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

A cutting insert of one aspect includes a main body section and a cutting section located at least at the front end side of the main body section, wherein the cutting section includes a top surface and a front cutting edge disposed along a ridge line at an intersection between the top surface and a front side surface, the front cutting edge includes a first section, a second section, and a third section, and a portion of the second section is located above the first section and the third section.The front side surface includes a first region located below the first section, a second region located below the second site, and a third regions located below the third site, wherein an angle of inclination of the second region is greater than angles of inclination of the first region and the third region.

TECHNICAL FIELD

The present embodiment relates to a cutting insert, a cutting tool, and a method for manufacturing a machined product.

BACKGROUND ART

Conventionally, the tip (cutting insert) described in Japanese Unexamined Patent Application Publication No. 2001-212704A (Patent Document 1) has been known as a cutting insert used in grooving of a work material. In the tip described in Patent Document 1, a front cutting edge is formed along a ridge line of a rake surface (top surface) and a front relief surface (front side surface). At substantially the center of the cutting edge ridge of the front cutting edge, a recess portion is disposed and lowers the rake surface, and a recessed groove extending successively rearward from the recess portion is disposed on the rake surface.

The front side surface on the tip described in Patent Document 1 is inclined rearward as it goes downward due to the fact that it is a relief surface. For this reason, the recess portion is formed recessing downward in a front end view, and formed recessing rearward in a top view. As a result, in grooving of a work material, an unmachined portion may be left at the groove bottom which is the machined surface, and smoothness of the groove bottom decreases.

In light of the problems described above, an object of the present aspect is to provide a cutting insert that can form a groove bottom with good machining precision, a cutting tool, and a method for manufacturing a machined product.

SUMMARY OF INVENTION

A cutting insert according to one aspect includes a main body section elongated in a direction from a rear end side toward a front end side, and a cutting section located at least at the front end side of the main body section. The cutting section includes a top surface, a front side surface adjacent to the top surface on the front end side and inclined toward the rear end side as a distance from the top surface increases, and a front cutting edge disposed along a ridge line at an intersection between the top surface and the front side surface.

The front cutting edge includes a first section, a pair of second sections sandwiching the first section therebetween, and third sections sandwiching the first section and the pair of second sections therebetween. A portion of the pair of second sections is located above the first section and the pair of third sections. The front side surface includes a first region located below the first section, a pair of second regions located below the pair of second sections, and a pair of third regions located below the pair of third sections. An inclination angle of the pair of second regions is greater than an inclination angle of the first region and an inclination angle of the third regions.

DESCRIPTION OF EMBODIMENTS

Cutting Insert

A detailed description will be given below of a cutting insert1of an embodiment (referred to below simply as “the insert1”) using the drawings. However, for convenience of explanation, each of the drawings referenced below is simplified to illustrate only the main members necessary to describe the embodiment. Accordingly, the cutting insert of the present invention may be provided with any constituent member which is not illustrated in each of the referenced drawings. Further, the dimensions of the members in the drawings do not faithfully represent the actual dimensions of the constituent members, the dimension ratios of the members, or the like.

As illustrated inFIGS. 1 to 11, an insert1of the present embodiment includes one main body section3and two cutting sections5. The main body section3has a rod shape elongated in a straight line from one side toward the other side. Furthermore, when one end of the rod-shaped main body section3is used as a front end, and the other end of the rod-shaped main body section3is used as a rear end, a central axis O extends from the rear end toward the front end on the main body section3. For this reason, the main body section3is said to elongate along the central axis O.

The main body section3includes a top side surface7located on a top side and that contacts a holder, and a bottom side surface9located on a bottom side and that contacts the holder. A top side groove portion7aextending in a direction along the central axis O is formed in the top side surface7. Furthermore, a bottom side groove portion (not illustrated) extending in the direction along the central axis O is formed in the same manner in the bottom side surface9. The insert1can be stably secured in the holder due to the insert1being provided with the top side groove portion7aand the bottom side groove portion and, as described later, also due to the holder being provided with a first protrusion that contacts the top side groove portion and a second protrusion that contacts the bottom side groove portion.

The size of the main body section3is not particularly limited but may, for example, be set so that a length along the central axis O is approximately from 5 to 80 mm. Additionally, a width in a direction orthogonal to the central axis O in a top view (horizontal direction inFIG. 2) may be set to, for example, approximately from 2 to 20 mm. Additionally, a height in a direction orthogonal to the central axis O in a side view (vertical direction inFIG. 5) may be set to, for example, approximately from 2 to 15 mm.

One cutting section5may be located at least at the front end side of the main body section3. In the present embodiment, one cutting section5is located at the front end side of the main body section3and another cutting section5is located at the rear end side of the main body section3. The main body section3and the cutting section5may be formed separately or integrally. In the insert1of the present embodiment, the main body section3and the cutting section5are formed integrally. Furthermore, a groove portion corresponding to the bottom side groove portion in the main body section3is formed on the bottom surface of the cutting section5in the present embodiment.

Examples of the material of the member constituting the insert1include cemented carbide alloy, cermet, or the like. Examples of the composition of the cemented carbide alloy include, for example, WC—Co, WC—TiC—Co, and WC—TiC—TaC—Co. WC—Co is produced by adding a cobalt (Co) powder to tungsten carbide (WC), and sintering the mixture. WC—TiC—Co is formed by adding titanium carbide (TiC) to WC—Co. WC—TiC—TaC—Co is formed by adding tantalum carbide (TaC) to WC—TiC—Co.

Further, cermet is a sintered composite material obtained by combining a metal with a ceramic component. Specifically, examples of the cermet include compounds in which a titanium compound such as titanium carbide (TiC), or titanium nitride (TiN) is the main component.

The surface of the member described above constituting the insert1may be coated with a coating film using a chemical vapor deposition (CVD) method or a physical vapor deposition (PVD) method. Examples of the composition of the coating film include titanium carbide (TiC), titanium nitride (TiN), titanium carbonitride (TiCN), alumina (Al2O3), and the like.

When performing machining using the insert1of the present embodiment, one of the two cutting sections5is used. In cases where the cutting section5located at the rear end side of the main body section3is used, the front end side and the rear end side of the main body section3are reversed and the insert1is attached to the holder. The cutting section5located at the front end side of the main body section3and the cutting section5located at the rear end side of the main body section3have the same shape. As such, in the following, a case where the cutting section5is located at the front of the main body section3will be described.

The cutting section5is provided with a top surface11, a bottom surface13, side surfaces, and cutting edges. As the side surfaces, a front side surface15, lateral side surfaces17, and corner side surfaces19are provided. As the cutting edges, a front cutting edge21, lateral cutting edges23, and corner cutting edges25are provided. Note that the lateral cutting edges23and the corner cutting edges25are optional.

The top surface11and the bottom surface13each extend from the rear end side to the front end side. The shape of the top surface11is roughly rectangular in a top view. The top surface11functions as a rake surface when cutting a work material. Of the outer periphery of the top surface11, the cutting section5is contiguous with the main body section3at the short edge located on the rear end side. Although not particularly illustrated, the shape of the bottom surface13is roughly rectangular, similar to the top surface11in a bottom view.

Of the side surfaces located between the top surface11and the bottom surface13, the front side surface15is a portion located at the front end side. Accordingly, the front side surface15is adjacent to the top surface11at the front end side of the cutting section5. The front side surface15has a substantially quadrilateral shape in a front end view. A pair of lateral side surfaces17is located at a portion of the side surfaces adjacent to the front side surface15. Each of the pair of lateral side surfaces17extends from the rear end side to the front end side. The front side surface15and the lateral side surfaces17are substantially orthogonal to each other, and corner side surfaces19are located between the front side surface15and the lateral side surfaces17. Since the front side surface15and the lateral side surfaces17connect smoothly, the corner side surfaces19have a curved surface shape.

In the insert1of the present embodiment, the central axis O is located passing through the center of the front side surface15of each of the two cutting sections5. The front side surface15has a substantially quadrilateral shape in a front end view, and the center portion in the height direction of the front side surface15and the center portion in the width direction serve as the center portion of the front side surface15. In the present embodiment, the intersection point of the diagonal lines on the front side surface15is also called the center portion of the front side surface15. Furthermore, in the present specification, “in a front end view” means viewing a side surface from the front end side where the front side surface is located.

The front side surface15, the lateral side surfaces17, and the corner side surfaces19each function as relief surfaces when cutting the work material. As such, the front side surface15, the lateral side surfaces17, and the corner side surfaces19each are directed toward the inside of the cutting section5, from the side of the top surface11toward the side of the bottom surface13in a side view. In other words, the front side surface15is inclined toward the rear end side as a distance from the top surface11increases. For example, inFIG. 4, the front side surface15located on the left end which is the front end side is inclined toward the right side which is the rear end side, from the top surface11side to the bottom surface13side.

Additionally, as the side surfaces are configured as described above, the bottom surface13is slightly smaller in size compared to the top surface11. A size of the cutting section5is not particularly limited but, for example, is set so that a length along the central axis O is approximately from 3 to 20 mm.

A front cutting edge21is disposed along a ridge line at an intersection between the top surface11and the front side surface15. Lateral cutting edges23are disposed along ridge lines at intersections between the top surface11and the lateral side surfaces17. Corner cutting edges25are disposed along ridge lines at intersections between the top surface11and the corner side surfaces19. When performing machining using the insert1of the present embodiment, the front cutting edge21is mainly used, and the lateral cutting edges23and the corner cutting edges25are also used as necessary. The work material is cut by these cutting edges.

In this case, the ridge lines where each of the front side surface15, the lateral side surfaces17, and the corner side surfaces19intersect with the top surface11do not have a strict linear shape due to the fact that two faces intersect. When the acute angles of the ridge lines where the side surfaces intersect with the top surface11are sharp, the durability of the cutting edge may degrade. As such, the portions where the top surface11and the side surfaces described above intersect are subjected to a so-called honing process, and these portions have a slightly curved shape.

The front cutting edge21in the present embodiment extends in a direction roughly parallel to the bottom surface13and orthogonal to the central axis O. The corner cutting edges25are connected to the front cutting edge21and the lateral cutting edges23, and the corner cutting edges25have an arc shape with the convex portion toward the outer side in a top view. The lateral cutting edges23have an ascending incline as the distance from the front cutting edge21and corner cutting edge25increases. In other words, the lateral cutting edges23are inclined upward from the front end side toward the rear end side. The lateral cutting edge23can decrease the generation of chatter vibration due to being inclined as described above.

Furthermore, as already shown, a groove portion is formed on the bottom surface13of the cutting section5in the present embodiment. For this reason, in the present embodiment, “parallel to the bottom surface13” means parallel to an imaginary plane (strictly speaking, an imaginary line in a front end view) that joins the two ends of the groove portion in a front end view.

The front cutting edge21has a roughly linear shape in a top view as illustrated inFIG. 3. On the other hand, the front cutting edge21has an M shape in a front end view as described below. The front cutting edge21includes a first section21a, a pair of second sections21b, and a pair of third sections21c. The first section21ain the present embodiment is located in the center of the front cutting edge21and includes the center of the front cutting edge21. The pair of second sections21bsandwiches the first section21atherebetween. The pair of third sections21csandwiches the first section21aand the pair of second sections21btherebetween.

Here, a portion serving as the highest point of the pair of second sections21bis located above the first section21aand the pair of third sections21c. For this reason, as illustrated inFIGS. 5 and 6, the front cutting edge21is formed in an M shape by the first section21a, the second sections21band third sections21cwith the center and the two ends recessing downward.

In particular, in the present embodiment, when an imaginary line L1is drawn joining the two ends of the front cutting edge21, the first section21a, second sections21b, and third sections21care divided by the region where the imaginary line L and the front cutting edge21intersect in a front end view.

For this reason, in the present embodiment, the first section21ais located below the imaginary line L1. The second sections21bare located above the imaginary line L1. The third sections21care the regions between the second sections21band the end portion of the front cutting edge21.

Furthermore, when the height of the front cutting edge21gradually decreases from the highest point of the pair of second sections21btoward the end portion of the front cutting edge21, one point of the end portion of the front cutting edge21corresponds to the third section21c.

In the present embodiment, the first section21ahas a curved shape that curves downward in a front end view. For this reason, the first section21ahas a shape protruding downward. The pair of second sections21bhave curved shapes that each curve upward in a front end view. For this reason, the second sections21bhave shapes protruding upward. The pair of third sections21chave curved shapes that each curve downward in a front end view. For this reason, the third sections21chave shapes protruding downward.

As such, due to the first section21a, second sections21b, and third sections21chaving respective curved shapes, the load is less likely to being excessively concentrated at portions of the first section21a, second sections21b, and third sections21c. Furthermore, due to the first section21a, second sections21b, and third sections21chaving respective curved shapes, the first section21aand the second sections21bare smoothly connected, and the second sections21band the third sections21care smoothly connected, even while the front cutting edge21has an M-shaped portion as described above. For this reason, the load is less likely to being excessively concentrated at the boundary between the first section21aand second sections21band the boundary between the second sections21band third sections21c.

The front side surface15in the present embodiment includes an upper region27located on a side of the top surface11and a lower region29located on a side of the bottom surface13. The upper region27includes a first region27a, second regions27b, and third regions27c. The first region27ais located below the first section21aon the front cutting edge21. The second regions27bare located below the second sections21bon the front cutting edge21. The third regions27care located below the third sections21con the front cutting edge21.

The lower region29on the front side surface15has a flat planar shape. On the other hand, the upper region27on the front side surface15does not have a flat planar shape. Specifically, the first region27a, the second regions27b, and the third regions27cin the upper region27are all inclined toward the rear end side as a distance from the top surface11increases, but the angles of inclination are not fixed.

In the present embodiment, the inclination angle of the first region27ais called the first inclination angle θ1, the inclination angle of the pair of second regions27bis called the second inclination angle θ2, and the inclination angle of the pair of third regions is called the third inclination angle θ3. More specifically, as illustrated inFIG. 9, the first inclination angle θ1is evaluated by the angle formed by an imaginary line L2parallel to the central axis O on the lowest point of the first section21aand an imaginary extended line27a′ of the first region27a.

Furthermore, as illustrated inFIG. 10, the second inclination angle θ2is evaluated by the angle formed by an imaginary line L2parallel to the central axis O on the highest point of the second section21band an imaginary extended line27b′ of the second region27b. As illustrated inFIG. 11, the third inclination angle θ3is evaluated by the angle formed by an imaginary line L2parallel to the central axis O on the lowest point of the third section21cand an imaginary extended line of the third region27c′.

However, as illustrated inFIG. 12, when the first region27ais not indicated by a straight line in cross-section, in other words, when the first inclination angle θ1is not fixed, the first inclination angle θ1may be evaluated by the angle formed by a tangent27a″ of the highest point of the first region27aand an imaginary line L2parallel to the central axis O. This is the same for the second inclination angle θ2and the third inclination angle θ3.

In the present embodiment, the second inclination angle θ2of the pair of second regions27bis greater than the first inclination angle θ1of the first region27a. Furthermore, the second inclination angle θ2described above is greater than the third inclination angle θ3of the third regions27c.

For this reason, as illustrated inFIG. 7, on the cross-section parallel to the bottom surface13passing through the upper region27, the pair of second regions27bare recessed and located more to the rear end side than the first region27aand the third regions27c. In other words, the first region27aand the third regions27chave a configuration that protrudes more to the front end side than the second regions27b. On the other hand, since the lower region29has a flat planar shape, the lower region29is indicated by a linear shape in the cross-section parallel to the bottom surface13passing through the lower region29, as illustrated inFIG. 8.

FIG. 7is a cross-sectional view of a cross-section orthogonal to the vertical direction, which is a cross-section parallel to the bottom surface13indicated by line A1-A1inFIG. 5. Furthermore,FIG. 8is a cross-sectional view of a cross-section orthogonal to the vertical direction, which is a cross-section parallel to the bottom surface13indicated by line A2-A2inFIG. 5.FIG. 9is a cross-sectional view of a cross-section orthogonal to the first section21ain a top view, which is indicated by line A3-A3inFIG. 6. Furthermore,FIG. 10is a cross-section orthogonal to the second sections21bin a top view, which is indicated by line A4-A4inFIG. 6.

When the front cutting edge21has an M-shaped portion as described above, and the inclination angles of the regions connected to the front cutting edge21on the front side surface15are fixed, the front cutting edge21has a shape in which the first section21aand the third sections21cof the front cutting edge21are recessed rearward in a top view. For this reason, in grooving of a work material, smoothness of the groove bottom decreases.

However, in the present embodiment, the front side surface15has a first region27a, second regions27b, and third regions27c, all having mutually different inclination angles as described above. For this reason, the cutting edge21can be curved in a front end view, while on the other hand, the recesses described above can be reduced and the front cutting edge21can be closer to a linear shape. For this reason, a groove bottom can be formed with high machining precision while the cutting insert has good cutting strength.

The front cutting edge21in the present embodiment has a curved shape in which the first section21a, the second sections21b, and the third sections21ceach curve in a front end view. For this reason, the first region27a, the second regions27b, and the third regions27con the front side surface15do not have flat planar face shapes. Specifically, the first region27ahas a concave surface shape that recesses toward the rear end side and upward. The third regions27chave a concave surface shape that recesses toward the rear end side and upward. Furthermore, the second regions27bhave a convex surface shape that protrudes toward the front end side and downward, the opposite of the first region27aand the third regions27c.

The front cutting edge21in the present embodiment has a curved shape in which the first section21a, the second sections21b, and the third sections21ceach curve in a front end view. For this reason, the first inclination angle θ1gradually becomes greater from the lowest point of the first section21atoward the second sections21b. The second inclination angles θ2gradually each become smaller from the highest point of the second section21btoward the first section21aand the third sections21c. Furthermore, the third inclination angle θ3gradually becomes greater from the lowest point of the third sections21ctoward the second sections21b. Due to the front cutting edge21having these configurations, the shape of the front cutting edge21in a top view can be closer to a linear shape.

The lowest point of the first section21aon the front cutting edge21in the present embodiment is located below the third sections21c. As a result, the depth in the vertical direction of the concave portion constituted by the first section21aand the second sections21bcan be maintained at a high depth. For this reason, chips produced at the pair of third sections21care drawn easily by the chips produced at the concave portion on the front cutting edge21. This reduces the possibility of the chips contacting the side surface of the groove, which is one of the machined surfaces in grooving.

Here, the third inclination angle θ3of the pair of third regions27cbecomes greater than the first inclination angle θ1of the first region27abecause the front cutting edge21is close to a linear shape in a top view while the lowest point of the first section21ais located below the third section21c.

Furthermore, in order for the chips produced at the pair of second sections21bto be easily drawn by the chips produced at the first section21a, the top surface11includes a pair of projecting portions31and a recess portion33. In the present embodiment, the pair of projecting portions31extends from the pair of second sections21bon the front cutting edge21toward the rear end side. Furthermore, the recess portion33is located between the pair of projecting portions31, and extends from the first section21aon the front cutting edge21toward the rear end side.

Furthermore, in order for the chips produced at the pair of second sections21bto be easily drawn by the chips produced at the first section21a, the width of the first section21ain the direction orthogonal to the vertical direction (horizontal direction inFIG. 5) is greater than the respective widths of the pair of second sections21b.

Additionally, in order for the chips produced at the pair of third sections21cto be easily drawn by the chips produced at the pair of second sections21b, the width of the pair of the second sections21bin the direction orthogonal to the vertical direction (horizontal direction inFIG. 5) is greater than the width of the pair of third sections21c.

The size of the first inclination angle θ1is set to, for example, approximately 75 to 87°. The size of the second inclination angle θ2is set to, for example, approximately 77 to 89°. Furthermore, the size of the second inclination angle θ3is set to, for example, approximately 76 to 88°.

Cutting Tool

Next, description will be given of a cutting tool101of an embodiment of the present invention using the drawings.

The cutting tool101in the present embodiment is provided with a holder105and the above-described cutting insert1. The holder105includes an insert pocket103on a front end. The cutting insert1is mounted to the insert pocket103with at least the front cutting edge21protruding from the front end of the holder105, as illustrated inFIG. 13.

The holder105of the present embodiment has a slender, elongated rod shape. A direction in which the holder105is slenderly elongated matches the direction in which the central axis of the insert1elongates. Also, the front end of the holder105is provided with one insert pocket103. The insert pocket103is a portion on which the insert1is mounted, and is opened to a front end surface of the holder105.

The holder105has an upper jaw portion107that constrains the top side surface of the main body section of the insert1, and a lower jaw portion109that constrains the bottom side surface of the main body section of the insert1. The insert pocket103is defined by the region where the upper jaw portion107and the lower jaw portion109face. The main body section of the insert1is inserted and secured in the insert pocket103, that is, between the upper jaw portion107and the lower jaw portion109. In this case, the top side surface of the main body section contacts the upper jaw portion107of the holder105. Also, the bottom side surface of the main body section contacts the lower jaw portion109of the holder105.

The top side surface of the main body section has the top side groove portion. As such, a first protrusion that contacts the top side groove portion is disposed in a region of the upper jaw portion107that faces the lower jaw portion109. Additionally, the bottom side surface of the main body section has the bottom side groove portion. As such, a second protrusion that contacts the bottom side groove portion is disposed in a region of the lower jaw portion109that faces the upper jaw portion107.

In the present embodiment, the holder105has a first screw hole (not illustrated) formed in the upper jaw portion107and a second screw hole (not illustrated) formed in the lower jaw portion109beneath the first screw hole. A fixing screw111is inserted in these screw holes and, thereby, the insert1is secured to the holder105. Specifically, the fixing screw111is inserted into the first screw hole formed in the upper jaw portion107and the front end of the fixing screw111is then inserted into the second screw hole formed in the lower jaw portion109. Thus, the fixing screw111is screwed into the first screw hole and the second screw hole.

For the holder105, it is possible to use steel, cast iron, or the like. In particular, it is preferable to use steel with a high toughness in these members.

Method for Manufacturing a Machined Product

Next, description will be given of a method for manufacturing a machined product of one embodiment of the present invention with reference to the drawings.

The machined product is manufactured by machining a work material201. In the present embodiment, boring is given as an example of the machining. The method for manufacturing a machined product of the present embodiment includes the following steps. Specifically, it includes the steps of:

(1) rotating a work material201;

(2) bringing at least the front cutting edge21of the cutting tool101exemplified in the above embodiment into contact with the work material201that is rotating; and

(3) separating the cutting tool101from the work material201.

More specifically, first, as illustrated inFIG. 14, the work material201is rotated in a D1 direction about an axis D. The cutting tool101is brought relatively close to the work material201by moving the cutting tool101in a D2 direction. Next, as illustrated inFIG. 15, the front cutting edge21, the corner cutting edges, and the lateral cutting edges of the cutting tool101are brought into contact with the work material201, and the work material201is cut. Then, as illustrated inFIG. 16, the cutting tool101is relatively moved away from the work material201by moving the cutting tool101in a D3 direction.

In the present embodiment, the cutting tool101is brought close to the work material201in a state where the axis D is fixed and the work material201is rotating. Furthermore, inFIG. 15, the work material201is cut by bringing the front cutting edge21, the corner cutting edges, and the lateral cutting edges of the cutting insert1into contact with the work material201that is rotating. Furthermore, inFIG. 16, the cutting tool101is moved away from the work material201in a state where the work material201is rotating.

Further, in the machining of the manufacturing method of the present embodiment, in each of the respective steps, although the cutting tool101is brought into contact with or separated from the work material201by moving the cutting tool101, the present embodiment is of course not limited to such a mode.

For example, in step (1), the work material201may be brought close to the cutting tool101. In the same manner, in step (3), the work material201may be moved away from the cutting tool101. In a case where the machining is to be continued, steps of bringing the cutting edges of the cutting insert1into contact with different positions on the work material201may be repeated by maintaining the rotating state of the cutting tool101.

Here, representative examples of the material of the work material201include carbon steel, alloy steel, stainless steel, cast iron, non-ferrous metals, or the like.

REFERENCE SIGNS LIST