting tool and method of manufacturing cut workpiece - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the possibility of insufficient holding of a chip by a holder in groove cutting.SOLUTION: A cutting insert in one embodiment includes: a top surface, a bottom surface, side surfaces, a front cutter, and a pair of side cutters. A pair of lateral side surfaces on the side surfaces respectively include: flat first lateral side surfaces adjacent to front side surfaces; and flat second lateral side surfaces adjacent to the front side surfaces via the first lateral side surfaces. In a top view, a crossing angle of virtual straight lines extended from a pair of second edge lines is larger than a crossing angle of virtual straight lines extended from a pair of first edge lines. A pair of the side cutters are formed on the first edge lines in edge lines where a pair of the lateral side surfaces and the top surface cross each other.

Description

  The present invention relates to a cutting insert, a cutting tool, and a method for manufacturing a workpiece.

  As a cutting insert used for grooving a work material, a throw-away tip described in Patent Document 1 is known. Cutting inserts used for grooving generally have cutting edges at the top and both ends of the upper surface. The chip described in Patent Document 1 has a cutting edge 13a as a cutting edge located at the leading edge of the upper surface, and a cutting edge 15a as a cutting edge located at both end edges of the upper surface.

Japanese Utility Model Publication No. 1-84903

  When the chip described in Patent Document 1 is attached to the holder, the rear end surface of the chip comes into contact with the holder. Therefore, the chip is restrained by the holder with no problem with respect to the load applied from the front end side toward the rear end side. However, the force that restrains the holder chip is relatively small with respect to a load applied from one end of the both ends toward the other. Therefore, for example, the chip may not be sufficiently restrained by the holder in the grooving lateral feed processing.

  This invention is made | formed in view of said subject, and it is providing the manufacturing method of the cutting insert which can be stably fixed to a holder in a grooving process, a cutting tool, and a cutting workpiece.

  A cutting insert according to an aspect of the present invention is formed on an upper surface, a lower surface, a side surface having a front side surface and a pair of lateral side surfaces connected to the upper surface and the lower surface, and a ridge line intersecting the upper surface and the front side surface. And a pair of horizontal cutting edges formed on a ridge line intersecting the upper surface and the pair of lateral side surfaces. The pair of lateral side surfaces respectively have a flat first lateral side surface adjacent to the front side surface and a flat second lateral side surface adjacent to the front side surface via the first lateral side surface.

  In the cutting insert according to this aspect, the first ridge line intersecting the upper surface and the pair of first lateral side surfaces and the second ridge line intersecting the upper surface and the pair of second lateral side surfaces are respectively the front view when viewed from above. The distance from each other decreases as the distance from the cutting edge increases. In addition, when viewed from the top, the angle at which the virtual straight line extending the pair of second ridge lines intersects is larger than the angle at which the virtual straight line extending the pair of first ridge lines intersects. And a pair of horizontal cutting blade is formed on the 1st ridgeline in the ridgeline which a pair of side surface and upper surface cross | intersect.

In the cutting insert of the said aspect, it has a 1st side surface and a 2nd side surface with a flat side surface. In addition, when viewed from above, the angle at which the virtual straight line extending the pair of second ridge lines intersects is larger than the angle at which the virtual straight line extending the pair of first ridge lines intersects, and the pair of horizontal cutting edges is a pair. Are formed on the first ridge line at the ridge line where the lateral side surface and the upper surface intersect. Therefore, the first lateral surface functions as a flank for the pair of lateral cutting edges, and the second lateral surface functions as a restraint surface for the holder. In this way, the cutting insert can be stably fixed to the holder on the second lateral side surface that functions as a restraint surface even against a force applied from one side of the pair of lateral side surfaces to the other.

It is a perspective view which shows the cutting insert of one Embodiment of this invention. It is the perspective view which looked at the cutting insert shown in FIG. 1 from another direction. It is a top view of the cutting insert shown in FIG. It is a top view of the cutting insert shown in FIG. It is the schematic which showed the outer periphery and through-hole of the cutting insert shown in FIG. It is a side view from the A1 direction of the cutting insert shown in FIG. It is a perspective view which shows the cutting tool of one Embodiment of this invention. It is the expansion perspective view which expanded area A2 of the cutting tool shown in FIG. It is a perspective view which shows 1 process of the manufacturing method of the cut workpiece of one Embodiment of this invention. It is a perspective view which shows 1 process of the manufacturing method of the cut workpiece of one Embodiment of this invention. It is a perspective view which shows 1 process of the manufacturing method of the cut workpiece of one Embodiment of this invention.

<Cutting insert>
Hereinafter, a cutting insert 1 according to an embodiment (hereinafter, also simply referred to as an insert 1) will be described in detail with reference to the drawings. However, in the drawings referred to below, for convenience of explanation, among the constituent members of the embodiment, only the main members necessary for explaining the present invention are shown in a simplified manner. Therefore, the cutting insert of the present invention may include any component not shown in the drawings to which the present specification refers. Moreover, the dimension of the member in each figure does not represent the dimension of an actual structural member, the dimension ratio of each member, etc. faithfully.

  As shown in FIGS. 1 to 6, the insert 1 of this embodiment has an upper surface 3, a lower surface 5, a side surface 7, a cutting edge 9, and a through hole 11. The side surface 7 is connected to each of the upper surface 3 and the lower surface 5. The insert 1 has a through hole 11 penetrating from the upper surface 3 to the lower surface 5. Further, the insert 1 has an axis X <b> 1 orthogonal to the upper surface 3 and the lower surface 5. The through hole 11 is parallel to the axis X1, and the central axis of the through hole 11 coincides with the axis X1. Therefore, in the following, the central axis is denoted by reference numeral X1.

  The through hole 11 is provided to insert a screw when the insert 1 is fixed to the holder of the cutting tool with a screw. In addition, as a method of fixing the insert 1 to the holder, a method using a clamp structure may be adopted instead of the method using screw fixing.

  In this embodiment, the penetration direction of the through hole 11 is the vertical direction. In other words, the direction in which the axis X1 extends is the vertical direction. Of the surfaces where the through holes 11 are opened, the surface on which the cutting blade 9 is formed is the upper surface 3, and the surface on which the cutting blade 9 is not formed is the lower surface 5. Therefore, the vertical direction of the cutting insert 1 of this embodiment described in detail below does not necessarily coincide with the vertical direction when the cutting insert 1 is used.

  In the insert 1 of this embodiment, the lower surface 5 is formed so that its outer shape is slightly smaller than the outer shape of the upper surface 3. When the virtual straight line X2 is set along the direction perpendicular to the axis X1 and projecting toward the work material during cutting, the upper surface 3 and the lower surface 5 have the maximum width in the direction along the virtual straight line X2. The maximum width of the upper surface 3 and the lower surface 5 is 5 to 20 mm. In the present embodiment, the upper surface 3 has a line-symmetric configuration with the virtual straight line X2 as an axis.

  Moreover, the height from the lower surface 5 to the upper surface 3 is 2-5 mm. Here, the height from the lower surface 5 to the upper surface 3 means a width in a direction parallel to the axis X <b> 1 between the upper end of the upper surface 3 and the lower end of the lower surface 5. Since the lower surface is formed slightly smaller than the upper surface 3, the side surface 7 is formed so as to approach the through hole 11 from the upper surface 3 side toward the lower surface 5 side.

  The side surface 7 has a front side surface 13, a pair of lateral side surfaces 15, and a pair of corner side surfaces 17. The front side surface 13 serves as a tip surface of the insert 1 that protrudes toward the work material during cutting. Therefore, the front side surface 13 is a region continuous with the tip of the upper surface 3.

  The pair of lateral side surfaces 15 are regions that are continuous with both side ends of the upper surface 3. Therefore, the pair of lateral side surfaces 15 are adjacent to each other via the front side surface 13 and a corner side surface 17 to be described later, and are positioned on opposite sides. A pair of corners are located between the tip and both side ends of the upper surface 3. The pair of corner side surfaces 17 are located between the front side surface 13 and the pair of lateral side surfaces 15 and are regions that are continuous with the corners of the upper surface 3.

  The pair of lateral side surfaces 15 each have a first lateral side surface 19 and a second lateral side surface 21. That is, the insert 1 has a pair of first lateral side surfaces 19 and a pair of second lateral side surfaces 21. The first lateral side surface 19 is located on the distal end side of the lateral side surface 15 and is adjacent to the corner side surface 17. Therefore, the first lateral side surface 19 in this embodiment is adjacent to the front side surface 13 via the corner side surface 17. The second lateral surface 21 is located on the rear end side of the lateral surface 15. Therefore, the second lateral side surface 21 in the present embodiment is separated from the front side surface 13 with the first lateral side surface 19 and the corner side surface 17 interposed therebetween.

  Hereinafter, among the ridge lines where the upper surface 3 and the pair of lateral side surfaces 15 intersect, the portion of the ridge line where the upper surface 3 and the pair of first lateral side surfaces 19 intersect is referred to as a first ridge line 23, The portion of the ridge line where the second lateral surface 21 intersects is referred to as a second ridge line 25. The pair of first lateral side surfaces 19 and the pair of second lateral side surfaces 21 in the present embodiment have flat surface shapes, respectively. Therefore, when viewed from above, the first ridge line 23 and the second ridge line 25 are each linear.

  A cutting edge 9 is formed on a ridge line where the upper surface 3 and the side surface 7 intersect. The insert 1 has a front cutting edge 27, a pair of side cutting edges 29, and a pair of corner cutting edges 31 as the cutting edges 9. The front cutting edge 27 is formed on a ridge line where the upper surface 3 and the front side surface 13 intersect. The pair of horizontal cutting edges 29 are formed on ridge lines where the upper surface 3 and the pair of lateral side surfaces 15 intersect. Further, the pair of corner cutting edges 31 are formed on ridge lines where the upper surface 3 and the corner side surface 17 intersect.

  At this time, the ridge line where the upper surface 3 and the side surface 7 intersect is not a strict line shape due to the intersection of the two surfaces. If the ridgeline between the upper surface 3 and the side surface 7 is sharpened at an acute angle, the durability of the cutting edge 9 is lowered. Therefore, a so-called honing process is applied to a portion where the upper surface 3 and the side surface 7 intersect, and this portion has a slightly curved surface shape.

  The pair of horizontal cutting blades 29 are located not at the entire ridgeline where the upper surface 3 and the pair of lateral side surfaces 15 intersect but at a part of the ridgeline on the tip side. Specifically, the side cutting edge 29 is located on the first ridge line 23, but is not located on the second ridge line 25. Therefore, the first lateral side surface 19 in the lateral side surface 15 functions as a flank. In the present embodiment, the horizontal cutting edge 29 is located not on the entire first ridge line 23 but on a part of the front end side close to the front cutting edge 27.

On the other hand, since the side cutting edge 29 is not located on the second ridge line 25, the second side surface 21 of the side surface 15 does not function as a flank. Therefore, when the insert 1 is mounted on the holder, the second lateral surface 21 can be brought into contact with the holder. That is, the second lateral surface 21 can function as a restraint surface.

  The pair of first ridge lines 23 and the pair of second ridge lines 25 in the present embodiment are closer to each other as the distance from the front cutting edge 27 increases. Since the pair of horizontal cutting edges 29 are formed on the pair of first ridge lines 23, the distance between the pair of horizontal cutting edges 29 increases as the distance from the front cutting edge 27 increases. Therefore, the groove side surface 7 can be cut using the pair of side cutting blades 29 when grooving.

  Furthermore, in a top view, the angle θ2 at which the virtual straight line extending the pair of second ridge lines 25 intersects is larger than the angle θ1 at which the virtual straight line extending the pair of first ridge lines 23 intersects. When the angle θ1 and the angle θ2 are the same value or when the angle θ1 is larger than the angle θ2, the second lateral side surface 21 of the holder is restrained to prevent the holder from contacting the work material. The thickness of the parts to be reduced must be reduced. Therefore, the force which restrains the 2nd side surface 21 of insert 1 may become inadequate.

  However, in the insert 1 of the present embodiment, since the angle θ2 is larger than the angle θ1, when the second lateral side surface 21 continuous with the second ridge line 25 is used as a restraint surface, a large thickness of the holder is ensured. Easy to do. Therefore, the cutting insert 1 can be stably fixed to the holder on the second lateral side surface 21 that functions as a restraint surface even with respect to a force applied from one side of the pair of lateral side surfaces 15 to the other side.

  When the values of the angles θ1 and θ2 are small and evaluation is difficult, the angles θ′1, θ ′ formed by the virtual straight line X3 parallel to the virtual straight line X2 and the first ridge line 23 and the second ridge line 25 It may be evaluated using 2. Since the upper surface 3 is line symmetric about the virtual straight line X2, the angles θ′1 and θ′2 formed by the virtual straight line X3 and the first ridge line 23 and the second ridge line 25 are half of the angles θ1 and θ2. This is because it becomes a value.

  In the insert 1 of the present embodiment, the angle θ1 is set to about 10 to 20 °, for example. That is, the angle θ′1 is set to about 5 to 10 °, for example. Further, the angle θ2 is set to about 40 to 70 °, for example. That is, the angle θ′2 is set to about 20 to 35 °, for example.

  The insert 1 of this embodiment has a front cutting edge 27, a pair of side cutting edges 29, and a pair of corner cutting edges 31 as the cutting edges 9. The front cutting edge 27 may have a linear shape when viewed from above, but in the present embodiment, the center has a shape that is recessed toward the rear end side.

  The front cutting edge 27 has a pair of first front cutting edge 27a and second front cutting edge 27b. The pair of first front cutting edges 27a are connected to the pair of corner cutting edges 31, respectively. The pair of first front cutting edges 27 a has a linear shape, and approaches the rear end side as the distance from the corner cutting edge 31 increases. Therefore, the pair of first front cutting edges 27a is configured to be inclined with respect to the virtual straight line X2 in a top view.

  The second front cutting edge 27b is located between the pair of first front cutting edges 27a, and is smoothly connected to the first front cutting edge 27a when viewed from above. The second front cutting edge 27b has an arc shape that is recessed toward the rear end side. Note that the term “smoothly connected” means that no bending point is formed at the boundary between the first front cutting edge 27a and the second front cutting edge 27b. The front cutting edge 27 has a pair of the first front cutting edge 27a and the second front cutting edge 27b configured as described above, so that the center is recessed toward the rear end in a top view. ing.

  The pair of corner cutting edges 31 positioned between the front cutting edge 27 and the pair of horizontal cutting edges 29 have an arc shape that is convex outward in a top view. At this time, the corner bisector of the pair of corner cutting edges 31, in other words, the corner cutting edge 31, and the linear first front cutting edge 27 a and the side cutting edge 29 that are respectively adjacent to the corner cutting edge 31, The corner bisector of the cutting edge region constituted by the crossing the second ridge line 25 in a top view.

  When cutting is performed using the corner cutting edge 31, a load is applied from the corner cutting edge 31 toward the direction along the corner bisector of the corner cutting edge 31. However, instead of the first lateral surface 19 that functions as a flank, the second lateral surface 21 that functions as a constraining surface is positioned on the extended line of the corner bisector. Therefore, the insert 1 can be stably fixed to the holder against a load applied from the corner cutting edge 31.

  Moreover, although the insert 1 of this embodiment has the through-hole 11 as above-mentioned, in the top view, the central axis X1 of the through-hole 11 is a pair of 1st ridgeline 23 and a pair of 2nd ridgeline 25. It is located closer to the front side surface 13 than the boundary. Since the pair of first ridge lines 23 and the pair of second ridge lines 25 are closer to each other as they are away from the front cutting edge 27, the pair of first ridge lines 23 and the pair of second ridge lines 25 are more paired than the pair of second ridge lines 25. The interval between the first ridge lines 23 is wider.

  Since the central axis X1 of the through hole 11 is located between the pair of first ridge lines 23 as described above, the inner diameter of the through hole 11 in the top view can be increased. Therefore, since the screw for screwing the insert 1 to the holder can be increased, the insert 1 can be stably fixed to the holder. Further, it is easy to ensure a large thickness between the through hole 11 and the pair of lateral side surfaces 15 in a top view. Therefore, the durability of the insert 1 can be improved.

  Furthermore, in the insert 1 of the present embodiment, the corner bisector of the pair of corner cutting edges 31 passes through the central axis X1 of the through hole 11 in a top view. When the through hole 11 is thus positioned, a load applied from the corner cutting edge 31 can be received by a screw inserted into the through hole 11. Therefore, it becomes possible to fix the insert 1 to the holder stably. In addition, when the corner bisector of the pair of corner cutting edges 31 passes through the central axis X1 of the through hole 11, the insert 1 is centered on the central axis X1 due to the load applied from the corner cutting edge 31. Rotation can be suppressed.

  Moreover, in the insert 1 of this embodiment, although the 2nd front cutting edge 27b and a pair of corner cutting blade 31 are circular arc shape, the curvature radius of the 2nd front cutting edge 27b is a pair of corner cutting edge 31. Greater than the radius of curvature. Due to the pair of corner cutting edges 31, the load applied from the pair of corner cutting edges 31 tends to concentrate on the second front cutting edge 27 b of the front cutting edges 27. However, since the radius of curvature of the second front cutting edge 27b is relatively large, it is possible to suppress the stress from being concentrated on a specific region of the second front cutting edge 27b.

  The upper surface 3 has a land surface 33, a breaker groove 35 and a main surface 37. The land surface 33 is located on the outer periphery of the upper surface 3 and is connected to the front cutting edge 27, the pair of horizontal cutting edges 29, and the pair of corner cutting edges 31. Specifically, the land surfaces 33 are respectively located inside the cutting blades 9 so as to be continuous with the cutting blades 9.

The breaker groove 35 is located closer to the center of the upper surface 3 than the land surface 33. The breaker groove 35 has a concave configuration formed by a surface including the first inclined surface and the second inclined surface. The height of the first inclined surface decreases toward the center of the upper surface 3. The second inclined surface is located closer to the center than the first inclined surface, and increases in height toward the center of the upper surface 3. The main surface 37 is located closer to the center than the breaker groove 35. The main surface 37 is a flat surface perpendicular to the axis X1.

  The land surface 33 is formed to be a flat surface substantially parallel to the lower surface 5 or an inclined surface whose height decreases toward the center of the upper surface 3. Note that “substantially parallel” does not mean that they are strictly parallel, but may mean that they may have a slight inclination of about ± 5 °. If it is difficult to evaluate whether the lower surface 5 is not flat but parallel to the lower surface 5, it may be compared with the axis X <b> 1 instead of the lower surface 5. That is, the land surface 33 may be evaluated based on whether or not it is perpendicular to the axis X1.

  Examples of the material of the cutting insert 1 include cemented carbide or cermet. As the composition of the cemented carbide, for example, WC-Co produced by adding cobalt (Co) powder to tungsten carbide (WC) and sintering, and WC-Co obtained by adding titanium carbide (TiC) to WC-Co. There is WC-TiC-TaC-Co in which tantalum carbide (TaC) is added to TiC-Co or WC-TiC-Co. The cermet is a sintered composite material in which a metal is combined with a ceramic component, and specifically includes a titanium compound mainly composed of titanium carbide (TiC) or titanium nitride (TiN).

The surface of the cutting insert 1 may be coated with a film using a chemical vapor deposition (CVD) method or a physical vapor deposition (PVD) method. Examples of the composition of the coating include titanium carbide (TiC), titanium nitride (TiN), titanium carbonitride (TiCN), and alumina (Al ₂ O ₃ ).

<Cutting tools>
Next, a cutting tool 101 according to an embodiment of the present invention will be described with reference to the drawings. 8 is an enlarged cross-sectional view in which a portion where the cutting insert 1 is attached to the holder 103 in FIG. 7 is enlarged.

  As shown in FIGS. 7 and 8, the cutting tool 101 of the present embodiment is mounted in the insert pocket 105 so that the holder 103 having the insert pocket 105 on the tip side and the cutting blade 9 protrude from the tip of the holder 103. The cutting insert 1 represented by the above embodiment is provided.

  The holder 103 has an elongated bar shape. One insert pocket 105 is provided on the tip side of the holder 103. The insert pocket 105 is a part to which the cutting insert 1 is mounted, and is open to the front end surface of the holder 103. At this time, since the insert pocket 105 is also open to the side surface 7 of the holder 103, the cutting insert 1 can be easily mounted. The insert pocket 105 has a seating surface parallel to the lower surface 5 of the holder 103 and a constraining side surface 7 positioned in a direction in which the seating surface intersects.

  The cutting insert 1 is mounted in the insert pocket 105. The cutting insert 1 is mounted so that the cutting edge 9 protrudes toward the tip side of the holder 103. Specifically, the cutting insert 1 is mounted on the holder 103 such that the front cutting edge 27, the pair of side cutting edges 29, and the pair of corner cutting edges 31 protrude outward from the tip of the holder 103.

In the present embodiment, the cutting insert 1 is fixed to the holder 103 with screws 107. That is, the screw 107 is inserted into the through hole 11 of the cutting insert 1, and the tip of the screw 107 is inserted into a screw hole (not shown) formed in the insert pocket 105.
Screw 107 and screw hole are screwed together.

  As the holder 103, steel, cast iron, or the like can be used. In particular, it is preferable to use steel having high toughness among these members.

<Manufacturing method of cut product>
Next, the manufacturing method of the cut workpiece of one Embodiment of this invention is demonstrated using drawing.

The cut workpiece is produced by cutting a work material. The manufacturing method of the cut workpiece in the present embodiment includes the following steps. That is,
(1) rotating the work material 201;
(2) a step of bringing the cutting blade 9 of the cutting tool 101 represented by the above embodiment into contact with the rotating work material 201;
(3) a step of separating the cutting tool 101 from the work material 201;
It has.

  More specifically, first, as shown in FIG. 9, the work material 201 is rotated around the axis Y in the Y1 direction. Further, the cutting tool 101 is moved closer to the workpiece 201 by moving the cutting tool 101 in the Y2 direction. Next, as shown in FIG. 10, the work material 201 is cut by bringing the front cutting edge, which is the cutting edge 9 of the cutting tool 101, a pair of side cutting edges, and a pair of corner cutting edges into contact with the work material 201. To do. At this time, a flat groove bottom can be formed by reciprocating the cutting tool 101 in the direction along the axis Y and laterally feeding it. Then, as shown in FIG. 11, the cutting tool 101 is moved away from the work material 201 by moving the cutting tool 101 in the Y3 direction.

  In the present embodiment, the cutting tool 101 is approached while the axis Y is fixed and the work material 201 is rotated. In FIG. 10, the work material 201 is cut by bringing the cutting edge 9 of the cutting insert 1 into contact with the rotating work material 201. In FIG. 11, the cutting tool 101 is moved away while the work material 201 is rotated. In the cutting in the manufacturing method of the present embodiment, the cutting tool 101 is moved to contact the work material 201 or moved away from the work material 201 in each step. Of course, it is not limited to such a form.

  For example, the work material 201 may be brought close to the cutting tool 101 in the step (1). Similarly, in the step (3), the work material 201 may be moved away from the cutting tool 101. In the case of continuing the cutting process, the state in which the cutting tool 101 is rotated and the cutting blade 9 of the cutting insert 1 is brought into contact with a different part of the work material 201 may be repeated.

  Note that typical examples of the material of the work material 201 include carbon steel, alloy steel, stainless steel, cast iron, and non-ferrous metal.

DESCRIPTION OF SYMBOLS 1 ... Cutting insert 3 ... Upper surface 5 ... Lower surface 7 ... Side surface 9 ... Cutting blade 11 ... Through-hole 13 ... Front side surface 15 ... Lateral side surface 17 ... Corner Side 19 ... First lateral side 21 ... Second lateral side 23 ... First ridge line 25 ... Second ridge line 27 ... Front cutting edge 27a ... First front Cutting edge 27b ... second front cutting edge 29 ... horizontal cutting edge 31 ... corner cutting edge 33 ... land surface 35 ... breaker groove 37 ... main surface 101 ... cutting tool 103 ... Holder 105 ... Insert pocket 107 ... Screw 201 ... Work material

Claims (8)

The top surface;
The bottom surface;
A side surface having a front side surface and a pair of lateral side surfaces connected to each of the upper surface and the lower surface;
A front cutting edge formed on a ridge line intersecting the upper surface and the front side surface;
A pair of horizontal cutting edges formed on a ridge line intersecting the upper surface and the pair of lateral side surfaces,
The pair of lateral side surfaces each have a flat first lateral side surface adjacent to the front side surface and a flat second lateral side surface adjacent to the front side surface via the first lateral side surface,
When viewed from above, the first ridge line intersecting the upper surface and the pair of first lateral sides and the second ridge line intersecting the upper surface and the pair of second lateral sides are respectively the front cutting edge. As you move away from each other, the distance between them gets closer,
In a top view, the angle at which the virtual line extending the pair of second ridge lines intersects is larger than the angle at which the virtual line extending the pair of first ridge lines intersects,
The pair of horizontal cutting edges are located on the first ridge line in a ridge line where the pair of lateral side surfaces and the upper surface intersect with each other. And further comprising a pair of arcuate corner cutting edges positioned between the front cutting edge and the pair of horizontal cutting edges,
The cutting insert according to claim 1, wherein a corner bisector of the pair of corner cutting blades intersects the second ridge line in a top view. Further comprising a through-hole penetrating from the upper surface to the lower surface;
The center axis of the through hole is located closer to the front side surface than a boundary between the pair of first ridge lines and the pair of second ridge lines in a top view. Cutting insert as described in.   The cutting insert according to claim 3, wherein a corner bisector of the pair of corner cutting blades passes through a central axis of the through hole in a top view. The front cutting edge includes a pair of linear first front cutting edges connected to the pair of corner cutting edges, and a concave arcuate second located between the pair of first front cutting edges. With a front cutting edge,
3. The cutting insert according to claim 2, wherein, in a top view, a curvature radius of the second front cutting edge is larger than a curvature radius of the pair of corner cutting edges.   The cutting insert according to claim 1, wherein the second ridge line is longer than the first ridge line in a top view. A holder having an insert pocket on the tip side;
The second lateral side surface is constrained in the insert pocket, and the front cutting edge and the pair of horizontal cutting edges are attached to the insert pocket so as to protrude from the tip of the holder. A cutting tool comprising the cutting insert according to any one of the above. A step of rotating the work material;
Contacting the front cutting edge and the pair of side cutting edges of the cutting tool according to claim 7 to the rotating work material;
The manufacturing method of the cut workpiece provided with the process of separating the said cutting tool from the said workpiece.