Cutting insert, cutting tool and cutting method using the same

A cutting insert provided with an upper surface, side surfaces, and cutting edges provided at portions at which the upper surface and the side surfaces intersect with each other. Each side surface has grooves reaching the upper surface so as to divide the cutting edge into small cutting edges. Projections are provided on the upper surface at positions to which the grooves extend.

TECHNICAL FIELD

The present invention relates to a cutting insert and the like.

BACKGROUND ART

Conventionally, a rotating tool such as a face mill cutter, an end mill or the like, particularly a throw away type rolling tool structured such that a cutting insert is installed to a holder has been in heavy usage in terms of an economical efficiency.

A great load is applied to a rolling tool having a long cutting edge at a time of cutting. Accordingly, a cutting insert in which a cutting resistance applied at a time of cutting is reduced has been proposed.

For example, in patent document 1, there is disclosed a cutting insert provided with a cutting edge which is positioned on an intersection of an upper surface and a side surface, and a groove portion which is provided on the side surface in such a manner as to divide the cutting edge. In accordance with the structure mentioned above, a chip is divided finely in a width direction, and a cutting resistance applied at a time of cutting is reduced.

However, in the cutting insert, a plurality of chips divided finely in the width direction are generated, and there is a risk that a plurality of chips come into collision with each other. Accordingly, there has been demanded a structure which has an excellent chip discharging property as well as reducing a cutting resistance.

PRIOR ART PUBLICATION

Patent Publication

SUMMARY OF THE INVENTION

An object of the present invention is to provide a cutting insert, a cutting tool and a cutting method having an excellent chip discharging property as well as reducing a cutting resistance.

MEANS FOR SOLVING THE PROBLEM

In accordance with the present invention, there is provided a cutting insert comprising:

an upper surface;

a first side surface; and

a first cutting edge positioned on a first intersection in which the upper surface intersects the first side surface,

wherein a groove portion having an end portion reaching the upper surface exists on the first side surface, the first cutting edge is divided into two small cutting edges by the end portion of the groove portion, and a convex portion is positioned at an extension area through which the groove portion passes in the case of extending the groove portion on the upper surface in a longitudinal direction.

In accordance with the present invention, there is provided a cutting tool comprising:

a holder; and

the cutting insert according to any one of claims1to12which is installed to the holder,

wherein at least apart of the first cutting edge protrudes outward over an outer periphery of the holder.

In accordance with the present invention, there is provided a cutting method comprising:

a moving close step of relatively moving a workpiece close to the cutting tool according to claim13or14;

a cutting step of cutting a surface of the workpiece by bringing the first cutting edge of the cutting tool which is rotated into contact with the surface of the workpiece; and

a separating step of relatively keeping the workpiece away from the cutting tool.

In accordance with the cutting insert and the cutting tool of the present invention, it is possible to inhibit a plurality of chips generated at a time of cutting from coming into collision with each other, by the convex portion provided in correspondence to the groove portion. Accordingly, the cutting insert in accordance with the present invention achieves an excellent chip discharging property as well as achieving a reduction of the cutting resistance applied at a time of cutting.

MODE FOR CARRYING OUT THE INVENTION

A description will be in detail given below of an embodiment in accordance with the present invention with reference to the accompanying drawings.

Cutting Insert

First Embodiment

FIGS. 1 to 3show an embodiment in accordance with the present invention.

An insert1is provided with an upper surface2, a side surface3, and a cutting edge4provided on an intersection of the upper surface2and the side surface3. The upper surface2is formed as an approximately polygonal shape, and is specifically formed as an approximately rectangular shape. Further, the insert1is provided with a rake face area21which is provided on the upper surface in such a manner as to extend inward from the cutting edge4.

In the present embodiment, the cutting edge4has a first cutting edge41, a second cutting edge42, and a third cutting edge43connected to the first cutting edge41and the second cutting edge42.

As shown inFIG. 2(a), the first cutting edge41is positioned at a first intersection in which the upper surface2intersects the first side surface3. In other words, it is positioned on one side of the upper surface2forming an approximately rectangular shape. Further, the second cutting edge42is positioned on a second intersection in which the upper surface2intersects the second side surface3. In other words, it is positioned on the other side which is adjacent to the one side of the upper surface2. Further, the third cutting edge43is positioned on a corner portion (a third intersection) formed by the crossing of the one side and the other side.

In the present embodiment, a first cutting edge41and a second cutting edge42are arranged in such a manner as to form an obtuse angle in a top view. Specifically, an angle formed by a virtual extension line of the first cutting edge41and a virtual extension line of the second cutting edge42in the top view is an obtuse angle. The insert1can be applied to a face mill cutter by employing an arrangement of the cutting edges as mentioned above.

In the cutting tool mentioned below, the first cutting edge41serves as a main cutting edge, the second cutting edge42serves as an auxiliary cutting edge, and the third cutting edge43serves as a corner cutting edge.

In this case, in the present embodiment, the first cutting edge41is provided on each of sides of the upper surface2formed as the approximately rectangular shape. Accordingly, the insert1has four first cutting edges41. Further, the second cutting edge42and the third cutting edge43are provided in correspondence to each of the four first cutting edges41. In other words, the insert1has four second cutting edges42and four third cutting edges43. In this case, four third cutting edges43are positioned respectively at four corner portions of the approximately rectangular shape.

Further, the insert1has a groove portion5and a convex portion6.

As shown inFIGS. 1 and 2(b), the groove portion5is provided on the side surface3in such a manner as to divide the cutting edge4into a plurality of small cutting edges411. In the present embodiment, the first cutting edge41is divided by two groove portions5. In other words, the first cutting edge41is divided into three small cutting edges411by the two groove portions5. As mentioned above, since the first cutting edge41is divided into three small cutting edges each having a short cutting edge length, a plurality of generated chips have a small width, in the insert1. Accordingly, a load applied to the insert at a time of cutting becomes small. As a result, it is possible to achieve an excellent cutting performance even under a severer cutting condition.

Further, as shown inFIGS. 1 and 2(a), the convex portion6is formed on the upper surface2in such a manner as to correspond to the groove portion. Specifically, the convex portion6is formed on the rake face area21connecting to the first cutting edge and extending inward from the first cutting edge. Note that in the case where a land portion is formed on the first cutting edge, the land portion is included in the rake face area. In this case, the matter that “the convex portion6corresponds to the groove portion5” means that the convex portion6is arranged on the upper surface2in such a manner as to satisfy the following two points.The convex portion6is positioned inside the groove portion5on the upper surface2.At least a part of the convex portion6is positioned on a virtual straight line M passing the center in a width direction of the groove portion5and extending along an extension direction of the groove portion5.

In the present embodiment, the convex portion6is formed along the virtual straight line M. In other words, it is positioned at an extension region through which the groove portion5passes in the case that it extends in its longitudinal direction, on the upper surface.

Meanwhile, the inner side in this case means a direction heading for the center side of the insert1with respect to the cutting edge4in the top view.

Further, as shown inFIG. 1, the convex portion6is positioned at a higher position than the rake face area21. In other words, the convex portion6is provided so as to be protuberant upward from the rake face area21of the upper surface2.

The insert1in accordance with the present embodiment can stabilize the chip discharging direction by the convex portion6structured as mentioned above, in such a manner as to prevent the chips each having the short width and generated by the small cutting edge411from coming into contact with each other. Accordingly, it is possible to suppress a damage of the cutting edge and the holder caused by a biting of the chips between the cutting edge ad the workpiece, a deterioration of a worked surface of the workpiece, a deterioration of a working precision and the like.

In other words, the chips generated by the small cutting blade411are curled along the rake face area21extending inward from the small cutting edge411. At this time, the convex portion6is provided in the inner side of the groove portion5, that is, in a direction in which the chips are discharged with respect to the groove portion5. It is possible to inhibit the discharging direction of the chips which are divided finely in the width direction from deflecting right and left, by means of the convex portion6. Accordingly, it is possible to inhibit the chips which are generated by the small cutting edge411from coming into collision with each other. As a result, it is possible to achieve an excellent chip discharging property.

Particularly, even in a cutting work mode in which a great load is applied at a time of the cutting work, such as an intermittent cutting, a high speed feeding work or the like, it is possible to achieve an excellent chip discharging property in addition to achieving a reduction of the chip resistance applied at a time of cutting.

Further, as shown inFIG. 3, the convex portion6has a pair of inclined side surfaces91and92. The pair of inclined side surfaces91and92are inclined toward the rake face area21corresponding to each of the two small cutting edges411positioned on both ends of the groove portion5in the upper surface2, from a top portion of the convex portion6.

Specifically, a pair of inclined side surfaces is provided with the first inclined surface91which is positioned close to the third cutting edge43side, and the second inclined side surface92which is positioned in a side being away from the first inclined surface91with respect to the third cutting edge43. The inclined side surfaces91and92are inclined in such a manner as to be positioned at a lower level as they come away from the virtual straight line M extending from the groove portion5mentioned above. In other words, the first inclined side surface91is inclined in such a manner as to be positioned at a lower level as it heads for the second cutting edge42from the top portion of the convex portion6. On the other hand, the second inclined side surface92is inclined in such a manner as to be positioned at a lower level as it heads for an opposite side to the second cutting edge42with respect to the convex portion6from the top portion of the convex portion6.

As mentioned above, since the convex portion6is provided with a pair of inclined side surfaces which are inclined toward the rake face area21, on both sides of the virtual straight line M in which the groove portion5and the convex portion6extend, it is possible to inhibit the discharging direction of the chips formed by the small cutting edge411from deflecting right and left.

Further, the pair of inclined side surfaces91and92is provided in such a manner as to protrude from the respective corresponding groove portions5to the small cutting edge411side in the top view. In other words, a width W6of the convex portion6is larger than a width W5of the groove portion5in the top view. In accordance with the structure mentioned above, the chip generated by the small cutting edge411is first of all curled along the rake face area21extending inward from the small cutting edge421. At this time, an end portion of the chip comes into contact with the inclined side surface of the convex portion6, and the chip is deformed in such a manner that a cross sectional shape of the chip comes to a concave shape. Accordingly, it is possible to reduce the width of the chip generated by the small cutting edge411little by little as the chip is curled along the rake face area21. As a result, an effect of inhibiting the adjacent chips from coming into collision with each other is enhanced.

In this case, the width W6of the convex portion6is a maximum value in the dimension in the direction extending along the first cutting edge41of the convex portion6in the top view.

Further, the width W5of the groove portion5means a distance between two crossing points of the virtual extension line of the wall surface of the groove portion5and the virtual extension line of the small cutting edge411, as shown inFIG. 3.FIG. 3exemplifies a width of a first groove51mentioned below. In this case, the wall surface of the groove portion5means a series of surfaces continuously connected to the rake face area21and the side surface3. Note that, in the case that a whole of the wall surface of the groove portion5is constructed by a curved surface, as is different from the present embodiment in which the wall surface of the groove portion5has a flat surface, a tangential line of the curved surface may be set to the virtual extension line of the wall surface of the groove portion mentioned above.

Further, as shown inFIG. 4, an angle of gradient θ91of the first inclined side surface91may be identical to an angle of gradient θ92of the second inclined side surface92; however, it is desirable that the angle of gradient θ91of the first inclined side surface91is larger than the angle of gradient θ92of the second inclined side surface92(θ91>θ92). In the case that θ91and θ92satisfy the relationship mentioned above, it is possible to combine an effect that the first inclined side surface91positioned close to the third cutting edge43side with which the generated chip is more likely to come into contact stabilizes the chip discharging direction, and an effect that the second inclined side surface92with which the generated chip is less likely to come into contact enhances a strength of the upper surface2, with a good balance.

Particularly, in the case that the insert1is installed to a holder while having a positive axial rake, the small cutting edge411is going to come into contact with the workpiece from the third cutting edge43side sequentially. Accordingly, the chip generated by the small cutting edge411is discharged in such a manner as to be pushed up from the third cutting edge43side coming into contact with the workpiece in advance. Accordingly, the discharging direction of the chip mentioned above is not a direction which is approximately vertical to the first cutting edge41, but tends to be deviated in a direction in which it comes away from the third cutting edge43toward the inner side with respect to the direction. Even in the case mentioned above, since θ91and θ92satisfy the relationship mentioned above, it is possible to preferably achieve a curl function and a guide function.

The angles of gradient θ91and θ92in this case each mean an angle at which the first inclined side surface91or the second inclined side surface92is inclined with respect to the lower surface, in a cross sectional view approximately in parallel to the first cutting edge41by which the maximum width W6of the convex portion6can be obtained.

Meanwhile, the matter “the top portion of the convex portion6is positioned at a higher position than the cutting edge4” in this case means the matter that the top portion of the convex portion6is positioned at higher position than the cutting edge4, on the basis of the lower surface of the insert1. Specifically, it means that a distance H6between the lower surface and the top portion of the convex portion6is larger than a distance H4between the lower surface and the cutting edge4. Further, the top portion of the convex portion6means a portion which is positioned at the highest level in the convex portion6. Therefore, H6means a maximum value in the distance between the lower surface and the convex portion6. Further, in the same manner, in the case that the cutting edge4is constructed by an inclined cutting edge, H4means a maximum value in the distance between the lower surface and the cutting edge4.

Further, a breaking groove71is formed on the upper surface2. The breaking groove71is formed inside the rake face area21and at a position which is away from the small cutting edge411than the convex portion6. Further, the breaking groove71is inclined in such a manner as to be positioned at a higher position toward the inner side. The breaking groove71is arranged in such a manner as to be opposed to the small cutting edge411. In accordance with the structure mentioned above, the breaking groove71can stably further curl the chip which is generated by the small cutting edge411and is curled along the rake face area21, and can cut the chip in the longitudinal direction.

More specifically, the rake face area21extending toward the inner side from the small cutting edge411and the breaking groove71can achieve a breaker function, while a pair of side surfaces can achieve a guide function of stabilizing the chip discharging direction. Since the breaking groove71is provided as mentioned above, it is possible to preferably combine the breaker function and the guide function.

Furthermore, the breaking groove71is connected to the inner side of the convex portion6. In accordance with the structure mentioned above, it is possible to improve a strength of an area in which a strength of the upper surface2is lowered by the formation of the groove portion5. In other words, the convex portion6serves as a reinforcing portion of the upper surface2, in the area mentioned above. Accordingly, it is possible to suppress a defect of the rake face area21and the groove portion5which tend to get chipped. As a result, it is possible to achieve an improvement of a tool service life.

Further, the convex portion6has an inclined center surface8which is positioned between a pair of inclined side surfaces91and92. It is preferable that the inclined center surface8is constructed by a flat surface extending toward the inner side from the groove portion5side. Further, the inclined center surface8is inclined in such a manner as to be positioned at a higher position as it comes away from the groove portion5. Since the inclined center surface8mentioned above is provided, it is possible to achieve an improvement of the chip discharging property as well as it is possible to achieve an improvement of a strength of the rake face area21.

In this case, it is sufficient that at least a part of the inner side of the convex portion6is connected to the breaking groove71. In the present embodiment, as shown inFIG. 4, the inclined center surface8of the convex portion6is connected to the breaking groove71. Accordingly, the function that the convex portion6guides the chip is enhanced.

Further, in the present embodiment, a center portion7is provided on the center of the upper surface2. The center portion7is positioned at a higher position than the rake face area21. The breaking groove71is arranged on a surface which is opposed to the small cutting edge411of the center portion7. Specifically, in the present embodiment, the breaking groove71corresponds to a surface which is positioned closest to the small cutting edge411in the center portion7. Therefore, in the present embodiment, the inner side of the convex portion6is connected to the center portion7. In other words, the convex portion6serving as the reinforcing portion as mentioned above is formed so as to be integrated with the center portion7. In accordance with the structure mentioned above, the strength of the upper surface2is further enhanced. Accordingly, it is possible to suppress the defect of the cutting edge4starting from the vicinity of the groove portion5.

Meanwhile, in the present embodiment, a through hole penetrating from the upper surface2to the lower surface is formed in the center portion7of the insert1. The through hole15is a hole to which a screw is inserted at a time of screw fastening to the holder. The center portion7is provided on an outer periphery of the through hole15, and is formed approximately as a rectangular shape in the top view, in the present embodiment. Further, an upper surface of the center portion7is formed as a flat surface which is approximately in parallel to the lower surface. In accordance with the structure mentioned above, it is possible to improve the strength of the upper surface2.

It is preferable that an angle θ8formed by the inclined center surface8and the rake face area21is between 135 degree and 165 degree. In accordance with the structure mentioned above, the convex portion6can preferably achieve the guide function as well as it is possible to suppress a clogging of the chips in an area between the convex portion6and the groove portion5.

In this case, the angle θ8formed by the inclined center surface8and the rake face area21can be defined by a cross section which passes through the center in the width direction of the groove portion5and is approximately in parallel to the extending direction of the groove portion5, as shown inFIG. 4(b). The extending direction of the groove portion5here means a direction which is approximately in parallel to a wall surface in the top view in the case where the groove portion5has a flat wall surface such as in the case of the present embodiment. Further, in the case where the groove portion5does not have the flat wall surface, it means an extending direction of a line connecting the center in the width direction in the end portion in the cutting edge4side of the groove portion5to the center in the width direction in the end portion in the inner side of the groove portion5.

Further, the inclined center surface8is constructed by the flat surface in the present embodiment; however, is not limited to the embodiment, but may be constructed by a curved surface. In this case, in the embodiment in which the inclined center surface8is formed as the flat surface, a strength of the insert1is high.

In this case, in the present embodiment, the inclined center surface8is provided on the upper surface2so as to be away from the groove portion5. Accordingly, the strength of the upper surface2of the insert1is improved, and it is possible to inhibit the insert1from chipping starting from the vicinity of the groove portion5. Further, it is possible to suppress the chip at a time of manufacturing the insert1, and a yield ratio is improved.

Further, in the present embodiment, the top portion of the convex portion6is positioned at a higher position than the cutting edge4. Accordingly, it is possible to inhibit the chip generated by the small cutting edge411from running on the convex portion6. As a result, the effect of inhibiting the adjacent chips from coming into collision with each other is enhanced.

Further, as shown inFIG. 3, a width W8close to the groove portion5of the inclined center surface8is smaller than the width W5of the groove portion5in the top view. Accordingly, it is possible to smoothly curl the chip generated by the small cutting edge411along the rake face area21. In other words, it is possible to inhibit the chip generated by the small cutting edge411from strongly coming into collision with the convex portion6and inhibit the discharging direction of the chip from becoming unstable. Therefore, it is possible to inhibit the chip from being clogged between the groove portion5and the inclined center surface8so as to scrape the worked wall surface, and a working precision is improved.

In this case, the width8close to the groove portion5of the inclined center surface8is a value of a width of the inclined center surface8which is calculated by the same method as the width W8of the inclined center surface8mentioned above, in the end portion closest to the groove portion5in the inclined center surface8. Further, the width W5of the groove portion5is a maximum value in the dimensions in the direction extending along the first cutting edge41of the groove portion5in the top view.

In this case, in the present embodiment, the width of the inclined center surface8is the smallest in the groove portion5side, and is reduced toward the inner side. A shape of the inclined center surface8is not limited to the embodiment, but may be structured such that a fixed width is given as it heads for the inner side from the groove portion5side, or may be structured such that the width is increased toward the inner side from the groove portion5side.

Further, it is preferable that an angle formed by at least one of the first inclined side surface91and the second inclined side surface92and the inclined center surface8is an obtuse angle. In the present embodiment, as shown inFIG. 4(a), both the first inclined side surface91and the second inclined side surface92form an obtuse angle with respect to the inclined center surface8. In accordance with the structure mentioned above, an improvement of the strength of the convex portion6itself can be achieved, as well as an improvement of the strength of the upper surface2can be achieved. Accordingly, it is possible to inhibit the insert1from chipping at a time of cutting.

In this case, it is preferable that the first inclined side surface91and the second inclined side surface92are each constructed by a flat surface. Accordingly, a chip guide function becomes preferable.

Further, as mentioned above, in the present embodiment, three groove portions5dividing the first cutting edge41are provided. In this case, as shown inFIG. 3, the groove portion5positioned closest to the third cutting edge43among a plurality of groove portions5is set to a corner groove portion5a. The corner groove portion5ais a groove portion5which is adjacent to a small cutting edge411aconnected to the first cutting edge41.

In the case that the groove portion5is the corner groove portion5awhich is provided on the third cutting edge43side serving as a corner cutting edge as mentioned above, it is preferable that it is constructed as follows.

In other words, the convex portion corresponding to the corner groove portion5ais set to a corner convex portion6a. At this time, the corner convex portion6ahas a first edge portion11and a second edge portion12which extend to the inner side from the groove portion5, in the top view. The first edge portion11is positioned closer to the second cutting edge42side than the second edge portion12.

Further, the first edge portion11is arranged so as to come away from the second cutting edge42as it heads for the inner side from the groove portion5, in the top view. In other words, a virtual extension line L11of the first edge portion11and a virtual extension line L42of the second cutting edge42are arranged so as to come away from each other as they head for the inner side from the small cutting edge411, in the top view. Specifically, a distance between the first edge portion11and the second cutting edge42(a distance between L11and L42) becomes minimized in the small cutting edge411side, and becomes maximized in the inner side, in the top view.

A chip generated by the small cutting edge411aconnected to the third cutting edge43is generated integrally with the chip generated by the third cutting edge43. Accordingly, the chip generating direction is affected by the corner portion of the third cutting edge43, and is deviated to a direction of coming away from the third cutting edge43as it heads for the inner side with respect to a direction (L41) which is approximately vertical to the first cutting edge41.

Accordingly, it is possible to inhibit the chip having the generating direction as mentioned above and generated by the small cutting edge411aconnected to the third cutting edge43from energetically coming into collision with the convex portion6, by setting the arrangement of the first edge portion11and the second edge portion12to the above. Therefore, it is possible to inhibit a great friction resistance from being generated between the chip and the convex portion6at a time of cutting. As a result, it is possible to smoothly discharge the chip.

In this case, in the case that the insert1is installed to the holder while having a positive axial rake as mentioned above, the generating direction of the chip mentioned above is further largely deviated at that degree. Accordingly, in the case that the insert1is used by being installed to the holder while having the positive axial rake, it is preferable that they are arranged so as to come away largely as L42and L11head for the inner side. In other words, it is preferable to make an angle of gradient of L112with respect to L42large.

Further, it is desirable that the following structure is satisfied in the two groove portions5positioned on both ends of one small cutting edge411, among a plurality of groove portions5. Here, a description will be given by exemplifying a small cutting edge411bpositioned in adjacent to the small cutting edge411aconnected to the third cutting edge43, as one small cutting edge411.

First of all, among a plurality of groove portions5, the groove portion5which is adjacent to one end of the small cutting edge411bof the two groove portions5positioned on both ends of the small cutting edge411bis set to a first groove portion51. Further, the groove portion5which is adjacent to the other end of the small cutting edge411bis set to a second groove portion52. Then, the second groove portion52is positioned closer to the third cutting edge43side than the first groove portion51.

In this case, the second groove portion52positioned close to the third cutting edge43side corresponds to the corner groove portion5amentioned above.

The rake face area21is provided with a first convex portion61and a second convex portion62, respectively, in correspondence to the first groove portion51and the second groove portion52. Further, the first convex portion61and the second convex portion62, respectively, have the first inclined side surface91and the second inclined side surface92as mentioned above. The first and second inclined side surfaces91and92are positioned on both sides of each of the inclined center surfaces8. In this case, the adjacent first convex portion61and second convex portion62are away from each other, and are structured such as not to obstruct the flow of the chip generated from the small cutting edge. In other words, the rake face area21is arranged between the convex portions. More specifically, the convex portion is not arranged on a vertical bisector of the small cutting edge.

Further, in the present embodiment, as shown inFIG. 4(a), an angle of gradient α of the first inclined side surface91in the first convex portion61is larger than an angle of gradient β of the second inclined side surface92in the second convex portion62. In accordance with the structure mentioned above, the angle of gradient of the inclined side surface of the convex portion is sharp on an end portion positioned in an opposite side to the third cutting edge43with respect to the small cutting edge411bof both ends of the small cutting edge411b, and the angle of gradient of the convex portion is gentle on an end portion positioned close to the third cutting edge43side with respect to the small cutting edge411b. Accordingly, it is possible to enhance the guide function of the convex portion on the end portion positioned in the opposite side to the third cutting edge43of both ends of the small cutting edge411, and it is possible to enhance the curl function of the convex portion on the end portion positioned close to the third cutting edge43side of both ends of the small cutting edge411.

Accordingly, it is possible to stabilize the discharging direction of the chip generated by the small cutting edge411bin which both ends are pinched by the groove portions5. Therefore, it is possible to enhance an effect of inhibiting the chip generated by the small cutting edge411aand generated integrally with the chip generated by the first cutting edge41, and the chip generated by the small cutting edge411bin which both ends are pinched by the groove portions5, from coming into collision with each other.

Second Embodiment

As shown inFIGS. 5 and 6, the number of the groove portions5dividing the first cutting edge41is different between an insert1′ in accordance with the present embodiment and the insert1in accordance with the first embodiment. Specifically, the number of the groove portions5dividing the first cutting edge41is two in the insert1, while is three in the insert1′. In other words, the first cutting edge41is divided into four small cutting edges411in the insert1′.

In the present embodiment, the distance between the corner groove portion5apositioned closest to the third cutting edge43among three groove portions5and the third cutting edge43becomes smaller in comparison with the insert1in accordance with the first embodiment. In other words, the corner groove portion5ain accordance with the present embodiment is provided in such a manner as to be positioned closer to the third cutting edge43than the corner groove portion5ain the first embodiment mentioned above.

Further, in the first embodiment mentioned above, the two groove portions5including the corner groove portion5ais approximately the same in size, however, the corner groove portion5ais smaller in comparison with the other two groove portions5, in the present embodiment. In other words, in the first embodiment, the width and the depth of two groove portions5including the corner groove portion5aare approximately the same in the top view; however, the width and the depth of the corner groove portion5aare smaller than those of the other two groove portions5, in the present embodiment.

Accordingly, in the present embodiment, the convex portion6acorresponding to the corner groove portion5ais formed so as to be smaller in comparison with the other two convex portions6. Specifically, a width of the convex portion6aitself, and widths of the inclined center surface8of the convex portion6aand a pair of inclined side surfaces91and92are each smaller than those of the other two convex portions6.

It is possible to enhance a strength of the rake face area21in the vicinity of the third cutting edge43, by setting the corner groove portion5awhich is adjacent to the small cutting edge411aconnected to the third cutting edge43and the convex portion6acorresponding to the groove portion5asmaller than the other groove portions5or convex portions6, as mentioned above. Therefore, it is possible to inhibit the third cutting edge43to which a very great load is applied from chipping, since it is the cutting edge portion first coming into contact with the workpiece at a time of cutting.

As mentioned above, in the inserts1and1′ in accordance with two embodiments of the present invention, there is exemplified the insert in which the upper surface2is formed as the approximately square shape and four corners can be used as mentioned above; however, the insert is not limited to this, but the upper surface may be formed as the other shapes such as a rhomboid shape, a triangular shape and the like. In this case, since a reduction of a working cost can be achieved, it is desirable to use a plurality of corners such as the present embodiment.

Further, in the embodiment mentioned above, there is exemplified the embodiment in which two or three groove portions5each dividing the third cutting edge43are formed; however, the number of the groove portions5dividing the third cutting edge43may be set to one or more. In other words, the number of the groove portions5dividing the third cutting edge43can be appropriately selected in correspondence to the cutting length and the cutting condition of the third cutting edge.

Further, with regard to the shape of the groove portion5, in the embodiment mentioned above, there is exemplified the embodiment in which the groove portion5is formed so as to reach the lower surface from the upper surface; however, the structure is not limited to this, but may be made such that the lower end of the groove portion is positioned on the side surface3.

Further, in the embodiment mentioned above, there is exemplified the embodiment in which the number of the convex portion6provided in correspondence to the groove portion5is one; however, the structure is not limited to this, but may be made such that a plurality of convex portions6are provided in correspondence to one groove portion5. For example, the structure may be made such that a plurality of convex portions6are provided front and rear side by side in the rake face area21positioned in the inner side of the groove portion5, or may be made such that a plurality of convex portions6are provided right and left side by side in the rake face area21positioned in the inner side of the groove portion5.

Further, in the embodiments mentioned above, there is exemplified the embodiment having the flat inclined center surface8extending toward the inner side from the groove portion5side in the center of the convex portion6; however, the shape of the convex portion6is not limited to this. For example, it may be an approximately semispherical convex portion6constructed by a convex curved surface. Further, it may be a convex portion6having approximately the same surface as the upper surface of the center portion7. In other words, the convex portion6may be formed as far as it protrudes upward from the rake face area21in such a manner that the chip generated by the small cutting edge411is stably curled by the rake face area21, or by the rake face area21and the breaking groove71.

Cutting Tool

A cutting tool13is structured, as shown inFIG. 7, such that the insert1mentioned above is installed to a leading end of the holder14. In the present embodiment, the holder14is formed as a rod shape, specifically as a columnar shape. Further, the holder14has eight insert pockets12to which the insert1is installed. Accordingly, the cutting tool1is provided with eight inserts1.

Installed to the insert1is the first cutting edge41serving as a main cutting edge in such a manner as to protrude outward from an outer peripheral surface of the holder14. Further, the second cutting edge42serving as an auxiliary cutting edge is installed in such a manner as to protrude from a leading end surface of the holder14. Further, at this time, the second cutting edge42is arranged so as to be approximately vertical to an axis S of the holder14. In this case, in the insert1in accordance with the present embodiment, the first cutting edge1is arranged so as to be inclined in such a manner as to come away from a leading end toward a trailing end, with respect to the axis S of the holder14.

Since the cutting tool13is structured such as to be provided with the insert1mentioned above, it is possible to inhibit a plurality of chips divided finely in the width direction from coming into collision with each other. Accordingly, the chip discharging characteristic is improved and an improvement of a tool service life can be achieved.

In this case, in the present embodiment, the insert1is installed to the holder14via a seat member16. In accordance with the structure mentioned above, it is possible to reduce the chip of the holder14portion positioned in the chip portion of the cutting edge4, in the case that the chip of the cutting edge4of the insert1is generated. Therefore, it is possible to make a service life of the holder14long.

In this case, in the present embodiment, the insert1is screw fastened to the holder14by a thread member51.

Further, it is preferable that the insert1is installed to the holder14while having a positive axial rake. Accordingly, it is possible to achieve a further reduction of the cutting resistance. Therefore, it is possible to achieve an excellent cutting performance even under a severer cutting condition particularly such as a heavy cutting work having a great depth of cut.

In this case, in the present embodiment, there is exemplified the embodiment in which the seat member is interposed between the insert1and the holder14, at a time of installing the insert1to the holder14, while the structure may be made such that the insert1is directly brought into contact with the holder1.

Further, in the cutting tool in accordance with the present embodiment, the face mill cutter is exemplified, but the cutting tool can be applied to an end mill or the like without being limited to this.

Cutting Method

Finally, a description will be given of a cutting method of a workpiece in accordance with an embodiment of the present invention with reference toFIGS. 8(a) to8(c) by exemplifying the case that the rolling tool (the cutting tool13) mentioned above is used.

The cutting method of the workpiece in accordance with the present embodiment is provided with the following steps (i) to (iii).

(i) an step of moving the cutting tool13close to a workpiece100by rotating the cutting tool13in a direction of an arrow A around the axis S of the holder14and moving it in a direction of an arrow B, as shown inFIG. 8(a).

(ii) a step of cutting a surface of the workpiece100by bringing the cutting edge4of the insert1into contact with the surface of the workpiece100, and moving the cutting tool13in a direction of an arrow C, as shown inFIG. 8(b).

(iii) a step of keeping the cutting tool13away from the workpiece100by moving the cutting tool13in a direction of an arrow D, as shown inFIG. 8(c).

Accordingly, as mentioned above, since the excellent chip discharging characteristic is provided, and the material is worked by using the cutting tool13having a long tool service life, it is possible to achieve an improvement of a working efficiency and a finished surface precision. In other words, it is possible to inhibit the chip generated by the small cutting edge411from being clogged between the workpiece and the cutting tool13, and it is possible to suppress the chip of the cutting edge4and the groove portion5. As a result, it is possible to stably carry out the cutting work having a high working precision for a long term.

In this case, in the step (i) mentioned above, at least one of the cutting tool13and the workpiece100may be rotated. Further, the cutting tool13and the workpiece100may relatively come close, for example, the workpiece100may be moved close to the cutting tool13. In the same manner, in the step (iii) mentioned above, the workpiece100and the cutting tool13may relatively come away, for example, the workpiece100may be moved away from the cutting tool13. In the case of carrying over the cutting work, the step of bringing the cutting edge4of the insert1into contact with different positions of the workpiece100may be repeated while keeping the state in which the cutting tool13and/or the workpiece100are rotated. When the used cutting edge wears, an unused cutting edge may be used by rotating the insert1with respect to the center axis of the through hole15.

The embodiments in accordance with the present invention are exemplified above, however, it goes without saying that the present invention is not limited to the embodiments, but may be optionally structured without departing from the purpose of the invention.