Cutting insert, cutting tool, and method of manufacturing machined product

A cutting insert according to one aspect of the present invention includes a polygonal columnar shape, and includes an upper surface, a lower surface and a side surface located between the upper surface and the lower surface, and a cutting edge is formed at an intersecting portion between the upper surface and the side surface, the upper surface includes a main portion of a convex shape including a flat upper end surface, a first projecting portion which projects from the main portion to a corner portion of the upper surface, and a pair of second projecting portions which each project from the first projecting portion to a periphery of the upper surface to interpose a region between a front end of the first projecting portion and the corner portion, and each of upper ends of the pair of second projecting portions is spaced part from the first projecting portion.

TECHNICAL FIELD

The present invention relates to a cutting insert, a cutting tool, and a method of manufacturing a machined product.

BACKGROUND ART

Conventionally, a throw-away cutting tool with a cutting insert attached to a holder is used for a cutting tool for use in cutting process. Such a cutting insert used for this cutting tool is generally configured to include an upper surface, a lower surface and a side surface, and a cutting edge is formed at an intersecting portion between the upper surface and the side surface. By bringing the cutting edge into contact with a rotating workpiece such as a metal member, it is possible to cut a workpiece.

A configuration of a cutting insert is proposed such that projections to be in contact with chips of a workpiece are provided on an upper surface thereof in the same manner as cutting chips disclosed in Patent Document 1. The cutting insert disclosed in Patent Document 1 can curve a chip by placing the chip of a workpiece in contact with a first projection (first ridge) and a second projection (second ridge) extending from the first projection.

The cutting insert disclosed in Patent Document 1 first contacts with the chip in the second projection upon high depth cut process. Further, after getting on the second projection, the chip contacts the first projection. At this time, an upper end of the second projection is positioned in contact with the first projection. Thus, when moving from the top of the second projection to the top of the first projection, the chip smoothly moves. Therefore, curving the chip in an adequate shape is likely to be difficult. In such a case, it is likely that the chip is insufficiently curved and the chip becomes long more than necessary.

SUMMARY OF THE INVENTION

A cutting insert according to one aspect of the present invention includes a polygonal columnar shape, and includes an upper surface, a lower surface and a side surface located between the upper surface and the lower surface, and a cutting edge is formed at an intersecting portion between the upper surface and the side surface. The upper surface includes a main portion which is made convex upward, a first projecting portion which projects from the main portion to a corner portion of the upper surface, and a pair of second projecting portions which each project from the first projecting portion to a periphery of the upper surface to interpose a region between a front end of the first projecting portion and the corner portion. Further, in the cutting insert according to the above aspect, each of upper ends of the pair of second projecting portions is spaced apart from the first projecting portion.

PREFERRED EMBODIMENTS FOR CARRYING OUT THE INVENTION

A cutting insert according to one embodiment will be described in detail using the drawings below. Meanwhile, each drawing referred to below simplifies only main members required to explain the present invention among components according to the embodiment for ease of description. Hence, the cutting insert according to the present invention may have arbitrary components which are not shown in each drawing referred to in the present description. Further, the dimensions of the members in each drawing do not exactly reflect dimensions of actual components and dimension ratios and the like of each member.

As shown inFIGS. 1 to 9, a cutting insert1according to the present embodiment has an upper surface3and a lower surface5whose shapes are square shapes when seen from a plan view and, more specifically, diamond shapes. More specifically, the top surface3and the lower surface5are not squares, strictly speaking. Each corner portion which is an intersection of each side which forms a square is a curved corner portion.

Further, four side surfaces7connected to the upper surface3and the lower surface5, respectively, are provided between the upper surface3and the lower surface5. The side surface7includes a flat portion which is positioned between each side of the upper surface3and the lower surface5forming a square, and a curved surface portion which is positioned between a curved portion of the upper surface3and the lower surface5. More specifically, the side surface7includes a flat first side surface7a, a corner side surface7bof a curved surface and a flat second side surface7c.

The upper surface3and the lower surface5have substantially same shapes which overlap each other when seen from a plan view. Hence, the four side surfaces7positioned between the upper surface3and the lower surface5are formed vertically with respect to the upper surface3and the lower surface5. These upper surface3, lower surface5and side surfaces7form the cutting insert1into a polygonal columnar shape, and, more specifically, a quadrangular prism shape.

Further, cutting edges9are formed at an intersecting portion between the upper surface3and the side surface7, and at an intersecting portion between the lower surface5and the side surface7. That is, the cutting insert1according to the present embodiment is a so-called negative-type cutting insert1which has the cutting edges9formed at the intersecting portion between the upper surface3and the side surface7and, in addition, the intersecting portion between the lower surface5and the side surface7. In addition, the cutting insert1may be a so-called positive-type cutting insert1which has the cutting edge9formed only at the intersecting portion between the upper surface3and the side surface7.

The cutting insert1according to the present embodiment is the negative-type, and the lower surface5of the cutting insert1according to the present embodiment employs the same configuration as that of the upper surface3which is not shown in particular. The negative-type cutting insert1can be vertically turned upside down and used.

That is, when the lower surface5of the cutting insert1is attached as a seating surface to a holder103, the cutting edge9formed at the intersecting portion between the upper surface3and the side surface7of the cutting insert1can be used for cutting process. Further, when the upper surface3of the cutting insert1is attached as a seating surface to the holder103by turning the cutting insert1upside down, the cutting edge9formed at the intersecting portion between the lower surface5and the side surface7of the cutting insert1can be used for cutting process.

As to the cutting edge9, a first cutting edge9ais formed at an intersecting portion between the upper surface3and the first side surface7a, a corner cutting edge9bis formed at an intersecting portion between the upper surface3and the corner side surface7b, and a second cutting edge9cis formed at an intersecting portion between the upper surface3and the second side surface7c.

A height of the cutting edge9from the lower surface5may be fixed. However, the cutting edge9according to the present embodiment is configured such that portions of the first cutting edge9aand the second cutting edge9cadjacent to the corner cutting edge9bare inclined toward the lower surface as being apart from a corner portion27. The portions of the first cutting edge9aand the second cutting edge9cadjacent to the corner cutting edge9bare used for high depth cut. However, this configuration can reduce a cutting resistance at this portion.

A longitudinal direction width of the upper surface3of the diamond shape in the cutting insert1according to the present embodiment is set to, for example, about 15 to 25 mm. Further, a width in a direction vertical to the longitudinal direction is set to about 10 to 22 mm. The size of the lower surface5of the diamond shape is set according to the size of the above upper surface3. The thickness of the cutting insert1is set to, for example, 3 to 7 mm.

In this regard, the thickness means a vertical direction width from a portion at the uppermost position of the upper surface3to a portion at the lowermost position of the lower surface5when the cutting insert1is seen from the side view. At, for example, an upper end of the upper surface3and a lower end of the lower surface5in the cutting insert1according to the present embodiment, flat surfaces which are seating surfaces to which the holder103is attached are formed. Vertical direction widths of these flat surfaces are the thickness of the cutting insert1.

A material of the cutting insert1is, for example, cemented carbide or cermet. A composition of cemented carbide includes, for example, WC—Co produced by adding cobalt (Co) powders to tungsten carbide (WC) and sintering the resultant material, WC—TiC—Co produced by doping WC—Co with titanium carbide (TiC) and WC—TiC—TaC—Co produced by doping WC—TiC—Co with tantalum carbide (TaC). Further, cermet is a sintered composite material produced by mixing metal in ceramic components, and more specifically, titanium compounds whose main component is titanium carbide (TiC) or titanium nitride (TiN).

The surface of the cutting insert1may be coated by a coating using a chemical vapor deposition (CVD) method or a physical vapor deposition (PVD) method. A composition of the coating includes, for example, titanium carbide (TiC), titanium nitride (TiN), titanium carbonitride (TiCN), alumina (Al2O3) and the like.

The upper surface3of the cutting insert1according to the present embodiment includes a main portion11, a land portion13and breaker groove15. The main portion11has a shape which is made convex upward, and is positioned so as to surround a through hole17as described below. The land portion13is formed at a periphery of the upper surface3so as to surround the main portion11. That is, the cutting edge9is formed at the intersecting portion between the land portion13and the side surface7.

Further, the breaker groove15is formed between the main portion11and the land portion13. Heights of the main portion11and the land portion13from the lower surface5are positioned higher than heights of bottom surface of the breaker groove15from the lower surface5. Further, the height of the main portion11from the lower surface5is higher than the height of the land portion13from the lower surface5.

A rake angle of a region of the breaker groove15along the cutting edge9is maximum near the corner portion27for the purpose of raking a chip in a high depth cut region and curing the chip, and for the purpose of reducing a cutting resistance. Further, an angle is relatively small compared to the angle of the above portion to maintain strengths of a portion corresponding to the corner portion27and a portion apart from the corner portion27.

In addition, the above “height from the lower surface5” means a vertical direction width from this flat surface when the lower surface5is the flat surface. Further, when the lower surface5includes concavities and convexities as in the cutting insert1according to the present embodiment, the “height from the lower surface5” means a vertical direction width from the flat lower end surface which functions as the seating surface to which the holder103is to be attached.

Furthermore, the upper surface3includes first projecting portion19which projects from the main portion11toward the corner portions27of the upper surface3, and pairs of second projecting portions21and23which each project from the first projecting portion19to the periphery of the upper surface3. The heights of the first projecting19and the second projecting portions21and23from the lower surface5are lower than the height of the main portion11from the lower surface5. A pair of second projecting portions21and23are located so as to interpose at least a front end portion19a(also referred to simply as a front end portion19a) of the first projecting portion19, and a region between the front end of the first projecting portion19and the corner portion27.

The cutting insert1includes these second projecting portions21and23, and, when low depth cut and high feed process are performed, a pair of second projecting portions21and23process a chip. Consequently, it is possible to reduce clogging of the chip upon high feed process, and to control the chip without an increase in cutting resistance.

Further, a first feature of the cutting insert1according to the present embodiment is that a pair of the second projecting portions21and23do not simply project from the first projecting portion19toward the periphery of the upper surface3, but the upper ends of the pair of the second projecting portions21and23are apart from the first projecting portion19. That is, a concave portion25which is a recess is formed at a boundary between the first projecting potion19and the second projecting portions21and23. More specifically, the concave portion25which is opened upward and in a direction orthogonal to a direction in which the second projecting portions21and23project is formed between the first projecting portion19and the second projecting portions21and23.

Thus, the recess is formed between the first projecting portion19and the second projecting portions21and23. Consequently, similar to, for example, high depth cut processing, a chip which gets on the second projecting portions21and23is raked into this recess and contacts the first projecting portion19and, consequently, the chip can be easily curved. Consequently, the chip is easily cut; as a result, the chip does not become excessively long. Therefore it is possible to eject the chip well.

The through hole17which penetrates from the center of the upper surface3to the center of the lower surface5is formed in the cutting insert1according to the present embodiment. The through hole17is provided to allow insertion of a bolt105to screw and fix the cutting insert1to the holder103of the cutting tool101. In addition, a clamp structure may be adopted for a method of fixing the cutting insert1to the holder103instead of the above screwing and fixing method.

An upper end surface of the main portion11is a flat surface. When the upper surface3of the cutting insert1is attached as the seating surface to the holder103by turning the cutting insert1upside down, the upper end surface of the main portion11functions as the seating surface. The first projecting portion19projects from the main portion11to the corner portion27of the upper surface3. A pair of second projecting portions21and23are located to interpose a region between the front end of the first projecting portion19and the corner portion27.

In the cutting insert1according to the present embodiment, a pair of second projecting portions21and23are located to interpose a line connecting the front end of the first projecting portion19and the corner portion27. A pair of second projecting portions21and23are located axisymmetric with respect to the above line as a center axis. The first projecting portion19and the second projecting portions21and23function as so-called breakers for chips.

The upper ends of a pair of the second projecting portions21and23can be configured to be positioned at the same height as that of the upper end of the first projecting portion19. The height of the upper end of the first projecting portion19, more specifically, the height from the lower surface5, and the heights of the upper ends of the second projecting portions21and23are substantially the same. Consequently, it is possible to stably curve chips.

Further, when a chip contacts one of the second projecting portions21and23and moves toward a rear end portion19bof the first projecting portion19, it is possible to smoothly place the chip in contact with the rear end portion19b. When the chip strongly contacts the rear end portion19bof the first projecting portion19, the chip is likely to be clogged at the rear end portion19bas the starting point. When the chip is clogged at the rear end portion19bas the starting point, the chip strongly contacts not only the rear end portion19bof the first projecting portion19but also a front end portion19a, the front end portion19ais likely to be damaged. However, by smoothly placing the chip in contact with the rear end portion19b, it is possible to reduce the likelihood that the chip strongly contacts the front end portion19a. As a result, it is possible to reduce the likelihood that the front end portion19ais damaged.

Meanwhile, when a chip contacts side surface of the first projecting portion19and the second projecting portions21and23upon high depth cut and low feed process, the upper end of the first projecting portion19and the upper ends of the second projecting portions21and23have the same heights. Consequently, it is possible to minimize variations of curves of chips at the first projecting portion19and the second projecting portions21and23. Consequently, it is possible to stably curve chips.

In the cutting insert1according to the present embodiment, the front end surface19aof the first projecting portion19has a flat surface shape inclined with respect to the lower surface5, and a front end surface11aof the main portion11has a concave curved surface shape inclined with respect to the lower surface5. Upon low depth cut and low feed process, a chip contacts the side surfaces of the second projecting portions21and23and, in addition, the front end surface of the first projecting portion19. The front end of the first projecting portion19is a flat inclined surface to stably curve chips whose thicknesses are relatively small and which are likely to deform.

Further, a chip contacts the front end surface of the main portion11upon high feed process. Upon high feed process, the chip thickness is relatively large. In such a case, the front end of the main portion11is a concave inclined surface as shown inFIG. 5to reduce a likelihood that the front end surface of the main portion11deforms, and to stably curve the chip.

When cutting process is performed using the cutting insert1according to the present embodiment and when, for example, low depth cut process is performed, a portion of the corner cutting edge9bnear the first cutting edge9aor a portion of the corner cutting edge9bnear the second cutting edge9cis mainly used. Which one of the portion of the corner cutting edge9bnear the first cutting edge9aor the portion of the corner cutting edge9bnear the second cutting edge9cis used is determined according to a direction in which a workpiece201is placed in contact.

When the workpiece201is placed in contact with the cutting insert1from a side of the first side surface7a(the right sides inFIGS. 5 to 7), the portion of the corner cutting edge9bnear the first cutting edge9ais used for cutting process. Further, when the workpiece201is placed in contact with the cutting insert1from a side of the second side surface7c(the left sides inFIGS. 5 to 7), the portion of the corner cutting edge9bnear the second cutting edge9cis used for cutting process.

When the portion of the corner cutting edge9bnear the first cutting edge9ais mainly used for cutting process, a chip of the workpiece cut at this portion is placed in contact with the second projecting portion23which is relatively apart from the first cutting edge9aamong the second projecting portions21and23, and is thereby deformed and cut.

A second feature of the cutting insert1according to the present embodiment is that the second projecting portion21projects toward the boundary between the first cutting edge9aand the corner cutting edge9b, the second projecting portion23projects toward the boundary between the second cutting edge9cand the corner cutting edge9b, and the height of the front end portion19ais lower than the heights of the upper surfaces of the second projecting portions21and23.

That is, in the cutting insert1according to the present embodiment, the second projecting portions21and23are not simply arranged symmetrically on a corner bisector but the second projecting portion21projects toward the boundary between the first cutting edge9aand the corner cutting edge9band the second projecting portion23projects toward the second cutting edge9cand the corner cutting edge9b.

When the second projecting portion23does not project toward the above boundary but the second projecting portion23projects closer to the corner portion of the upper surface3than the boundary between the second cutting edge9cand the corner cutting edge9b, that is, projects toward the corner cutting edge9b, it is possible to narrow the interval between the second projecting portion23and the first cutting edge9a. However, in such a case, the angle formed between the direction in which the second projecting portion23projects and the first cutting edges9ais large. Therefore, it is difficult to place a chip in contact with the second projecting portion23and to curve the chip well, and performance to cut chips lowers.

Meanwhile, in the cutting insert1according to the present embodiment, the second projecting portion23projects toward the above boundary. Consequently, the angle formed between the direction in which the second projecting portion23projects and the first cutting edge9abecomes small, so that it is possible to cut chips well. More specifically, the second projecting portion23projects toward the above boundary, and the second projecting portion23is arranged in a state substantially vertical to a feeding direction of the cutting tool or to a rotation axis of a workpiece. Consequently, it is possible to cut chips well.

In addition, in the cutting insert1according to the present embodiment, that “the second projecting portion21projects toward the boundary between the first cutting edge9aand the corner cutting edge9b” means that a line which is parallel to a line X1 connecting the front end and the rear end of the second projecting portion21and which passes at least part of the second projecting portion21is located on the boundary between the first cutting edge9aand the corner cutting edge9b. More specifically, as shown inFIG. 6, the boundary between the first cutting edge9aand the corner cutting edge9bis located between two dashed-two dotted lines interposing the line X1. Hence, the line connecting the front end and the rear end of the second projecting portion21is not strictly limited to the line positioned on the above boundary.

Further, the second projecting portions21and23are located so as to interpose at least the front end portion19aof the first projecting portion19. In other words, the front end portion19aof the first projecting portion19projects toward the corner cutting edge9bbetween the second projecting portions21and23.

Consequently, even when a corner curvature radius is increased, it is possible to first place a chip of a workpiece cut at the portion of the corner cutting edge9bnear the first cutting edge9a, in contact with the front end portion19aof the first projecting portion19. More specifically, the front end portion19aof the first projecting portion19is located closer to the first cutting edge9athan the second projecting portion23. Consequently, it is possible to place a chip in contact with the front end portion19aof the first projecting portion19upon cutting process by way of low feed.

In addition, the height of the front end portion19ais lower than the heights of the upper surfaces of the second projecting portions21and23and, when a feeding amount is increased, the chip gets over the front end portion19a. In such a case, the chip contacts the second projecting portion23. Consequently, even when the feeding amount is great, it is possible to stably deform chips. As described above, even when the corner curvature radius is increased, the cutting insert1according to the present embodiment can perform cutting process well upon low feed process and high feed process.

In addition, the height of the front end portion19aand the heights of the upper surfaces of the second projecting portions21and23can be evaluated by calculating “heights from the lower surface5” as described above. Further, the “upper surfaces” of the second projecting portions21and23mean the highest portions of the second projecting portions21and23from the lower surface5, and do not necessarily need to be flat surfaces. In other words, the height of the upper surface of the first projecting portion19at the portion interposed between the second projecting portions21and23is lower than the heights of the upper ends at the highest positions of the second projecting portions21and23.

The cutting insert1according to the present embodiment is suitably used for cutting process with a wide variety of feeding amounts upon low depth cut process of cutting the workpiece201in such a region of the corner cutting edge9b. In addition, the cutting insert1according to the present embodiment is suitably used upon low depth cut process. However, naturally, use of the cutting insert1upon high depth cut process is not disturbed.

Further, a case has been described above where the portion of the corner cutting edge9bnear the first cutting edge9ais mainly used for cutting process. However, when the portion of the corner cutting edge9bnear the second cutting edge9cis mainly used for cutting process, a role of the second projecting portion21and a role of the second projecting portion23are reversed.

The first projecting portion19includes the front end portion19ainterposed between the second projecting portions21and23, and a portion positioned closer to the rear end side than this front end portion19a. Hereinafter, this portion will be referred to as the rear end portion19bfor ease of description. The upper surface of the front end portion19ais a planar inclined surface. Further, the upper surface of the rear end portion19bis an inclined surface of a concave curved surface. The upper surfaces of the front end portion19aand the rear end portion19bare inclined surfaces whose heights become lower toward the corner cutting edge9b.

The front end portion19aof the first projecting portion19mainly functions when a chip is placed in contact with the front end portion19aupon low depth cut and low feed process and is deformed. The thickness of a chip is small upon low feed process, and, consequently, the chip is easily curved when contacting the front end portion19awhose upper surface is the planar inclined surface. Further, when the cutting amount is great and the feeding amount is also great, a chip is likely to get over the front end portion19aand contact the rear end portion19bof the first projecting portion19.

In such a case, the upper surface of the rear end portion19bis an inclined surface of a concave curved surface. Consequently, when a chip moves along this inclined surface, it is possible to increase a contact area between the chip and the rear end portion19b. Therefore, it is possible to stably put on a brake on the chips and, consequently, to efficiently cut the chips.

Further, in the cutting insert1according to the present embodiment, the width of the rear end portion19bof the first projecting portion19in a direction orthogonal to the direction in which the first projecting portion19projects gradually becomes narrower from the rear end side to the front end side. In addition, the width of the front end portion19aof the first projecting portion19in the direction orthogonal to the direction in which the first projecting portion19projects gradually becomes wider from the rear end side to the front end side. The front end side width of the front end portion19ais relatively wide and, consequently, it is possible to have chips stably get on the upper surface of the front end portion19aupon low depth cut process.

Further, the entire width of the front end portion19ais not wide but the rear end side width of the front end portion19ais relatively narrow. Consequently, it is possible to reduce an interval between the second projecting portions21and23so as not to become excessively large. That is, it is possible to reduce the interval between the first cutting edge9aand the second projecting portion23. Consequently, it is possible to reduce a distance which a chip cut by the corner cutting edge9btakes to contact the second projecting portion23so as not to become excessively longer. Consequently, it is possible to stably deform chips when the chips are placed in contact with the second projecting portions23.

The upper surface of the rear end portion19bof the first projecting portion19is a concave curved surface as described above. Hence, when a chip is placed in contact with the rear end portion19b, the chip is likely to apply a greater load to the rear end side than to the front end side of the upper surface of the rear end portion19b. However, the rear end side width of the rear end portion19bis relatively wide. Consequently, it is possible to increase a contact area with chips, on the rear end side of the rear end portion19bto which a relatively great load is likely to be applied. Consequently, it is possible to distribute the load applied to the first projecting portion19. As a result, it is possible to enhance durability of the rear end portion19bof the first projecting portion19.

Further, the entire width of the rear end portion19bis not wide but the front end side width of the rear end portion19bis relatively narrow. Consequently, it is possible to reduce an interval between the second projecting portions21and23so as not to become excessively large. Consequently, it is possible to stably deform chips when the chips are placed in contact with the second projecting portions23as described above.

Further, in the cutting insert1according to the present embodiment, the front end portions of the second portions21and23project more in a direction in which the first projecting portion19projects than the front end portion19aof the first projecting portion19. More specifically, as shown inFIG. 7, a line which is orthogonal to a direction in which the first projecting portion19projects and which is in contact with the front end of the first projecting portion19is a line X3. Further, a line which is orthogonal to the direction in which the first projecting portion19projects and which is in contact with the front ends of the second projecting portions21and23is a line X4.

In this case, the line X4 is parallel to the line X3, and the line X4 is located closer to the corner portion27in the direction in which the first projecting portion19projects than the line X3. Hence, a concave portion is formed in a region surrounded by the corner cutting edge9b, the projecting portion19and the second projecting portions21and23. The concave portion forms a part of the breaker groove15. When this concave portion is formed, a chip which is in contact with the second projecting portion23can be easily deformed in this concave portion.

In the cutting insert1according to the present embodiment, the second projecting portions21and23each linearly project. In this regard, that the second projecting portions21and23linearly project means that, in case of, for example, the second projecting portions23, each ridge connecting the front end and the rear end of the second projecting portion23is linearly formed. Consequently, the second projecting portion23does not need to have a linear shape, and may have an oval sphere or a droplet shape whose width at a center portion between the front end side and the rear end side is wide as shown inFIGS. 6 and 7.

The second projecting portions21and23in the cutting insert1according to the present embodiment has the upper surfaces which are convex curved surfaces and lower ends of the side surfaces which are concave curved surface. Consequently, an upper end side surface including the upper surface is shown as a convex curve in the cross section which is vertical to the lower surface5and includes the second projecting portion23, and the lower end side surface continuing to the breaker groove15is shown as a concave curve.

When the feeding amount is great, a chip gets over the front end portion19aof the first projecting portion19and contacts the surfaces of the second projecting portions21and23. However, even in such a case, it is possible to easily curl a chip which contacts the second projecting portions21and23through the surfaces which are lower end side concave curved surfaces continuing to the breaker groove15in the second projecting portion23.

Further, the upper surfaces of the second projecting portions21and23are convex curved surfaces, so that the feeding amount further increases and it is possible to have chips smoothly move from the second projecting portions21and23to the rear end portion19bof the first projecting portion19. Consequently, it is possible to stably deform the chips in the upper surface of the rear end portion19b.

Further, in the cutting insert1according to the present embodiment, the direction in which the second projecting portion23projects is nearly parallel to the second side surface7c. When the second projecting portion23is formed in this way, chips can be stably curved by the second projecting portion23upon process with the feeding amount at which the chips are placed in contact with the second projecting portion23. Consequently, the chips are easily cut to an adequate length; as a result, the chips do not become excessively long.

Further, the direction in which the second projecting portion21projects is nearly parallel to the first side surface7a. When the second projecting portion21is formed in this way, chip lengths can be easily controlled upon cutting process of placing chips in contact with the second projecting portion21by placing a workpiece in contact with the cutting insert1from a direction with the left and the right reversed. More specifically, chips can be stably curved by the second projecting portion21upon process with the feeding amount at which the chips are placed in contact with the second projecting portion21. Consequently, the chips are easily cut to an adequate length; as a result, the chips do not become excessively long.

Exemplary sizes of the first projecting portion19and the second projecting portions21and23are as follows. As shown inFIG. 5, the length of the rear end portion19bof the first projecting portion19indicated by the direction in which the first projecting portion19projects (the vertical direction inFIG. 5) can be set to 0.4 to 1 mm, and the width of the rear end portion19bindicated by the direction orthogonal to the above direction can be set to 0.3 to 0.6 mm.

Further, the length of the front end portion19aof the first projecting portion19indicated by the direction in which the first projecting portion19projects (the vertical direction inFIG. 5) can be set to 0.3 to 0.7 mm, and the width of the front end portion19aindicated by the direction orthogonal to the above direction can be set to 0.4 to 0.7 mm. Furthermore, the length of each second projecting portion21indicated by the direction in which the second projecting portion21projects can be set to 0.3 to 0.8 mm, and the width of the second projecting portion21indicated by the direction orthogonal to the above direction can be set to 0.3 to 0.6 mm. Still further, the length of each third projecting portion23indicated by the direction in which the third projecting portion23projects can be set to 0.3 to 0.8 mm, and the width of the third projecting portion23indicated by the direction orthogonal to the above direction can be set to 0.3 to 0.6 mm.

In addition, as shown inFIG. 2, the cutting insert1according to the present embodiment has the upper surface3whose shape is a square shape of a diamond shape when seen from a plan view and is not limited to this mode. For example, the shape of the upper surface3may be a polygonal shape such as a triangular shape, a pentagonal shape, a hexagonal shape or an octagonal shape when seen from a plan view.

Further, that the shape is a square shape when seen from a plan view does not demand a strict square shape. The main portions at the outer periphery of the upper surface3may be formed with four sides and the corner portion27may have partial curved shape.

Next, a cutting tool101according to an embodiment of the present invention will be described with reference to the drawings.

As shown inFIGS. 10 to 12, the cutting tool101according to the present embodiment has the cutting insert1represented in the above embodiment, and the holder103to which the cutting insert1is attached. The holder103according to the present embodiment has at one end portion a bar shape, and has an insert pocket to which the cutting insert1is attached. The cutting insert1is attached such that the cutting edge9projects outward compared to the outer periphery of the holder103.

In the present embodiment, the cutting insert1is fixed to the insert pocket by the bolt105. That is, by inserting the bolt105in the through hole17of the cutting insert1, inserting the front end of this bolt105in a screw hole (not shown) formed in the insert pocket and screwing screw portions, the cutting insert1is attached to the holder103.

Steel or cast iron can be used for the holder103. Particularly, touch steel among these members is preferably used.

<Method of Manufacturing Machined Product>

Next, the method of manufacturing a machined product by cutting the workpiece201according to one embodiment of the present invention will be described with reference to the drawings.

The manufacturing method according to the present embodiment has the following processes. That is, the manufacturing method includes,

as shown inFIG. 10, process (1) of placing the cutting tool101represented in the above embodiment relatively close to the workpiece201in a state where the workpiece201is rotated, as shown inFIG. 11, process (2) of placing at least the corner cutting edge13of the cutting edge9of the cutting tool101in contact with the rotating workpiece201, and,

as shown inFIG. 12, process (3) of separating the cutting tool101from the workpiece201.

According to the method of manufacturing the machined product according to the present embodiment, the cutting insert1has the first projecting portion19and the second projecting portions21and23employing the above characteristic configuration. Consequently, it is possible to support cutting process with a wide variety of feeding amounts.

In addition, inFIG. 10, the workpiece201is rotated in a state where the rotation axis is fixed, and the cutting tool101is placed close to the workpiece201. Further, inFIG. 11, in a state where the workpiece201is rotated, cutting process is performed by placing the cutting tool101in contact with the workpiece201. Furthermore, inFIG. 12, the workpiece201is rotated in a state where the rotation axis is fixed, and the cutting tool101is placed away from the workpiece201. In addition, according to the cutting method according to the present embodiment, the workpiece201is rotated in a state where the rotation axis is fixed and the cutting tool101is moved in each process. Naturally, the cutting method is not limited to this mode.

For example, in the process (1), the workpiece201may be placed close to the cutting tool101. Further, in the process (3), the workpiece201may be placed away from the cutting tool101. To continue cutting process, process of holding a state where the workpiece201is rotated, and placing the corner cutting edge9bof the cutting insert1in contact with different portions of the workpiece201only needs to be repeated. When the corner cutting edge9bin use is worn away, the corner cutting edge9bwhich is not used can be used by rotating the cutting insert1by 180 degrees with respect to the center axis of the through hole17or turning the cutting insert1upside down.

In addition, typical examples of materials of the workpiece201are carbon steel, steel alloy, stainless steel, cast iron or non-ferrous metal.

REFERENCE SIGNS LIST