JP2017221982A - Tip exchange type cutting tool holder and tip exchange type cutting tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To mount a cutting insert in high rigidity by preventing the looseness of a clamp screw with a small outer diameter of the tip part of a holder body.SOLUTION: An insert mount seat 5 equipped with a bottom face turning outside of a holder body 1 is formed in the outer face of the holder body 1, a projection part 6 projecting outside of the holder body 1 in the center part of the bottom face, and a clamp screw hole 7 toward inside of the holder body 1 from the projecting end face 6a of the projection part 6, and the insert mount seat 5 keeps a cutting insert with a mount hole 13 opened in the center part of two polygonal face 12 equipped with a polygonal plate insert body 11 to turn to an opposite side mounted to be detachable by bringing one polygonal face 12 in contact with the bottom face to turn the other polygonal face 12 as a flank outside of the holder body 1, and by storing the projection part 6 in the opening of the mount hole 13 of one polygonal face 12 to make the clamp screw hole 7 receive the screw-in of a clamp screw 14 inserted through the mount hole 13 from the side of the other polygonal face 12.SELECTED DRAWING: Figure 11

Description

  The present invention relates to a vertical blade type cutting edge-replaceable cutting tool holder in which a polygonal plate-shaped cutting insert is detachably mounted toward one side of the holder body with one of the two polygonal surfaces as a flank. Further, the present invention relates to a blade type replaceable cutting tool of a vertical blade type in which a cutting insert is detachably attached to the blade replaceable cutting tool holder.

  As such a vertical blade type cutting edge exchangeable cutting tool, for example, in Patent Document 1, there are two identical end faces facing each other, and a periphery extending between these end faces and having two identical main side faces facing each other. A cutting insert comprising a side surface, four main cutting blades formed at intervals between each main side surface and each end surface and spaced apart, and a primary flank adjacent to each main cutting blade, There is described a milling cutter (end mill) of an exchangeable blade tip attached to a cutter body (holder body) having at least one insert pocket for holding a cutting insert.

  In the holder for cutting edge replacement type cutting tool described in Patent Document 1, the at least one insert pocket (insert mounting seat) includes an adjacent side wall and a rear wall that substantially traverse the base (mounting seat bottom surface), and the base is A threaded hole (clamp screw hole) for receiving a clamping screw for securing the cutting insert in the insert pocket, the side wall having an axial positioning surface that abuts a given minor side of at least one cutting insert; The rear wall includes two projecting tangential positioning surfaces positioned on opposite sides of its central recessed area, which abut against a given inner end surface of the at least one cutting insert.

  Patent Document 2 includes a cutting insert as described above and an insert holder (holder body) having an insert pocket (insert mounting seat) for holding the cutting insert. The insert pocket is provided with the cutting insert. A base surface (mounting seat bottom surface) abutted by the main side surface of the first side wall, a first side wall extending upright from the base surface and abutted by a given sub-side surface of the cutting insert; And a second side wall extending upright and transverse from the base surface and the first side wall, and a fixing screw (clamp screw) extending through the insert through hole (mounting hole) as a screw on the base surface There is described a cutting edge replaceable bite in which a cutting insert is fixed to an insert pocket by screwing into a cut receiving hole (clamp screw hole).

Special table 2007-520360 gazette JP 2005-518949 A

  By the way, in such a vertical blade type cutting edge exchangeable cutting tool, a plurality of insert mounting seats are spaced apart in the circumferential direction at the tip of the holder body, particularly like the blade edge exchangeable end mill described in Patent Document 1. If the outer diameter of the tip of the holder body is reduced, the clamp screws screwed into the clamp screw holes extending from the bottom surface of the insert seats to the inner periphery of the holder body interfere with each other. Therefore, the length of the screw part of the clamp screw cannot be secured sufficiently.

  If the length of the screw part of the clamp screw cannot be secured sufficiently in this way, the contact area between the screws with the clamp screw hole is also reduced, resulting in insufficient frictional force, loosening of the clamp screw and attachment of the cutting insert. There is a risk of lack of rigidity. This is the same even when the cutting edge exchange type tool described in Patent Document 2 is used, for example, when the outer diameter of the tip of the holder main body has to be reduced in the case of performing an internal machining of a small diameter hole. .

  The present invention is made under such a background, and even when the outer diameter of the tip of the holder body on which the insert mounting seat is formed is small, the contact area between the screws of the clamp screw and the clamp screw hole It is an object of the present invention to provide a blade-tip-exchange-type cutting tool holder and a blade-tip-exchange-type cutting tool that can prevent the clamp screw from loosening and attach the cutting insert with high rigidity.

  In order to solve the above problems and achieve such an object, the holder for cutting edge replacement type cutting tool of the present invention has an insert mounting seat formed on the outer surface of the holder body, A mounting seat bottom surface facing the outside of the holder body is provided, and a convex portion that protrudes outward from the holder body is formed at the center of the mounting seat bottom surface, and the holder body from the projecting end surface of the projection portion. A clamp screw hole for mounting an insert is formed on the inside of the insert, and the insert mounting seat has a polygonal plate-like insert body and two polygons facing the opposite sides of the insert body. A cutting insert having a mounting hole that opens through the insert body at the center of the surface causes one of the two polygonal surfaces to be in close contact with the bottom surface of the mounting seat and the other. The convex surface is accommodated in the opening of the mounting hole in the one polygonal surface with the square surface as the flank and facing the outside of the holder body, and is inserted into the mounting hole from the other polygonal surface side. The clamp screw is detachably attached by being screwed into the clamp screw hole.

  Further, the cutting edge replaceable cutting tool of the present invention is a cutting edge replaceable cutting tool in which a cutting insert is detachably attached to the insert mounting seat in such a blade edge replaceable cutting tool holder by a clamp screw. The cutting insert has a polygonal plate-like insert body, and a mounting hole that penetrates the insert body is opened at the center of two polygonal surfaces facing the opposite sides of the insert body. One of the two polygonal surfaces is brought into close contact with the bottom surface of the mounting seat, and the other polygonal surface is used as a flank to face the outside of the holder body, and the mounting hole in the one polygonal surface The clamp screw inserted into the mounting hole from the other polygonal surface side is screwed into the clamp screw hole. And wherein the mounted detachably by being.

  In such a blade-tip-replaceable cutting tool holder and blade-replaceable cutting tool, a convex portion that protrudes outside the holder body is formed on the bottom surface of the mounting seat of the insert mounting seat, and the mounting hole in the insert body of the cutting insert is formed. The clamp screw hole extends to the inside of the holder main body from the protruding end surface of the convex portion. For this reason, even if the hole depth of the clamp screw hole from the bottom surface of the mounting seat is shallow, as in the case where the outer diameter of the tip of the holder body is small, it is screwed in as much as the clamp screw hole formed in the convex part. By increasing the length of the threaded portion of the clamp screw, a large contact area between the screws can be ensured.

  Therefore, according to the blade tip replaceable cutting tool holder and the blade replaceable cutting tool configured as described above, the clamp screw can be prevented from loosening and the cutting insert can be attached to the insert mounting seat with high mounting rigidity. Become. Moreover, since the protruding length of the clamp screw from the holder body is the protruding length of the protruding portion from the protruding end surface, the protruding length can be shortened, and bending of the clamp screw due to cutting load or the like can be prevented. be able to. Further, if the protrusion length is the same, the position of the bottom surface of the mounting seat can be arranged inside the holder main body, so that it is possible to cope with a further reduction in the diameter of the holder main body. Furthermore, the clearance between the cutting insert and the holder body can be reduced by the convex portion, and the inclination of the insert body can be suppressed.

  Here, in the case where the blade-tip-exchangeable cutting tool holder is a blade-tip-exchangeable end mill as described in Patent Document 1, on the outer periphery of the tip of the cylindrical holder body rotated around the axis, At least two insert mounting seats are formed at intervals in the circumferential direction, and these insert mounting seats are provided with the mounting seat bottom surfaces facing in different directions in the radial direction of the holder body, and these mounting seat bottom surfaces By forming the clamp screw hole on the inner peripheral side of the holder main body from the protruding end surface of the convex portion formed in the above, it is possible to prevent the clamp screws from interfering with each other. However, the present invention can also be applied to the cutting edge-exchangeable tool described in Patent Document 2.

  As described above, according to the present invention, even when the outer diameter of the tip of the holder body is small, the contact area between the clamp screw and the screw of the clamp screw hole can be ensured. It is possible to prevent the looseness of the cutting and the mounting rigidity of the cutting insert from being insufficient and perform stable cutting.

It is a perspective view of the tip part showing one embodiment of a holder for cutting edge exchange type cutting tools of the present invention. It is a side view of embodiment shown in FIG. It is a top view of embodiment shown in FIG. It is a front view of embodiment shown in FIG. It is ZZ sectional drawing in FIG. FIG. 6 is a perspective view of a tip portion showing an embodiment of a cutting edge-replaceable cutting tool of the present invention in which a cutting insert is attached to the cutting edge-replaceable cutting tool holder of the embodiment shown in FIGS. 1 to 5. It is a front view of embodiment shown in FIG. It is the partial fracture | rupture perspective view which fractured | ruptured the cutting insert of embodiment shown in FIG. 6 in the position corresponded to the ZZ cross section in FIG. It is a front view of the partially broken perspective view shown in FIG. It is the fracture | rupture perspective view which fractured | ruptured embodiment shown in FIG. 6 in the position corresponded to ZZ cross section in FIG. It is a front view of the fracture | rupture perspective view shown in FIG.

  FIGS. 1 to 5 show an embodiment of a holder for cutting edge replacement type cutting tool according to the present invention. FIGS. 6 to 11 show a cutting insert attached to the holder for cutting edge replacement type cutting tool of this embodiment. 1 shows an embodiment of the cutting edge exchangeable cutting tool of the present invention. These embodiments show a case where the present invention is applied to a holder for a blade-tip replaceable end mill and a blade-tip replaceable end mill as described in Patent Document 1.

  In the present embodiment, the holder main body 1 is formed in a multi-stage columnar shape centering on the axis O by a metal material such as a steel material, and a rear end portion thereof (in FIGS. 1 to 3 and FIGS. 6, 8, and 10). The right portion) is a cylindrical shank portion 2 and the tip portion (the left portion in FIGS. 1 to 3 and FIGS. 6, 8, and 10) is a cutting edge portion 3 to which a cutting insert is attached. ing. The cutting edge-replaceable cutting tool of the present embodiment is normally sent out in a direction perpendicular to the axis O while the shank portion 2 is gripped by the spindle of the machine tool and rotated around the axis O in the tool rotation direction T. The workpiece is cut by a cutting insert attached to the cutting edge portion 3.

  The cutting blade portion 3 is formed in an outer cylindrical shape having an outer diameter slightly smaller than that of the shank portion 2, and a chip pocket 4 that opens to the front end surface of the cutting blade portion 3 and extends to the rear end side is formed on the outer peripheral portion thereof. In addition, on the side opposite to the tool rotation direction T of the chip pocket 4, an insert mounting seat 5 communicating with the chip pocket 4 is opened to the front end surface and the outer peripheral surface, which are also the outer surfaces of the cutting blade portion 3. It is formed as a recess. In this embodiment, two chip pockets 4 and two insert mounting seats 5 are formed at 180 ° rotational symmetry with respect to the axis O at equal intervals in the circumferential direction.

  The insert mounting seat 5 has a mounting seat bottom surface 5a facing the outer peripheral side (outside) of the holder body 1 and a mounting seat wall surface facing the tool rotating direction T on the opposite side of the tool seating bottom surface 5a from the tool rotating direction T. 5b and a mounting seat wall surface 5c which is located on the rear end side of the mounting seat bottom surface 5a and faces the front end side of the holder main body 1. Therefore, the mounting seat bottom surfaces 5 a of the two insert mounting seats 5 face each other in the radial direction of the holder body 1. Further, the corners between the mounting seat bottom surface 5a and the mounting seat wall surfaces 5b and 5c and between the mounting seat wall surfaces 5b and 5c, and the intersection ridge line portion between the mounting seat bottom surface 5a and the mounting seat wall surface 5c and the chip pocket 4. A concave relief portion for avoiding interference with the cutting insert is formed at the intersecting ridge line portion between the mounting seat wall surfaces 5b and 5c and the outer peripheral surface of the cutting blade portion 3.

  The mounting seat bottom surface 5a and the mounting seat wall surfaces 5b and 5c are formed in a flat shape except for the convex portion 6 of the mounting seat bottom surface 5a described below. Among these, the mounting seat bottom surface 5a has the largest area, and the mounting seat wall surfaces 5b and 5c become smaller in order. In the present embodiment, the mounting seat bottom surface 5a is formed in a substantially parallelogram shape as shown in FIG. 2, and the mounting seat wall surfaces 5b and 5c are formed in a substantially rectangular shape as shown in FIGS. .

  And the convex part 6 which protrudes in the outer peripheral side (outside) of the holder main body 1 perpendicularly | vertically from the attachment seat bottom face 5a which makes the substantially parallelogram planar shape as mentioned above is formed in the center part of the attachment seat bottom face 5a. A clamp screw hole 7 for mounting an insert is formed from the protruding end surface 6a facing the outer peripheral side of the convex portion 6 toward the inner peripheral side (inner side) of the holder body 1. As shown in FIG. 5, the clamp screw holes 7 of the two insert mounting seats 5 are eccentric to the tool rotation direction T side at equal intervals from the axis O. However, the hole bottom portions communicate with each other.

  Moreover, the convex part 6 in this embodiment protrudes perpendicularly | vertically from the attachment seat bottom face 5a in the substantially annular shape or C shape centering on the centerline of the clamp screw hole 7, The cross section along this centerline is substantially. However, a part thereof is cut away by the relief portion between the mounting seat bottom surface 5a and the mounting seat wall surface 5b. The cross section of the convex portion 6 may have a trapezoidal shape or the like that becomes wider as it goes toward the mounting seat bottom surface 5a with the outer peripheral side of the convex portion 6 being a hypotenuse. Furthermore, the protruding height of the convex portion 6 from the mounting seat bottom surface 5a is sufficiently smaller than, for example, the inner and outer diameters of the convex portion 6.

  The cutting insert attached to the insert mounting seat 5 of the holder main body 1 is a polygonal plate formed by a hard material such as a cemented carbide having a hardness higher than that of the holder main body 1, more specifically, a substantially parallelogram plate shape. That is, the insert body 11 includes two polygonal surfaces (parallelogram surfaces) 12 facing each other and two arranged around each of the polygonal surfaces 12. With a long side and a short side.

  An attachment hole 13 that penetrates through the insert body 11 is opened at the center of the two polygonal surfaces 12. The insert body 11 is detachably attached to the insert attachment seat 5 by screwing the clamp screw 14 inserted through the attachment hole 13 into the clamp screw hole 7.

  Here, the parallelogram formed by the two polygonal surfaces 12 is a parallelogram formed by the other polygonal surface 12 on the opposite side of the acute angle portion of the parallelogram formed by the one polygonal surface 12. The obtuse corner is positioned. Such an insert body 11 is formed in a 180 ° rotationally symmetric shape with respect to the center line of the mounting hole 13, and is formed in a reverse-inverted symmetrical shape with respect to the two polygonal surfaces 12.

  Furthermore, a main cutting edge having a rake face on the long side surface is formed at the cross ridge line portion between each polygonal surface 12 and the long side surface, and at least the acute angle corner portion of the cross ridge line portion between the long side surface and the short side surface On the side, a secondary cutting edge having a rake face on the long side is formed. Accordingly, the polygonal surface 12 serves as a flank of the main cutting edge used for cutting formed at the intersection ridge line portion with the long side surface. The central portion of the polygonal surface 12 and the bottom surface of the long side surface are formed in a substantially flat shape. In addition, the area of each surface is the largest on the polygonal surface 12, followed by the long side and the short side in this order.

  Further, the mounting hole 13 is formed so as to decrease in diameter from the opening in the two polygonal surfaces 12 toward the inside of the insert body 11. Further, the opening portions of the mounting holes 13 in the polygonal surfaces 12 are sized to accommodate the heads of the clamp screws 14 and the convex portions 6 on the mounting seat bottom surface 5a of the insert mounting seat 5, that is, the inner diameter. And depth.

  In such a cutting insert, the convex surface 6 is accommodated in the opening of the mounting hole 13 on the one polygonal surface 12 side of the insert main body 11, and the one polygonal surface 12 is brought into close contact with the mounting seat bottom surface 5a. In addition, the other polygonal surface 12 is directed to the outer peripheral side of the holder body 1 as a flank (peripheral flank), one long side is directed in the tool rotation direction T, and the other long side is opposed to the mounting seat wall 5b. Further, one short side surface is directed to the tip end side of the holder body 1 and the other short side surface is seated on the insert mounting seat 5 so as to face the mounting seat wall surface 5c.

  Then, by screwing the clamp screw 14 inserted into the mounting hole 13 as described above from the other polygonal surface 12 side into the clamp screw hole 7, the one polygonal surface 12 is pressed against the mounting seat bottom surface 5a, The bottom surface of the other long side surface and the other short side surface are brought into contact with the mounting seat wall surfaces 5 b and 5 c, respectively, and the cutting insert is attached to the insert mounting seat 5. At this time, the screw portions of the clamp screw 14 screwed into the clamp screw holes 7 of the two insert mounting seats 5 have lengths that do not interfere with each other, and the head of the clamp screw 14 is the other polygon of the insert body 11. It is accommodated in the opening of the mounting hole 13 on the surface 12 side.

  In the thus configured vertical blade type holder for cutting edge-exchangeable cutting tool (end mill) and cutting edge-exchangeable cutting tool (endmill), the intersecting ridge line between the other polygonal surface 12 and one long side surface and one short side surface. The main cutting edge and the auxiliary cutting edge formed in the part are used for cutting. At this time, the polygonal surface 12 having the largest area extending so as to be orthogonal to the direction of the smallest thickness of the polygonal plate-like insert body 11 (the direction of the center line of the mounting hole 13) is the main cutting edge. Since it is arranged along the tool rotation direction T on which the cutting load acts, it is possible to ensure the cutting edge strength of the main cutting edge particularly used for cutting and perform high-precision cutting.

  Further, in the blade-tip-exchangeable cutting tool holder and the blade-tip-exchangeable cutting tool configured as described above, the convex portion 6 is formed on the mounting seat bottom surface 5a facing the outer periphery of the holder body 1 of the insert mounting seat 5 as described above. In the state where the cutting insert is attached to the insert mounting seat 5, the convex portion 6 is accommodated in the opening of the mounting hole 13 of the insert main body 11, and the clamp screw 14 into which the clamp screw 14 for fixing the insert main body 11 is screwed. The hole 7 extends from the protruding end surface 6 a of the convex portion 6 to the inner peripheral side of the holder body 1.

  For this reason, even when the outer diameter of the cutting edge portion 3 at the tip of the holder body 1 is small and the hole depth from the mounting seat bottom surface 5a to the bottom of the clamp screw hole 7 cannot be increased, The length of the screw portion of the clamp screw 14 to be screwed into the clamp screw hole 7 is increased by the length of the screw of the clamp screw hole 7 formed on the inner periphery (for example, about 1 to 2 threads). Thus, the contact area between the clamp screw hole 7 and the clamp screw 14 can be increased. Therefore, it is possible to prevent the clamp screw 14 from being loosened due to a decrease in the contact area between the screws and the insufficient frictional force, and it is possible to attach the cutting insert with high mounting rigidity, which is stable. Cutting can be performed.

  Further, by forming such a convex portion 6 and forming the clamp screw hole 7 from the protruding end surface 6a, the protruding length of the clamp screw 14 from the holder body 1 is the protruding length from the protruding end surface 6a. Thus, the protruding length can be shortened as compared with the case where the clamp screw hole 7 is directly opened on the mounting seat bottom surface 5a without the convex portion 6 being formed. For this reason, it is possible to prevent the clamp screw 14 from being bent due to a cutting load or the like, and to perform more stable and highly accurate cutting.

  On the other hand, if the protruding length is the same as the case where the clamp screw hole 7 is directly open on the mounting seat bottom surface 5a, the position of the mounting seat bottom surface 5a is the same as the protruding height of the convex portion 6 compared to this case. The holder main body 1 can be disposed on the inner peripheral side. Therefore, according to the blade tip replaceable cutting tool holder and the blade replaceable cutting tool configured as described above, the diameter of the tip of the holder body 1 is further reduced while maintaining the contact area between the clamp screw hole 7 and the clamp screw 14. It becomes possible. Furthermore, by reducing the clearance between the inner wall surface of the mounting hole 13 of the cutting insert and the outer peripheral surface of the convex portion 6, unexpected movement of the insert body 11 in the insert mounting seat 5 can be suppressed.

  In addition, the blade-tip-exchangeable cutting tool holder and the blade-tip-exchangeable cutting tool of the present embodiment have two insert mounting seats 5 on the outer periphery of the distal end portion of the cylindrical holder body 1 that is rotated around the axis O as described above. Are end blade holders and end mills of an exchangeable blade tip, which are formed at intervals in the circumferential direction with the respective mounting seat bottom surfaces 5a facing away from each other, and the cutting inserts are detachably attached by the clamp screws 14, respectively.

  In particular, in the case of a small-diameter-blade replaceable end mill, when the cutting insert is attached to the plurality of insert mounting seats 5 in this way, the clamp screw 14 is likely to interfere, but by applying the present invention, even with a small diameter. Interference between the clamp screws 14 can be prevented while maintaining a contact area with the clamp screw hole 7. Of course, this is the same even when there are three or more insert mounting seats 5 formed in the holder body 1.

  On the other hand, in addition to the blade end replaceable end mill holder and the blade end replaceable end mill in which a plurality of insert mounting seats 5 are formed on the holder main body 1 in this way, one insert mounting seat in the circumferential direction on the outer periphery of the tip end portion of the holder main body 1 In the single-blade blade-end replaceable end mill holder and the blade-tip replaceable end mill, which are only formed, a holder between the mounting seat bottom surface 5a and the outer peripheral surface of the cutting blade portion 3 on the opposite side in order to reduce the diameter. The present invention is effective when the thickness of the main body 1 must be small.

  Furthermore, in addition to such a blade-tip replaceable end mill holder and end mill, the blade-tip replaceable cutting tool holder and the blade-tip replaceable cutting tool described in Patent Document 2 are also used, for example, to carry out small-diameter hole machining. The present invention is effective when the diameter of the tip of the holder body 1 is reduced. In addition, for example, an insert mounting seat is provided in the circumferential direction and the axial line on the two circular side surfaces, outer peripheral surface, and inner peripheral surface (outer surface) of a thin disc-shaped or annular plate-shaped holder main body (cutter main body) rotated about the axis. Cutting edge replacement of vertical blade type, which is formed alternately in the direction, and a polygonal plate-like cutting insert is mounted on these insert mounting seats with one of the two polygonal surfaces as the flank face in the axial direction Thickness from the bottom of the mounting seat of the insert mounting seat to the side of the holder body on the opposite side (inner side) in the axial direction, even in the case of a side cutter, external or internal pin mirror cutter holder body and side cutter or pin mirror cutter The present invention is effective when it is difficult to ensure. Further, in the above-described embodiment, the main cutting edge is disposed so as to extend substantially parallel to the axis O as shown in FIG. 6, for example. However, in the present invention, the main cutting edge is, for example, 45 ° with respect to the axis O. It is applicable also to the holder and milling machine of the face mill which inclined so that it may go to an inner peripheral side as it goes to the front end side at this angle.

DESCRIPTION OF SYMBOLS 1 Holder main body 2 Shank part 3 Cutting edge part 4 Tip pocket 5 Insert mounting seat 5a Mounting seat bottom 5b, 5c Mounting seat wall surface 6 Convex part 6a Protruding end face of convex part 7 Clamp screw hole 11 Insert main body 12 Insert body 11 Rectangular surface 13 Mounting hole 14 Clamp screw O Axis of holder body 1 T Tool rotation direction

Claims (3)

An insert mounting seat is formed on the outer surface of the holder body, and this insert mounting seat is provided with a mounting seat bottom surface facing the outside of the holder body,
A convex portion that protrudes outside the holder body is formed at the center of the bottom surface of the mounting seat, and a clamp screw hole for attaching an insert is formed from the protruding end surface of the convex portion toward the inside of the holder body. Formed,
The insert mounting seat has a polygonal plate-like insert main body, and a cutting insert having a mounting hole opened through the insert main body at the center of two polygonal surfaces facing opposite sides of the insert main body, Of the two polygonal surfaces, one polygonal surface is brought into close contact with the bottom surface of the mounting seat and the other polygonal surface is used as a relief surface toward the outside of the holder body so that the mounting hole in the one polygonal surface is Cutting edge replacement characterized in that the convex portion is accommodated in the opening, and the clamp screw inserted into the attachment hole from the other polygonal surface side is removably attached by being screwed into the clamp screw hole. Type cutting tool holder.   At least two insert mounting seats are formed on the outer periphery of the tip of the cylindrical holder body that rotates about the axis with a circumferential interval, and these insert mounting seats have a diameter of the holder body. 2. The blade tip replaceable cutting tool holder according to claim 1, wherein the mounting seat bottom faces facing in directions different from each other are provided. A cutting edge replaceable cutting tool in which a cutting insert is detachably attached to the insert mounting seat in the holder for cutting edge replaceable cutting tool according to claim 1 or 2, by a clamp screw,
The cutting insert has a polygonal plate-like insert body, and a mounting hole that penetrates the insert body is opened at the center of two polygonal surfaces facing opposite sides of the insert body.
The cutting insert has one of the two polygonal surfaces in close contact with the bottom surface of the mounting seat and the other polygonal surface serving as a flank toward the outside of the holder body, The convex portion is accommodated in the opening portion of the mounting hole, and the clamp screw inserted into the mounting hole from the other polygonal surface side is detachably mounted by being screwed into the clamp screw hole. A cutting edge exchangeable cutting tool characterized by comprising:

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