JP2022058916A - Cutting insert and tip replaceable rotary cutting tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase processing efficiency while securing accuracy on a machined surface.

SOLUTION: A cutting insert comprises a plate-like insert body 15, and cutting edge parts 4 formed on the insert body 15. The cutting edge part 4 includes: a bottom cutting edge 11 which is disposed at a tip in a center axis C direction of the insert body 15, and formed like a circular arc protruding toward a tip side in the center axis C direction; an outer peripheral cutting edge 9 which is disposed at an outer end in a radial direction of the insert body 15, and formed like a circular arc protruding to the outside in the radial direction; and a connection edge 13 which connects the bottom cutting edge 11 to the outer peripheral cutting edge 9. In the cutting insert, curvature radius of the bottom cutting edge 11 and curvature radius of the outer peripheral cutting edge 9 are half or more of an edge diameter D of the cutting edge part 4, and at least one of the curvature radius of the bottom cutting edge 11 and the curvature radius of the outer peripheral cutting edge 9 is larger than half of the edge diameter D. Further, when viewing a rake face 19 as a front face, an edge diameter center point and a virtual straight line passing through an edge length center of the connection edge 13 intersect at an angle α to the center axis C, and the angle α satisfies 10°≤α<45°.

SELECTED DRAWING: Figure 16

COPYRIGHT: (C)2022,JPO&INPIT

Description

The present invention relates to a cutting insert and a rotary cutting tool with a replaceable cutting edge.

Conventionally, for example, a ball end mill with a replaceable cutting edge (rotary cutting tool with a replaceable cutting edge) according to Patent Document 1 below is known. The cutting edge of the cutting insert of this replaceable cutting edge ball end mill is arcuate. The cutting edge has a constant radius of curvature over the entire blade length from the tool tip to the radial outer edge. The radius of curvature of the cutting edge is 1/2 of the tool blade diameter (diameter).

JP-A-2017-61009

With this type of rotary cutting tool with replaceable cutting edge, there is room for improvement in terms of improving machining efficiency while ensuring machined surface accuracy.

In view of the above circumstances, it is an object of the present invention to provide a cutting insert capable of improving machining efficiency while ensuring machining surface accuracy, and a cutting tool with a replaceable cutting edge using the cutting insert.

The cutting insert according to one aspect of the present invention includes a plate-shaped insert main body and a cutting edge portion formed on the insert main body, and the cutting edge portion is arranged at a tip portion in the central axial direction of the insert main body. The bottom cutting edge is formed in an arc shape that is convex toward the tip end side in the central axis direction, and is arranged at the outer end portion of the insert body in the radial direction orthogonal to the central axis. It has an outer peripheral cutting edge formed in an arc shape that is convex toward the outside, and a connecting blade that connects the bottom cutting edge and the outer peripheral cutting edge, and has a radius of curvature of the bottom cutting edge and the outer peripheral cutting edge. The radius of curvature of the blade is ½ or more of the blade diameter of the cutting edge portion, and at least one of the radius of curvature of the bottom cutting edge and the radius of curvature of the outer peripheral cutting edge is 1 / of the blade diameter. The central axis, which is larger than 2 and is located at a distance of 1/2 of the blade diameter from the tip of the insert body in the central axis direction toward the proximal end side when the rake face of the cutting edge portion is viewed from the front. The upper point, the center point of the blade diameter, and the virtual straight line passing through the center of the blade length of the connecting blade intersect the central axis at an angle α, and the angle α is 10 ° ≦ α <45 °. It is characterized by being.
Further, the cutting insert according to one aspect of the present invention includes a plate-shaped insert body and a cutting edge portion formed on the insert body, and the cutting edge portion is a tip portion in the central axis direction of the insert body. A bottom cutting edge formed in an arc shape that is convex toward the tip side in the central axis direction, and a radial outer end portion of the insert body perpendicular to the central axis. It has an outer peripheral cutting edge formed in an arc shape that is convex toward the outside in the direction, and the radius of curvature of the bottom cutting edge and the radius of curvature of the outer peripheral cutting edge are 1 of the blade diameter of the cutting edge portion. / 2 or more, and at least one of the radius of curvature of the bottom cutting edge and the radius of curvature of the outer peripheral cutting edge is larger than 1/2 of the blade diameter, and the rake face of the cutting edge portion faces the front. As seen, the radial outer portion of the bottom cutting edge and the tip end side portion of the outer peripheral cutting edge in the central axis direction are formed in a line-symmetrical shape with a virtual straight line as the axis of symmetry. The virtual straight line intersects the central axis at an angle α, and the angle α is characterized in that 10 ° ≦ α <45 °.
Further, the cutting insert according to one aspect of the present invention includes a plate-shaped insert main body and a cutting edge portion formed on the insert main body, and the cutting edge portion includes a rake face and a central axis of the insert main body. The bottom cutting edge, which is arranged at the tip portion in the direction, extends along the radial direction orthogonal to the central axis, and is formed in an arc shape that is convex toward the tip side in the central axis direction, and the insert body. It has an outer peripheral cutting edge that is arranged at the outer end portion in the radial direction, extends along the central axis direction, and is formed in an arc shape that is convex toward the outside in the radial direction, and has the rake face. Of these, the portion of the bottom cutting edge adjacent to the proximal end side in the central axis direction is the rake face portion of the bottom cutting edge, and the rake face portion of the bottom cutting edge is flat and the rake surface. Of these, the portion adjacent to the inner side of the outer peripheral cutting edge in the radial direction is the rake face portion of the outer peripheral cutting edge, the rake surface portion of the outer peripheral cutting edge is flat, and the rake surface portion of the bottom cutting edge. The rake face portion of the outer peripheral cutting edge is formed on the same plane, and the radius of curvature of the bottom cutting edge and the radius of curvature of the outer peripheral cutting edge are ½ or more of the blade diameter of the cutting edge portion. Moreover, at least one of the radius of curvature of the bottom cutting edge and the radius of curvature of the outer peripheral cutting edge is larger than 1/2 of the blade diameter, and the rotation locus of the bottom cutting edge around the central axis is the center. It has a convex lens shape that bulges toward the tip side in the axial direction, and the rotation locus of the outer peripheral cutting edge around the central axis has a barrel shape that bulges outward in the radial direction, and the curvature of the outer peripheral cutting edge. The radius is larger than the radius of curvature of the bottom cutting edge.
Further, the blade tip exchange type rotary cutting tool according to one aspect of the present invention includes a tool body that is rotated around a central axis and the above-mentioned cutting insert that is attached to the tip portion of the tool body in the central axis direction. It is characterized by that.

INDUSTRIAL APPLICABILITY According to the present invention, there is provided a cutting insert and a cutting tool with a replaceable cutting edge that can improve machining efficiency while ensuring machining surface accuracy.

It is a perspective view which shows the cutting edge exchange type rotary cutting tool of 1st Embodiment of this invention. It is a top view of the rotary cutting tool with exchangeable cutting edge. It is a side view of the cutting edge exchange type rotary cutting tool. It is a front view of a rotary cutting tool with a replaceable cutting edge. It is a perspective view which shows the cutting insert of 1st Embodiment. It is (a) plan view, (b) side view, (c) front view which shows the cutting insert (plate surface reference). It is (a) plan view, (b) side view, (c) front view which shows the cutting insert (the rake face reference). It is (a) plan view, (b) side view, (c) front view which shows the modification of the cutting insert of 1st Embodiment. (A) The figure which shows the pitch and the cusp height of the pick feed of the machined surface cut by the cutting insert and the cutting edge exchange type rotary cutting tool of this invention, (b) the pitch and cusp height of the pick feed of the machined surface cut by the conventional ball end mill. It is a figure which shows. It is a perspective view which shows the cutting edge exchange type rotary cutting tool of the 2nd Embodiment of this invention. It is a top view of the rotary cutting tool with exchangeable cutting edge. It is a side view of the cutting edge exchange type rotary cutting tool. It is a front view of a rotary cutting tool with a replaceable cutting edge. It is a perspective view which shows the cutting insert of 2nd Embodiment. It is (a) plan view, (b) side view, (c) front view which shows the cutting insert (plate surface reference). It is (a) plan view, (b) side view, (c) front view which shows the cutting insert (the rake face reference). It is (a) plan view, (b) side view, (c) front view which shows the modification of the cutting insert of 2nd Embodiment. It is a perspective view which shows the cutting edge exchange type rotary cutting tool of the 3rd Embodiment of this invention. It is a top view of the rotary cutting tool with exchangeable cutting edge. It is a side view of the cutting edge exchange type rotary cutting tool. It is a front view of a rotary cutting tool with a replaceable cutting edge. It is a perspective view which shows the cutting insert of the 3rd Embodiment. It is (a) plan view, (b) side view, (c) front view which shows the cutting insert (plate surface reference). It is (a) plan view, (b) side view, (c) front view which shows the cutting insert (the rake face reference). It is (a) plan view, (b) side view, (c) front view which shows the modification of the cutting insert of 3rd Embodiment. It is a perspective view which shows the cutting edge exchange type rotary cutting tool of 4th Embodiment of this invention. It is a perspective view which shows the cutting insert of 4th Embodiment. It is a perspective view which shows the cutting edge exchange type rotary cutting tool of 5th Embodiment of this invention. It is a perspective view which shows the cutting insert of 5th Embodiment. It is a perspective view which shows the cutting edge exchange type rotary cutting tool of the 6th Embodiment of this invention. It is a perspective view which shows the cutting insert of the 6th Embodiment. It is a perspective view which shows the cutting edge exchange type rotary cutting tool of 7th Embodiment of this invention. It is a perspective view which shows the cutting insert of 7th Embodiment.

<First Embodiment>
Hereinafter, the cutting insert 5A according to the first embodiment of the present invention and the cutting edge exchangeable rotary cutting tool 6A provided with the cutting insert 5A will be described with reference to FIGS. 1 to 9. In addition, in the drawing used for the description of the embodiment, in order to make it easy to understand the features of the present invention, the main part may be enlarged, emphasized, or excerpted.

The rotary cutting tool 6A with a replaceable cutting edge of the present embodiment can perform a plurality of types of cutting including front cutting (flat surface processing) and side surface cutting (standing wall surface processing) on the work material. The rotary cutting tool 6A with a replaceable cutting edge can obtain excellent machined surface accuracy especially in finishing and semi-finishing of the machined surface.

As shown in FIGS. 1 to 4, the cutting edge exchange type rotary cutting tool 6A includes a tool body 1 and a cutting insert 5A. The tool body 1 has a columnar shape and is rotated around the central axis C. The cutting insert 5A is attached to one end (tip) 2 of both ends of the tool body 1 in the central axis C direction. A mounting seat (insert mounting seat) 3 is formed on one end 2 of the tool body 1. A cutting insert 5A is detachably attached to the attachment seat 3.

The cutting insert 5A includes a plate-shaped insert main body 15 and a cutting edge portion 4 formed on the insert main body 15. The cutting edge portion 4 has a bottom cutting edge 11, an outer peripheral cutting edge 9, and a connecting blade 13. The bottom cutting edge 11, the outer peripheral cutting edge 9, and the connecting blade 13 are arranged on the peripheral edge portion of the insert main body 15.

In the description of the embodiment, 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. Of the central axis C directions, the direction from the mounting seat 3 of the tool body 1 to the end (the other end) opposite to the mounting seat 3 of the tool body 1 is referred to as the proximal end side. The base end side is the upper side in FIGS. 2 and 3. Of the central axis C direction, the direction from the end of the tool body 1 opposite to the mounting seat 3 toward the mounting seat 3 is referred to as the tip side. The tip side is the lower part in FIGS. 2 and 3.
The direction orthogonal to the central axis C is called the radial direction. Of the radial directions, the direction closer to the central axis C is called the inner side in the radial direction, and the direction away from the central axis C is called the outer side in the radial direction.
The direction that orbits around the central axis C is called the circumferential direction. Of the circumferential directions, the direction in which the tool body 1 is rotated during cutting is called the tool rotation direction R, and the rotation direction opposite to this is called the anti-tool rotation direction.

The cutting insert 5A is arranged on the mounting seat 3 of the tip portion 2 of the tool body 1 in a posture in which the central axis (insert central axis) thereof coincides with the central axis C of the tool body 1. That is, the central axis C of the tool body 1 and the central axis of the cutting insert 5A are arranged coaxially with each other. Therefore, the above definition of orientation applies similarly to the cutting insert 5A. In FIGS. 5 to 8 and the like showing the cutting insert 5A, the central axis of the cutting insert 5A is represented by using the same reference numeral C as the central axis C of the tool body 1.

Specifically, in the cutting insert 5A, the direction from the bottom cutting edge 11 to the end of the insert body 15 opposite to the bottom cutting edge 11 in the direction of the central axis C is the proximal end side. In the direction C of the central axis, the direction from the end of the insert body 15 opposite to the bottom cutting edge 11 toward the bottom cutting edge 11 is the tip side.
The direction orthogonal to the central axis C is the radial direction. Of the radial directions, the direction closer to the central axis C is the inner side in the radial direction, and the direction away from the central axis C is the outer side in the radial direction.
The direction of orbiting around the central axis C is the circumferential direction. Of the circumferential directions, the direction in which the rake face 19 described later of the cutting edge portion 4 faces is the tool rotation direction R, and the rotation direction opposite to this is the anti-tool rotation direction (opposite to the tool rotation direction R). be.

The tool body 1 is formed of, for example, a steel material. The base end portion of the tool body 1 is attached to a spindle of a machine tool (not shown). By rotationally driving the spindle, the tool body 1 is rotated in the tool rotation direction R around the central axis C. The tool body 1 is moved together with the spindle in the central axis C direction, the radial direction, the combined direction thereof, and the like. As a result, the rotary cutting tool 6A with a replaceable cutting edge performs milling processing (milling processing) on the work material made of a metal material or the like at the cutting edge portion 4 of the cutting insert 5A. The blade tip exchange type rotary cutting tool 6A of the present embodiment is more preferably used for a machine tool such as a machining center with multi-axis control of 4 to 6 axes, for example.

In FIGS. 1 to 4, the mounting seat 3 includes a slit-shaped insert insertion groove 7 formed in the tip portion 2 of the tool body 1 and a fixing screw 8 for fixing the cutting insert 5A inserted in the insert insertion groove 7. , Equipped with.

The insert insertion groove 7 opens on the tip 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 insertion groove 7 is recessed from the tip surface of the tool body 1 toward the proximal end side, and has a slit shape that penetrates the tool body 1 in the radial direction. The bottom surface of the groove located at the base end portion of the insert insertion groove 7 and facing the tip end side is V-shaped and is concave toward the base end side.

By forming the insert insertion groove 7 in the tip portion 2 of the tool body 1, the tip portion 2 is divided into two, and a pair of tip half body portions (half pieces) are formed in the tip portion 2. The tip portion 2 is formed with a screw hole that penetrates one tip half body portion and extends into the other tip half body portion. Of the screw holes, the inner diameter of the hole portion formed in one tip half body portion is larger than the inner diameter of the hole portion formed in the other tip half body portion. A female screw portion to be screwed with the male screw portion of the fixing screw 8 is formed on the inner peripheral surface of the hole portion of the screw hole formed in the other tip half body portion. Of the screw holes, the hole portion formed in at least one of the tip half bodies is a through hole. In the example of the present embodiment, each hole portion of one tip half body portion and the other tip half body portion is a through hole.

The cutting insert 5A is formed of, for example, a cemented carbide. The cutting insert 5A has a higher hardness than the tool body 1. The cutting insert 5A attached to the mounting seat 3 of the tool body 1 is arranged such that the cutting edge portion 4 protrudes toward the tip end side of the tool body 1 and outward in the radial direction.
As shown in FIGS. 5 to 7, the cutting insert 5A of the present embodiment is formed in front-to-back inversion symmetry (180 ° rotational symmetry) with the central axis C as the axis of symmetry.

In the example of this embodiment, the insert body 15 has a pentagonal plate shape. A pair of plate surfaces facing the thickness direction of the insert body 15 are indicated by reference numerals 16 and 17. The insert body 15 is formed with a screw insertion hole 18 that penetrates the insert body 15 in the thickness direction. The screw insertion hole 18 opens in one plate surface 16 and the other plate surface 17. When the cutting insert 5A is mounted on the mounting seat 3 of the tool body 1 and fixed, the fixing screw 8 is inserted into the screw insertion hole 18.

The cutting edge portion 4 is arranged at the tip end portion in the central axis C direction and the outer end portion in the radial direction in the insert main body 15. The cutting edge portion 4 has a rake face 19, a flank intersecting the rake face 19, and a cutting edge formed on the intersecting ridge line between the rake face 19 and the flank surface.
The cutting edge includes the bottom cutting edge 11, the outer peripheral cutting edge 9, and the connecting blade 13 described above. The cutting edge is formed in a substantially L shape as a whole. The rake face portions 10, 12, 14 of the rake face 19, which will be described later, and the flank portion of the flank are arranged adjacent to the outer peripheral cutting blade 9, the bottom cutting blade 11, and the connecting blade 13, respectively.

The cutting insert 5A of the present embodiment is a two-flute cutting insert, and is a set of the cutting edges provided with an outer peripheral cutting edge 9, a bottom cutting edge 11 and a connecting blade 13 at 180 ° about the central axis C. It has two sets in rotational symmetry.

As shown in FIGS. 6 (a) to 6 (c) and FIGS. 7 (a) to 7 (c), the bottom cutting edge 11 is arranged at the tip end portion of the insert body 15 in the central axis C direction. The bottom cutting edge 11 is formed in an arc shape that is convex toward the tip end side in the central axis C direction. The bottom cutting edge 11 extends along the radial direction. The bottom cutting edge 11 is a so-called "lens" having a convex arc shape.

The radial outer end A of the bottom cutting edge 11 is connected to the connecting blade 13. The bottom cutting edge 11 is inclined and extends toward the tip end side in the central axis C direction from the outer end (connection point) A in the radial direction toward the inside in the radial direction. The amount of displacement of the bottom cutting edge 11 in the central axis C direction 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 toward it, 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 radial inner end of the bottom cutting edge 11 is located at the most advanced end in the central axis C direction. In the present embodiment, the radial inner end of the bottom cutting edge 11 is arranged on the central axis C. The tangent line (not shown) at the radial inner end of the bottom cutting edge 11 (the tip end in the central axis C direction) extends on a plane (horizontal plane) perpendicular to the central axis C.

When the cutting insert 5A is mounted on the mounting seat 3 (insert insertion groove 7) of the tool body 1 and the cutting tool 6A with replaceable cutting edge is rotated around the central axis C, the rotation locus of the bottom cutting edge 11 is on the tip side. It has a convex lens shape that bulges toward. Specifically, the rotation locus around the central axis C of the bottom cutting edge 11 is spherical. That is, the rotation locus of the bottom cutting edge 11 is formed so as to form an outer peripheral surface portion (spherical portion) of the sphere.

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

As shown in FIGS. 6A and 7A, of the rake face 19 facing the tool rotation direction R of the cutting edge portion 4, the bottom cutting edge 11 is adjacent to the base end side in the central axis C direction. The portion is the rake face portion 12 of the bottom cutting edge 11. In the example of this embodiment, the rake face portion 12 of the bottom cutting edge 11 is planar.

Of the tip surface of the insert body 15 facing the tip side in the central axis C direction, the portion adjacent to the counter-tool rotation direction of the bottom cutting edge 11 is the flank portion of the bottom cutting edge 11. The flank portion of the bottom cutting edge 11 has a curved surface shape that is convex toward the tip end side. The flank portion of the bottom cutting edge 11 is inclined toward the base end side in the central axis C direction from the bottom cutting edge 11 in the anti-tool rotation direction, whereby the flank angle of the bottom cutting edge 11 is increased. Is given.

As shown in FIGS. 6 (a) to 6 (c) and FIGS. 7 (a) to 7 (c), the outer peripheral cutting edge 9 is arranged at the outer end portion in the radial direction of the insert main body 15. The outer peripheral cutting edge 9 is formed in an arc shape that is convex toward the outside in the radial direction. The outer peripheral cutting edge 9 extends along the central axis C direction. The outer peripheral cutting edge 9 is a so-called "barrel", which is a convex arc-shaped cutting edge.

The tip B of the outer peripheral cutting edge 9 in the central axis C direction is connected to the connecting blade 13. The outer peripheral cutting edge 9 is inclined and extends outward in the radial direction from the tip end (connection point) B in the central axis C direction toward the proximal end side. The amount of radial displacement (that is, the inclination with respect to the central axis C direction) per unit length along the central axis C direction of the outer peripheral cutting edge 9 is based on the tip B of the outer peripheral cutting edge 9 in the central axis C direction. It gradually becomes smaller toward the end.

Of the total length of the cutting edge of the cutting edge portion 4, the base end of the outer peripheral cutting edge 9 in the central axis C direction is located at the outermost end in the radial direction.
When the cutting insert 5A is mounted on the mounting seat 3 of the tool body 1 and the cutting edge exchangeable rotary cutting tool 6A is rotated around the central axis C, the rotation locus of the outer peripheral cutting edge 9 bulges outward in the radial direction. It has a barrel shape (barrel shape).

In the example of this embodiment, as shown in FIG. 7B, the axial rake angle (corresponding to the helix angle) of the outer peripheral cutting edge 9 is 0 °. However, the present invention is not limited to this, and the axial rake angle of the outer peripheral cutting edge 9 may be a positive value or a negative value. Further, the radial rake angle of the outer peripheral cutting edge 9 is 0 °. However, the present invention is not limited to this, and the radial rake angle of the outer peripheral cutting edge 9 may be a positive value or a negative value.

As shown in FIGS. 6A and 7A, of the rake face 19 of the cutting edge portion 4 facing the tool rotation direction R, the portion adjacent to the radial inner side of the outer peripheral cutting edge 9 is the outer peripheral cutting. The rake face portion 10 of the blade 9. In the example of this embodiment, the rake face portion 10 of the outer peripheral cutting edge 9 is planar.

Of the outer peripheral surface of the insert body 15 facing outward in the radial direction, the portion adjacent to the outer peripheral cutting edge 9 in the anti-tool rotation direction is the flank portion of the outer peripheral cutting edge 9. The flank portion of the outer peripheral cutting edge 9 has a curved surface shape that is convex toward the outside in the radial direction. The flank portion of the outer peripheral cutting edge 9 is inclined inward in the radial direction from the outer peripheral cutting edge 9 in the anti-tool rotation direction, whereby the outer peripheral cutting edge 9 is provided with a clearance angle. ..

As shown in FIGS. 6 (a) to 6 (c) and FIGS. 7 (a) to 7 (c), the connecting blade 13 is arranged on the outer peripheral portion of the tip of the insert main body 15. The connecting blade 13 connects the bottom cutting blade 11 and the outer peripheral cutting blade 9. The connecting blade 13 connects the outer end A of the bottom cutting blade 11 in the radial direction and the tip B of the outer peripheral cutting blade 9 in the central axis C direction. The connecting blade 13 has an arcuate portion 13a that is convex toward the outer peripheral side of the tip. In the example of the present embodiment, the arcuate portion 13a is formed over the entire blade length of the connecting blade 13. The connecting blade 13 is a cutting edge having a convex arc shape.

The radial inner end of the connecting blade 13 is connected to the radial outer end (connection point) A of the bottom cutting blade 11. The connecting blade 13 is inclined and extends toward the base end side in the central axis C direction from the connection point A toward the outside in the radial direction. The displacement amount (that is, the inclination with respect to the radial direction) per unit length along the radial direction of the connecting blade 13 gradually increases from the connection point A toward the outside in the radial direction.

The base end of the connecting blade 13 in the central axis C direction is connected to the tip (connection point) B of the outer peripheral cutting edge 9 in the central axis C direction. The connecting blade 13 is inclined and extends inward in the radial direction from the connecting point B toward the tip end side in the central axis C direction. The displacement amount of the connecting blade 13 in the radial direction per unit length along the central axis C direction (that is, the inclination with respect to the central axis C direction) gradually increases from the connection point B toward the tip side.

In this embodiment, the connecting blade 13 is formed by one arcuate portion 13a. The radial inner end of the connecting blade 13 and the radial outer end of the bottom cutting edge 11 are in contact with each other at the connection point A. That is, the radial inner end of the connecting blade 13 and the radial outer end of the bottom cutting blade 11 have a common tangent at the connection point A and are connected to each other. The base end of the connecting blade 13 in the central axis C direction and the tip of the outer peripheral cutting edge 9 in the central axis C direction are in contact with each other at the connection point B. That is, the base end of the connecting blade 13 in the central axis C direction and the tip of the outer peripheral cutting edge 9 in the central axis C direction have a common tangent at the connection point B and are connected to each other.

When the cutting insert 5A is mounted on the mounting seat 3 of the tool body 1 and the cutting edge exchangeable rotary cutting tool 6A is rotated around the central axis C, the rotation locus of the connecting blade 13 is directed toward the tip side in the central axis C direction. It has a tapered tubular shape that shrinks in diameter accordingly.

In the example of this embodiment, as shown in FIG. 7B, the axial rake angle of the connecting blade 13 is 0 °. Therefore, the axial rake angle of the connecting blade 13 at the connection point A between the connecting blade 13 and the bottom cutting blade 11 is 0 °. Further, the axial rake angle of the connecting blade 13 at the connecting point B between the connecting blade 13 and the outer peripheral cutting edge 9 is 0 °. However, the present invention is not limited to this, and the axial rake angle of the connecting blade 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 connecting blade 13 is 0 °. However, the present invention is not limited to this, and the radial rake angle of the connecting blade 13 may be a positive value or a negative value.

As shown in FIGS. 6A and 7A, of the rake face 19 of the cutting edge portion 4 facing the tool rotation direction R, the portion of the connecting blade 13 inside the radial direction and adjacent to the proximal end side is , The rake face portion 14 of the connecting blade 13. In the example of this embodiment, the rake face portion 14 of the connecting blade 13 is planar.

Of the peripheral surfaces of the insert body 15 connecting the plate surfaces 16 and 17, the portion adjacent to the connecting blade 13 in the anti-tool rotation direction is the flank portion of the connecting blade 13. The flank portion of the connecting blade 13 has a curved surface shape that is convex toward the outer peripheral side of the tip. The flank portion of the connecting blade 13 is inclined toward the proximal end side in the central axis C direction and inward in the radial direction from the connecting blade 13 in the anti-tool rotation direction, thereby escaping to the connecting blade 13. The horns are given.

In FIGS. 7A and 7C, the radius of curvature of the bottom cutting edge 11 and the radius of curvature of the outer peripheral cutting edge 9 are ½ or more of the blade diameter D of the cutting edge portion 4, and the bottom cutting edge 11 At least one of the radius of curvature of the blade and the radius of curvature of the outer peripheral cutting edge 9 is larger than 1/2 of the blade diameter D. The above-mentioned "blade diameter D" is the outer diameter of the cutting edge portion 4 and is the maximum diameter. That is, the blade diameter D is the diameter of the rotation locus obtained by rotating the cutting edge portion 4 around the central axis C. In the present embodiment, the blade diameter D of the cutting edge portion 4 may be referred to as a tool blade diameter D.
That is, assuming that the radius of curvature of the bottom cutting edge 11 is X and the radius of curvature of the outer peripheral cutting edge 9 is Y, any of the following relationships I and II holds.
[I]
X ≧ 1 / 2D, Y> 1 / 2D
[II]
X> 1 / 2D, Y ≧ 1 / 2D

In the present embodiment, the radius of curvature of the bottom cutting edge 11 and the radius of curvature of the outer peripheral cutting edge 9 are both larger than 1/2 of the blade diameter D. Expressing this using the above X, Y, and D,
X> 1 / 2D, Y> 1 / 2D
Is.

In the present embodiment, 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 as each other. In the example of the present embodiment, the radius of curvature of the bottom cutting edge 11 and the radius of curvature of the outer peripheral cutting edge 9 are each equal to the tool blade diameter D. That is, the radius of curvature of the bottom cutting edge 11 and the radius of curvature of the outer peripheral cutting edge 9 are equal to the outer diameter of the rotation locus obtained by rotating the outer peripheral cutting edge 9 around the central axis C. Expressing this using the above X, Y, and D,
X = Y, X = D, Y = D
Is.

The radius of curvature of the connecting blade 13 (the arcuate portion 13a) is smaller than the radius of curvature of the bottom cutting edge 11 and the radius of curvature of the outer peripheral cutting edge 9. That is, assuming that the radius of curvature of the connecting blade 13 is Z, the following relationship holds.
X> Z, Y> Z

In this embodiment, the radius of curvature of the connecting blade 13 is smaller than 1/2 of the tool blade diameter D. in short,
1 / 2D> Z
Is.
In the example of the present embodiment, the radius of curvature of the connecting blade 13 is 1/3 or less with respect to the radius of curvature of the bottom cutting edge 11 and the radius of curvature of the outer peripheral cutting edge 9. in short,
1 / 3X ≧ Z, 1 / 3Y ≧ Z
Is. In the example of this embodiment, since the radius of curvature of the bottom cutting edge 11 and the radius of curvature of the outer peripheral cutting edge 9 are equal to the tool blade diameter D,
1 / 3D ≧ Z, 1 / 3D ≧ Z
Is.

As shown in FIGS. 6A and 7A, in the present embodiment, 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 connecting blade are used. The rake face portion 14 of 13 is formed on the same plane. That is, the entire rake face 19 of the cutting edge of the cutting edge portion 4 is formed by one flat surface.

As shown in FIG. 7A, when the rake face 19 is viewed from the front, the outer portion in the radial direction of the bottom cutting edge 11 and the tip end side portion of the outer peripheral cutting edge 9 in the central axis C direction are The virtual straight line VL is used as an axis of symmetry, and they are formed in a line-symmetrical shape with each other. The virtual straight line VL includes a blade diameter center point O1 which is a point on the central axis C located at a distance of 1/2 of the tool blade diameter D from the tip of the insert body 15 in the central axis C direction toward the base end side. It is a straight line passing through the arc center point O2 of the connecting blade 13. The virtual straight line VL is located at the same distance from the connection points A and B. The virtual straight line VL is orthogonal to the connecting blade 13 and passes through the center of the blade length of the connecting blade 13.

The virtual straight line VL intersects the central axis C at an angle α, and extends from the blade diameter center point O1 toward the tip end side in the central axis C direction as it goes outward in the radial direction. The above-mentioned "angle α" refers to an acute angle among the acute and obtuse angles formed by the intersection of the virtual straight line VL and the central axis C.
In this embodiment, the angle α is larger than 45 °. The angle α is, for example, 45 ° <α ≦ 55 °. The blade length of the bottom cutting edge 11 is longer than the blade length of the outer peripheral cutting edge 9. The angle α may be smaller than 45 °. In this case, the angle α is, for example, 10 ° ≦ α <45 °. The blade length of the outer peripheral cutting edge 9 is made longer than the blade length of the bottom cutting edge 11.
Further, regardless of the size of the angle α, the blade length of the connecting blade 13 is shorter than the blade length of the bottom cutting blade 11 and the blade length of the outer peripheral cutting blade 9.

In the example of the present embodiment, 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 connecting blade 13 are formed on the same plane with each other. In the above "looking at the rake face 19 from the front", the rake face portion 12 of the bottom cutting edge 11 is viewed from the front, the rake surface portion 10 of the outer peripheral cutting edge 9 is viewed from the front, and the connecting blade 13 It is synonymous with looking at the rake face portion 14 from the front.

In the front view of the rake face 19 shown in FIG. 7A, the hole center of the screw insertion hole 18 is located on the virtual straight line VL. Specifically, in the front view of the rake face 19, the hole center of the screw insertion hole 18 is arranged on the blade diameter center point O1 which is the intersection of the virtual straight line VL and the central axis C.

In the cutting insert 5A and the blade tip exchange type rotary cutting tool 6A of the present embodiment described above, the radius of curvature of the bottom cutting edge 11 and the radius of curvature of the outer peripheral cutting edge 9 are ½ or more of the blade diameter D of the cutting edge portion 4. Moreover, since at least one of the radius of curvature of the bottom cutting edge 11 and the radius of curvature of the outer peripheral cutting edge 9 is larger than 1/2 of the blade diameter D, the following effects are exhibited.

According to this embodiment, as compared with a conventional ball end mill or radius end mill, it is possible to shorten the machining time and improve the machining efficiency while maintaining good machining surface accuracy of the work material.
Specifically, in a conventional ball end mill, the cutting edge has a constant radius of curvature over the entire blade length from the tool tip to the radial outer end. The radius of curvature of the cutting edge is 1/2 of the tool blade diameter (outer diameter, diameter). Therefore, in the ball end mill, the pick feed is set so as to be equal to or less than a predetermined cusp height value according to the size of 1/2 (radius) of the blade diameter, and the cutting process is performed. Further, in the case of a radius end mill, a corner R cutting edge is used when cutting an inclined machined surface or a curved surface of a work material, and the radius of curvature of the corner R cutting edge is generally the cutting of a ball end mill. It is smaller than the radius of curvature of the blade (when the tool blade diameter is the same). Therefore, the pick feed of the radius end mill is smaller than the pick feed of the ball end mill.

On the other hand, in the present embodiment, the radius of curvature of the bottom cutting edge 11 and the outer peripheral cutting edge 9 is ½ or more of the tool blade diameter D, and each radius of curvature of the bottom cutting edge 11 and the outer peripheral cutting edge 9. One or more of them is larger than 1/2 of the tool blade diameter D. Therefore, in order to obtain a cusp height equivalent to the cusp height of the grain of the machined surface machined by the conventional ball end mill (that is, when the cusp height is set to a predetermined cusp height value or less), the pick feed (machining pitch) is set large according to the present embodiment. can.
In the example of the present embodiment, the radius of curvature of the bottom cutting edge 11 and the radius of curvature of the outer peripheral cutting edge 9 are equal to the tool blade diameter D. Therefore, the pick feed can be set to a value close to 1.4 times that of the conventional ball end mill.

Here, the difference between the present embodiment and the conventional pick feed will be described with reference to FIGS. 9 (a) and 9 (b). FIG. 9A shows an enlarged cross section of the machined surface (machining mark) of the work material W cut by the cutting insert 5A and the cutting edge replaceable rotary cutting tool 6A of the present embodiment, and is shown in FIG. 9B. ) Enlarges the cross section of the machined surface of the work material W cut by the conventional ball end mill. In the figure, reference numeral P is a pick feed pitch (machining pitch), and reference numeral CH is a cusp height. As shown in FIGS. 9A and 9B, when the cusp height CHs are set to be the same as each other, the processing pitch P of the pick feed can be made larger in the present embodiment of FIG. 9A.

According to this embodiment, the pick feed (machining pitch P) can be set large while keeping the cusp height CH small. As a result, the number of irregularities (scallops) given to the machined surface as machined marks can be reduced, and the machined surface accuracy can be improved. In addition, the toolpath length (total machining length) can be reduced by the amount of the larger pick feed, and the machining time can be shortened.

When a cutting test of the work material (S50C) was actually performed using the cutting tool 6A with a replaceable cutting edge equipped with the cutting insert 5A of the present embodiment and the ball end mill of the conventional example, the tool blade diameter was determined. When the cutting speed, the feed amount and the cusp height (scallop height) are set to be the same, the processing time of this embodiment is reduced by about 30% as compared with the conventional example. Further, the arithmetic mean roughness Ra and the ten-point average roughness Rz of the machined surface were both smaller than those of the conventional example in this embodiment, and it was confirmed that the machined surface accuracy was excellent.

From the above, according to the present embodiment, it is possible to improve the machining efficiency while ensuring the accuracy of the machined surface.

Further, in the present embodiment, since the cutting edge portion 4 has a connecting blade 13 for connecting the bottom cutting edge 11 and the outer peripheral cutting edge 9, the degree of freedom of each cutting edge shape of the bottom cutting edge 11 and the outer peripheral cutting edge 9 is increased. Increase. That is, since it is not necessary to directly connect the bottom cutting edge 11 and the outer peripheral cutting edge 9, the cutting edge of the bottom cutting edge 11 and the outer peripheral cutting edge 9 such as the radius of curvature and the blade length of each of the bottom cutting edge 11 and the outer peripheral cutting edge 9 according to the type of cutting. A large degree of freedom in shape is secured.

Further, by providing the connecting blade 13, it is possible to suppress the formation of a sharp corner portion at the connecting portion between the bottom cutting blade 11 and the outer peripheral cutting blade 9. As a result, chipping of the cutting edge portion 4 and the like can be suppressed.

Further, in the present embodiment, the connecting blade 13 has an arcuate portion 13a that is convex toward the outer peripheral side of the tip. Therefore, the connecting blade 13 can be used for different types of cutting than the bottom cutting edge 11 and the outer peripheral cutting edge 9, such as cutting a machined surface having a three-dimensional curved surface having a small radius of curvature.

Further, in the present embodiment, 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 as each other. The grain (machined grain, machined mark) and the grain formed on the machined surface by cutting the work material with the outer peripheral cutting edge 9 can have the same properties as each other.

Specifically, in order to make the cusp height of the machined surface cut by the bottom cutting edge 11 equal to the cusp height of the machined surface cut by the outer peripheral cutting edge 9, both should be machined with the same pick feed (machining pitch). Can be done. As a result, the grind by the bottom cutting edge 11 and the grind by the outer peripheral cutting edge 9 can be aligned with each other. Then, 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 outer peripheral cutting edge 9, the properties of the machined surface of the work material can be made uniform.

Since the properties of the machined surface of the work material can be made uniform, the surface roughness and gloss 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 the finishing process and the intermediate finishing process, it is possible to obtain an advantageous effect for improving the processing accuracy.

Further, in the present embodiment, the rotation locus around the central axis C of the bottom cutting edge 11 is spherical, and this rotation locus is formed like the outer peripheral surface portion (spherical portion) of the sphere. Therefore, for example, when face-cutting (flat surface machining) is performed on the work material, the above-mentioned effect that the pick feed (machining pitch) can be set large can be stably obtained.

Further, in the present embodiment, when the rake face 19 is viewed from the front, the radial outer portion of the bottom cutting edge 11 and the tip end side portion of the outer peripheral cutting edge 9 in the central axis C direction are symmetrical with respect to the virtual straight line VL. As axes, they are formed in a line-symmetrical shape with each other.
Therefore, for example, when face-cutting (flat surface machining) is performed on the work material, the grind imparted to the machined surface of the work material by cutting with the bottom cutting edge 11 and the side-cutting work on the work material. When performing (standing wall processing), it is easy to finish the grain provided on the machined surface of the work material by cutting with the outer peripheral cutting edge 9 to have the same properties.

Further, as in the present embodiment, when the angle α is larger than 45 ° and the blade length of the bottom cutting edge 11 is longer than the blade length of the outer peripheral cutting edge 9, for example, frontal cutting is mainly performed on the work material. Machining efficiency can be significantly improved when cutting (flat surface machining). Since the angle α is 55 ° or less, it is possible to prevent the blade length of the outer peripheral cutting edge 9 from becoming too short.

Further, when the angle α is smaller than 45 ° and the blade length of the outer peripheral cutting edge 9 is longer than the blade length of the bottom cutting edge 11, for example, side surface cutting (standing wall processing) is mainly performed on the work material. Machining efficiency can be significantly improved during cutting. Since the angle α is 10 ° or more, it is possible to prevent the blade length of the bottom cutting edge 11 from becoming too short.

Further, in the present embodiment, 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 connecting blade 13 are on the same plane. Is formed in. Therefore, the axial rake angle and the radial rake angle do not change over the entire length of the cutting edge.
In a general end mill or the like, among the rake faces of the cutting edge portion, the rake face portion of the bottom cutting edge and the rake face portion of the outer peripheral cutting edge are formed by different flat surfaces and curved surfaces. Since the connection point between the cutting edges is a portion where two cutting edges having different shapes are connected to each other, the axial rake angle and the radial rake angle change. Therefore, at the time of cutting, the cutting load in the vicinity of the connection point between the cutting edges tends to be large.

Therefore, 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 connecting blade 13 are formed on the same plane as in the present embodiment, the bottom is formed. At the connection point A between the cutting edge 11 and the connecting blade 13 and the connection point B between the outer peripheral cutting edge 9 and the connecting blade 13, the rake face of the cutting edge is formed by one flat surface.
As a result, it is possible to prevent the axial rake angle and the radial rake angle from changing significantly on both sides of the cutting edge sandwiching the connection points A and B, and the cutting edge bends at the connection points A and B. As a result, it is possible to suppress the action of a large cutting load in the vicinity of the connection points A and B. Therefore, the cutting edge strength at the connection portion between the connecting blade 13 and the bottom cutting edge 11 and the connecting portion between the connecting blade 13 and the outer peripheral cutting edge 9 is significantly increased, and the tool life is extended.

Further, 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 connecting blade 13 are formed on the same plane, the cutting insert 5A can be easily manufactured. be. Further, since no recess (valley) or the like is formed between these rake face portions 10, 12, and 14 (connection portion), the catching of chips during cutting is suppressed and the chip discharge property is improved. Be done.

Further, in the present embodiment, since the center of the screw insertion hole 18 is located on the virtual straight line VL when the rake face 19 is viewed from the front, the outer peripheral cutting edge is also formed during cutting using the bottom cutting edge 11. Even during the cutting process using 9, the force for rotating the cutting insert 5A around the screw insertion hole 18 (fixing screw 8) is suppressed.

Specifically, at the time of 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 center of the screw insertion hole 18. Further, at the time of cutting using the outer peripheral cutting edge 9, the cutting edge normal direction component of the cutting resistance received by the outer peripheral cutting edge 9 acts toward the center of the screw insertion hole 18. Therefore, the force for rotating the cutting insert 5A fixed by the fixing screw 8 around the fixing screw 8 is relaxed, and the micro-vibration (rotational micro-vibration) of the cutting insert 5A with respect to the mounting seat 3 is reduced. It is suppressed.

As a result, the properties of the machined surface of the work material are stable, and high-precision machining can be maintained satisfactorily. In particular, it is advantageous for high precision in so-called surface-based finishing and intermediate finishing, in which milling is performed on a three-dimensionally shaped component of a work material with a tool locus along the outer surface of the component. Effect can be obtained.
Further, at the time of cutting using the connecting blade 13, the cutting edge normal direction component of the cutting resistance received by the connecting blade 13 acts toward the center of the screw insertion hole 18. Therefore, even at the time of cutting using the connecting blade 13, the same operation and effect as described above can be obtained.

When the cutting insert 5A and the cutting edge exchange type rotary cutting tool 6A of the present embodiment are used for a machine tool such as a multi-axis control machining center, the action and effect of the present embodiment become more remarkable. The multi-axis control refers to control of, for example, 4 to 6 axes. The multi-axis control makes it easier to process a plurality of machined surfaces having different inclinations into more uniform properties. In this case, even a work material having a complicated three-dimensional curved surface such as a turbine blade can be stably cut with high accuracy.

Specifically, when a conventional ball end mill is used in a 3-axis controlled cutting method, it is difficult to improve both the machined surface accuracy and the machined efficiency.
According to the cutting insert 5A and the cutting edge exchangeable rotary cutting tool 6A of the present embodiment, it is possible to correspond to a processing machine by 5-axis control, and the outer peripheral cutting edge (barrel cutting edge) 9 and the bottom cutting edge (lens cutting edge) 11 By using these in combination, it has become possible to realize high-efficiency machining and high-precision machining at the same time.
For example, when the outer peripheral cutting edge (barrel cutting edge) 9 is used by inclining the tool axis, the machining pitch is set large on the inclined surface having the gradient of the work material to perform highly efficient machining. It is possible to set conditions and obtain a high-quality finished surface.
Further, when the bottom cutting edge (lens cutting edge) 11 is also used, the curved surface of the work material can be made into a high-quality finished surface as in the case of the outer peripheral cutting edge (barrel cutting edge) 9.
Furthermore, even when used in a 3-axis control processing machine, by using the outer peripheral cutting edge (barrel cutting edge) 9, a slope surface close to a vertical vertical wall or a bottom cutting edge (lens cutting edge) can be used. By using 11, the curved surface of the work material, which is close to a flat surface, can be machined under the condition that the machining pitch is set large.

8 (a) to 8 (c) show a modified example of the cutting insert 5A of this embodiment. In this modification, as shown in FIG. 8B, the axial rake angle of the outer 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 connecting blade 13 has a positive value. Further, the axial rake angle of the connecting blade 13 at the connection point A between the bottom cutting blade 11 and the connecting blade 13 has a positive value. The axial rake angle of the connecting blade 13 at the connection point B between the outer peripheral cutting blade 9 and the connecting blade 13 has a positive value. As described above, the axial rake angle of the outer peripheral cutting edge 9, the axial rake angle of the bottom cutting edge 11, and the axial rake angle of the connecting blade 13 are all positive angles.

In this modification, the axial rake angle of the outer peripheral cutting edge 9, the axial rake angle of the connecting blade 13, and the axial rake angle of the bottom cutting edge 11 are all the same angle β. The angle β is, for example, 0 ° <β ≦ 15 °. Further, the rake face 19 is formed by one flat surface over the entire cutting edge length of the cutting edge portion 4.

According to this modification, the sharpness is enhanced, the chips generated during cutting are efficiently sent from the tool tip to the base end side, and the chip discharge property is good. The flow of chips is stable on the rake face 19, and the chip discharge property is maintained well. The cutting speed can be increased and the machining efficiency is improved. By setting the angle β to 15 ° or less, the strength of the cutting edge can be secured and chipping and the like can be suppressed.

<Second Embodiment>
Next, the cutting insert 5B according to the second embodiment of the present invention and the cutting edge exchangeable rotary cutting tool 6B provided with the cutting insert 5B will be described with reference to FIGS. 10 to 17.
In the second embodiment, the same parts as the components in the first embodiment are designated by the same reference numerals, the description thereof will be omitted, and the differences will be mainly described.

As shown in FIGS. 10 to 16, the cutting insert 5B and the cutting edge exchangeable rotary cutting tool 6B of the present embodiment are different from the above-described embodiment in the configuration of the cutting edge of the cutting edge portion 4.
In the present embodiment, the radius of curvature of the outer peripheral cutting edge 9 is larger than the radius of curvature of the bottom cutting edge 11. That is, assuming that the radius of curvature of the bottom cutting edge 11 is X and the radius of curvature of the outer peripheral cutting edge 9 is Y.
Y> X
Is.

Further, the radius of curvature of the connecting blade 13 (the arcuate portion 13a) is smaller than the radius of curvature of the bottom cutting edge 11 and the radius of curvature of the outer peripheral cutting edge 9. That is, assuming that the radius of curvature of the connecting blade 13 is Z, the following relationship holds.
Y>X> Z

Further, in the present embodiment, the blade length of the cutting edge increases in the order of the connecting blade 13, the bottom cutting edge 11, and the outer peripheral cutting edge 9. In the illustrated example, the blade length of the outer peripheral cutting blade 9 is twice or more the blade length of the bottom cutting blade 11.

According to the cutting insert 5B and the cutting edge exchange type rotary cutting tool 6B of the present embodiment described above, the same operation and effect as those of the above-described embodiment can be obtained.
Further, in the present embodiment, since the radius of curvature of the outer peripheral cutting edge 9 is larger than the radius of curvature of the bottom cutting edge 11, the cusp height of the machined surface to be cut by the outer peripheral cutting edge 9 and the machined surface to be cut by the bottom cutting edge 11 In order to make the cusp height equivalent, the pick feed (machining pitch) can be set larger in the outer peripheral cutting edge 9 than in the bottom cutting edge 11. Therefore, for example, the processing efficiency can be remarkably improved at the time of cutting in which the side surface cutting process (standing wall surface processing) is mainly performed on the work material.

17 (a) to 17 (c) show a modification of the cutting insert 5B of this embodiment. In this modification, as shown in FIG. 17B, the axial rake angle of the outer 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 connecting blade 13 has a positive value. That is, the axial rake angle of the outer peripheral cutting edge 9, the axial rake angle of the bottom cutting edge 11, and the axial rake angle of the connecting blade 13 are all positive angles.
According to this modification, the sharpness is enhanced, the chips generated during cutting are efficiently sent from the tool tip to the base end side, and the chip discharge property is good. The cutting speed can be increased and the machining efficiency is improved.

<Third Embodiment>
Next, the cutting insert 5C according to the third embodiment of the present invention and the cutting edge exchangeable rotary cutting tool 6C provided with the cutting insert 5C will be described with reference to FIGS. 18 to 25.
In the third embodiment, the same parts as the components in the first and second embodiments are designated by the same reference numerals, the description thereof will be omitted, and the differences will be mainly described.

As shown in FIGS. 18 to 24, the cutting insert 5C and the cutting edge replaceable rotary cutting tool 6C of the present embodiment are different from the above-described embodiment in the configuration of the cutting edge of the cutting edge portion 4.
In the present embodiment, the radius of curvature of the bottom cutting edge 11 is larger than the radius of curvature of the outer peripheral cutting edge 9. That is, assuming that the radius of curvature of the bottom cutting edge 11 is X and the radius of curvature of the outer peripheral cutting edge 9 is Y.
X> Y
Is.

Further, the radius of curvature of the connecting blade 13 (the arcuate portion 13a) is smaller than the radius of curvature of the bottom cutting edge 11 and the radius of curvature of the outer peripheral cutting edge 9. That is, assuming that the radius of curvature of the connecting blade 13 is Z, the following relationship holds.
X>Y> Z

Further, in the present embodiment, the blade length of the cutting edge increases in the order of the connecting blade 13, the outer peripheral cutting edge 9, and the bottom cutting edge 11. In the illustrated example, the blade length of the bottom cutting edge 11 is twice or more the blade length of the outer peripheral cutting edge 9.

According to the cutting insert 5C and the cutting edge exchange type rotary cutting tool 6C of the present embodiment described above, the same operation and effect as those of the above-described embodiment can be obtained.
Further, in the present embodiment, since the radius of curvature of the bottom cutting edge 11 is larger than the radius of curvature of the outer peripheral cutting edge 9, the cusp height of the machined surface to be cut by the bottom cutting edge 11 and the machined surface to be cut by the outer peripheral cutting edge 9 In order to make the cusp height equivalent, the pick feed (machining pitch) can be set larger in the bottom cutting edge 11 than in the outer peripheral cutting edge 9. Therefore, for example, the processing efficiency can be remarkably improved at the time of cutting in which the work material is mainly subjected to front surface cutting (flat surface processing).

25 (a) to 25 (c) show a modified example of the cutting insert 5C of this embodiment. In this modification, as shown in FIG. 25 (b), the axial rake angle of the outer 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 connecting blade 13 has a positive value. That is, the axial rake angle of the outer peripheral cutting edge 9, the axial rake angle of the bottom cutting edge 11, and the axial rake angle of the connecting blade 13 are all positive angles.
According to this modification, the sharpness is enhanced, the chips generated during cutting are efficiently sent from the tool tip to the base end side, and the chip discharge property is good. The cutting speed can be increased and the machining efficiency is improved.

<Fourth Embodiment>
Next, the cutting insert 5D according to the fourth embodiment of the present invention and the cutting edge exchangeable rotary cutting tool 6D provided with the cutting insert 5D will be described with reference to FIGS. 26 and 27.
In the fourth embodiment, the same parts as the components in the first to third embodiments are designated by the same reference numerals, the description thereof will be omitted, and the differences will be mainly described.

As shown in FIGS. 26 and 27, the cutting insert 5D and the cutting edge exchangeable rotary cutting tool 6D of the present embodiment are different from the above-described embodiment in the configuration of the cutting edge of the cutting edge portion 4.
In FIG. 27, in the present embodiment, the connecting blade 13 has a linear portion 13b. In the example of this embodiment, the linear portion 13b is formed over the entire blade length of the connecting blade 13. The radial outer end (connection point A) of the bottom cutting edge 11 and the tip end (connection point B) of the outer peripheral cutting edge 9 in the central axis C direction are interposed via one linear portion 13b constituting the connecting blade 13. To connect. The connecting blade 13 is a linear cutting edge.

The connecting blade 13 is inclined toward the proximal end side in the central axis C direction from the radial inner end (connection point A) of the connecting blade 13 connected to the bottom cutting blade 11 toward the radial outer side. Is extending. The connecting blade 13 is inclined and extends inward in the radial direction from the base end (connection point B) in the central axis C direction of the connecting blade 13 connected to the outer peripheral cutting edge 9 toward the tip end side.

The angle at which the connecting blade 13 is inclined with respect to the radial direction and the central axis C direction is constant over the entire blade length of the connecting blade 13. The connecting blade 13 is connected to the bottom cutting blade 11 at a connection point A so as to form an obtuse angle portion with the bottom cutting blade 11. The connecting blade 13 is connected to the outer peripheral cutting edge 9 at a connection point B so as to form an obtuse-angled corner portion with the outer peripheral cutting edge 9.

In the present embodiment, 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 as each other. Further, the blade length of the bottom cutting edge 11 and the blade length of the outer peripheral cutting edge 9 are the same as each other. The blade length of the connecting blade 13 is shorter than the blade length of the bottom cutting blade 11 and the blade length of the outer peripheral cutting blade 9.

According to the cutting insert 5D and the cutting edge exchange type rotary cutting tool 6D of the present embodiment described above, the same operation and effect as those of the above-described embodiment can be obtained.
Further, in the present embodiment, the connecting blade 13 has a linear portion 13b. Therefore, using this connecting blade 13, for example, flat milling (finishing) of a work material, which is difficult to perform with high precision by a conventional ball end mill or the like, can be performed. That is, the connecting blade 13 has a function as a finishing blade for eliminating the grind. Therefore, according to this embodiment, it is possible to cope with various cutting processes.

In the example of the present embodiment, since the connecting blade 13 has one linear portion 13b, a large blade length of the linear portion 13b can be secured, and when this linear portion 13b is used for cutting. The feed amount can be increased, and flat milling can be performed efficiently.

<Fifth Embodiment>
Next, the cutting insert 5E according to the fifth embodiment of the present invention and the cutting edge exchangeable rotary cutting tool 6E provided with the cutting insert 5E will be described with reference to FIGS. 28 and 29.
In the fifth embodiment, the same parts as the components in the first to fourth embodiments are designated by the same reference numerals, the description thereof will be omitted, and the differences will be mainly described.

As shown in FIGS. 28 and 29, the cutting insert 5E and the cutting edge replaceable rotary cutting tool 6E of the present embodiment are different from the above-described embodiment in the configuration of the cutting edge of the cutting edge portion 4.
In FIG. 29, in the present embodiment, the connecting blade 13 has a plurality of linear portions 13b. The radial outer end (connection point A) of the bottom cutting edge 11 and the tip end (connection point B) of the outer peripheral cutting edge 9 in the central axis C direction are interposed via a plurality of linear portions 13b constituting the connecting blade 13. To connect. Specifically, the outer end in the radial direction of the bottom cutting edge 11 and the tip end in the central axis C direction of the outer peripheral cutting edge 9 are connected via two linear portions 13b.

The plurality of linear portions 13b extend in different directions from each other between the connection points A and B, and are formed continuously with each other.
Of the plurality of linear portions 13b, the linear portion (first linear portion) 13b connected to the bottom cutting edge 11 is in the direction of the central axis C as it goes outward in the radial direction from the connection point A. It extends incline toward the base end side. Of the plurality of linear portions 13b, the linear portion (second linear portion) 13b connected to the outer peripheral cutting edge 9 is inclined inward in the radial direction from the connection point B toward the tip side. And is extending.

The amount of displacement (that is, the inclination with respect to the radial direction) toward the central axis C per unit length in the radial direction in the first linear portion 13b is the above-mentioned virtual line segment (not shown) connecting the connection points A and B. It is smaller than the amount of displacement.
The amount of displacement of the second linear portion 13b toward the central axis C per unit length in the radial direction is larger than the amount of displacement of the virtual line segment.
The amount of displacement of the first linear portion 13b toward the central axis C per unit length in the radial direction is smaller than the amount of displacement of the second linear portion 13b.

In the present embodiment, the plurality of linear portions 13b (first linear portion 13b and second linear portion 13b) are arranged on the outer peripheral side of the tip of the tool with respect to the virtual line segment. When the rake face 19 is viewed from the front, the corners where the adjacent linear portions 13b are connected to each other are formed so as to form an obtuse angle that is convex toward the outer peripheral side of the tip of the tool. In the present embodiment, the blade length of the first linear portion 13b and the blade length of the second linear portion 13b are the same as each other.
The rake face portion 14 of the connecting blade 13 is formed by one flat surface. That is, each rake face portion of the plurality of linear portions 13b is formed on the same plane.

According to the cutting insert 5E and the cutting edge exchange type rotary cutting tool 6E of the present embodiment described above, the same operation and effect as those of the above-described embodiment can be obtained.
Further, in the present embodiment, since the connecting blade 13 has a plurality of linear portions 13b, it is possible to cope with various finishing processes by using each of the linear portions 13b.

Further, in the present embodiment, since the blade length of the first linear portion 13b and the blade length of the second linear portion 13b are the same as each other, the first linear portion 13b is used. The grain can be aligned by the finishing process and the finishing process using the second linear portion 13b. Therefore, the grinds imparted to the machined surface of the work material by cutting separately at the plurality of linear portions 13b have the same properties as each other.

Further, in the present embodiment, the connecting blade 13 has different cutting edge-shaped portions (first and second linear portions 13b), but the rake face portion 14 of the connecting blade 13 is one flat surface. Is formed by. Therefore, the local concentration of the cutting load acting on the connecting blade 13 can be suppressed, the strength of the cutting edge can be ensured, and the chip evacuation property can be improved.

<Sixth Embodiment>
Next, the cutting insert 5F according to the sixth embodiment of the present invention and the cutting edge exchangeable rotary cutting tool 6F provided with the cutting insert 5F will be described with reference to FIGS. 30 and 31.
In the sixth embodiment, the same parts as the components in the first to fifth embodiments are designated by the same reference numerals, the description thereof will be omitted, and the differences will be mainly described.

As shown in FIGS. 30 and 31, the cutting insert 5F and the cutting edge exchangeable rotary cutting tool 6F of the present embodiment are different from the above-described embodiment in the configuration of the cutting edge of the cutting edge portion 4.
In FIG. 31, in the present embodiment, the connecting blade 13 has three linear portions 13b. The radial outer end (connection point A) of the bottom cutting edge 11 and the tip end (connection point B) of the outer peripheral cutting edge 9 in the central axis C direction are connected via three linear portions 13b.

Looking at the rake face 19 from the front, the three linear portions 13b extend in different directions from each other between the connection points A and B. The three linear portions 13b include a linear portion (first linear portion) 13b connected to the bottom cutting edge 11 and a linear portion (second linear portion) connected to the outer peripheral cutting edge 9. 13b, and a linear portion (third linear portion) 13b located between the first linear portion 13b and the second linear portion 13b and connecting them. Is included. The third linear portion 13b is inclined and extends toward the base end side in the central axis C direction from the connection point with the first linear portion 13b toward the outer side in the radial direction.

The displacement amount of the third linear portion 13b toward the central axis C direction per unit length in the radial direction (that is, the inclination with respect to the radial direction) is larger than the displacement amount of the first linear portion 13b. , Is smaller than the displacement amount of the second linear portion 13b. In the present embodiment, the displacement amount of the third linear portion 13b and the displacement amount of the virtual line segment (not shown) connecting the connection points A and B are the same as each other. That is, the third linear portion 13b and the virtual line segment are parallel to each other.

In the present embodiment, the plurality of linear portions 13b (first to third linear portions 13b) are arranged on the outer peripheral side of the tip of the tool with respect to the virtual line segment. When the rake face 19 is viewed from the front, the corners where the adjacent linear portions 13b are connected to each other are formed so as to form an obtuse angle that is convex toward the outer peripheral side of the tip of the tool.

A connection point (corner portion) between the first linear portion 13b and the third linear portion 13b, and a connection point between the second linear portion 13b and the third linear portion 13b (the connection point between the second linear portion 13b and the third linear portion 13b). The corners) are arranged on the outer peripheral side of the tip of the tool with respect to the virtual line segment. In the present embodiment, the blade length of the first linear portion 13b, the blade length of the second linear portion 13b, and the blade length of the third linear portion 13b are the same as each other.

According to the cutting insert 5F and the cutting edge exchange type rotary cutting tool 6F of the present embodiment described above, the same operation and effect as those of the above-described embodiment can be obtained.
Further, in the present embodiment, the blade length of the first linear portion 13b, the blade length of the second linear portion 13b, and the blade length of the third linear portion 13b are the same as each other. , Finishing using the first linear portion 13b, finishing using the second linear portion 13b, and finishing using the third linear portion 13b to align the grain. be able to.

The blade length of the third linear portion 13b may be different from the blade length of the first and second linear portions 13b. That is, the blade length of the third linear portion 13b may be longer or shorter than the blade length of the first and second linear portions 13b. In this case, it is possible to support a wider variety of processing forms.

<7th Embodiment>
Next, the cutting insert 5G according to the seventh embodiment of the present invention and the cutting edge exchangeable rotary cutting tool 6G provided with the cutting insert 5G will be described with reference to FIGS. 32 and 33.
In the seventh embodiment, the same parts as the components in the first to sixth embodiments are designated by the same reference numerals, the description thereof will be omitted, and the differences will be mainly described.

As shown in FIGS. 32 and 33, the cutting insert 5G and the cutting edge exchangeable rotary cutting tool 6G of the present embodiment are different from the above-described embodiment in that the cutting edge portion 4 does not have the connecting blade 13. The configuration is different.

In the present embodiment, the bottom cutting edge 11 and the outer peripheral cutting edge 9 are directly connected. The radial outer end of the bottom cutting edge 11 (connection point A) and the tip end of the outer peripheral cutting edge 9 in the central axis C direction (connection point B) are directly connected. The radial outer end of the bottom cutting edge 11 and the tip end of the outer peripheral cutting edge 9 in the central axis C direction are directly connected to each other without passing through the connecting blade 13.

The connection point A is an end point connected to the outer peripheral cutting edge 9 in the bottom cutting edge 11, and the connection point B is an end point connected to the bottom cutting edge 11 in the outer peripheral cutting edge 9. The positions of the connection point A and the connection point B coincide with each other. In the present embodiment, the connecting blade 13 is not formed between the connecting point A and the connecting point B. Therefore, the rake face 19 of the cutting edge portion 4 does not have the rake face portion 14 of the connecting blade 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. Further, the flank of the cutting edge portion 4 does not have the flank portion of the connecting blade 13.
The corner portion connecting the radial outer end of the bottom cutting edge 11 and the tip of the outer peripheral cutting edge 9 in the central axis C direction is formed so as to form an obtuse angle that is convex toward the outer peripheral side of the tip of the tool. ..

According to the cutting insert 5G and the cutting edge exchange type rotary cutting tool 6G of the present embodiment described above, the same operation and effect as those of the above-described embodiment can be obtained.
Further, in the present embodiment, the bottom cutting edge 11 and the outer peripheral cutting edge 9 are directly connected. Therefore, it is possible to set the blade length of the bottom cutting edge 11 and the blade length of the outer peripheral cutting edge 9 to be long (longest). Therefore, the processing pitch of the pick feed can be increased while keeping the cusp height small. Therefore, the machining efficiency can be improved while maintaining good machining surface accuracy.

Further, the manufacturing of the cutting insert 5G can be simplified because the connecting blade 13, the rake face portion 14 of the connecting blade 13, and the flank portion of the connecting blade 13 are not formed.

The present invention is not limited to the above-described embodiment, and the configuration can be changed without departing from the spirit of the present invention, for example, as described below.

In the above-described embodiment, the insert main body 15 of the cutting inserts 5A to 5G has a pentagonal plate shape, but the present invention is not limited to this. The insert body 15 may have a plate shape such as a polygonal plate shape other than the pentagonal plate shape, for example.
Further, although it is assumed that the insert main body 15 of the cutting inserts 5A to 5G has the screw insertion hole 18, it is not necessary to have the screw insertion hole 18. In this case, the cutting inserts 5A to 5G are mounted on the mounting seat 3 of the tool body 1 by, for example, a clamp mechanism.

Further, in the first to third embodiments, the connecting blade 13 has one arc-shaped portion 13a, and the arc-shaped portion 13a is formed over the entire blade length of the connecting blade 13. Not limited to this. An arcuate portion 13a may be formed on a portion (part) of the connecting blade 13. Further, the connecting blade 13 may have a plurality of arcuate portions 13a. In this case, the plurality of arcuate portions 13a may have different radius of curvature, blade length, and the like.

Further, in the fifth embodiment, the connecting blade 13 is provided with two linear portions 13b, and in the sixth embodiment, the connecting blade 13 is provided with three linear portions 13b. Instead of these configurations, the connecting blade 13 may be provided with four or more linear portions 13b.
Further, the connecting blade 13 may have an arcuate portion 13a and a linear portion 13b. The connecting blade 13 may have a cutting edge-shaped portion other than the arc-shaped portion 13a and the linear portion 13b.
Further, in the above-described embodiment, the connecting blade 13 has a cutting edge function (cutting function), but is not limited to this. The connecting blade 13 may be a fake blade having no cutting function.

Further, in the first to sixth embodiments, among the rake faces 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 connecting blade 13 are on the same plane. I gave an example of what is formed in. Further, in the seventh embodiment, among the rake faces 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, and 14 may be formed on the same curved surface (convex curved surface, concave curved surface). Alternatively, the rake face portions 10, 12, and 14 may be formed by different planes or curved surfaces.

In the above-described embodiment, the material of the substrate (insert body 15) of the cutting inserts 5A to 5G is, for example, cermet or high-speed steel, in addition to the cemented carbide containing tungsten carbide (WC) and cobalt (Co). , Titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, and ceramics composed of a mixture thereof, cubic boron nitride sintered body, diamond sintered body, polycrystalline diamond or hard phase composed of cubic boron nitride. It is also possible to use an ultra-high pressure fired body that calcins the bonded phase of ceramics, iron group metal, etc. under ultra-high pressure.
Further, as the tool body 1, for example, in addition to the case of manufacturing with an alloy tool steel such as SKD61, it is also possible to use a tool body 1 formed by joining an alloy tool steel such as SKD61 and a cemented carbide.

In addition, as long as it does not deviate from the gist of the present invention, each configuration (component) described in the above-described embodiments, modifications, and notes may be combined, and additions, omissions, substitutions, and the like of the configurations may be combined. It can be changed. Further, the present invention is not limited to the above-described embodiments, but is limited only to the scope of claims.

The cutting insert and the rotary cutting tool with a replaceable cutting edge of the present invention can improve the machining efficiency while ensuring the machining surface accuracy. Therefore, it has industrial applicability.

1 Tool body 2 Tip part 4 Cutting edge part 5A-5G Cutting insert 6A-6G Cutting edge exchangeable rotary cutting tool 9 Outer cutting edge 11 Bottom cutting edge 13 Connecting blade 13a Arc-shaped part 13b Straight part 15 Insert body C center Shaft D Cutting edge diameter X Bottom cutting edge radius of curvature Y Outer peripheral cutting edge radius of curvature β Angle (axial rake angle)

Claims (4)

Plate-shaped insert body and
A cutting edge portion formed on the insert body is provided.
The cutting edge portion is
A bottom cutting edge that is arranged at the tip of the insert body in the central axis direction and is formed in an arc shape that is convex toward the tip side in the central axis direction.
An outer peripheral cutting edge that is arranged at the outer end portion in the radial direction orthogonal to the central axis of the insert body and is formed in an arc shape that is convex toward the outside in the radial direction.
It has a connecting blade that connects the bottom cutting edge and the outer peripheral cutting edge.
The radius of curvature of the bottom cutting edge and the radius of curvature of the outer peripheral cutting edge are ½ or more of the blade diameter of the cutting edge portion, and the radius of curvature of the bottom cutting edge and the radius of curvature of the outer peripheral cutting edge. At least one of them is larger than 1/2 of the blade diameter.
A point on the central axis located at a distance of 1/2 of the blade diameter from the tip of the insert body in the central axis direction toward the proximal end side when the rake face of the cutting edge portion is viewed from the front. The center point of the blade diameter and the virtual straight line passing through the center of the blade length of the connecting blade intersect with the center axis at an angle α.
The angle α is a cutting insert in which 10 ° ≦ α <45 °. Plate-shaped insert body and
A cutting edge portion formed on the insert body is provided.
The cutting edge portion is
A bottom cutting edge that is arranged at the tip of the insert body in the central axis direction and is formed in an arc shape that is convex toward the tip side in the central axis direction.
It has an outer peripheral cutting edge that is arranged at the outer end portion in the radial direction orthogonal to the central axis of the insert body and is formed in an arc shape that is convex toward the outside in the radial direction.
The radius of curvature of the bottom cutting edge and the radius of curvature of the outer peripheral cutting edge are ½ or more of the blade diameter of the cutting edge portion, and the radius of curvature of the bottom cutting edge and the radius of curvature of the outer peripheral cutting edge. At least one of them is larger than 1/2 of the blade diameter.
Looking at the rake face of the cutting edge portion from the front, the outer portion of the bottom cutting edge in the radial direction and the tip end side portion of the outer peripheral cutting edge in the central axis direction have a virtual straight line as an axis of symmetry. , Formed in line symmetry with each other,
The virtual straight line intersects the central axis at an angle α and
The angle α is a cutting insert in which 10 ° ≦ α <45 °. Plate-shaped insert body and
A cutting edge portion formed on the insert body is provided.
The cutting edge portion is
The rake face and
A bottom cutting edge that is arranged at the tip of the insert body in the central axis direction, extends along the radial direction orthogonal to the central axis, and is formed in an arc shape that is convex toward the tip side in the central axis direction. When,
It has an outer peripheral cutting edge that is arranged at the radial outer end of the insert body, extends along the central axis direction, and is formed in an arc shape that is convex toward the outside in the radial direction. ,
Of the rake face, the portion of the bottom cutting edge adjacent to the proximal end side in the central axial direction is the rake face portion of the bottom cutting edge, and the rake face portion of the bottom cutting edge is flat.
Of the rake face, the portion adjacent to the radial inner side of the outer peripheral cutting edge is the rake face portion of the outer peripheral cutting edge, and the rake face portion of the outer peripheral cutting edge is flat.
The rake face portion of the bottom cutting edge and the rake face portion of the outer peripheral cutting edge are formed on the same plane.
The radius of curvature of the bottom cutting edge and the radius of curvature of the outer peripheral cutting edge are ½ or more of the blade diameter of the cutting edge portion, and the radius of curvature of the bottom cutting edge and the radius of curvature of the outer peripheral cutting edge. At least one of them is larger than 1/2 of the blade diameter.
The rotation locus of the bottom cutting edge around the center axis has a convex lens shape that bulges toward the tip side in the center axis direction, and the rotation locus of the outer peripheral cutting edge around the center axis is radially outward. It has a barrel shape that bulges toward you,
A cutting insert in which the radius of curvature of the outer peripheral cutting edge is larger than the radius of curvature of the bottom cutting edge. The tool body that can be rotated around the central axis and
A rotary cutting tool with a replaceable cutting edge, comprising the cutting insert according to any one of claims 1 to 3, which is attached to the tip end portion of the tool body in the central axis direction.

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