Cutting insert, cutting tool, and method for manufacturing cut workpiece

Abstract

A cutting insert according to one non-limiting aspect of the present disclosure has a main body portion and a cutting portion positioned on a tip end side of the main body portion. The cutting portion has an upper surface that extends from a tip end surface toward the main body portion. The upper surface has a pair of first breaker projections, each extending from the main body portion side toward the tip end surface, and a pair of second breaker projections, extending respectively from the first breaker projections toward the tip end surface. Each of the pair of first breaker projections has a forward surface positioned on the tip end side and having a flat inclined region. The pair of second breaker projections each have a curved surface shape and extend respectively from the forward surfaces of the pair of first breaker projections toward the tip end surface.

Description

Cutting insert, cutting tool, and method for manufacturing machined product CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to Japanese Patent Application No. 2023-185156, filed on October 30, 2023, the entire disclosure of which is incorporated herein by reference.

[0002] The present disclosure relates to a cutting insert and a cutting tool used in cutting a workpiece, and a method for manufacturing a machined product. Examples of cutting include turning and milling. Examples of turning include internal diameter machining, external diameter machining, grooving, and cut-off.

[0003] An example of a cutting tool used when cutting a workpiece is the cutting tool described in Japanese Patent Laid-Open No. 9-174308 (Patent Document 1). The cutting tool described in Patent Document 1 is a tool used for groove machining, and includes a holder and a cutting insert (hereinafter simply referred to as "insert"). The insert described in Patent Document 1 has a pair of breaker protrusions extending from the tip cutting edge. During cutting, chips are brought into contact with the pair of breaker protrusions to deform the chips and control the speed at which the chips flow.

[0004] However, a simple design with only a pair of breaker protrusions is not very versatile for various cutting conditions and workpiece materials. For example, when cutting with a small feed rate or when cutting soft materials such as aluminum, mild steel, or low-carbon steel, it is difficult to control the deformation of the chips, and the breaker protrusions have limited effect on controlling the speed at which the chips flow, i.e., on braking the chips.

[0005] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide an insert that is highly versatile in terms of cutting conditions and types of workpiece materials.

[0006] A non-limiting one-sided cutting insert of the present disclosure has a rod shape extending along a central axis from a tip end to a rear end. The cutting insert has a body portion and a cutting portion located closer to the tip end than the body portion. The cutting portion has a tip surface located closer to the tip end, an upper surface extending from the tip surface toward the body portion, a first side surface adjacent to the tip surface and the upper surface, and a tip cutting edge located at the intersection of the tip surface and the upper surface.

[0007] The upper surface has a pair of first breaker protrusions extending from the main body toward the tip surface, and a pair of second breaker protrusions extending from the first breaker protrusions toward the tip surface. Each of the pair of first breaker protrusions has a front surface located on the tip side and having a flat inclined region. The pair of second breaker protrusions has a curved shape and extends from the front surface of the pair of first breaker protrusions toward the tip surface.

[0008] 5 is a perspective view showing an unlimited single-sided cutting insert of the present disclosure. FIG. 1 is an enlarged view of region II shown in FIG. 1. FIG. 1 is a plan view showing the top surface of the cutting insert shown in FIG. 1 from the front. FIG. 3 is an enlarged view of region IV shown in FIG. 3. FIG. 3 is a side view of the cutting insert shown in FIG. 3 as viewed from direction V. FIG. 5 is an enlarged view of region VI shown in FIG. 5. FIG. 3 is a plan view of the cutting insert shown in FIG. 3 as viewed from direction VII. FIG. 3 is an enlarged view of the tip side of the cutting insert shown in FIG. 3. A sectional view of section IX of the cutting insert shown in FIG. 8. A sectional view of section X of the cutting insert shown in FIG. 8. A sectional view of section XI of the cutting insert shown in FIG. 8. A sectional view of section XII of the cutting insert shown in FIG. 8. A sectional view of section XIII of the cutting insert shown in FIG. 8. A sectional view of section XIV of the cutting insert shown in FIG. 8. An enlarged view of the tip side of the cutting insert shown in FIG. 3, which is a sectional view parallel to the central axis and the tip cutting edge. FIG. 5 is a perspective view showing an unlimited single-sided cutting tool of the present disclosure. FIG. 5 is a schematic view showing one step in a unlimited method of manufacturing a single-sided machined product of the present disclosure. FIG. 5 is a schematic view showing one step in a unlimited method of manufacturing a single-sided machined product of the present disclosure. 1 is a schematic diagram showing a step in a non-limiting method of manufacturing a one-sided machined product according to the present disclosure.

[0009] <Cutting Insert> Hereinafter, a non-limiting one-sided cutting insert 1 (hereinafter also simply referred to as "insert 1") of the present disclosure will be described in detail with reference to the drawings. However, for the sake of convenience, the drawings referred to below show only the main components necessary for explaining the embodiment in a simplified form. Therefore, the insert 1 may include any components not shown in the drawings referred to. Furthermore, the dimensions of the components in the drawings do not faithfully represent the actual dimensions of the components and the dimensional ratios of the components.

[0010] The insert 1 may have a rod shape extending along the central axis O1 from the front end 1a to the rear end 1b, as in the non-limiting example shown in Figures 1 to 15. The insert 1 may have a prismatic shape. The insert 1 may have a quadrangular prism shape. Note that the quadrangular prism shape may be roughly a quadrangular prism shape, and does not necessarily have to be a quadrangular prism shape in the strict sense.

[0011] The insert 1 may have a body portion 3 and a cutting portion 5, as shown by way of non-limiting example in FIGS.

[0012] The main body portion 3 can function as a portion that is fixed to the holder when the insert 1 is attached to the holder. The main body portion 3 may be located at the center of the insert 1 in the direction along the central axis O1.

[0013] The cutting portion 5 may be located closer to the tip 1a than the main body portion 3. The cutting portion 5 is capable of coming into contact with the workpiece, and can function as a portion that plays a major role in cutting (e.g., grooving) the workpiece.

[0014] The insert 1 may further include a cutting portion 7 located closer to the rear end 1b than the main body portion 3. In this case, the cutting portion 5 may be referred to as the first cutting portion 5, and the cutting portion 7 may be referred to as the second cutting portion 7. The second cutting portion 7 may have the same configuration as the first cutting portion 5. Therefore, the description regarding the first cutting portion 5 may be used to understand the configuration of the second cutting portion 7.

[0015] The cutting portion 5 may have a tip surface 9, an upper surface 11, a first side surface 13, and a tip cutting edge 15, as shown in a non-limiting example in FIG.

[0016] The tip surface 9 may be located on the tip 1a side. The top surface 11 may extend from the tip surface 9 toward the main body 3. The first side surface 13 may be adjacent to the tip surface 9 and the top surface 11.

[0017] The upper surface 11 is a convenient expression and does not indicate an upward direction. For example, the upper surface 11 does not need to face upward when the insert 1 is used. This also applies to other parts that include the expressions "up" and "down." Furthermore, the positional relationship in the up-down direction may be specified by defining a direction perpendicular to the central axis O1, from the central axis O1 toward the upper surface 11 as "upward," and a direction from the upper surface 11 toward the central axis O1 as "downward."

[0018] The tip cutting edge 15 may be located at the intersection of the tip surface 9 and the top surface 11. The tip cutting edge 15 may be located at the entire intersection, or may be located only at a portion of the intersection. For example, as shown in a non-limiting example in FIG. 2, the tip cutting edge 15 may be located at the entire intersection. The tip cutting edge 15 can be used to cut a workpiece when manufacturing a machined product using the insert 1. The tip cutting edge 15 may also be generally referred to as a leading cutting edge or a main cutting edge.

[0019] The tip cutting edge 15 may have a straight or curved shape when viewed from the tip or from above. The tip cutting edge 15 may also have a shape that combines a straight line and a curved line when viewed from the tip or from above. For example, as in a non-limiting example shown in FIG. 7, the tip cutting edge 15 may have a straight line shape when viewed from the tip. Also, as in a non-limiting example shown in FIG. 4, the tip cutting edge 15 may have a straight line shape when viewed from above.

[0020] The term "tip view" may refer to a state viewed from the side of the tip 1a. The term "top view" may refer to a state viewed from the side of the top surface 11. In other words, the term "top view" may refer to a state where the top surface 11 is viewed from the front.

[0021] 2 and 4 , the upper surface 11 may have a pair of first breaker protrusions 17 and a pair of second breaker protrusions 19. The pair of first breaker protrusions 17 may each extend from the side of the main body 3 toward the tip surface 9. The pair of second breaker protrusions 19 may each extend from the first breaker protrusions 17 toward the tip surface 9.

[0022] The pair of first breaker protrusions 17 may each have a front surface 21. The front surface 21 may be located on the side of the tip 1a. The front surface 21 may have a flat inclined region 23.

[0023] The pair of second breaker projections 19 may have a curved shape and extend from the front surfaces 21 of the pair of first breaker projections 17 toward the tip surfaces 9 .

[0024] In these cases, the insert 1 is highly versatile for various cutting conditions and workpiece materials. For example, when cutting soft materials such as aluminum, mild steel, or low-carbon steel, or when cutting at a low feed rate, chip control is difficult due to the tendency for chips to elongate. When cutting such materials, the pair of second breaker protrusions 19 brakes the chips and tends to stabilize the direction of chip movement. Furthermore, the front faces 21 of the pair of first breaker protrusions 17 further brake the chips and tend to stably curl them.

[0025] When cutting hard materials or when cutting at a large feed rate, chip control is difficult because chips are difficult to deform. For example, forcibly deforming chips at a position too close to the tip face 9 may cause chip clogging. When cutting such materials, the curved shape of the pair of second breaker protrusions 19 makes it easier for chips to climb over the pair of second breaker protrusions 19. This prevents chips from curling at a position too close to the tip face 9. As a result, chip clogging is less likely to occur.

[0026] Furthermore, since the front surface 21 has the flat inclined region 23, chips that are difficult to deform can easily come into surface contact with the inclined region 23. This allows the chips to be braked and the chips to be easily curled stably. Therefore, the insert 1 is highly versatile in terms of cutting conditions and types of workpiece materials.

[0027] The entire front surface 21 may be configured with the inclined region 23. The inclined region 23 may be a flat region that slopes upward as it approaches the main body portion 3. The flatness of the inclined region 23 does not necessarily mean flat in the strict sense. The inclined region 23 may be generally flat, and may be slightly curved or have slight irregularities that are not noticeable when the insert 1 is viewed as a whole. For example, the inclined region 23 may have slight irregularities of about several tens of μm.

[0028] The curved surface shape of the second breaker projection 19 may be rephrased as a convex curved surface shape. The second breaker projection 19 may be connected to the first breaker projection 17.

[0029] The pair of first breaker protrusions 17 may be connected on the side of the main body 3. As shown in a non-limiting example in Fig. 4 , when viewed from above, the pair of first breaker protrusions 17 and the pair of second breaker protrusions 19 may be symmetrical with respect to the perpendicular bisector of the cutting edge 15. The perpendicular bisector of the cutting edge 15 may coincide with the central axis O1 when viewed from above.

[0030] 2 and 4, the second breaker projection 19 may be connected to the tip cutting edge 15. In this case, the effect of controlling the direction of chip advance at the second breaker projection 19, in other words, the effect of guiding the chip, is enhanced.

[0031] As a non-limiting example shown in Figure 10, the inclined region 23 may be parallel to the cutting edge 15 in a cross section perpendicular to the central axis O1. The cross section may be perpendicular to the central axis O1 and pass through the inclined region 23. A virtual line L15 of the cutting edge 15 projected onto this cross section may be regarded as the cutting edge 15. In other words, the virtual line L15 obtained by translating the cutting edge 15 until it intersects with the cross section may be regarded as the cutting edge 15. Furthermore, "parallel" is not limited to being strictly parallel, and may mean that an inclination of about ±5° is allowed.

[0032] In the above cross section, when the inclined region 23 is parallel to the cutting edge 15 (virtual line L15), the chips tend to flow in a direction perpendicular to the virtual line L15, making it easier for the chips to come into stable surface contact with the inclined region 23, allowing for stable chip discharge.

[0033] 6 and 7, the inclined region 23 may be located above the second breaker projection 19. In this case, the effect of braking chips in the inclined region 23 is enhanced.

[0034] The width W23 of the inclined region 23 in the direction along the tip cutting edge 15 may be gradually narrowed upward, as in a non-limiting example shown in Figure 7. In this case, chips tend to curl stably.

[0035] The inclined region 23 may have a triangular shape when viewed from the tip, as shown in a non-limiting example in Fig. 7. The shape of the inclined region 23 is not limited to the illustrated shape. The inclined region 23 may have a trapezoidal shape when viewed from the tip, for example.

[0036] 6, the inclined region 23 may have a linear shape when viewed from the side of the first side surface 13. The side view from the side of the first side surface 13 may refer to a state when viewed from the side of the first side surface 13.

[0037] 2, the upper surface 11 may further have an inclined surface 25. The inclined surface 25 may be located closer to the main body 3 than the pair of first breaker protrusions 17. The inclined surface 25 may be a surface that slopes upward as it approaches the main body 3.

[0038] As shown in a non-limiting example in Figure 6, the inclination angle θ23 of the inclined region 23 may be larger than the inclination angle θ25 of the inclined surface 25. Generally, the holder is located rearward relative to the insert 1. When the inclination angle θ23 of the inclined region 23 is configured as described above, chips are less likely to advance toward the holder located rearward relative to the insert 1. Therefore, damage to the holder by chips is more likely to be avoided.

[0039] The inclination angle θ23 of the inclined region 23 and the inclination angle θ25 of the inclined surface 25 may each be an inclination angle with respect to the central axis O1. When evaluating the inclination angle, a virtual line O1a parallel to the central axis O1 may be used as a reference. If the inclined region 23 has a linear shape when viewed from the side of the first side surface 13, the inclination angle θ23 may be evaluated using a virtual line L23 along the inclined region 23. The same applies to the inclined surface 25.

[0040] The inclination angle is not limited to a specific value. For example, the inclination angle θ23 of the inclined region 23 may be set to 30 to 60 degrees. The inclination angle θ25 of the inclined surface 25 may be set to 25 to 55 degrees.

[0041] 2, 4, and 11, the upper surface 11 may further have a rake surface 27. The rake surface 27 may be located between the pair of first breaker protrusions 17 and the pair of second breaker protrusions 19. The rake surface 27 may be a surface that faces downward as it moves away from the tip cutting edge 15. The rake surface 27 can function as a portion through which chips flow during cutting.

[0042] 2 and 4, the lower end 27a of the rake face 27 may be located between the pair of first breaker projections 17. In this case, chips are less likely to come into contact with the lower end 27a of the rake face 27, which makes it easier to avoid excessive braking of the chips.

[0043] The lower end 27a may refer to the lowest portion of the rake face 27. The lower end 27a of the rake face 27 may be located between the front faces 21 of the pair of first breaker projections 17. The lower end 27a of the rake face 27 may be located between the inclined regions 23 of the pair of first breaker projections 17.

[0044] The pair of first breaker protrusions 17 may extend in a direction Y1 in which the distance between them narrows as they approach the leading edge 15. The pair of second breaker protrusions 19 may extend in a direction Y2 in which the distance between them widens as they approach the leading edge 15. These configurations may be evaluated in a cross section parallel to the central axis O1 and the leading edge 15, as in the non-limiting example shown in Figure 15.

[0045] When the pair of first breaker protrusions 17 extend in the direction Y1 in which the distance between them narrows as they approach the tip cutting edge 15, it is easy to stably curl chips that have advanced between the pair of first breaker protrusions 17. When the pair of second breaker protrusions 19 extend in the direction Y2 in which the distance between them widens as they approach the tip cutting edge 15, it is easy to avoid a situation in which excessive braking is applied to chips that have advanced between the pair of first breaker protrusions 17.

[0046] The cutting portion 5 may further have a first side edge 29, as shown in Figures 2 and 4 as a non-limiting example. The first side edge 29 may be located at the intersection of the first side surface 13 and the top surface 11. The first side edge 29 may be located over the entire intersection, or may be located over only a portion of the intersection. The first side edge 29 can be used to increase the smoothness of the inner surface of a groove when manufacturing a machined product using the insert 1, or to widen the groove width during grooving.

[0047] The first side blade 29 may have a linear or curved shape when viewed from the side or top of the first side surface 13. The first side blade 29 may also have a shape that combines linear and curved lines when viewed from the side or top of the first side surface 13. For example, as shown in a non-limiting example in FIG. 6 , the first side blade 29 may have a linear shape when viewed from the side of the first side surface 13. The first side blade 29 may also be parallel to the central axis O1 when viewed from the side of the first side surface 13. However, as described above, the term "parallel" in this disclosure does not necessarily mean a strict parallel configuration, and may allow for an error (inclination) of approximately ±5°. For example, even if the first side blade 29 is slightly inclined by approximately ±5° with respect to the central axis O1, the first side blade 29 may be considered parallel to the central axis O1. As shown in a non-limiting example in FIG. 4 , the first side blade 29 may have a linear shape when viewed from the top.

[0048] 6 , the inclined region 23 may be located above the first side blade 29 when viewed from the side of the first side surface 13. In this case, chips are less likely to climb up onto the inclined region 23, and the chips tend to curl stably in the inclined region 23.

[0049] The cutting portion 5 may further include a first corner cutting edge 31 located at the corner where the tip cutting edge 15 and the first side cutting edge 29 intersect. The first corner cutting edge 31 may have a convex curved shape when viewed from above, as shown in a non-limiting example in Figure 4.

[0050] As a non-limiting example shown in Figures 2 and 4, the cutting portion 5 may further have a second side surface 33 located on the opposite side of the first side surface 13 and adjacent to the tip surface 9 and the top surface 11, a second horizontal blade 35 located at the intersection of the second side surface 33 and the top surface 11, and a second corner blade 37 located at the corner where the tip blade 15 and the second horizontal blade 35 intersect.

[0051] The second side surface 33 may have the same configuration as the first side surface 13. Furthermore, the second side blade 35 may have the same configuration as the first side blade 29. The second corner blade 37 may have the same configuration as the first corner blade 31. Therefore, the descriptions regarding the first side surface 13, the first side blade 29, and the first corner blade 31 may be used to understand the configurations of the second side surface 33, the second side blade 35, and the second corner blade 37, respectively.

[0052] The insert 1 is not limited to a specific size. For example, the length of the insert 1 in the direction along the central axis O1 may be set to approximately 10 to 40 mm. Furthermore, the width of the insert 1 in the direction perpendicular to the central axis O1 when viewed from above may be set to approximately 2 to 12 mm. The height of the insert 1 in the direction perpendicular to the central axis O1 when viewed from the tip may be set to approximately 2 to 10 mm.

[0053] Examples of the material of the insert 1 include cemented carbide and cermet. Examples of the cemented carbide composition include WC-Co, WC-TiC-Co, and WC-TiC-TaC-Co. Here, WC, TiC, and TaC may be hard particles, and Co may be a binder phase.

[0054] The cermet may be a sintered composite material in which a ceramic component is combined with a metal. An example of the cermet is a titanium compound mainly composed of titanium carbide (TiC) or titanium nitride (TiN). It goes without saying that the material of the insert 1 is not limited to the above composition.

[0055] The surface of the insert 1 may be coated with a coating using a chemical vapor deposition (CVD) method or a physical vapor deposition (PVD) method, and the composition of the coating may include, for example, titanium carbide (TiC), titanium nitride (TiN), titanium carbonitride (TiCN), and alumina (Al2O3).

[0056] <Cutting Tool> Next, a non-limiting one-sided cutting tool 101 of the present disclosure will be described with reference to the drawings.

[0057] The cutting tool 101 may have a holder 103 and an insert 1, as in a non-limiting example shown in Fig. 16. When the cutting tool 101 has the insert 1, the insert 1 has excellent versatility for cutting conditions and types of workpiece materials, and therefore, it is possible to exhibit high cutting performance.

[0058] The holder 103 may extend from the first end 103a toward the second end 103b. The extending direction of the holder 103 may coincide with the extending direction of the central axis O1 of the insert 1. The holder 103 may also be rod-shaped extending from the first end 103a toward the second end 103b. The holder 103 may also be shaped like a prism. The holder 103 may also be shaped like a square prism.

[0059] The holder 103 may have a pocket 105. The pocket 105 may be located on the side of the first end 103a. The insert 1 can be attached to the pocket 105.

[0060] The holder 103 may have an upper jaw 107 and a lower jaw 109 located on the side of the first end 103 a and spaced apart from each other, and the upper jaw 107 and the lower jaw 109 may form a pocket 105 .

[0061] The insert 1 may be located within the pocket 105. If the holder 103 has an upper jaw 107 and a lower jaw 109, the insert 1 may be sandwiched between the upper jaw 107 and the lower jaw 109.

[0062] The insert 1 may be positioned in the pocket 105 so that at least a part of the portion used as a cutting edge protrudes outward from the side of the first end 103 a of the holder 103. For example, the insert 1 may be positioned in the pocket 105 so that the cutting edge 15 protrudes outward from the side of the first end 103 a of the holder 103.

[0063] The insert 1 may be attached to the pocket 105 by a screw 111. For example, the insert 1 may be attached to the pocket 105 by inserting the screw 111 into the screw holes of the upper jaw 107 and the lower jaw 109 and fastening the screw 111 to the screw holes.

[0064] Examples of materials for the holder 103 include steel and cast iron. When the material for the holder 103 is steel, the holder 103 has high toughness.

[0065] <Method for Manufacturing Machined Product> Next, a non-limiting method for manufacturing the machined product 201 having one surface according to the present disclosure will be described with reference to the drawings.

[0066] The machined product 201 may be produced by cutting a workpiece 203. A manufacturing method for the machined product 201 may include the following steps: (1) a step of rotating the workpiece 203; (2) a step of bringing the cutting tool 101, which is typified by the non-limiting embodiment described above, into contact with the rotating workpiece 203; and (3) a step of separating the cutting tool 101 from the workpiece 203.

[0067] Specifically, first, as in a non-limiting example shown in Fig. 17 , the workpiece 203 may be rotated around the axis O2, and the cutting tool 101 may be brought relatively close to the workpiece 203. Next, as in a non-limiting example shown in Fig. 18 , the cutting edge 15 of the cutting tool 101 may be brought into contact with the workpiece 203 to cut the workpiece 203. Then, as in a non-limiting example shown in Fig. 19 , the cutting tool 101 may be moved relatively away from the workpiece 203.

[0068] By going through the above process, the cutting tool 101 has an insert 1 that is highly versatile for cutting conditions and the material type of the workpiece 203, making it possible to obtain a machined product 201 with a highly accurate finished surface.

[0069] In the non-limiting example shown in FIGS. 17 to 19, the workpiece 203 is fixed and the cutting tool 101 is moved in each step, but the present invention is not limited to this configuration.

[0070] For example, in step (1), the workpiece 203 may be brought closer to the cutting tool 101. Also, in step (3), the workpiece 203 may be moved away from the cutting tool 101. When continuing the cutting process, the workpiece 203 may be kept rotating, and the step of bringing the cutting tool 101 into contact with different locations of the workpiece 203 may be repeated.

[0071] Examples of the material of the workpiece 203 include titanium alloys, aluminum, mild steel, carbon steel (high carbon steel and low carbon steel), alloy steel, stainless steel, cast iron, and non-ferrous metals.

[0072] The above provides examples of the non-limiting one-sided cutting insert 1, cutting tool 101, and method for manufacturing the machined product 201 of the present disclosure, but it goes without saying that the present disclosure is not limited to the above embodiments and can be any as long as it does not deviate from the gist of the present disclosure.

[0073] For example, the cutting insert 1, the cutting tool 101, and the manufacturing method of the machined product 201 may be configured as follows: [1] The cutting insert is rod-shaped extending from a tip end to a rear end along a central axis, and has a main body and a cutting portion located closer to the tip end than the main body, the cutting portion having a tip surface located closer to the tip end, an upper surface extending from the tip surface toward the main body, a first side surface adjacent to the tip surface and the upper surface, and a tip cutting edge located at an intersection of the tip surface and the upper surface, the upper surface having a pair of first breaker protrusions each extending from the main body side toward the tip surface and a pair of second breaker protrusions each extending from the first breaker protrusions toward the tip surface, the pair of first breaker protrusions each having a front surface located closer to the tip end and having a flat inclined region, the pair of second breaker protrusions each having a curved surface and extending from the front surface of the pair of first breaker protrusions toward the tip surface. [2] In the cutting insert of [1] above, the second breaker protrusion may be connected to the leading edge. [3] In the cutting insert of [1] or [2] above, the inclined region may be parallel to the leading edge in a cross section perpendicular to the central axis. [4] In any one of the cutting inserts of [1] to [3] above, the inclined region may be located above the second breaker protrusion. [5] In any one of the cutting inserts of [1] to [4] above, the width of the inclined region in a direction along the leading edge may narrow upward. [6] In any one of the cutting inserts of [1] to [5] above, the upper surface may be located closer to the main body portion than the pair of first breaker protrusions and may further have an inclined surface that inclines upward as it approaches the main body portion, and the inclination angle of the inclined region may be greater than the inclination angle of the inclined surface. [7] The cutting insert according to any one of [1] to [6] above may further have a cutting surface, the upper surface of which is located between the pair of first breaker protrusions and the pair of second breaker protrusions, and which faces downward as it moves away from the tip cutting edge, and the lower end of the cutting surface may be located between the pair of first breaker protrusions.[8] In the cutting insert of any one of [1] to [7] above, the pair of first breaker protrusions may extend in a direction that narrows the gap between them as they approach the leading edge, and the pair of second breaker protrusions may extend in a direction that widens the gap between them as they approach the leading edge. [9] A cutting tool may have a holder extending from a first end to a second end and having a pocket located on the side of the first end, and a cutting insert of any one of [1] to [8] above located in the pocket.

[10] A method for manufacturing a machined product may include a step of rotating a workpiece, a step of bringing the cutting tool of [9] above into contact with the rotating workpiece, and a step of separating the cutting tool from the workpiece.

[0074] DESCRIPTION OF SYMBOLS 1...Cutting insert (insert) 1a...Tip 1b...Rear end 3...Main body 5...Cutting portion (first cutting portion) 7...Cutting portion (second cutting portion) 9...Tip surface 11...Top surface 13...First side surface 15...Tip cutting edge 17...First breaker protrusion 19...Second breaker protrusion 21...Front surface 23...Inclined region 25...Inclined surface 27...Cutting face 27a...Bottom end 29...First side cutting edge 31...First corner cutting edge 33...Second side surface 35...Second side cutting edge 37...Second corner cutting edge 101...Cutting tool 103...Holder 103a...First end 103b...Second end 105...Pocket 107...Upper jaw 109...Lower jaw 111...Screw 201...Cutting workpiece 203...Workpiece O1...center axis O2...axis

Claims

1. A cutting insert having a rod shape extending along a central axis from a tip to a rear end, comprising: a main body portion; and a cutting portion located on the tip side of the main body portion, wherein the cutting portion has: a tip surface located on the tip side, an upper surface extending from the tip surface towards the main body portion, a first side surface adjacent to the tip surface and the upper surface, and a tip cutting edge located at the intersection of the tip surface and the upper surface, wherein the upper surface has a pair of first breaker protrusions each extending from the side of the main body portion towards the tip surface, and a pair of second breaker protrusions each extending from the first breaker protrusions towards the tip surface, wherein the pair of first breaker protrusions each have a front surface located on the tip side and having a flat inclined region, and the pair of second breaker protrusions are curved in shape and each extend from the front surface of the pair of first breaker protrusions towards the tip surface.

2. The cutting insert according to claim 1, wherein the second breaker projection is connected to the tip edge.

3. The cutting insert according to claim 1 or 2, wherein the inclined region is parallel to the tip edge in a cross section perpendicular to the central axis.

4. The cutting insert according to any one of claims 1 to 3, wherein the inclined region is located above the second breaker protrusion.

5. A cutting insert according to any one of claims 1 to 4, wherein the width of the inclined region in a direction along the tip edge narrows toward the top.

6. A cutting insert according to any one of claims 1 to 5, wherein the upper surface is located closer to the main body portion than the pair of first breaker protrusions and further has an inclined surface that slopes upward as it approaches the main body portion, and the inclination angle of the inclined area is greater than the inclination angle of the inclined surface.

7. A cutting insert according to any one of claims 1 to 6, wherein the upper surface is located between the pair of first breaker projections and the pair of second breaker projections, and further has a cutting surface that faces downward as it moves away from the tip cutting edge, and a lower end of the cutting surface is located between the pair of first breaker projections.

8. A cutting insert according to any one of claims 1 to 7, wherein the pair of first breaker projections extend in a direction in which the distance between them becomes narrower as they approach the leading edges, and the pair of second breaker projections extend in a direction in which the distance between them becomes wider as they approach the leading edges.

9. A cutting tool comprising: a holder extending from a first end toward a second end and having a pocket located on the side of the first end; and a cutting insert according to any one of claims 1 to 8 located in the pocket.

10. A method for manufacturing a machined product, comprising the steps of: rotating a workpiece; bringing a cutting tool according to claim 9 into contact with the rotating workpiece; and removing the cutting tool from the workpiece.

Images