Double-sided circular cutting insert and indexable rotary cutting tool

In a circular cutting insert of the present invention, the upper side surface and the lower side surface each include: a plurality of planar restraining faces which are disposed sequentially in a circumferential direction of the upper side surface and the lower side surface so as to interpose a joint portion between each of the planar restraining faces and each have a side disposed on the side surface-intermediate line (N); and a plurality of antivibration restraining faces which are each disposed between two planar restraining faces adjacent through the joint portion and each include an inclined face, and the restraining faces of the lower side surface are disposed so as to be shifted with respect to the restraining faces of the upper side surface by a predetermined angle (α) around a central axis of a screw insertion hole.

TECHNICAL FIELD

The present invention relates to a cutting insert which is detachably attached to an indexable rotary cutting tool for performing milling and an indexable rotary cutting tool to which the cutting insert is attached, and particularly, to a double-sided circular cutting insert and an indexable rotary cutting tool having a means of preventing occurrence of vibrations during a cutting operation of a workpiece.

Priority is claimed on Japanese Patent Application No. 2015-129520, filed on Jun. 29, 2015, the content of which is incorporated herein by reference.

BACKGROUND ART

In a cutting insert formed into a circular shape in a planar view, that is, in a so-called a circular (round) cutting insert, a top surface as a rake face and a bottom surface formed at a position opposite to the top surface are formed into circular shapes, a side surface connecting the top surface and the bottom surface to each other is formed into an approximately columnar shape or an approximately conical shape, and cutting edges are provided in some or all of ridgeline at which the side surface intersects with the top surface. In addition, in a double-sided cutting insert formed in a circular shape, cutting edges are also provided on ridgeline at which the bottom surface and the side surface intersect with each other.

In a case where the cutting insert formed into a circular shape (hereinafter, referred to as a “circular cutting insert”) is attached to an insert mounting seat provided on a tool main body of the indexable rotary cutting tool and is fixed to the insert mounting seat by tightening a clamp screw, and a cutting operation of a workpiece is performed, there are the following tasks (1) to (3), and in the related art, solutions with respect to the tasks are suggested.

In the circular cutting insert, cutting edges formed into a circular shape are provided on the ridgeline at which the top surface intersects with the side surface or the ridgelines at which the top surface and the bottom surface intersect with the side surface, and thus, it is necessary to effectively use the regions of the cutting edges. Accordingly, whenever the circular cutting insert is reattached to the insert mounting seat of the tool main body, it is necessary to accurately position the circular cutting insert so as to fix the circular cutting insert to the tool main body by tightening the clamp screw (an indexing function is required). Particularly, when a portion (cutting edge portion) of the cutting edges used during the cutting operation wears out, in order to use an unused portion during the cutting operation the next time, the circular cutting insert is rotated about a center of a circle of the cutting edges by a predetermined angle. Accordingly, in a state where the positions of the cutting edges are shifted, the circular cutting insert is reattached to the insert mounting seat. In the reattachment of the cutting edges, it is necessary to attach the circular cutting insert to the insert mounting seat in a state where the unused cutting edges are accurately positioned without erroneous operations.

Even when the circular cutting insert is firmly fixed to the insert mounting seat, the cutting insert is easily displaced by a cutting force loaded to the cutting insert during a cutting operation of a workpiece. The reason for this is that the circular cutting insert is fixed to the insert mounting seat of the tool main body by tightening the clamp screw; however, the side surface of the circular cutting insert is formed into a columnar shape (cylindrical shape) or a conical shape, and thus, a reaction force with respect to the cutting force during the cutting operation acts as a force trying to rotate the circular cutting insert about the clamp screw (a turning force about the clamp screw). If the circular cutting insert fixed to the insert mounting seat is rotated by the turning force (rotational moment) and the fixed position thereof is slightly shifted, machining accuracy of a machined surface of the workpiece deteriorates, vibrations are generated, abnormal wear of the cutting edges occurs, and thus, the cutting edges are damaged. Accordingly, in the indexable rotary cutting tool to which the circular cutting insert is attached, a function for preventing turning (or rotation) of the circular cutting insert during the cutting operation (antirotation function) is required.

In general, when a workpiece is cut using the indexable rotary cutting tool to which the cutting insert is attached, the cutting force acting on the cutting insert is applied in a direction of pressing the cutting edge portion (a portion of the cutting edge used for cutting) from the top surface to the insert mounting seat of the indexable rotary cutting tool. In addition, in the cutting insert, a stress acting on the cutting edge portion and a repulsive force with respect to the stress are generated. During a cutting operation in a normal state, the stress acting on the cutting edge portion and the repulsive force with respect to the stress mainly act on the clamp screw by which the cutting insert is fixed to the tool main body.

However, in a transient state during the cutting operation, if the stress acting on the cutting edge portion and the repulsive force with respect to the stress are not balanced with each other, vibrations may occur. The transient state during the cutting operation indicates a moment when the cutting edge bites into the workpiece, or the like. The clamp screw is loosened or the installation (attachment) position of the cutting insert with respect to the insert mounting seat is displaced by the vibrations, and thus, a so-called displacement of the cutting insert may occur. If the vibrations and the displacement of the cutting insert occur, the cutting edge is damaged, and there are problems that favorable machining accuracy and improved machined surface roughness with respect to the workpiece cannot be obtained. In addition, there is a disadvantage that noise occurs during the cutting operation.

Moreover, in recent years, in order to improve machining efficiency with respect to a workpiece, a high-speed cutting operation is required. If the high-speed cutting operation is performed, when the cutting edge of the cutting insert bites into a workpiece, vibrations are likely to be generated by the impact. Accordingly, in order to realize the high-speed cutting operation in the indexable rotary cutting tool to which the circular cutting insert is attached, it is very important to provide a function for preventing or suppressing occurrence of the vibrations (antivibration function).

In the indexable rotary cutting tool to which the circular cutting insert is attached, among the above-described tasks (1) to (3), an improvement plan for the tasks (1) and (2) are proposed by many patent applications in the related art. However, there are few suggestions with respect to an improvement plan for the task (3) in addition the tasks (1) and (2). The reason for this is that a favorable improvement plan for the tasks (1) and (2) is based on a technical idea that vibrations are not generated during the cutting operation.

For example, the improvement plans for the tasks (1) and 2 are suggested by PTL 1 to PTL 3 below.

PTL 1 (Japanese Unexamined Patent Application, First Publication No. 2011-245585) suggests that in a positive round cutting insert, the cutting insert for increasing reliability of fixing with respect to an insert mounting seat and a cutting tool using the cutting insert. In the invention described in PTL 1, a plurality of planar indexing surfaces of which inclination angles are larger than the inclination angle of a side surface of the cutting insert are provided on the side surface at constant pitches in a circumferential direction, a vertically long protrusion is provided at a center portion of each of the indexing surfaces in the circumferential direction, the protrusion is inserted to engage with a recessed portion provided on a seating side surface (wall surface) of an insert mounting seat of a tool main body, and in this state, the indexing surfaces positioned at different positions abut on a plurality of seating side surfaces. Accordingly, the cutting insert is positioned on the insert mounting seat, and rotation of the cutting insert is prevented. In addition, PTL 1 describes that in the cutting tool, an indexing number of the cutting edges of the cutting insert is set to four, two seating side surfaces whose directions are different from each other by 90 degrees are formed on the insert mounting seat of the tool main body, and the adjacent indexing surfaces of the cutting insert are restrained by two seating site surfaces.

PTL 2 (Published Japanese Translation No. 2012-525268 of the PCT International Publication) suggests a double-sided cutting insert formed into a circular shape and a cutting tool using the cutting insert. The cutting insert described in PTL 2 has a configuration in which a plurality of antirotation surfaces substantially perpendicular to a top surface and a bottom surface are provided in a circumferential direction of a side surface of the cutting insert. Meanwhile, protrusion surfaces which are aligned with the antirotation surface of the cutting insert and prevent the rotation of the cutting insert, are provided on a pocket side surface (a wall surface provided on the insert mounting seat) of the tool main body. Accordingly, a wide attachment area is secured between the cutting insert and the cutting tool to prevent the rotation of the cutting insert.

PTL 3 (Specification of U.S. Pat. No. 6,607,335) suggests an invention which relates to a cutting insert attached to an indexable rotary cutting tool and the cutting tool. The cutting tool described in PTL 3 does not adopt the indexing means and the antirotation means of the cutting insert described in PTLs 1 and 2. That is, the means of restraining the rotation restraining faces formed on the side surface of the cutting insert or the protrusions of the rotation restraining faces, is not provided on a restraining wall surface erected to the seating surface provided on the insert mounting seat of the tool main body. However, FIG. 14 of PTL 3 shows an embodiment of a cutting insert, in which the center of the side surface of the double-sided circular cutting insert is a ridgeline at which the side surface and a base surface (intermediate plane M) of the cutting insert intersect with each other, and the side surface each between the ridgeline and the top surface and between the ridgeline and the bottom surface includes eight planes sequentially connected along the ridgeline to have an octagonal cross-section.

PTL 4 and PTL 5 suggest inventions relating to a cutting tool having a means of preventing occurrence of vibrations in the indexable rotary cutting tool to which the circular cutting insert is attached.

PTL 4 (Japanese Unexamined Patent Application, First Publication No. 2012-206249) suggests an invention relating to a double-sided circular cutting insert for preventing occurrence of vibrations caused by loosening of a tightening screw in an antirotation mechanism which can be easily and inexpensively manufactured. The circular cutting insert suggested in PTL 4 includes a plurality of dimples (recessed portions) formed on the top surface and a plurality of other dimples formed on the bottom surface facing the top surface to be capable of an indexing. The cutting insert is removably accommodated in an insert accommodation pocket of the tool main body, and the insert accommodation pocket includes a single protrusion which can be accommodated in one of the plurality of dimples. Therefore, according to cooperation of the protrusion of the insert accommodation pocket and one of a plurality of dimples of the cutting insert, the indexing of the round cutting insert attached to the insert accommodation pocket can be performed, and the rotation of the cutting insert during the cutting operation is prevented. As the effect thereof, PTL 4 describes that a mechanism for preventing occurrence of vibrations caused by the loosening of the tightening screw is provided.

PTL 5 (Published Japanese Translation No. 2002-527251 of the PCT International Publication) suggests an invention relating to an antirotation attachment mechanism of a circular cutting insert including an antirotation means of the circular cutting insert and an antivibration means thereof. PTL 5 states that the antirotation attachment mechanism includes a plurality of curved stopping surfaces inclined to a cylindrical side surface of the cutting insert around the cylindrical side surface and an antirotation surface which forms an interference fit joint surface engaging with the inclined disposition portion of the curved stopping surface of the cutting insert in one line contact manner on the insert mounting seat (pocket) of the tool main body. In addition, PTL 5 states that the side surface of the pocket includes a semicircular upper portion for coming into direct contact with the upper side wall of the cutting insert.

In addition, Specification of PTL 5 describes that “a supporting contact between an upper portion 60 of a pocket side surface 50 and an upper side wall 64 of an insert 3 is important for two reasons. Firstly, most of lateral vibration loads applied to the insert 3 are absorbed by a wide range of semicircular contact between the side surface 50 of the pocket 5 and the upper portion 60 of the insert side wall 21 during the cutting operation in order to protect the antirotation mechanism 1 from the vibration loads. Secondly, according to this configuration, most of the lateral vibrations concentrate on the strongest portion of the insert 3, that is, the upper side wall 64 which has the largest diameter of the insert and in which a material of an insert main body is little or not removed at all since the curved stopping surfaces 35 are provided”. That is, PTL 5 describes that the supporting contact between the upper portion 60 of the pocket side surface 50 and the upper side wall 64 of the insert 3 absorbs lateral vibrations occurring during the cutting operation.

CITATION LIST

Patent Literature

[PTL 2] Published Japanese Translation No. 2012-525268 of the PCT International Publication

[PTL 5] Published Japanese Translation No. 2002-527251 of the PCT International Publication

SUMMARY OF INVENTION

Technical Problem

With respect to the above-described task of the circular cutting insert, as described in PTL 1, the cutting insert and the cutting tool using the same include the configuration to solve the indexing function (task (1)) and the antirotation function (task (2)). However, in PTL 1, the solution with respect to the antivibration function (task (3)) is not described. In addition, the cutting insert described in PTL 1 does not include the configuration of the double-sided cutting insert in a positive circular cutting insert.

As described in PTL 2, in the double-sided cutting insert formed into a circular shape and the cutting tool using the same, the plurality of antirotation surface substantially perpendicular to the top surface and the bottom surface are provided in the circumferential direction of the side surface of the cutting insert, and the protrusion surface which is aligned with the antirotation surface and prevents the rotation of the cutting insert is provided on the pocket side surface (the wall surface provided on the insert mounting seat) of the tool main body. Accordingly, the indexing function and the antirotation function are provided in the double-sided circular cutting insert. However, similarly to PTL 1, the cutting insert and the cutting tool do not have the antivibration function.

As shown in FIG. 14 of PTL 3, the circular cutting insert includes two side surfaces between the ridgeline and the top surface and between the ridgeline and the bottom surface with respect to the ridgeline portion at which the side surface and the base surface (M) intersect with each other, and each side surface is formed by connecting eight planar side faces sequentially in the direction of the ridgeline and has an octagonal cross-section. In addition, FIG. 14 of PTL 3 shows that the joint portion of the planar side faces adjacent in the direction of the ridgeline forms the corner (corner portion) protruding toward the outside of the cutting insert.

However, in the circular cutting insert described in PTL 3, an insertion hole penetrating from the top surface to the bottom surface is not a hole into which the clamp screw is inserted and which is formed so as to fix the circular cutting insert to the seating surface of the insert mounting seat. In addition, as shown in FIG. 5 of PTL 3, the fixing of the circular cutting insert adopts the means of allowing the tip portion of the clamp screw to engage with a clamp surface formed around the insertion hole of the top surface of the circular cutting insert. Accordingly, the double-sided circular cutting insert described in PTL 3 is not the circular cutting insert having the means of performing indexing and antirotation by attaching the circular cutting insert to the insert mounting seat of the tool main body by tightening the clamp screw inserted into the screw insertion hole. In addition, PTL 3 does not describe that the cutting tool and the cutting insert have an antivibration means.

In the double-sided circular cutting insert described in PTL 4, the plurality of dimples (recessed portions) are formed on the top surface and the bottom surface, and the single protrusion accommodated in one of the plurality of dimples of the top surface and the bottom surface is provided in the insert accommodation pocket of the tool main body. Accordingly, the indexing of the round cutting insert can be performed, the rotation of the cutting insert is prevented during the cutting operation, and as a result, occurrence of vibrations caused by loosening of the tightening screw is prevented. However, the side surface of the round cutting insert is configured in a circular shape (columnar shape), and thus, the side surface does not have a configuration in which the plurality of planar side faces are connected with each other in the circumferential direction.

In the antirotation attachment mechanism of the round cutting insert described in PTL 5, the plurality of curved stopping surfaces are provided around the cylindrical side surface of the cutting insert, and the antirotation surface is provided, which forms the interference fit joint surface engaging with the inclined disposition portion of the curved stopping surface of the cutting insert in one line contact manner on the insert mounting seat (pocket) of the tool main body. Accordingly, the indexing function and the antirotation function are exerted. In addition, the side surface of the pocket includes a semicircular upper portion for coming into direct contact with the upper side wall of the cutting insert, and thus, most of the lateral vibration loads applied to the cutting insert are absorbed.

The indexing function and the antirotation function of the cutting insert described in PTL 5 are exerted by the configuration in which the plurality of curved stopping surfaces are disposed from the intermediate portion of the side surface toward the bottom surface at equal intervals on the side surface formed into a circular shape.

In addition, PTL 5 describes that vibrations are absorbed by the configuration including the semicircular upper portion for causing the side surface of the pocket to come into direct contact with the upper side wall of the cutting insert. However, the cutting insert and the pocket described in PTL 5 have room for improvement.

Accordingly, in the circular cutting insert and the indexable rotary cutting tool to which the cutting insert is attached, an object of the present invention is to provide a double-sided circular cutting insert having a means of increasing indexing accuracy of the cutting insert with respect to a tool main body, preventing the rotation of the cutting insert during a cutting operation, and preventing occurrence of vibrations, and an indexable rotary cutting tool to which the cutting insert is detachably attached.

Solution to Problem

The present invention includes the following aspects.

(1) A double-sided circular cutting insert including: a top surface and a bottom surface configured to be detachably attached to an insert mounting seat and formed into a circular shape in a planar view of the circular cutting insert; a side surface connecting the top surface and the bottom surface; a screw insertion hole penetrating from the top surface to the bottom surface; and cutting edges formed on intersecting ridgelines at which the top surface and the bottom surface intersect with the side surface, in which

when a plane bisecting the circular cutting insert in a thickness direction is referred to as an intermediate plane (M) of the circular cutting insert, an imaginary ridgeline at which the intermediate plane (M) intersects with the side surface is referred to as a side surface-intermediate line (N), the side surface between the side surface-intermediate line (N) and the top surface is referred to as an upper side surface, and the side surface between the side surface-intermediate line (N) and the bottom surface is referred to as a lower side surface,

the upper side surface and the lower side surface each include:

a plurality of planar restraining faces disposed sequentially in a circumferential direction of the upper side surface and the lower side surface so as to interpose a joint portion between each of the planar restraining faces, each planar restraining face having a side disposed on the side surface-intermediate line (N), and

a plurality of antivibration restraining faces, each antivibration restraining face being disposed between two planar restraining faces adjacent through the joint portion, and comprising an inclined face which has an apex portion at an end portion of each of the joint portions closer to the side surface-intermediate line (N) and a side disposed on the side surface-intermediate line (N) and tilts from the apex portion to the side so as to have a length in the circumferential direction of the side surface gradually increasing from the apex portion to the side surface-intermediate line (N),

the planar restraining faces and the antivibration restraining faces of the lower side surface are disposed so as to be shifted with respect to the planar restraining faces and the antivibration restraining faces of the upper side surface by a predetermined angle (α) around a central axis of the screw insertion hole, and

the planar restraining faces and the antivibration restraining faces of the upper side surface and the lower side surface are configured to be restrained by a restraining wall surface provided on the insert mounting seat when the circular cutting insert is attached to an indexable rotary cutting tool.

(2) The double-sided circular cutting insert described in the above (1), wherein

the side of each of the planar restraining faces of the upper side surface disposed on the side surface-intermediate line (N) is also the side of each of the antivibration restraining faces of the lower side surface disposed on the side surface-intermediate line (N), and

the side of each of the planar restraining faces of the lower side surface disposed on the side surface-intermediate line (N) is also the side of each of the antivibration restraining faces of the upper side surface disposed on the side surface-intermediate line (N).

(3) The double-sided circular cutting insert described in the above (1) or (2), wherein

the sides of the planar restraining faces disposed on the side surface-intermediate line (N) and the sides of the antivibration restraining faces disposed on the side surface-intermediate line (N) have the same length and are alternately connected with each other along the side surface-intermediate line (N).

(4) The double-sided circular cutting insert described in any one of the above (1) to (3), wherein

each of the joint portions has a predetermined width in the circumferential direction of the side surface, and

each of the antivibration restraining faces is formed into an isosceles trapezoid when the circular cutting insert is viewed from the side surface, and the isosceles trapezoid has an upper base which is the apex portion of each of the joint portions, and a lower base which is the side disposed on the side surface-intermediate line (N).

(5) The double-sided circular cutting insert described in any one of the above (1) to (3), wherein

each of the joint portions comprises a joint ridgeline which is a ridgeline formed by sides of two adjacent planar restraining faces which face each other, and

each of the antivibration restraining faces is formed into an isosceles triangle or an equilateral triangle when the circular cutting insert is viewed from the side surface, the isosceles triangle and the equilateral triangle have an apex which is an end of the joint ridgeline closer to the side surface-intermediate line (N), and a base corresponding to the apex which is the side disposed on the side surface-intermediate line (N).

(6) The double-sided circular cutting insert described in any one of the above (1) to (5), wherein

in a longitudinal section of the circular cutting insert passing through a central axis of the screw insertion hole, a ridgeline of each of the antivibration restraining faces is linear, convex, or concave.

(7) The double-sided circular cutting insert described in any one of the above (1) to (6), wherein

each of the joint portion and each of regions in the adjacent two planar restraining faces in a predetermined range from the joint portion in the circumferential direction of the side surface are formed into an antirotation surface as a corner portion, and

the antirotation surface is configured to be restrained by the restraining wall surface provided on the insert mounting seat as a means of preventing the circular cutting insert from rotation when the circular cutting insert is attached to an indexable rotary cutting tool.

(8) The double-sided circular cutting insert described in any one of the above (1) to (7), wherein

an outline of a cross-section of the circular cutting insert along the intermediate plane (M) is formed into a regular polygon.

(9) The double-sided circular cutting insert described in any one of the above (1) to (8), wherein

the upper side surface and the lower side surface each comprise: the eight planar restraining faces, the eight antivibration restraining faces, and the eight antirotation surfaces;

and the angle (α) is set to be 22.5 degrees.

(10) The double-sided circular cutting insert described in any one of the above (1) to (8), wherein

the upper side surface and the lower side surface each comprise: the six planar restraining faces, the six antivibration restraining faces, and the six antirotation surfaces; and the angle (α) is set to be 30 degrees.

(11) An indexable rotary cutting tool including: a tool main body which includes an insert mounting seat; and the double-sided circular cutting insert according to any one of claims1to10which is detachably attached to a seating surface provided on the insert mounting seat by tightening a clamp screw,

wherein the insert mounting seat includes a restraining wall surface for restraining the side surface of the circular cutting insert, the restraining wall surface erecting on the seating surface, and

wherein the restraining wall surface includes:a first restraining wall provided with an antirotation wall surface configured to restrain one of the antirotation surfaces formed on the upper side surface of the circular cutting insert, and a planar restraining wall surface configured to restrain one of the planar restraining faces disposed on the lower side surface at a position corresponding to the restrained antirotation surface, anda second restraining wall provided with a planar restraining wall surface configured to restrain one of the planar restraining faces formed on the upper side surface of the circular cutting insert, and an antivibration wall surface configured to restrain one of the antivibration restraining faces disposed on the lower side surface at a position corresponding to the restrained planar restraining face.

(12) The indexable rotary cutting tool described in the above (11), wherein

the antirotation wall surface and the planar restraining wall surface of the first restraining wall are formed such that the antirotation wall surface is disposed at a more distant position from the seating surface than the planar restraining wall surface.

(13) The indexable rotary cutting tool described in the above (11) or (12), wherein

the planar restraining wall surface and the antivibration wall surface of the second restraining wall are formed such that the antivibration wall surface is disposed at a closer position from the seating surface than the planar restraining wall surface.

(14) The indexable rotary cutting tool described in any one of the above (11) to (13), wherein

the antirotation wall surface includes a wall surface formed into a concave shape and configured to engage with the antirotation surface of the circular cutting insert.

(15) The indexable rotary cutting tool described in any one of the above (11) to (14), wherein

the antivibration wall surface includes a wall surface formed into a shape corresponding to the antivibration restraining face of the circular cutting insert and configured to contact with the antivibration restraining face.

(16) The indexable rotary cutting tool described in any one of the above (11) to (15), wherein

the double-sided circular cutting insert of which the upper side surface and the lower side surface each include the eight planar restraining faces, the eight antivibration restraining faces, and the eight antirotation surfaces is attached to the insert mounting seat, and

the first restraining wall and the second restraining wall are formed so as to intersect with each other at an intersecting angle of 67.5 degrees.

(17) The indexable rotary cutting tool described in any one of the above (11) to (15), wherein

the double-sided circular cutting insert of which the upper side surface and the lower side surface each include the six planar restraining faces, the six antivibration restraining faces, and the six antirotation surfaces is attached to the insert mounting seat, and

the first restraining wall and the second restraining wall are formed so as to intersect with each other at an intersecting angle of 60 degrees.

(18) A double-sided circular cutting insert including: a top surface and a bottom surface configured to be detachably attached to an insert mounting seat and formed into a circular shape in a planar view of the circular cutting insert; a side surface connecting the top surface and the bottom surface; a screw insertion hole penetrating from the top surface to the bottom surface; and cutting edges formed on intersecting ridgelines at which the top surface and the bottom surface intersect with the side surface, in which

when a plane bisecting the circular cutting insert in a thickness direction is referred to as an intermediate plane (M) of the circular cutting insert, an imaginary ridgeline at which the intermediate plane (M) intersects with the side surface is referred to as a side surface-intermediate line (N), the side surface between the side surface-intermediate line (N) and the top surface is referred to as an upper side surface, and the side surface between the side surface-intermediate line (N) and the bottom surface is referred to as a lower side surface,

the upper side surface and the lower side surface each include:a plurality of planar restraining faces disposed sequentially in a circumferential direction of the upper side surface and the lower side surface so as to interpose a joint portion between each of the planar restraining faces, each planar restraining face having a side disposed on the side surface-intermediate line (N), anda plurality of antivibration restraining faces, each antivibration restraining face being disposed between two planar restraining faces adjacent through the joint portion, and comprising an inclined face which has an apex portion at an end portion of each of the joint portions closer to the side surface-intermediate line (N) and a side disposed on the side surface-intermediate line (N) and tilts from the apex portion to the side so as to have a length in the circumferential direction of the side surface gradually increasing from the apex portion to the side surface-intermediate line (N), and

the planar restraining faces and the antivibration restraining faces of the lower side surface are disposed so as to be shifted with respect to the planar restraining faces and the antivibration restraining faces of the upper side surface by a predetermined angle (α) around a central axis of the screw insertion hole.

In addition, the circular cutting insert described in (18) may include additional aspects described in any one of the above (2) to (10).

Advantageous Effects of Invention

In the present invention, the first restraining wall and the second restraining wall are provided on the insert mounting seat of the tool main body of the indexable rotary cutting tool, a stage is provided at a position of the first restraining wall separated from the seating surface in a direction perpendicular to the seating surface, and the planar restraining wall surface and the antirotation wall surface are provided at the position at which the stage is provided. Similarly, the stage is provided at a position of the second restraining wall separated from the seating surface in the direction perpendicular to the seating surface, and the antivibration wall surface and the planar restraining wall surface are provided at the position at which the stage is provided. Meanwhile, in the circular cutting insert, the plurality of antivibration restraining faces, planar restraining faces, and antirotation surfaces (corners) are provided in each of the upper side surface and the lower side surface of the side surface. In addition, when the circular cutting insert is attached to the insert mounting seat, one of the antivibration restraining faces of the circular cutting insert comes into surface contact with and engages with the antivibration wall surface of the second restraining wall. Accordingly, the present invention can have the following effects.

(1) When a cutting operation of a workpiece is performed using the indexable rotary cutting tool, in cutting forces applied to the cutting edge of the circular cutting insert, a component force in a circumferential tangential direction of a rotation trajectory of the cutting edge of the cutting tool is transmitted to the antivibration restraining faces of the circular cutting insert and strongly presses the antivibration restraining faces to the antivibration wall surface of the insert mounting seat. According to this pressing action, the antivibration wall surface of the tool main body receives the component force of the cutting forces, and thus, occurrence of vibrations is prevented or suppressed while a restraining force generated by the surface-contact and engagement between the antivibration wall surface and one of the antivibration restraining faces of the circular cutting insert is maintained. Therefore, it is possible to provide the circular cutting insert capable of preventing or suppressing occurrence of vibrations and the indexable rotary cutting tool to which the cutting insert is attached.

(2) When an indexing operation of attaching the circular cutting insert to the insert mounting seat is performed, the planar restraining wall surface of the first restraining wall engages with the planar restraining face formed on the lower side surface of the side surface of the circular cutting insert, and the planar restraining wall surface of the second restraining wall engages with the planar restraining face formed on the upper side surface of the side surface of the circular cutting insert. Accordingly, it is possible to attach the circular cutting insert to the insert mounting seat without erroneous operations.

Moreover, the recessed portion of the antirotation wall surface provided on the first restraining wall engages with the corner of the side surface of the circular cutting insert, and thus, it is possible to prevent the circular cutting insert from rotating during the cutting operation.

(3) According to the above (1) and (2), in the present invention, in the cutting operation using the indexable rotary cutting tool to which the double-sided circular cutting insert is attached, it is possible to improve surface accuracy of a machined surface of a workpiece and it is possible to remarkably improve a tool life.

DESCRIPTION OF EMBODIMENTS

(First Embodiment of Circular Cutting Insert)

An embodiment of a double-sided circular cutting insert of the present invention will be described with reference to the drawings.FIG. 1is a perspective view showing a first embodiment of the circular cutting insert of the present invention andFIG. 2is a side view of the circular cutting insert1shown inFIG. 1.

As shown inFIGS. 1 and 2, a basic configuration of the circular cutting insert1of the present embodiment includes: a top surface2formed into a circular shape in a planar view; a bottom surface3disposed at a position opposite to the top surface2and formed into a circular shape in a planar view; a side surface4connecting the top surface2and the bottom surface3to each other; a screw insertion hole5penetrating from the top surface2to the bottom surface3; and cutting edges6aand6bformed along circular intersecting ridgelines at which the top surface2and the bottom surface3intersect with the side surface4and formed into circular shapes. In this way, the circular cutting insert1is a double-sided circular cutting insert which can use the cutting edge6aand the cutting edge6bprovided on the top surface2and the bottom surface3. A reference numeral P shown inFIG. 1is a central axis of the screw insertion hole5. The top surface2and the bottom surface3are formed into a circle centered on the central axis P of the screw insertion hole5in a planar view. In the descriptions below, the double-sided circular cutting insert1of the present embodiment may be simply referred to as a “cutting insert1”.

The top surface2includes: a rake face7awhich is an inclined face inclined downwardly (inclined in a direction approaching the bottom surface3) toward the screw insertion hole5from the cutting edge6aformed into a circular shape; and a top surface flat portion8aformed from the rake face7ato an opening of the screw insertion hole5. Each of the rake face7aand the top surface flat portion8ais an annular surface centered on the central axis P of the screw insertion hole5. The cutting insert1is a double-sided cutting insert, and thus, the shape and the configuration of the bottom surface3are the same as those of the top surface2. That is, the bottom surface3includes: a rake face7bwhich is an inclined face inclined downwardly (inclined in a direction approaching the top surface2) toward the screw insertion hole5from the cutting edge6b; and a bottom surface flat portion8bwhich is formed from the rake face7bto the opening of the screw insertion hole5(refer toFIG. 7). The top surface flat portion8aand the bottom surface flat portion8bare formed to be parallel to each other and are planes which are orthogonal to the central axis P of the screw insertion hole5.

Here, as shown inFIG. 2, a plane bisecting the double-sided circular cutting insert1in a thickness direction thereof is defined as an “intermediate plane (M)” of the cutting insert. The thickness direction of the cutting insert1indicates a direction in which the central axis P of the screw insertion hole5extends, and the intermediate plane (M) is a plane which is orthogonal to the central axis P. In the thickness direction, a direction from the top surface2or the bottom surface3toward the intermediate plane (M) is referred to as the inside in the thickness direction, and a direction from the intermediate plane (M) toward the top surface2or the bottom surface3is referred to as the outside in the thickness direction. In addition, a direction around the central axis P is referred to as a circumferential direction, and a direction orthogonal to the central axis P is referred to as a radial direction. In the radial direction, a direction approaching the central axis P is referred to as the inside in the radial direction, and a direction separated from the central axis P is referred to as the outside in the radial direction.

FIG. 3shows the shape of the cross-section of the cutting insert1taken along the intermediate plane (M) in the side view of the cutting insert1shown inFIG. 2. As shown inFIG. 3, the outline showing the shape of the cross-section of the cutting insert1is formed into a regular polygon or an approximately regular polygon formed by alternately and sequentially connecting sides c and sides g (refer toFIG. 4) described later. The shape of the cross-section (FIG. 3) of the cutting insert1shown inFIG. 1(FIG. 2) taken along the intermediate plane (M) is a regular hexadecagon in which each of the lengths of the sides c and the sides g is m. Hereinafter, the configuration of the side surface4will be described with reference toFIG. 4.

FIG. 4is an enlarged view of the side view of the circular cutting insert1of the present embodiment shown inFIG. 2. The side surface4of the cutting insert1has characteristic configurations in the cutting insert of the present embodiment, and thus, hereinafter, the configuration of the side surface4will be described in detail.

Here, an imaginary ridgeline at which the intermediate plane M of the cutting insert1intersects with the side surface4is defined as a “side surface-intermediate line (N)” of the double-sided cutting insert. As described above, the intermediate plane (M) is the plane orthogonal to the central axis P and bisecting the double-sided circular cutting insert1in the thickness direction. Accordingly, in the descriptions below, the side surface4between the side surface-intermediate line (N) and the top surface2is referred to as an “upper side surface4a”, and the side surface4between the side surface-intermediate line (N) and the bottom surface3is referred to as a “lower side surface4b”. In the present embodiment, the upper side surface4aand the lower side surface4bhave the same shape as each other. More specifically, the lower side surface4bhas a shape obtained by inverting the upper side surface4awith respect to the intermediate plane (M) and rotating (shifting) the inverted upper side surface4aabout the central axis P by a predetermined angle α.

As shown inFIG. 4, the side surface4is formed so as to be slightly retracted with respect to end portions (peripheral edge portions) of the top surface2and the bottom surface3in the direction of the central axis P of the screw insertion hole5, and thus, the cutting insert1is formed into a hourglass shape when viewed from the side surface. In other words, the side surface4has a shape which is recessed toward the inside in the radial direction with respect to a cylindrical surface obtained by connecting the cutting edge6aof the top surface2and the cutting edge6bof the bottom surface3.

The upper side surface4aconfiguring the side surface4includes: a flank face9aof the cutting edge6awhich is formed along the peripheral edge portion of the top surface2; and a plurality of planar restraining faces10a,10b, . . . , between the flank face9aand the side surface-intermediate line (N). The planar restraining faces10a,10b, . . . , have the same shape as each other, each have a side c which is disposed on and along the side surface-intermediate line (N), and are sequentially disposed in one row in the circumferential direction of the upper side surface4aso as to interpose a joint portion12abetween each of the planar restraining faces. In the circular cutting insert1shown inFIG. 1(FIG. 4), an example in which eight planar restraining faces10a,10b, . . . , and10hare formed on the upper side surface4a, is shown. However, in the circular cutting insert of the present invention, the number of the planar restraining faces10a,10b, . . . is not limited to eight.

The flank face9ais a conical face which extends so as to be inclined toward the inside in the radial direction from the cutting edge6atoward the intermediate plane (M).

Each of the eight planar restraining faces10a,10b, . . . , and10his formed so as to be a plane perpendicular to or approximately perpendicular to the top surface flat portion8aof the top surface2. The planar restraining faces10a,10b, . . . , and10hare disposed at equal intervals in the circumferential direction such that a circle centered on the central axis P is inscribed on the planar restraining faces10a,10b, . . . , and10hand the planar restraining faces10a,10b, . . . , and10hare rotationally symmetrical with respect to the central axis P.

In addition, the upper side surface4aincludes: a plurality of joint portions12awhich each connect two planar restraining faces10aand10b,10band10c, . . . , and10hand10awhich are each adjacent to each other in the direction along the side surface-intermediate line (N) (the circumferential direction of the upper side surface4a); and a plurality of antivibration restraining faces11a,11b, . . . , which are each formed from a lower end portion (apex portion (t1) shown inFIG. 4) of each of the joint portions12acloser to the side surface-intermediate line (N) to the side surface-intermediate line (N) and are each formed into a trapezoidal shape when viewed from the side surface of the cutting insert1. In the circular cutting insert1shown inFIG. 1(FIG. 4), an example in which eight antivibration restraining faces11a,11b, . . . , and11hformed into the same shape are provided, is shown. The number of the antivibration restraining faces11a11b, . . . , provided on the upper side surface4ais the same as the number of the planar restraining faces10a,10b, . . . . In this way, the antivibration restraining faces11a,11b, . . . are each formed between the planar restraining faces10aand10b,10band10c, . . . , which are each adjacent to each other. The antivibration restraining faces11a,11b, . . . are disposed at equal intervals in the circumferential direction such that the circle centered on the central axis P is inscribed on the antivibration restraining faces11a,11b, . . . and the antivibration restraining faces11a,11b, . . . are rotationally symmetrical with respect to the central axis P.

Moreover, in the circular cutting insert1of the present embodiment, the shape of each of the antivibration restraining faces11a,11b, . . . , and11hof the cutting insert1is a trapezoidal shape when viewed from the side surface. However, like a second embodiment described later, the shape when viewed from the side surface may be a triangular shape (refer toFIGS. 8 to 10).

Each of the planar restraining faces10a,10b, . . . , and10hshown inFIG. 4is formed in a hexagonal plane having a side a, a side b, the side c, a side d, a side e, and a side f, and among the sides, the side c is formed on and along the side surface-intermediate line (N). Each of the planar restraining faces10a,10b, . . . , and10his formed into a hexagonal shape which is linearly symmetric with respect to a perpendicular bisector of the side c. In addition, inFIG. 4, a length of the side f which faces the side c and is parallel to the side c is indicated by1, and a length of the side c is indicated by m. InFIG. 3showing the above-described shape of the cross-section of the cutting insert1taken along the intermediate plane (M), the shape of the outline thereof is shown so as to be a regular hexadecagon in which the length of one side is indicated by the above “m”.

The disposition positions of the side a to the side f of each of the planar restraining faces10a,10b, . . . , and10hformed into a plane and characteristics such as the connections thereof will be described as follow using the planar restraining face10ashown inFIG. 4as an example. The disposition positions of the side a to the side f of each of other planar restraining faces10b, . . . , and10hand characteristics such as the connections thereof are the same as those of the planar restraining face10a.

The side a is a ridgeline (boundary line) between the joint portion12ainterposed between the planar restraining face10ashown inFIG. 4and the planar restraining face10badjacent to the planar restraining face10aon the right side of the paper surface in the circumferential direction of the upper side surface4a, and the planar restraining face10a. In addition, the side a is formed to the lower end portion (the apex portion (t1) or the vicinity of the apex portion (t1)) of the joint portion12acloser to the side surface-intermediate line (N) in the direction orthogonal to the intermediate plane (M). In other words, the side a is a straight line which extends from the apex portion (t1) or the vicinity thereof toward the top surface2in the thickness direction. Moreover, as shown inFIG. 4, the apex portion (t1) is positioned on the top surface2side (the outside in the thickness direction) from the intermediate plane (M).

The side b is a ridgeline which is inclined so as to form an obtuse angle with respect to the side a from the lower end portion of the side a closer to the side surface-intermediate line (N) and is formed to a point n1on the side surface-intermediate line (N). In other words, the side b is a straight line which extends from the apex portion (t1) or the vicinity thereof to the point n1in a direction separated from the planar restraining face10b. In addition, the side b is formed as a ridgeline which is also one side of the antivibration restraining face11adescribed later and is positioned between the planar restraining face10aand the antivibration restraining face11a.

The side c has the length m from the point n1of the side b on the side surface-intermediate line (N) and is formed to a point n2on the side surface-intermediate line (N) along the side surface-intermediate line (N). The side c is a straight line which forms an obtuse angle with respect to the side b and extends in a direction perpendicular to the side a.

The side d is formed as a ridgeline which is inclined so as to form an obtuse angle with respect to the side c from the point n2of the side c on the side surface-intermediate line (N) to the lower end portion (the apex portion (t1) or the vicinity of the apex portion (t1)) of the joint portion12ainterposed between the planar restraining face10aand another planar restraining face10hadjacent to the left side on the paper surface of the planar restraining face10a. In other words, the side d is a straight line which extends from the point n2to the apex portion (t1) or the vicinity thereof in the direction approaching the top surface2. In addition, the side d is formed as a ridgeline which is also one side of another antivibration restraining face11hdescribed later and is positioned between the planar restraining face10aand the antivibration restraining face11h. Moreover, the side d is connected to the lower end portion of the side e described later closer to the side surface-intermediate line (N) so as to form an obtuse angle with respect to the side e. In addition, the angle between the side c and the side d is the same as the angle between the side c and the side b, and the angle between the side d and the side e is the same as the angle between the side b and the side a. Moreover, the length of the side d is the same as the length of the side b.

The side e is a ridgeline between the joint portion12ainterposed between the planar restraining face10aand another planar restraining face10hadjacent to the left side on the paper surface of the planar restraining face10a, and the planar restraining face10a, and the side e is formed in a direction orthogonal to the intermediate plane (M). In other words, the side e is a straight line which extends from the lower end portion (the apex portion (t1) or the vicinity of the apex portion (t1)) of the joint portion12atoward the top surface2in the thickness direction. The length of the side e is the same as the length of the side a.

The side f is a straight line which connects the upper end portion (the end portion closer to the top surface2) of the side e and the upper end portion (the end portion closer to the top surface2side) of the side a and is parallel to the side c, and has the length l in the circumferential direction (more accurately, in a direction parallel to the side c) of the side surface4. The side f is orthogonal to the side a and the side e.

For example, each joint portion12afor connecting the adjacent two planar restraining faces in the circumferential direction of the upper side surface4ato each other may be integrally molded during powder molding of the circular cutting insert1such that the side a and the side e facing each other of the planar restraining face10aand the planar restraining face10badjacent to each other in the circumferential direction are integrated so as to be one straight-line ridgeline (refer to the second embodiment described later). Meanwhile, unlike the above-described case, as shown inFIG. 4, in the case of providing the joint portion12ahaving a predetermined width w in the circumferential direction of the side surface4and connecting the planar restraining faces adjacent to each other through the joint portion12ato each other, strength of the joint portion is effectively and maintained, which is preferable. InFIG. 4, in order to clarify differences between the first embodiment and the second embodiment described later, the width w of the joint portion12ais drawn larger than an actual width.

The value of the width w (an interval between the side a and the side e) of the joint portion12ain the circumferential direction of the side surface4(upper side surface4a) may be appropriately set according to a diameter of the top surface2(bottom surface3) of the circular cutting insert1. However, it is desirable that the width w is set to be at least approximately 0.5 mm to 1 mm, and that the shape of the surface of the joint portion12ain the cross-section thereof is a gentle arc shape (R shape). That is, it is desirable that each joint portion12ais a surface formed into an arc shape protruding toward the outside in the radial direction in the cross-section of the joint portion12aorthogonal to the central axis P.

In addition, in each joint portion12a, a portion positioned to be separated from the intermediate plane (M) toward the top surface2is served as an end portion (a lower end portion) closer to the side surface-intermediate line (N), and the joint portion12aextends from the end portion toward the top surface2in the thickness direction.

In the cutting insert1of the first embodiment, similarly to the upper side surface4a, the lower side surface4bincludes eight planar restraining faces13a,13b, . . . , and13hand eight antivibration restraining faces14a,14b, . . . , and14heach formed into a trapezoidal shape in a planar view.

Next, characteristics of the antivibration restraining faces11a,11b, . . . , and11hwhich are provided on the upper side surface4aand are each formed into a trapezoidal shape when the cutting insert1is viewed from the side surface and the disposition positions thereof will be described using the antivibration restraining face11ashown inFIG. 4as an example.

The antivibration restraining face11a, which is formed into a trapezoidal shape when the cutting insert1is viewed from the side surface, is an isosceles trapezoidal (or an approximately isosceles trapezoidal) face having the apex portion (t1) formed on the lower end portion of the joint portion12acloser to the side surface-intermediate line (N) as an upper base (t1) of the trapezoid and a line segment obtained by connecting the two points (points n1and n2) on the side surface-intermediate line (N) to each other as a lower base. The upper base (t1) is a ridgeline having the minute width w of the joint portion12aprovided between the planar restraining face10aand the adjacent planar restraining face10b, and the upper base (t1) is formed to be parallel to or approximately parallel to the side surface-intermediate line (N).

Meanwhile, in the lower base having an isosceles trapezoid, one side on the side surface-intermediate line (N) is the lower base g of the antivibration restraining face11a, and the one side is obtained by connecting the point (n1) at which the side b and the side c of the planar restraining face10aintersect with each other and the point (n2) at which the side c and the side d of the planar restraining face10badjacent to the planar restraining face10aintersect with each other. In addition, as shown inFIG. 4, two sides becoming legs of the isosceles trapezoid are the side b of the planar restraining face10aand the side d of the planar restraining face10badjacent to the planar restraining face10a. In this way, in the two sides b and d becoming the legs of the trapezoid of the antivibration restraining face11aconfiguring the isosceles trapezoid, the leg b of the trapezoid is configured so as to be the ridgeline which is also the side b of the planar restraining face10a. In addition, another leg d of the trapezoid is configured so as to be the ridgeline which is also the side d of the planar restraining face10b.

Moreover, as shown inFIG. 4, the lower base g has the same length m as the length m of the one side c of the planar restraining face10aformed on the side surface-intermediate line (N).

As described above, the antivibration restraining face11aformed into an isosceles trapezoidal shape when the cutting insert1is viewed from the side surface is formed (disposed) between the planar restraining face10aand the planar restraining face10badjacent to each other, in which the ridgeline having the width w on the apex portion of the joint portion12ais the upper base (t1), and the side having the length m on the side surface-intermediate line (N) obtained by connecting the point (n1) at which the side b and the side c of the planar restraining face10aintersect with each other and the point (n2) at which the side c and the side d of the planar restraining face10badjacent to the planar restraining face10aintersect with each other is the lower base g. Accordingly, in the antivibration restraining face11aformed into an isosceles trapezoidal shape when the cutting insert1is viewed from the side surface, the length of the antivibration restraining face11ain the circumferential direction gradually increases from the upper base (t1) toward the lower base g. In addition, the antivibration restraining face extends to be inclined to the inside in the radial direction from the upper base (t1) to the lower base g.

Similarly, the antivibration restraining face11bis disposed between the planar restraining face10band the planar restraining face10c(not shown inFIG. 4) adjacent to the planar restraining face10bthrough the joint portion12a, in which the line segment having the width w on the apex portion of the joint portion12ais the upper base (t1) and the side having the length m on the side surface-intermediate line (N) obtained by connecting the point (n1) at which the side b and the side c of the planar restraining face10bintersect with each other and the point (n2) at which the side c and the side d of the planar restraining face10cadjacent to the planar restraining face10bintersect with each other is the lower base g. In this way, other antivibration restraining faces11c,11d, . . . , and11hare also formed between the adjacent planar restraining faces so as to have specifications such as the shapes, the dimensions, or dispositions similar to those of the antivibration restraining faces11aand11b.

Similarly to the upper side surface4a, the lower side surface4bconfiguring the side surface4includes: a flank face9bof the cutting edge6bformed along the peripheral edge of the bottom surface3; eight planar restraining faces13a,13b, . . . , and13hwhich are each formed into the same shape between the flank face9band the side surface-intermediate line (N) and each have one side disposed on and along the side surface-intermediate line (N); and eight antivibration restraining faces14a,14b, . . . , and14hwhich are each formed into an isosceles trapezoid formed to the side surface-intermediate line (N) from an apex portion (t2), which is closer to the side surface-intermediate line (N), of each of the joint portions12bbetween the planar restraining faces13aand13b,13band13c, . . . , and13hand13aadjacent to each other in the circumferential direction of the lower side surface4b. Each of the planar restraining faces13a,13b, . . . , and13his formed so as to be a plane which is perpendicular to or approximately perpendicular to the bottom surface flat portion8b(top surface flat portion8a).

Similarly to the apex portion (t1) of the upper side surface4a, the apex portion (t2) shown inFIG. 4has the width w in the circumferential direction of the upper side surface4aand is the upper base of each of the antivibration restraining faces14a,14b, and14hformed in an isosceles trapezoid when the cutting insert1is viewed from the side surface.

The planar restraining faces13a,13b, . . . , and13hprovided on the lower side surface4band the planar restraining faces10a,10b, . . . , and10hprovided on the upper side surface4ahave the same shape as each other, the directions of the dispositions thereof are inverted with respect to the side surface-intermediate line (N), and the planar restraining faces13a,13b, . . . , and13hand the planar restraining faces10a,10b, . . . , and10hare disposed so as to be shifted from each other in the upper side surface4aand the lower side surface4b.

Similarly, the antivibration restraining faces14a,14b, . . . , and14hprovided on the lower side surface4band the antivibration restraining faces11a,11b, . . . , and11hprovided on the upper side surface4ahave the same shape as each other, the directions and the dispositions thereof are inverted with respect to the side surface-intermediate line (N), and the antivibration restraining faces14a,14b, . . . , and14hand the antivibration restraining faces11a,11b, . . . , and11hare disposed so as to be shifted from each other in the upper side surface4aand the lower side surface4b. Here, the “shifting” means rotating the lower side surface4bwith respect to the upper side surface4aabout the central axis P of the screw insertion hole5from a state where the upper side surface4aand the lower side surface4bhaving the same shape as each other are disposed so as to be mirror-symmetrical with respect to the side surface-intermediate line (N).

In this way, inFIG. 4, the planar restraining faces and the antivibration restraining faces of each of the upper side surface4aand the lower side surface4beach have the same shape as each other, and thus, the corresponding reference numerals of the sides configuring each of the restraining faces of the upper side surface4aare assigned to the sides configuring each of the restraining faces of the lower side surface4b. Shift specifications at the positions where the restraining faces of the upper side surface4aand the restraining faces of the lower side surface4bare disposed will be described later, and the restraining faces of the upper side surface4aand the restraining faces of the lower side surface4bare shifted from each other by a predetermined angle (α) with respect to the central axis P of the screw insertion hole5. In other words, the restraining faces of the upper side surface4aand the restraining faces of the lower side surface4bare disposed at positions at which the restraining faces of the lower side surface4brotates by the predetermined angle (α) with respect to the restraining faces of the upper side surface4aabout the central axis P from a state where the restraining faces of the upper side surface4aand the restraining faces of the lower side surface4bare disposed so as to be mirror-symmetrical with respect to the side surface-intermediate line (N).

Accordingly, when the plurality of regions of the cutting edges9aand9bare selectively used by rotating the circular cutting insert1, an accurate indexing function can be exerted.

As shown inFIG. 4, the side c of each of the planar restraining faces10a,10b, . . . , and10hof the upper side surface4ais also the lower base of each of the antivibration restraining faces14a,14b, . . . , and14hof the lower side surface4bwhich are each formed into an isosceles trapezoid when the cutting insert1is viewed from the side surface. In addition, in each of the planar restraining faces13a,13b, . . . , and13hof the lower side surface4b, one side formed along the side surface-intermediate line (N) is also the lower base g of each of the antivibration restraining faces11a,11b, . . . , and11hof the upper side surface4a. Accordingly, even when the top and bottom sides of the cutting insert1are reversed, the shapes of the cutting insert1are the same as each other, and thus, it is not necessary to change the shape of an insert mounting seat32formed on a tool main body31depending on whether the cutting edge to be used for the cutting operation is the cutting edge6aof the top surface2or the cutting edge6bof the bottom surface3. That is, even when the cutting edge6aof the top surface2is used or the cutting edge6bof the bottom surface3is used, the cutting insert1can be attached to the same insert mounting seat32.

When the cutting insert1is viewed from the side surface, the antivibration restraining faces11a,11b, . . . , and11hwhich are each formed into an isosceles trapezoid on the upper side surface4aand the antivibration restraining faces14a,14b, . . . , and14hwhich are each formed into an isosceles trapezoid on the lower side surface4bare disposed as described above. Accordingly, the lower bases g each having the length m on the antivibration restraining faces of the upper side surface4aand the lower bases c each having the length m on the antivibration restraining faces of the lower side surface4bare alternately disposed along the side surface-intermediate line (N) (FIG. 3). Accordingly, effects described later can be obtained.

In the length of each of the joint portions12aand12bof the upper side surface4aand the lower side surface4b, that is, the length of each of the side a and the side e, it is preferable that the length of each of the joint portions12aand12bin the direction of the central axis P of the screw insertion hole5is set to approximately 0.1 to 0.15 times the thickness (the distance between the cutting edge6aand the cutting edge6bin the thickness direction) of the circular cutting insert1.

Reference numerals21aand21bshown inFIG. 4indicate inclined faces provided so as to form the above-described planar restraining faces10a,10b, . . . , and10hand planar restraining faces13a,13b, . . . , and13hon the upper side surface4aand the lower side surface4bof the side surface4. Each of the inclined faces21aand21bis formed so as to be inclined by a predetermined angle (δ) in the direction of the central axis P of the screw insertion hole5(FIG. 7). More specifically, the inclined face21ais a surface which extends so as to be inclined to the outside in the radial direction from the side f of each of the planar restraining faces10a, . . . , and10htoward the flank face9a, and the inclined face21bis a surface which extends to the outside in the radial direction from the side f of each of the planar restraining faces13a, . . . , and13htoward the flank face9b. As shown inFIG. 4, for example, each of the upper end portions of the joint portions12aand12b(end portions of the joint portions12aand12bon the outside in the thickness direction) is connected to the side surface4abetween the adjacent inclined faces21aor between the adjacent inclined faces21b. In other words, in the example ofFIG. 4, the upper end portion of the joint portion12ais smoothly continued to a region between the adjacent inclined faces21ain the circumferential direction, and the upper end portion of the joint portion12bis smoothly continued to a region between the adjacent inclined faces21bin the circumferential direction.

Next, in the upper side surface4aand the lower side surface4b, the shifting of the positions of the planar restraining faces and the antivibration restraining faces disposed on the upper side surface4aand the lower side surface4bwill be described with reference toFIG. 5.

FIG. 5is a sectional view of the circular cutting insert1shown inFIG. 2taken along the intermediate plane (M),FIG. 5(a)is a sectional view when the circular cutting insert1is viewed toward the top surface2from the cross-section, andFIG. 5(b)is a sectional view when the circular cutting insert1is viewed toward the bottom surface3from the cross-section. Similarly toFIG. 3, inFIG. 5(a), the planar restraining faces10a, . . . , and10hand the antivibration restraining faces11a, . . . , and11hare alternately disposed to be formed into a regular hexadecagonal shape, and inFIG. 5(b), the planar restraining faces13a, . . . , and13hand the antivibration restraining faces14a, . . . , and14hare alternately disposed to be formed into a regular hexadecagonal shape.

In addition, inFIGS. 5(a) and 5(b), the central axes P of the screw insertion holes5shown inFIGS. 5(a) and 5(b)are connected to each other by a straight line (dashed line) C such that the disposed positions of the planar restraining faces and the antivibration restraining faces disposed on the upper side surface4aand the lower side surface4bcorrespond to each other, and the disposed positions of the planar restraining faces and the antivibration restraining faces disposed on the upper side surface4aand the lower side surface4bare shown to correspond to each other with respect to the central axis P. In other words, inFIGS. 5(a) and 5(b), ifFIG. 5(a)andFIG. 5(b)face each other such that the central axis P and the straight line C coincide with each other, the restraining faces of the upper side surface4aand the restraining faces of the lower side surface4bare shown by a sectional view to obtain the dispositions shown inFIGS. 1, 2, and4. InFIG. 5, for simplification of explanation, the joint portions12aand12bare not shown, and only reference numerals are assigned to the positions thereof.

For example,FIG. 5shows that, as shown inFIG. 5(b), the planar restraining face13ais disposed on the lower side surface4bcorresponding to the position at which the antivibration restraining faces11aof the upper side surface4ashown inFIG. 5(a)is disposed. In other words,FIGS. 5(a) and 5(b)show that the position at which the antivibration restraining faces11aof the upper side surface4ais disposed and the position at which the planar restraining face13ais disposed on the lower side surface4bcoincide with each other in the circumferential direction. In this way,FIGS. 5(a) and 5(b)show a correspondence between the positions (positions in the circumferential direction) at which the planar restraining faces and the antivibration restraining faces of the upper side surface4aand the lower side surface4bshown inFIG. 4are disposed.

In addition,FIG. 5shows that the dispositions of the planar restraining faces and the antivibration restraining faces of the upper side surface4aand the lower side surface4bare shifted by a predetermined angle (α) with respect to the central axis P of the screw insertion hole5. Specifically, the angle (α) is formed between the straight line C passing through the center of the antivibration restraining face11aof the upper side surface4a(the center of the apex portion (t1) in the circumferential direction) shown inFIG. 5(a)and the central axis P of the screw insertion hole5and a straight line D passing through the center of the antivibration restraining face14hof the lower side surface4b(the center of the apex portion (t2) in the circumferential direction) shown inFIG. 5(b)and the central axis P of the screw insertion hole5. This indicates the antivibration restraining faces11a, . . . , and11hdisposed on the upper side surface4aand the antivibration restraining faces14a, . . . , and14hdisposed on the lower side surface4bare formed such that the dispositions thereof (the positions in the circumferential direction) are shifted from each other by the angel (α) with respect to the central axis P of the screw insertion hole5. Similarly, the planar restraining faces10a, . . . , and10hdisposed on the upper side surface4aand the planar restraining faces13a, . . . , and13hdisposed on the lower side surface4bare formed such that the dispositions thereof are shifted from each other by the angel (α) with respect to the central axis P of the screw insertion hole5.

As described above, the circular cutting insert1shown inFIG. 1is an embodiment (eight-corner type cutting insert) in which the eight planar restraining faces and the eight antivibration restraining faces are disposed in each of the upper side surface4aand the lower side surface4b. Accordingly, a shifting angle (an angle indicating phase differences between the upper side surface4aand the lower side surface4b) (α) of the disposition is set to 22.5 degrees (360 degrees/(2×8)).

In the circular cutting insert1, in this way, the shifting angle (α) is set to 22.5 degrees, and thus, as shown inFIG. 4, the eight antivibration restraining faces11a,11b, . . . , and11hwhich are each formed into an isosceles trapezoid when the cutting insert1is viewed from the side surface can be formed and disposed, in which the isosceles trapezoid has the end portion (apex portion (t1)) of the joint portion12aof the upper side surface4aof the circular cutting insert1closer to the side surface-intermediate line (N) as the upper base and the side of each of the planar restraining faces13a,13b, . . . , and13hof the lower side surface4bon the side surface-intermediate line (N) as the lower base. Similarly, the eight antivibration restraining faces14a,14b, . . . , and14hwhich are each formed into an isosceles trapezoid when the cutting insert1is viewed from the side surface can be formed and disposed, in which the isosceles trapezoid has the end portion (apex portion (t2)) of the joint portion12bof the lower side surface4bcloser to the side surface-intermediate line (N) as the upper base and the side of each of the planar restraining faces10a,10b, . . . , and10hof the upper side surface4aon the side surface-intermediate line (N) as the lower base. In addition, on the side surface-intermediate line (N), the sides c of the planar restraining faces10b,10c, . . . , and10aof the upper side surface4awhich are also the lower bases of the antivibration restraining faces14a,14b, . . . , and14hof the lower side surface4band the sides g of the planar restraining faces13a,13b, . . . , and13hof the lower side surface4bwhich are also the lower bases of the antivibration restraining faces11a,11b, . . . , and11hof the upper side surface4aeach have the same length m and can be disposed so as to be alternately connected to each other.

Accordingly, in the cutting insert1which is the double-sided circular cutting insert, for example, in a case where an use region of the cutting edge6aof the top surface2is changed and the cutting insert1is reattached to the insert mounting seat so as to perform the cutting operation, even when the use region of the cutting edge6ais changed, the same performance of the cutting operation can be secured, that is, it is possible to prevent variations in the performance of the cutting operation. In addition, even in a case where the cutting operation is performed using the cutting edge6bof the bottom surface3, it is possible to secure the same performance of the cutting operation as that of the cutting edge6aof the top surface2.

In the double-sided circular cutting insert1of the present embodiment, the number (r) of each of the planar restraining faces and the antivibration restraining faces provided in each of the upper side surface4aand the lower side surface4balong the side surface-reference line (N) (side surface-intermediate line (N)), is eight. However, as the number (r) other than eight, it is desirable that the number is set to an even number such as six according to the diameter of the top surface2of the cutting insert1. The reason is because, generally, the diameter of the top surface2of the circular cutting insert1is approximately 10 mm to 20 mm, and thus, in a case where the number (r) is six or eight, a mold for press-molding a powder molded body of the circular cutting insert1can be easily manufactured. In addition, in the powder molded body of the circular cutting insert1, in order to manufacture a molded body which is uniformly filled with powder, it is desirable that the number (r) is set to eight or six. In addition, it is desirable that the number of the use regions of the cutting edges6aand6bincreases to lengthen the life of one cutting insert in the cutting operation. Here, it is desirable to increase the number of the use regions of the cutting edges6aand6b. However, in order to prevent the length of the cutting edge per one use region from being shortened due to the increase of the divided number of the cutting edges6aand6b, preferably, the number (r) of each of the planar restraining faces and the antivibration restraining faces is set to ten or less.

Preferably, the shifting angle (α) of the disposition is set to (360/2×r) degrees according to the number (r) of each of the planar restraining faces and the antivibration restraining faces (the number of corners) of each of the upper side surface4aand the lower side surface4b. More preferably, 18 degrees (r=10)≤α≤(360/2×r) degrees is satisfied.

FIG. 6is a sectional view taken along line A-A in the region of the upper side surface4aon the side surface4of the cutting insert1shown inFIG. 4. That is,FIG. 6shows a sectional view when the region each having the length1between the sides a and the sides e of the planar restraining faces10a,10b, . . . , and10hformed on the upper side surface4ais taken along line A-A orthogonal to the central axis P. InFIG. 6, for simplification of explanation, the joint portions12aare not shown, and only reference numerals are assigned to the positions thereof.

As shown inFIG. 6, at locations at which the planar restraining faces10aand10b,10band10c, . . . , and10hand10aadjacent in the circumferential direction of the upper side surface4aare connected to each other through the joint portions12a, regions S including a predetermined range of planar restraining faces from the sides a and the sides e of the adjacent two planar restraining faces form the corners (corner portions)15a,15b, . . . , and15hwhich have the joint portions12aas protruding apex portions. In addition, the corners15a, . . . , and15hhave shapes protruding to the outside of the cutting insert1from the planar restraining faces13a,13b, . . . , and13hwhich are disposed on the lower side surface4bto correspond the positions of the corners15a, . . . , and15h(face the corners in the thickness direction). In other words, the corners15a,15b, . . . , and15hare each disposed radially outside the planar restraining faces13a,13b, . . . , and13hpositioned at the same positions in the circumferential direction. In addition, the corners15a,15b, . . . , and15hare disposed radially inside the cutting edge6aof the upper side surface4a(FIG. 7).

The corners15a,15b, . . . , and15hformed by the adjacent two planar restraining faces10aand10b, . . . , and10hand10aare used as antirotation surfaces19a,19b, and19hprovided on the circular cutting insert1of the present embodiment, that is, a means of preventing the rotation of the circular cutting insert1when the circular cutting insert1is attached to the insert mounting seat32of the indexable rotary cutting tool30. Functions of the antirotation surfaces19a,19b, . . . , and19hfor preventing the rotation of the circular cutting insert1will be described later.

Similarly, in the sectional view taken along line B-B in the region of the lower side surface4bin the cutting insert1shown inFIG. 4, that is, in the sectional view when the region each having the length1between the sides a and the sides e of the planar restraining faces13a,13b, . . . , and13hformed on the lower side surface4bis taken along line B-B orthogonal to the central axis P, similarly toFIG. 6, at locations at which the planar restraining faces13aand13b,13b, . . . , and13hand13aadjacent in the circumferential direction of the upper side surface4aare connected to each other through the joint portions12b, the regions S including a predetermined range of planar restraining faces from the sides a and the sides e of the adjacent two planar restraining faces13aand13b,13b, . . . , and13hand13aare not shown, but the regions S form the corners (corner portions)16a,16b, . . . , and16hwhich have the joint portions12bas protruding apex portions. Similarly to the corners (corner portions)15a,15b, . . . , and15hof the upper side surface4a, the corners (corner portions)16a,16b, . . . , and16halso configure the antirotation surfaces20a,20b, . . . , and20h(not shown) in the circular cutting insert1of the present embodiment.

As described above, in the upper side surface4a, the regions S including the joint portions12aconnecting the adjacent planar restraining faces10aand10b, . . . , and10aand10hin the circumferential direction of the side surface4to each other and the planar restraining faces10a,10b, . . . , and10haround the joint portions12aform the corners (corner portion)15a,15b, . . . , and15h. The corners15a,15b, . . . , and15hprotrude to the outside of the cutting insert1from the planar restraining faces13a,13b, . . . , and13hpositioned in the region of the lower side surface4b. Accordingly, each of the antivibration restraining faces11a,11b, . . . , and11hwhich are each formed into a trapezoidal shape when the cutting insert1is viewed from the side surface is formed as an inclined face which is inclined downwardly from the apex portion (t1) which is the upper base, that is, the end portion of the joint portion12acloser to the side surface-intermediate line (N) toward the side surface-intermediate line (N) which is the lower base g (which is inclined radially inward with respect to the thickness direction), and the length of each of the antivibration restraining faces11a,11b, . . . , and11hin the circumferential direction of the side surface4gradually increases from the apex portion (upper base) (t1) toward the side surface-intermediate line (N).

Similarly to the upper side surface4a, in the lower side surface4b, each of the antivibration restraining faces14a,14b, . . . , and14hwhich are each formed into a trapezoidal shape when the cutting insert1is viewed from the side surface is formed as an inclined face which is inclined upwardly from the apex portion (t2) which is the upper base, that is, the end portion of the joint portion12bcloser to the side surface-intermediate line (N) toward the lower base c on the side surface-intermediate line (N) (which is inclined radially inward with respect to the thickness direction), and the length of each of the antivibration restraining faces14a,14b, . . . , and14hin the circumferential direction of the side surface4gradually increases from the apex portion (upper base) (t2) toward the side surface-intermediate line (N).

In this way, the antivibration restraining faces provided in each of the upper side surface4aand the lower side surface4bare formed such that the length of each of the antivibration restraining faces in the circumferential direction of the side surface4gradually increases toward the side surface-intermediate line (N), surface areas of the antivibration restraining faces are made as large as possible, and thus, an improved antivibration function is exerted. The antivibration functions of the antivibration restraining faces will be described in detail later.

The antivibration restraining faces11a,11b, . . . , and11hof the upper side surface4aand the antivibration restraining faces14a,14b, . . . , and14hof the lower side surface4bare formed as the inclined faces which are inclined upwardly or downwardly (inclined faces which are inclined radially inward with respect to the thickness direction) from the apex portions (t1) and the apex portions (t2) toward the side surface-intermediate line (N), and inFIGS. 5(a) and 5(b), the inclined faces of the antivibration restraining faces are shown as the inclined faces17a,17b, . . . , and17hand the inclined faces18a,18b, . . . , and18h. In addition, inFIG. 6, the corners (corner portions)15a,15b, . . . , and15hprovided on the upper side surface4aare shown.

Preferably, an angle at which each of the antivibration restraining faces11a,11b, . . . , and11hof the upper side surface4aand each of the antivibration restraining faces14a,14b, . . . , and14hof the lower side surface4bare inclined downwardly or inclined upwardly, that is, an angle at which each antivibration restraining face intersects with the intermediate plane (M) is set to a range from 40 degrees to 60 degrees. The reason is because if the angle is less than 40 degrees, the area of each antivibration restraining face decreases, and as described later, a contact area between the antivibration restraining faces and the antivibration wall surface42of the insert mounting seat32decreases, and thus, sufficient antivibration effects cannot be obtained. Meanwhile, in a case where the angle exceeds 60 degrees, a component force of a cutting force acts on the antivibration restraining faces, a component in the thickness direction of the cutting insert1of a force by which the antivibration wall surface42is pressed by the antivibration restraining faces decreases, and thus, antivibration effects decrease. More preferably, the intersecting angle is 45 degrees to 55 degrees.

FIG. 7shows a view showing a longitudinal section of the circular cutting insert1which passes through the central axis P of the screw insertion hole5and intersects with the antivibration restraining faces14dand14h(a view showing a cross-section taken along the straight line D shown inFIG. 5(b)). In dotted circles shown inFIG. 7, as examples of lines showing the cross-sectional shapes of the surfaces of the antivibration restraining faces14a,14b, . . . , and14hprovided on the lower side surface4b, the cross-sections of the antivibration restraining faces14dand14hare shown. Each of the cross-sections of the antivibration restraining faces14dand14his formed into a straight-line shape. In this way, the present embodiment shows the example configured of the restraining faces in which the antivibration restraining faces14a,14b, . . . , and14hare formed into flat planes.

The antivibration restraining faces Ha,11b, . . . ,11h,14a,14b, . . . , and14hprovided on the upper side surface4aand the lower side surface4bof the side surface4are not limited to the flat planar shapes as shown inFIG. 7.

As shown inFIG. 7, an inner diameter reduced portion5ais formed on an inner peripheral surface of the screw insertion hole5, and an inner diameter of the inner diameter reduced portion5agradually decreases toward the inside in the thickness direction so as to engage with a lower end portion of a head portion of a clamp screw35inserted into the screw insertion hole5when the circular cutting insert1is fixed to the seating surface33.

(Second Embodiment of Circular Cutting Insert)

Next, a second embodiment of the circular cutting insert of the present invention will be described.FIG. 8is a perspective view of a circular cutting insert25according to the second embodiment,FIG. 9is a side view of the circular cutting insert25, andFIG. 10is an enlarged view of the side view shown inFIG. 9. The cutting insert25according to the second embodiment is mainly different from the cutting insert1according to the above-described first embodiment as described in the following (1) and (2). In addition, the same reference numerals are assigned to configurations which are the same as those of the first embodiment, and descriptions thereof are omitted.

(1) In the second embodiment, in the eight planar restraining faces which are sequentially disposed on the upper side surface4aand the lower side surface4bof the side surface4in the circumferential direction, the ridgelines (side a and side e) which are the end portion of the adjacent two planar restraining faces are configured so as to be directly connected to each other. In the descriptions below, the portion connecting the ridgelines of the end portions of the adjacent two planar restraining faces to each other is referred to as a “joint ridgeline”. Joint portions26aand26bare joint portions which replace the joint portions12aand12bof the first embodiment and are each configured of a ridgeline having a minute width. In other words, in the second embodiment, the widths w of the joint portions12aand12bin the circumferential direction in the first embodiment are made extremely small so as to be the joint ridgelines26aand26b.

(2) According to the above (1), in the second embodiment, each of antivibration restraining faces27a,27b, . . . , and27his formed into a triangular shape (an isosceles triangular shape or an approximately isosceles triangular shape) when the cutting insert25is viewed from the side surface.

Moreover, the shape of each of the planar restraining faces provided on the cutting insert25in the second embodiment is substantially the same as that of the cutting insert1of the first embodiment, and thus, inFIGS. 8 to 10, the reference numerals assigned to the planar restraining faces10a,10b, . . . , and10hand the planar restraining faces13a,13b, . . . , and13hand the reference numerals assigned to the sides a, b, . . . , and f in the first embodiment are used as they are.

Hereinafter, characteristics of the cutting insert25of the second embodiment will be described. As shown inFIG. 10, in the eight planar restraining faces10a,10b, . . . , and10hwhich are sequentially disposed in the circumferential direction of the upper side surface4a, the ridgelines of each of the adjacent two planar restraining faces10aand10b,10band10c, . . . , and10hand10aare connected to each other through the minute joint ridgeline26a(having a minute circumferential width). As described above, in the joint ridgelines26a, the side a and side e which are end portions in the circumferential direction of each of the adjacent two planar restraining faces10aand10b,10band10c, . . . , and10hand10aare made to be one minute connection ridgeline, and thus, it is possible to form the connection ridgeline when press molding is performed using a mold to obtain a power molded body of the cutting insert25. In addition, preferably, in order to prevent chipping, the joint ridgelines26aare each molded so as to have a R shape when the press molding is performed, and after the powder molded body is sintered, the joint ridgelines26aare formed to be a ridgeline (curved surface) having a minute line width of approximately 0.2 R.

Similarly, in the eight planar restraining faces13a,13b, . . . , and13hwhich are sequentially disposed in the circumferential direction of the lower side surface4b, the adjacent two planar restraining faces13aand13b,13band13c, . . . , and13hand13aare each connected to each other in the circumferential direction through the joint ridgeline26b.

In the upper side surface4a, the eight antivibration restraining faces27a,27b, . . . , and27h, which are provided between the adjacent planar restraining faces10aand10b,10band10c, . . . , and10hand10athrough the joint ridgelines26a, are formed so as to each have a triangular shape when the cutting insert25is viewed from the side surface. The cutting insert25is the double-sided circular cutting insert, and thus, in order to secure the same performance of the cutting operation even when the use regions of the cutting edges6aand6bare changed, each of the eight antivibration restraining faces27a,27b, . . . , and27his formed into an isosceles triangular face or an approximately isosceles triangular face (an equilateral triangular face or an approximately equilateral triangular face) when the cutting insert25is viewed from the side surface.

As shown inFIG. 10, in the triangle of each of the antivibration restraining faces27a,27b, . . . , and27hof the upper side surface4a, the end portion of the joint ridgeline26acloser to the side surface-intermediate line (N) is a vertex (apex) (t3) of the triangle, the one side g on the side surface-intermediate line (N) is the base of the triangle facing the vertex (t3) as the apex, and the side b and the side d of the two planar restraining faces adjacent to each other through the joint ridgeline26aare inclined sides of the triangle. In addition, each of the antivibration restraining faces27a,27b, . . . , and27his formed so as to be an inclined face which is inclined downwardly from the vertex (t3) toward the base g (inclined radially inward with respect to the thickness direction), and is formed such that the length thereof in the circumferential direction of the side surface4gradually increases toward the side surface-intermediate line (N).

Similarly to the upper side surface4a, also in the lower side surface4b, the adjacent planar restraining faces13aand13b,13band13c, . . . , and13hand13aare connected to each other through the minute joint ridgelines26b, and each of antivibration restraining faces28a,28b, . . . , and28hprovided between the adjacent planar restraining faces is formed so as to have a triangular shape (an isosceles triangular shape or an equilateral triangular shape) when the cutting insert25is viewed from the side surface. In the triangle of each of the antivibration restraining faces28a,28b, . . . , and28h, the end portion of the joint ridgeline26bcloser to the side surface-intermediate line (N) is a vertex (apex) (t4) of the triangle, the one side c on the side surface-intermediate line (N) is the base of the triangle facing the vertex (t4) as the apex, and the side b and the side d of the two planar restraining faces adjacent to each other through the joint ridgeline26aare inclined sides of the triangle. In addition, each of the antivibration restraining faces28a,28b, . . . , and28his formed so as to be an inclined face which is inclined upwardly from the vertex (t4) toward the base c (inclined radially inward with respect to the thickness direction), and the length thereof in the circumferential direction of the side surface4gradually increases toward the side surface-intermediate line (N).

Moreover, preferably, the length of each of the joint ridgelines26aand26bof the upper side surface4aand the lower side surface4b, that is, the length of the side a or the side e in the direction of the central axis P of the screw insertion hole5is set to approximately 0.1 to 0.15 times the thickness of the circular cutting insert25.

The line showing the cross-sectional shape of each of the antivibration restraining faces shown in the view of the longitudinal section which passes through the central axis P of the screw insertion hole5of the cutting insert25according to the second embodiment and intersects with each antivibration restraining face, may be formed into a straight-line shape as shown inFIG. 7in the first embodiment or may be formed into a gentle convex-line shape or concave-line shape (FIG. 17).

In the first embodiment of the circular cutting insert of the present invention, the joint portion12aor12bhaving the predetermined width w is provided between the two planar restraining faces adjacent to each other in the circumferential direction of the side surface4, the adjacent planar restraining faces are connected to each other through the joint portions12a(12b), and thus, strength of the joint portions is secured. Meanwhile, in the second embodiment of the circular cutting insert, the two planar restraining faces adjacent to each other in the circumferential direction of the side surface4are connected to each other through the minute straight-line ridgeline (joint ridgeline26aor26b) (having the minute width) formed into an R shape. Accordingly, when a mold for press-molding the powder molded body of the circular cutting insert25of the second embodiment is compared with a mold for press-molding the powder molded body of the circular cutting insert1of the first embodiment, in the second embodiment, it is possible to simplify a structure of a mold cavity, and thus, the filling density of powder of the powder molded body can be made uniform.

In the region of the upper side surface4aof the circular cutting insert25according to the second embodiment, similarly to the circular cutting insert1according to the above-described first embodiment, at locations at which the planar restraining faces10aand10b,10band10c, . . . , and10hand10aadjacent in the circumferential direction of the upper side surface4aare connected to each other through the joint ridgelines12a, regions including a predetermined range of planar restraining faces in the upper side surface4afrom the sides a and the sides e of the adjacent two planar restraining faces10aand10b, . . . form the corners (corner portions) which have the joint ridgelines26aas protruding center portions. The corners have shapes protruding to the outside of the cutting insert25from the planar restraining faces13a,13b, . . . , and13hwhich are disposed on the lower side surface4bto correspond (face) the disposed positions of the corners. In other words, the corners are each disposed radially outside the planar restraining faces13a,13b, . . . , and13hpositioned at the same positions in the circumferential direction. In addition, the corners are disposed radially inside the cutting edge6aof the upper side surface4a.

Similarly to the cutting insert1of the above-described first embodiment, the corners formed by the adjacent two planar restraining faces10aand10b,10band10c, . . . , and10hand10aare used as antirotation surfaces19a,19b, (not shown inFIG. 10) described later, that is, as a means of preventing the rotation of the circular cutting insert25when the circular cutting insert25is attached to the insert mounting seat32of the indexable rotary cutting tool30.

Similarly to the upper side surface4a, also in the lower side surface4bof the circular cutting insert25, the locations at which the adjacent planar restraining faces13aand13b,13band13c, . . . , and13hand13aare connected to each other through the joint ridgelines26band regions around the locations form corners (corner portions), and the corners are used as a means (antirotation surfaces20a,20b, . . . , and20h) (not shown) of preventing the rotation of the circular cutting insert25.

(Embodiment of Indexable Rotary Cutting Tool)

Next, in the indexable rotary cutting tool to which the above-described double-sided circular cutting insert of the present invention is attached, an embodiment thereof and a restraining structure for attaching the circular cutting insert to the insert mounting seat so as to restrain the circular cutting insert will be described with reference toFIGS. 11 to 16. Here, in the following descriptions of the indexable rotary cutting tool, a direction along a rotational axis of the indexable rotary cutting tool is referred to as an axial direction, a direction orthogonal to the rotational axis is referred to as a radial direction (radial direction of the tool main body), and a direction around the rotational axis is referred to as a circumferential direction (circumferential direction of the tool main body).

FIG. 11is a perspective view showing an example of an indexable rotary cutting tool30according to the present embodiment to which the circular cutting inserts1of the first embodiment are attached. The indexable rotary cutting tool30is configured of the tool main body31. The tool main body31includes a plurality of insert mounting seats32which are formed with a predetermined interval therebetween along an outer peripheral portion31cof a tip portion31athereof. The insert mounting seats32each have the same shape as each other and are provided at equal intervals in the circumferential direction of the tool main body31so as to be rotationally symmetrical about a rotational axis O.FIG. 11shows an example in which three insert mounting seats32are provided at intervals of120degrees about the rotational axis O of the tool main body31. In addition, each of the insert mounting seats32is provided in a region which is formed by notching the tip portion31ahaving an approximately doughnut shape about the rotational axis O to form a surface which is approximately parallel in the radial direction and the axial direction with respect to the tool main body31from a tip in the axial direction and faces the rotation direction of the tool main body31and a surface which is approximately perpendicular to the surface. The circular cutting insert1is attached to each insert mounting seat32, and the cutting insert1is firmly fixed to the insert mounting seat32by tightening the clamp screw35. A rear end portion31bof the tool main body31is a portion for joining with an arbor member attached to a main spindle of a machine tool for performing the cutting operation. A reference numeral “R” shown inFIG. 11indicates a direction in which the tool main body31rotates about the rotational axis O when the cutting operation is performed on a workpiece. Here, a direction from the rear end portion31bof the tool main body31toward the tip portion31aalong the axial direction is referred to a tip side in the axial direction, and a direction opposite thereto is referred to as a rear end side in the axial direction. In addition, in the radial direction of the tool main body31, a direction approaching the rotational axis O is referred to as an inside of the tool main body31in the radial direction, and a direction separated from the rotational axis O is referred to as an outside of the tool main body31in the radial direction. Moreover, in the circumferential direction of the tool main body31, a direction R in which the tool main body31rotates is referred to as a rotational direction R, and a direction opposite thereto is referred to as an opposite side of the rotational direction R.

FIG. 12is a perspective view of the insert mounting seat32for explaining a configuration of one of the plurality of insert mounting seats32provided on the tool main body31and shows a state before the circular cutting insert1is attached to the insert mounting seat32.

As shown inFIG. 12, the insert mounting seat32includes: a seating surface33; and a restraining wall (restraining wall surface) on which a first restraining wall38and a second restraining wall39are formed. The seating surface33is a surface facing the rotational direction R of the tool main body31and is a seating surface for seating the top surface flat portion8aor the bottom surface flat portion8bof the circular cutting insert1when the circular cutting insert1is attached to the insert mounting seat32. The seating surface33is a plane which extends so as to be approximately parallel to the tool main body31in the axial direction and the radial direction. A screw hole34is perforated at circular cutting insert1when the circular cutting insert1is attached to the insert mounting seat32and is fixed by tightening the clamp screw35. In other words, the screw hole34is a hole in which a female screw corresponding to a male screw of the clamp screw35is formed on an inner peripheral surface of the hole, and the screw hole34is screwed together with the male screw of the clamp screw35inserted into the screw insertion hole5when the circular cutting insert1is fixed.

The first restraining wall38is arranged in a direction substantially perpendicular to the seating surface33through a groove portion36a, and the second restraining wall39is arranged in a direction substantially perpendicular to the seating surface33through a groove portion36b. The first restraining wall38faces the tip side of the tool main body31in the axial direction. The second restraining wall39faces the outside of the tool main body31in the radial direction. A reference numeral “37” shown inFIG. 12is a relief portion which connects the first restraining wall38and the second restraining wall39to each other. Each of the groove portions36aand36bis a groove having an approximately cylindrical inner peripheral surface which extends along the seating surface33. The groove portion36ais positioned on the rear end side of the tool main body31in the axial direction from the seating surface33. The groove portion36bis positioned on the inside of the tool main body31in the radial direction from the seating surface33. In the rotation direction R of the tool main body31, groove bottoms of the groove portions36aand36b, that is, the surfaces facing the rotational direction R are positioned on the opposite side of the rotational direction R from the seating surface33. A groove wall of the groove portion36a, that is, a surface thereof facing the tip side in the axial direction is positioned on the rear side from a planar restraining wall surface40described later of the first restraining wall38in the axial direction of the tool main body31. A groove wall of the groove portion36b, that is, a surface thereof facing the outside in the radial direction is positioned on the inside from a second restraining wall39described later in the radial direction of the tool main body31.

The first restraining wall38and the second restraining wall39are restraining wall surfaces for exerting two or more functions among a function (indexing function) for restraining the circular cutting insert1at a predetermined position of the insert mounting seat32, a function (antirotation function) preventing the rotation (or turning) of the circular cutting insert1during a cutting operation of a workpiece, and a function (antivibration function) for preventing or suppressing vibrations generated during a cutting operation of a workpiece, with respect to the circular cutting insert1, when the circular cutting insert1is attached to the insert mounting seat32and is fixed by tightening the clamp screw35and after the circular cutting insert1is fixed. As shown inFIG. 12, the first restraining wall38and the second restraining wall39are formed so as to intersect with each other at an angle (β). More specifically, extended planes of the first restraining wall38and the second restraining wall39intersect with each other at the angle (β), and an inner end of the first restraining wall38in the radial direction and a rear end of the second restraining wall39in the axial direction are smoothly connected to each other through a recessed cylindrical surface-shaped relief portion37. Hereinafter, configurations and functions of the first restraining wall38and the second restraining wall39will be described.

As shown inFIG. 12, the first restraining wall38erects on the seating surface33through the groove portion36aprovided on the outer peripheral portion31cside of the tool main body31, and the planar restraining wall surface40and an antirotation wall surface41are formed on the surface of the first restraining wall38facing the seating surface33(facing the tip side in the axial direction). The planar restraining wall surface40is formed as a wall surface perpendicular to the seating surface33formed into a plane. The antirotation wall surface41is formed as an approximately V-shaped recessed portion41ahaving a predetermined depth. In other words, the recessed portion41ais formed by notching the planar restraining wall surface40into a columnar shape having an approximately triangular bottom surface which is separated from the seating surface33in the rotational direction R of the tool main body31and is approximately parallel to the seating surface33and a side surface which extends in a direction perpendicular to the seating surface33. The side surface of the recessed portion41aincludes: a planar portion which is connected to the planar restraining wall surface40to form an obtuse angle; and a curved surface portion which is smoothly connected to the planar portion in the inside of the tool main body31in the radial direction (FIG. 16). In addition, in the formation positions of the planar restraining wall surface40and the antirotation wall surface41with respect to the seating surface33, the planar restraining wall surface40are formed to be positioned below the antirotation wall surface41. That is, the planar restraining wall surface40and the antirotation wall surface41are formed (disposed) to provide a stage respect to the seating surface33. In other words, in a direction perpendicular to the seating surface33, the antirotation wall surface41is positioned to be further separated from the seating surface33than the planar restraining wall surface40(the antirotation wall surface41is disposed at a more distant position than the planar restraining wall surface40).

In the first restraining wall38, the planar restraining wall surface40of the planar restraining wall surface40and the antirotation wall surface41formed to provide a stage with respect to the seating surface33is a wall surface for restraining any one of the planar restraining faces13a,13b, . . . , and13hprovided on the lower side surface4bof the circular cutting insert1when the circular cutting insert1is attached and fixed to the insert mounting seat32. In other words, when the circular cutting insert1is fixed to the insert mounting seat32, the planar restraining wall surface40comes into surface contact with one of the planar restraining faces13a,13b, . . . , and13hof the lower side surface4bof the circular cutting insert1. Accordingly, the cutting insert1is positioned in the direction facing the planar restraining wall surface40.

Meanwhile, the V-shaped recessed portion41aformed on the antirotation wall surface41is a wall surface for engaging with any one of the corners (corner portions)15a,15b, . . . , and15hof the upper side surface4aof the circular cutting insert1, that is, any one of the antirotation surface19a,19b, . . . , and19hso as to restrain it. In other words, when the circular cutting insert1is fixed to the insert mounting seat32, the side surface of the recessed portion41acomes into contact with any one of the antirotation surfaces19a,19b, . . . , and19hof the upper side surface4aof the circular cutting insert1. Accordingly, as will be described later, it is possible to prevent the cutting insert1from rotating around the clamp screw35during the cutting operation.

In this way, the first restraining wall38is a restraining wall for simultaneously restraining any one of the planar restraining faces13a,13b,13c, . . . , and13hof the circular cutting insert I and any one of the antirotation surfaces19a,19b, . . . , and19hthereof. That is, the first restraining wall38mainly has the indexing function and the antirotation function. Accordingly, the formation positions of the planar restraining wall surface40and the antirotation wall surface41of the first restraining wall38formed to provide the stage with respect to the seating surface33are required to be determined in advance in consideration of a state where the circular cutting insert1is seated on and fixed to the seating surface33. Specifically, preferably, in a direction perpendicular to the seating surface33, a distance between a boundary between the antirotation wall surface41and the planar restraining wall surface40, that is, the bottom surface of the recessed portion41aand the seating surface33is set to be equal to or more than a distance from the top surface2of the cutting insert1to the apex portion (t1) of each of the antivibration restraining faces11a, . . . , and11hof the upper side surface4aand is set to be less than a distance from the top surface2to the apex portion (t2) of each of the antivibration restraining faces14a, . . . , and14hof the lower side surface4b. More preferably, the distance between the bottom surface of the recessed portion41aand the seating surface33is set to a distance from the top surface2of the cutting insert1to the intermediate plane (M).

The second restraining wall39includes the antivibration wall surface42and a planar restraining wall surface43formed to provide a stage with respect to the seating surface33. Specifically, the planar restraining wall surface43is a wall surface perpendicular to the seating surface33and is a plane extending along the groove portion36b. The angle β is formed between the planar restraining wall surface43and the planar restraining wall surface40of the first restraining wall38. The antivibration wall surface42forms an obtuse angle between the planar restraining wall surface43and the antivibration wall surface42and extends between the planar restraining wall surface43and the groove portion36b. In addition, the antivibration wall surface42is inclined to the inside of the tool main body31in the radial direction from one end of the planar restraining wall surface43toward the groove portion36b. Moreover, a ridgeline which is a boundary between the antivibration wall surface42and the planar restraining wall surface43is parallel to the seating surface33. In the present embodiment, the antivibration wall surface42is a plane.

The antivibration wall surface42is a wall surface for restraining any one of the antivibration restraining faces14a,14b,14c, . . . , and14hprovided on the lower side surface4bof the circular cutting insert1. The antivibration wall surface42is formed to have an inclined face so as to come into contact (surface contact) with the inclined face of the antivibration restraining face of the circular cutting insert1when the circular cutting insert1is attached to the insert mounting seat32. Accordingly, as will be described later, it is possible to prevent vibrations of the cutting insert1during the cutting operation.

Meanwhile, the planar restraining wall surface43is a wall surface for restraining any one of the planar restraining faces10a,10b,10c, . . . , and10hprovided on the upper side surface4aof the circular cutting insert1, that is, the planar restraining face corresponding to (facing) the position of the antivibration restraining face provided on the lower side surface4bof the circular cutting insert1coming into contact with (restraining) the antivibration wall surface42. In other words, the planar restraining wall surface43comes into surface contact with any one of the planar restraining faces10a,10b, . . . , and10hof the upper side surface4aof the circular cutting insert1when the circular cutting insert1is fixed to the insert mounting seat32. Accordingly, the circular cutting insert1is positioned in the direction facing the planar restraining wall surface43. In this way, the second restraining wall39mainly has the antivibration function and the indexing function.

Therefore, the formation positions of the antivibration wall surface42and the planar restraining wall surface43of the second restraining wall39formed to provide the stage with respect to the seating surface33are required to be determined in advance in consideration of the state where the circular cutting insert1is seated on and fixed to the seating surface33. Specifically, in the direction perpendicular to the seating surface33, preferably, a distance between a boundary between the antivibration wall surface42and the planar restraining wall surface43and the seating surface33is set to be the same as the distance from the top surface2(bottom surface3) of the cutting insert1to the intermediate plane (M).

In addition, the above-described intersecting angle (β) at which the first restraining wall38and the second restraining wall39intersect with each other is set to 67.5 degrees (90 degrees−(360 degrees/(2×8 corners))) in a case where the (eight-corner type) circular cutting insert1of an embodiment in which the eight planar restraining faces and the eight antivibration restraining faces are disposed in each of the upper side surface4aand the lower side surface4bis attached to the insert mounting seat32. In addition, in a case where a six-corner type circular cutting insert (the circular cutting insert in which six planar restraining faces and six antivibration restraining faces are provided in each of the upper side surface4aand the lower side surface4b) is attached, the intersecting angle (β) is set to 60 degrees (90 degrees−(360 degrees/(2×6 corners))). In this way, in the present embodiment, the angle β is set according to the angle formed between two planar restraining faces each abutting on the planar restraining wall surfaces40and43in a case where the circular cutting insert1is attached to the insert mounting seat32. Moreover, as will be described later, preferably, the angle β is set to an acute angle.

Any one of the bottom surface flat portion8bof the bottom surface3or the top surface flat portion8aof the top surface2of the circular cutting insert1shown inFIG. 13is seated on the seating surface33of the insert mounting seat32shownFIG. 12, and the circular cutting insert1can be detachably attached and fixed to the insert mounting seat32by tightening the clamp screw35.

For example, in the operation of attaching and fixing the circular cutting insert1to the insert mounting seat32, in a case where an unused cutting edge6aof the top surface2is used for the cutting operation, as shown by a thick line arrow inFIG. 13, the bottom surface3(bottom surface flat portion8b) of the cutting insert1is attached to the seating surface33while moving in a transverse direction (a direction parallel to the seating surface) to be parallel to the seating surface33from a front side of the seating surface33(the outside of the tool main body31in the radial direction), and thus, any one of the antirotation surfaces19a,19b, . . . , and19hprovided on the upper side surface4aof the circular cutting insert1engages with the recessed portion41aof the antirotation wall surface41. In other words, in the two planar restraining faces10a,10b, . . . , and10hconfiguring any one of the antirotation surfaces19a,19b, . . . , and19h(corner portions15a,15b, . . . , and15h), the planar restraining face facing the direction in which the clamp screw35rotates when the cutting insert1is fixed, abuts on the planar portion on the side surface of the recessed portion41a. Preferably, the surfaces come into surface contact with each other. According to this operation, the planar restraining faces disposed on the lower side surface4bside of the circular cutting insert1facing the antirotation surface engaging with the recessed portion41aof antirotation wall surface41come into contact with the planar restraining wall surface40of the first restraining wall38. In other words, the planar restraining faces of the lower side surface4bdisposed at the same position as that of the antirotation surface in the circumferential direction of the circular cutting insert1come into surface contact with the planar restraining wall surface40.

FIG. 14shows the state when the circular cutting insert1is attached and fixed to the insert mounting seat32and is a view when the tip portion31aof the tool main body31is viewed from the front side (the tip side in the axial direction). An arrow F shown inFIG. 14indicates a cutting force acting on the top surface2of the circular cutting insert1when the cutting operation is performed using the cutting edge6aprovided on the top surface2of the circular cutting insert1.

FIG. 15is a view when the tool main body31is viewed from the top surface2of the circular cutting insert1(from the opposite side of the rotation direction R) in the case where the circular cutting insert1is attached and fixed to the insert mounting seat32inFIG. 14. A reference numeral “L” shown inFIG. 15indicates the lowest point of the indexable rotary cutting tool30in the direction of the rotational axis O. In general, in a case where a cutting operation of a workpiece is performed by the indexable rotary cutting tool30to which the circular cutting insert1is attached, in the cutting edge6aformed into a circular shape, a cutting edge positioned within a range from the lowest point L to 45 degrees in the direction toward the outer peripheral portion31cof the tool main body31(toward the outside of the tool main body31in the radial direction) about the central axis P of the screw insertion hole5is used.

(Restraining Structure of Insert Mounting Seat for Restraining Circular Cutting Insert)

Next, when the circular cutting insert1is attached to the insert mounting seat32of the tool main body31and is fixed by tightening the clamp screw35, a restraining structure (restraining relationship) of the insert mounting seat32of the tool main body31for restraining the circular cutting insert1will be described. The “restraining” means that the first restraining wall38and the second restraining wall39provided on the insert mounting seat32of the tool main body31restrain an appropriate portion (come into contact with an appropriate portion) of the side surface4of the circular cutting insert1(or the circular cutting insert25) such that the indexable rotary cutting tool30to which the circular cutting insert1of the first embodiment (or the circular cutting insert25of the second embodiment) is attached exerts the above-described “indexing function”, “antirotation function”, and “antivibration function”.

FIG. 16is a sectional view showing a state where the circular cutting insert1of the first embodiment is attached (fixed) to the insert mounting seat32of the indexable rotary cutting tool30shown inFIG. 12,FIG. 16(a)is a view when the cross-sections of the tool main body31and the circular cutting insert1taken along the intermediate plane (M) of the circular cutting insert1are viewed from the top surface2side, andFIG. 16(b)is a view when the cross-sections of the tool main body31and the circular cutting insert1taken along line A-A shown inFIG. 4are viewed from the top surface2side. InFIGS. 16(a) and 16(b), for simplification of explanation, the joint portions12aand12bare not shown. The “β” shown inFIG. 16(a)is the angle (β) shown inFIG. 12and indicates the angle (β) at which the first restraining wall38and the second restraining wall39intersect with each other.

Moreover,FIG. 16is a view for explaining the restraining structure for the insert mounting seat32, which is the characteristic of the present embodiment, to restrain the circular cutting insert1when the circular cutting insert1is attached and fixed to the insert mounting seat32. Hereinafter, this restraining structure will be described with reference toFIG. 16.

(Restraining Structure of First Restraining Wall38for Restraining Circular Cutting Insert)

The restraining structure of the first restraining wall38for restraining the side surface4of the circular cutting insert1includes the following first restraining structure and second restraining structure.

The first restraining structure is a structure in which the corner portions15a, . . . , and15h(16a,. . . , and16h) (antirotation surfaces19a, . . . , and19h(20a, . . . , and20h)) of the circular cutting insert1and the antirotation wall surface41(the approximately V-shaped recessed portion41a) of the insert mounting seat32engage with each other. As shown inFIG. 16(b), the corner (corner portion)15hwhich is the antirotation surface19hof the upper side surface4aof the circular cutting insert1engages with the approximately V-shaped recessed portion41aof the antirotation wall surface41provided on the first restraining wall38.FIG. 16(b)shows the first restraining structure in which the corner15h(antirotation surface19h) which is one of the corners provided on the upper side surface4aof the circular cutting insert1is fitted into and engages with the recessed portion41a. In other words, in the first restraining structure, the corner portion15his inserted into the recessed portion41a, and a portion of the planar restraining face10hconfiguring the corner portion15h(antirotation surface19h) comes into surface contact with the planar portion on the side surface of the recessed portion41a.

Moreover, as shown inFIG. 16(b), in this engagement relationship, when the circular cutting insert1is fixed to the insert mounting seat32by tightening the clamp screw35in a right-handed rotation (clockwise direction inFIG. 16(b)), in the V-shaped recessed portion41a, a right wall surface on the paper surface ofFIG. 16(b)(the planar portion on the side surface of the recessed portion41a) comes into contact with and engages with one planar portion of the corner15h(planar restraining face10h). In addition, as shown inFIG. 14, in the cutting force F acting on the circular cutting insert1during the cutting operation of the workpiece, a component force of the cutting force F acts on the circular cutting insert1shown inFIG. 16(b)in the clockwise direction. Accordingly, the engagement relationship (first restraining structure) between the approximately V-shaped recessed portion41aof the antirotation wall surface41and the corner15h(antirotation surface19h) of the circular cutting insert1exerts the above-described antirotation function of preventing the rotation of the circular cutting insert1during the cutting operation.

The second restraining structure is a structure in which the planar restraining face13a, . . . , and13h(10a, . . . , and10h) of the circular cutting insert1and the planar restraining wall surface40of the insert mounting seat32engage with each other.FIG. 16(a)shows a restraining structure in which the planar restraining wall surface40provided on the first restraining wall38of the insert mounting seat32engages with the planar restraining face13hamong the planar restraining faces13a,13b,13c, . . . , and13hprovided on the lower side surface4bof the circular cutting insert1in planes. In other words, in the second restraining structure, the planar restraining face13hcomes into surface contact with the planar restraining wall surface40. This restraining structure exerts a function (indexing function) for positioning the circular cutting insert1at an accurate position of the insert mounting seat32without errors in cooperation with a third restraining structure described later.

In this way, the planar restraining wall surface40and the recessed portion41aof the antirotation wall surface41formed into a V shape to provide a stage on the first restraining wall38each restrain one of the planar restraining faces13a, . . . , and13hof the lower side surface4bof the circular cutting insert1and one of the antirotation surfaces19a, . . . , and19hof the upper side surface4adisposed so as to face the planar restraining faces in the thickness direction. More specifically, the planar restraining wall surface40and the planar portion of the recessed portion41aprovided on the first restraining wall38intersect with each other at a predetermined angle. Accordingly, a rotation suppression force acting on one of the antirotation surfaces19a, . . . , and19hof the upper side surface4aand a restraining force acting on one of the planar restraining faces13a, . . . , and13hof the lower side surface4bact in a direction against a turning force generated around the central axis P of the screw insertion hole5of the cutting insert1. In addition to this, the rotation suppression force and the restraining force effectively prevent rotational fine motions or vibrations in the clockwise direction and the counterclockwise direction generated around the central axis P during the cutting operation, in cooperation with the third restraining structure described later. In addition, the rotation suppression force and the restraining force also exert the indexing function for preventing an erroneous attachment of the circular cutting insert1.

(Restraining Structure of Second Restraining Wall39for Restraining Circular Cutting Insert)

The restraining structure of the second restraining wall39for restraining the side surface4of the circular cutting insert1includes the following third restraining structure and fourth restraining structure.

The third restraining structure is a structure in which the planar restraining faces10a, . . . , and10h(13a, . . . , and13h) of the circular cutting insert1and the planar restraining wall surface43provided on the second restraining wall39of the insert mounting seat32engage with each other.FIG. 16(b)shows a restraining structure in which the planar restraining wall surface43of the second restraining wall39shown inFIG. 16(b)engages with one planar restraining face10camong the planar restraining faces10a,10b,10c, . . . , and10hof the upper side surface4aof the circular cutting insert1. In other words, in the third restraining structure, the planar restraining face10ccomes into surface contact with the planar restraining wall surface43. The third restraining structure contributes to highly exert the indexing function for positioning the circular cutting insert1at an accurate position of the insert mounting seat32without erroneous operations when the circular cutting insert1is attached to the insert mounting seat32, in cooperation with the second restraining structure in which the planar restraining wall surface40of the first restraining wall38of the second restraining structure engages with the planar restraining face13hprovided on the lower side surface4bof the circular cutting insert1in planes.

The reason why the indexable rotary cutting tool of the present embodiment can highly exert the above-described indexing function is in the following (1) and (2).

(1) One of the planar restraining faces13a, . . . , and13hprovided on the lower side surface4bof the circular cutting insert1is restrained by the planar restraining wall surface40of the first restraining wall38, one of the planar restraining faces10a, . . . , and10hprovided on the upper side surface4aof the circular cutting insert1is restrained by the planar restraining wall surface43of the second restraining wall39, and the planar restraining wall surface40of the first restraining wall38and the planar restraining wall surface43of the second restraining wall39are formed so as to face (intersect with) each other at the intersecting angle β (the angle which is the same as the angle formed between one of the planar restraining faces13a, . . . , and13hon which the planar restraining wall surface40abuts and one of the planar restraining faces10a, . . . , and10hto which the planar restraining wall surface43abuts) which is an acute angle. Accordingly, when the clamp screw35is loosened and an operation for reattaching the circular cutting insert1is performed or when an operation for attaching a new cutting insert1is performed, it is possible to position the circular cutting insert1at an accurate position of the insert mounting seat32without erroneous attachment.

(2) When the circular cutting insert1is attached to the insert mounting seat32, it is necessary to cause one of the antirotation surfaces19a, . . . , and19h(20a, . . . , and20h) of the circular cutting insert1to be fitted to (to engage with) the V-shaped recessed portion41aof the antirotation wall surface41provided on the first restraining wall38of the insert mounting seat32. Accordingly, it is possible to reliably prevent the circular cutting insert1from being erroneously attached to the insert mounting seat32.

The fourth restraining structure is an engagement structure generated by the contact between the antivibration restraining faces11a, . . . , and11h(14a, . . . , and14h) of the circular cutting insert1and the antivibration wall surface42provided on the second restraining wall39of the insert mounting seat32. In the second restraining wall39of the insert mounting seat32shown inFIG. 16(a), the portion indicated by the reference numeral14bis one of the antivibration restraining faces14a,14b, . . . , and14hprovided on the lower side surface4bof the circular cutting insert1.FIG. 16(a)shows that the antivibration restraining face14bcomes into contact with and engages with the antivibration wall surface42of the second restraining wall39. The antivibration wall surface42is an inclined face which comes into engagement contact with (comes into surface contact with) the inclined face of each of the inclined antivibration restraining faces14a,14b, . . . , and14hof the circular cutting insert1, and thus is not shown inFIG. 16(a). Accordingly, inFIG. 16(a), a region formed by the antivibration wall surface42is shown by a dotted line.

InFIG. 14(FIG. 13) showing the state where the circular cutting insert1is viewed in an arrow Y direction shown inFIG. 16(b), it is shown that the antivibration wall surface42of the second restraining wall39is formed as an inclined face inclined in a direction separated from the screw hole34. In other words, the antivibration wall surface42is a surface which extends to be inclined in the rotation direction R from the inside of the tool main body31in the radial direction toward the outside thereof. In addition,FIG. 14in which the circular cutting insert1is attached shows the state where the antivibration restraining face14bprovided on the lower side surface4bof the circular cutting insert1comes into engagement contact (comes into surface contact) with the antivibration wall surface42of the second restraining wall39. The fourth restraining structure exerts a function (antivibration function) for preventing or suppressing occurrence of vibrations during the cutting operation of the workpiece in the present embodiment.

In addition, as shown inFIG. 12, the antivibration wall surface42of the second restraining wall39is formed along the inclined face as the lower end portion of the planar restraining wall43and the length of the formed antivibration wall surface42is approximately the same as the length of the planar restraining wall surface43. Accordingly, when the circular cutting insert1is attached to the insert mounting seat32as shown inFIG. 13, an attachment operation of the circular cutting insert1is easily performed, and erroneous operations at the time of the attachment can be prevented.

In the above-described fourth restraining structure, the reason why the contact and engagement between the antivibration wall surface42of the second restraining wall39and the antivibration restraining face14hprovided on the lower side surface4bof the circular cutting insert1exert the function for preventing or suppressing the occurrence of vibrations is as follows.

In the indexable rotary cutting tool30to which the circular cutting insert1is attached, it is considered that in the cutting force acting on the cutting edge6a(6b), a component force in a circumferential tangential direction in a rotation trajectory of the cutting edge6a(6b) of the cutting tool30largely contributes to the occurrence of the vibrations of the cutting insert1. Accordingly, in the antivibration function of the above-described indexable rotary cutting tool30of the present embodiment, the antivibration restraining faces11a,11b, . . . , and11hand the antivibration restraining faces14a,14b, . . . , and14hare provided on the upper side surface4aand the lower side surface4bof the double-sided circular cutting insert1such that a portion except for the clamp screw35can receive a repulsive force with respect to the component force in the circumferential tangential direction in the rotation trajectory. In addition, when the circular cutting insert1is attached to the insert mounting seat32, the inclined face of the antivibration restraining face of the circular cutting insert1comes into contact with the antivibration wall surface42(refer toFIG. 14).

In addition, when the cutting operation of the workpiece is performed in a state where the inclined face of one antivibration restraining face of the circular cutting insert1comes into contact with the antivibration wall surface42, if vibrations are generated by a cutting force, the vibrations exerts an operation of pressing the antivibration restraining face on the circular cutting insert1side to the antivibration wall surface42. The operation of pressing is caused by the component force of the cutting force in the circumferential tangential direction in the rotation trajectory of the cutting edge6a(6b) of the cutting tool. The antivibration restraining face and the antivibration wall surface42come into surface contact with each other, and with respect to this pressing force, the antivibration wall surface42of the insert mounting seat32receives the component force of the cutting force in the circumferential tangential direction. Accordingly, the antivibration wall surface42come into strong engagement-contact with the antivibration restraining face of the circular cutting insert1and exerts effects of preventing or suppressing of occurrence of the vibrations while maintaining the restraining force.

In addition, as described above, the antivibration wall surface42has the surface inclined to come into engagement contact with (come into surface contact with) the inclined face of the antivibration restraining face of the circular cutting insert I, and thus it is possible to increase an area receiving the component force of the cutting force in the circumferential tangential direction in the rotation trajectory of the cutting edge6a(6b) of the cutting tool30. Accordingly, it is possible to further increase effects for preventing the occurrence of the vibrations during the cutting operation. In addition, the antivibration wall surface42restrains the antivibration restraining face formed at the position separated from the screw insertion hole5on the side surface (the sides of the upper side surface4aand the lower side surface4bwhich do not have the cutting edge used for the cutting operation) of the circular cutting insert1at the position away from the cutting edge used during the cutting operation (within the range of 45 degrees from the lowest point L of the cutting edge6ashown inFIG. 15toward the outer peripheral portion31cof the tool main body31(toward the outside of the tool main body31in the radial direction), and thus, it is possible to increase the effect of preventing the occurrence of vibrations.

The above-described first to fourth restraining structures can be also provided in the indexable rotary cutting tool30to which the circular cutting insert25of the second embodiment is attached, and thus, descriptions thereof are omitted.

(Structure of Inclined Face of Antivibration Restraining Face)

FIG. 7shows the example in which the inclined faces of the antivibration restraining faces of the circular cutting insert1are each formed into a flat surface shape. However, the inclined faces adopt a structure shown inFIG. 17.

As shown by dotted line circles inFIG. 17(a),FIG. 17(a)shows an example in which in the longitudinal section which passes through the central axis P of the screw insertion hole5of the cutting insert1and intersects with the antivibration restraining faces14dand14h, the shapes of the cross-sections of the antivibration restraining faces14dand14hare formed into gentle convex lines, andFIG. 17(b)shows an example in which the shapes of the cross-sections of the antivibration restraining faces14dand14hare formed into gentle concave lines. In this way, compared to the case where the shapes of the cross-sections of the restraining faces are formed into a flat surface shapes shown inFIG. 7, in the case where the shape of the cross-sections of the surfaces of all the antivibration restraining faces11a,11b, . . . , and11hand all the antivibration restraining faces14a,14b, . . . , and14h, including the antivibration restraining faces14dand14h, are formed into gentle convex lines or gentle concave lines, it is possible to surface areas of the antivibration restraining faces. Accordingly, the force receiving the component force of the cutting force increases, and thus, effects for preventing the occurrence of vibrations increase.

The shapes of the cross-sections of the above-described antivibration restraining faces11ato11hand14ato14hcan be also applied to the circular cutting insert25of the second embodiment.

In addition, as shown inFIG. 17(a), in the case where the shapes of the cross-sections of the antivibration restraining faces of the cutting insert1(25) are formed into gentle convex lines, the antivibration wall surface42of the insert mounting seat32is formed into a concave line corresponding to the convex line. As shown inFIG. 17(b), in the case where the shapes of the cross-sections of the antivibration restraining faces are formed into gentle concave lines, the antivibration wall surface42of the insert mounting seat32is formed into a convex line corresponding to the concave line. Therefore, the antivibration restraining face of the cutting insert1(25) and the antivibration wall surface42of the insert mounting seat32come into surface contact with each other when the cutting insert1(25) is fixed to the insert mounting seat32, and thus, the above-described antivibration functions are exerted.

In the indexable rotary cutting tool30to which the above-described eight-corner type double-sided cutting insert1(25) is attached, for example, with respect to the cutting edge6aprovided on the top surface2of the cutting insert1(25), by repeating the reattachment of the cutting insert1, the eight regions of the cutting edges6acan be sequentially used in the cutting operation. In addition, after all the regions of the cutting edge6aof the top surface2are used, in order to use the cutting edge6bof the bottom surface3of the cutting insert1(25), the top surface2and the bottom surface3are inverted to be reattached to the insert mounting seat32, and thus, an unused cutting edge6bof the bottom surface3can be used in the cutting operation. Therefore, in one cutting insert1, total16cutting edge regions can be used in the cutting operation.

Accordingly, in a case where all the cutting edge regions of the cutting edge6aon the top surface2of the above-described double-sided cutting insert1(25) are used and the top surface2and then the bottom surface3are inverted to be reattached to the insert mounting seat32in order to use the cutting edge6bof the bottom surface3of the cutting insert1(25), in the “top surface2” and the “bottom surface3” in the descriptions of the above-described embodiments, it is obvious that the surface having the cutting edge used in the cutting operation indicates the top surface2.

In the indexable rotary cutting tool30according to the embodiments of the present invention, the positional relationship between the first restraining wall38and the second restraining wall39shown inFIG. 12may be reversed to the right and left, that is, the second restraining wall39may be formed and disposed on the right side on the paper surface ofFIG. 12, and the first restraining wall38may be formed and disposed on the left side on the paper surface ofFIG. 12.

(Manufacturing Method of Circular Cutting Insert and Tool Main Body)

Next, outlines of manufacturing methods of the circular cutting insert1(25) according to the embodiments of the present invention and the tool main body31to which the cutting insert1is attached, will be described.

It is desirable that a material of the circular cutting insert1of the embodiment is a hard material such as WC (tungsten carbide)-Co (cobalt) base cemented carbide which is widely adopted in the related art. In a case where the circular cutting insert1is made of cemented carbide, the outline of the manufacturing method of the circular cutting insert1is as follows.

(1) A pressed molded body of the circular cutting insert1is produced by pressurization-molding (press-molding) cemented carbide powder in which Co powder and a binder are added to WC powder using a powder molding apparatus using a mold (molding step). The side surface4of the circular cutting insert1has a complicated configuration, and thus, it is necessary to mold the pressed molded body formed by powder molding such that density of the cemented carbide powder becomes uniform. Accordingly, it is desirable to use as the powder molding apparatus used in the press molding, a powder molding apparatus having multi-axial specifications such as three axes or four axes.

(2) Subsequently, by firing the press molded body at a temperature of 1300 to 1450° C. for a predetermined time in a sintering furnace, a circular cutting insert made of a sintered body having a high hardness can be obtained (firing step). In the circular cutting insert manufactured through the firing step, finishing machine may be applied to a necessary portion of the circular cutting insert using a diamond grindstone or the like. In addition, the cutting insert1(25) of the present embodiment may be made of a hard material such as cermet or ceramics in addition to the above-described cemented carbide.

The tool main body31can be manufactured by cutting a round rod material made of alloy tool steel such as SKD 61 using an NC controlled processing machine. The insert mounting seat32can be formed by a cutting operation using an end mill or the like. In addition, desirably, the detailed shape of the insert mounting seat32is subjected to precise machining using a small-diameter end mill or the like.

Moreover, in the cutting insert1as the first embodiment of the above-described circular cutting insert of the present invention, the example is described in which each of the antivibration restraining faces11a,11b, . . . , and11hand the antivibration restraining faces14a,14b, . . . , and14hdisposed on the side surface4is formed into an isosceles trapezoid when the circular cutting insert is viewed from the side surface. However, the antivibration restraining faces11a,11b, . . . ,11h,14a,14b, . . . , and14hmay be formed into an isosceles triangle when the circular cutting insert1(25) is viewed from the side surface as in the cutting insert25of the second embodiment. In this case, the center portion of each of the joint portions12aand12bhaving the minute width w closer to the side surface-intermediate line (N) is the vertex which is the apex of the isosceles triangle.

The indexable rotary cutting tool30according to the embodiment of the present invention is used in engraving machining or a cutting operation of a free curved surface on the surface of a rotary blade or the like in addition to general plane machining at high speed in a cutting operation of a workpiece, and the indexable rotary cutting tool30can improve surface accuracy on the machined surface of the workpiece and remarkably improve tool life.

The present invention is not limited to the above-described embodiments, the configurations (constituent elements) described in the above-described embodiments, a modification example, an explanatory note, or the like may be combined within a scope which does not depart from the gist of the present invention, and addition, omission, replacement, or other modification of the configurations are possible. Moreover, the present invention is not limited by the above-described embodiments and is limited only by the claims.

INDUSTRIAL APPLICABILITY

The double-sided circular cutting insert and the indexable rotary cutting tool of the present invention have a high indexing function, antirotation function, and antivibration function, and thus, according to the present invention, it is possible to improve the surface accuracy of a machined surface of a workpiece and remarkably improve tool life.

REFERENCE SIGNS LIST

1: circular cutting insert of first embodiment (double-sided circular cutting insert)

2: top surface

3: bottom surface

4: side surface

4a: upper side surface

4b: lower side surface

5: screw insertion hole

5a: inner diameter reduced portion

6a,6b: cutting edge

8a: top surface flat portion

8b: bottom surface flat portion

12a: joint portion of upper side surface4a

12b: joint portion of lower side surface4b

25: circular cutting insert (double-sided circular cutting insert) of second embodiment

26a: joint ridgeline of upper side surface4a

26b: joint ridgeline of lower side surface4b

30: indexable rotary cutting tool

31: tool main body

31a: tip portion

31b: rear end portion

31c: outer peripheral portion

32: insert mounting seat

33: seating surface

37: relief portion

38: first restraining wall

39: second restraining wall

40: planar restraining wall surface of first restraining wall38

41: antirotation wall surface of first restraining wall38

42: antivibration wall surface of second restraining wall39

43: planar restraining wall surface of second restraining wall39

M: intermediate plane of circular cutting insert

N: side surface-intermediate line of circular cutting insert

O: rotational axis of indexable rotary cutting tool (tool main body)

P: central axis of screw insertion hole5

a, b, c, d, e, f: each side of planar restraining face formed into a hexagonal shape

g: lower base of antivibration restraining face which is disposed on upper side surface and formed into a trapezoidal shape or a triangular shape

l: length of side f of planar restraining face

m: length of side c of planar restraining face provided on side surface-intermediate line (N)

S: region functioning as antirotation surface

t1: apex portion (upper base) of antivibration restraining face disposed on upper side surface4a

t2: apex portion (upper base) of antivibration restraining face disposed on lower side surface4b

t3: vertex of antivibration restraining face formed on upper side surface4a

t4: vertex of antivibration restraining face formed on lower side surface4b

β: intersecting angle between first restraining wall and the second restraining wall