JP2013121640A - Cutting insert and indexable end mill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure the cutting edge strength of main cutting edges at a portion in which cutting chips are increased in thickness, to prevent abnormal damage by preventing the thickness of the cutting chips from becoming excessively thick, and to perform further efficient high feed processing by further increasing a feed amount.SOLUTION: Rake faces 3 are formed at polygonal faces of an insert body 1 formed into a polygonal plate shape, flanks 4 are formed at side faces arranged at the surrounding of the polygonal faces, the main cutting edges 5 are formed at side ridges of the polygonal faces at cross ridge lines between the rake faces 3 and the flanks 4, one-side ends 5a of the main cutting edges 5 are formed into protrusive curved line shapes and other ends 5b are formed into recessive curved line shapes when viewed from a direction opposing the rake faces 3, and rake angles α5 of the main cutting edges 5 are made large toward a negative angle side as progressing toward the one-side ends 5a at the other ends 5b.

Description

  The present invention particularly relates to a cutting insert that is detachably attached to a cutting edge replaceable end mill for high feed machining, and a cutting edge replaceable end mill for high feed machining to which the cutting insert is attached.

  As cutting inserts attached to such a high-feed cutting edge end mill, for example, in Patent Documents 1 and 2, a substantially equilateral triangle plate shape is formed, and the front and back surfaces forming the equilateral triangle are selectively scooped surfaces. 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 connected to the corner blades has been proposed. .

  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

  By the way, in these Patent Documents 1 and 2, Patent Document 1 describes that the main cutting edge is formed in a polygonal line composed of a straight line intersecting an obtuse angle, and the cutting insert described in Patent Document 2 is The main cutting edge is formed to be convexly curved. However, when high-feed machining is performed with such a cutting insert, the cutting angle increases toward the outer peripheral side of the end mill body, and thus the thickness of the generated chips increases toward the outer peripheral side.

  And since the thickness of this chip becomes the maximum at the cutting boundary part of the outermost periphery of the main cutting edge, the main cutting edge of the cutting insert may cause abnormal damage such as chipping and chipping at the cutting boundary part. For this reason, for example, it is necessary to suppress the feed amount per tooth so that the thickness of the chips does not become too thick, and it is difficult to further increase the feed amount and perform more efficient high feed processing. It was.

  The present invention has been made under such a background, and ensures the strength of the main cutting edge at the portion where the chip becomes thick and prevents abnormal damage by preventing the thickness of the chip from becoming too thick. It is an object of the present invention to provide a cutting insert capable of preventing the above, further increasing the feed amount and performing more efficient high-feed machining, and a blade-tip replaceable end mill to which the cutting insert is detachably attached. .

  In order to solve the above problems and achieve such an object, a cutting insert according to the present invention has a rake face formed on a polygonal surface of an insert body having a polygonal plate shape and a periphery of the polygonal surface. A flank is formed on the side surface arranged at the side, and a main cutting edge is formed at a side ridge of the polygonal surface at the intersection ridge line portion between the rake surface and the flank, and faces the rake surface. One end of the main cutting edge has a convex curve shape and the other end has a concave curve shape, and the rake angle of the main cutting edge is the one end portion at the other end portion. It is characterized by being enlarged toward the negative angle side as it goes to.

  Further, the blade tip replaceable end mill of the present invention is a blade tip replaceable type in which such a cutting insert is detachably attached to an insert mounting seat formed at a tip portion of an end mill main body that is rotated in an end mill rotating direction around an axis. An end mill, wherein the cutting insert has the rake face directed in the direction of rotation of the end mill, the main cutting edge directed toward the tip side of the end mill body, and the one end of the main cutting edge directed to the inner periphery of the end mill body. The other end is positioned on the outer peripheral side of the end mill body, and the main cutting edge is attached so as to gradually extend to the rear end side of the end mill body from the one end to the other end. It is characterized by being.

  In the cutting insert of the above configuration attached to the end mill body in this way, the main cutting edge as viewed from the direction facing the rake face has a convex curve at one end positioned on the inner peripheral side of the end mill body, Since the other end located on the outer peripheral side of the end mill body has a concave curved shape, the cutting angle of the main cutting edge once increases toward the outer peripheral side of the end mill main body and then decreases. For this reason, it is possible to prevent the chips from becoming thicker at the cutting boundary of the main cutting edge on the outer peripheral side of the end mill body, to prevent abnormal damage such as chipping and chipping, and the maximum thickness of the chips itself. It can be kept small.

  In addition, when the cutting angle is once increased toward the outer peripheral side of the end mill body and then decreased, the position where the thickness of the chip becomes maximum is from the cutting boundary portion of the main cutting edge on the outer peripheral side of the end mill body to the inner periphery of the end mill body. Although it is displaced to the central part closer to the side, the rake angle of the main cutting edge is a negative angle at the other end of the main cutting edge located on the outer peripheral side of the end mill body toward the one end located on the inner peripheral side of the end mill main body. It is getting bigger towards the side. Therefore, the blade angle of the main cutting edge can be increased at the central part where the thickness of the chip becomes thick to ensure the cutting edge strength, so that the feed amount can be further increased to perform more efficient high feed processing. It becomes possible.

  Here, in such a blade-tip-exchange-type end mill, in addition to feeding the end mill main body in a direction perpendicular to the axis as described above, the end mill main body is slightly fed in the axial direction to process the work material. In recent years, the ramping process is frequently performed. In this ramping process, since the main cutting edge is cut into the work material from one end portion that protrudes toward the end mill body tip side, in the cutting insert frequently used in such a ramping process, the main cutting edge By making the rake angle constant at one end of the rake, the rake angle at one end remains larger from the other end toward the negative angle side, so the main cutting edge is cut into the work material. Chipping and chipping can be prevented.

  On the other hand, when the rake angle is increased toward the one end side at the other end of the main cutting edge, the rake angle of the main cutting edge at the one end is directed toward the negative angle side toward the other end. As described above, the cutting edge strength at the center part between the one end part and the other end part of these main cutting edges is secured as described above, while the rake angle is set to the positive side at both ends. It becomes large and can improve the sharpness of the main cutting edge. For this reason, the cutting resistance can be reduced and more efficient cutting can be promoted.

  In addition, since the clearance angle of the main cutting edge is increased toward the positive angle side at the other end portion than the one end portion, the one end portion has a larger clearance angle on the negative angle side than the other end portion. Chipping and chipping during the ramping process described above can be more reliably prevented, and cutting resistance can be reduced at the other end of the main cutting edge.

  On the other hand, the radius of curvature of the main cutting edge formed in the concave and convex shape is such that the curvature radius of the concave curve formed by the other end is made larger than the radius of curvature of the convex curve formed by the one end. Since the position where the thickness becomes the thickest can be set closer to the center of the main cutting edge, the cutting edge strength can be further sufficiently ensured. Further, if the convex curve formed by the one end and the concave curve formed by the other end are in contact with each other and the main cutting edge is a smoothly continuous concave / convex curve, the amount of variation in chip thickness is also smooth. Thus, the burden on the main cutting edge can be reduced.

  Further, the insert body has a regular polygonal plate shape, and the main cutting edge is formed at each side ridge portion of the polygonal surface on the front and back sides forming a regular polygonal shape, and the polygonal surfaces on the front and back sides are By arranging the insert body to be twisted around the center line of the insert passing through the center of the polygonal surface, and making the insert body symmetrical with respect to the polygonal surface on the front and back sides, the polygonal surface on the front and back sides is formed with one insert body. Without causing interference, the main cutting edge formed on the side ridge portion can be used evenly for cutting.

  As described above, according to the present invention, the strength of the main cutting edge is secured at the portion where the chip becomes thick and the thickness of the chip itself is prevented from becoming too thick to prevent abnormal damage to the main cutting edge. Further, it is possible to further increase the feed amount and perform more efficient high feed processing.

It is a perspective view which shows 1st Embodiment of the cutting insert of this invention. It is a top view of embodiment shown in FIG. It is a side view of embodiment shown 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. It is a perspective view which shows one Embodiment of the blade-tip-exchange-type end mill of this invention which attached the cutting insert of embodiment shown in FIG. FIG. 7 is a plan view of the blade edge replaceable end mill shown in FIG. 6. It is a side view of the blade-tip-exchangeable end mill shown in FIG. FIG. 7 is an enlarged front view of the blade edge replaceable end mill shown in FIG. 6. (A) When high feed processing is performed, (a) A diagram showing a cross section of the chip generated by the blade-end-exchangeable end mill shown in FIG. 6, (b) Chip generated by the blade-tip-exchangeable end mill equipped with a conventional cutting insert It is a figure which shows a cross section. It is a perspective view which shows 2nd Embodiment of the cutting insert of this invention. It is a top view of embodiment shown in FIG. It is (a) AA expanded sectional view in FIG. 12, (b) BB expanded sectional view, (c) DD expanded sectional view, (d) EE expanded sectional view, (e) FF expanded sectional view.

  FIGS. 1 to 5 show a first embodiment of the cutting insert of the present invention, and FIGS. 6 to 9 show an embodiment of the edge-replaceable end mill of the present invention to which the cutting insert of this embodiment is attached. It is shown. In the cutting insert of the present embodiment, the insert body 1 is a polygonal plate shape, specifically a regular polygonal plate shape by a hard material such as cemented carbide, and is formed in a substantially square plate shape in the present embodiment, At the center of the pair of front and back polygonal surfaces of the insert body 1 having a substantially square shape, the insert body 1 penetrates in the thickness direction of the insert body 1 (vertical direction in FIG. 3) and the insert body 1 is an end mill of a blade-tip replaceable end mill. An attachment hole 2 for attaching to the main body 11 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 having a square plate shape has a rotationally symmetric shape of 90 ° around the insert center line C, and the thickness of the insert body 1 is perpendicular to the insert center line C. It passes through the center of the direction, passes through the bisector of the diagonal lines of the front and back square surfaces twisted in the insert center line C direction view, and the center of the side surface of the insert body 1 arranged around the square surfaces of the front and back surfaces. The shape is symmetrical with respect to the straight line.

  A rake face 3 is formed on the front and back polygonal surfaces of the insert body 1, and a flank 4 is formed on the side surface of the insert body 1 disposed around these polygonal faces. . 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 1/4 arc as viewed 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. A positive rake face 3a that inclines so as to recede in the thickness direction toward the opposite polygon face side, and the periphery of the opening of the attachment hole 2 at the center of the polygon face is perpendicular to the insert center line C. The restraint surface 3b is used. The main cutting edge 5 and the corner edge 6 may be formed with lands or round honing.

  Further, the four side surfaces arranged around the rectangular surfaces on the front and back sides of the insert body 1 are formed such that the center portion in the thickness direction of the insert body 1 is recessed as shown in FIG. The recessed portion has a square shape whose diagonal line is a bisector between diagonal lines of the front and back square surfaces in a cross section orthogonal to the insert center line C, and each of them is a planar shape extending parallel to the insert center line C. Yes. The flank surfaces 4 of the main cutting edge 5 and the corner edge 6 are respectively formed in convex portions with respect to the concave portions on both outer sides in the thickness direction of the respective side surfaces.

  Here, in the cutting insert of the present embodiment, the main cutting edge 5 and the corner edge 6 used at the time of cutting are rotated counterclockwise as seen from the front side as shown in FIG. 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.

  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 regular angle side from one end portion 6a of the corner blade 6 connected to the one end portion 5a of the main cutting edge 5 toward the other end portion 6b of the corner blade 6. Has been. That is, the flank 4 is recessed from the one end portion 6a toward the other end portion 6b so as to recede from the corner blade 6 in the thickness direction in the cross section with a larger recess. Note that the clearance angle β6 of the corner blade 6 in this embodiment is 0 ° at one end 6a of the corner blade 6, and is therefore a positive angle at the other end 6b of the corner blade 6, but 20 ° or less. In order to become, it is gradually increased to the positive angle side.

  Further, the clearance angle β5 of the main cutting edge 5 is also a positive angle side at the other end portion 5b of the main cutting edge 5 with respect to the one end portion 5a of the main cutting edge 5 as shown in FIGS. Has been increased towards. In other words, at one end portion 5a of the main cutting edge 5, the clearance angle β5 is made larger on the negative angle side than the other end portion 5b. Here, the clearance angle β5 of the main cutting edge 5 is, as shown in FIG. 2, a plane cross section (insert body) including an insert center line C and a straight line passing through the center of the side surface of the insert body 1 in this embodiment. 1 is a cross section perpendicular to the concave plane at the center of the side surface (DD cross section in FIG. 2) and a cross section parallel to the cross section. It is an angle.

  The clearance angle β5 of the main cutting edge 5 is a contact point (one end of the main cutting edge 5 and one end of the corner blade 6) at the one end 5a of the main cutting edge 5 with the corner blade 6 connected to the one end 5a. The clearance angle β6 at one end portion 6a of the corner blade 6 is set to 0 °, and the other end portion 5b of the main cutting blade 5 is gradually increased toward the positive angle side. The clearance angle β5 of the main cutting edge 5 at the contact point with the other corner blade 6 connected to the other end portion 5b of the main cutting edge 5 is the clearance angle β6 of the other end portion 6b of the other corner blade 6 at the contact point. So that the flank 4 of the main cutting edge 5 and the corner edge 6 is smoothly continuous.

  The main cutting edge 5 has the one end portion 5a of the main cutting edge 5 connected to the corner blade 6 as shown in FIG. A convex curve having a radius of curvature larger than the convex curve formed by the corner blade 6 is formed, and the other end portion 5b of the main cutting blade 5 is formed in a concave curve. Here, the concave-convex curve formed by the main cutting edge 5 is the curvature radius of the concave curve formed by the other end portion 5b of the main cutting edge 5 rather than the curvature radius of the convex curve formed by the one end portion 5a of the main cutting edge 5. Has been made larger.

  In the present embodiment, the convex curve formed by the 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. 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, In this embodiment, the main cutting edge 5 and the corner edge 6 formed on the side ridges and corners of the polygonal surfaces on the front and back sides, which are the rake face 3, have a smoothly continuous uneven curve in this embodiment. I will draw and go around.

  Further, the rake angle α5 of the main cutting edge 5 is increased toward the negative angle side toward the one end 5a of the main cutting edge 5 at the other end 5b of the main cutting edge 5. Here, the rake angle α5 of the main cutting edge 5 is the main cutting edge 5 in a cross section by a plane including the above-mentioned insert center line C and a straight line passing through the center of the side surface of the insert body 1 and a cross section parallel thereto. The positive rake face 3a that is continuous with the angle is made with respect to a plane perpendicular to the center line C of the insert, and as the positive rake face 3a moves away from the main cutting edge 5 toward the inside of the square face, The side inclined toward the surface side so as to recede in the thickness direction with respect to the plane perpendicular to the insert center line C is separated from the opposite quadrangular surface toward the regular side, and conversely toward the inner side of the quadrangular surface. The side that inclines so as to rise in the thickness direction with respect to the plane perpendicular to the insert center line C is the negative angle side. Accordingly, the rake angle α5 of the main cutting edge 5 in the present embodiment is increased toward the negative angle side toward the one end portion 5a in the other end portion 5b within the positive angle range.

  In the present embodiment, the rake angle α5 of the main cutting edge 5 is set to a large rake angle α5 on the negative angle side at the one end 5a side of the other end 5b in the one end 5a of the main cutting edge 5. The angle is kept constant. Therefore, as shown in FIG. 2, the width of the positive rake face 3a when viewed from the direction facing the rake face 3 in the direction of the insert center line C is constant at one end portion 5a of the main cutting edge 5, and the other end portion. In b, it becomes gradually smaller as it is separated from the one end portion 5a.

  Further, the rake angle α6 of the corner blade 6 is made larger at the one end portion 6a of the corner blade 6 connected to the one end portion 5a of the main cutting edge 5 on the negative angle side than the other end portion 6b. 5a, one end portion 6a of the corner blade 6, and the other end portion 5b of the main cutting blade 5 and the other end portion 6b of the other corner blade 6 connected thereto, the rake angle α5 of the main cutting blade 5 And the rake angles α6 of the corner blades 6 are equal to each other. Accordingly, the positive rake face 3a of the rake face 3 is also made to continue smoothly in the range where the rake angles α5 and α6 are positive angles.

  The cutting edge replaceable end mill according to this embodiment to which the cutting insert configured as described above is detachably attached has a substantially cylindrical shape with the end mill main body 11 centering on the axis O, and the rear end side of the end mill main body 11 ( The upper right side in Fig. 6 and the upper side in Figs. 7 and 8 are the cylindrical shank portion 12, and the tip side of the shank portion 12 (the lower left side in Fig. 6; in Figs. 7 and 8). Is formed with a blade portion 14 to which the cutting insert is attached via a 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 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 17 drilled along the axis O from the rear end surface of the shank portion 12 toward the front end side, and the coolant hole 17 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 facing the end mill rotation direction T, a wall surface 16b extending from the bottom surface 16a toward the end mill rotation direction T and facing the tip side of the end mill body 11, and a wall surface 16c facing the outer peripheral side. In addition, a recess is formed in the blade portion 14 that opens to the tip surface and the outer peripheral surface of the end mill body 11. Screw holes 16d are formed in the bottom surface 16a, and the wall surfaces 16b and 16c have flat protruding end surfaces that are orthogonal to each other when viewed from the direction perpendicular to the bottom surface 16a and extend in a direction orthogonal to the bottom surface 16a. A ridge is formed.

  In such an insert mounting seat 16, the cutting insert has a rake face 3 on one of the polygonal faces on which the main cutting edge 5 and the corner edge 6 used for cutting are formed. In the end mill rotating direction T, the other constraining surface 3b at the center of the other polygonal surface opposite to this is brought into close contact with the bottom surface 16a, and the recessed flat central portions of the two adjacent side surfaces of the insert body 1 are wall surfaces. It is made to contact | abut on the protrusion end surface of the said protrusion part of 16b, 16c, and is seated. Then, 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, and the central part of the two side surfaces is the protruding end surface of the ridge part. Are also fixed to the insert mounting seat 16 and attached.

  The cutting insert attached in this way is protruded with the main cutting edge 5 used for the above-mentioned cutting directed toward the distal end side of the end mill body 11, and its one end 5a is positioned on the inner peripheral side of the end mill body 11 and the other end 5b. Is arranged so as to gradually extend toward the rear end side of the end mill body 11 from the one end portion 5a toward the other end portion 5b, so that a relatively small cutting angle is given to the main cutting edge 5. To be.

  Further, the corner blade 6 located on the inner peripheral side of the end mill body 11 and continuing to the one end portion 5a of the main cutting blade 5 is arranged on the inner peripheral side of the rear end of the end mill main body 11 as it is separated from the one end portion 5a of the main cutting blade 5. The periphery of the contact point between the one end portion 5a of the main cutting edge 5 and the one end portion 6a of the corner blade 6 is projected most toward the tip end side of the end mill body 11. The other corner blade 6 connected to the outer peripheral side of the end mill main body 11 of the other end 5b of the main cutting edge 5 used for this cutting is protruded to the outer peripheral side of the end mill main body 11 at the blade portion 14, and FIG. 2, the other polygonal surface of the insert body 1 is positioned on the inner peripheral side of the rotation locus around the axis O.

  Furthermore, as shown in FIG. 8, this cutting insert is directed so that the insert center line C is directed toward the rear end side in the direction of the axis O of the end mill body 11 as it goes from one polygonal surface which is a rake face to the other polygonal surface. The main cutting edge 5 used for cutting is set to a negative axial rake angle. 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. Further, the main cutting edge 5 used for this cutting is shown in FIG. 9 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 the cutting insert and the edge-exchange-type end mill having the above-described configuration, one end portion 5 a disposed on the inner peripheral side of the end mill body 11 is more than the corner blade 6 when the main cutting edge 5 is viewed from the direction facing the rake face 3. 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 one end portion 5a to the other end portion 5b. By attaching the insert main body 1 so as to extend toward the rear end side of the end mill main body 11 toward the end, the cutting angle of the main cutting edge 5 gradually increases at the one end portion 5a toward the outer peripheral side of the end mill main body 11. The end portion 5b becomes gradually smaller.

  Here, what is indicated by hatching in FIG. 10A is a cross section of the chips generated by such a main cutting edge 5, and what is indicated by hatching in FIG. 10B is described in Patent Document 2, for example. This is a cross-section of chips when the cutting angle of the main cutting edge increases toward the outer peripheral side of the end mill body as in the case of an end mill with a cutting edge attached, and the feed amount fz per cutting edge and the cutting depth The ap are equal to each other. Of these, when the cutting angle of the main cutting edge 5 gradually increases toward the outer peripheral side as shown in FIG. 10 (b), 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 the thickness is increased, the thickness is reduced to the maximum thickness t at the central portion of the main cutting edge 5, and the maximum thickness t itself is reduced. Further, in the cutting insert having the above configuration, the rake angle α5 of the main cutting edge 5 is such that the main cutting edge on the inner peripheral side of the end mill body 11 is the other end portion 5b of the main cutting edge 5 disposed on the outer peripheral side of the end mill body 11. As it goes toward the one end portion 5a of the blade 5, it is increased toward the negative angle side, and thus the blade angle of the main cutting blade 5 at the portion where the chip has the maximum thickness t can be ensured.

  For this reason, according to the cutting insert and the edge-exchange-type end mill having the above-described configuration, it is possible to reduce the cutting load acting on the main cutting edge 5 at the time of high feed processing, and in particular, the burden on the main cutting edge 5 at the cutting boundary portion. On the other hand, as described above, the cutting edge strength of the main cutting edge 5 at the portion where the chip has the maximum thickness t 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. On the other hand, since the rake angle α5 is increased to the positive angle side at the other end portion 5b of the main cutting edge 5, the cutting resistance is not increased.

  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. 10 (a), the position where the chip has the maximum thickness t is set to a position close to the central portion of the main cutting edge 5 where the one end portion 5a and the other end portion 5b are in contact. it can. 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.

  Further, 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, that is, the main cutting edge 5 has a straight portion or the like. It is a continuous uneven curve that does not have. 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.

  On the other hand, in such a blade-tip exchange type end mill, in addition to the case where the end mill main body 11 is fed in a direction perpendicular to the axis O as shown in FIG. In recent years, ramping has been increasingly performed in which the workpiece is slightly fed to the front end side in the O direction and the work material is dug down. And in such a ramping process, the one end part 5a of the main cutting edge 5 protruded to the front end side of the end mill main body 11 is cut into a work material first.

  On the other hand, in the cutting insert of the present embodiment, the rake angle α5 at the one end portion 5a of the main cutting edge 5 is increased to the negative angle side from the other end portion 5b toward the one end portion 5a, and is fixed. The angle is α5. For this reason, at the one end portion 5a of the main cutting edge 5 that is first cut into the work material as described above, the blade angle can be increased in the same way as the central portion to ensure the cutting edge strength, and the ramping process. It is also possible to prevent the main cutting edge 5 from being damaged by the impact at the time of cutting.

  In addition, in the present embodiment, the clearance angle β5 of the main cutting edge 5 is also increased toward the negative angle side from the other end 5b at the one end 5a to be 0 °. Can be further secured to improve the cutting edge strength, and damage to the main cutting edge 5 during ramping can be reliably prevented. In addition, in the ramping process, one end portion 6a of the corner blade 6 on the inner peripheral side of the end mill main body 11 connected to the one end portion 5a of the main cutting edge 5 is also cut into the work material. The rake angle α6 and the relief angle β6 of the blade 6 are also made larger at the one end portion 6a of the corner blade 6 to the negative angle side than the other end portion 6b, and in particular, the relief angle β6 is set to 0 °. Damage can also be avoided.

  By the way, the main cutting edge 5 used for cutting as described above is closer to the end mill rotation direction T side than the straight line parallel to the main cutting edge 5 and intersecting the axis O when viewed from the front end side of the end mill body 11 in the axis O direction. When the main cutting edge 5 is provided with a negative radial rake angle, the corner blade 6 on the inner peripheral side of the end mill main body 11 has a clearance angle β6 of 0 ° which remains at its one end 6a. When extending to the other end 6b, the rotation locus around the axis O of the corner blade 6 at the other end 6b is located on the outer peripheral side of the flank 4 connected to the other end 6b. There is a risk of interference with the work material.

  However, in the cutting insert of this embodiment, on the other hand, the corner blade 6 connected to the one end portion 5 a located on the inner peripheral side of the end mill body 11 of the main cutting blade 5 used for the cutting is connected to the main cutting blade 5. Since the clearance angle β6 is increased toward the positive angle side from the one end portion 6a of the corner blade 6 toward the other end portion 6b, the rotation locus of the corner blade 6 is evacuated at the other end portion 6b. Can be positioned on the inner peripheral side of the workpiece, and interference with the work material can be avoided. Therefore, it is possible to prevent unused corner blades 6 from being worn out due to interference with the work material and becoming unusable, and all the main cutting edges 5 and corners formed in one insert body 1 can be prevented. The blade 6 can be used up evenly to promote efficient and economical cutting.

  In the present embodiment, the clearance angle β6 at the one end portion 6a of the corner blade 6 is set to 0 ° as described above, and the clearance surface 4 is orthogonal to the plane perpendicular to the insert center line C. Therefore, even if the corner blade 6 side of the rake face 3 is the positive rake face 3a as described above, the blade angle of the corner blade 6 can be increased to ensure the cutting edge strength. On the other hand, even in the other end portion 6b of the corner blade 6 where the clearance angle β6 is larger on the positive side than the one end portion 6a, the clearance angle β6 is 20 ° or less in the present embodiment. In this case, it is possible to prevent the cutting edge strength from becoming too small while preventing interference with the work material.

  Further, in the present embodiment, as described above, the rake angle α5 of the one end portion 5a of the main cutting edge 5 is set to a constant angle that is increased to the negative angle side on the one end portion 5a side of the other end portion 5b. At the same time, the rake angle α6 of the corner blade 6 is also made larger at the one end portion 6a to the negative angle side than the other end portion 6b, and the clearance angles β5 and β6 are also negative angles at the one end portions 5a and 6a than the other end portions 5b and 6b. Since it is enlarged to the side, one end portion 5a of the main cutting edge 5, one end portion 6a of the corner blade 6, and the other end portion 5b of the main cutting edge 5 and the other end portion 6b of the other corner blade 6 connected thereto. The rake angle α5 and clearance angle β5 of the main cutting edge 5 and the rake angle α6 and clearance angle β6 of the corner blade 6 can be made equal to each other. For this reason, the rake face 3 (positive rake face 3a) and the flank face 4 of the insert body 1 can be smoothly and continuously provided, and a step or the like is formed on the rake face 3 or the flank face 4. It is also possible to avoid the tendency to occur.

  However, instead of setting the rake angle α5 at the one end portion 5a of the main cutting edge 5 to a constant angle that is increased toward the negative angle side toward the one end portion 5a at the other end portion 5b as described above. Like the cutting insert of the second embodiment of the present invention shown in FIGS. 11 to 13, the one end portion 5a of the main cutting edge 5 is also made to increase toward the negative angle side toward the other end portion 5b. May be. In the second embodiment shown in FIGS. 11 to 13, the same reference numerals are assigned to the parts common to the first embodiment shown in FIGS. 1 to 5 to simplify the description.

  In the cutting insert of the second embodiment configured as described above, the width of the positive rake face 3a when viewed from the direction facing the rake face 3 in the insert center line C direction is the width of the main cutting edge as shown in FIG. The width of the one end portion 5a increases toward the other end portion 5b, and the width of the other end portion 5b increases toward the one end portion 5a. In the present embodiment, the rake angle α5 at the contact point between the one end portion 5a of the main cutting edge 5 and the one end portion 6a of the corner blade 6 connected thereto, the other end portion 5a of the main cutting edge 5 and the other connected to this. The rake angle α5 at the contact point with the other end 6a of the corner blade 6 is substantially equal to each other.

  Also in the cutting insert of the second embodiment, the end mill 5 is located on the inner peripheral side of the end mill body 11 when viewed from the direction in which the main cutting edge 5 faces the rake face 3, and has an end mill shape. Since the other end portion 5b located on the outer peripheral side of the main body 11 has a concave curve shape, the position where the chip has the maximum thickness t is the position of the main cutting edge 5 between the one end portion 5a and the other end portion 5b. It can be located in the center, and the maximum thickness t itself can be reduced. And in the center part of this main cutting edge 5, since the rake angle (alpha) 5 is enlarged to the negative angle side and a cutter angle can be ensured, cutting edge intensity | strength can be raised and abnormal damages, such as chipping and a defect | deletion, can be prevented. .

  On the other hand, in this embodiment, since the rake angle α5 at both ends 5a and 5b of the main cutting edge 5 is increased to the positive angle side, the cutting resistance can be improved and the cutting resistance can be reduced. Therefore, according to the present embodiment, the end mill body 11 can be attached exclusively to the blade end replaceable end mill that feeds in the direction orthogonal to the axis O and performs high feed processing, thereby further promoting efficient cutting.

  Also in the second embodiment, as in the first embodiment, the insert body 1 has a regular polygonal plate shape, and each side ridge portion and each of the polygonal surfaces on the front and back that are regular polygons. The main cutting edge 5 and the corner edge 6 are formed at the corners, except that the polygonal surfaces on the front and back sides are slightly twisted around the insert center line C passing through the center, and the insert body 1 is turned upside down. It has a symmetrical shape. Such a cutting insert is such that the insert mounting seat 16 of the end mill body 11 is given a relatively small cutting angle to one main cutting edge 5 and the insert center line C is a rake face. The other polygonal surface is used for cutting one polygonal surface by being attached so as to extend from the polygonal surface toward the other polygonal surface toward the rear end side in the axis O direction of the end mill body 11. The main cutting edge 5 is positioned 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 the other corner cutting edges 6 connected to the outer peripheral side of the end mill main body 11 of the main cutting edge 5. It becomes possible.

  Therefore, when the main cutting edge 5 formed on the side ridge portion of one polygonal surface directed in the end mill rotation direction T is used for cutting, the main cutting edge 5 and the corner blade 6 of the other polygonal surface are not covered. Without interfering with the cutting material, the insert body 1 is rotated by 90 ° around the insert center line C and reattached to the insert mounting seat 16, and each of the four polygonal surfaces has four side ridges and corners. After the formed main cutting edge 5 and corner blade 6 are used for cutting, the insert body 1 is turned upside down and reattached to the insert mounting seat 16 so that the rake face 3 that is the other polygonal face is removed. The main cutting edge 5 and the corner edge 6 can be used for cutting in the end mill rotation direction T. For this reason, when the insert main body 1 has a square plate shape as in the first and second embodiments, a total of eight main cutting edges 5 and corner blades 6 formed on one insert main body 1 can be reliably secured. It is more efficient and economical.

  However, in these first and second embodiments, the insert body 1 is thus formed in a square plate shape. However, the insert body 1 is not limited to a cutting insert having an insert body of another regular polygonal plate shape, for example, an equilateral triangle plate shape. The invention can also be applied. Moreover, it is also possible to apply this invention to the cutting insert which has a polygon plate-shaped insert main body other than a regular polygon plate shape.

  In the first and second embodiments, as described above, the present invention is applied to a right-handed cutting insert configured to form a right blade that can be rotated counterclockwise when the blade end replaceable end mill is viewed from the front side. However, 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 the same as that of the insert body 1 of the above embodiment. It becomes a mirror-symmetrical shape. However, in either case, one end 5a of the main cutting edge 5 is arranged on the inner peripheral side of the tip of the end mill main body 11, and the other end 5b is arranged on the outer peripheral side, and one end 5a of the main cutting edge 5 is arranged. Is formed in a convex curve shape and the other end portion 5b is formed in a concave curve shape, and the rake angle α5 of the other end portion 5b is increased toward the negative angle side toward the one end portion 5a.

DESCRIPTION OF SYMBOLS 1 Insert body 2 Mounting hole 3 Rake face 3a Positive rake face 3b Restraint face 4 Relief face 5 Main cutting edge 5a One end part of the main cutting edge 5 5b Other end part of the main cutting edge 5 6 Corner edge 6a One end part of the corner edge 6 6b The other end of the corner blade 6 11 End mill main body 14 Blade portion 16 Insert mounting seat 18 Clamp screw C Insert center line O End mill main body 11 axis T End mill rotation direction α5 Rake angle of main cutting edge 5 α6 Rake angle of corner blade 6 β5 Clearance angle of main cutting edge 5 β6 Clearance angle of corner blade 6

Claims (8)

  A rake face is formed on the polygonal surface of the insert body having a polygonal plate shape, and a flank is formed on a side surface arranged around the polygonal surface, and the ridge line portion between the rake face and the flank is formed. The main cutting edge is formed on the side ridge portion of the polygonal surface, and one end portion of the main cutting edge is formed in a convex curve shape and the other end portion when viewed from the direction facing the rake face. A cutting insert, wherein the rake angle of the main cutting edge is increased toward the negative angle side toward the one end at the other end.   The cutting insert according to claim 1, wherein a rake angle of the main cutting edge is constant at the one end.   2. The cutting insert according to claim 1, wherein a rake angle of the main cutting edge is increased toward a negative angle side toward the other end portion at the one end portion.   The clearance angle of the said main cutting edge is enlarged toward the negative angle side rather than the said other end part in the said one end part, The Claim 1 characterized by the above-mentioned. Cutting insert.   The curvature radius of the concave curve which the said other end part makes larger than the curvature radius of the convex curve which the said one end part makes, The Claim 1 characterized by the above-mentioned. Cutting insert.   The cutting insert according to any one of claims 1 to 5, wherein a convex curve formed by the one end and a concave curve formed by the other end are in contact with each other.   The insert body has a regular polygonal 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 polygonal shape, and the polygonal surface on the front and back sides is the polygonal surface. The insert main body is made into a reverse-inverted symmetrical shape with respect to the polygonal surfaces of the front and back sides of the insert center line passing through the center of the insert. The cutting insert as described in any one of Claims. A cutting edge in which the cutting insert according to any one of claims 1 to 7 is detachably attached to an insert mounting seat formed at a tip portion of an end mill main body that is rotated in an end mill rotating direction around an axis. An exchangeable end mill,
The cutting insert directs the rake face in the direction of rotation of the end mill, directs the main cutting edge toward the tip side of the end mill body, and positions the one end of the main cutting edge on the inner peripheral side of the end mill body. The other end is positioned on the outer peripheral side of the end mill body, and the main cutting edge is attached so as to gradually extend toward the rear end side of the end mill body from the one end to the other end. Features a replaceable blade end mill.

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