JP7239864B2 - Cutting inserts and indexable rotary cutting tools - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cutting insert suitable for face milling (flat surface milling) and side milling (vertical wall milling) of a work material, and an indexable rotary cutting tool equipped with the same.

2. Description of the Related Art Conventionally, solid-type end mills, such as those disclosed in Patent Documents 1 and 2 below, are known. This type of end mill has a shank that rotates around a central axis and a cutting edge formed at the tip of the shank. In addition, among the cutting edge portions, an arc-shaped bottom cutting edge that is convex toward the tip side is arranged at the tip portion in the central axis direction, and a bottom cutting edge that is convex toward the tip side is arranged at the outer end portion in the radial direction. A peripheral cutting edge is arranged which has an arcuate shape that is convex toward the edge.
The bottom cutting edge is used for face milling (flat milling) of the work material, and the peripheral cutting edge is used for side milling (upright wall milling). .

Japanese Patent Publication No. 2010-520064 JP 2007-152502 A

However, the above conventional end mill has the following problems.
When performing face milling on the work material, the cutting marks (machining marks, machining marks) given to the machined surface by cutting with the bottom cutting edge, and when performing side milling, the peripheral cut It was difficult to finish the saw marks imparted to the machined surface by cutting with a blade to have the same properties as each other. That is, the properties of the machined surface after cutting varied depending on the machined portion and shape of the work material, and it was not possible to equalize the machining accuracy of the machined surface as a whole in finish machining, semi-finishing, and the like.

The present invention has been made in view of such circumstances, and is a cutting insert capable of performing cutting so that the properties of the machined surface are uniform regardless of the machining site or shape of the work material. , and an indexable rotary cutting tool using the same.

One aspect of the present invention is a cutting insert detachably attached to a mounting seat formed at the tip of a tool body that is rotated around a central axis, comprising a plate-shaped insert body and a The cutting edge portion is disposed at the tip portion of the insert body in the central axis direction, extends along the radial direction perpendicular to the central axis, and extends along the central axis. A bottom cutting edge having an arc shape that is convex toward the distal end side of the direction; A rake face and an arc-shaped outer peripheral cutting edge that protrudes toward the radial direction, and the outer end of the bottom cutting edge in the radial direction and the tip of the outer peripheral cutting edge in the central axis direction are directly connected. In addition, the radius of curvature of each of the bottom cutting edge and the outer peripheral cutting edge is larger than 1/2 of the cutting edge diameter of the cutting edge portion, and is 45° with respect to the central axis when the rake face is viewed from the front. The bottom cutting edge and the outer peripheral cutting edge form line symmetry with respect to an imaginary straight line that intersects at an angle of and extends toward the tip side in the central axis direction as it goes outward in the radial direction as an axis of symmetry. It is characterized by being formed as follows.
Further, one aspect of the present invention is a cutting insert detachably attached to a mounting seat formed at the tip of a tool body that is rotated around a central axis, comprising a plate-shaped insert body, the insert a cutting edge portion formed in a main body, the cutting edge portion being arranged at a tip portion of the insert body in the central axis direction, extending along a radial direction orthogonal to the central axis, and A bottom cutting edge having an arc shape that protrudes toward the tip side in the central axis direction; and a rake face, the radius of curvature of the bottom cutting edge and the radius of curvature of the bottom cutting edge are the same, and the bottom The outer end of the cutting edge in the radial direction and the tip of the outer peripheral cutting edge in the central axis direction are directly connected, and each curvature radius of the bottom cutting edge and the outer peripheral cutting edge is the edge of the cutting edge portion A straight line larger than 1/2 of the diameter and extending along the radial direction passing through the tip of the bottom cutting edge in the central axis direction when viewed from the front is defined as the outer peripheral cutting edge. A straight line extending along the central axis direction passing through the radial outer end of the bottom cutting edge is defined as a central axis direction reference line, and a tangent line to the bottom cutting edge at the radial outer end of the bottom cutting edge is defined as a first tangent line , the tangent line of the outer peripheral cutting edge at the tip of the outer peripheral cutting edge in the central axis direction is defined as a second tangent line, the intersection of the first tangent line and the radial reference line, the first tangent line and the central axis A right-angled triangle formed by connecting the intersection of the direction reference line and the intersection of the radial reference line and the central axis direction reference line with straight lines is defined as a first right-angled triangle, and the second tangent line and the A point of intersection with the central axis direction reference line, an intersection point of the second tangent line and the radial direction reference line, and an intersection point of the radial direction reference line and the central axis direction reference line are formed by connecting each other with straight lines. The right-angled triangle is a second right-angled triangle, and the first right-angled triangle and the second right-angled triangle are congruent with each other.
Further, one aspect of the present invention includes a tool body that is rotated around a central axis, a mounting seat that is formed at the tip of the tool body, and a cutting insert that is detachably mounted on the mounting seat. An indexable rotary cutting tool, characterized in that the cutting insert described above is used as the cutting insert.

In the above cutting insert, when the rake face is viewed from the front, a straight line passing through the tip of the bottom cutting edge in the central axis direction and extending along the radial direction is defined as a radial reference line. A tangent line to the bottom cutting edge at the outer end in the radial direction is a first tangent line, and a tangent line to the outer peripheral cutting edge at the tip of the outer peripheral cutting edge in the central axis direction is a second tangent line. The angle θ1 formed between the radial reference line is 10 to 30°, and the angle θ2 formed between the second tangent line and the radial reference line is (90°−θ1 )° is preferred.

According to the cutting insert and the indexable rotary cutting tool of the present invention, it is possible to carry out cutting so that the properties of the machined surface are uniform regardless of the machined part or shape of the work material. Therefore, in finishing machining, semi-finishing machining, etc., it is possible to obtain good machined surface accuracy over the entire machined surface.

1 is a perspective view showing an indexable rotary cutting tool according to a first embodiment of the present invention; FIG. Fig. 2 is a plan view of the indexable rotary cutting tool; Fig. 2 is a side view of the indexable rotary cutting tool; 1 is a front view of an indexable rotary cutting tool; FIG. Fig. 2 is a perspective view showing a cutting insert of a first reference example; It is (a) a top view, (b) a side view, and (c) a front view showing a cutting insert. It is (a) a top view, (b) a side view, and (c) a front view which expand and show the cutting edge part of a cutting insert. Fig. 2 is a plan view of the cutting insert of the first reference example, with the rake face viewed from the front; It is a top view of the cutting insert of a reference example which looked at the rake face from the front. It is a top view of the cutting insert of a reference example which looked at the rake face from the front. (a) A diagram showing the pick feed pitch and cusp height of the machined surface cut with the cutting insert (exchangeable rotary cutting tool) of the first reference example, (b) The pick feed of the machined surface cut with the conventional cutting tool FIG. 4 is a diagram showing pitch and cusp height; Fig. 10 is a perspective view showing an indexable rotary cutting tool according to a second embodiment of the present invention; FIG. 11 is a perspective view showing a cutting insert of a second reference example; It is (a) a top view, (b) a side view, and (c) a front view which expand and show the cutting edge part of a cutting insert. Fig. 10 is a perspective view showing a tip-exchangeable rotary cutting tool according to a third embodiment of the present invention; FIG. 11 is a perspective view showing a cutting insert of a third reference example; It is (a) a top view, (b) a side view, and (c) a front view which expand and show the cutting edge part of a cutting insert. 1 is a perspective view showing an indexable rotary cutting tool according to an embodiment of the present invention; FIG. It is a perspective view showing a cutting insert of an embodiment. It is (a) a top view, (b) a side view, and (c) a front view which expand and show the cutting edge part of a cutting insert. It is (a) a top view, (b) a side view, and (c) a front view which show the modification of the cutting insert of the 1st reference example of this invention.

<First reference example>
A cutting insert 5A according to a first embodiment of the present invention and an indexable rotary cutting tool 6A having the same will be described below with reference to FIGS. 1 to 11. FIG. In addition, in the drawings used for explaining the reference examples, in order to make it easier to understand the features of the present invention, there are cases in which the essential parts are enlarged, emphasized, or extracted.

The cutting insert 5A of this reference example includes a convex arc-shaped bottom cutting edge 11 called a so-called lens, a convex arc-shaped outer peripheral cutting edge 9 called a so-called barrel, and the bottom cutting edge 11 and the outer peripheral cutting edge 9. A composite cutting edge composed of a linear cutting edge 13 having a straight shape is provided. The indexable rotary cutting tool 6A equipped with the cutting insert 5A is used to perform various cutting processes including face milling (flat surface milling) and side milling (vertical wall milling) on a work material. In particular, excellent surface accuracy can be obtained in finishing or semi-finishing of the machined surface.

As shown in FIGS. 1 to 4, the indexable rotary cutting tool 6A includes a substantially cylindrical tool body 1 that is rotated around a central axis C, and a distal end portion 2 of the tool body 1 in the direction of the central axis C. A mounting seat 3 formed and a cutting insert 5</b>A detachably attached to the mounting seat 3 and having a cutting edge portion 4 are provided.

The indexable rotary cutting tool 6A of this reference example includes a tool body 1 made of steel or the like, and a cutting insert 5A made of cemented carbide harder than the tool body 1 or the like. A mounting seat (insert mounting seat) 3 formed at the distal end portion 2 of the tool body 1 has a plate-like cutting insert 5A which can be detached with its center axis aligned with the center axis C of the tool. be worn. The cutting insert 5</b>A attached to the mounting seat 3 is arranged such that the cutting edge portion 4 protrudes toward the tip side and radially outward of the tool body 1 .

The indexable rotary cutting tool 6A has a base end portion (shank portion) of the tool body 1 attached to a main shaft (not shown) of a machine tool, and rotates around the central axis C as the main shaft is driven to rotate. It is rotated in the tool rotation direction R. Then, the tool body 1 is fed together with the spindle in a direction intersecting the central axis C or in the direction of the central axis C, so that the cutting edge portion 4 of the cutting insert 5A cuts into a workpiece made of a metal material or the like. , Milling is applied. The indexable rotary cutting tool 6A of this reference example is more preferably used for a machine tool such as a 4- to 6-axis multi-axis control machining center.

In this reference example, the direction in which the central axis C of the tool body 1 extends, that is, the direction along the central axis C is referred to as the central axis C direction. Further, in the direction of the central axis C, the direction from the shank portion of the tool body 1 to the mounting seat 3 (downward in FIGS. 2 and 3) is called the front end side, and the direction from the mounting seat 3 to the shank portion (FIGS. 3) is referred to as the base end side.

A direction orthogonal to the central axis C is called a radial direction. Among the radial directions, the direction approaching the central axis C is called the radial inner side, and the direction away from the central axis C is called the radial outer side.
Also, the direction of rotation around the central axis C is called the circumferential direction. Among the circumferential directions, the direction in which the tool body 1 is rotated by the rotation of the spindle during cutting is referred to as the tool rotation direction R, and the opposite rotation direction to this is the side opposite to the tool rotation direction R (i.e., the anti-tool rotation direction). ).

The above definition of the orientation (direction) is similarly applied to the cutting insert 5A in which the insert center axis is aligned with (coaxially arranged with) the center axis C of the indexable rotary cutting tool 6A. be. Therefore, in FIGS. 6 to 10 showing the cutting insert 5A, the center axis of the insert is denoted by the same symbol C as the center axis C. As shown in FIG.

1 to 4, the mounting seat 3 includes a slit-shaped insert fitting groove 7 formed in the tip portion 2 of the tool body 1 and extending in the radial direction including the center axis C of the tool, and an insert fitting A fixing screw 8 for fixing the cutting insert 5A inserted into the groove 7 is provided.

The insert fitting groove 7 opens at the tip end surface of the tool body 1 , extends in the radial direction of the tool body 1 , and also opens on the outer peripheral surface of the tool body 1 . The insert fitting groove 7 has a slit shape formed with a predetermined length (depth) from the distal end surface of the tool body 1 toward the proximal end side.

By forming the slit-shaped insert fitting groove 7 in the tip portion 2 of the tool body 1, the tip portion 2 of the tool body 1 is divided into two to form a pair of tip half portions (half-split pieces). It is Further, an insert fixing screw hole is formed in the tip portion 2 so as to cross the insert fitting groove 7 from one surface portion of the tip half portion and reach the other tip half portion. The screw hole center axis of the insert fixing screw hole extends in the radial direction at the distal end portion 2 . , extending in orthogonal directions.

Among the insert fixing screw holes, the inner diameter of the hole portion formed in one tip half portion is larger than the inner diameter of the hole portion formed in the other tip half portion. In addition, a female threaded portion that engages with the male threaded portion of the fixing screw 8 is formed on the inner peripheral surface of the hole portion formed in the other tip half portion. Of the insert fixing screw holes, the hole portions formed in at least one of the tip half portions are through holes. In this reference example, each hole portion of one tip half portion and the other tip half portion is a through hole.

As shown in FIGS. 5 to 8, the cutting insert 5A includes a plate-shaped insert body 15, a cutting edge portion 4 formed in the insert body 15, and a cutting edge portion 4 formed in the insert body 15. The insert body 15 is formed to have a thickness. and a screw insertion hole 18 penetrating in the vertical direction.
5 A of cutting inserts of this reference example are formed in the front-back inversion symmetry (180-degree rotational symmetry) by making the central axis C into an axis of symmetry.

The insert body 15 has a substantially flat plate shape. A pair of plane portions 16 and 17 are formed on the front and back surfaces of the insert body 15 facing the thickness direction. The screw insertion hole 18 is a through hole that passes through the insert body 15 in the thickness direction and is opened to the one flat portion 16 and the other flat portion 17 . The fixing screw 8 is inserted through the screw insertion hole 18 when the cutting insert 5</b>A is attached to the mounting seat 3 and fixed. The arrangement of the screw insertion holes 18 in the insert body 15 will be separately described later.

The cutting edge portion 4 is arranged at the tip portion of the insert body 15 in the central axis C direction and the outer end portion in the radial direction. The cutting edge portion 4 has a rake face 19 facing the tool rotation direction R, a flank face that intersects the rake face 19 and faces at least one of the tip side and the radially outer side, and an intersection ridge line between the rake face 19 and the flank face. a cutting edge formed in the
The cutting edges include a peripheral cutting edge 9 , a bottom cutting edge 11 and a straight cutting edge 13 . The cutting edge is provided with an outer peripheral cutting edge 9, a bottom cutting edge 11, and a straight cutting edge 13, and thus has a substantially L-shape as a whole. In addition, the rake face portions (10, 12, 14) of the rake face 19 and the flank face portions of the flank face are respectively adjacent to the cutting edges (9, 11, 13).

The cutting insert 5A of this reference example is a two-flute cutting insert, and the set of cutting edges provided with the peripheral cutting edge 9, the bottom cutting edge 11 and the straight cutting edge 13 is arranged around the central axis C by 180 ° There are two sets of rotational symmetry.

As shown in FIG. 7A, the bottom cutting edge 11 is arranged at the tip of the insert body 15 in the direction of the central axis C, extends along the radial direction, and extends toward the tip in the direction of the central axis C. It has a convex arc shape.
The bottom cutting edge 11 is inclined toward the tip side in the central axis C direction as it goes radially inward from the radial outer end (connection point) A of the bottom cutting edge 11 connected to the straight cutting edge 13. extended. The amount of displacement of the bottom cutting edge 11 in the direction of the central axis C per unit length along the radial direction (that is, the inclination with respect to the radial direction) is radially inward from the radial outer end A of the bottom cutting edge 11 It gradually becomes smaller as it goes, and becomes zero at the inner end in the radial direction.

Of the total length of the cutting edge of the cutting edge portion 4, the radially inner end of the bottom cutting edge 11 is located at the forefront in the central axis C direction. In this reference example, the radially inner end of the bottom cutting edge 11 is arranged on the central axis C. As shown in FIG. A tangent line (radial reference line described later) RR at the radially inner end (most tip in the central axis C direction) of the bottom cutting edge 11 extends parallel to a plane perpendicular to the central axis C (horizontal plane).

When the cutting insert 5A is attached to the mounting seat 3 (insert fitting groove 7) of the tool body 1 and the indexable rotary cutting tool 6A is rotated around the central axis C, the rotational trajectory of the bottom cutting edge 11 changes to the tip It forms a convex lens shape that bulges out toward the side.

In this reference example, as shown in FIG. 7B, the axial rake angle (axial rake) of the bottom cutting edge 11 is 0°. However, it is not limited to this, and the rake angle in the axial direction of the bottom cutting edge 11 may be a positive value (positive angle) or a negative value (negative angle). Moreover, as shown in FIGS. 6(c) and 7(c), the radial rake angle of the bottom cutting edge 11 is 0°.

As shown in FIG. 7( a ), of the rake face 19 facing the tool rotation direction R of the cutting edge portion 4 , the portion adjacent to the base end side of the central axis C direction of the bottom cutting edge 11 is the bottom cutting edge 11 is the rake face portion 12 . In this reference example, the rake face portion 12 of the bottom cutting edge 11 is planar.
In addition, of the front end surface of the insert body 15 facing the front end side in the central axis C direction, the portion adjacent to the bottom cutting edge 11 on the side opposite to the tool rotation direction R is the flank portion of the bottom cutting edge 11 . A flank portion of the bottom cutting edge 11 has a curved surface that is convex toward the tip side. The flank portion of the bottom cutting edge 11 is inclined toward the base end side in the direction of the central axis C as it goes from the bottom cutting edge 11 toward the side opposite to the tool rotation direction R. has a clearance angle.

As shown in FIG. 7( a ), the outer peripheral cutting edge 9 is arranged at the radially outer end of the insert body 15 , extends along the direction of the central axis C, and protrudes radially outward. It has an arc shape that becomes
The outer peripheral cutting edge 9 extends diagonally outward in the radial direction from the tip (connection point) B in the direction of the central axis C of the outer peripheral cutting edge 9 connected to the straight cutting edge 13 toward the base end side. . The amount of displacement in the radial direction per unit length along the direction of the central axis C of the peripheral cutting edge 9 (that is, the inclination with respect to the direction of the central axis C) is based on the tip B of the peripheral cutting edge 9 in the direction of the central axis C. It gradually decreases toward the end side, and becomes zero at the base end in the central axis C direction.

Of the total cutting edge length of the cutting edge portion 4, the proximal end of the outer peripheral cutting edge 9 in the direction of the central axis C is positioned at the outermost end in the radial direction. A tangent line (a central axis direction reference line to be described later) CR at the base end (outermost end in the radial direction) of the peripheral cutting edge 9 in the direction of the central axis C is parallel to a plane (vertical plane) parallel to the central axis C. Extend.

When the cutting insert 5A is attached to the mounting seat 3 of the tool body 1 and the indexable rotary cutting tool 6A is rotated around the central axis C, the rotational locus of the outer peripheral cutting edge 9 expands radially outward. It has a barrel shape (barrel shape).

In this reference example, as shown in FIG. 7B, the axial rake angle (corresponding to the helix angle) of the outer peripheral cutting edge 9 is 0°. However, it is not limited to this, and the rake angle in the axial direction of the peripheral cutting edge 9 may be a positive value or a negative value. The radial rake angle (central direction rake angle; radial rake) of the outer peripheral cutting edge 9 is set at 0°. However, it is not limited to this, and the radial rake angle of the peripheral cutting edge 9 may be a positive value or a negative value.

As shown in FIG. 7A, of the rake face 19 of the cutting edge portion 4 facing the tool rotation direction R, the portion adjacent to the radially inner side of the outer peripheral cutting edge 9 is the rake face portion of the outer peripheral cutting edge 9. 10. In this reference example, the rake face portion 10 of the outer peripheral cutting edge 9 is planar.
In addition, of the outer peripheral surface facing radially outward in the insert body 15 , the portion adjacent to the outer peripheral cutting edge 9 on the side opposite to the tool rotation direction R is the flank portion of the outer peripheral cutting edge 9 . A flank portion of the outer peripheral cutting edge 9 has a curved surface that protrudes radially outward. The flank portion of the peripheral cutting edge 9 is inclined radially inward from the peripheral cutting edge 9 toward the side opposite to the tool rotation direction R, thereby providing the peripheral cutting edge 9 with a clearance angle. It is

As shown in FIG. 7(a), the straight cutting edge 13 has a straight shape. The straight cutting edge 13 connects the radial outer end A of the bottom cutting edge 11 and the tip B of the outer peripheral cutting edge 9 in the central axis C direction. That is, the radial outer end A of the bottom cutting edge 11 and the tip B of the outer peripheral cutting edge 9 in the central axis C direction are connected via the straight cutting edge 13 . In this reference example, the radial outer end A of the bottom cutting edge 11 and the tip B of the outer peripheral cutting edge 9 in the central axis C direction are connected via one straight cutting edge 13 .

The straight cutting edge 13 is inclined toward the base end side in the direction of the central axis C as it goes radially outward from the radial inner end (connection point A) of the straight cutting edge 13 connected to the bottom cutting edge 11. and extended. The straight cutting edge 13 extends from the base end (connection point B) in the direction of the central axis C of the straight cutting edge 13 connected to the outer peripheral cutting edge 9 while being inclined inward in the radial direction as it goes to the tip side. .

When the cutting insert 5A is attached to the mounting seat 3 of the tool body 1 and the indexable rotary cutting tool 6A is rotated around the central axis C, the rotational locus of the linear cutting edge 13 moves toward the tip side in the direction of the central axis C. It is formed in a tapered tubular shape whose diameter gradually decreases as it goes.

In this reference example, as shown in FIG. 7B, the rake angle in the axial direction of the straight cutting edge 13 is 0°. Therefore, the rake angle in the axial direction of the straight cutting edge 13 at the connecting point A between the straight cutting edge 13 and the bottom cutting edge 11 is 0°. Further, the rake angle in the axial direction of the straight cutting edge 13 at the connecting point B between the straight cutting edge 13 and the peripheral cutting edge 9 is 0°. However, it is not limited to this, and the rake angle in the axial direction of the straight cutting edge 13 may be a positive value or a negative value. As shown in FIGS. 6(c) and 7(c), the radial rake angle of the straight cutting edge 13 is 0°. However, it is not limited to this, and the radial direction rake angle of the straight cutting edge 13 may be a positive value or a negative value.

As shown in FIG. 7( a ), of the rake face 19 of the cutting edge portion 4 facing the tool rotation direction R, the portion adjacent to the radially inner side and the proximal side of the straight cutting edge 13 is the straight cutting edge 13 is the rake face portion 14 of the . In this reference example, the rake face portion 14 of the straight cutting edge 13 is planar.
A portion of the outer surface of the insert body 15 adjacent to the straight cutting edge 13 on the side opposite to the tool rotation direction R is a flank portion of the straight cutting edge 13 . A flank portion of the straight cutting edge 13 is formed in a planar shape facing the front end side in the direction of the central axis C and radially outward. The flank portion of the straight cutting edge 13 is inclined toward the base end side in the direction of the central axis C and radially inward from the straight cutting edge 13 toward the side opposite to the tool rotation direction R. A relief angle is provided to the straight cutting edge 13 .

In the cutting edge portion 4, the radius of curvature of the bottom cutting edge 11 and the radius of curvature of the outer peripheral cutting edge 9 are the same. In this reference example, the curvature radius of the bottom cutting edge 11 and the curvature radius of the outer peripheral cutting edge 9 are the outer diameter of the rotation locus obtained by rotating the outer peripheral cutting edge 9 around the central axis C (the maximum diameter of the cutting edge portion 4 and is equal to the blade diameter).

In this reference example, of the rake face 19, the rake face portion 12 of the bottom cutting edge 11, the rake face portion 10 of the outer peripheral cutting edge 9, and the rake face portion 14 of the straight cutting edge 13 are formed on the same plane. there is That is, the entire rake face 19 of the cutting edge of the cutting edge portion 4 is formed by one plane.

7(a) and 8, when the rake face 19 is viewed from the front, it intersects with the central axis C at an angle α of 45°, and the central axis C The bottom cutting edge 11 and the outer peripheral cutting edge 9 are formed so as to be line-symmetrical with each other with the imaginary straight line VL extending toward the tip side of the direction as the axis of symmetry. Further, the straight cutting edge 13 is orthogonal to the virtual straight line VL.
Specifically, in this reference example, when the rake face 19 is viewed from the front, the entire blade length of the cutting edge of the cutting edge portion 4 is formed in a line-symmetrical shape with the imaginary straight line VL as the axis of symmetry.

In this reference example, since the rake face portion 12 of the bottom cutting edge 11, the rake face portion 10 of the outer peripheral cutting edge 9, and the rake face portion 14 of the straight cutting edge 13 are formed on the same plane, The above "looking at the rake face 19 from the front" means that the rake face portion 12 of the bottom cutting edge 11 is seen from the front, the rake face portion 10 of the outer peripheral cutting edge 9 is seen from the front, and the straight cutting edge 13 It is synonymous with viewing the rake face portion 14 from the front.
Also, the angle α refers to an acute angle out of acute angles and obtuse angles formed by the intersection of the imaginary straight line VL and the central axis C. As shown in FIG.

As shown in FIGS. 7A and 8, when the rake face 19 is viewed from the front, a straight line passing through the tip of the bottom cutting edge 11 in the direction of the center axis C and extending in the radial direction is defined as a radial reference line. RR, a straight line extending along the direction of the central axis C passing through the radially outer end of the outer peripheral cutting edge 9 is defined as the central axial direction reference line CR, and the bottom cutting edge 11 at the radially outer end A of the bottom cutting edge 11 The tangent line of is the first tangent line L1, the tangent line of the outer peripheral cutting edge 9 at the tip B in the direction of the central axis C of the outer peripheral cutting edge 9 is the second tangent line L2, and the first tangent line L1 and the radial reference line RR , an intersection point E between the first tangent line L1 and the central axial reference line CR, and an intersection point F between the radial reference line RR and the central axial reference line CR. With a triangle (ΔDEF) as a first right triangle T1, a point of intersection G between a second tangent line L2 and the central axial reference line CR, an intersection point H of the second tangent line L2 and the radial reference line RR, and a radial A right-angled triangle (ΔGHF) formed by connecting the intersection points F of the direction reference line RR and the center axis direction reference line CR with straight lines is defined as a second right-angled triangle T2, and the first right-angled triangle T1 and the second right-angled triangle T2 are formed. The right triangle T2 is congruent with each other.

In addition, in the front view of the rake face 19 shown in FIGS. 7A and 8, a line segment connecting the radial outer end A of the bottom cutting edge 11 and the tip B of the outer peripheral cutting edge 9 in the direction of the central axis C A virtual straight line passing through the midpoint M (the midpoint M of the straight cutting edge 13 in this reference example) and the intersection point F between the radial reference line RR and the central axial reference line CR coincides with the virtual straight line VL. do.
Further, the hole center of the screw insertion hole 18 is positioned on the imaginary straight line VL. Specifically, when the rake face 19 is viewed from the front, the hole center of the screw insertion hole 18 is arranged on the intersection point I between the imaginary straight line VL and the central axis C. As shown in FIG.

Further, when the rake face 19 is viewed from the front, the angle θ1 formed between the first tangent line L1 and the radial reference line RR is 10 to 30°, and the second tangent line L2 and the radial reference line The angle θ2 formed with RR is (90°−θ1)°. The angle θ1 is preferably 12-28°, more preferably 12-25°. However, the angles θ1 and θ2 are not limited to the numerical range of this reference example.
It should be noted that the angle θ1 indicates an acute angle out of an acute angle and an obtuse angle formed by the intersection of the first tangent line L1 and the radial reference line RR. Further, the angle θ2 indicates an acute angle out of acute angles and obtuse angles formed by the intersection of the second tangent line L2 and the radial reference line RR.

According to the cutting insert 5A and the indexable rotary cutting tool 6A of this reference example described above, the rake face 19 of the cutting edge 4 intersects the central axis C at an angle α of 45° when viewed from the front. The bottom cutting edge 11 and the outer peripheral cutting edge 9 are formed in a line-symmetrical shape with the imaginary straight line VL as an axis of symmetry.
Alternatively, when the rake face 19 of the cutting edge portion 4 is viewed from the front, the radius of curvature of the bottom cutting edge 11 and the radius of curvature of the outer peripheral cutting edge 9 are the same, and the radial outer end of the bottom cutting edge 11 A first right triangle T1 (ΔDEF) having a tangent (first tangent) L1 to the bottom cutting edge 11 at A, and a tangent to the outer peripheral cutting edge 9 at the tip B in the direction of the central axis C of the outer peripheral cutting edge 9 (Second tangent) A second right-angled triangle T2 (ΔGHF) having a hypotenuse L2 is congruent with each other.

Therefore, for example, when performing face cutting (surface machining) on a work material, the cutting marks (processing marks, processing marks) imparted to the machined surface of the work material by cutting with the bottom cutting edge 11, When the work material is subjected to side surface milling (upright wall processing), the cut marks imparted to the machined surface of the work material by cutting with the outer peripheral cutting edge 9 have the same properties as each other.
That is, in this reference example, the radius of curvature of the bottom cutting edge 11 and the radius of curvature of the outer peripheral cutting edge 9 are the same, and the bottom cutting edge 11 and the outer peripheral cutting edge 9 are formed line-symmetrically with each other. . Therefore, in order to make the cusp height of the flat portion and the cusp height of the vertical wall portion of the machined surface of the work material equal, both can be machined with the same pick feed (pitch). Eyes can be aligned with each other. Therefore, it is possible to obtain a machined surface having the same quality over the entire work material.
That is, in the case of cutting using either the bottom cutting edge 11 or the peripheral cutting edge 9, the properties of the machined surface of the work material can be made uniform.

Reference is now made to FIG. 11(a) where pitch and cusp height are shown. FIG. 11(a) is an enlarged cross-sectional view of the machined surface of the work material W. In the figure, P denotes the pitch of machining marks (pick feed ), and symbol CH represents the cusp height of the machining marks. According to this reference example, the pitch (width) P and the cusp height (depth) CH of the pick feed can be made uniform regardless of the machining site and shape of the work material W.

Further, since the properties of the machined surface of the work material can be uniformed as described above, the surface roughness, gloss, etc. of the machined surface can be made uniform over the entire machined surface. That is, the surface performance and appearance of the entire machined surface can be made uniform. As a result, in finishing and semi-finishing, an advantageous effect can be obtained in increasing the precision of machining.

Also, the range of the inclination angle of the machined surface that can be cut with the bottom cutting edge 11 in face milling (flat machining) and the inclination angle of the machined surface that can be cut with the peripheral cutting edge 9 in side milling (upright wall machining) Since the ranges are the same as each other, more machining shapes can be handled while the properties of the machining surface of the work material are kept constant.

When the cutting insert 5A and the indexable rotary cutting tool 6A of this reference example are used in a machine tool such as a multi-axis control machining center, the effects of this reference example are particularly remarkable. The above-mentioned multi-axis control refers to, for example, 4 to 6-axis control. Multi-axis control makes it easier to machine a plurality of machining surfaces with different inclinations to have more uniform properties. In this case, even a workpiece having a complicated three-dimensional curved surface, such as a turbine blade, can be cut with high precision and stability.

Specifically, when a conventional ball end mill is used in a three-axis control cutting method, there are problems as described in the above "Problems to be Solved by the Invention".
According to the cutting insert 5A and the indexable rotary cutting tool 6A of this reference example, it is possible to correspond to a processing machine with 5-axis control, and the outer peripheral cutting edge (barrel cutting edge) 9 and the bottom cutting edge (lens cutting edge) 11 By using them in combination, it is possible to achieve high-efficiency machining and high-precision machining at the same time.
For example, when using the peripheral cutting edge (barrel cutting edge) 9 by tilting the tool axis, the machining pitch is set large on the inclined surface of the work material to achieve high efficiency machining. It becomes possible to set conditions and obtain a high-quality finished surface.
Also, when the bottom cutting edge (lens cutting edge) 11 is used, similarly to the outer peripheral cutting edge (barrel cutting edge) 9, the curved surface of the work material can be finished with high quality.
Furthermore, even when used in a 3-axis control processing machine, by using the outer peripheral cutting edge (barrel cutting edge) 9, the inclined surface close to the vertical vertical wall or the bottom cutting edge (lens cutting edge) By using 11, it is possible to machine a curved surface of a work material that is close to a flat surface under the condition that the machining pitch is set large.

Here, with reference to FIGS. 8 to 10, this reference example will be described in more detail. FIG. 8 shows a cutting insert 5A of this reference example, and FIGS. 9 and 10 show cutting inserts 20 and 30 of other reference examples having different technical ideas from this reference example. 8 to 10 are plan views of the cutting inserts 5A, 20 and 30, respectively, with the rake face 19 of the cutting edge portion 4 viewed from the front. The three cutting inserts 5A, 20, 30 shown in FIGS. 8 to 10 all have the same radius of curvature of the bottom cutting edge 11 and the radius of curvature of the peripheral cutting edge 9. FIG.

In the cutting insert 5A of this reference example shown in FIG. It is formed so as to have a line-symmetrical shape. In addition, in the cutting insert 5A of this reference example shown in FIG. 8, the first right triangle T1 (ΔDEF) and the second right triangle T2 (ΔGHF) are congruent with each other. Thereby, there exists the outstanding effect mentioned above.

On the other hand, in the cutting inserts 20 and 30 of other reference examples shown in FIGS. 9 and 10, the radius of curvature of the bottom cutting edge 11 and the radius of curvature of the outer peripheral cutting edge 9 are the same, but The cutting edge 11 and the outer peripheral cutting edge 9 are not formed in a line-symmetrical shape. Moreover, in the cutting inserts 20 and 30 of the reference examples shown in FIGS. 9 and 10, the first right triangle T1 (ΔDEF) and the second right triangle T2 (ΔGHF) are not congruent with each other.
Therefore, in the cutting inserts 20 and 30 of other reference examples shown in FIGS. In some cases, it is difficult to make the same properties as the saw marks imparted to the machined surface by performing side surface machining (upright wall machining). In other words, simply setting the radius of curvature of the bottom cutting edge 11 and the radius of curvature of the outer peripheral cutting edge 9 to be the same does not always provide the excellent effects of this reference example described above.

Moreover, according to this reference example, the machining time can be shortened as compared with conventional cutting tools such as ball end mills and radius end mills.
Specifically, in conventional ball end mill type cutting tools, the locus of rotation around the central axis of the cutting edge is hemispherical, and the radius of this locus of rotation is the tool diameter (the maximum diameter of the locus of rotation of the cutting edge). , blade diameter). In the ball end mill type cutting tool, the curvature radius of the cutting edge portion corresponding to the bottom cutting edge and the curvature radius of the cutting edge portion corresponding to the outer cutting edge are both 1/2 of the tool diameter. In other words, with the ball end mill type cutting tool, the pick feed is set so that the cusp height is equal to or less than a predetermined cusp height value according to the tool radius (1/2 of the tool diameter), and cutting is performed. In addition, in the case of a radius end mill type cutting tool, a corner R cutting edge is used when cutting an inclined machined surface, etc., but the curvature radius of the corner R cutting edge is generally the same as that of the cutting edge of a ball end mill. Because it is smaller than the radius of curvature (for the same tool diameter), the pick feed is even smaller than a ball end mill.

On the other hand, in this reference example, the radius of curvature of the bottom cutting edge 11 and the radius of curvature of the outer peripheral cutting edge 9 can each be set larger than 1/2 of the tool diameter. For this reason, in order to obtain a cusp height equivalent to the cusp height of the machined surface machined with a conventional ball end mill (that is, in order to reduce the cusp height to a predetermined value or less), according to this reference example, the pick feed (pitch) is set large. can do.
In this reference example, the radius of curvature of the bottom cutting edge 11 and the radius of curvature of the outer peripheral cutting edge 9 are made equal to the tool diameter (maximum diameter of the rotational locus of the cutting edge). Therefore, in this reference example, the pick feed can be set to a value nearly twice that of the conventional ball end mill.

Here, with reference to FIGS. 11A and 11B, the difference in pick feed (pitch) between this reference example and the conventional example will be described. FIG. 11(a) shows a cross section of the machined surface (machined trace) of the work material W cut by the cutting insert 5A (exchangeable rotary cutting tool 6A) of this reference example, and FIG. , a cross-section of a machined surface of a work W cut by a conventional cutting tool. In the figure, P is the pick feed pitch, and CH is the cusp height. As shown in FIGS. 11A and 11B, when the cusp heights CH are set to be the same, the pick feed pitch P can be increased in this reference example shown in FIG. 11A. can.

Thus, according to this reference example, the pick feed (pitch P) can be set large while keeping the cusp height CH small. As a result, the number of irregularities (scallops) imparted to the machined surface as machining traces can be reduced, and the machined surface accuracy can be improved. In addition, the length of the tool path (total machining length) can be reduced by increasing the pick feed, and the machining time can be shortened.

Using an indexable rotary cutting tool 6A equipped with a cutting insert 5A of this reference example and a ball end mill of a conventional example, a cutting test of a work material (S50C) was actually performed. It was confirmed that when the speed, feed amount and cusp height (scallop height) are set to be the same, the machining time can be reduced by about 30% in this reference example compared to the conventional example. Moreover, both the arithmetic mean roughness Ra and the ten-point mean roughness Rz of the machined surface of this reference example are smaller than those of the conventional example, indicating that the machined surface accuracy is excellent.

Further, a straight cutting edge 13 connecting the bottom cutting edge 11 and the outer peripheral cutting edge 9 is provided. Therefore, using the straight cutting edge 13, it is possible to perform surface milling (finishing) of a work material, which is difficult to perform with a conventional ball end mill or the like. In addition, plane milling can be performed efficiently. That is, the straight cutting edge 13 has a function as a finishing edge for eliminating sawing (processing marks, processing marks). Therefore, according to this reference example, it is possible to cope with various cutting processes.

As described above, according to this reference example, it is possible to carry out cutting work so that the properties of the machined surface are uniform regardless of the machined part or shape of the work material. Therefore, in finishing machining, semi-finishing machining, etc., it is possible to obtain good machined surface accuracy over the entire machined surface.

In this reference example, the insert body 15 is formed with a screw insertion hole 18 that penetrates the insert body 15 in the thickness direction. A fixing screw 8 for fixing the cutting insert 5A is inserted into the matching groove 7).
According to this reference example, since the hole center of the screw insertion hole 18 is positioned on the imaginary straight line VL, even during cutting using the bottom cutting edge 11, cutting using the outer peripheral cutting edge 9 Also in this case, the force that tends to rotate the cutting insert 5A around the screw insertion hole 18 (fixing screw 8) is suppressed.

Specifically, during cutting using the bottom cutting edge 11 , the cutting edge normal direction component of the cutting resistance received by the bottom cutting edge 11 acts toward the hole center of the screw insertion hole 18 . During cutting using the peripheral cutting edge 9 , the cutting edge normal direction component of the cutting resistance received by the peripheral cutting edge 9 acts toward the hole center of the screw insertion hole 18 . Therefore, the force that tends to rotate the cutting insert 5A fixed by the fixing screw 8 around the fixing screw 8 is alleviated, and the minute vibration (rotational minute vibration) of the cutting insert 5A with respect to the mounting seat 3 is reduced. Suppressed.

As a result, the properties of the machined surface of the work material are stabilized, and high-precision machining can be achieved.
In particular, it is advantageous for high precision in finishing and semi-finishing by so-called surface-along machining, in which a three-dimensional component of a work material is milled with a tool locus along the outer surface of the component. effect can be obtained.
Further, during cutting using the straight cutting edge 13 , the cutting edge normal direction component of the cutting resistance received by the straight cutting edge 13 acts toward the hole center of the screw insertion hole 18 . Therefore, even during cutting using the straight cutting edge 13, the same effect as described above can be obtained.

In this reference example, the radial outer end A of the bottom cutting edge 11 and the tip B of the outer peripheral cutting edge 9 in the central axis C direction are connected via one straight cutting edge 13 . Therefore, the length of the straight cutting edge 13 can be ensured long, and the feed amount can be increased when the straight cutting edge 13 is used for cutting, so that the machining efficiency can be enhanced.

In this reference example, of the rake face 19 of the cutting edge portion 4, the rake face portion 12 of the bottom cutting edge 11, the rake face portion 10 of the outer peripheral cutting edge 9, and the rake face portion 14 of the straight cutting edge 13 are flush with each other. formed on top. Therefore, the rake angle in the axial direction and the rake angle in the radial direction do not substantially change over the entire length of the cutting edge.
In general, among the rake faces of the cutting edge portion, the rake face portion of the bottom cutting edge, the rake face portion of the outer peripheral cutting edge, and the like are formed of flat surfaces and curved surfaces that are different from each other. Since the connection point between the cutting edges is a portion where two cutting edges having different shapes are connected, the rake angle in the axial direction and the rake angle in the radial direction change. Therefore, during cutting, the cutting load tends to increase in the vicinity of the connection point between the cutting edges.

Therefore, as in this reference example, if the rake face portion 12 of the bottom cutting edge 11, the rake face portion 10 of the outer peripheral cutting edge 9, and the rake face portion 14 of the straight cutting edge 13 are formed on the same plane, At the connection point A between the bottom cutting edge 11 and the straight cutting edge 13, and the connection point B between the outer peripheral cutting edge 9 and the straight cutting edge 13, the rake faces of the cutting edges are formed by one plane. .
As a result, large changes in the rake angle in the axial direction and the rake angle in the radial direction are suppressed on both sides of the cutting edge sandwiching connection points A and B, and a large cutting load acts on the vicinity of connection points A and B. can be prevented. Therefore, the cutting edge strength at the connecting portion between the straight cutting edge 13 and the bottom cutting edge 11 and the connecting portion between the straight cutting edge 13 and the outer peripheral cutting edge 9 is remarkably increased, and the tool life is extended.

In addition, since the rake face portion 12 of the bottom cutting edge 11, the rake face portion 10 of the outer peripheral cutting edge 9, and the rake face portion 14 of the straight cutting edge 13 are formed on the same plane, the cutting insert 5A can be easily manufactured. is. In addition, since no recesses (troughs) or the like are formed between the rake face portions 10, 12, and 14 (connection portions), catching of chips during cutting is suppressed, and chip discharge is enhanced. be done.

In this reference example, when the rake face 19 is viewed from the front, the angle θ1 formed between the first tangent line L1 and the radial reference line RR is 10 to 30°. Since the angle θ2 formed with the direction reference line RR is (90°−θ1)°, the above-described effects are more remarkable. In addition, while ensuring the strength of the cutting edge in the vicinity of the straight cutting edge 13, it becomes easier to cope with various workpieces to be machined and their shapes.

Specifically, since the angle θ1 is 10° or more (the angle θ2 is 80° or less), it is possible to prevent the length of the linear cutting edge 13 from becoming too long. As a result, the length of each edge of the bottom cutting edge 11 and the outer peripheral cutting edge 9 is ensured to be long, and the effects of the present reference example described above (the effect of increasing the pick feed pitch P while keeping the cusp height CH small) can be further enhanced. You can make it special. When the angle θ1 is less than 10° (when the angle θ2 exceeds 80°), the cutting edge length of the straight cutting edge 13 becomes too long, and as a result, the cutting edge lengths of the bottom cutting edge 11 and the peripheral cutting edge 9 become short. , it may become difficult to obtain the above effects. In addition, in order to make the above-described effect more remarkable, it is preferable that the angle θ1 is 12° or more (the angle θ2 is 78° or less).
Moreover, since the angle θ1 is 30° or less (angle θ2 is 60° or more), it is possible to prevent the length of the linear cutting edge 13 from becoming too short. As a result, the blade length of the straight cutting edge 13 can be ensured to be long, and the effects of the present reference example described above (such as the effect of performing surface milling with high precision and efficiency using the straight cutting edge 13) can be made more exceptional. . When the angle θ1 exceeds 30° (when the angle θ2 is less than 60°), the length of the linear cutting edge 13 becomes too short, which may make it difficult to obtain the above effects. In order to make the above effects more remarkable, the angle θ1 is preferably 28° or less (angle θ2 is 62° or more), and is preferably 25° or less (angle θ2 is 65° or more). is more desirable.

<Second reference example>
Next, a cutting insert 5B according to a second embodiment of the present invention and an indexable rotary cutting tool 6B having the same will be described with reference to FIGS. 12 to 14. FIG.
In the second reference example, the same components as those in the first reference example are denoted by the same reference numerals, and descriptions thereof are omitted, and different points are mainly described.

As shown in FIGS. 12 to 14, the cutting insert 5B and the indexable rotary cutting tool 6B of this reference example have the straight cutting edge 13 and the rake face portion 14 provided in the cutting edge portion 4. etc. are different.
In this reference example, the radial outer end (connection point) A of the bottom cutting edge 11 and the tip (connection point) B of the outer peripheral cutting edge 9 in the central axis C direction are connected via a plurality of straight cutting edges 13. do. Specifically, as shown in FIGS. 14A to 14C, the radial outer end A of the bottom cutting edge 11 and the tip B of the outer peripheral cutting edge 9 in the direction of the central axis C are divided into two. They are connected via a straight cutting edge 13 .

As shown in FIG. 14( a ), the plurality of straight cutting edges 13 extend in different directions between connection points A and B and are formed continuously with each other.
Among the plurality of straight cutting edges 13, the straight cutting edge (first straight cutting edge) 13 connected to the bottom cutting edge 11 moves radially outward from the connection point A toward the base end in the direction of the central axis C. It extends at an angle towards Among the plurality of straight cutting edges 13, the straight cutting edge (second straight cutting edge) 13 connected to the outer peripheral cutting edge 9 extends diagonally inward in the radial direction from the connection point B toward the tip side. there is

The amount of displacement in the direction of the central axis C per unit length in the radial direction of the first straight cutting edge 13 (that is, the inclination with respect to the radial direction) is the radial outer end A of the bottom cutting edge 11 and the outer peripheral cutting edge 9 is smaller than the amount of displacement of the line segment LS connecting the tip B in the direction of the central axis C of , and larger than the amount of displacement of the first tangent line L1.
The amount of displacement in the direction of the central axis C per unit length in the radial direction of the second straight cutting edge 13 is larger than the amount of displacement of the line segment LS and smaller than the amount of displacement of the second tangent line L2. .
The amount of displacement of the first straight cutting edge 13 in the direction of the central axis C per unit length in the radial direction is smaller than the amount of displacement of the second straight cutting edge 13 .

In this reference example, the plurality of straight cutting edges 13 (the first straight cutting edge 13 and the second straight cutting edge 13) are arranged closer to the outer periphery of the tip of the tool than the line segment LS. When the rake face 19 is viewed from the front, the corners where the adjacent straight cutting edges 13 are connected are formed to form an obtuse angle convex toward the outer periphery of the tip of the tool. In addition, the virtual straight line VL passes through the intersection point F between the radial reference line RR and the central axial reference line CR, and the midpoint M of the line segment LS.

A connection point (the above-mentioned corner portion) between the first straight cutting edge 13 and the second straight cutting edge 13 is arranged on the virtual straight line VL. A connection point between the first straight cutting edge 13 and the second straight cutting edge 13 is arranged on the tip outer peripheral side of the tool from the midpoint M of the line segment LS. The 1st linear cutting edge 13 and the 2nd linear cutting edge 13 are formed so that it may become line symmetrical shape mutually by making the virtual straight line VL into a symmetry axis. That is, in this reference example, the blade length of the first straight cutting edge 13 and the blade length of the second straight cutting edge 13 are the same.

In addition, of the rake face 19 of the cutting edge portion 4, the rake face portion 12 of the bottom cutting edge 11, the rake face portion 10 of the outer peripheral cutting edge 9, and the rake face portions 14 of the plurality of straight cutting edges 13 are They are formed on the same plane. 12 and 13, the flank portions of the plurality of straight cutting edges 13 are formed on planes different from each other.

According to the cutting insert 5B and the indexable rotary cutting tool 6B of this reference example described above, the same effects as those of the reference example described above can be obtained.
In addition, in this reference example, a plurality of straight cutting edges 13 can be used for various finishing processes.

In this reference example, since the blade length of the first straight cutting edge 13 and the blade length of the second straight cutting edge 13 are the same as each other, finishing using the first straight cutting edge 13 , and finish machining using the second straight cutting edge 13 can align the sawing lines (processing marks, processing marks). Therefore, the cut marks imparted to the machined surface of the work material by cutting separately with the plurality of straight cutting edges 13 have the same properties.

<Third reference example>
Next, a cutting insert 5C according to a third embodiment of the present invention and an indexable rotary cutting tool 6C having the same will be described with reference to FIGS. 15 to 17. FIG.
In the third reference example, the same reference numerals are assigned to the same components as those in the first and second reference examples, and the description thereof is omitted, and mainly the different points will be described.

As shown in FIGS. 15 to 17, the cutting insert 5C and the indexable rotary cutting tool 6C of this reference example are different from the above-described reference example in that the straight cutting edge 13 and the rake face portion 14 provided in the cutting edge portion 4 etc. are different.
In this reference example, as shown in FIGS. 17A to 17C, the radial outer end (connection point) A of the bottom cutting edge 11 and the tip (connection point) of the outer peripheral cutting edge 9 in the direction of the central axis C Point) B is connected via three straight cutting edges 13 .

As shown in FIG. 17( a ), the plurality of straight cutting edges 13 include a straight cutting edge (first straight cutting edge) 13 connected to the bottom cutting edge 11 and a straight cutting edge (first straight cutting edge) 13 connected to the outer peripheral cutting edge 9 . A blade (second straight cutting edge) 13 and a straight cutting edge (third straight cutting edge) 13 that is positioned between and connects the first straight cutting edge 13 and the second straight cutting edge 13. and are included. The third straight cutting edge 13 extends obliquely toward the base end side in the direction of the central axis C as it extends radially outward from the connection point with the first straight cutting edge 13 .

The amount of displacement in the direction of the central axis C per unit length in the radial direction of the third straight cutting edge 13 (that is, the inclination with respect to the radial direction) is greater than the amount of displacement of the first straight cutting edge 13, It is smaller than the displacement amount of the linear cutting edge 13 of No. 2. In this reference example, the displacement amount of the third straight cutting edge 13 and the displacement amount of the line segment LS are the same as each other. That is, the third straight cutting edge 13 and the line segment LS are parallel to each other.

In this reference example, the plurality of straight cutting edges 13 (first to third straight cutting edges 13) are arranged closer to the outer peripheral side of the tip of the tool than the line segment LS. When the rake face 19 is viewed from the front, the corners where the adjacent straight cutting edges 13 are connected are formed to form an obtuse angle convex toward the outer periphery of the tip of the tool.

The connection point (corner) between the first straight cutting edge 13 and the third straight cutting edge 13, and the connection point (corner) between the second straight cutting edge 13 and the third straight cutting edge 13 are , are arranged on the outer peripheral side of the tip of the tool from the line segment LS. Moreover, the 3rd linear cutting edge 13 orthogonally crosses the imaginary straight line VL. The 1st linear cutting edge 13 and the 2nd linear cutting edge 13 are formed so that it may become line symmetrical shape mutually by making the virtual straight line VL into a symmetry axis. In this reference example, the blade length of the first straight cutting edge 13, the blade length of the second straight cutting edge 13, and the blade length of the third straight cutting edge 13 are the same.

According to the cutting insert 5C and the indexable rotary cutting tool 6C of this reference example described above, the same effects as those of the reference example described above can be obtained.
In this reference example, since the blade length of the first straight cutting edge 13, the blade length of the second straight cutting edge 13, and the blade length of the third straight cutting edge 13 are the same, the first Finishing using the straight cutting edge 13, finishing using the second straight cutting edge 13, and finishing using the third straight cutting edge 13. can be aligned.

The blade length of the third straight cutting edge 13 may be different from the blade lengths of the first and second straight cutting edges 13 . That is, the blade length of the third straight cutting edge 13 may be longer or shorter than the blade lengths of the first and second straight cutting edges 13 . In this case, it becomes possible to deal with more diverse processing forms.

<Embodiment>
Next, a cutting insert 5D according to an embodiment of the present invention and an indexable rotary cutting tool 6D having the same will be described with reference to FIGS. 18 to 20. FIG.
In this embodiment, the same reference numerals are assigned to the same components as those in the first to third reference examples, and the description thereof will be omitted, and mainly the different points will be described.

As shown in FIGS. 18 to 20, the cutting insert 5D and the indexable rotary cutting tool 6D of the present embodiment are such that the cutting edge portion 4 does not include the straight cutting edge 13 and the rake face portion 14. The configuration is different from the aforementioned reference example.

As shown in FIGS. 20(a) to (c), in the present embodiment, the radial outer end (connection point) A of the bottom cutting edge 11 and the tip (connection point) of the outer peripheral cutting edge 9 in the direction of the central axis C point) B is directly connected. The radial outer end A of the bottom cutting edge 11 and the tip B of the outer peripheral cutting edge 9 in the central axis C direction are directly connected to each other. A connection point A of the bottom cutting edge 11 is an end point where the bottom cutting edge 11 is connected to the outer peripheral cutting edge 9, and a connection point B of the outer peripheral cutting edge 9 is connected to the bottom cutting edge 11 at the outer peripheral cutting edge 9. It is the end point. The positions of the connection point A and the connection point B coincide with each other. Between the connection point A and the connection point B, no straight cutting edge 13 is formed. Therefore, the rake face 19 of the cutting edge portion 4 does not have the rake face portion 14 of the straight cutting edge 13 . Of the rake face 19, the rake face portion 12 of the bottom cutting edge 11 and the rake face portion 10 of the outer peripheral cutting edge 9 are formed on the same plane.

As shown in FIGS. 18 to 20(a), the corner where the radial outer end A of the bottom cutting edge 11 and the tip B of the outer peripheral cutting edge 9 in the direction of the central axis C are connected is the tip of the tool. It is formed so as to form an obtuse angle that becomes convex toward the outer peripheral side.
In this embodiment, the hole center of the screw insertion hole 18 is the connection point A, B between the radial outer end A of the bottom cutting edge 11 and the tip B of the outer peripheral cutting edge 9 in the central axis C direction, and the radial reference It is positioned on an imaginary straight line VL passing through the intersection F between the line RR and the central axis direction reference line CR.

Further, as shown in FIG. 20(a), when the rake face 19 is viewed from the front, the angle θ1 formed between the first tangent line L1 and the radial reference line RR is 10 to 30°, The angle θ2 formed between the second tangent line L2 and the radial reference line RR is (90°−θ1)°.

According to the cutting insert 5D and the indexable rotary cutting tool 6D of this embodiment described above, it is possible to obtain the same effects as those of the reference example described above.
In this embodiment, since the radial outer end A of the bottom cutting edge 11 and the tip B of the outer peripheral cutting edge 9 in the central axis C direction are directly connected, the length of the bottom cutting edge 11 and the outer peripheral edge It becomes possible to set the blade length of the cutting edge 9 long (maximum). Therefore, the pick feed pitch P can be increased while keeping the cusp height CH small. Therefore, it is possible to improve the machining efficiency while maintaining good machined surface accuracy. Moreover, since the straight cutting edge 13, the rake face portion 14 and the flank face portion of the straight cutting edge 13 are not formed, the manufacturing of the cutting insert 5D can be simplified.

Further, in the present embodiment, since the angle θ1 is 10° or more (angle θ2 is 80° or less), connection points A and B (corners) between the bottom cutting edge 11 and the outer peripheral cutting edge 9 are located on the tip outer peripheral side of the tool. It can be suppressed that it is too sharp toward. Therefore, chipping of the cutting edge in the vicinity of the connection points A and B is suppressed. In order to make the above effects more remarkable, it is preferable that the angle θ1 is 12° or more (the angle θ2 is 78° or less).
In addition, since the angle θ1 is 30° or less (angle θ2 is 60° or more), the cutting edge shape of the cutting edge portion 4 as a whole is prevented from coming close to the cutting edge shape of a ball end mill. That is, since the radius of curvature of each of the bottom cutting edge 11 and the outer peripheral cutting edge 9 can be set sufficiently larger than 1/2 of the cutting edge diameter of the cutting edge portion 4 (1/2 of the tool diameter, which is the tool radius), The above-mentioned effects such as being able to increase the pitch P of the pick feed are more remarkable. In order to make the above effects more remarkable, the angle θ1 is preferably 28° or less (angle θ2 is 62° or more), and is preferably 25° or less (angle θ2 is 65° or more). is more desirable.

It should be noted that the present invention is not limited to the above-described embodiments, and, for example, as described below, changes in configuration can be made without departing from the gist of the present invention. In the drawings of the modified example, the same reference numerals are assigned to the same constituent elements as in the above-described embodiment and reference example, and mainly different points will be described.

21(a) to (c) show modifications of the cutting insert 5A of the first reference example. In this modification, as shown in FIG. 21(b), the axial rake angle of the peripheral cutting edge 9 has a positive value. The axial rake angle of the bottom cutting edge 11 has a positive value. The axial rake angle of the straight cutting edge 13 has a positive value. The axial rake angle at the connection point A between the bottom cutting edge 11 and the straight cutting edge 13 has a positive value. The axial rake angle at the connection point B between the peripheral cutting edge 9 and the straight cutting edge 13 has a positive value. That is, the axial rake angle of the peripheral cutting edge 9, the axial rake angle of the bottom cutting edge 11, and the axial rake angle of the straight cutting edge 13 are all positive angles.

Therefore, according to this modified example, chips generated during cutting are efficiently sent from the tip of the tool to the base end side, and chip discharge is excellent. In addition, since good chip discharging performance is maintained, cutting speed can be increased, and machining efficiency is improved.
In addition, since the rake face 19 is formed by one plane over the entire length of the cutting edge, the rake angle in the axial direction of the outer peripheral cutting edge 9, the rake angle in the axial direction of the straight cutting edge 13, and the rake angle in the axial direction of the bottom cutting edge 11 The rake angles are all the same angle β. As a result, the chip discharging performance is stably enhanced, and the cutting insert 5A is easy to manufacture.
Note that the modified example described above may be applied to the cutting inserts 5B to 5D of the second and third reference examples and the embodiment.

Further, in the above-described embodiment and reference example, the cutting inserts 5A to 5D are formed with the screw insertion holes 18, and the hole centers of the screw insertion holes 18 are positioned on the imaginary straight line VL. It is not limited. That is, the hole center of the screw insertion hole 18 does not have to be arranged on the imaginary straight line VL. However, arranging the hole center of the screw insertion hole 18 on the virtual straight line VL is preferable because the excellent effects described in the above-described embodiment and reference example can be obtained.
Moreover, the cutting inserts 5A to 5D may be formed without the screw insertion holes 18. In this case, the cutting inserts 5A to 5D are detachably attached to the mounting seat 3 of the tool body 1 by a clamping mechanism or the like. .

In the second reference example, the cutting edge portion 4 is provided with two straight cutting edges 13, and in the third reference example, the cutting edge portion 4 is provided with three straight cutting edges 13. Instead of these configurations, the cutting edge portion 4 may be provided with four or more straight cutting edges 13 . In this case, the cutting edge portion 4 is provided with four or more rake face portions 14 and four or more flank portions of the straight cutting edges 13 according to the number of the straight cutting edges 13 .

In addition, in the first to third reference examples, of the rake face 19, the rake face portion 12 of the bottom cutting edge 11, the rake face portion 10 of the outer peripheral cutting edge 9, and the rake face portion 14 of the straight cutting edge 13 are coplanar. Examples were given above. Moreover, in the embodiment, of the rake face 19, the rake face portion 12 of the bottom cutting edge 11 and the rake face portion 10 of the outer peripheral cutting edge 9 are formed on the same plane. The present invention is not limited to these configurations, and for example, the rake face portions 10, 12, 14 may be formed on the same curved surface (convex curved surface, concave curved surface). Alternatively, the rake face portions 10, 12, 14 may be formed by planes or curved surfaces different from each other.

In the above-described embodiment and reference example, the angle θ1 is 10 to 30° and the angle θ2 is (90°−θ1)°, but the numerical ranges of the angles θ1 and θ2 are the same as described above. Not limited.

In the above-described embodiments and reference examples, the material of the base (insert body 15) of the cutting inserts 5A to 5D is not only cemented carbide containing tungsten carbide (WC) and cobalt (Co), but also cermet, High-speed steel, titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, ceramics made of mixtures thereof, cubic boron nitride sintered bodies, diamond sintered bodies, polycrystalline diamond or cubic boron nitride It is also possible to use an ultra-high pressure sintered body in which a hard phase such as a ceramic or an iron group metal is sintered under an ultra-high pressure.
The tool body 1 may be made of alloy tool steel such as SKD61 or may be formed by joining alloy tool steel such as SKD61 and cemented carbide.

In addition, without departing from the scope of the present invention, the configurations (components) described in the above-described embodiments, modifications, reference examples, and remarks may be combined, and addition, omission, and replacement of configurations may be performed. , and other modifications are possible. Moreover, the present invention is not limited by the embodiments described above, but only by the claims.

The cutting insert and the indexable rotary cutting tool of the present invention can perform cutting work so that the properties of the machined surface are uniform, regardless of the machining site or shape of the workpiece. In addition, in finishing machining, semi-finishing machining, etc., good machined surface accuracy can be obtained over the entire machined surface. Therefore, it has industrial applicability.

1 tool body 2 tip portion 3 mounting seat 4 cutting edge portion 5A to 5D cutting insert 6A to 6D indexable rotary cutting tool 9 peripheral cutting edge 10 rake face portion of peripheral cutting edge 11 bottom cutting edge 12 rake face of bottom cutting edge Portion 13 Straight cutting edge 14 Rake face portion of straight cutting edge 15 Insert body 18 Screw insertion hole 19 Rake face A Radial outer end (connection point) of bottom cutting edge
B Tip of the peripheral cutting edge in the central axis direction (connection point)
C central axis CR central axis reference line D, E, F, G, H intersection L1 first tangent line L2 second tangent line LS line segment M midpoint RR radial reference line T1 first right triangle T2 second Right triangle VL Virtual straight line α Angle β Angle (axial rake angle)
θ1 angle θ2 angle

Claims (4)

A cutting insert detachably attached to a mounting seat formed at the tip of a tool body that is rotated around a central axis,
a plate-like insert body;
and a cutting edge portion formed on the insert body,
The cutting edge portion is
An arc-shaped bottom cutting edge that is disposed at the tip of the insert body in the central axis direction, extends along a radial direction perpendicular to the central axis, and protrudes toward the tip side in the central axis direction. and,
an arc-shaped peripheral cutting edge disposed at the outer end portion of the insert body in the radial direction, extending along the central axis direction, and protruding outward in the radial direction;
comprising a rake face and
While the outer end of the bottom cutting edge in the radial direction and the tip of the outer peripheral cutting edge in the central axis direction are directly connected,
Each curvature radius of the bottom cutting edge and the outer peripheral cutting edge is larger than 1/2 of the cutting edge diameter of the cutting edge portion,
Looking at the rake face from the front,
An imaginary straight line that intersects the central axis at an angle of 45° and extends toward the tip side in the central axis direction as it goes outward in the radial direction is set as a symmetrical axis, and the bottom cutting edge and the outer peripheral cutting edge are formed to be line-symmetrical with each other. A cutting insert detachably attached to a mounting seat formed at the tip of a tool body that is rotated around a central axis,
a plate-like insert body;
and a cutting edge portion formed on the insert body,
The cutting edge portion is
An arc-shaped bottom cutting edge that is disposed at the tip of the insert body in the central axis direction, extends along a radial direction perpendicular to the central axis, and protrudes toward the tip side in the central axis direction. and,
an arc-shaped peripheral cutting edge disposed at the outer end portion of the insert body in the radial direction, extending along the central axis direction, and protruding outward in the radial direction;
comprising a rake face and
The radius of curvature of the bottom cutting edge and the radius of curvature of the peripheral cutting edge are the same,
While the outer end of the bottom cutting edge in the radial direction and the tip of the outer peripheral cutting edge in the central axis direction are directly connected,
Each curvature radius of the bottom cutting edge and the outer peripheral cutting edge is larger than 1/2 of the cutting edge diameter of the cutting edge portion,
Looking at the rake face from the front,
A straight line extending along the radial direction passing through the tip of the bottom cutting edge in the central axis direction is defined as a radial reference line,
A straight line passing through the outer end of the outer peripheral cutting edge in the radial direction and extending along the central axis direction is defined as a central axis direction reference line,
A tangent line of the bottom cutting edge at the outer end of the bottom cutting edge in the radial direction is a first tangent line,
A tangent to the outer peripheral cutting edge at the tip of the outer peripheral cutting edge in the central axis direction is defined as a second tangent,
The intersection of the first tangent line and the radial reference line, the intersection of the first tangent line and the central axial reference line, and the intersection of the radial reference line and the central axial reference line, A first right triangle is defined as a right triangle formed by connecting them with straight lines,
The intersection of the second tangent line and the central axial reference line, the intersection of the second tangent line and the radial reference line, and the intersection of the radial reference line and the central axial reference line, Assuming that the right-angled triangles formed by connecting them with straight lines are the second right-angled triangles,
The cutting insert, wherein the first right triangle and the second right triangle are congruent with each other. The cutting insert according to claim 1 or 2,
Looking at the rake face from the front,
A straight line extending along the radial direction passing through the tip of the bottom cutting edge in the central axis direction is defined as a radial reference line,
A tangent line of the bottom cutting edge at the outer end of the bottom cutting edge in the radial direction is a first tangent line,
With the tangent line of the outer peripheral cutting edge at the tip of the outer peripheral cutting edge in the central axis direction as a second tangent line,
an angle θ1 formed between the first tangent line and the radial reference line is 10 to 30°;
The cutting insert, wherein an angle θ2 formed between the second tangent line and the radial reference line is (90°−θ1)°. a tool body that can be rotated around a central axis;
a mounting seat formed at the tip of the tool body;
A cutting insert detachably attached to the mounting seat, and an indexable rotary cutting tool comprising:
An indexable rotary cutting tool using the cutting insert according to any one of claims 1 to 3 as the cutting insert.

Images