JP2019119022A - Cutting insert and blade tip replaceable cutting tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a chip from being bitten by a high cutting process and to prevent a chip from being chipped. SOLUTION: A cutting edge 15 formed at an intersecting ridge line portion between a rake surface and a flank surface has a corner blade 15a, a main cutting edge 15b extending from one end of the corner blade 15a, and a secondary cutting edge extending from the other end of the corner blade 15a. A first region 15A having a cutting blade 15d, and a rake angle in a cross section along the insert center line L gradually increases from the end portion 15e of the main cutting blade 15b toward the corner blade 15a, and a corner from the first region 15A. The rake angle gradually decreases toward the blade 15a side in the second region 15B, and the rake angle from the second region 15B including at least a part of the corner blade 15a and the sub cutting blade 15d toward the sub cutting blade 15d side. Has a third region 15C that gradually increases in a range smaller than the first region 15A, and the rake angle of the third region 15C is in the range of 15 ° to 18 °. [Selection diagram] Fig. 2

Description

  The present invention is a cutting insert that is detachably mounted on a cutting edge-replaceable cutting tool such as a tip-exchange-type end mill, and is particularly suitable for high-cut processing, and a cutting edge on which such a cutting insert is removably mounted. It relates to a replaceable cutting tool.

  As a cutting insert and an indexable cutting tool for high feed processing, for example, Patent Document 1 discloses cutting of a triangular plate shape having two triangular surfaces having two substantially triangular shapes in which the insert body has three corners. The insert and one triangular face of the cutting insert are directed as a rake face in the tool rotational direction, and the corner edge formed at one corner of the one triangular face is directed to the outer peripheral side of the tool body, and the one With the main cutting edge extending from one end of the corner blade facing the tip end of the tool body, and with the sub cutting edge (wiper blade) extending from one end of the main cutting blade substantially positioned on a plane perpendicular to the rotation axis of the tool body An indexable cutting tool removably mounted is described.

  In such a cutting insert, the main cutting edge which is directed to the tip end side of the tool main body and directed to the rear end side at a gentle angle with respect to a plane perpendicular to the rotation axis as it goes to the outer peripheral side of the tool main body Since thin chips having a small thickness are generated on the inner peripheral side of the main cutting edge of the main cutting blade and the above wiper blade, an increase in cutting resistance can be suppressed even if the tool main body is fed at a high feed rate. It is possible to perform efficient cutting in the processing of molds and the like. Further, in this patent document 1, when the cutting amount in the Z-axis direction is set large in inclined cutting, the second sub cutting edge connected to the first sub cutting edge also acts as a cutting edge. It is stated that it will be.

Patent No. 5983901

  By the way, in the high cutting process in which the cutting amount in the Z-axis direction is set large as described above, chips having a wide width are generated, chip dischargeability is easily impaired, and it becomes difficult to stabilize the chip outflow direction. There is a risk that chips will bite and degrade the machined surface quality of the work material. In order to prevent such biting of chips, set the rake angle of the cutting edge to a large angle on the regular angle side to reduce the curl diameter of the chips, stabilize the chip outflow direction, and improve the dischargeability. Is considered.

  However, when the rake angle of the cutting edge is increased on the regular angle side, the cutting edge angle of the cutting edge is reduced and the cutting edge strength is impaired, and when a large cutting load or stress is applied, the cutting edge is lost. . In particular, a corner cutting edge directed from the outer peripheral portion of the main cutting edge directed to the front end side of the tool main body to the outer circumference side of the tool main body, and a secondary cutting edge connected to the other end of the corner cutting edge acting as the cutting edge when the cutting amount is large. Such a large cutting load and stress are likely to act on the.

  The present invention has been made under such a background, and prevents cutting of chips in high cutting processing to improve the processing surface quality of the work material while securing the strength of the cutting edge to secure the cutting edge. An object of the present invention is to provide a cutting insert capable of preventing a defect or the like, and an indexable cutting tool to which such a cutting insert is detachably attached.

  In order to solve the problems described above and achieve such an object, the cutting insert of the present invention is a polygon having two polygons in which one is a rake surface and the other is a seating surface. A flank, a flank disposed around the two polygonal faces and having a flank face intersecting the rake face of the polygon face, and a ridge line between the rake face and the flank face Cutting insert having a polygonal plate-like insert body having a cutting edge, the insert body having a rotationally symmetrical shape with respect to an insert center line passing through the centers of the two polygonal faces; The cutting blade has a corner blade located at a corner of the polygon surface, a main cutting blade extending from one end of the corner blade, and the other end of the corner blade. With the extended cutting edge And a first region in which the rake angle in the cross section along the insert center line gradually increases from the end of the main cutting edge opposite to the corner blade toward the corner blade, and the first region The second region where the rake angle gradually decreases toward the corner edge side from the second edge, and the portion including at least a part of the corner edge and the sub cutting edge from the second region toward the sub cutting edge side And a third area in which the rake angle gradually increases in a range smaller than the first area, and the rake angle in the third area is in the range of 15 ° to 18 °.

  Further, in the indexable tool according to the present invention, such a cutting insert may be attached to an insert mounting seat formed on the outer periphery of a tip end portion of a tool body which is rotated about an axis, one of the two polygonal surfaces. The polygon face is directed as a rake face in the tool rotational direction, and the one corner edge of the one polygon face is directed to the outer peripheral side of the tool body, and the one main edge extending from one end of the one corner edge The cutting blade is directed to the tip end side of the tool body, and the end opposite to the corner blade of the one main cutting blade is detachably attached with the tip of the tool body protruding to the forefront of the tool body It features.

  In the cutting insert configured as described above attached to the tool body of the indexable cutting tool in this manner, the corner edge of the one main cutting edge directed to the tip end side of the tool body in the high cutting process. A corner blade directed from the opposite end to the outer peripheral side of the tool body and a portion on the corner blade side of the minor cutting edge extending from the other end of the corner blade are used exclusively for cutting.

  Here, while a relatively thin chip is generated at a portion on the inner peripheral side of the tool main body facing the corner blade side from the end of the main cutting blade on the opposite side to the corner blade, the cutting of the above configuration is performed In the insert, this portion is used as the first region where the rake angle in the cross section along the insert center line gradually increases, and the main cutting edge is sharpened while securing the cutting edge strength to thin chips. The outflow direction can be controlled so as to guide the entire chips generated in a wide width toward the inner peripheral side (axis line side) of the tool main body, and the chip discharge performance can be improved.

  The portion from the first region toward the corner edge of the main cutting edge is a second region in which the rake angle gradually decreases, and the thickness of the chips gradually increases toward the outer periphery of the tool body. While cutting load and stress become large, it becomes possible to secure cutting edge strength and to prevent chipping and the like.

  Furthermore, a portion including at least a part of the corner blade and the minor cutting edge from the second region is a third region in which the rake angle gradually increases in a range smaller than the first region as it goes to the minor cutting edge side. ing. Therefore, in this third area, which is located at the outermost periphery of the tool body, while maintaining the cutting edge strength by the rake angle reduced through the second area, the rake angle is gradually moved toward the minor cutting edge side. By increasing the size, chips can be caught on the inner peripheral side of the tool body with a small curl diameter, and combined with the improvement of the chip dischargeability by the first region, biting of chips can be prevented and a good machined surface quality can be obtained. You can get And since the above-mentioned rake angle of the cutting edge in this 3rd field is made into the range of 15 degrees-18 degrees, biting of chips is secured while securing cutting edge strength certainly as demonstrated in the example mentioned below. It can be prevented.

  Here, the cutting edge has a rake angle at a rate of change larger than that of the first area to the third area as it goes from the third area to the end of the sub cutting edge opposite to the corner blade. It may have a gradually decreasing fourth region. Such a fourth region is used exclusively in the above-described beveling process, but while the thickness of the chips produced is still thick, the rake angle increased in the third region to the fourth region By reducing the rate of change at a rate of change greater than that of the first region to the third region, it is possible to secure the cutting edge strength again and prevent the occurrence of defects and the like.

  Further, the rake angle in the second region is preferably in the range of 15 ° to 25 °. When the rake angle in the second region is less than 15 °, the rake angle in the third region can not be in the range of 15 ° to 18 °, while the rake angle in the second region exceeds 25 °. The blade angle of the cutting edge in the second region may be reduced to make it difficult to secure the cutting edge strength.

  Furthermore, in the case where the insert body is in the form of a triangular plate having three corner portions as in the cutting insert described in Patent Document 1, the first region and the second region are included. The position where the rake angle is maximum at the boundary with the edge is the end of the main cutting edge opposite to the corner blade and the above-mentioned cutting edge as viewed from the direction opposite to the polygonal surface along the insert center line. It is desirable that the angle range from 15 ° to 45 ° toward the corner blade side from a straight line passing through the insert centerline centering on the insert centerline.

  If the position where the rake angle is the largest is within the above-mentioned angle range of less than 15 °, the first region becomes smaller and the flow direction is controlled to sufficiently guide the chips to the inner peripheral side of the tool body. If the position where the rake angle becomes maximum is within the above-mentioned angle range which exceeds 45 °, the blade angle of the main cutting edge becomes smaller at the part where the chips are thickened, and there is a possibility that it will be difficult. Etc. may not be prevented reliably. The angle range in which the rake angle is maximum is preferably in the range of 17 ° to 40 °, and more preferably in the range of 19 ° to 35 °.

  As described above, according to the present invention, the cutting direction of the chips is controlled to be guided to the inner peripheral side of the tool body in the high cutting process to prevent the biting of the chips, and the machined surface of the work material The quality can be improved, and the strength of the cutting edge can be sufficiently secured in accordance with the thickness of the generated chips to prevent the cutting of the cutting edge and the like.

It is a perspective view showing one embodiment of a cutting insert of the present invention. It is the top view which looked at embodiment shown in FIG. 1 from the insert centerline direction. FIG. 3 is a side view in the arrow X direction in FIG. 2; FIG. 3 is a side view in the direction of arrow Y in FIG. 2. It is AL sectional drawing in FIG. It is BL sectional drawing in FIG. It is CL sectional drawing in FIG. It is DL sectional drawing in FIG. It is a perspective view of the tool main body of the blade-tip-exchange-type cutting tool to which the cutting insert of embodiment shown in FIG. 1 is attached detachably. It is a perspective view of the blade-tip-exchange-type cutting tool in which the cutting insert of embodiment shown in FIG. 1 was attached to the tool main body shown in FIG. 9 so that attachment or detachment was possible. It is a figure which shows the rake angle of the cutting blade in the cross section along the insert centerline in the cutting insert of the Example of this invention, and the cutting insert of Comparative Examples 1 and 2. FIG. (A) The figure which shows the outflow state of the chip in the cutting insert of the Example of this invention, (b), (c) It is a figure which shows the outflow state of the chip in the cutting insert of a comparative example. (A) The figure which shows the concentration state of the stress in the cutting insert of the Example of this invention, (b), (c) It is a figure which shows the concentration state of the stress in the cutting insert of a comparative example.

  FIGS. 1 to 8 show an embodiment of the cutting insert of the present invention, and FIG. 9 shows a tool body of an indexable cutting tool to which the cutting insert of this embodiment is detachably attached. FIG. 10 shows an embodiment of the cutting edge-replaceable cutting tool according to the present invention in which the cutting insert of the above embodiment is detachably attached to the tool body. The cutting insert according to the present embodiment includes a polygonal plate-like insert body 11 formed of a hard material such as cemented carbide, and in this insert body 11, two polygonal faces 12 each have three corners. It has a triangular plate shape and is rotationally symmetrical with respect to the insert center line L passing through the centers of the two polygonal faces 12 and is face-up inverted symmetrical with respect to the two polygonal faces 12.

  When these two polygonal surfaces 12 are attached to the tool body 21 of the indexable cutting tool as shown in FIG. 10, one of the polygonal surfaces 12 is a rake surface, and the other polygonal surface 12 is a rake surface. Reference numeral 12 denotes a seating surface for the insert mounting seat 22 formed on the tool body 21. The flanks 14 of the insert body 11 disposed around these two polygonal faces 12 are formed with flanks 14 that intersect with the rake faces of the two polygonal faces 12, and these rake faces (polygonal faces 12). The cutting edge 15 is formed at the intersection ridge line portion of the clearance face 14 and the flank face 14. A mounting hole 16 having a circular cross section centering on the insert center line L for attaching the insert body 11 to the insert mounting seat 22 is provided at the central portion of the two polygonal surfaces 12. It is opened in the L direction.

  The cutting edge 15 has a corner edge 15a in the form of a convex curve such as an arc disposed at three corners of the polygonal surface 12 when viewed from the insert center line L direction, and one end of the corner edge 15a (see FIG. A convex main curved edge 15b having a radius of curvature larger than that of a straight line extending in contact with the corner edge 15a from the end on the clockwise direction centering around the insert center line L or the convex edge formed by the corner edge 15a A convex curved wiper blade 15c having a radius of curvature larger than that of a straight line extending in a direction intersecting the main cutting edge 15b and an obtuse angle at one end of the main cutting edge 15b or a convex curve formed by the main cutting edge 15b is provided. Further, the cutting blade 15 further includes a linear sub cutting blade 15 d as viewed from the direction of the insert center line L extending from the other end of the corner blade 15 a in contact with the corner blade 15 a. The other cutting edge 15 adjacent to the other end side (the counterclockwise direction side in FIG. 2) of the cutting edge 15 extends in a direction intersecting with the wiper blade 15 c of the other cutting edge 15 at an obtuse angle.

  The flanks 14 are formed on the edge of the side face 13 of the insert body 11 on the side of the two polygonal faces 12, and between these flanks 14, the insert in a cross section along the insert center line L A plurality of insert restraint surfaces 17 extending in the direction of the center line L are formed in directions intersecting with each other when viewed from the direction of the insert center line L. In the present embodiment, these insert constraining surfaces 17 are planar parallel to the insert center line L, and are formed inside the insert center line L direction of the main cutting edge 15b and the sub cutting edge 15d, and are adjacent to each other. The portion of the corner blade 15a located inside in the direction of the insert center line L between the insert constraining surfaces 17 is connected by a convex curved surface.

  In addition, a flat portion 12a perpendicular to the insert center line L is formed around the opening of the mounting hole 16 in the polygonal surface 12 which is a rake surface, and this flat surface is formed on the corner blade 15a side. The inclined part 12b which inclines so that it may protrude in the insert centerline L direction as it goes to the cutting blade 15 side from the part 12a is formed. In the present embodiment, among the cutting edges 15, the full length of the corner cutting edges 15a and the main cutting edges 15b, a part of the wiper cutting edge 15c that intersects the main cutting cutting edges 15b, and the corner cutting edges 15a of the auxiliary cutting edges 15d. A part of the side is formed at the intersection ridge line portion of the inclined portion 12b and the flank surface 14, and the remaining part of the wiper blade 15c and the sub cutting edge 15d is formed at the intersection ridge line portion of the plane portion 12a and the flank surface 14 ing. The difference in height in the direction of the insert center line L between the position of the cutting edge 15 most projecting in the direction of the insert center line L and the flat portion 12a is, for example, 0.6 mm.

  The cutting edge 15 has a rake angle θ with respect to the flat surface portion 12a in a cross section along the insert center line L as it goes from the end 15e of the main cutting edge 15b opposite to the corner edge 15a to the corner edge 15a. A gradually increasing first region 15A, a second region 15B in which the rake angle θ gradually decreases from the first region 15A toward the corner blade 15a, and a corner blade 15a and an auxiliary cutting edge 15d from the second region 15B And a third area 15C in which the rake angle θ gradually increases in a range smaller than the first area 15A as it goes to the side of the minor cutting edge 15d in a portion including at least a part of Furthermore, the rake angle θ in the third region 15C is in the range of 15 ° to 18 °. In the present specification, as described above, the inclination angle of the rake surface of the inclined portion 12b based on the flat portion 12a of the cutting insert alone is referred to as the rake angle θ for convenience.

  Further, the cutting blade 15 further changes from the first area 15A to the third area 15C at a larger change rate as it goes from the third area 15C to the end 15f of the sub cutting edge 15d opposite to the corner blade 15a. The rake angle θ has a fourth region 15D in which the rake angle θ gradually decreases. The rake angle θ of the portion of the cutting edge 15 formed at the intersection ridge line portion between the flat surface portion 12a and the flank surface 14 is 0 °.

  Here, in FIG. 11, reference symbol A denotes a cutting insert of the present embodiment having a triangular plate-like insert main body 11, in which the main cutting edge 15 b on the opposite side to the corner edge 15 a along the insert center line L The cross section passing through the end portion 15e is a reference 0 ° position, and the corner edge 15a of the other cutting edge 15 located at 120 ° in the counterclockwise direction around the insert center line L in FIG. Is expressed by calculating the rake angle θ in the cross section along the insert center line L up to the end 15e of the main cutting edge 15b on the opposite side by 5 °, according to this, the cross section position in the present embodiment The angle range of 0 ° to 25 ° is the first area 15A.

  In addition, an angle range of 25 ° to 60 ° at the cross-sectional position on the side of the corner blade 15a from the first area 15A is the second area 15B in the present embodiment. Therefore, the rake angle θ is the second area 15B. The cross-sectional position which is the boundary between the first region 15A and the first region 15A has a maximum value as shown in FIG. In the present embodiment, the maximum value of the rake angle θ is 23.526 °. Furthermore, in the present embodiment, the main cutting edge 15b is formed in an angle range of 0 ° to 60 ° at the cross-sectional position, and the whole is formed in the first and second regions 15A and 15B. Here, the rake angle θ in the second region 15B is preferably in the range of 15 ° to 25 °, and the rake angle θ of the position of the cross section shown in FIG. 6 at an angle of 45 ° is 20.456 °. is there.

  Furthermore, in the present embodiment, the third region 15C has an angle range of 60 ° to 75 ° at the cross section position, and the corner blade 15a has an angle range of 60 ° to 70 ° at the cross section position. Is formed, so that one end of the corner blade 15a is located at the boundary between the second area 15B and the third area 15C, and the rake angle .theta. At this boundary shown in FIG. . That is, the whole of the corner blade 15a is formed in the third region, and a part of the minor cutting edge 15d on the corner blade 15a side is also formed in the third region 15C.

  Furthermore, in this embodiment, the angle range of the said cross-sectional position of 75 degrees-95 degrees is made into 4th area | region 15D. Therefore, the position where the angle of the cross section position is 75 ° is the boundary between the third area 15C and the fourth area 15D, and the rake angle θ at the position of this boundary shown in FIG. It is considered to be in the range of 18 °.

  Further, as shown in FIG. 11, in the fourth area 15D, the rake angle θ gradually decreases at a rate of change larger than that of the first to third areas 15A to 15C. Here, assuming that [change amount of rake angle θ (°)] / [angle change amount of cross section (°)] is the angle change rate of the rake angle θ, the angle change rate of the first region 15A is 30% to It is in the range of 45%, 40% in the present embodiment, and the angle change ratio of the second region 15B is in the range of -15% to -25%, and is -20% in the present embodiment. The angle change rate of the third area 15C is in the range of 0.3% to 8%, and is 5% in the present embodiment, while the angle change rate in the fourth area 15D is -97% to -77%. It is a range, and is set to -87% in this embodiment.

  The cutting insert according to the present embodiment is detachably attached to the insert mounting seat 22 formed on the outer periphery of the tip end portion of the tool body 21 of the indexable cutting tool as shown in FIG. 9, and is shown in FIG. Such an indexable cutting tool according to an embodiment of the present invention is configured. The tool body 21 has a substantially cylindrical shape around the axis O. During cutting, the rear end is gripped by the main shaft of the machine tool and rotated about the axis O in the tool rotational direction T, by the cutting insert The cutting material is cut.

  A plurality of (five in this embodiment) tip pockets 23 are formed on the outer periphery of the tip end portion of the tool main body 21, and the insert mounting seat 22 is a tip end portion of a wall surface facing the tool rotation direction T of these tip pockets 23. A flat bottom 22a formed on the outer periphery, facing in the tool rotation direction T, and spaced from the bottom 22a in the tool rotation direction T, is in contact with the insert restraint surface 17 of the insert body 11 A plurality of possible planar wall surfaces 22b are provided. The bottom surface 22a is formed with a screw hole 22c into which the clamp screw 24 inserted into the mounting hole 16 is screwed.

  The cutting insert of the present embodiment is directed to such an insert mounting seat 22 with the one polygonal surface 12 of the insert main body 11 as a rake face in the tool rotational direction T, and the flat portion 12a of the other polygonal surface 12 Is placed in close contact with the bottom surface 22 a of the insert mounting seat 22. Furthermore, the cutting insert causes the corner blade 15a located at one corner of the one polygonal surface 12 to protrude to the outer peripheral side of the tool main body 21, and the main cutting blade 15b extending from one end of the corner blade 15a The end 15e of the main cutting edge 15b opposite to the corner edge 15a of the main cutting edge 15b is protruded toward the tip end of the main body 21 so that the end 15e of the tool main body 21 protrudes to the mounting hole 16 It fixes by screwing in the clamp screw 24 penetrated to the screw hole 22c.

  The wiper blade 15c extending from the end 15e of the tool main body 21 which is projected to the tip end is disposed so that the watermark angle is 2 ° or less with respect to a plane perpendicular to the axis O, that is, The wiper blade 15c is disposed along a plane perpendicular to the axis O, or inclined toward the rear end side toward the inner peripheral side of the tool body 21 at an angle of 2 ° or less with respect to this plane Be placed. At this time, the insert restraint surface 17 of the side surface 13 connected to the cutting edge 15 not used for cutting is brought into contact with the wall surface 22b of the insert mounting seat 22, and rotation of the insert body 11 around the insert center line L is restrained.

  The indexable cutting tool attached with the cutting insert in this manner is fed out in a direction perpendicular to the axis O while being rotated about the axis O, and protrudes to the tip of the tool body 21 in the case of high cutting. The material to be cut is cut by the corner blade 15a protruding outward from the end 15e of the main cutting blade 15b and the portion on the corner blade 15a side of the auxiliary cutting blade 15d connected to the other end of the corner blade 15a The bottom surface of the processing surface is finished by a wiper blade 15c connected to 15e.

  Since the main cutting edge 15b has a linear shape or a convex curved shape having a radius of curvature larger than that of the corner edge 15a, the thickness of the chips generated by the inner peripheral portion of the tool body 21 becomes relatively thin. On the other hand, in the cutting insert of the above configuration, this portion is the first region 15A where the rake angle θ in the cross section along the insert center line L gradually increases, and the cutting for such thin chips is performed The main cutting edge 15b can be sharpened while ensuring the strength of the blade, and the flow direction is controlled so as to guide the entire chip generated widely to the inner peripheral side (axis line side) of the tool main body 21. It is possible to improve chip dischargeability.

  The thickness of chips gradually increases from the portion on the inner peripheral side of the tool main body 21 of the main cutting edge 15b toward the corner edge 15a on the outer peripheral side of the tool main body 21, and the cutting load or stress acting on the cutting edge 15 It will grow gradually. On the other hand, in the cutting insert having the above-described configuration, this portion is the second region 15B in which the rake angle θ gradually decreases even on the regular angle side as it goes to the corner blade 15a side, and thus the chip becomes thicker The strength of the cutting edge can be secured against cutting load and stress due to the above to prevent the occurrence of chipping and the like.

  Further, a portion including at least a part of the corner blade 15a and the sub cutting edge 15d from the second region 15B (in the present embodiment, the whole of the corner blade 15a and the portion on the corner blade 15a side of the sub cutting edge 15d) is The third region 15C is such that the rake angle θ gradually increases in a range smaller than the first region 15A toward the side of the minor cutting edge 15d. For this reason, in the third region 15C located at the outermost periphery of the tool body 21, the cutting force is maintained by the rake angle θ which is reduced in the second region 15B, and the chips have a small curl diameter inside the tool body 21. Since the first region 15A improves the chip discharge performance, biting of chips can be prevented and good machined surface quality can be obtained.

  Further, since the rake angle θ of the cutting edge 15 in the third region 15C is in the range of 15 ° to 18 °, biting of chips can be prevented while ensuring the strength of the cutting edge. That is, as described in the examples described later, when the rake angle θ in the third region 15C is less than 15 ° or more than 18 °, it is difficult to curl chips with a small curl diameter, and biting occurs. There is a risk of Further, if the rake angle θ exceeds 18 °, the blade angle becomes small, the strength of the cutting edge is impaired, and there is a possibility that the chipping easily occurs.

  Further, in the present embodiment, the cutting blade 15 is larger than the first to third regions 15A to 15C as it goes from the third region 15C to the end 15f of the sub cutting blade 15d opposite to the corner blade 15a. The rake angle θ has a fourth area 15D in which the rake angle θ gradually decreases at a change rate (angle change rate). Such a fourth region 15D is exclusively used in oblique cutting processing in which cutting is performed by feeding the tool main body 21 obliquely to the axis O, but the thickness of chips generated in the fourth region 15D Is still thick, while the rake angle .theta. Increased in the third region 15C is reduced by a larger angle change rate in the fourth region 15D than in the first region 15A to the third region 15C. It is possible to secure strength again and prevent the occurrence of defects and the like.

  Here, the rake angle θ in the second region 15B is preferably in the range of 15 ° to 25 ° as described above. If the rake angle θ in the second region 15B is less than 15 °, the rake angle θ in the third region 15C can not be in the range of 15 ° to 18 °, and chip processing properties may be impaired. On the other hand, if the rake angle θ in the second region 15B exceeds 25 °, the blade angle of the cutting edge 15 in the second and third regions 15B and 15C may be too small, which may lead to defects and the like.

  In the cutting insert of the present embodiment in which the insert body 11 has a triangular plate shape having three corners on each of the two polygonal surfaces 12, the scoop is generated at the boundary between the first area 15A and the second area 15B. The position where the angle θ is maximized is the end 15e of the main cutting edge 15b opposite to the corner edge 15a and the insert center line L when viewed from the direction facing the polygonal surface 12 along the insert center line L. It is desirable for the angle range of 15 ° to 45 ° toward the corner blade 15a side from the straight line passing through the insert center line L, and in the present embodiment, the cross-sectional position is around 25 ° as described above.

  If the position where the rake angle θ is maximum is within the above-mentioned angle range of less than 15 °, the first region 15A becomes smaller and the flow direction is controlled so as to sufficiently guide the chips to the inner peripheral side of the tool body. May be difficult. On the other hand, when the position where the rake angle θ is maximum is in the above-mentioned angle range exceeding 45 °, the blade angle of the cutting edge 15 becomes small at the part where the chips are generated thick. There is a risk that it can not be reliably prevented. The angle range in which the rake angle θ is maximum is preferably in the range of 17 ° to 40 °, and more preferably in the range of 19 ° to 35 °.

  Further, in the cutting insert according to the present embodiment, a plurality of flanks 14 on the side of the two polygonal surfaces 12 on the side surface 13 of the insert body 11 extend in the direction of the insert center line L in a cross section along the insert center line L The insert restraint surfaces 17 are formed in directions intersecting with each other when viewed from the insert center line L direction. Therefore, as described above, by bringing these insert restraint surfaces 17 into contact with the wall surface 22b of the insert mounting seat 22, the rotation of the insert body 11 around the insert center line L can be restrained, and cutting is more stable. It is possible to do

  Next, the effects of the above rake angle θ in the third region 15C of the present invention will be demonstrated by way of examples. In the present embodiment, as shown by the symbol A in FIG. 11, using a cutting insert having a rake angle θ in the range of 15 ° to 18 ° in the third region 15C, the spindle rotational speed 808.0 rpm, per blade The case where high cut processing was performed to the cut material which consists of S50C under cutting conditions of a feed amount of 0.7 mm, a radial cut depth of 45.0 mm, and an axial cut depth of 3.0 mm was analyzed. In addition, as Comparative Example 1 to this embodiment, when the rake angle θ in the third region 15C indicated by the reference B in FIG. 11 is less than 15 °, the third example shown by the reference C in FIG. The rake angle θ in the region 15C is greater than 18 °, and analysis is also performed in the case where high cutting is performed under the same cutting conditions as in the example.

  12 (a) to 12 (c) show the outflow of chips according to these Examples and Comparative Examples 1 and 2. FIG. 12 (a) shows an Example, FIG. 12 (b) shows a Comparative Example 1, FIG. 12C shows the result of Comparative Example 2. According to FIGS. 12 (a) to 12 (c), the chips are curled with a small curl diameter in the example, while in the comparative examples 1 and 2, the chips do not curl but become slightly stretched, which may cause biting. It is understood that there is.

  13 (a) to 13 (c) are analysis of stress concentration in the example and the comparative examples 1 and 2, FIG. 13 (a) is an example, and FIG. 12 (b) is a comparative example 1, FIG. 12C shows the result of Comparative Example 2, in which the dark portion on the cutting edge side is a portion to which high stress is applied. From the results of FIGS. 12 (a) to 12 (c), it can be seen that stress is concentrated on the cutting edge 15 used for cutting in both the embodiment and the comparative examples 1 and 2, but in particular, the rake angle θ is It is understood that high stress is applied in Comparative Example 2 in which the angle is more than 18 °, and there is a possibility that the cutting edge may be chipped due to the small blade angle.

  In addition, below, an example of the measuring method of the inclination-angle (The rake angle (theta) mentioned above in this specification) of the rake surface of a cutting insert is described. First, in a first step, the three-dimensional shape of the insert body 1 is measured using a noncontact three-dimensional measuring device, and the measurement results are stored as electronic data. Next, as a second step, using the three-dimensional measurement data and the shape measurement software, at the ridge line portion of the cutting edge 15 of the insert body 1, the insert at every predetermined radiation angle interval width from the insert center line L A plurality of cross sections along the center line L are created. Finally, as a third step, by obtaining a cross-sectional view of the ridge line portion of the cutting edge 15 of the insert main body 1 as shown in FIGS. 5 to 8, the rake surface and the flat portion 12a of the insert main body are used as a reference surface. The inclination angle of the rake surface of the inclined portion 12b, that is, the rake angle θ can be obtained.

11 insert body 12 polygon surface 12a flat surface portion 12b inclined portion 13 side surface 14 flank surface 15 cutting edge 15a corner cutting edge 15b main cutting edge 15c wiper cutting edge 15d minor cutting edge 15A first area 15B second area 15C third area 15C third area 15D fourth Region 16 Mounting hole 17 Insert restraint surface 21 Tool body 22 Insert mounting seat 23 Tip pocket 24 Clamp screw L Insert center line θ Rake angle of cutting edge 15 in section along insert center line O Axis of tool body 21 T direction of tool rotation

Claims (5)

Two polygonal surfaces, one of which is a rake surface, and the other is a seating surface, and one of the polygonal surfaces is disposed around the two polygonal surfaces and intersects with the rake surface of the polygonal surface. A cutting insert comprising: a polygonal plate-like insert body having a side face on which a flank face is formed and a cutting edge formed at a cross ridge line portion between the rake face and the flank face,
The insert body has a rotationally symmetrical shape with respect to an insert center line passing through the centers of the two polygonal faces, and has a front and back inverted symmetrical shape with respect to these two polygonal faces,
The cutting blade includes a corner blade located at a corner of the polygonal surface, a main cutting blade extending from one end of the corner blade, and a minor cutting blade extending from the other end of the corner blade.
A first region in which the rake angle in the cross section along the insert center line gradually increases from the end of the main cutting edge opposite to the corner blade to the corner blade side, and the corner from the first region A second region where the rake angle gradually decreases toward the blade side, and a portion including at least a part of the corner blade and the sub cutting edge from the second region, the rake angle toward the sub cutting edge side And a third region that gradually increases in a range smaller than the first region,
A cutting insert characterized in that the rake angle in this third region is in the range of 15 ° to 18 °.   The rake angle gradually decreases at a larger change rate than the first area to the third area from the third area toward the end of the auxiliary cutting edge opposite to the corner blade from the third area to the cutting edge. The cutting insert according to claim 1, characterized in that it has a fourth region.   The cutting insert according to claim 1 or 2, wherein the rake angle in the second region is in the range of 15 ° to 25 °. The insert body is in the form of a triangular plate in which the two polygonal faces each have three corners,
The position at which the rake angle is maximum at the boundary between the first area and the second area is the side opposite to the corner blade when viewed from the direction opposite to the polygonal surface along the insert center line. A straight line passing through the end of the main cutting edge and the insert center line is within an angle range of 15 ° to 45 ° toward the corner blade side centering on the insert center line. The cutting insert according to any one of the claims 3. The cutting insert according to any one of claims 1 to 4, in an insert mounting seat formed on an outer periphery of a tip end portion of a tool body rotated about an axis.
One of the above two polygonal faces is used as a rake face and directed in the tool rotational direction,
The one corner edge of this one polygonal surface is directed to the outer peripheral side of the tool body,
One main cutting edge extending from one end of the one corner blade is directed to the tip end side of the tool body, and the end opposite to the corner blade of the one main cutting edge is the most distal end of the tool body A cutting edge-replaceable cutting tool characterized in that it is detachably attached to a tip so as to protrude therefrom.