JP2014087881A - Cutting insert and cutting edge replaceable cutting tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cutting insert that, even in high-feed processing, can smoothly produce and discharge chips, reduce cutting resistance, and further suppress increase in temperature of the chips to endure a longer service life and prevent abnormal damage of a cutting blade.SOLUTION: On a cutting face pointing in the thickness direction of a plate-like insert main body 1 is formed a cutting face 3, and on the circumferential face arranged around the face pointing in the thickness direction is formed a flank face 4. In a ridge line portion where the cutting face crosses the flank face is formed a cutting blade 5. The cutting blade has a convex curve portion 5a formed in a convex curve when viewed from a direction opposing to the cutting face. The cutting face is a positive cutting face that retreats to the center side in the thickness direction as the face recedes from the cutting blade. At least a portion that succeeds the convex curve portion of the cutting blade of the positive cutting face is formed in a planar shape.

Description

  The present invention relates to a cutting insert that is detachably attached to a cutting edge-exchangeable cutting tool used for milling, and a cutting edge-exchangeable cutting tool to which the cutting insert is attached.

  As a cutting edge exchange type cutting tool, high feed machining is known in which an end mill body as a tool body is fed at a high feed amount to cut a work material. As cutting inserts attached to such a high-feed cutting edge replaceable end mill, for example, in Patent Documents 1 and 2, a front surface and a back surface forming a substantially equilateral triangle are formed as a rake face, There has been proposed a negative type cutting insert in which a corner blade having an arc shape is formed at the corner portions of the front and back surfaces, and a main cutting edge is formed at the side ridge portions of the front and back surfaces that are connected to the corner blades.

  This cutting insert is directed to the end mill body rotating toward the end mill main body with one of the front and back surfaces facing the end mill rotating direction with one of the front and back surfaces as the rake face. The main cutting edge is attached so that a relatively small cutting angle, negative axial rake angle and radial rake angle are given, and usually it is fed at high speed in the direction perpendicular to the above-mentioned axis for cutting work. used. Since the cutting angle of the main cutting edge is relatively small, even if the feed is increased in this way, the thickness of the generated chips is reduced and efficient cutting can be performed.

Japanese Patent No. 3951766 Special table 2010-517802

  In the cutting inserts described in Patent Documents 1 and 2 above, the main cutting edge provided on the side ridges of the front and back surfaces forming a substantially equilateral triangle is formed in a convex curve shape when viewed from the direction facing the front and back surfaces. Yes. By the way, when the main cutting edge is formed so as to form a curve when viewed from the direction facing the front and back surfaces, for example, a positive rake face formed along the main cutting edge is usually in the thickness direction. The highest part (ridge-like part) is formed so as to extend toward the normal direction of the curve of the main cutting edge.

  However, when cutting is performed with such a cutting insert, the chips generated by the main cutting edge flow on the rake face so as to extend in the normal direction of the curve of the main cutting edge. When moving, a load that deforms the chip itself is applied. That is, for example, when the main cutting edge is formed in a convex curve shape when viewed from the direction facing the front and back surfaces, the chips generated by the convex curved main cutting edge move along the rake face. When receiving a load, the width is reduced by friction with the rake face. On the other hand, when the main cutting edge is formed in a concave curve shape when viewed from the direction facing the front and back surfaces, the chips generated by the concave curved main cutting edge move along the rake face. In addition, it receives a load that widens the width dimension by friction with the rake face.

  For this reason, the generation and discharge of chips are not performed smoothly, cutting resistance increases, or the wear of the cutting blade part increases with the increase in chip temperature, or the life of the cutting insert is shortened, or this cutting boundary part As a result, the cutting blade of the cutting insert may cause abnormal damage such as chipping or chipping. In particular, the problems associated with chip temperature rise are prominent when the object to be cut is a heat-resistant alloy such as stainless steel.

  The present invention has been made under such a background, and even during high-feed machining, chips are generated and discharged smoothly, cutting resistance can be reduced, and the temperature rise of the chips can be suppressed to extend the life. It is an object of the present invention to provide a cutting insert capable of reducing the cutting edge and preventing abnormal damage to the cutting blade, and a cutting edge exchangeable cutting tool having the cutting insert detachably attached thereto.

  In order to solve the above problems, a cutting insert according to the present invention has a rake face formed on a surface facing a thickness direction of a plate-like insert body, and is disposed around the surface facing the thickness direction. A flank is formed on the peripheral surface, a cutting edge is formed at the intersection ridge line portion between the rake face and the flank, and the cutting edge is a convex curve formed in a convex curve shape when viewed from the direction facing the rake face. The rake face is a positive rake face that retreats toward the center in the thickness direction as it is separated from the cutting edge, and at least a portion of the positive rake face that is continuous with the convex curve portion of the cutting edge is It is formed in one flat shape.

The cutting insert having the above configuration has a convex curve portion formed in a convex curve shape when viewed from the direction in which the cutting edge faces the rake surface, and a positive rake surface portion connected to the convex curve portion is formed in one flat shape. Has been. And the chip | tip produced | generated when cutting with the convex curve part of a cutting edge flows to the back | latter stage side along the positive rake face formed in one plane shape which is a part continuing to a convex curve part. In this way, since the chips move along only one flat portion, when the chips move on the positive rake face, a force that deforms the chips, for example, narrows the chips in the width direction. No load that spreads in the load or width direction is applied. As a result, chips are generated and discharged smoothly.
In this way, since the generation and discharge of chips are smooth, cutting resistance can be reduced, and it is possible to extend the life by suppressing the temperature rise of the chips and to prevent abnormal damage to the cutting blades. it can.

  The cutting edge has a concave curve portion formed in a concave curve shape when viewed from a direction facing the rake face, adjacent to the convex curve portion, and at least the convex curve portion of the positive rake face. The continuous part and the continuous part of the concave curve part may be formed in one flat shape.

Depending on the conditions required for cutting, the cutting blade may be formed with a convex curve portion viewed from the direction facing the rake face and a concave curve portion viewed from the same direction so as to be adjacent thereto. is there. Even in this case, at least the portion connected to the convex curve portion and the portion connected to the concave curve portion of the positive rake face are formed in a common plane, so that the convex curve portion adjacent to the cutting edge is formed. Chips generated when cutting at the concave curve portion move along one planar portion of the positive rake face. For this reason, an unnecessary load is not added when the chips move along the positive rake face, and the generation and discharge of the chips become smooth.
Here, the concave curve portion being formed adjacent to the convex curve portion is not limited to the case where the concave curve portion is formed continuously with the convex curve portion, and the convex curve portion and the concave curve portion. Including a case where a straight line portion is interposed between

  The insert body has a polygonal plate shape, the positive rake face is formed on the polygonal surface of the insert body, and the flank face is formed on the peripheral surface of the insert body disposed around the polygonal surface. A main cutting edge is formed at the side ridge portion of the polygonal surface at the intersecting ridge line portion between the rake face and the flank surface, and the main cutting edge is a portion of the corner of the polygonal surface. The convex curved portion and the concave curved portion may be formed adjacent to each other on the main cutting edge, extending between two corners adjacent to each other in the circumferential direction of the square surface.

Even when the insert body is formed in a polygonal plate shape and the main cutting edge is formed on the side ridge portion of the polygonal surface at the intersection ridgeline portion of the rake face and the flank face, When the chips move along one flat part of the positive rake face, when the chips move along the positive rake face, the chips generated when cutting at the adjacent convex curve part and concave curve part of the cutting edge move. In addition, no unnecessary load is applied, and generation and discharge of chips are smooth.
Moreover, since the insert body is formed in a polygonal plate shape and the main cutting edge is formed on the side ridge portion of the polygonal surface, a plurality of main cutting edges can be formed on one polygonal surface in the insert body. And can be cut individually by the plurality of main cutting edges.

The main cutting edge may be formed in a curved shape throughout.
When the convex curve portion and the concave curve portion of the main cutting edge do not have a straight line portion between them and the convex curve portion and the concave curve portion are continuous, chips generated when cutting with the convex curve portion of the main cutting edge Therefore, the chips generated when cutting with the main cutting edge at the boundary between the convex curve part and the concave curve part are the main behavior. When moving on the positive rake face connected to the cutting edge, there is a concern that an unnecessary load is applied to the chips.
However, even in this case, the chips generated when cutting with the main cutting edge at the boundary portion between the convex curve portion and the concave curve portion move along one planar portion of the positive rake face, When the chips move along the positive rake face, unnecessary load is not applied, and generation and discharge of the chips become smooth.

The highest part in the thickness direction in the cutting edge may be formed in the main cutting edge.
The load tends to concentrate on the highest portion in the thickness direction, and an excessive load may be applied. However, there is a place where the excessive load is applied to the main cutting edge, and the positive rake face portion connected to the convex curve portion and the concave curve portion of the main cutting edge is formed in one flat shape. When the chips move along the positive rake face, unnecessary load is not applied to the chips, and the generation and discharge of the chips become smooth. For this reason, it is possible to avoid applying a load to the main cutting edge through the chips, and it is possible to reduce the load burden when cutting with the main cutting edge.

A step inclined surface that is inclined more steeply than the angle of the positive rake face may be formed on the center side of the insert body of the positive rake face.
In this case, since a step surface inclined more steeply than the angle of the positive rake face is formed on the center side of the insert rake face of the positive rake face, chip separation from the positive rake face is good, and the cutting resistance is further increased. Can be reduced.

The insert body has a regular triangular plate shape, and the main cutting edge is formed on each side ridge portion of the polygonal surface on the front and back sides forming a regular triangle shape, and the polygonal surface on the front and back surfaces is formed of the polygonal surface. The insert body may be twisted around the center line of the insert passing through the center, and the insert body may be symmetrical with respect to the polygonal surfaces of the front and back sides.
The main cutting edge formed on the side ridge portion can be used for cutting evenly without interfering the front and back polygonal surfaces with one insert body.

The cutting edge-exchangeable cutting tool of the present invention comprises a tool body that is rotated in the direction of tool rotation around an axis, and the cutting insert that is detachably attached to the tip of the tool body. One or more insert mounting seats to which the cutting insert is attached are formed, and the cutting insert has the rake face facing the tool rotation direction and the cutting edge facing the tip side of the tool body. It is attached to the insert mounting seat.
Even in such a blade-tip-exchange-type cutting tool, the above-described effects can be obtained.

  As described above, according to the present invention, chips can be generated and discharged smoothly even during high-feed machining, cutting resistance can be reduced, and the life of the chips can be extended by suppressing the temperature rise of the chips. Can be prevented and abnormal damage to the cutting edge can be prevented.

It is a perspective view which shows embodiment of the cutting insert of this invention. It is a top view of the cutting insert. It is a side view of the arrow L direction view in FIG. It is a side view of the arrow M direction view in FIG. FIG. 3 is (a) AA enlarged sectional view, (b) BB enlarged sectional view, (c) DD enlarged sectional view, (d) EE enlarged sectional view, and (e) FF enlarged sectional view in FIG. 2. FIG. 3 is (a) XX enlarged sectional view, (b) YY enlarged sectional view, and (c) ZZ enlarged sectional view in FIG. 2. FIG. 2 is a perspective view of a tip end portion of an end mill body showing a blade edge replaceable end mill which is an embodiment of the blade edge replaceable cutting tool of the present invention to which the cutting insert of the embodiment shown in FIG. 1 is attached. FIG. 8 is an enlarged perspective view of a tip end portion of an end mill body in a state in which a cutting insert is removed in the blade edge replaceable end mill shown in FIG. 7. FIG. 8 is a perspective view of the blade edge replaceable end mill shown in FIG. 7. FIG. 8 is a plan view of the blade edge replaceable end mill shown in FIG. 7. It is a side view of the blade-tip-exchangeable end mill shown in FIG. FIG. 8 is an enlarged front view of the blade edge replaceable end mill shown in FIG. 7. It is a figure at the time of performing high feed processing, (a) is a figure which shows the cross section of the chip | tip produced | generated by the blade-tip-exchange-type end mill shown in FIG. 5, (b) is the blade-tip-exchange-type end mill which attached the conventional cutting insert. It is a figure which shows the cross section of the chip | tip produced | generated by.

FIGS. 1 to 6 show an embodiment of the cutting insert of the present invention, and FIGS. 7 to 12 show a blade edge replacement which is an embodiment of the cutting edge replaceable cutting tool of the present invention to which the cutting insert of this embodiment is attached. The type | formula end mill is shown.
1 is a perspective view of the cutting insert, FIG. 2 is a plan view of the cutting insert, FIG. 3 is a side view in the direction of arrow L in FIG. 1, and FIG. 4 is a side view in the direction of arrow M in FIG. 5 (a) is an AA enlarged sectional view in FIG. 2, FIG. 5 (b) is a BB enlarged sectional view in FIG. 2, FIG. 5 (c) is a DD enlarged sectional view in FIG. 2, and FIG. 5E is an FF enlarged sectional view in FIG. 2, FIG. 6A is an XX enlarged sectional view in FIG. 2, FIG. 6B is a YY enlarged sectional view in FIG. c) is a ZZ enlarged sectional view in FIG.

  In the cutting insert of the present embodiment, the insert body 1 is made of a hard plate selected from cemented carbide, cermet, surface-coated cemented carbide, surface-coated cermet, and the like. In this embodiment, it is formed in a regular triangular plate shape. At the center of a pair of front and back polygonal surfaces (first and second polygonal surfaces) of the insert body 1 having an equilateral triangle shape, the thickness direction of the insert body 1 (direction orthogonal to the drawing of FIG. 2; FIG. 5). (A) to (e), the vertical direction in FIGS. 6 (a) to (c)), and an attachment hole 2 for attaching the insert body 1 to the end mill body 11 of the blade tip replaceable end mill is opened. .

  Here, in this embodiment, the front and back polygonal surfaces of the insert body 1 pass through the center of the mounting hole 2 (the center of the front and back polygonal surfaces) as shown in FIG. It is arranged to be twisted slightly around the insert center line C extending in the direction. In addition, the insert body 1 of the present embodiment in the form of an equilateral triangle has a rotationally symmetric shape of 120 ° around the insert center line C, and the front and back equilateral triangle surfaces orthogonal to the insert center line C. The front and back are symmetrical with respect to three imaginary straight lines passing through the centers of the three side surfaces of the insert body 1 arranged around the periphery of the insert body 1.

  A rake face 3 is formed on the surface of the insert body 1 facing the thickness direction, that is, the front and back polygonal faces, and the side face of the insert body 1 disposed around these polygonal faces is escaped. A surface 4 is formed. Further, at the intersecting ridge line portion between the rake face 3 and the flank face 4, a main cutting edge 5 is formed at each side ridge portion of both polygonal surfaces, and a corner blade is provided at each corner portion of the polygonal surface. 6 is formed, and the corner blade 6 has a convex curve shape such as a 1/3 arc as seen from the direction facing the rake face 3 in the insert center line C direction. In this embodiment, the main cutting edge 5 and the corner edge 6 are positioned on one plane perpendicular to the insert center line C in each of the front and back polygonal surfaces.

The rake face 3 formed on the front and back polygonal surfaces is such that the outer peripheral portions along the main cutting edge 5 and the corner edge 6 are spaced apart from the main cutting edge 5 and the corner edge 6 toward the inside of the polygonal face. The positive rake surface 3a is inclined so as to recede in the thickness direction toward the opposite polygonal surface. That is, the rake face 3 is a positive rake face that retreats toward the center in the thickness direction of the insert body 1 as it is separated from the main cutting edge 5 and the corner edge 6.
The periphery of the opening of the attachment hole 2 at the center of the polygonal surface is a flat constraining surface 3b perpendicular to the insert center line C.

  In this embodiment, the positive rake face 3a connected to the main cutting edge 5 of the rake face 3 extends over the entire length of the main cutting edge 5 used for cutting when the insert body 1 is attached to an insert mounting seat 16 described later. And a constant rake angle in the axial direction. That is, as shown in FIGS. 2, 5, and 10, it passes through the protruding end (the most outwardly protruding portion) of the one end portion 5 a that forms the convex curve shape of the main cutting edge 5 when viewed in the direction of the insert center line C. In a plane P parallel to the axis O of the end mill body 11 and including the insert center line C, and a cross section of each plane parallel to the plane P, the inclination angle of the positive rake face 3a with respect to the plane perpendicular to the insert center line C (FIG. 5). (Θ) in (a) to (e) is made constant. The inclination angle θ is set to 15 ° in this embodiment, and the axial rake angle is set to 5 ° when attached to the insert mounting seat 16 of the end mill body 11.

Accordingly, the positive rake face 3a has a certain inclination angle with respect to one main cutting edge 5 as it goes from the main cutting edge 5 to the inside of the polygonal surface on which the rake face 3 is formed. It is formed in one flat shape that inclines toward the square surface. Here, when the workpiece is cut by the main cutting edge 5 connected to the positive rake face 3a without the positive rake face 3a being curved, the above-mentioned one planar shape is used to flow the generated chips in a certain direction. The flat state of the degree to get.
Further, the positive rake face 3a is opposed to the center side of the insert body 1, specifically, between the positive rake face 3a and the restraining face 3b as it is steeper than the positive rake face 3a toward the inside of the polygonal face. A step surface 3c that is inclined toward the polygonal surface on the side is formed.

In this way, the positive rake face 3a of the main cutting edge 5 is formed in a flat shape, and the main cutting edge 5 has an uneven curve shape when viewed from the direction facing the rake face 3 along the insert center line C direction. As a result of the formation, the main cutting edge 5 has an end portion 5a having a convex curve shape in the side view as viewed from the direction perpendicular to the insert center line C as shown in FIGS. The protrusion in the center line C direction has a convex curve shape that protrudes most in the insert thickness direction in which the protrusion protrudes most, and the other end portion 5b that forms the concave curve shape gradually increases in the insert thickness direction as the distance from the one end portion 5a increases. A concave curve shape is formed so as to be recessed.
In the present embodiment, the main cutting edge 5 has one end portion 5a having a convex curve shape and the other end portion 5b having a concave curve shape, so that the entire region is formed in a curved shape. As shown in FIGS. 3 and 4, the highest portion of the cutting blade in the thickness direction is formed not on the corner blade 6 but on the main cutting blade 5.

  The positive rake face 3a connected to the corner blade 6 has a cross section parallel to the insert center line C along the normal line of the corner blade 6 when viewed along the direction of the insert center line C, as shown in FIG. The inclination angle with respect to a plane perpendicular to the insert center line C is made constant, and this inclination angle is also set to 15 ° equal to the inclination angle of the positive rake face 3a connected to the main cutting edge 5. Therefore, the positive rake face 3a of the corner blade 6 is formed in a concave frustoconical surface shape that forms a fan shape as viewed in the direction of the insert center line C and is concave along the corner blade 6, and is adjacent to the corner blade 6 therebetween. The positive rake face 3 a of the main cutting edge 5 is smoothly continuous via the positive rake face 3 a of the corner edge 6.

A protrusion 3d is formed around the opening of the mounting hole 2 on the constraining surface 3b having a polygonal surface on the front and back sides. The protrusions 3d have a substantially rectangular shape when viewed in the direction of the insert center line C, and are formed one by one on a straight line connecting the insert center line C and the corner blade 6 in each restraint surface 3b. Three protrusions 3d are formed at equal intervals in the circumferential direction with respect to 3b, and the protruding end surfaces of the three protrusions 3d in the direction of the insert center line C in this one restraint surface 3b are located on one plane perpendicular to the insert center line C. doing.
The main cutting edge 5 and the corner edge 6 may be formed with lands or round honing. Moreover, in each figure, although the boundary line is shown for the positive rake face 3a, the flank 4 etc. for description, a boundary line does not necessarily appear.

Further, on the three side surfaces arranged around the triangular surfaces on the front and back sides of the insert main body 1, as shown in FIG. 1, a concave portion 7 recessed inward is formed in the center portion in the thickness direction of the insert main body 1. It is formed over the entire circumference. The bottom surface 7b facing the outer periphery of the insert main body 1 of each of the concave portions 7 on the three side surfaces is a hexagonal shape in a cross section perpendicular to the insert center line C, and the six surfaces connected to each side of the eccentric hexagon are Each of them is parallel to the insert center line C and has a flat shape perpendicular to the pair of polygonal constraining surfaces 3b.
In addition, the width of the recess 7 in the direction of the insert center line C is set to 1/3 or more of the thickness of the insert body 1 itself, and the flank 4 of the main cutting edge 5 and the corner blade 6 has the above-mentioned thickness on each side. It is formed in the part which becomes convex on the outer side of the insert main body 1 with respect to the recessed part 7 on both outer sides in the vertical direction.

  Furthermore, in the cutting insert of this embodiment, as shown in FIG. 12, the main cutting edge 5 and the corner edge 6 used at the time of cutting rotate the blade tip replaceable end mill counterclockwise as viewed from the front side. A right-handed cutting insert configured to form a right blade, and when viewed from the direction facing the polygonal surface on which the rake face 3 of the main cutting edge 5 and the corner edge 6 is formed, One end portion 6a of the corner blade 6 connected to the one end portion 5a of the main cutting blade 5 is positioned at one end portion 5a of the main cutting blade 5 positioned on the clockwise direction side of the circumference, and is positioned on the counterclockwise direction side. The other end portion 5b of the other corner blade 6 is connected to the other end portion 5b of the main cutting edge 5 to be connected. The other polygonal surface as viewed from one polygonal surface side is slightly twisted toward the clockwise direction as shown in FIG.

  Further, the clearance angle β6 of the corner blade 6, that is, the angle formed by the flank 4 connected to the corner blade 6 with respect to a straight line parallel to the insert center line C in the cross section along the insert center line C is shown in FIG. ) To (c) so as to increase toward the negative angle side from one end portion 6a of the corner blade 6 connected to the one end portion 5a of the main cutting blade 5 toward the other end portion 6b of the corner blade 6. Has been. That is, the flank 4 from the other end portion 6b toward the one end portion 6a is recessed so as to recede more greatly on the inner side of the insert main body 1 as it is separated from the corner blade 6 in the thickness direction in the cross section. Note that the clearance angle β6 of the corner blade 6 in the present embodiment is a positive angle at the one end portion 6a of the corner blade 6 but is 20 ° or less and 0 ° at the other end portion 6b. The angle is gradually increased toward the negative angle side.

  The main cutting edge 5 connected to the corner blade 6 is connected to the one end portion 6a of the corner blade 6 as shown in FIG. 2 when viewed from the direction facing the rake face 3 when viewed in the direction of the insert center line C. The one end portion 5a of the cutting blade 5 has a convex curve shape having a radius of curvature larger than the convex curve formed by the corner blade 6, and the other end portion 5b of the main cutting blade 5 has a concave curve shape. That is, one end portion 5a of the main cutting edge 5 is a convex curved cutting edge, and the other end portion 5b of the main cutting edge 5 is a concave curved cutting edge. Here, the concavo-convex curve formed by these main cutting edges 5 is such that the radius of curvature of the concave curve formed by the other end portion 5b is larger than the radius of curvature of the convex curve formed by the one end portion 5a. The length of the convex curve formed by 5a is set to be longer than the length of the concave curve formed by the other end 5b.

  Accordingly, one main cutting edge 5 formed on one side ridge extending between two corners adjacent to each other in the circumferential direction of the polygonal surface is scooped. When viewed from the direction facing the surface 3, one of the two corners (the first corner. In the present embodiment that is a right-handed cutting insert, the one side ridge is clockwise. One end portion (first end portion) 5a of the main cutting edge 5 connected to the direction side corner portion is formed in a convex curve shape, and the other corner portion (second corner portion. The other end part (second end part) 5b of the main cutting edge 5 connected to the counterclockwise direction corner of the side ridge part has a concave curve shape.

  Since the insert body 1 has a rotationally symmetrical shape around the insert center line C by a predetermined angle (120 ° in this embodiment), in the cutting insert of this embodiment that is right-handed, the direction facing the rake face 3 When viewed from the above, the one corner portion with respect to one main cutting edge 5 is relative to the other main cutting edge 5 adjacent to the one main cutting edge 5 in the clockwise direction via the one corner portion. Is the other corner.

  Further, since the insert body 1 has a reverse inversion shape with respect to three imaginary straight lines passing through the centers of the side surfaces, the two flank surfaces 4 formed on one side surface of the insert body 1 and many front and back surfaces. Each of the two main cutting edges 5 formed at each of the intersecting ridge lines with the rake face 3 of the rectangular surface is also in an inverted symmetrical shape with respect to the polygonal surfaces on the front and back sides. That is, one polygonal surface of the pair of front and back polygonal surfaces of the insert body 1 is a first polygonal surface, the other polygonal surface is a second polygonal surface, and one side surface of the insert body 1 is The first flank 4 is defined as a first flank 4 which is the first flank 4 of the two flank 4 formed on the first side. The main cutting edge 5 formed at the crossing ridge line portion with the rake face (first rake face) 3 of the first polygonal surface is defined as the first main cutting edge 5, and the second multiple of the first side face. The flank 4 on the side of the square surface is used as a second flank 4, and the second flank 4 is formed at the crossing ridge line portion of the second polygonal rake face (second rake face) 3. When the main cutting edge 5 is the second main cutting edge 5, the insert body 1 is rotated 180 ° in the circumferential direction around the virtual straight line on the first side surface and reversed. The first main cutting edge 5 coincides with the second main cutting edge at the original position before reversing, and the second main cutting edge is at the original position before reversing. Therefore, the first and second main cutting edges 5 have a reverse symmetrical shape with respect to the first and second polygonal surfaces on the front and back sides.

  Accordingly, in the two main cutting edges (first and second main cutting edges) 5 formed on the both sides in the insert thickness direction on one side face (first side face) of the insert body 1, The other end portion (second end portion) 5b of the other main cutting edge 5 is located on the opposite side of the insert thickness direction of one end portion (first end portion) 5a of the main cutting edge 5a. One end portion (first end portion) 5a of the other main cutting blade 5 is positioned on the opposite side of the other end portion (second end portion) 5b of the blade 5 in the insert thickness direction. Moreover, also about the corner | angular part of the polygonal surface in which the corner blade 6 continuing to these two main cutting blades 5 is formed, one polygonal surface (first polygonal surface) and the other polygonal surface (second The other corner (second corner) is positioned on the opposite side of the insert thickness direction of one corner (first corner) on the polygonal surface.

  In the present embodiment, the convex curve formed by one end portion 5a of the main cutting edge 5 and the concave curve formed by the other end portion 5b are in contact with each other at the contact point 5c. One end portion 5a of the main cutting edge 5 and one end portion 6a of the corner blade 6 connected thereto, and the other end portion 5b of the main cutting blade 5 and the other end portion 6b of another corner blade 6 connected thereto are also in contact with each other. Yes. Therefore, the contact 5c is located on the other corner side from the midpoint of the side ridge part of the polygonal surface where the main cutting edge 5 is formed. In the present embodiment, a convex curve is formed from a contact point between the one end portion 5a of the main cutting edge 5 and one end portion 6a of the corner blade 6 connected thereto to a contact point 5c between the one end portion 5a and the other end portion 5b of the main cutting edge 5. A range of one end portion 5a of the main cutting edge 5 which is a cutting edge, from this contact point 5c to a contact point between the other end portion 5b of the main cutting edge 5 and the other end portion 6b of another corner blade 6 connected thereto. It is set as the range of the other end part 5b of the main cutting edge 5 made into the concave curvilinear cutting edge. Therefore, in this embodiment, the main cutting edge 5 and the corner edge 6 formed at the side ridges and corners of the polygonal surfaces on the front and back sides, which are the rake face 3, are drawn in a smoothly continuous concave-convex curve. Will do.

  Further, the clearance angle β5 of the main cutting edge 5 is larger at the one end portion 5a of the main cutting edge 5 than at the other end portion 5b of the main cutting edge 5, as shown in FIGS. It is enlarged toward the regular angle side. In other words, at the other end portion 5b of the main cutting edge 5, the clearance angle β5 is larger on the negative angle side than the one end portion 5a. Here, in this embodiment, the clearance angle β5 of the main cutting edge 5 is a cross section by a plane including the insert center line C and a straight line passing through the center of the side surface of the insert body 1 (FIG. 2). DD cross section) and a cross section parallel thereto, the flank 4 connected to the main cutting edge 5 is at an angle formed with respect to a straight line passing through the main cutting edge 5 and parallel to the insert center line C. The flank 4 is the center of the insert. The case parallel to the line C is 0 °. Further, when the flank 4 is moved away from the main cutting edge 5, the case where the flank 4 recedes to the inside of the insert body 1 with respect to a straight line parallel to the insert center line C becomes a regular angle, and conversely, The case where it protrudes becomes a negative angle.

  In the present embodiment, the clearance angle β5 of the main cutting edge 5 is such that the one end portion 5a of the main cutting edge 5 is in contact with the corner blade 6 connected to the one end portion 5a (the main cutting edge 5 and the corner blade). 6) and a positive angle equal to 20 ° or less equal to the clearance angle β6 at one end portion 6a of the corner blade 6, and toward the other end portion 5b side of the main cutting edge 5, on the corner blade 6 side of the one end portion 5a. The constant clearance angle β5 remains unchanged, and the portion of the one end portion 5a toward the contact point 5c opposite to the corner blade 6 gradually increases toward the negative angle side toward the contact point 5c, that is, toward the other end portion 5b side. Has been. In other words, the clearance angle β5 of the main cutting edge 5 is in a portion adjacent to the contact 5c in the one end 5a, that is, on the other end 5b side of the one end 5a of the main cutting edge 5, as the distance from the contact 5c increases. In other words, the distance from the other end 5b increases toward the regular angle side.

  Further, the clearance angle β5 of the main cutting edge 5 at the one end portion 5a that is increased toward the negative angle side toward the other end portion 5b in this way is the contact point 5c between the one end portion 5a and the other end portion 5b of the main cutting edge 5. In this embodiment, the negative is 0 °, and the other end 5b is kept constant at the 0 ° clearance angle β5. Therefore, in this embodiment, the contact between one end portion 5a of the main cutting edge 5 and one end portion 6a of the corner blade 6 connected thereto, the other end portion 5b of the main cutting edge 5 and other corner blades 6 connected thereto. The contact angles between the end 6b and the contact 5c between the one end 5a and the other end 5b of the main cutting edge 5 are equal to each other at the clearance angles β5 and β6. The flank 4 of 6 has an uneven curved surface that is smoothly continuous over the entire circumference of the insert body 1.

  In this way, the flank 4 connected to the main cutting edge 5 and the corner blade 6 is formed into an uneven curved surface, whereby the flank 4 on the front and back polygonal surfaces (regular triangle surface) side on the side surface of the insert body 1 is formed. The concave portion 7 formed in the shape of the concave portion 7 is formed in a polygonal line shape in which a cross section perpendicular to the insert center line C of the bottom surface 7b forms a convex V shape extending in a direction in which a portion along the main cutting edge 5 intersects an obtuse angle. In addition, the portions along the one end portion 5a and the other end portion 5b of the pair of main cutting blades 5 adjacent to each other via the corner blades 6 in the circumferential direction have a bent line shape that forms a convex V shape extending in a direction intersecting at an acute angle. It is formed in a partial hexagonal shape.

  A description will be given of a blade edge replaceable end mill which is a blade edge replaceable cutting tool according to an embodiment to which the thus configured cutting insert is detachably attached. FIG. 7 is a perspective view of the tip end portion of the end mill body showing a blade edge replaceable end mill which is an embodiment of the blade edge replaceable cutting tool of the present invention to which the cutting insert of the embodiment shown in FIG. 1 is attached. FIG. 8 is a blade edge shown in FIG. FIG. 9 is a perspective view of the blade tip replaceable end mill, FIG. 10 is a plan view of the blade tip replaceable end mill, and FIG. 11 is the blade tip of the end mill body with the cutting insert removed in the replaceable end mill. FIG. 12 is an enlarged front view of the blade end replaceable end mill.

  In the edge-replaceable end mill, an end mill body 11 as a tool body has a substantially cylindrical shape with an axis O as a center. The rear end side (upper side in FIGS. 10 and 11) of the end mill body 11 is a cylindrical shank portion 12, and is closer to the front end side (lower side in FIGS. 10 and 11) than the shank portion 12. The blade portion 14 to which the cutting insert is attached is formed through the neck portion 13. In such a blade-tip-exchangeable end mill, the shank portion 12 is gripped by the main spindle of the machine tool and rotated in the end mill rotation direction T around the axis O, and is usually fed in a direction perpendicular to the axis O, and the blade 14 The workpiece is cut by the cutting insert of the first embodiment attached to the workpiece.

  A plurality of (two in this embodiment) tip pockets 15 are formed in the blade portion 14 so as to open to the outer periphery of the tip end portion of the end mill body 11, and the end mill rotation direction T side of these tip pockets 15 is arranged on the blade portion 14. Insert mounting seats 16 to which cutting inserts are attached are respectively formed at the front end portions of the facing wall surfaces. The end mill body 11 has a coolant hole 11a drilled along the axis O from the rear end surface of the shank portion 12 toward the front end side. The coolant hole 11a branches into a plurality at the blade portion 14, Opened toward the insert mounting seat 16 on the wall surface of each chip pocket 15 facing the rear side in the end mill rotation direction T.

  The insert mounting seat 16 has a flat bottom surface 16a that is recessed from the wall surface of the tip pocket 15 toward the rear side in the end mill rotation direction T and faces the end mill rotation direction T, and extends from the bottom surface 16a toward the end mill rotation direction T. 11 is provided with a wall surface 16b facing the inner peripheral side of the tip and a wall surface 16c facing the outer peripheral side of the tip, and is a recess that opens to the distal end surface and the outer peripheral surface of the end mill body 11 in the blade portion 14. The bottom surface 16a has a size and shape that is slightly smaller than the constraining surface 3b at the center portion of the rake face 3 of the insert body 1. A screw hole 16d is formed in the center portion of the bottom surface 16a perpendicular to the bottom surface 16a, and the wall surface 16b. , 16c is formed with a protrusion 17 projecting inward of the insert mounting seat 16 so as to extend in the circumferential direction of the bottom surface 16a.

  Of these, two protrusions 17 are formed on the wall surface 16c facing the outer peripheral side of the tip end of the end mill main body 11 so as to extend from the front end side of the end mill main body toward the rear end side. The protruding end surface 17a inside the insert mounting seat 16 of the strip portion 17 corresponds to the bottom surface 7b of the concave portion 7 in the portion along the main cutting edge 5 of the insert body 1 in a cross section orthogonal to the center line of the screw hole 16d. As shown in FIG. 8, it is a plane that is substantially perpendicular to the bottom surface 16a.

  Further, one protrusion 17 is formed on the wall 16b facing the inner peripheral end of the end mill body 11, and the protrusion 17a of the protrusion 17 is a cross section that is also orthogonal to the center line of the screw hole 16d. 1a and 5b, one end 5a and the other end 5b of the pair of main cutting blades 5 adjacent to each other in the circumferential direction of the insert body 1 through the corner blades 6 together with the protrusion end surface 17a of the protrusion 17 on the rear end side of the wall surface 16c. The bottom surfaces 7b of the recesses 7 in the section along the line are formed so as to form a concave V-shaped broken line extending in a direction intersecting at an angle equal to the acute angle of the convex V-shaped in a cross section orthogonal to the insert center line C. Yes. An escape portion 16e is formed between the protruding end surface 17a and the bottom surface 16a of each protruding portion 17 and between adjacent protruding portions 17.

Further, the height from the bottom surface 16a of the projecting end surface 17a in the center line direction of the screw hole 16d is within the range of the width in the thickness direction of the bottom surface 7b located on the same side from the restraining surface 3b of the insert body 1. ing.
Further, in the end mill main body 11 of this blade edge replaceable end mill, three recesses 16f are formed at equal intervals in the circumferential direction as shown in FIG. 8 around the screw hole 16d in the bottom surface 16a of the insert mounting seat 16. Yes. The recess 16f corresponds to the protrusion 3d formed on the polygonal constraining surface 3b on the front and back of the insert body 1, and the protrusion 3d is fitted into the recess 16f.

  In such an insert mounting seat 16, the cutting insert uses the rake face 3 of one polygonal surface on which the main cutting edge 5 used for cutting among the polygonal surfaces on the front and back sides of the insert body 1 is formed in the end mill rotation direction. The main cutting edge 5 is projected toward the tip end side of the end mill main body 11, and one end 5a of the main cutting edge 5 is positioned on the inner peripheral side of the end mill main body 11 and the other end 5b is set on the outer peripheral side. The other polygonal surface opposite to the one polygonal surface is used as a seating surface, and the restraint surface 3b at the center thereof is brought into close contact with the bottom surface 16a to be seated.

  Further, the insert in which the flank 4 of the other main cutting edge 5 on the opposite side of the corner blade 6 connected to the one end portion 5a of the main cutting edge 5 used for cutting is formed with the insert body 1 seated in this manner. The side surface of the main body 1 is opposed to a wall surface 16b facing the tip inner peripheral side of the end mill main body 11 of the insert mounting seat 16, and the bottom surface 7b of the recess 7 formed on this side surface is a ridge portion 17 formed on the wall surface 16b. It is made to contact | abut to the protrusion end surface 17a.

  On the other hand, the side surface of the insert main body 1 on which the flank 4 of the remaining main cutting edge 5 adjacent to the main cutting edge 5 used for the above-mentioned cutting through the corner edge 6 on the one end 5a side is formed as an insert mounting seat. A pair of bottom surfaces 7b of the recesses 7 formed on the side surfaces are brought into contact with the protruding end surfaces 17a of the ridges 17 formed on the wall surface 16c. It is done.

  And by screwing the clamp screw 18 inserted through the mounting hole 2 of the insert body 1 into the screw hole 16d, the cutting insert is pressed against the bottom surface 16a by the polygonal surface of the constraining surface 3b. The bottom surface 7b on the polygonal surface side, which is the seating surface of the concave portion 7 on the two side surfaces facing the wall surfaces 16b, 16c, is pressed against the projecting end surface 17a of the projecting ridge portion 17 in contact as described above. It is fixed and attached to the mounting seat 16.

  The main cutting edge 5 used for the cutting of the cutting insert attached in this way protrudes toward the distal end side of the end mill main body 11 at one end portion 5a having a convex curve shape as it goes from the inner peripheral side of the end mill main body 11 to the outer peripheral side. Later, toward the rear end side, the other end portion 5b having a concave curve shape is arranged so as to gradually extend toward the rear end side of the end mill body 11, and the substantially central portion of the one end portion 5a protrudes most toward the front end side of the end mill body. It is said. In addition, the main cutting edge 5 has an axis line on the side ridge portion of the polygonal surface on which the main cutting edge 5 is formed so that the whole of the one end portion 5a is located on the tip end side of the end mill body 11 with respect to the other end portion 5b. With respect to the plane orthogonal to O, the end mill body 11 is slightly tilted toward the rear end side toward the outer peripheral side of the end mill body 11.

  Furthermore, the cutting insert is attached with being slightly tilted so that the insert center line C is directed toward the rear end side in the axis O direction of the end mill body 11 as the insert center line C moves toward the rear side in the end mill rotation direction T as shown in FIG. Thus, a negative axial rake angle is set for the main cutting edge 5 used for cutting. However, since the rake face 3 connected to the main cutting edge 5 is the positive rake face 3a as described above, the actual axial rake angle of the main cutting edge 5 does not become too large on the negative angle side. In addition, by giving a negative axial rake angle in this way, the rake face 3 of the other polygonal surface which is the seating surface of the insert body 1 is around the insert center line C with respect to the one polygonal surface. Combined with the twisted arrangement, the end mill body 11 is positioned on the rear end side of the main cutting edge 5 used for cutting.

  Further, the main cutting edge 5 used for this cutting is shown in FIG. 12 when viewed from the front end side of the end mill body 11 in the direction of the axis O, rather than a straight line parallel to the main cutting edge 5 and intersecting the axis O. The main cutting edge 5 is provided with a negative radial rake angle by being arranged so as to be positioned on the side of the rotation direction T, and so-called centering. In addition, by giving a negative radial rake angle to the main cutting edge 5 used for cutting in this way, other corner blades 6 connected to the outer peripheral side of the end mill body 11 at the other end 5b of the main cutting edge 5 are The blade 14 is projected to the outermost periphery of the end mill body 11, and as shown in FIG. 8, the insert body is located on the inner peripheral side with respect to the rotation trajectory around the axis O of the tip of the other outer periphery of the corner blade 6 as shown in FIG. The rake face 3 of the other polygonal face of 1 is located.

  Next, the operation of the cutting insert having the above-described configuration and the blade edge replaceable end mill will be described. When the main cutting edge 5 of the cutting insert is viewed from the direction facing the rake face 3, the one end portion 5 a disposed on the inner peripheral side of the end mill body 11 has a convex curve shape having a larger radius of curvature than the corner edge 6. At the same time, the other end portion 5b disposed on the outer peripheral side of the end mill body 11 has a concave curve shape, and the main cutting edge 5 is moved from the protruding end of the one end portion 5a toward the other end portion 5b. 11 By attaching the insert main body 1 so as to extend to the rear end side, the cutting angle of the main cutting edge 5 at the time of high feed processing in which the end mill main body 11 is fed in a direction orthogonal to the axis O to perform cutting processing is the above-mentioned protrusion From the end mill body 11 toward the outer periphery of the end mill 11 gradually increases at the one end 5a, but gradually decreases at the other end 5b.

FIG. 13 is an explanation of the operation when performing high-feed machining, in which (a) is a diagram showing a cross-section of chips generated by the blade-tip replaceable end mill shown in FIG. 7, and (b) a blade edge with a conventional cutting insert attached. It is a figure which shows the cross section of the chip | tip produced | generated by a replaceable end mill.
What is indicated by hatching in FIG. 13 (a) is a cross section of the chips generated by the main cutting edge 5 during such high feed processing, and what is indicated by hatching in FIG. This is a cross-section of chips when the cutting angle of the main cutting edge is increased toward the outer peripheral side of the end mill body as in the case of an end mill with a cutting edge described in Reference 2, and the feed rate per blade. The fz and the cut depth ap are equal to each other. Of these, as shown in FIG. 13B, when the cutting angle of the main cutting edge 5 gradually increases toward the outer peripheral side, the thickness of the chips also increases toward the outer peripheral side, and the outermost cutting boundary is formed. Since the portion has the maximum thickness t, the cutting insert may cause abnormal damage such as chipping or chipping at the incision boundary. For example, the feed amount per blade must be reduced.

  However, when the cutting angle of the main cutting edge 5 becomes smaller on the outer peripheral side of the end mill body 11 as described above, the thickness of the chips is once increased toward the outer peripheral side as shown in FIG. After becoming thicker, it becomes thinner and becomes the maximum thickness t at the substantially central portion of the outer peripheral side portion of the end mill body 11 from the protruding end of the main cutting edge 5, and this maximum thickness t itself becomes thinner. For this reason, according to the cutting insert and the cutting edge exchangeable cutting tool (end mill) configured as described above, the cutting load acting on the main cutting edge 5 during high feed processing is reduced, and the main cutting edge particularly at the cutting boundary portion. On the other hand, the cutting edge strength of the main cutting edge 5 at the portion where the chips have the maximum thickness t as described above can be ensured. Therefore, it is possible to reliably prevent abnormal damage at the cutting boundary portion of the main cutting edge 5 and to further increase the feed amount per blade and achieve more efficient high feed processing.

  Further, the insert body 1 has a symmetrical shape with respect to the imaginary straight line, and the rake surfaces 3 are formed on the polygonal surfaces of the front and back surfaces, respectively, and the rake surfaces 3 and the relief formed on one side surface are formed. One main cutting edge 5 is formed at each of the intersecting ridge lines with the surface 4, and these main cutting edges 5 have an inverted symmetrical shape with respect to the polygonal surfaces on the front and back sides. In the front and back polygonal surfaces on which the side surfaces are arranged, the main cutting edge 5 on the other polygonal surface side is opposite to the front and back sides of the one end portion 5a forming the convex curve shape of the main cutting edge 5 on one polygonal surface side. The other end portion 5b having a concave curve shape is disposed.

  Therefore, in the polygonal surface opposite to the polygonal surface on which the main cutting edge 5 used for cutting is located, the tip of the end mill body 11 is placed on the opposite side of the one end portion 5a of the main cutting edge 5 in the insert thickness direction. Of the main cutting edge 5 directed to the side, the other end portion 5b that is recessed in the shape of a concave curve is positioned, so that a sufficient escape amount can be ensured. For this reason, it is not necessary to set the axial rake angle of the main cutting edge 5 used for cutting larger than necessary to the negative angle side, and sharpness is sharpened to reduce cutting resistance and improve chip discharge performance. Can do.

  Further, in addition to feeding the end mill body 11 in a direction perpendicular to the axis O as in the above-described high feed machining, the end mill body 11 is slightly fed to the front end side in the axis O direction to dig up the work material. Even in the case of performing such ramping, the main cutting edge 5 used for cutting is cut into the work material entirely from one end portion 5a, whereas a large escape amount is provided on the opposite side of the one end portion 5a. Therefore, interference between the insert body 1 and the work material can be prevented. Therefore, the amount of digging and the ramping angle during the ramping process can be increased, and the processing efficiency can be improved.

  Moreover, in this embodiment, the curvature radius of the other end part 5b which makes a concave curve shape is made larger than the curvature radius of the one end part 5a which makes a convex curve shape among the main cutting blades 5 which make an uneven curve shape in this way. Thus, as shown in FIG. 13 (a), the position where the chip has the maximum thickness t is set at the one end 5a and the other end 5b at the outer peripheral side of the end mill body 11 from the protruding end of the main cutting edge 5. It can be set as the position close | similar to the center part which touches. For this reason, compared with the case where the chip has the maximum thickness at a position close to the portion connected to the adjacent corner blade 6 of the one end portion 5a or the other end portion 5b of the main cutting edge 5, the main cutting edge has a maximum thickness t. It is easy to ensure the strength of the cutting edge 5, and this can also prevent chipping and chipping.

  Furthermore, in the present embodiment, the convex curve formed by one end 5a of the main cutting edge 5 and the concave curve formed by the other end 5b are in contact with each other at the contact 5c, that is, the main cutting edge 5 is a straight line. It is made into the continuous uneven | corrugated curve which does not have a part. Accordingly, the amount of variation in the thickness of the chips on the inner and outer peripheries of the end mill main body 11 also becomes continuous and smooth, avoiding the concentration of the cutting load on a specific part of the main cutting edge 5 and further burdening the main cutting edge 5. Can be reduced. However, the convex curve formed by the one end portion 5a and the concave curve formed by the other end portion 5b may be continued to the intermediate portion via a tangent line. In addition, since the convex curve formed by the one end portion 5a of the main cutting edge 5 is longer than the concave curve formed by the other end portion 5b, the amount of digging is reduced by the convex curved one end portion 5a during the ramping process described above. It is also possible to secure a larger size and perform more efficient cutting.

Moreover, in the said cutting insert, the positive rake face 3a continued to the main cutting edge 5 is formed so that one flat shape may be formed, and the main cutting edge 5 is seen from the direction facing the rake face 3 as described above. Even if it is made into the uneven | corrugated curved shape, a chip | tip can be produced | generated smoothly and discharged | emitted. That is, when the main cutting edge 5 has a concave-convex curved shape as described above, for example, the inclination toward the normal direction of the main cutting edge 5 like the positive rake face 3a connected to the corner edge 6 of the present embodiment. If the angle is constant, the chip is compressed in the width direction at one end 5a having a convex curve shape, and the chip is stretched at the other end 5b having a concave curve shape. Therefore, the load at the time of chip generation is large, and there is a possibility that the cutting resistance increases and wear due to excessive cutting heat may occur. However, the positive rake face 3a of the main cutting edge 5 is a flat surface as in this embodiment. By forming it in the shape of a chip, it is possible to generate and discharge the chip smoothly by keeping the generation direction of the chip constant along the one planar portion.
In this way, since the generation and discharge of chips are smooth, cutting resistance can be reduced, and it is possible to extend the life by suppressing the temperature rise of the chips and to prevent abnormal damage to the cutting blades. it can.

  Further, in the present embodiment, between the positive rake face 3a and the constraining face 3b, the positive rake face 3a is steeper than the positive rake face 3a and is inclined toward the opposite polygon face as it goes toward the inside of the polygon face. Since the step surface 3c is formed, chip separation from the positive rake surface 3a is good, and the cutting resistance can be further reduced.

  Further, at the time of ramping, the main cutting edge 5 is located at one end portion 5a of the end mill body 11 on the inner peripheral side with respect to the protruding end with respect to the outer peripheral side of the end mill body 11 with respect to the protruding end of the main cutting edge 5. Is given a negative radial rake angle, it is difficult to secure a clearance between the machining surface of the work material formed by the main cutting edge 5 and the flank 4, and the flank 4 rubs against the machining surface. However, in the cutting insert configured as described above, the clearance angle β5 of the main cutting edge 5 may be different at the one end portion 5a. Such an interference can be avoided because it is made larger on the positive angle side than the end 5b.

  For this reason, even if the axial rake angle of the main cutting edge 5 used for cutting is not increased more than necessary to the negative angle side, it is possible to prevent wear due to abrasion of the flank 4 and increase in cutting resistance. The chips generated by the main cutting edge 5 can be smoothly discharged and processed, and the sharpness of the main cutting edge 5 is sharpened to reduce cutting resistance and promote more efficient ramping. it can. In particular, in this embodiment, since the positive rake face 3a is formed on the rake face 3 connected to the main cutting edge 5, it is possible to further improve the sharpness.

  Further, by increasing the clearance angle β5 to the positive angle side at the one end portion 5a of the main cutting edge 5 in this way, when the feed amount per one blade is further increased as described above in the high feed processing, the main cutting edge 5 Even when the work material is greatly cut even at the inner peripheral side of the end mill body 11 from the protruding end, it is possible to prevent interference between the work material and the flank 4. On the other hand, at the other end portion 5b located on the outer peripheral side of the end mill body 11 of the main cutting edge 5, the clearance angle β5 is relatively increased to the negative angle side, and the cutting angle of the main cutting edge 5 is also increased. Abnormal damage of the main cutting edge 5 at the boundary can be further reliably prevented.

  Furthermore, in the present embodiment, the clearance angle β5 of the main cutting edge 5 is gradually increased toward the positive angle side as it is separated from the other end portion 5b on the other end portion 5b side of the one end portion 5a. In other words, the clearance angle β5 gradually increases toward the positive angle side as the distance from the contact point 5c increases in the portion adjacent to the contact point 5c of the one end portion 5a. A step or the like does not occur on the flank 4 as in the case where the clearance angle β5 changes discontinuously, and it is possible to perform stable cutting by preventing a defect from such a step.

  In addition, in the present embodiment, the clearance angle β5 of the main cutting edge 5 on the side opposite to the other end 5b of the one end 5a, that is, on the corner blade 6 side (one corner side) connected to the one end 5a of the one end 5a. Can be prevented, and the cutting angle of the main cutting edge 5 is reduced by reducing the clearance angle β5 more than necessary and the strength of the cutting edge is impaired, thereby preventing the chipping and chipping from being easily caused. . In the present embodiment, the clearance angle β5 is constant at the other end portion 5b of the main cutting edge 5 and does not become excessively large on the negative angle side. Interference with the material can also be prevented.

  Note that the clearance angle β5 at the one end portion 5a of the main cutting edge 5 is desirably a positive angle of 20 ° or less as in this embodiment, and if larger than this, the one end portion is as described above. The blade angle of the main cutting edge 5 in 5a becomes small, and damage such as chipping and chipping is likely to occur. In addition, the clearance angle β5 of the main cutting edge 5 at the other end 5b is preferably 0 ° or more as in the present embodiment, and if larger than this, the main cutting edge 5 at the other end 5b. Since the flank 4 may interfere with the work material, the axial rake angle must be increased.

  However, if the clearance angle β5 is desirably within these ranges, the entire one end portion 5a of the main cutting edge 5 may be gradually increased toward the positive angle side as it is separated from the other end portion 5b. Alternatively, the entire other end portion 5b may be gradually increased toward the negative angle side as it is separated from the one end portion 5a.

  Further, in the present embodiment, the corner of the polygonal surface that is the rake face 3 of the insert body 1 has a convex curve shape when viewed from the direction facing the rake face 3, and the one end 5 a of the main cutting edge 5. Consecutive corner blades 6 are formed, and the clearance angle β6 of the corner blades 6 is from the one end portion 6a of the corner blade 6 connected to the one end portion 5a of the main cutting blade 5 to the other end of the corner blade 6 opposite thereto. It is enlarged toward the negative angle side toward the part 6b. For this reason, at the one end portion 6a of the corner blade 6, similarly to the one end portion 5a of the main cutting edge 5, the interference with the work material is prevented and the other end portion 5b of the main cutting edge 5 adjacent via the corner blade 6 is prevented. At the other end portion 6b of the corner blade 6 that is connected to, the blade angle can be increased to prevent breakage and the like.

  In particular, in this embodiment, the contact between one end 5a of the main cutting edge 5 and one end 6a of the corner blade 6 and the contact between the other end 5b of the main cutting edge 5 and the other end 6b of the corner blade 6 are provided. The relief angles β5 and β6 are equal to each other, and the relief surface 4 forms an uneven curved surface that is smoothly continuous over the entire circumference of the insert body 1 as described above. For this reason, it is also possible to prevent the clearance surface 4 from being stepped as in the case where the clearance angle β5 and the clearance angle β6 change discontinuously at these contact points. Occurrence can be prevented.

  On the other hand, in the cutting insert of the first embodiment, the insert body 1 has an equilateral triangular plate shape, and the main cutting edge 5 is formed at each side ridge portion of the polygonal surfaces on the front and back sides forming the equilateral triangle shape. However, the polygonal surfaces on the front and back sides are arranged to be slightly twisted around the insert center line C passing through the center thereof, and the insert body 1 is formed in a symmetrical shape with respect to the front and back polygonal surfaces. Yes.

  Then, the cutting edge of such a cutting insert is inclined so that the insert mounting seat 16 of the end mill body 11 is given a relatively small cutting angle to the main cutting edge 5 used for cutting. 5 is attached so that a negative axial rake angle and a radial rake angle are given, and the rake face 3 of the other polygonal surface opposite to the polygonal surface on which the main cutting edge 5 is formed is The main cutting edge 5 used for cutting is located on the rear end side in the direction of the axis O of the end mill main body 11 and on the inner peripheral side of the rotation trajectory of other corner blades 6 connected to the outer peripheral side of the end mill main body 11 of the main cutting edge 5. It is possible to be located at.

  Therefore, when the main cutting edge 5 formed on the side ridge portion of the rake face 3 of one polygonal surface directed in the end mill rotation direction T is used for cutting, the main cutting edge 5 or corner of the other polygonal surface is used. The blade 6 does not interfere with the work material, and the insert body 1 is rotated 120 ° around the insert center line C by 120 ° and reattached to the insert mounting seat 16. After the main cutting edge 5 and the corner blade 6 formed at the corners are used for cutting, the insert main body 1 is turned upside down and reattached to the insert mounting seat 16 to form the other polygonal surface. The main cutting edge 5 and the corner edge 6 can be used for cutting with the rake face 3 facing the end mill rotation direction T. For this reason, when the insert main body 1 has a regular triangular plate shape as described above, a total of six main cutting edges 5 and corner blades 6 formed in one insert main body 1 can be used up, and the efficiency is further increased. And economical.

  In particular, when the insert body 1 is formed into an equilateral triangular plate shape in this way, according to the present embodiment, when one main cutting edge 5 is ramped toward the tip side of the end mill body 11, Even if the digging amount is relatively large, the other main cutting edges 5 can be prevented from interfering with the work material, and the six main cutting edges 5 can be used up more reliably.

  As described above, the embodiments of the present invention have been described. However, the configurations and combinations thereof in the embodiments are examples, and the addition, omission, replacement, and other configurations of the configurations are within the scope not departing from the gist of the present invention. It can be changed. Moreover, the cutting insert of this invention can be used also in blade-tip-exchange-type cutting tools other than a blade-tip-exchange-type end mill. Furthermore, the present invention is not limited by the embodiment.

In the present embodiment, the insert body 1 has a regular triangular plate shape, but other regular polygonal plate shapes, for example, a cutting insert having a square plate-like insert body, or a polygon plate other than a regular polygon plate shape. The present invention can be applied to a cutting insert having a cylindrical insert body and also to a disc-shaped cutting insert.
For example, when applied to a cutting insert having a square plate-like or rectangular plate-like insert body, the number of usable cutting edges is reduced to prevent the above-described interference, but a pair of square or rectangular surfaces is used. The main cutting edge 5 may be formed only on the opposite side.

  In the present embodiment, as described above, when the present invention is applied to a right-handed cutting insert configured to form a right blade that is rotated counterclockwise when the blade-tip replaceable end mill is viewed from the front side. Although described, when applied to a left-handed cutting insert that is a left blade that is rotated clockwise when viewed from the front side, the shape of the insert body is mirror-symmetrical with the insert body 1 of the above embodiment. . However, in either case, one end 5a of the main cutting edge 5 used for cutting is disposed on the inner peripheral side of the tip of the end mill body 11, and the other end 5b is disposed on the outer peripheral side. One end portion 5a is formed in a convex curve shape, and the other end portion 5b is formed in a concave curve shape.

  In the present embodiment, the main cutting edge in which the convex curve portion and the concave curve portion are continuously formed is taken as an example. However, the present invention is not limited thereto, and a straight line is provided between the convex curve portion and the concave curve portion. The present invention can be applied to a cutting blade provided with a portion, and also to a cutting insert including a cutting blade having only a convex curve portion.

DESCRIPTION OF SYMBOLS 1 Insert body 2 Mounting hole 3 Rake face 3a Positive rake face 3b Restraint face 3c Step surface 4 Relief face 5 Main cutting edge 5a One end part of main cutting edge 5b Other end part of main cutting edge 5 6 Corner blade 7 Recess 7b Recess Bottom of 7 11 End mill body (tool body)
14 Blade part 16 Insert mounting seat 17 Projection part 17a Projection end face of projection part 18 Clamp screw C Insert center line O End mill body 11 axis T End mill rotation direction β5 Relief angle of main cutting edge 5 β6 Relief of corner edge 6 Corner

Claims (8)

A rake face is formed on the surface facing the thickness direction of the insert body having a plate shape, and a flank face is formed on the peripheral surface arranged around the surface facing the thickness direction,
A cutting edge is formed at the intersection ridgeline between these rake face and flank face,
The cutting blade has a convex curve portion formed in a convex curve shape when viewed from the direction facing the rake face,
The rake face is a positive rake face that recedes toward the center in the thickness direction as it is separated from the cutting edge,
A cutting insert characterized in that at least a portion of the positive rake face connected to the convex curve portion of the cutting edge is formed in a single flat shape. The cutting edge has a concave curve portion formed in a concave curve shape when viewed from the direction facing the rake face, adjacent to the convex curve portion,
2. The cutting insert according to claim 1, wherein at least a portion connected to the convex curve portion and a portion connected to the concave curve portion of the positive rake face are formed in one flat shape. The insert body is a polygonal plate,
The positive rake face is formed on the polygonal surface of the insert body, and the flank is formed on the peripheral surface of the insert body disposed around the polygonal surface,
A main cutting edge is formed on the side ridge portion of the polygonal surface at the intersection ridge line portion between the rake face and the flank face,
The main cutting edge is formed extending between two corners adjacent to each other in the circumferential direction of the polygonal surface among the corners of the polygonal surface,
The cutting insert according to claim 2, wherein the convex curve portion and the concave curve portion are formed adjacent to the main cutting edge.   The cutting insert according to claim 3, wherein the main cutting edge is formed in a curved shape throughout.   The cutting insert according to claim 3 or 4, wherein a portion of the cutting blade that is highest in the thickness direction is formed on the main cutting blade.   The step surface which inclines more steeply than the angle of the said positive rake surface is formed in the said insert main body center side of the said positive rake surface as described in any one of Claims 3-5 characterized by the above-mentioned. Cutting insert.   The insert body has a regular triangular plate shape, and the main cutting edge is formed on each side ridge portion of the polygonal surface on the front and back sides forming a regular triangle shape, and the polygonal surface on the front and back surfaces is formed of the polygonal surface. The insert body is arranged to be twisted around an insert center line passing through the center, and the insert body has a reverse-inverted symmetrical shape with respect to the polygonal surfaces of the front and back sides. Cutting insert as described in. A cutting edge exchangeable cutting tool,
A tool body that can be rotated in the direction of tool rotation about an axis;
The cutting insert according to any one of claims 1 to 7 detachably attached to the tip of the tool body,
The tool body is formed with one or more insert mounting seats to which the cutting insert is mounted,
The cutting insert is attached to the insert mounting seat so that the rake face faces in the tool rotation direction and the cutting edge faces the tip end side of the tool body. .

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