Patent Description:
Patent Document <NUM> discloses an ultrahigh-pressure sintered body tool wherein: an ultrahigh-pressure sintered body <NUM>, consisting of a cBN sintered body or a diamond sintered body, is provided at a corner part of a cemented carbide material; the ultrahigh-pressure sintered body <NUM> is provided with a cutting edge <NUM>; an oil supply hole <NUM> is provided which has an ejection port 6b opened in a flank <NUM> located immediately below the edge corner part of the tool; and an inclination angle of the ejection port 6b with respect to the flank <NUM> is set at from <NUM>° or more to <NUM>° or less, whereby the extension of the life of the tool and an improvement in machined-surface quality are achieved.

Patent Document <NUM> discloses a cutting machining apparatus comprising: work rotating means <NUM> for rotating a cylindrical work <NUM> around a cylindrical axis; and cutting means <NUM> for cutting the rotating work <NUM> through contact therewith, wherein cutting means <NUM> comprises spraying means <NUM> for ejecting a spray medium M to a machined part <NUM> of the work <NUM>, whereby the machined part of the work is cooled efficiently so that the life of the cutting means is extended and whereby the removal of chips, etc. can be performed efficiently.

Patent Document <NUM> discloses a throwaway turning tool wherein: a sheet member <NUM> provided on an insert seat <NUM> formed at a leading end part of a tool body <NUM> is structured so as to have, in an upper surface part thereof, a groove part <NUM> and to be provided with notch parts <NUM>, <NUM> in the groove part <NUM>; and the tool body <NUM> is provided with a passage which communicates with a coolant supply part and the notch part <NUM>, as a result of which a throwaway tip is cooled effectively, thereby leading to improvements in edge life and machining accuracy.

However, no means for sufficiently cooling a cutting tip serving as a sintered body portion which constitutes a cutting edge has been provided so far. When a cutting tip is at a high temperature, this will cause, for example, the problems of deterioration in machining accuracy and of the wear of the cutting tip being likely to progress.

In view of the above, an object of the present invention is to provide a cutting insert where a cutting tip is cooled effectively so as to achieve an extended tool life.

An embodiment of the present invention will hereinafter be described with reference to the drawings. It should be noted that the same elements are denoted by the same symbols and will not be further explained. Further, the embodiment set forth below is illustrative in order to describe the present invention and is not intended to limit the present invention to such embodiment.

<FIG> is a perspective view of a cutting insert <NUM>, and <FIG> is a plan view seen from a direction facing an upper surface of the cutting insert <NUM>. The cutting insert <NUM> has a rhombic shape, in a plan view, with apex angles of <NUM>° and <NUM>°, an inscribed circle diameter of <NUM>, a thickness of <NUM> and a corner radius of <NUM>.

The cutting insert <NUM> comprises a base insert <NUM> and cutting tips <NUM> and <NUM>' which are fixed to two opposing apexes of the base insert <NUM> by means of brazing or the like.

The base insert <NUM> consists of a cemented carbide and includes an upper surface 12a (a first upper surface), a lower surface 12b (a first lower surface) and a side surface (a first side surface) connecting the upper surface 12a and the lower surface 12b. The side surface is constituted by: a mounting surface 12c (a first mounting surface) for mounting the cutting tip <NUM>; and a peripheral side surface 12d (a first peripheral side surface) which is connected to the upper surface 12a, the lower surface 12b and the mounting surface 12c and is exposed outward. Further, the base insert <NUM> is provided with a through hole 12e which penetrates the upper surface 12a and the lower surface 12b in a substantially perpendicular manner.

The cutting tips <NUM> and <NUM>' are mounted at the opposing apexes of the base insert <NUM>. The cutting tips <NUM> and <NUM>' are comprised of a cubic boron nitride sintered body (hereinafter referred to as a "cBN sintered body"). For instance, a heat resistant hard coating with a thickness of <NUM> may be formed on a surface of the cBN sintered body.

The cutting tip <NUM> includes an upper surface 14a (a second upper surface), a lower surface 14b (a second lower surface) and a side surface (a second side surface) connecting the upper surface 14a and the lower surface 14b. The side surface is constituted by: a mounting surface 14c (a second mounting surface) opposing the mounting surface 12c of the base insert <NUM>; and a peripheral side surface 14d (a second peripheral side surface) which is connected to the upper surface 14a, the lower surface 14b and the mounting surface 14c and is exposed outward. Further, provided at an edge 14e (an edge), which is formed by the upper surface 14a and the peripheral side surface 14d intersecting with each other, or which connects the upper surface 14a and the peripheral side surface 14d, are: two cutting edges <NUM> and <NUM>' (first cutting edges) which sandwich a corner part 14f; and a corner cutting edge which connects such cutting edges. The cutting tip <NUM>' has the same structure as the cutting tip <NUM>.

As shown in <FIG>, the base insert <NUM> and the cutting tip <NUM> are, in a plan view seen from a direction facing the upper surfaces 12a and 14a, provided so as to be in line symmetry with respect to a line L1 (a line) passing through the corner part 14f located on the edge 14e.

The upper surface 14a and the lower surface 14b have the same configuration, and the base insert <NUM> and the cutting edge <NUM> are provided so as to be in plane symmetry with respect to a reference plane located in the middle between a plane including the upper surface 12a (and the upper surface 12b) and a plane including the lower surface 12b (and the lower surface 14b). Therefore, the cutting insert <NUM> can achieve machining with the use of each of the following edges: the two cutting edges <NUM> (a forward direction) and <NUM>' (a backward direction) provided at the edge between the upper surface 14a and the peripheral side surface 14d; two cutting edges provided at an edge between the lower surface 14b and the peripheral side surface 14d; and four cutting edges provided similarly in the cutting tip <NUM>'. In addition, the lower surface 12b and the lower surface 14b are provided with the same configurations as those of the elements of the upper surface 12a and the upper surface 14a.

<FIG> is a cross-sectional view of the cutting insert <NUM>, the view being taken along a cross-section which includes the line L1 and is perpendicular to the upper surface 12a, the upper surface 14a, the lower surface 12b and the lower surface 14b.

As shown in <FIG>, at a boundary between the cutting tip <NUM> and the base insert <NUM>, a passage PA is formed which is constituted by passage parts PA1 through PA3.

When performing machining with the use of the cutting edge <NUM> or <NUM>' provided in the upper surface 14a of the cutting tip <NUM>, coolant C flows through the passage PA from the lower surface side to the upper surface side and absorbs heat generated in the cutting tip <NUM>, thereby leading to the facilitation of heat exhaust. Meanwhile, when performing machining either of the cutting edges provided in the lower surface 14b of the cutting tip <NUM>, the flow direction of the coolant C is opposite to the above-mentioned direction.

Herein, the passage PA is constituted by: the passage part PA3 which starts at a boundary between the lower surface 12b and the lower surface 14b and travels in a direction away from the cutting tip <NUM> or the peripheral side surface 14d; the passage part PA2 which is connected to the passage part PA3 and travels in a substantially perpendicular manner toward the upper surface 12a and the upper surface 14a; and the passage part PA1 which is connected to the passage part PA2 and travels in a direction toward the cutting tip <NUM> or the peripheral side surface 14d so as to be connected to a boundary between the upper surface 12a and the upper surface 14a.

<FIG> is a plan view illustrating a state in which the coolant C flows out of the passage part PA1.

As shown in <FIG>, in a plan view seen from the direction facing the upper surfaces 12a and 14a, the upper surfaces 12a and 14a are formed so as to be in line symmetry with respect to the line L1 passing through the edge 14e. Further, a line B1, which serves as a boundary line between the upper surface 12a and the upper surface 14a, or which serves as an edge between the upper surface 12a and the mounting surface 12c, is a line which is in line symmetry with respect to the line L1 and is a wavy line segment.

As to the boundary line B1, two ends connected to the peripheral surface are defined as points P2 and P2' (end points), and a point which is located as the middle point between the point P2 and the point P2' and where the boundary line B1 and the line L1 intersect with each other is defined as a point P1 (an intersection). At this time, a distance, in the line L1 direction, between each point on the boundary line B1 and the corner part 14f (an intersection between the line L1 and the edge 14e), has the relationship set forth below.

First, the distance, in the line L1 direction, between each point on the boundary line B1 and the corner part 14f, is constant within a predetermined distance from the middle point P1. That is, this line segment is perpendicular to the line L1. Then, the distance, in the line L1 direction, between each point on the boundary line B1 and the corner part 14f becomes longer, as such point moves away from the middle point P1, and such distance is at a maximum at a point P3 (a point P3'). Further, the distance, in the line L1 direction, between each point on the boundary line B1 and the corner part 14f becomes shorter, as such point moves away from the point P3 (the point P3') and becomes closer to the end point P2 (the end point P2').

Similarly, a passage P', which has the same structure as the passage PA, is formed at a boundary between the cutting tip <NUM>' and the base insert <NUM>. When performing machining with the cutting tip <NUM>', the coolant C flows through the passage P' and absorbs heat generated in the cutting tip <NUM>', thereby leading to the facilitation of heat exhaust.

<FIG> shows a cooling method with the coolant C which is employed when a work is machined by a cutting insert I serving as a comparative example. <FIG> shows a cooling method with the coolant C which is employed when a work is machined by the cutting insert <NUM> according to the present embodiment.

In a comparative example, the coolant C is ejected from only the outside of the cutting insert I. Therefore, in the first place, the amount of the coolant C which heads toward the area around the cutting edge is small, and most of such amount of the coolant C bounces off chips W from the work, and thus, the area around the cutting edge cannot be cooled efficiently. Further, constraints are placed on the mounting position and the orientation of a nozzle for ejecting the coolant C, thereby leading to a problem in that it is difficult to adjust the nozzle in order to achieve the appropriate position and angle.

Meanwhile, in the present embodiment, when the coolant C passes through the cutting insert <NUM>, the cutting tip <NUM> can be cooled directly. Further, due to a small amount of the chips W which obstruct the coolant C, the coolant C can be ejected efficiently toward the area close to a machining surface of the cutting tip <NUM>, thereby leading to the facilitation of cooling. Moreover, the coolant C collides with the back side of each of the chips W, and thus, the chips W can be forcedly separated from a rake surface, thereby leading to the suppression of crater wear. Furthermore, it is expected that, when the coolant C collides with the chips W, the chips W will be deformed, thereby leading to an improvement in chip control.

In particular, because the passage part PA1 on the outlet side of the coolant C travels in the direction toward the cutting tip <NUM> so as to be connected to a boundary part between the upper surface 14a and the upper surface 12a, the coolant C can be ejected closer to the surface to be machined.

The passage part PA3 on the inlet side of the coolant C starts from a boundary part between the lower surface 14b and the lower surface 12b and travels in the direction away from the cutting tip <NUM>, and thus, when any cutting edge on the lower surface 12b side is used for machining, the coolant C can be ejected toward a position near the cutting location. Therefore, the cooling of the cutting tip <NUM> is facilitated, whereby the extension of the life of the cutting insert <NUM> can be achieved. However, at the same time as when, as shown in <FIG>, the coolant C is ejected from the inside of the cutting insert <NUM>, the coolant C may be ejected additionally from the outside of the cutting insert <NUM>, as shown in <FIG>.

<FIG> is a perspective view of a base insert <NUM> before the cutting tip <NUM> is mounted thereon and integrated therewith. <FIG> is a perspective view of the same cutting tip <NUM>. <FIG> is a perspective view when the two elements are fixed to each other.

As shown in <FIG>, the mounting surface 12c on which the cutting tip <NUM> is mounted comprises: a securing surface <NUM> (a first securing surface) fixed to the cutting tip <NUM> via brazing or the like; and a passage surface 12f (a first passage surface) separate from and opposing the mounting surface 14c of the cutting tip <NUM>.

Further, as shown in <FIG>, the mounting surface 14c of the cutting tip <NUM> comprises: a securing surface 14c' fixed to the securing surface <NUM> of the base insert <NUM>; and a passage surface 14c" (a second passage surface) separate from and opposing the passage surface 12f and thereby forms part of an inner surface of the passage PA.

The securing surface <NUM> of the base insert <NUM> is a surface which passes through the line segment B1 shown in the plan view of <FIG> (the line segment passing through the middle point P1, the end points P2 and P2' and the points P3 and P3') and is perpendicular to the upper surface 12a and the lower surface 12b. Further, the passage surface 12f comprises, at a center part of the securing surface <NUM>, a surface dented inward, i.e., in the direction away from the cutting tip <NUM>.

Meanwhile, as shown in <FIG>, the upper surface 14a of the cutting tip <NUM> comprises: a rake surface <NUM>; and a guiding surface 14i which is connected to the rake surface <NUM> and is dented in the direction of the lower surface 14b and connected to the passage PA. The rake surface <NUM> is not necessarily a flat surface, and may be flat so as to be capable of functioning as a rake surface or may be provided with a chip breaker. The securing surface 14c' and the passage surface 14c" are included in a plane perpendicular to the reference plane.

As shown in <FIG>, when the cutting tip <NUM> is mounted on the base insert <NUM>, each of the upper surface 14a and the lower surface 14b is provided with the guiding surface 14i such that either an upper end of the passage surface 12f or a lower end thereof is exposed, whereby an opening OP which communicates with the passage PA can be formed in each of the upper surface 14a and the lower surface 14b.

Herein, the angle of the passage surface 12f relative to the securing surface <NUM> and the angle of the guiding surface 14i are adjusted, whereby the ejection angle and ejection position of the coolant C can be adjusted. For example, in an inner surface of the passage surface 12f, a downward surface which forms the passage part PA1 and an upward surface which forms the passage part PA3 (an upward surface and a downward surface) may each be provided so as to form an angle close to <NUM>° with respect to the passage part PA2, whereby the ejection angle of the coolant C can be made close to parallel to the rake surface.

Serration connection is established between the cutting tip <NUM> and the base insert <NUM> at the surface where they are fixed to each other. Therefore, the adhesion (dynamic adhesion) can be enhanced by increasing the area of such securing surface. Further, securing can be maintained with respect to an external force in a lateral direction (a direction perpendicular to the line L1).

As described above, according to the present embodiment, the passage PA is provided which is formed along a boundary surface between the cutting tip <NUM> and the base insert <NUM> so as to extend from the boundary part, in the upper surface of the cutting insert <NUM>, between the cutting tip <NUM> and the base insert <NUM> to the boundary part, in the lower surface of the cutting insert <NUM>, between the cutting tip <NUM> and the base insert <NUM>. From the above, while the entire respective opposing surfaces of a base insert and a cutting tip are originally desired to be fixed to each other in order to ensure a sufficient adhesion force (dynamic adhesion), the present embodiment is intentionally configured such that parts of the above respective surfaces form the passage for the coolant C. Therefore, heat exhaust of the cutting tip can be facilitated also at the boundary between the base insert and the cutting tip.

Further, as described above, an increased amount of the coolant C can be ejected to the area around the machining part, and thus, the cooling of the cutting tip <NUM> can be facilitated. Moreover, the coolant C is ejected to the back side of each chip, whereby the discharging of chips can also be facilitated.

The embodiment described above is intended to facilitate the understanding of the present invention, and is not intended to allow for the present invention to be interpreted in a limited manner. For instance, such embodiment can be used for a cutting insert comprising cutting tips comprised of something other than a cBN sintered body (for example, a diamond sintered body). Further, the technical idea indicated in the present embodiment is applicable to cutting tools other than turning tools. Such technical idea is also applicable to a negative or positive-type cutting tip having, in a plan view, a triangular shape, a hexagonal shape, any other polygonal shape, a round shape or the like. Moreover, the base insert <NUM> and the cutting tip <NUM> may be provided so as to be in rotational symmetry with respect to the through hole 12e or may be provided so as to be in axial symmetry with respect to a line perpendicular to the axis of the through hole 12e (that is, the upper surface 12a and the lower surface 12b can be used in a reverse state). Furthermore, the edge 14e (the edge) connecting the upper surface 14a and the peripheral side surface 14d may include a honed region.

The passage PA is not limited to being constituted by a single passage but may be constituted by multiple passages. The passage PA may be configured so as to branch out, at some middle point thereof, into multiple passages. Further, the base insert and the cutting tip may not necessarily be flush with each other. Depending on the use, a configuration may be employed in which the upper surface 14a of the cutting tip protrudes with respect to the upper surface 12a of the base insert.

The elements of the embodiment as well as the arrangements, materials, conditions, shapes, sizes, etc. thereof are not limited to those illustrated and may be changed as appropriate.

In addition, it is possible to employ a cutting insert which does not comprise part of the configuration of the present embodiment or any of the other embodiments; alternatively, it is possible to replace part of the configuration of an embodiment with part of the configuration of another embodiment or to incorporate part of the configuration of an embodiment into the configuration of another embodiment.

Description will be made below regarding the configuration of a holder <NUM> (a tool body) for holding the cutting insert <NUM> according to the above embodiment and the configuration of a metal spacer <NUM>.

As shown in <FIG>, the holder <NUM> comprises: a rod-shaped shank part <NUM> which is comprised of chrome molybdenum steel and has a quadrangular shape in its cross-section; and an insert seat 16C provided in a recessed manner at a leading-end side corner part of the holder <NUM>.

The insert seat 16C has, in a plan view, the same substantially rhombic shape as the cutting insert <NUM>. The insert seat 16C comprises an upward seating surface 16D and two wall surfaces 16E which stand up with respect to the seating surface 16D and are substantially perpendicular to the seating surface 16D.

The seating surface 16D is provided with a screw hole (not shown) for fixing the metal spacer <NUM> (which may be referred to, for example, as a shim) to be placed on the seating surface, and the metal spacer <NUM> can be fixed to the seating surface 16D through a screw.

The holder <NUM> is provided with a screw hole 16F for a clamp screw <NUM> for fixing, with a presser bar <NUM>, the cutting insert <NUM> to be placed on the metal spacer <NUM>. The holder <NUM> is further provided with, in one of the wall surfaces 16E, a supply port <NUM> for supplying the coolant C to the cutting insert <NUM> via a groove part 18A (a coolant passage) formed in the metal spacer <NUM>.

The metal spacer <NUM> has the same rhombic shape as the cutting insert <NUM> in a plan view, and the metal spacer <NUM> is designed such that two side surfaces thereof adhere to the two wall surfaces 16E of the insert seat 16C when the metal spacer <NUM> is fixed and that, in a plan view, the other two side surfaces thereof slightly protrude from end surfaces of the holder <NUM>. Further, in order to supply the coolant C, the metal spacer <NUM> is provided with the groove part 18A which has one end communicating with the supply port <NUM> provided in the holder <NUM> and another end, when the cutting insert <NUM> is mounted, communicating with the passage part PA3 of the cutting insert <NUM>. Moreover, the metal spacer <NUM> is provided with, at a center part thereof, a through hole 18B for allowing a screw to pass therethrough, such screw being screwed into a screw hole 18C formed in the seating surface 16D. An opening of the through hole 18B is provided in a tapered shape such that the head of a screw stops.

<FIG> is a perspective view showing a state in which the presser bar <NUM> fixes the metal spacer <NUM> and the cutting insert <NUM> mounted on the metal spacer <NUM>.

As shown in <FIG>, the upper surface 12a of the base insert <NUM> of the cutting insert <NUM> is fixed to the seating surface 16D of the holder <NUM> via the metal spacer <NUM> by means of the presser bar <NUM> fixed, with the clamp screw <NUM>, to the holder <NUM>. At this time, the two wall surfaces of the metal spacer <NUM> and two surfaces included in the peripheral side surface 12d of the base insert <NUM> are fixed, through contact, to the two wall surfaces 16E.

The coolant C is supplied from a lower part of the holder <NUM>. The lower part of the holder <NUM> is provided with a hole <NUM> which communicates with the supply port <NUM>. The coolant C which has passed through the holder <NUM> via the hole <NUM> is supplied from the supply port <NUM> through the groove part 18A of the metal spacer <NUM> to the passage PA of the cutting insert <NUM>.

With the use of the holder <NUM> and metal spacer <NUM> described above, it is possible to cool the cutting tip effectively and thereby achieve the extension of tool life.

Description will be made below regarding variations of the cutting insert <NUM> according to the first embodiment. It should be noted that, with regard to the parts of the same structures or functions as those of the first embodiment, description thereof is omitted or simplified here.

<FIG> is a perspective view of a cutting insert <NUM> according to the variation. The cutting insert <NUM> is different from the cutting insert <NUM> according to the first embodiment with respect to the point of comprising a base insert <NUM> and a cutting tip <NUM>.

The base insert <NUM> comprises: an upper surface 26a; a lower surface 26b; a mounting surface 26c on which the cutting tip <NUM> is mounted; and a peripheral side surface 26d connected to the upper surface 26a, the lower surface 26b and the mounting surface 26c.

As shown in <FIG>, the peripheral side surface 26d of the base insert <NUM> is provided with, in an intermediate part between the upper surface 26a and the lower surface 26b, an inclined surface facing toward the upper surface 26a and an inclined surface facing toward the lower surface 26b as well as a side surface part 26d' connected to such inclined surfaces so as to extend over two continuous sides of a rhombic shape. Similarly, the peripheral side surface 26d of the base insert <NUM> is provided with an inclined surface facing toward the upper surface 26a and an inclined surface facing toward the lower surface 26b, as well as a side surface part 26d" connected to such inclined surfaces so as to extend over the other two sides of the rhombic shape.

The side surface parts <NUM>' and 26d" are provided as described above. Thus, in order to mold the cutting insert <NUM>, when performing, in a die, pressing with an upper-surface side punch of a cutting insert and a lower-surface side punch thereof, leading end parts in the outer peripheries of the two punches are made flat in order to mold the side surface parts <NUM>' and 26d". Therefore, compared with the case where leading ends of two punches are made sharp without providing the side surface parts <NUM>' and 26d", punches, being used as components of a mold, can be made resistant to chipping. Further, the inclined surface facing toward the upper surface 26a presses the cutting insert <NUM>, whereby the lifting of the cutting insert <NUM> during machining can be suppressed effectively. Moreover, the base insert <NUM> can be decreased in thickness, whereby the manufacturing cost can be reduced.

<FIG> is a perspective view of the cutting tip <NUM> according to the variation. <FIG> shows a state in which the cutting tip <NUM> is mounted on the base insert <NUM>.

As shown in <FIG>, the cutting tip <NUM> differs from the cutting tip <NUM> in terms of the shape of a guiding surface 28i leading to a flat part <NUM>. More specifically, a surface of the guiding surface 28i is provided with irregularities in a direction perpendicular to the flow direction of the coolant C. Such irregularities can be formed through, by way of example, laser machining.

The formation of such irregularities on the surface can increase the contact area between the coolant C and the cutting tip <NUM>, whereby the cooling of the cutting tip <NUM> can be facilitated more effectively.

<FIG> shows a metal spacer <NUM> according to the variation. The metal spacer <NUM> differs from the metal spacer <NUM> with respect to the point of comprising a through hole 30A for supplying the coolant C rather than the groove part 18A. More specifically, the metal spacer <NUM> is provided with: a through hole 30B (a first through hole) for allowing a screw to pass therethrough, such screw being provided at a center part of the metal spacer <NUM> and intended to fix the metal spacer <NUM> to a holder; and the through hole 30A for supplying the coolant C to the passage PA of the cutting insert <NUM> (or the cutting insert <NUM>). The through hole 30A is formed such that, when the cutting insert <NUM> is placed, the through hole 30A is shifted from the position of the passage part PA3 of the cutting insert <NUM>. Therefore, the coolant C supplied from a lower surface of the metal spacer <NUM> is decelerated through collision with the lower surface 12b of the base insert <NUM> and is then supplied to the cutting insert <NUM> via a liquid reservoir 30C. The above configuration allows air bubbles, etc. to be less likely to stay in the passage of the cutting insert <NUM>, whereby cooling is less likely to be inhibited. Further, even a cutting insert in which the openings of a passage are formed at locations different from those of the cutting insert <NUM> can communicate with the through hole 30A via the liquid reservoir 30C, and thus, the metal spacer <NUM> is applicable to various cutting inserts which are each provided with a coolant passage at a location different from that involved in the cutting insert <NUM>.

As described above, the cutting insert according to the above embodiment and the relevant metal spacer and holder allow a cutting tip to be cooled effectively, thereby leading to the extension of tool life.

It should be noted that no limitations are placed on the method for fixing the cutting insert <NUM> through a holder, and various types of means may be employed for such fixation. An example of such fixation method is one involving the use of a presser piece, and further, the fixation of the cutting insert <NUM> can be performed through screwing, a lever, a wedge, an eccentric pin or the like.

Claim 1:
A cutting insert (<NUM>) comprising:
a base insert (<NUM>) comprising a first upper surface (12a), a first lower surface (12b) and
a first side surface connecting the first upper surface and the first lower surface; and
a cutting tip (<NUM>) comprising a second upper surface (14a), a second lower surface (14b) and a second side surface connecting the second upper surface and the second lower surface, wherein:
the first side surface comprises:
a first mounting surface (12c) opposing the second side surface; and
a first peripheral side surface (12d) connected to the first upper surface, the first lower surface and the first mounting surface;
the second side surface comprises:
a second mounting surface (14c) opposing the first mounting surface; and
a second peripheral side surface (14d) which is connected to the second upper surface, the second lower surface and the second mounting surface and in which at least an edge connected to the second upper surface is provided with a first cutting edge (<NUM>, <NUM>'), wherein
the first mounting surface comprises:
a first securing surface (<NUM>) secured to the second mounting surface; and
a first passage surface (12f) separate from and opposing the second mounting surface; and
the first passage surface, and, in the second mounting surface, a second passage surface (14c") opposing the first passage surface, form a passage (PA) which communicates with the second upper surface and the second lower surface and is intended to allow coolant for cooling the cutting tip to pass therethrough,
characterised in that the passage is constituted by a first passage part (PA3) which starts at a boundary between the first lower surface and the second lower surface and travels in a direction away from the second peripheral side surface;
a second passage part (PA2) which is connected to the first passage part and travels in a substantially perpendicular manner toward the first upper surface and the second upper surface; and
a third passage part (PA1) which is connected to the second passage part and travels in a direction toward the second peripheral side surface so as to be connected to a boundary between the first upper surface and the second upper surface.