JP2014193491A - Tip replaceable rotary cutting tool and cutting insert using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tip replaceable rotary cutting tool and cutting insert using te same, capable of suppressing chips from clogging between two cutting inserts.SOLUTION: A cutting insert 50 is a tip replaceable rotary cutting tool, including a tool body 10 rotatable around a rotation axial line C, and the cutting insert 50 which is detachably attached to a tip end region of the tool body 10. At least two cutting inserts 50 are present at positions of rotational symmetry about the rotation axial line C. The cutting insert 50 includes an outer blade 51 extending to an outer peripheral side from the rotation axial line C side, and an inner blade 52 which is connected to the outer blade 51 and is arranged on the rotation axial line C side. When viewed from the tip end side of the tool, the inner blade 52 of at least one of the cutting inserts 50 is convexed toward the rotation axial line C.

Description

  The present invention relates to a cutting tool exchangeable rotary cutting including a tool body rotatable around a rotation axis, and two cutting inserts each having a main cutting edge and detachably disposed in a tip region of the tool body. The present invention relates to a tool and a cutting insert used for the tool.

  The so-called two-blade type blade-replaceable drill can perform cutting at a higher speed than a solid carbide drill. Such a two-blade type blade-tip replaceable drill is disclosed in, for example, Patent Document 1. A blade-tip replaceable drill disclosed in Patent Document 1 includes a main body that can rotate around a rotation axis, two chip seats disposed in a tip region of the main body, and a drill tool that is replaceably attached to the chip seat. And a cutting insert that forms a central gap opposite to each other across the axis.

US Pat. No. 7,575,400

  By the way, each of the two cutting inserts has an outer peripheral cutting edge (hereinafter referred to as an outer cutting edge) and a central cutting edge portion (hereinafter referred to as an inner cutting edge) following this, and an inner cutting edge with a rotation axis interposed therebetween. It arrange | positions so that the terminal part of each may oppose. For this reason, the drill diameter of the blade-tip-exchangeable drill to which this cutting insert can be applied is determined by the length of the cutting edge from the outer peripheral side to the end portion of the inner blade. In other words, it is difficult to use the same cutting insert in common for tool bodies having a low degree of freedom in arrangement and slightly different drill diameters. If the inner blade portion of the cutting insert overlaps in the direction of decreasing the drill diameter, the drill diameter can be slightly adjusted. However, if the inner blade portions overlap each other, there is a problem that chips are easily clogged in a narrow gap formed between the overlapping portions of the inner blades. For this reason, the adjustment range of the drill diameter is actually limited.

  The present invention can be used in common for rotary cutting tools of various drill diameters, and can also prevent clogging of chips between two or more cutting inserts, and a cutting insert used therefor. I will provide a.

  The cutting edge exchange type rotary cutting tool of the present invention is a cutting edge exchange type rotary cutting tool having a tool body rotatable around a rotation axis and a cutting insert detachably attached to a tip region of the tool body. The cutting insert has at least two rotationally symmetric positions with respect to the rotation axis, the cutting insert is connected to the outer blade extending from the rotation axis side to the outer peripheral side, the outer blade, and the rotation axis. An inner blade disposed on the side, and when viewed from the tip end side of the tool, at least one of the inner blades of the cutting insert is curved convexly with respect to the rotation axis. To do.

  The cutting insert of the present invention is a cutting insert that is detachably disposed at a plurality of positions around the rotation axis in the tip region of the tool body that is rotatable around the rotation axis. Is formed in a plate shape, and a cutting edge is formed at an intersection ridge line between at least one of the upper surface or the lower surface and the outer peripheral side surface, the cutting blade having an outer blade and an inner blade inclined with respect to the outer blade, A first abutting surface formed on the outer peripheral side surface and parallel to each other, and formed between the two first abutting surfaces and having a central axis parallel to the first abutting surface A through hole, a second contact surface formed on the upper surface and the lower surface, respectively, and a second contact surface parallel to each other; and formed so as to protrude from the second contact surface in at least one of the upper surface or the lower surface; Inclined with respect to the contact surface of the A first rake face connected to the first rake face, a second rake face connected to the inner blade and inclined to a different direction from the first rake face; A second flank formed on the same surface as the first abutment surface and intersecting the first rake face, and formed on the outer peripheral side surface and intersecting the second rake face. And at least one of the inner blades is curved in a convex shape when viewed from a direction facing the second flank.

  According to the present invention, when mounting the same cutting insert on a tool body of various drill diameters, the amount of overlapping of the inner blades can be easily adjusted in a state where two or more inner blades face each other with the rotation axis interposed therebetween. Therefore, the degree of freedom of arrangement of the cutting insert is high. For this reason, it becomes possible to deal with tools having various drill diameters. Further, according to the present invention, since at least one inner blade of the two or more cutting inserts is convexly curved with respect to the rotation axis, chips formed at the center of the tool are laterally moved. Easier to escape and can prevent clogging between cutting inserts

The front view which looked at the front-end | tip part of the blade-tip-exchange-type rotary tool which concerns on the 1st Embodiment of this invention from the rotating shaft direction. The side view of the blade-tip-exchange-type rotary cutting tool seen from the direction along the Y plane of FIG. The side view of the blade-tip-exchange-type rotary cutting tool seen from the direction along the X plane of FIG. The side view of the blade-tip-exchange-type rotary cutting tool seen from the D direction of FIG. The front view of the cutting insert which concerns on the 1st Embodiment of this invention. The top view of the cutting insert of FIG. The right view of the cutting insert of FIG. The left view of the cutting insert of FIG. Sectional drawing of the AA line direction of the cutting insert of FIG. The perspective view from one direction of the cutting insert of FIG. The perspective view from the other direction of the cutting insert of FIG. The front view which looked at the front-end | tip part of the tool main body which concerns on the 1st Embodiment of this invention from the rotating shaft direction. The side view of the tool main body seen from the direction along the Y plane of FIG. The side view of the tool main body seen from the direction along X plane of FIG. The perspective view from one direction of the tool main body of FIG. The perspective view from the other direction of the tool main body of FIG. It is a front view which shows the 1st modification of the 1st Embodiment of this invention. It is a front view which shows the 2nd modification of the 1st Embodiment of this invention. It is a front view of the cutting insert used for the cutting tool of FIG. The front view which looked at the front-end | tip part of the blade-tip-exchange-type rotary cutting tool which concerns on the 2nd Embodiment of this invention from the rotation axis direction. The side view of the blade-tip-exchange-type rotary cutting tool seen from the direction along the Y plane of FIG. The side view of the blade-tip-exchange-type rotary cutting tool seen from the direction along the X plane of FIG. The front view of the cutting insert which concerns on the 2nd Embodiment of this invention. The bottom view of the cutting insert of FIG. The rear view of the cutting insert of FIG. The right view of the cutting insert of FIG. It is a perspective view of the bottom face side of the cutting insert of FIG. It is a perspective view from the other direction of the bottom face side of the cutting insert of FIG.

Hereinafter, embodiments of the present invention will be described in detail.
1st Embodiment With reference to FIGS. 1-16, the blade-tip-exchange-type rotary cutting tool and cutting insert which concern on 1st Embodiment of this invention are demonstrated. In addition, the blade-tip-exchange-type rotary cutting tool according to the present embodiment is a rotary cutting tool capable of drilling, and is used as a drill, for example. “Perforating” means that cutting can be performed in a direction parallel to the rotation axis C of the rotary tool. That is, a cutting edge is required from the outer periphery to the vicinity of the rotation axis C at the tip portion of the rotary cutting tool.

  The cutting edge exchange type rotary cutting tool according to this embodiment includes a tool main body 10 that can rotate around a rotation axis C extending in the longitudinal direction, and a rotational symmetry about the rotation axis C at a tip region of the tool main body 10 by approximately 180 degrees. There are two cutting inserts 50 that are detachably arranged and mounted at various positions, and a clamping screw SC for attaching each cutting insert 50 to the tool body 10.

  In the first embodiment, the two cutting inserts 50 are negative type cutting inserts having the same shape. As shown in FIGS. 5 to 11, the cutting insert 50 is formed in a plate shape and includes first to third contact surfaces 81, 83, and 85. These three surfaces are in contact with first to third seat surfaces 21, 23, 25 of the tool body 10, which will be described later. The first contact surface 81 is formed on the outer peripheral side surface of the cutting insert 50, and is two flat surfaces parallel to each other. The second contact surfaces 83 are formed on the upper surface and the lower surface of the cutting insert 50, respectively, and are parallel to each other. As shown in FIGS. 6 and 8, the third contact surface 85 is a surface formed at two locations on the outer peripheral side surface of the cutting insert 50. However, the first to third contact surfaces 81, 83, 85 are not limited to flat surfaces, and may be curved surfaces in other embodiments. That is, as long as the shape is in contact with the first to third seating surfaces 21, 23, and 25 formed on the tool body 10, any shape may be used.

  The cutting insert 50 includes a through hole 90 for attaching the cutting insert. The through hole 90 is formed so as to penetrate the upper and lower surfaces, and has a central axis AX parallel to the first contact surface 81.

  A first rake face 61 is formed on the upper and lower surfaces of the cutting insert 50. The first rake face 61 is formed so as to protrude from the second contact surface 83, and is inclined with respect to the second contact surface 83. Specifically, as shown in FIG. 5, the first rake face 61 is inclined in a direction away from the cutting insert 50 from the left end side to the right end side of the cutting insert 50.

  The second rake face 62 is connected to a connection region 63 that is the most protruding portion of the first rake face 61, and is inclined with respect to the second abutting face 83 in a direction different from the first rake face 61. ing. Specifically, the second rake face 62 is inclined toward the bottom surface side of the cutting insert 50 as the distance from the connection region 63 increases. A part of the second rake face 62 intersects with the second contact face 83.

  By connecting the first rake face 61 and the second rake face 62 via the connection region 63, the shape of the cutting edge changes smoothly, and the cutting insert becomes difficult to chip. In another embodiment, the connection region 63 is not provided, and the first rake face 61 and the second rake face 62 may be directly connected. However, if the first rake face and the second rake face are directly connected, the ridgeline becomes a corner, which tends to cause the cutting insert to be chipped.

  Between the first rake face 61 and the second abutment surface 83, and between the second rake face 62 and the second abutment surface 83, the second rake face 83 is inclined. An inclined surface 65 is interposed. Further, notched inclined surface portions 69 are formed on the upper and lower surfaces of the cutting insert 50 in order to prevent a part of the cutting insert 50 from projecting from the outer periphery of the tool body 10 and interfering with the workpiece after processing. Has been.

  The first contact surface 81 intersects the first rake surface 61 and becomes a flank (first flank) of the outer blade 51 described later. The first contact surface 81 is smoothly connected to a connection surface 82 that is curved outward of the cutting insert 50, and the connection surface 82 is connected to a second flank 71 that intersects the second rake surface 62. It is connected.

  The outer blade 51 that cuts the outer peripheral side during drilling and the inner blade 52 that cuts the central side are the outer peripheral surfaces connecting the first contact surface 81, the connection surface 82, and the second flank 71. And the first rake face 61, the rake face connecting region 63, and the rake face connecting the second rake face 62.

  As shown in FIG. 2, the outer blade 51 is a part of the intersecting ridge line portion between the first contact surface 81 and the first rake surface 61 and the intersecting ridge line portion between the connection surface 82 and the first rake surface 61. The part which is comprised and is extended substantially linearly from the outer peripheral side of the tool main body 10 corresponds.

  On the other hand, the inner blade 52 is constituted by a part of the intersecting ridge line portion between the connection surface 82 and the first rake face 61 and the intersecting ridge line portion between the second flank 71 and the second rake face 62. The part extending in a different direction corresponds to this. That is, the inner blade 52 corresponds to a portion extending from the side where the outer blade 51 is disposed to the X plane and the Y plane, crossing the X plane and the Y plane shown in FIG.

  Between the outer blade 51 and the inner blade 52, there is a connecting portion that connects the two cutting blades. More intuitively using FIG. 1, the portion extending linearly from the right (left) outer periphery of the tool body 10 toward the rotation axis C is the outer blade 51, and the rotation axis is bent from the outer blade 51. The portion that passes in the vicinity of C is the inner blade 52.

  The X plane is defined as a plane that includes the rotation axis C and passes through the outermost end of any one of the outer blades 51 serving as a reference. The Y plane is defined as a plane that includes the rotation axis C and is orthogonal to the X plane.

  The cutting insert 50 is 180-degree rotationally symmetric with respect to a symmetry axis J that is orthogonal to the central axis AX and parallel to the first contact surface 81. Therefore, the cutting insert 50 can be used twice upside down. Here, as shown in FIG. 7, the inner blade 52, which is an intersection of the second rake face 62 and the second flank 71, as viewed from the direction of the symmetry axis J, is directed toward the rotational axis C. Curved in a convex shape. Although not shown, the inner blade 52 is curved in a convex shape when viewed from the direction facing the second flank 71. As will be described later, this is a configuration for suppressing the clogging of chips into a narrow gap formed between the overlapping portions of the inner blades.

  As shown in FIGS. 12 to 16, the tool main body 10 has two protrusions 11 at positions where the tip end thereof is 180 degrees rotationally symmetric with respect to the rotation axis C. The protrusion 11 is formed by cutting out the tip of the tool body 10 along the shape of the cutting insert 50.

  The two projecting portions 11 are formed with a first seat surface 21 with which the first abutting surface 81 of each cutting insert 50 abuts, and a screw hole penetrating the first seat surface 21. 40 is formed. The first seat surfaces 21 face each other across the rotation axis C and are parallel to the rotation axis C. The surface extending between the two protrusions 11 is a second seat surface 23 formed of an inclined surface (plane) that is rotationally symmetrical by 180 degrees with respect to the rotation axis C. The second seating surface 23 is inclined toward the rear end side of the tool body 10 as it goes radially outward from the rotation axis C side. Therefore, the angle formed by the plane including the first seating surface 21 and the plane including the second seating surface 23 corresponding thereto is an acute angle. With this configuration, when the cutting insert 50 is fastened with the fastening screw SC, the cutting insert 50 is securely clamped. Moreover, when the main component force is added to the cutting insert 50 because the angle formed by the first seating surface 21 and the second seating surface 23 is an acute angle, the rear side of the tool body 10 of the cutting insert 50. It is suppressed that the edge part located in is floating. The third seating surface 25 is formed in the vicinity of the second seating surface 23 and is a flat surface inclined so as to face the second seating surface 23 side. The wall portion 26 that constitutes the third seating surface 25 and faces the outer peripheral direction of the tool main body 10 functions to protect the outer blade 51.

  A recess 30 having a concave curved surface extending along the first seat surface 21 is formed between the plane including the first seat surface 21 and the second seat surface 23 corresponding thereto. This recessed part 30 is for covering and protecting the one of the two cutting edges of the cutting insert 50 that is not used for cutting. By covering at least the outer blade 51 with the concave portion 30, it is possible to prevent the cutting blade that is not used during the cutting process from being damaged. In this embodiment, the recess 30 is formed as a groove shape. Moreover, in another embodiment, the recessed part 30 can also be made into the shape which covers the whole cutting blade which is not used during cutting.

  Further, on the outer peripheral surface of the tool body 10, two spiral chip conveying grooves 15 are formed in the longitudinal direction. The chip conveying groove 15 is continuous with a concave curved surface 24 adjacent to the second seat surface 23 shown in FIG. As shown in FIG. 13, the curved surface 24 is located immediately below the inner blade 52 in a direction parallel to the rotation axis C. By this curved surface 24, chips generated by the inner blade 52 are smoothly guided to the chip conveying groove 15.

  The inner blades 52 of the two cutting inserts 50 are arranged so as to face each other across the rotation axis C when viewed from the tip, and are convex so that the tops of both inner blades 52 face the rotation axis C. It is curved. That is, when viewed from the tip, the two inner blades 51 are arranged at positions that are approximately 180 degrees rotationally symmetric with respect to the rotation axis C, and the interval GP1 between the inner blades 51 gradually increases as the distance from the rotation axis C increases in the radial direction. Has expanded to. Since the inner blades 52 of the two cutting inserts 50 face each other, a cylindrical non-cutting portion is formed between the two inner blades 52 during the cutting process.

  Further, as shown in FIG. 4, when viewed from the D direction, the interval GP2 between the second rake faces 62 that form the inner blades 52 of the two cutting inserts and that face each other is parallel to the rotation axis C. Is gradually enlarged toward the tool body 10 side. That is, the gap GP2 becomes wider from the front end side (upper drawing) of the tool main body 10 toward the rear end side (lower drawing) of the tool main body 10. The D direction is a direction along a plane passing through the rotation axis C between the second rake faces 62 facing each other and between the inner blades 52 facing each other. The “D direction” defined as described above is not limited to one, but the interval GP2 gradually increases toward the tool body 10 when viewed from all the directions defined as described above. It is formed to do.

  As shown in FIG. 2, the two second flank surfaces 71 respectively forming the inner blades 52 of the two cutting inserts 50 are directed toward the rear end side of the tool body 10 toward the rear in the rotational direction of the rotary cutting tool. Inclined, and further toward the rear end side of the tool body 10 as it approaches the rotation axis C side.

  In the present embodiment, a gap is formed between the two inner blades 52 around the rotation axis C. For this reason, a cylindrical non-cutting part is formed in the center of the tool during the cutting process. When this cylindrical non-cutting portion is pushed by the blade-replaceable rotary tool and removed from the work, it is likely to clog the gap between the cutting inserts normally. However, in this embodiment, the gap GP1 is set as described above. Since it expands gradually as it leaves | separates from the rotating shaft C in the radial direction, it becomes easy to discharge | emit toward the outer peripheral side. Further, since the gap GP2 between the second rake faces 62 is also enlarged toward the tool main body 10 side, chips are not easily clogged in this direction. Thus, since the gap formed between the cutting inserts has a shape that expands in two directions at the same time, the cutting edge-preferred rotary cutting tool of this embodiment is a conventional cutting edge replaceable rotary cutting tool. More efficient chip removal.

  Further, as shown in FIG. 2, the two second flank surfaces 71 are inclined toward the rear end side of the tool body 10 as approaching the rotation axis C side, so It dents to the rear end side and does not interfere with the hole bottom.

  FIG. 17 is a first modification of the first embodiment. The tools shown in FIGS. 17A and 17B are obtained by attaching common cutting inserts to different tool bodies 10A and 10B. In FIG. 17, the same reference numerals are used for the same components as those in the first embodiment. The tool diameter of the tool body 10B shown in FIG. 17B is larger than the tool diameter of the tool body 10A shown in FIG. That is, since the cutting insert 50 according to the present embodiment places the two inner blades 52 facing each other across the rotation axis C, the cutting of the outer blade 51 is performed within a range where the inner blades 52 face each other across the rotation axis C. You can change the maximum diameter possible. In particular, in the present embodiment, since the inner blade 52 is curved in a convex shape, the range in which the two inner blades 52 can be opposed to each other with the rotation axis C interposed therebetween is greater than the case where the inner blade is linear. Is also wide.

  18 and 19 show a second modification of the first embodiment. In FIGS. 18 and 19, the same reference numerals are used for the same components as those in the first embodiment.

  As shown in FIGS. 18 and 19, a chip splitter 100 is formed on the first contact surface 81 of each cutting insert 50B. The chip splitter 100 is also called a nickname. The chip splitter 100 is a concave groove formed in the first contact surface 81 and extends in the thickness direction of the cutting insert 50. The formation position of one chip splitter 100 and the formation position of the other chip splitter 100 are not 180-degree rotationally symmetric with respect to the symmetry axis J. By adopting such a configuration, the arrangement of the two chip splitters 100 can be varied in the radial direction of the tool body 10 as shown in FIG. Can cut chips, improving chip cutting efficiency.

Second Embodiment Next, with reference to FIGS. 20 to 28, a blade edge replaceable rotary cutting tool and a cutting insert according to a second embodiment of the present invention will be described. 23 to 28, the same reference numerals are used for the same components as those in the first embodiment.

  The difference between the second embodiment and the first embodiment is the shape of the cutting insert. The two inner blades 52 and 52A of the cutting insert 50A according to the present embodiment have different shapes and are asymmetric with respect to the above-described symmetry axis J.

  Specifically, in the cutting insert 50A according to the present embodiment, the second rake face 62 having the same shape as that of the first embodiment is formed on the upper surface, and the shape of the second rake face 62 is formed on the lower surface. A different third rake face 62A is formed. The third rake face 62A is connected in the connection region 63 of the first rake face 61, and is inclined in a direction different from that of the first rake face 61 and curved in a concave shape. A fourth rake face 62B is formed adjacent to the third rake face 62A, which is a flat surface. Further, a second flank 71 intersecting with the second rake face 62 and a third flank 71A having a different shape from the second flank 71 intersecting with the third rake face 62A are formed on the side surfaces. Has been. And the 1st inner blade 52 of the same shape as the inner blade of 1st Embodiment is formed in the intersection of the 2nd rake face 62 and the 2nd flank 71, and the 3rd rake face 62A and A second inner blade 52A having a shape different from that of the first inner blade 52 is formed at the intersection with the third flank 71A and at the intersection between the fourth rake face 62B and the third flank 71A. ing.

  As described in the first embodiment, the first inner blade 52 is curved in a convex shape toward the rotation axis C as seen from the direction of the symmetry axis J. As shown in FIG. The inner blade 52A is formed of a concavely curved portion and a linear portion when viewed from the direction of the symmetry axis J. That is, by making the shape of the third rake face 62A different from the shape of the fourth rake face 62B, the second inner blade 52A is formed by a curve curved in a concave shape with respect to the straight line and the rotation axis C. . At this time, the shortest distance from the second inner blade 52A to the rotation axis C is longer than the distance from the first inner blade 51 to the rotation axis C. That is, the second inner blade 52A is offset in the radial direction, and is disposed on the radially outer side than the first inner blade 52.

  When the first inner blade 51 and the second inner blade 52A are asymmetrically offset in the radial direction, the diameter of the cylindrical chip formed at the center of the tool is the same as that of the first inner blade 51. It is defined by the distance from the rotation axis C. For this reason, a gap is formed between the offset second inner blade 52A and the cylindrical chip. As a result, chips are less likely to be clogged between the first inner blade 51 and the second inner blade 52A.

  Moreover, since the cylindrical chip formed in the center part of the blade-tip-exchange-type rotary cutting tool of the present embodiment receives force only from the first inner blade 51, the cylindrical chip, particularly the cylindrical non-cutting A bending force to be folded can always be applied to the part. Thereby, columnar chips are easily discharged in the outer peripheral direction of the tool body 10.

  In the above embodiment, the case where the present invention is applied to a drill has been described. However, the present invention is not limited to this. For example, a feed is given in the rotational axis direction such as a plunging tool or an end mill with a bottom blade. However, any tool that cuts can be used.

  In the first embodiment, both inner blades have the same shape, but when both inner blades are convex curves and one inner blade is compared with the other inner blade, one inner blade It is also possible to adopt a shape in which the shortest distance from the rotation axis to the rotation axis is longer than the shortest distance on the other side.

  Moreover, in the above-described embodiments, each has two blades, but the blade-tip-exchange-type rotary cutting tool of the present invention can be configured to have three or more cutting inserts.

  The outer blade is also a straight line in the above embodiment, but may be formed in a concave curve shape that curves in a direction in which the thickness of the cutting insert decreases. When the outer blade has such a shape, a force to bend the generated chip from the side can be generated, so that the chip is easily subdivided.

  Definitions relating to terms used in this specification are also explained. In the present invention, “the inner blade and the inner blade face each other across the rotation axis” means that the inner blades are close to each other to the extent that they function as a cutting edge-exchangeable rotary cutting tool, and the gap formed by the two inner blades That is, at least one of the openings is formed to spread from the center toward the outer periphery.

  In the present invention, “in the vicinity of the rotation axis C” means that the inner blade is close to the rotation axis C to such an extent that it functions as a cutting edge of a blade-cutting-type rotary cutting tool capable of drilling.

DESCRIPTION OF SYMBOLS 10 ... Tool body 15 ... Chip conveyance groove 50 ... Cutting insert 51 ... Outer blade 52 ... Inner blade 71 ... Second flank surface 61 ... First rake surface 62 ... Second rake surface 62A ... Third rake surface 62B ... Fourth rake face 63 ... Rake face connection area 81 ... First contact face (first flank face)
82 ... Connection surface 83 ... Second contact surface 85 ... Third contact surface 21 ... First seat surface 23 ... Second seat surface 25 ... Third seat surface SC ... Tightening screw C ... Rotation axis AX ... Center axis

Claims (15)

A cutting edge replaceable rotary cutting tool having a tool body rotatable around a rotation axis, and a cutting insert removably attached to a tip region of the tool body,
The cutting insert has at least two rotationally symmetric positions with respect to the rotation axis, the cutting insert is connected to the outer blade extending from the rotation axis side to the outer peripheral side, the outer blade, and the rotation axis side An inner blade disposed on
An edge-replaceable rotary cutting tool characterized in that at least one of the inner blades of the cutting insert is curved in a convex shape with respect to the rotational axis when viewed from the tip side of the tool body.   Two cutting inserts are mounted, and the distance between the facing rake faces of the inner blade of the cutting insert is perpendicular to the rotational axis and when viewed from the direction in which both rake faces are visible, The blade-tip-exchange-type rotary cutting tool according to claim 1, which expands toward the rear end side.   The length of the inner cutter is 10% or more and 40% or less of the length of the cutting insert of the cutting insert, and the flank of the inner cutter is moved toward the rear in the rotational direction of the rotary cutting tool. The blade tip replacement type according to claim 1 or 2, wherein the blade tip is inclined toward the rear end side and is inclined toward the rear end side of the tool body as it approaches the rotation axis side. Rotary cutting tool.   When viewed from the direction of the rotation axis, the inner blades of the cutting insert are both convexly curved with respect to the rotation axis, and are disposed at rotationally symmetric positions with respect to the rotation axis. 4. The blade-tip-exchange-type rotary cutting tool according to claim 1, wherein the interval gradually increases with increasing distance from the rotation axis in the radial direction. 5. Each of the cutting inserts is formed in a plate shape,
A first abutting surface formed on the outer peripheral side surface that is parallel to each other and abuts against the first seat surface of the tool body;
A through-hole for attaching a cutting insert formed between the two first contact surfaces and having a central axis parallel to the first contact surface;
A second contact surface formed on each of the upper surface and the lower surface, parallel to each other and contacting the second seating surface of the tool body;
A first rake face that is formed on the upper surface and the lower surface so as to protrude from the second contact surface, is inclined with respect to the second contact surface, and is connected to the outer blade;
A second rake face formed on each of the upper face and the lower face, connected to the first rake face, inclined in a direction different from the first rake face, and connected to the inner blade;
A first flank formed as the same surface as the first contact surface and intersecting the first rake surface;
A second flank surface formed on each of the outer peripheral side surfaces and intersecting with the second rake face;
5. The cutting insert according to claim 1, wherein each of the cutting inserts is 180 degrees rotationally symmetric with respect to a symmetry axis perpendicular to the central axis and parallel to the first contact surface. The cutting edge exchange type rotary cutting tool as described.   The blade tip exchange type rotary cutting tool according to claim 5, wherein the inner blade is curved in a convex shape when viewed from a direction facing the second flank. Two cutting inserts are mounted, and an inner blade of one of the two cutting inserts is curved in a convex shape with respect to the rotation axis, and an inner blade of the other cutting insert is formed in a straight line. Or formed in a concave curve with respect to the rotation axis,
4. The shortest distance from the inner blade of the other cutting insert to the rotation axis is longer than the distance from the inner blade of the one cutting insert to the rotation axis. 5. The cutting edge exchange type rotary cutting tool described in 1. Each of the two cutting inserts is formed in a plate shape,
A first abutting surface formed on the outer peripheral side surface that is parallel to each other and abuts against the first seat surface of the tool body;
A through-hole for attaching a cutting insert formed between the two first contact surfaces and having a central axis parallel to the first contact surface;
A second contact surface formed on each of the upper surface and the lower surface, parallel to each other and contacting the second seating surface of the tool body;
A first rake face that is formed on the upper surface and the lower surface so as to protrude from the second contact surface, is inclined with respect to the second contact surface, and is connected to the outer blade;
A second rake face formed on an upper surface of the cutting insert, connected to the first rake face, and inclined in a direction different from the first rake face;
A third rake face formed on a lower surface of the cutting insert, connected to the first rake face, and inclined in a direction different from the first rake face;
A first flank formed as the same surface as the first contact surface and intersecting the first rake surface;
A second flank formed on the outer peripheral side and intersecting the second rake face;
A third flank formed on the outer peripheral side surface and intersecting the third rake face;
A first inner blade is formed at the intersection of the second rake face and the second flank face,
A second inner blade is formed at the intersection of the third rake face and the third flank face,
The first inner blade is curved in a convex shape when viewed from the direction facing the second flank.
The said 2nd inner blade is formed in linear form seeing from the direction which opposes the said 3rd flank, or is curving in concave shape, It is characterized by the above-mentioned. The cutting edge exchangeable rotary cutting tool. The tool body has a first seat surface on which the first contact surface of the cutting insert abuts, and a second seat surface on which the second contact surface of the cutting insert abuts, respectively.
The concave portion for covering and protecting at least the outer blade on the side not used for cutting is formed between the first seat surface and the corresponding second seat surface. The blade-tip-exchange-type rotary cutting tool according to any one of 1 to 3.   4. The cutting edge replacement type rotary cutting tool according to claim 1, wherein an angle formed between the first seating surface and the corresponding second seating surface is an acute angle. 5. Chip splitters extending to the upper and lower outer blades are formed on each of the first flank surfaces,
4. The formation position of the chip splitter on one of the first flank surfaces and the formation position of the chip splitter on the other first flank surface are different from each other. The cutting edge exchange type rotary cutting tool according to any one of the above. A cutting insert that is detachably disposed at a plurality of positions around the rotation axis in the tip region of the tool body that can rotate around the rotation axis,
The cutting insert is formed in a plate shape, and a cutting edge is formed on an intersecting ridge line between at least one of the upper surface or the lower surface and the outer peripheral side surface, and the cutting blade includes an outer blade and an inner blade inclined with respect to the outer blade. Have
First contact surfaces formed on the outer peripheral side surface and parallel to each other;
A through hole formed between the two first contact surfaces and having a central axis parallel to the first contact surface;
A second contact surface formed on each of the upper surface and the lower surface and parallel to each other;
A first rake face that is formed so as to protrude from the second contact surface on at least one of the upper surface and the lower surface, is inclined with respect to the second contact surface, and is connected to the outer blade When,
A second rake face connected to the first rake face, inclined in a direction different from the first rake face, and connected to the inner blade;
A first flank formed as the same surface as the first contact surface and intersecting the first rake surface;
A second flank surface formed on the outer peripheral side surface and intersecting the second rake face,
The cutting insert, wherein when viewed from a direction facing the second flank, at least one of the inner blades is curved in a convex shape.   The cutting insert according to claim 12, wherein the cutting insert is 180-degree rotationally symmetric with respect to an axis of symmetry perpendicular to the central axis and parallel to the first contact surface. The second rake face is formed on an upper surface of the cutting insert;
A third rake face formed on a lower surface of the cutting insert, connected to the first rake face, and inclined in a direction different from the first rake face;
A third flank formed on the outer peripheral side surface and intersecting with the third rake face;
A first inner blade is formed at the intersection of the second rake face and the second flank face,
A second inner blade is formed at the intersection of the third rake face and the third flank face,
The first inner blade is curved in a convex shape when viewed from the direction facing the second flank.
The said 2nd inner blade is formed in linear form seeing from the direction which opposes the said 3rd flank, or is curving in concave shape, It is characterized by the above-mentioned. Cutting inserts. Chip splitters extending to the upper and lower outer blades are formed on each of the first flank surfaces,
The formation position of the chip splitter on one of the first flank surfaces and the formation position of the chip splitter on the other first flank surface are not 180-degree rotationally symmetric with respect to the symmetry axis. The cutting insert according to claim 12, characterized in that:

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