JP2008000840A - Cutting insert and rotary cutting tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cutting insert for flange work capable of reducing cutting resistance, improving cutting blade strength in accordance with the cutting resistance, restraining chattering vibration in working and defect of a cutting blade even in heavy cutting work under a more serious cutting condition and displaying an excellent chip discharging property. <P>SOLUTION: This cutting insert makes a roughly polygonal plate shape, is furnished with a rake face on an upper surface, a seating face on a lower surface and a flank on a side surface and has a main cutting blade formed on an intersection crest line part of the rake face and the flank, and the main cutting blade is constituted of a plurality of divided main cutting blades divided by at least one groove part formed on the flank, a plurality of the divided main cutting blades are constituted of one end side divided main cutting blade including one end of the main cutting blade and a separated divided main cutting blade separated from the one end of the main cutting blade, and the separated divided main cutting blade is formed so that cutting blade length gradually increases toward the other end side from the one end side of the main cutting blade. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a cutting insert and a rolling tool provided with the cutting insert, and more particularly to a rolling tool used for a plunge machining tool.

  As a recent trend in the machining industry, various tools have been developed to further improve the efficiency of cutting work.

  For example, Patent Document 1 discloses a plunge grinding milling machine in which many cutting inserts are mounted on a holder. Such a plunge grinding mill can mount a large number of cutting inserts on the holder by forming the cutting insert pockets in a specific shape. Thereby, the improvement of cutting efficiency can be aimed at.

Further, Patent Document 2 discloses a cutting insert in which the rake face with respect to the main cutting edge has a positive rake angle while being attached to the holder, and the flank face is divided by the groove together with the main cutting edge. Yes. With such a cutting insert, the cutting resistance during cutting can be reduced, and chatter vibration during processing can be suppressed even in heavy cutting with more severe cutting conditions. Therefore, cutting efficiency can be improved.
JP 2004-202686 A JP 7-299636 A

  However, when the plunge grinding mill described in Patent Document 1 is used under more severe cutting conditions with a large depth of cut for further efficiency, the cutting resistance applied to the cutting insert is further increased. There is a problem that it becomes difficult to sufficiently suppress chatter vibration in the inside, and the cutting edge of the cutting insert is easily damaged. In particular, the cutting edge on the inner peripheral side with a low cutting speed has a problem that a large cutting resistance is applied and chipping is likely to occur.

  In addition, when cutting inserts with a long cutting edge length are used for plunge machining in order to increase the efficiency of the cutting operation, the difference in cutting speed at both ends of the cutting edge increases, so that the chip at both ends of the cutting edge Differences in length and curl diameter also increase. Therefore, in such a processing form, by using the cutting insert described in Patent Document 2, even if cutting resistance can be reduced, chips are easily entangled, chip dischargeability is deteriorated, and tool life is shortened. There was a problem that.

  The present invention has been made to solve such problems of the prior art, and is used in a turning tool, in particular, a plunge machining tool having a long cutting edge length and a large number of cutting edges attached thereto. An object of the present invention is to provide a cutting insert that reduces cutting resistance, suppresses chipping of a cutting edge, and exhibits stable chip discharge.

  In order to solve the above problems, the cutting insert of the present invention has a substantially polygonal plate shape, and includes a rake face on the upper surface, a seating surface on the lower surface, and a flank surface on the side surface, and the rake face and the flank face. A cutting insert consisting of a plurality of divided main cutting edges, wherein the main cutting edge is formed at the intersecting ridge line portion, and the main cutting edge is divided by at least one groove portion formed on the flank surface, The plurality of divided main cutting edges are composed of one end-side divided main cutting edge including one end of the main cutting edge, and a separated divided main cutting edge that is separated from one end of the main cutting edge. The length of the cutting edge is gradually increased from one end side to the other end side of the main cutting edge.

  With such a configuration, the separated divided main cutting edge gradually increases in cutting edge strength from one end side to the other end side of the main cutting edge, so that the cutting resistance applied to each cutting edge portion gradually increases. Therefore, it is possible to suppress cutting edge defects that are likely to occur. In addition, since the width of the chips generated by each divided main cutting edge gradually increases, chips having different chip lengths and curl diameters can be discharged well. As a result, variation in cutting resistance applied to each cutting edge portion in the cutting insert can be reduced, chatter vibration and chipping of the cutting edge can be suppressed, and chip discharge performance can be improved.

  Furthermore, the one end side divided main cutting edge is formed to be substantially the same as the cutting edge length of the adjacent separated divided main cutting edge, thereby improving the cutting edge strength of the one end side divided main cutting edge. Chipping and the like can be suppressed.

  A plurality of the groove portions are formed, and the plurality of groove portions are formed so that the width of the groove portion in the top view of the insert is gradually increased from one end side to the other end side of the main cutting edge. Thus, the strength of the entire cutting insert can be improved from the one end side of the main cutting edge to the other end side, and the tool life can be further extended.

  Further, the plurality of groove portions are formed so that the maximum width of the width of the groove portion in the side view of the insert gradually increases from one end side to the other end side of the main cutting edge. Since it corresponds to the groove portion, it is possible to suppress the interference between the uncut portion generated on the processed surface of the work material and the cutting insert without being cut during cutting, and the cutting resistance can be reduced.

  Further, the plurality of divided main cutting edges are formed so as to be gradually inclined so as to approach the seating surface from one end side to the other end side of the main cutting edge, so that one end of the main cutting edge is formed. As it goes from the side to the other end side, the sharpness can be gradually improved, and chipping and the like can be suppressed.

  Further, the plurality of divided main cutting edges are formed such that a rake angle gradually increases from one end side to the other end side of the main cutting edge, so that the other end from the one end side of the main cutting edge The strength of the cutting edge can be gradually improved toward the side, and chipping and the like can be suppressed even under severer cutting conditions.

  Further, since at least one protrusion is formed on the rake face corresponding to each of the divided main cutting edges, chips generated by the divided main cutting edges are transferred to the corresponding protrusions. Since the chips are brought into contact with each other and the chips are effectively curled, the size of the chips can be reduced, and the chips can be efficiently discharged out of the tool, thereby improving chip discharge performance.

  Further, the rolling tool of the present invention comprises a holder having a substantially cylindrical shape and the cutting insert according to any one of claims 1 to 6, wherein the main cutting edge is located on the tip surface side of the main body part, The cutting insert is mounted on the holder so that one end of the main cutting edge is positioned on the outer peripheral side of the holder.

  With such a configuration, the cutting edge strength of each divided main cutting edge is formed so as to gradually increase. Therefore, even in a machining mode in which the cutting resistance varies depending on the cutting edge part, such as plunge machining, the cutting edge is not damaged. Can be suppressed. In addition, since the width of the chips is generated so as to gradually increase, it is possible to reduce the variation in the chip weight of the chips generated by each divided main cutting edge, and to cut the chips with different lengths and curl diameters. It is possible to improve the chip dischargeability of scrap.

Still further, the rolling tool of the present invention is a rolling tool comprising a substantially cylindrical body part and a tip blade formed on the tip side of the body part, wherein the tip blade is at least The plurality of small cutting blades are composed of a plurality of small cutting blades separated by one concave portion, and the plurality of small cutting blades are separated from an outer peripheral side small cutting blade located on the outer periphery of the main body portion, and are separated from the outer periphery of the main body portion. Consisting of a blade,
The spaced small cutting edges are formed such that the cutting edge length gradually increases from the outer peripheral side to the inner peripheral side of the main body portion. Even if resistance is applied to each small cutting edge, it is possible to suppress chipping of the cutting edge and chatter vibration, and it is possible to reduce variation in chip weight of the chips generated by each small cutting edge. . As a result, it is possible to improve the machining surface accuracy and improve the chip discharging property.

  Further, a plurality of the recesses are formed, and the plurality of recesses are formed so that the width gradually increases from the outer peripheral side of the main body toward the inner peripheral side, so that the holder outer periphery side and inner Even in plunge machining under severe cutting conditions where the strength balance on the circumferential side is good and the cutting resistance is large, chipping of the cutting edge and chatter vibration can be suppressed.

  According to the cutting insert of the present invention, the main cutting edge is formed of a plurality of divided main cutting edges divided by the groove portion, and the separated divided main cutting edge that is separated from one end of the main cutting edge is the main cutting edge. As the cutting edge length gradually increases from one end side to the other end side, the cutting resistance during cutting is reduced, and the cutting edge strength is gradually increased according to the cutting resistance applied to each cutting edge portion. In addition, it is possible to reduce the variation in chip weight of chips having different chip lengths and curl diameters. Therefore, it is possible to realize a cutting insert having a long tool life that can suppress chatter vibration and chipping and also exhibits excellent chip discharge performance.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  1A and 1B show an embodiment of the present invention. FIG. 1A is a plan view and FIG. 1B is a side view of a long side of a cutting insert (hereinafter abbreviated as an insert) 1 according to a first embodiment of the present invention. It is. FIG. 2 is an enlarged view of a main part of the insert 1. FIG. 3 is an overall perspective view (a) and (b) of the rolling tool 11 using the insert 1 of the present invention.

  FIG. 4 is a (a) side view and (b) bottom view of a rolling tool 21 showing a second embodiment of the present invention.

  In FIG. 1, an insert 1 according to the first embodiment has a substantially polygonal plate-like main body, specifically, a substantially parallelogram-like plate, and has a seating surface 2 on the lower surface of the main body and a rake surface on the upper surface. 3 and a flank 4 on the side. And the main cutting edge 5 is formed in a part of intersection ridgeline part of the scoop surface 3 and the flank 4.

  Here, a plurality of groove portions 6 are arranged in parallel on the flank 4 with one end on the rake face 3. The main cutting edge 5 is divided into a plurality of divided main cutting edges 7 by the groove 6. As shown in FIG. 1A, the plurality of divided main cutting edges 7 are separated from one end-side divided main cutting edge 71 including one end 5 ′ of the main cutting edge and one end 5 ′ of the main cutting edge. It consists of a divided main cutting edge 72. That is, the one-end-side divided main cutting edge 71 is a divided main cutting edge located on the most one end side of the main cutting edge 5 among the divided main cutting edges 7. The separated divided main cutting edge 72 is a divided main cutting edge other than the one end side divided main cutting edge 71 among the divided main cutting edges 7. In FIG. 1A, the direction from the center of the main cutting edge 5 to the one end 5 'of the main cutting edge is shown as one end side direction X, and the direction toward the other end is shown as the other end side direction Y.

  FIG. 3 is an overall perspective view of the rolling tool 11 to which the insert 1 according to the first embodiment of the present invention is mounted. Here, the cutting tool 11 is configured such that the insert 1 is mounted on the holder 12 so that one end side X of the main cutting edge 5 is positioned on the outer peripheral side of the holder 12. Therefore, in a state where the insert 1 is mounted on the holder 12, the one end side divided main cutting edge 71 is positioned on the outermost peripheral side of the holder 12 among the plurality of divided main cutting edges 7. Moreover, the cutting tool 11 is equipped with a plurality of cutting inserts, and by cutting complementarily with the plurality of cutting inserts, it is possible to perform a cutting process with the processing surface being a substantially flat surface.

  As illustrated in FIGS. 1A and 1B, the insert 1 has a gradually increasing cutting edge length as the separated divided main cutting edge 72 moves from one end side X to the other end side Y of the main cutting edge 5. It is formed to increase. As a result, even when the cutting resistance at the time of cutting differs at each cutting edge portion as in plunge machining, an insert having a cutting edge strength corresponding to the cutting resistance can be obtained. For example, in the case of using the rolling tool 12 for plunge processing shown in FIG. 3, the cutting speed gradually decreases as the distance from the holder outer peripheral side toward the holder inner peripheral side increases. In the insert 1 of the present invention, the separated main cutting edge 72 is formed so that the length of the cutting edge gradually increases, so that the cutting edge strength of the main cutting edge 5 corresponding to such a change in cutting resistance gradually increases. A cutting edge configuration can be obtained.

  Further, since the separated divided main cutting edge 72 is configured to gradually increase the cutting edge length, the width of the chips generated by the separated divided main cutting edge 72 is also gradually increased accordingly. Therefore, even when the cutting speed on the holder inner peripheral side and the holder outer peripheral side are different as in plunge processing, and the length and curl diameter of the chips generated on the holder inner peripheral side and the holder outer peripheral side are different accordingly. By making the widths of the chips generated by the separate divided main cutting edges 72 different, the chip dischargeability can be improved. In other words, the cutting edge length arranged on the holder outer circumference side with a larger cutting speed and a longer chip length is reduced, and the cutting edge length arranged on the holder inner circumference side with a smaller cutting speed and a shorter chip length. By increasing the thickness, it is possible to reduce the variation in the chip weight of the chips generated by each separated divided main cutting edge 72. As a result, it is possible to suppress the chips generated by each separated divided main cutting edge 72 from being clogged in the chip pocket 13 or from being entangled with each other, and to improve the chip dischargeability. In particular, in heavy cutting where the amount of cutting is large and the chip size of the generated chips is larger, it is possible to reduce the variation in the chip size of the generated chips and The tool life can be effectively lengthened by improving the scrap discharging property.

  Furthermore, under cutting conditions where the feed amount in the radial direction is smaller than the length of the main cutting edge 5, the cutting material has a cutting edge structure in which the cutting edge strength gradually increases like the insert 1. It is possible to suppress boundary wear and boundary damage that are likely to occur at the cutting edge portion that contacts the boundary surface.

  Furthermore, the cutting resistance at the time of cutting can be reduced by dividing the main cutting edge 5 with the groove part 6 and comprising a plurality of divided main cutting edges 7. Therefore, it is possible to suppress chatter vibration and chipping even in continuous cutting where cutting force is always applied during cutting and heavy cutting under severe cutting conditions where higher cutting resistance is applied, and to improve the machining surface accuracy. Can do.

  Furthermore, as shown in FIGS. 1A and 1B, the one-end-side divided main cutting edge 71 is formed to be substantially the same as the cutting edge length of the adjacent separated divided main cutting edge 72 '. Thereby, in the state with which the holder 12 was mounted | worn, the cutting edge intensity | strength of the one end side division | segmentation main cutting edge 71 most located in the outer peripheral side of a holder can be enlarged, and chipping can be suppressed effectively.

  Further, as illustrated in FIG. 1A, the insert 1 has a gradually increasing width W of the groove portion in the top view of the insert as the plurality of groove portions 6 move from one end side X to the other end side Y of the main cutting edge 5. It is desirable to be formed to increase. Thereby, the protrusion amount of the cutting edge portion of each divided main cutting edge 7 protruding outward from the wall surface 8 of the groove is adjusted according to the cutting resistance having gradually different sizes applied to each divided main cutting edge 7. The strength of the insert 1 can be further stabilized. Therefore, chipping and the like can be further suppressed.

  Moreover, the insert 1 is mounted | worn with and used for the circumferential direction of the holder 12, as shown in FIG. At this time, a plurality of cutting inserts are mounted on the holder 12 so as not to leave uncut portions on the processed surface of the work material. At this time, a plurality of groove portions 6 are formed in the main cutting edge 5 so that the width W of the groove portion gradually increases in the insert 1 as described above, whereby one insert 1 (A) cuts the work material after cutting. The uncut portion generated on the processing surface is formed so as to gradually increase from the holder outer peripheral side toward the holder inner peripheral side. Therefore, the second insert B adjacent to the holder circumferential direction of the insert 1 (A), which cuts the uncut portion, adjusts the balance of the cutting resistance of each divided main cutting edge when the uncut portion is cut. can do. That is, since the uncut portion is generated so as to gradually increase from the holder outer peripheral side toward the holder inner peripheral side, the cutting edge length of each divided main cutting edge contributing to the cutting of the insert B also gradually increases accordingly. . As a result, in each of the plurality of inserts mounted on the rolling tool 12, each divided main cutting is performed from the holder outer peripheral side toward the holder inner peripheral side according to different cutting speeds on the holder outer peripheral side and inner peripheral side. The cutting edge strength of the blade can be gradually increased. Furthermore, it is possible to suppress variations in the chip weight of the chips generated by the divided main cutting edges having different chip lengths and curl diameters. Therefore, while maintaining the cutting edge strength according to such cutting resistance, chip discharge | emission property can be improved and a tool life can be lengthened.

  In addition, the width W of the groove part in the top view of the insert is a dimension in the longitudinal direction of the insert 1 in the groove part 6 as illustrated in FIG. That is, in the top view of the insert (when the top surface of the insert is projected onto a surface parallel to the seating surface 2), 2 of the intersecting ridge line portion 8 between the wall surface 8 of the groove and the rake surface 3 and the virtual straight line of the main cutting edge 5. The distance between two intersections. The wall surface 8 of the groove means a series of surfaces connected to the rake face 3 and the flank face 4. As shown in FIG. 2, when the insert 1 is viewed from above, the insert 1 has two convex curves 8 ′ and 8 ″ that are close to the flank 4 at the intersection ridgeline between the wall surface 8 of the groove and the rake face 3. The width W of the groove in the case of having the following is as follows: The distance between the intersection S of each tangent at both ends of the convex curve 8 ′ and the intersection T of each tangent at both ends of the convex curve 8 ″ is the width W of the groove. And

  Further, as shown in FIG. 1B, the plurality of groove portions 6 gradually increase from one end side X to the other end side Y of the main cutting edge 5 so that the maximum width Ws of the groove portions in the side view of the insert gradually increases. It is desirable to form so as to increase. Thereby, since it corresponds to the groove portion of the insert 1, it is possible to suppress the interference between the uncut portion generated on the processed surface of the work material and the wall surface 8 of the groove portion of the insert 1 without being cut during cutting. Resistance can be reduced.

  Further, the plurality of divided main cutting edges 7 are preferably formed so as to be gradually inclined so as to approach the seating surface 2 from the one end side X to the other end side Y of the main cutting edge 5. Thereby, as it goes to the other end side Y from the one end side X of the main cutting edge 5, the sharpness is improved and chipping and the like can be suppressed. Specifically, when the insert 1 is mounted on the holder so that the radial rake has a negative value, the radial rake gradually increases so as to approach zero as it goes from the holder outer peripheral side to the holder inner peripheral side. Configured. Thereby, the sharpness of the holder inner peripheral side can be improved and cutting resistance can be reduced.

  Furthermore, it is desirable that the plurality of divided main cutting edges 7 be formed such that the rake angle gradually increases from one end side X to the other end side Y of the main cutting edge 5. Thereby, as it goes from the one end side X of the main cutting edge 5 to the other end side Y, the cutting edge strength increases and chipping and the like can be suppressed. Specifically, the axial rake is configured to gradually increase from the holder outer peripheral side toward the holder inner peripheral side when the insert 1 is mounted on the holder so that the axial rake has a negative value. Thereby, the biting to the work material in the holder outer peripheral side can be improved.

  Furthermore, it is desirable that at least one protrusion 9 is formed on the rake face 3 corresponding to each divided main cutting edge 7. Thereby, each chip | tip produced | generated with each division | segmentation main cutting edge 7 can be made to contact the corresponding projection part 9, and a chip | tip can be curled. Therefore, the chip size of the chips discharged from the tool body can be further reduced. As a result, it is possible to prevent chips from being entangled with the chip pocket 13 and from entanglement between the chips generated by the respective divided main cutting edges 7, thereby further improving the chip discharge performance.

  Next, the cutting tool 21 which is 2nd embodiment of this invention is demonstrated using FIG. The rolling tool 21 shown in FIG. 4 has a main body portion 22 having a substantially cylindrical shape, and a blade portion 28 is brazed to the distal end side of the main body portion 22. The blade portion 28 includes a tip blade 25 on the tip side, and the tip blade 25 has a plurality of small cutting blades 27 separated by at least one recess 26. The plurality of small cutting edges 27 includes an outer peripheral side small cutting edge 271 located on the outer periphery of the main body 22 and a separated small cutting edge 272 spaced from the outer periphery of the main body 22.

  As shown in FIG. 4, the cutting tool 21 of the present invention includes a plurality of small cutting edges 27, each of which has a cutting edge length as the separated small cutting edges 272 move from the outer peripheral side to the inner peripheral side. It is formed to increase gradually. With such a configuration, it is possible to gradually increase the cutting edge strength of the separated small cutting edge 272 according to the cutting resistance applied to the tip edge, which gradually increases from the outer peripheral side toward the inner peripheral side. Therefore, chipping of each separated small cutting edge 272 can be suppressed. Further, since the chip width of the generated chips gradually increases corresponding to the gradually increasing cutting edge length of the spaced small cutting edges 272, each of the separated small cutting edges having different chip lengths and curl diameters. It is possible to suppress the variation in chip weight of the chips generated at 272. As a result, it is possible to obtain a turning tool with improved tool life and improved tool life.

  Further, the rolling tool 21 is preferably formed with a plurality of recesses 26, and the plurality of recesses 26 are formed so that the width w gradually increases from the outer peripheral side of the main body portion toward the inner peripheral side. . Thereby, in the rolling tool 21 in which a plurality of tip blades 25 are formed and these tip blades 25 complementarily cut the work material, any tip blade 25 is directed from the outer peripheral side to the inner peripheral side. Thus, the cutting edge strength of each small cutting edge 27 is formed to gradually increase. Accordingly, it is possible to stabilize the balance of cutting resistance applied to each tip blade 25 at the time of cutting, and to suppress chipping in any tip blade 25. Furthermore, it is possible to suppress variation in the chip weight of the chips generated by the small cutting blades 27 having different chip lengths and curl diameters, and improve chip discharge performance.

  Note that the width w of the recess 26 of the rolling tool 21 is the distance between the small cutting edges 27 in a plan view perpendicular to the direction in which the tip edge 25 extends, as shown in FIG. is there. Specifically, it can be calculated in the same manner as the groove width W described above.

  Here, FIG. 1 illustrates the insert 1 in which the main body portion has a substantially parallelogram plate shape, but as another embodiment of the present invention, the main body portion has a substantially square plate shape and a substantially rhombus shape corresponding to the holder shape. It goes without saying that the same effect can be obtained even if it is formed in a plate shape or the like. Furthermore, in the present embodiment, the shape of the groove portion 6 is exemplified only that the one end is scooped on the face 3 and the other end is located on the seating face 2. However, the present invention is not limited to this, and the insert requires a large insert strength. When used for such cutting, the other end of the groove 6 may be located on the flank 4. Thereby, the improvement of insert strength can be aimed at.

  In addition, the formation position of the groove 6 in the main cutting edge 5 can obtain the effect of the present invention even if it is not formed over the entire area of the main cutting edge 5, but in order to reduce the cutting resistance more effectively, It is desirable to form over the entire area of the main cutting edge 5 as in this embodiment. Thereby, this effect can be effectively obtained even in heavy cutting under more severe cutting conditions.

  Furthermore, as illustrated in FIG. 3, two types (1A and 1B) of a rolling tool used by mounting a plurality of cutting inserts are illustrated. At this time, by making the arrangement of the groove portions of the two types of inserts different from each other, complementary cutting is performed and the work surface of the work material is flattened. However, the number and the type of are not limited to this. What is necessary is just to have the groove part arrangement | positioning which is mounted | worn with a holder so that the part cut with each insert and the uncut part can be complementarily covered, and a processing surface becomes flat.

  As mentioned above, although embodiment of this invention was illustrated, this invention is not limited to embodiment, It cannot be overemphasized that it can be made arbitrary, unless it deviates from the objective of invention.

It is (a) top view of the cutting insert by 1st embodiment of this invention, (b) Long side side view. It is a principal part enlarged view of the cutting insert 1 of FIG. It is a whole perspective view (a) and (b) of a turning tool using a throw away insert of the present invention. It is (a) side view and (b) bottom view of the rolling tool of this invention.

Explanation of symbols

1 Cutting insert (insert)
2 Seating surface 3 Rake face 4 Flank 5 Main cutting edge 6 Groove 7 Divided main cutting edge 71 One end side divided main cutting edge 72 Separately divided main cutting edge 8 Groove wall 9 Projection 11 Rolling tool 12 Holder 13 Chip pocket 21 Cutting Tool 22 according to Second Embodiment Main Body 25 Tip Blade 26 Concave 27 Small Cutting Edge 271 Outer Small Cutting Blade 272 Separated Small Cutting Blade 28 Blade Part W: Width of Groove w: Width of Concave

Claims (10)

It has a substantially polygonal plate shape,
With a rake face on the upper surface, a seating surface on the lower surface, and a relief surface on the side surface,
A main cutting edge is formed at an intersection ridge line portion between the rake face and the flank face, and the main cutting edge is composed of a plurality of divided main cutting edges divided by at least one groove portion formed on the flank face. A cutting insert,
The plurality of divided main cutting edges are composed of one end-side divided main cutting edge including one end of the main cutting edge, and a separated divided main cutting edge spaced from one end of the main cutting edge,
The spacing insert main cutting edge is formed so that the cutting edge length gradually increases from one end side to the other end side of the main cutting edge.   2. The cutting insert according to claim 1, wherein the one end side divided main cutting edge is formed to be substantially the same as a cutting edge length of the adjacent divided division main cutting edge.   A plurality of the groove portions are formed, and the plurality of groove portions are formed such that the width of the groove portion in the top view of the insert gradually increases from one end side to the other end side of the main cutting edge. The cutting insert according to claim 1 or 2.   The plurality of groove portions are formed such that the maximum width of the groove portion in the side view of the insert gradually increases from one end side to the other end side of the main cutting edge. 3. A cutting insert according to any one of the above.   The plurality of divided main cutting edges are formed so as to be gradually inclined so as to approach the seating surface from one end side to the other end side of the main cutting edge. A cutting insert as described above.   The cutting according to any one of claims 1 to 5, wherein the plurality of divided main cutting edges are formed such that a rake angle gradually increases from one end side to the other end side of the main cutting edge. insert.   The cutting insert according to any one of claims 1 to 6, wherein at least one protrusion is formed on the rake face corresponding to each of the divided main cutting edges. A holder having a substantially cylindrical shape;
A cutting insert according to any one of claims 1 to 7,
The cutting insert is mounted on the holder so that the main cutting edge is located on the tip surface side of the holder and one end of the main cutting edge is located on the outer peripheral side of the holder. Cutting tool. A substantially cylindrical main body,
A rolling tool provided with a tip blade formed on the tip side of the main body,
The tip blade comprises a plurality of small cutting blades separated by at least one recess,
The plurality of small cutting edges comprises an outer peripheral side small cutting edge located on the outer periphery of the main body part, and a spaced small cutting edge spaced from the outer periphery of the main body part,
The separated small cutting edge is formed so that the cutting edge length gradually increases from the outer peripheral side to the inner peripheral side of the main body.   The rolling tool according to claim 9, wherein a plurality of the recesses are formed, and the plurality of recesses are formed so that the width gradually increases from the outer peripheral side of the main body toward the inner peripheral side. .

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