JP2017177285A

JP2017177285A - Cutting insert

Info

Publication number: JP2017177285A
Application number: JP2016068955A
Authority: JP
Inventors: 修介北川; Shusuke Kitagawa; 小出　実; Minoru Koide; 実小出
Original assignee: NGK Spark Plug Co Ltd
Current assignee: Niterra Co Ltd
Priority date: 2016-03-30
Filing date: 2016-03-30
Publication date: 2017-10-05

Abstract

PROBLEM TO BE SOLVED: To provide a cutting insert of favorable discharge processability which stabilizes cutting chips by the grooving work of the outer peripheral surface of a cutting workpiece, develops no lateral deviation, and turns in a spiral spring form in a densely wound state.SOLUTION: A rake face 30 comprises a pair of right and left protrusions 50 arranged in symmetry with a straight line G drawn forward and rearward in between and orthogonally to a front cutting edge 21 at the intermediate position of the edge width of the front edge 21. Each protrusion 50 extends continuously forward and rearward and, when the rake face 30 is cut in a straight line parallel with the front cutting edge 21, shows a rectangular cross-sectional shape. An interval K between the apices 52 of the rectangles of the respective protrusions 50 is smaller from forward to rearward. Each protrusion 50 gets the inclination angles of both slope faces 54, 55 in the rectangle cross section larger from forward to rearward, and the angle between the apices 52 in the cross sections of the rectangles smaller from forward to rearward to be sharp. This pair of protrusions 50 enhance the discharge processibility of cutting chips.SELECTED DRAWING: Figure 3

Description

本発明は、金属材料の旋削加工で、溝入れ加工や突っ切り加工等に使用される切削インサート（バイト用インサート）に関する。 The present invention relates to a cutting insert (tool insert) used for grooving or parting-off processing in turning of a metal material.

例えば、機械工具用炭素鋼（Ｓ４５Ｃ等）、合金鋼（ＳＣＭ、ＳＮＣＭ等）、さらにはステンレス鋼等のような高強度材の切削においては、切り込みにおける送り量等にもよるが、通常、排出される切り屑が延びがちとなる。一方、このような被削材の外周面の溝入れ加工や突っ切り加工においては、それに用いられる切削インサートの前切れ刃で切削、生成され、すくい面上を後ろに流れる切り屑を、上向きにカールさせてぜんまい状に巻かせ、適度の巻状態において分断させて排出させる必要がある。こうすることで、工具への絡み付きや仕上面に接触することを防止するためである。また、被削材の端面への溝入れ加工においては、その半径方向の回転周速の相違から、生成される切り屑は、その半径外方（斜め後方）に流れるためにコイル状となるものの、これもすくい面上において上向きにカールさせ、コイル状の排出方向もぶれのない安定した切り屑として排出させる必要がある。すなわち、このような加工では、排出される切り屑の工具への絡み付きや仕上面への接触を如何に防止できるかといった切り屑処理性をどれだけ高められるか、ということが切削加工上においては極めて重要視される。こうした中、従来より、すくい面に、各種の形状の隆起部（隆起状の凸部又は突起）等を形成した切削インサート（以下、単にインサートともいう）が提案されている。 For example, when cutting high-strength materials such as carbon steel for machine tools (S45C, etc.), alloy steel (SCM, SNCM, etc.) and stainless steel, etc. The chip to be cut tends to extend. On the other hand, in such grooving and parting off of the outer peripheral surface of the work material, the chips cut and generated by the front cutting edge of the cutting insert used therefor and curled upward on the rake face are curled upward. It is necessary to let it wind into a mainspring shape, and to divide and discharge in an appropriate winding state. This is to prevent the tool from being entangled or coming into contact with the finished surface. In addition, in grooving to the end face of the work material, the generated chips are coiled because of the difference in rotational peripheral speed in the radial direction, so that the generated chips flow outward (diagonally backward) in the radius. Also, it is necessary to curl upward on the rake face, and to discharge the coiled discharge direction as stable chips without blurring. That is, in such processing, how much the chip processing property such as how to prevent the entangled chips from being entangled with the tool and how to contact the finish surface can be improved in cutting processing. Very important. Under these circumstances, cutting inserts (hereinafter also simply referred to as “inserts”) in which ridges (bump-shaped protrusions or protrusions) of various shapes are formed on the rake face have been proposed.

このような従来技術のうち、溝入れ加工や突っ切り加工に好適とされる切削インサートで、すくい面に、その前切れ刃に対して引いた垂直二等分線を挟んで互いに対向するように一対の隆起部を設け、この一対の隆起部のそれぞれの頂部が、垂直二等分線に沿う方向に向かってそれぞれ延びる２つの突部を有し、この二等分線側に近い側に位置している突部を第１突部とし、それに遠い側に位置している突部を第２突部としたとき、この両突部における頂部が、第１突部の頂部より第２突部の頂部を高位にした構造のものが知られている（特許文献１）。この切削インサートによる被削材の溝入れ加工においては、第１突部によって切り屑を変形させて硬化させることができるとともに、第２突部によって切り屑の排出方向における左右方向のぶれを抑制することができるため、切り屑の排出方向が安定し、その排出性能を向上させることができるなど、とされている。また、このものでは、一対の隆起部相互の間隔を後方に向かうに従い狭くするということも提案されている。 Among such prior arts, a cutting insert suitable for grooving and parting-off processing, and a pair of rake faces facing each other across a perpendicular bisector drawn with respect to the front cutting edge. The top of each of the pair of raised portions has two protrusions extending in the direction along the vertical bisector, and is located on the side close to the bisector side. When the projecting part which is located on the side far from the first projecting part is the second projecting part, the top part of the two projecting parts is closer to the second projecting part than the top part of the first projecting part. The thing of the structure which made the top part high is known (patent document 1). In the grooving process of the work material by the cutting insert, the first protrusion can deform and harden the chips, and the second protrusion can suppress lateral blur in the chip discharge direction. Therefore, the discharge direction of chips is stabilized, and the discharge performance can be improved. Moreover, in this thing, narrowing the space | interval of a pair of protruding part as it goes back is proposed.

特許第５６３９６５６号公報Japanese Patent No. 5369656

ところが、前記切削インサートで、外周面に溝入れ加工をする場合においては切り屑の排出方向における左右方向のぶれ（以下、横ぶれ）を抑制することについての効果は、未だ不十分であった。というのは、一対の隆起部の頂部のそれぞれが、上記垂直二等分線に近い側に位置している第１突部と、遠い側に位置しているこれより高位の第２突部とを有するものであるとしても、その各隆起部における第１、第２突部相互の前切れ刃の刃幅方向の間が比較的平坦な面をなし、この平坦な面のまま後方に延びているためである。すなわち、この切削インサートにおける一対の隆起部は、その頂部がそれぞれ比較的平坦であり、いわば略台形の山断面で前後に連なる形態を呈している。このため、前切れ刃で切削されて後方に流れる切り屑は、すくい面におけるその両横切れ刃寄り部位の一対の隆起部の頂部に乗り上げることでその両端寄り部位が持ち上げられ、切り屑の幅を狭めるように、横断面において上向き凹となすような形に変形はするものの、その乗り上げ後は、その頂部の平坦性ゆえに、ガイド性が悪く、横ぶれしがちとなる。 However, in the case where the outer peripheral surface is grooved with the cutting insert, the effect of suppressing lateral blur (hereinafter referred to as lateral blur) in the chip discharge direction has not been sufficient. This is because each of the tops of the pair of raised portions has a first protrusion located on the side close to the vertical bisector, and a second protrusion higher than this located on the far side. Even if the first and second protrusions of each of the raised portions have a relatively flat surface between the blade width directions of the first and second protrusions, and the flat surfaces extend rearward. Because it is. In other words, the pair of raised portions in the cutting insert has a relatively flat top portion, so to speak, has a form that is connected to the front and rear in a substantially trapezoidal mountain cross section. For this reason, the chips that have been cut by the front cutting edge and flowed rearward are lifted at the top of the pair of raised portions near the side cutting edges on the rake face, and the width of the chip is increased. Although it is deformed so as to be narrowed upward in the cross section so as to narrow, after the ride, due to the flatness of the top portion, the guide property is poor and it tends to be laterally shaken.

結果、この切削インサートによる外周面の溝入れや突っ切り加工においては、溝の壁面等に切り屑が接触し易く、横ぶれの無い、ぜんまい状にならず、螺旋状の巻となりがちであり、切り屑の排出処理性に難点があった。すなわち、前記切削インサートでは、隆起部における頂部の横幅が広く、平坦であるがために、切り屑がその頂部面において横ずれし、或いは、その頂部を横に乗り越えやすいため、横ぶれしがちとなるなど、その排出処理性に課題があった。 As a result, in grooving or parting off of the outer peripheral surface using this cutting insert, chips are likely to come into contact with the wall surface of the groove, etc. There was a difficulty in waste disposal. That is, in the cutting insert, since the width of the top portion of the raised portion is wide and flat, the chips are laterally shifted on the top surface, or the top portion tends to get over to the side, so that it tends to run out sideways. There was a problem in the discharge processability.

本発明はかかる課題に鑑みてなされたもので、被削材の特に外周面の溝入れや、突っ切り加工において生成され、すくい面を後方に流れる切り屑が、安定し、横ぶれもなく、ち密な巻状態のぜんまい状のものとなって、その排出処理性を高められる切削インサートを提供することを目的とする。 The present invention has been made in view of such a problem, and the chips generated in grooving or parting off of the outer peripheral surface of the work material, and flowing backward on the rake face, are stable, free from side wobbling, and dense. An object of the present invention is to provide a cutting insert that has a spirally wound mainspring shape and is capable of enhancing its discharge processability.

上記課題を解決するための請求項１に記載の本発明は、すくい面と前逃げ面との交叉稜部に前切れ刃を備え、該前切れ刃をその刃幅方向において挟む配置で両側に位置する各横逃げ面と前記すくい面との交叉稜部に横切れ刃を備える切削インサートであって、
前記すくい面には、前切れ刃の刃幅の中間位置において該前切れ刃に垂直に、該すくい面において前後に引いた直線を挟んで対称配置をなす左右一対の隆起部を備えると共に、その各隆起部は、前後に連なって延び、かつ、前記すくい面を前切れ刃の両端を結ぶ直線と平行な直線で、該すくい面側から切断したときに三角山の断面形状を呈するものとされ、
前記左右の各隆起部の三角山の頂部相互の間隔が前方から後方に向かうに従って小さくなり、
しかも、その左右の各隆起部は、その三角山の断面における両斜面の傾斜角が前方から後方に向かうに従い大きくなり、該三角山の断面における頂部の挟角が前方から後方に向かうに従い小さくなるように形成されていることを特徴とする。 The present invention as set forth in claim 1 for solving the above-mentioned problems is provided with a front cutting edge at the crossing ridge part of the rake face and the front flank face, and arranged on both sides in such a manner that the front cutting edge is sandwiched in the blade width direction. A cutting insert provided with a horizontal cutting edge at the intersection ridge between each lateral flank face and the rake face,
The rake face is provided with a pair of left and right raised portions that are symmetrically arranged with a straight line drawn back and forth on the rake face perpendicular to the front edge at the middle position of the edge width of the front edge, Each ridge extends continuously in the front-rear direction, and is a straight line parallel to the straight line connecting both ends of the front cutting edge, and exhibits a cross-sectional shape of a triangular mountain when cut from the rake face side. ,
The distance between the tops of the triangular peaks of the left and right ridges decreases from the front to the rear,
In addition, the ridges on the left and right sides of the triangular mountain section increase in inclination angle of both slopes from the front to the rear, and the apex angle in the triangular mountain section decreases from the front to the rear. It is formed as follows.

請求項２に記載の本発明は、前記間隔が前方から後方に向かうに従って小さくなる割合を、前記左右の各隆起部の前後方向の中間部位が、それより前寄り部位と後寄り部位に比較し、大きくなるものとしたことを特徴とする請求項１に記載の切削インサートである。
請求項３に記載の本発明は、前記左右の各隆起部の三角山の頂部の前記すくい面からの高さを、前方から後方の後端寄り部位に向かうに従い高くなるものとしたことを特徴とする請求項１又は２に記載の切削インサートである。 According to a second aspect of the present invention, the rate at which the distance decreases from the front toward the rear is compared between the front and rear portions of the middle portion in the front-rear direction of the left and right raised portions. The cutting insert according to claim 1, wherein the cutting insert is large.
The present invention according to claim 3 is characterized in that the height from the rake face of the top of the triangular mountain of each of the left and right raised portions is increased from the front toward the rear end portion. The cutting insert according to claim 1 or 2.

請求項４に記載の本発明は、前記左右の各隆起部を前記横逃げ面側から、前記前切れ刃の両端を結ぶ直線と平行な直線に沿う方向において見たときにおける該隆起部の三角山の頂部における前後の連なり状態を、該隆起部の前後長における前半部と後半部とを２つの直線で接続する上向き凹となす連なり状態とし、その連なりの前半部における前端部では上向き凸曲線で隆起し該凸曲線の後方に続く前記前半部の直線の前端に連なり、前記前半部と前記後半部とを２つの直線で接続する接続箇所を含む中間部位では上向き凹曲線で連なるものとしたことを特徴とする請求項３に記載の切削インサートである。 The present invention according to claim 4 is a triangle of the raised portions when the left and right raised portions are viewed from the side of the lateral relief surface in a direction along a straight line parallel to a straight line connecting both ends of the front cutting edge. The continuous state at the top of the mountain is a continuous state in which the front half and the rear half of the raised part are connected by two straight lines, and the front end of the front half of the series is an upward convex curve. It is connected to the front end of the straight line of the front half part that protrudes at the rear of the convex curve, and is connected to the front half part and the rear half part by an upward concave curve at an intermediate part that includes a connection part that connects the two straight lines. It is a cutting insert of Claim 3 characterized by the above-mentioned.

請求項５に記載の本発明は、前記左右の各隆起部を前記横逃げ面側から、前記前切れ刃の両端を結ぶ直線と平行な直線に沿う方向において見たときにおける該隆起部の三角山の頂部における前後の連なり状態を、該隆起部の前後長において上向き凹曲線による連なり状態とし、かつ、その連なりの前端部では上向き凸曲線で隆起し該凸曲線の後方に続く前記上向き凹曲線の前端に連なるものとしたことを特徴とする請求項３に記載の切削インサートである。 The present invention according to claim 5 is the triangle of the raised portions when the left and right raised portions are viewed from the side of the lateral relief surface in a direction along a straight line parallel to a straight line connecting both ends of the front cutting edge. The front and back continuous state at the top of the mountain is a continuous state with an upward concave curve in the front and rear length of the raised portion, and the upward concave curve that rises with an upward convex curve at the front end of the continuous portion and continues behind the convex curve The cutting insert according to claim 3, wherein the cutting insert is continuous with the front end of the cutting insert.

本発明に係る切削インサートによって、例えば、被削材（丸棒）の外周面を旋削により溝入れ加工する場合に発生する切り屑は、その前切れ刃（刃先）にて、その刃幅を横幅とする帯板状のものとなって生成され、すくい面を後方に向けて、上向きにカールするように流れる。このような帯板状の切り屑は、すくい面に設けられた上記左右一対の隆起部の前端に、その下面における両側端寄り部位が押し付けられる。これにより、後方に流れる帯板状の切り屑は、その幅方向の中央に対し、その両側がすくい面（隆起部）側から押し上げられる作用を受けるとともに、その前後に延びる隆起部にて後方に案内（ガイド）されながら流れる。結果、切り屑は、被削材の材質（被削性）や切り込みにおける送り量等にもよるが、横断面において上面において凹となし幅を狭めるような変形（以下、幅方向の変形ともいう）をするか、低硬度材では、上記左右一対の隆起部（三角山）の横断面の頂部形状に対応した凹み、又は、すじ状の変形（以下、すじ状変形ともいう）が付けられながら、或いはこのような、すじ状の変形と共に幅方向の変形が付けられながら後方に流れる。これにより、切り屑は、その幅が加工している溝幅より小さく、そして、横（左右）ぶれも防止されながら排出される。 With the cutting insert according to the present invention, for example, chips generated when grooving the outer peripheral surface of a work material (round bar) by turning the width of the cutting edge at the front cutting edge (cutting edge) It is generated in the form of a band plate, and flows so as to curl upward with the rake face facing rearward. Such band-plate-like chips are pressed against the front ends of the pair of left and right raised portions provided on the rake face, on both sides of the lower surface thereof. As a result, the strip-like chip flowing backward is subjected to the action that both sides thereof are pushed up from the rake face (bump) side with respect to the center in the width direction, and at the back of the ridge extending forward and backward. It flows while being guided. As a result, depending on the material of the work material (machinability) and the feed amount of the cut, the chip is a deformation that narrows the width on the upper surface in the cross section (hereinafter also referred to as a deformation in the width direction). In a low-hardness material, a dent corresponding to the top shape of the cross section of the pair of left and right raised portions (triangular mountain) or a streak-like deformation (hereinafter also referred to as a streak-like deformation) is attached. Alternatively, it flows backward while being deformed in the width direction along with the streak-shaped deformation. Thereby, the chip is discharged while its width is smaller than the width of the groove being processed, and lateral (left and right) shaking is prevented.

そして、本発明においては、各隆起部が、前後に連なって延び、かつ、前記すくい面を前切れ刃の両端を結ぶ直線と平行な直線で、該すくい面側から切断したとき、三角山の断面形状を呈するものとされている。すなわち、この各隆起部は、その頂部が平坦ではなく鋭利な断面三角山で前後に延びる軌道（又は凸条）をなしている。一方、上記した従来の切削インサートでは、隆起部の頂部の横幅が広く、比較的平坦なもので前後に延びている。このため、切り屑は、その頂部（面）において横ずれし、或いは、その頂部を横に乗り越えやすいのに対し、本発明では、すくい面上を流れる切り屑に対し、前後に延びる三角山の鋭利な頂部が食い込みやすいから、切り屑が横ずれ（横すべり）しにくく、その頂部を横に乗り越えにくい。そして、この鋭利な山をなす左右の各隆起部の三角山の頂部相互の間隔が、前方から後方に向かうに従って小さくなるものとされているため、その隆起部上を後ろに流れる切り屑は、その頂部相互間の中央に向かうようにガイドされる。その上、上面を凹となす形の変形（幅方向の変形）の促進作用を受けるから、上向きカールされてぜんまい状に巻かれる際にも、綺麗な巻のぜんまい状の切り屑となる。しかも、このような三角山の断面頂部における挟角が、前方から後方に向かうに従い小さくなり、その鋭利性が高められているため、こうした作用効果もその流れ過程で高められる。すなわち、本発明では、外周面の溝入れや、突っ切り加工において、一対の隆起部による上記した各作用効果が重畳するため、そのすくい面を後方に流れる切り屑が、安定し、横ぶれもなく、ち密な巻状態のぜんまい状のものとなるため、その排出処理性が高められる。なお、本発明において、前記すくい面を前切れ刃の両端を結ぶ直線と平行な直線で、該すくい面側から切断したとき、というときの、「前切れ刃の両端」における「端」は、前切れ刃の両端において横切れ刃との交叉部に、すくい面においてアール（又は面取り状の傾斜）がつけられているときは、その「アール」にさしかかる前の箇所とする。すなわち、前切れ刃のうち、横切れ刃に向かう端は、その「アール」と前切れ刃との境界点を意味する。 In the present invention, when each ridge extends from front to back, and the rake face is cut from the rake face side by a straight line parallel to a straight line connecting both ends of the front cutting edge, It is supposed to have a cross-sectional shape. That is, each bulge has a track (or ridge) extending forward and backward with a triangular cross section having a sharp top section and not a flat top. On the other hand, in the above-described conventional cutting insert, the width of the top of the raised portion is wide, and is relatively flat and extends back and forth. For this reason, the chips are laterally shifted at the top (surface) or easily get over the top, and in the present invention, the sharpness of the triangular mountain extending in the front-rear direction with respect to the chips flowing on the rake face. Since the top is easy to bite, the chips are less likely to slip sideways (slip), and it is difficult to get over the top sideways. And since the interval between the tops of the triangular peaks of the left and right ridges forming this sharp mountain is reduced from the front toward the rear, the chips flowing backward on the ridges are Guided toward the center between the tops. In addition, since it has an effect of promoting the deformation of the shape with the concave surface (deformation in the width direction), even when curled upward and wound into a mainspring shape, it becomes a beautifully wound mainspring-like chip. In addition, the angle at the top of the cross section of such a triangular mountain becomes smaller as it goes from the front to the rear, and the sharpness thereof is enhanced. Therefore, these effects are also enhanced in the flow process. That is, in the present invention, in the grooving and parting off of the outer peripheral surface, the above-described effects by the pair of raised portions are superimposed, so that the chips flowing rearward on the rake face are stable and free from lateral deviation. Since the mainspring is in a densely wound state, its discharge processability is improved. In the present invention, when the rake face is a straight line parallel to the straight line connecting both ends of the front cutting edge and is cut from the rake face side, the `` ends '' in `` both ends of the front cutting edge '' When a radius (or chamfered slope) is applied to the rake face at the intersection with the horizontal cutting edge at both ends of the front cutting edge, this is the location before the "R" is reached. That is, the end of the front cutting edge toward the horizontal cutting edge means a boundary point between the “R” and the front cutting edge.

本発明において一対の隆起部相互の間隔が小さくなる割合（変化割合）については、一対の隆起部を後方においてその相互間の間隔が小さくなるように直線状に延ばすか、すくい面側から見て（以下、上面視、又は上面視において、ともいう）、前切れ刃の中間位置で、前切れ刃に垂直に、該すくい面において前後に引いた直線（１つの垂直な直線）を挟み、その直線側を向いて凹、又は凸となす半径の大きな円弧曲線としてもよい。ただし、この変化割合は、請求項２に記載の発明のように、変化させるのがよい。すなわち、請求項２に記載の発明では、隆起部のうち、その間隔が小さくなる割合について、前切れ刃側に位置する前寄り部位では、相対的にそれを小さくし、中間部位では、相対的にそれを大きくし、さらに、後寄り部位ではそれを小さくし、前後方向において、緩、急、緩の変化割合となるようにしている。これにより、切り屑は、前寄り部位で、後方へのガイド作用が保持され、左右の振れが防止され、中間部位で、その変化割合が大きくされているため、幅を小さく変形させられ、横ぶれの無い、ぜんまい巻とされ、後寄り部位でガイド性よく後方に流され得る。なお、本願において、すくい面側から見た図は、平面図（上面図）のことである。 In the present invention, the rate at which the distance between the pair of raised portions is reduced (change rate) is such that the pair of raised portions are linearly extended at the rear so that the interval between the raised portions is reduced or viewed from the rake face side. (Hereinafter also referred to as top view or top view), sandwiching a straight line (one vertical straight line) drawn back and forth on the rake face at the middle position of the front cutting edge, perpendicular to the front cutting edge, It is good also as a circular arc curve with a large radius which makes concave or convex toward the straight line side. However, this change ratio is preferably changed as in the second aspect of the invention. That is, in the invention according to claim 2, with respect to the proportion of the bulging portion where the interval is small, the front portion located on the front cutting edge side is relatively small, and the intermediate portion is relatively small. Furthermore, it is made larger and further reduced at the rear part so that the rate of change is slow, steep and slow in the front-rear direction. As a result, the chip has a backward guide action at the front part, prevents left and right deflection, and the change rate is increased at the intermediate part. The mainspring winding is free from shaking and can be swept backwards with good guideability at the rear part. In addition, in this application, the figure seen from the rake face side is a top view (top view).

なお、すくい面上を後方に流れる切り屑は、上向きにカールするため、その流れ過程で幅方向の変形を大きくしたい場合には、一対の隆起部の高さは、前方から後方に向けて次第に高くするのがよいが、隆起部の前端において幅方向の変形が決まるような場合には、その後方に向けての高さは減少するものであっても、前後において一定の高さであってもよい。ただし、好ましくは、請求項３に記載の発明のように、一対の隆起部の高さを前方から後方に向けて次第に高くするのがよい。このように高さを漸増させることとすることにより、後方に流れる切り屑の上向きカール性を一層高めることができ、ぜんまい巻をち密にできるためである。これにより、一層、切り屑処理性を高めることができる。なお、このようにその高さを漸増する場合には、請求項４又は５に記載したように隆起部に高さ変化を付与するのがよい。こうすることで、ぜんまい状に巻かれる切り屑は、隆起部の前後方向における後半部に、強く押し付けられるため、一層、上向きカール性が高められると共に、ち密な、ぜんまい巻となるから、さらに一層、切り屑処理性が高められる。なお、本願において、前記横逃げ面側から、前記前切れ刃の両端を結ぶ直線と平行な直線に沿う方向において見たとき、切削インサートを側面から見たときを意味する。 In addition, since the chips flowing backward on the rake face curl upward, when it is desired to increase the deformation in the width direction during the flow process, the height of the pair of raised portions gradually increases from the front toward the rear. It is better to make it higher, but when the deformation in the width direction is determined at the front end of the ridge, even if the height toward the rear is reduced, the height is constant at the front and rear. Also good. However, it is preferable that the height of the pair of raised portions is gradually increased from the front to the rear as in the invention described in claim 3. By gradually increasing the height in this way, the upward curling property of the chips flowing backward can be further enhanced, and the mainspring winding can be made dense. Thereby, chip disposal property can be improved further. In addition, when gradually increasing the height in this way, it is preferable to give a height change to the raised portion as described in claim 4 or 5. In this way, the chips wound in the mainspring shape are strongly pressed against the rear half of the raised portion in the front-rear direction, so that the upward curling property is further improved and the mainspring winding becomes even more dense. , Chip disposal is improved. In addition, in this application, when it sees in the direction along the straight line parallel to the straight line which connects the both ends of the said front cutting edge from the said side flank side, it means the time when the cutting insert is seen from the side surface.

本発明に係る切削インサートの全体形状を説明する図であって、Ａはすくい面側から切削インサートを見た図（平面図、又は上面図）、Ｂは横逃げ面側から、前切れ刃の両端を結ぶ直線と平行な直線に沿う方向において切削インサートを見た図（側面図）、Ｃは切削インサートの底面図。BRIEF DESCRIPTION OF THE DRAWINGS It is a figure explaining the whole shape of the cutting insert which concerns on this invention, Comprising: A is the figure (plan view or top view) which looked at the cutting insert from the rake face side, B is a side cutting face side, The figure (side view) which looked at the cutting insert in the direction along the straight line parallel to the straight line which connects both ends, C is a bottom view of the cutting insert. 図１−Ｂの左（又は右）の端面（前逃げ面）を見た拡大図。The enlarged view which looked at the left (or right) end surface (front flank) of FIG. 1-B. 図１−Ａの切れ刃部の拡大図。The enlarged view of the cutting-blade part of FIG. 1-A. 図３のＳ１−Ｓ１矢視断面図。S1-S1 arrow sectional drawing of FIG. 図１−Ｂの切れ刃部の拡大図。The enlarged view of the cutting-blade part of FIG. 1-B. 図３の切れ刃部のすくい面を前切れ刃側から見た斜視図。The perspective view which looked at the scoop surface of the cutting blade part of FIG. 3 from the front cutting blade side. 図３の切れ刃部のすくい面を前切れ刃と反対側（後方）から見た斜視図。The perspective view which looked at the scoop surface of the cutting blade part of FIG. 3 from the opposite side (back) with the front cutting edge. 図３のＳ２−Ｓ２線（拡大）断面図、Ｓ３−Ｓ３線（拡大）断面図、Ｓ４−Ｓ４線（拡大）断面図。S2-S2 line (enlarged) cross-sectional view, S3-S3 line (enlarged) cross-sectional view, and S4-S4 line (enlarged) cross-sectional view of FIG. 図３のＳ１−Ｓ１線断面図において、隆起部の前後方向における高さ変化の別例を説明する図。The figure explaining another example of the height change in the front-back direction of a protruding part in the S1-S1 sectional view taken on the line of FIG. すくい面の変形例を説明する図であって、図３に相当する図。It is a figure explaining the modification of a rake face, Comprising: The figure corresponded in FIG. すくい面の変形例を説明する図であって、図６に相当する図。It is a figure explaining the modification of a rake face, Comprising: The figure corresponded in FIG.

本発明の切削インサートを具体化した実施の形態例について、図１−図８に基づいて詳細に説明する。本例のインサート１０１は、棒状部１０の両端部（図１のＡ〜Ｃの左右端部）に切れ刃部２０を備える２コーナタイプの矩形の溝入れ用切削インサートである。ただし、切れ刃部２０は、すくい面（上面）３０が両端部のそれとも同向き（図１のＢ上）を向いて設けられており、各前切れ刃２１をそのすくい面３０側から見たとき（図１のＡ）において膨拡状をなしている。なお、両切れ刃部２０をつないでいる棒状部１０は、ホルダ（図示せず）への固定用部位をなすところであり、横断面が上下に長い長方形で、一定の横断面で延びる四角棒をベースにして、すくい面３０と同向き面（図１のＢ上面１１）は、その長手方向において概略Ｖ字状の溝１３が延びる形状を呈している。後述するように、本例ではその底面（インサートの下面）１４も、その長手方向において概略Ｖ字状の溝１５が延びる形状を呈しており、ホルダへの固定時においてその固定用部位（ホルダのクランプ部位）に設けられている対応する凸部に嵌合され、横方向への移動防止が図られるよう形成されている。なお、本例のインサート１０１は、四角棒を長手方向中央で横断する直線（図１のＡ〜Ｃの左右方向の中央で棒状部を切断する線）に関して、各切れ刃部２０を含め、対称形状をなしている。また、各切れ刃部２０についても、これをすくい面３０側から見たときの形状は、図１のＡにおいて前切れ刃２１の幅方向中央を横断する直線に関して対称形をなしている。以下、一方の前切れ刃２１を含む切れ刃部２０の形状を中心として説明する。なお、インサート１０１は、切削条件等に応じた適宜の公知材料（例えば、超硬合金）からなるものとされる。 The embodiment which actualized the cutting insert of this invention is described in detail based on FIGS. The insert 101 in this example is a two-corner rectangular grooving cutting insert having cutting edge portions 20 at both end portions (left and right end portions of FIGS. 1A to 1C) of the rod-shaped portion 10. However, the cutting edge portion 20 is provided with the rake face (upper surface) 30 facing the same direction as that of both end portions (on B in FIG. 1), and each front cutting edge 21 is viewed from the rake face 30 side. Sometimes (A in FIG. 1). In addition, the rod-shaped part 10 which connects both the cutting edge parts 20 is a place which makes the site | part for fixing to a holder (not shown). As a base, the surface facing the rake face 30 (the B upper surface 11 in FIG. 1) has a shape in which a substantially V-shaped groove 13 extends in the longitudinal direction. As will be described later, in this example, the bottom surface (the lower surface of the insert) 14 also has a shape in which a substantially V-shaped groove 15 extends in the longitudinal direction. It is formed so as to be fitted to a corresponding convex portion provided in the clamp part) and to prevent movement in the lateral direction. In addition, the insert 101 of this example is symmetrical with respect to a straight line (line that cuts the rod-like portion at the center in the left-right direction in FIGS. 1A to 1C) including the respective cutting blade portions 20 with respect to a straight line that crosses the square rod at the center in the longitudinal direction. It has a shape. Further, the shape of each cutting edge portion 20 when viewed from the rake face 30 side is symmetrical with respect to a straight line crossing the center in the width direction of the front cutting edge 21 in FIG. Hereinafter, the shape of the cutting edge portion 20 including one front cutting edge 21 will be mainly described. The insert 101 is made of an appropriate known material (for example, cemented carbide) according to cutting conditions and the like.

本例のインサート１０１は、切れ刃部２０における前端面が前逃げ面４０をなし、この前逃げ面４０とすくい面３０との交叉稜部が前切れ刃（刃先）２１をなしている。また、本例におけるこの前切れ刃２１及びその切れ刃稜線は、その左右両端の横切れ刃に向けて直線状に延びるようになっており、したがって、この前切れ刃２１をすくい面３０側から見たときは、固定用部位（棒状部）１０の前後方向に対して直角な直線であり、前逃げ面４０側から見たときも直線を呈するものとされている。ただし、切り屑を横断面の幅方向において積極的に上向き凹に変形させたいときは、例えば、前逃げ面４０側から見たとき（図２参照）において、前切れ刃２１はその幅方向の中央が凹となす円弧状としておいてもよい。 In the insert 101 of this example, the front end surface of the cutting edge portion 20 forms a front flank 40, and the cross ridge portion between the front flank surface 40 and the rake face 30 forms a front cutting edge (blade edge) 21. In addition, the front cutting edge 21 and the cutting edge ridge line in this example extend linearly toward the lateral cutting edges at both the left and right ends. Therefore, the front cutting edge 21 is viewed from the rake face 30 side. Is a straight line perpendicular to the front-rear direction of the fixing portion (rod-like portion) 10 and is also a straight line when viewed from the front flank 40 side. However, when it is desired to positively deform the chips into a concave upward in the width direction of the cross section, for example, when viewed from the front flank 40 side (see FIG. 2), the front cutting edge 21 is in the width direction. You may make it the circular arc shape which the center makes a concave.

一方、前切れ刃２１をその刃幅方向において挟む切れ刃部２０における両側の面が、それぞれ、横逃げ面４３をなし、この横逃げ面４３とすくい面３０との交叉稜部が、それぞれ後方に延びる横切れ刃２３をなしている。この横切れ刃２３は、これをすくい面３０側から見たとき（図３参照）、直線状で、すくい面３０の横幅を、前切れ刃２１から後方に向かうに従い小さくするテーパ（バックテーパ）が付与されている。このため、この横切れ刃２３と前切れ刃２１は、これをすくい面３０側から見たとき、９０度より小さい角度で交差するものとされている。そして、本例ではその両刃の接続コーナに微小な円弧切れ刃（アール）２２が付けられている。また、この横切れ刃２３の後端においては、固定用部位（棒状部）１０の前端部に向け、そのバックテーパより大きいテーパで狭まる首部４５を介して接続されている。なお、前逃げ面４０及び横逃げ面４３には、適度の逃げ角（前逃げ角、横逃げ角）が付けられており、したがって、切れ刃部２０におけるすくい面３０と反対側を向く底面（下面）１４は、それらの逃げ角に対応して、すくい面３０の平面形状より一回り小さいものとされている。なお、この底面１４を含め、固定用部位（棒状部）１０の下面は、上記もしたように、Ｖ字状の溝１５が長手方向に延びたものとされており、ホルダへの固定における横方向への移動防止が図られるものとされている。 On the other hand, the surfaces on both sides of the cutting edge portion 20 sandwiching the front cutting edge 21 in the width direction of the blade each form a lateral flank surface 43, and the cross ridges between the lateral flank surface 43 and the rake face 30 are respectively rearward. A transverse cutting edge 23 extending in the direction is formed. When this side cutting edge 23 is viewed from the rake face 30 side (see FIG. 3), it is linear and has a taper (back taper) that reduces the lateral width of the rake face 30 from the front cutting edge 21 toward the rear. Has been granted. For this reason, the horizontal cutting edge 23 and the front cutting edge 21 intersect with each other at an angle smaller than 90 degrees when viewed from the rake face 30 side. In this example, a small arc cutting edge (R) 22 is attached to the connecting corner of the two blades. In addition, the rear end of the horizontal cutting edge 23 is connected to a front end portion of the fixing portion (bar-shaped portion) 10 via a neck portion 45 narrowed with a taper larger than the back taper. The front flank 40 and the side flank 43 have an appropriate flank angle (front flank angle, side flank angle), and therefore, the bottom surface of the cutting edge 20 facing the rake face 30 (the opposite side) ( The lower surface 14 is made to be slightly smaller than the planar shape of the rake face 30 corresponding to the clearance angle. In addition, the bottom surface of the fixing portion (rod-like portion) 10 including the bottom surface 14 is formed with the V-shaped groove 15 extending in the longitudinal direction as described above. It is supposed to prevent movement in the direction.

切れ刃部２０におけるすくい面３０は、図４に示したように、固定用部位１０の上面（すくい面３０と同向き面）１１に対し、固定用部位１０の前端部において、前方に下向き傾斜する傾斜状壁面（ブレーカ壁面）４７を介して低位をなすように形成されている。ただし、本例では、すくい面３０は、後方に対し前切れ刃２１が高位をなすポジのすくい角（５〜２０度）が付くように形成されており、溝入れ加工における切削抵抗の低減が図られている。そして、本例ではすくい面３０が、前切れ刃２１から後方に向かい、すくい面３０の前後の中間までの前半部位（Ｌ１）において、ポジ角に対応して次第に低位をなす傾斜面をなしており、その中間部位から上記した傾斜状壁面４７に向かう首部４５を含む後半部位においてはその傾斜角が略０度（固定部位の上面と平行）となって連なり、さらに、後方に向けて、上向き急勾配角（例えば、４０度〜５０度）の上記した傾斜状壁面４７へと、それぞれ上向き凹となす曲面を介して連なるように形成されている（図４参照）。なお、横切れ刃２３を横逃げ面４３側から見たとき、その前後方向における傾斜は、すくい面３０における前後方向の傾斜よりは小さいが、それに倣うものとされている（図５参照）。以下、「横切れ刃２３を横逃げ面４３側から見たとき」とは、横切れ刃２３を横逃げ面４３側から、前切れ刃２１の両端を結ぶ直線と平行な直線（仮想直線）に沿う方向において見たとき、という意味であり、他に、「横逃げ面側から見たとき」というときも、横逃げ面４３側から、前切れ刃２１の両端を結ぶ直線と平行な直線（仮想直線）に沿う方向において見たとき、を意味するものである。 As shown in FIG. 4, the rake face 30 in the cutting edge portion 20 is inclined forward and downward at the front end portion of the fixing portion 10 with respect to the upper surface 11 (the same direction as the rake face 30) of the fixing portion 10. It forms so that it may become low through the inclined wall surface (breaker wall surface) 47 which does. However, in this example, the rake face 30 is formed so as to have a positive rake angle (5 to 20 degrees) where the front cutting edge 21 is higher than the rear, and the cutting resistance in grooving is reduced. It is illustrated. In the present example, the rake face 30 forms a slanting surface that gradually moves downward from the front cutting edge 21 and gradually lowers in correspondence with the positive angle in the first half portion (L1) before and after the rake face 30. In the latter half portion including the neck portion 45 heading from the intermediate portion to the inclined wall surface 47 described above, the inclination angle is approximately 0 degrees (parallel to the upper surface of the fixed portion), and further upwards toward the rear. It forms so that it may continue to the above-mentioned inclined wall surface 47 of a steep slope angle (for example, 40 degree-50 degree | times) via the curved surface which makes an upward concave respectively (refer FIG. 4). When the side cutting edge 23 is viewed from the side of the side clearance surface 43, the inclination in the front-rear direction is smaller than the inclination in the front-rear direction on the rake face 30, but it is assumed to follow that (see FIG. 5). Hereinafter, “when the side cutting edge 23 is viewed from the side clearance surface 43 side” is along a straight line (virtual straight line) parallel to a straight line connecting both ends of the front cutting edge 21 from the side clearance surface 43 side of the side cutting edge 23. In other words, when viewed from the side of the side clearance surface, a straight line parallel to the straight line connecting the ends of the front cutting edge 21 from the side of the side clearance surface 43 (virtual) When viewed in a direction along a straight line).

また、すくい面３０のうち、左右の各横切れ刃２３に沿う部位におけるすくい面３０ｂは、これを全体としてみたときは、その前後方向においては、前記したすくい面３０と同様な傾斜を呈している。ただし、このすくい面３０ｂは、横切れ刃２３から内側に向けて、すなわち、すくい面３０側から見て、前切れ刃２１の幅方向の中心においてその前切れ刃２１に垂直に、前後に引いた直線（仮想直線）Ｇに向けても低位をなし、ポジのすくい角（傾斜）が付くように形成されている。すなわち、横切れ刃２３についても、適度のポジ角が付くように形成されている。ただし、そのポジ角は前切れ刃２１から離間するに従い、その前半部位（Ｌ１）において漸増するようにされている。 Moreover, the rake face 30b in the part along the horizontal cutting edges 23 on the left and right sides of the rake face 30 exhibits the same inclination as the rake face 30 in the front-rear direction when viewed as a whole. . However, this rake face 30b was drawn inward from the side cutting edge 23 inward, that is, perpendicularly to the front cutting edge 21 at the center in the width direction of the front cutting edge 21 when viewed from the rake face 30 side. Even toward the straight line (virtual straight line) G, it is formed at a low position and has a positive rake angle (inclination). That is, the horizontal cutting edge 23 is also formed to have an appropriate positive angle. However, the positive angle gradually increases at the front half portion (L1) as the distance from the front cutting edge 21 increases.

さて、このような本例インサート１０１において、そのすくい面３０には、上記した仮想直線Ｇを挟んで対称配置をなす左右一対の隆起部５０が、次のような形状ないし構造のものとして設けられている。すなわち、本例において、各隆起部５０は、すくい面３０における前切れ刃２１と横切れ刃２３が交差するその接続コーナの微小な円弧切れ刃２２の近傍から、後方に向けて前後に、詳細は後述するが、後方に向かうに従い仮想直線Ｇに近接するような変化状態で山脈状に連なり延びている。ただし、左右一対の隆起部５０の間隔は、前方から後方に向かうに従って小さくなっている。また、この各隆起部５０は、すくい面３０を前切れ刃２１に平行な直線で切断したとき（図３、図８参照）、すなわち、すくい面３０を前切れ刃２１の両端を結ぶ直線と平行な直線で、すくい面３０側から切断したとき、頂部５２が鋭利な三角山の断面形状を呈し、前後に山脈状に連なるものとされている。そして、左右の一対の隆起部５０の三角山の頂部５２相互の間隔Ｋが、前方から後方に向かうに従って小さくなるものとされている（図３、図８参照）。すなわち、図３等において、対向する隆起部５０の頂部５２の前後方向の連なりとして、その稜線を太い線Ｔで示したように、頂部５２相互の間隔Ｋが、前方から後方に向かうに従って小さくなるものとされている。なお、三角山の頂部５２は、ガイド性や食い込み性の点からは、できるだけ鋭利な方がよいが、カケや耐摩耗性を考慮すると、Ｒ０．０５〜０．５ｍｍとするのがよい。 Now, in this example insert 101, the rake face 30 is provided with a pair of left and right raised portions 50 that are symmetrically arranged with the virtual straight line G interposed therebetween, and have the following shape or structure. ing. That is, in this example, each bulging portion 50 has a front and rear cutting edge 21 and a side cutting edge 23 on the rake face 30 that intersect each other from the vicinity of the minute arc cutting edge 22 of the connecting corner, and back and forth. As will be described later, it extends continuously in a mountain range in a changing state such that it approaches the virtual straight line G as it goes rearward. However, the distance between the pair of left and right raised portions 50 decreases from the front to the rear. Each raised portion 50 is formed by cutting the rake face 30 along a straight line parallel to the front cutting edge 21 (see FIGS. 3 and 8), that is, a straight line connecting the rake face 30 to both ends of the front cutting edge 21. When cut from the rake face 30 side by a parallel straight line, the top 52 has a sharp triangular mountain cross-sectional shape, and is continuous in a mountain range. And the space | interval K between the top parts 52 of the triangular mountain of a pair of right and left raised parts 50 shall become small as it goes to the back from the front (refer FIG. 3, FIG. 8). That is, in FIG. 3 and the like, as a series in the front-rear direction of the top portions 52 of the raised portions 50 facing each other, as indicated by the thick line T, the distance K between the top portions 52 becomes smaller from the front toward the rear. It is supposed to be. The apex 52 of the triangular mountain is preferably as sharp as possible from the viewpoint of guide property and bite property. However, in consideration of chipping and wear resistance, it is preferably R0.05 to 0.5 mm.

そして、その左右の各隆起部５０は、その三角山の断面における内外の両斜面（山腹）５４，５５の傾斜角（仮想直線Ｇ向き斜面５４の傾斜角：α、横切れ刃２３向き斜面５５の傾斜角：β）が前方から後方に向かうに従い大きくなり、したがって、その三角山の断面における頂部５２の挟角γが前方から後方に向かうに従い小さく、鋭くなるように形成されている（図８参照）。一方、上記したように、左右の一対の隆起部５０の三角山の頂部５２相互の間隔Ｋは、前方から後方に向かうに従って小さくなるものとされているが、この小さくなる変化割合は、三角山の頂部５２を前後方向において線で連ねた稜線（Ｔ）として示したとき、それぞれ、上面視、直線となるようにしてもよいが、本例でのその間隔Ｋの小さくなる割合は、前記左右の各隆起部５０における前後方向の中間部位が、それより前寄り部位と、後寄り部位に比較し、大きくなるように、変化が付けられている（図３参照）。 Then, the left and right raised portions 50 are inclined angles of both the inner and outer slopes (hillsides) 54 and 55 in the section of the triangular mountain (inclination angle of the slope 54 facing the virtual straight line G: α, the slope 55 facing the side cutting edge 23). The inclination angle β is increased as it goes from the front to the rear. Therefore, the sandwich angle γ of the top 52 in the cross section of the triangular mountain is made smaller and sharper as it goes from the front to the rear (see FIG. 8). ). On the other hand, as described above, the interval K between the tops 52 of the triangular mountains of the pair of left and right raised parts 50 is reduced from the front to the rear. When the top portion 52 is shown as a ridge line (T) connected in a line in the front-rear direction, the top 52 may be a straight line, respectively. A change is made so that the intermediate portion in the front-rear direction in each of the raised portions 50 is larger than the front portion and the rear portion (see FIG. 3).

すなわち、本例では、すくい面３０側から見たとき（図３参照）、三角山の頂部５２を前後方向において連ねた稜線（図中太線）Ｔは、前寄り部位、中間部位、そして、後寄り部位の順で、左右の各隆起部５０とも、前後方向において、仮想直線Ｇに向けて、緩、急、緩の勾配ないし変化で、その左右相互間において互いに近づき、その両者の間隔Ｋが前方から後方に向かうに従って小なる変化割合で形成されている。より具体的には、各隆起部５０における三角山の頂部５２を前後方向において連ねた稜線Ｔは、これをすくい面３０側から見たとき（図３参照）、その前寄り部位では、前方から後方に向けて前記仮想直線Ｇに近づく傾斜の直線を呈し、中間部位では、この直線に続き、仮想直線Ｇを向いて凹となす緩やかな円弧曲線Ｒ１、そしてこの円弧曲線Ｒ１に続き、仮想直線Ｇを向いて凸となす緩やかな円弧曲線Ｒ２でもってその仮想直線Ｇに緩やかに近づくカーブ変化を有するものとされている。 That is, in this example, when viewed from the rake face 30 side (see FIG. 3), the ridge line (thick line in the figure) T connecting the tops 52 of the triangular mountains in the front-rear direction is a front part, an intermediate part, and a rear part. Each of the left and right raised portions 50 in the order of the offset parts approaches each other between the left and right sides in a gradual or change of gentle, steep, or gentle direction toward the virtual straight line G in the front-rear direction. It is formed with a smaller change rate from the front to the rear. More specifically, the ridge line T connecting the tops 52 of the triangular mountains in the ridges 50 in the front-rear direction, when viewed from the rake face 30 side (see FIG. 3) An inclined straight line approaching the virtual straight line G toward the rear is presented, and at the intermediate portion, following this straight line, a gentle circular arc R1 that is concave toward the virtual straight line G, and following this circular arc R1, It is assumed that there is a curve change that gradually approaches the virtual straight line G with a gentle arc curve R2 that is convex toward G.

また、本例において左右一対の隆起部５０は、そのすくい面３０からの高さが、Ｈ１＜Ｈ２＜Ｈ３として、図８に示したように、前方から後方（後端寄り部位）に向かうに従い次第に高くなるものとされている。ただし、隆起部５０における頂部５２のすくい面３０からの高さの前後方向における変化は、横逃げ面側から見ると（図４参照）、稜線Ｔが、隆起部５０の前後方向の中間部位Ｐ１において上向き凹と屈曲するような２つの直線状のものとなっている（図４参照）。すなわち、図４において、その稜線Ｔは、隆起部５０の前端部５０ａから後方に向かう中間部位Ｐ１までの前後範囲（前半部Ｚａ）は、すくい面３０のポジの傾斜面に倣い、僅かではあるが下向き傾斜の直線を呈し、Ｐ１より後端５０ｃに向けての前後範囲（後半部Ｚｃ）は上向き傾斜に転じた直線を呈し、隆起部５０のすくい面３０からの高さは、後端寄り部位に向けて次第に高くなるように形成されている。なお、この中間部位Ｐ１は、すくい面３０の前後方向における前切れ刃２１のポジ角の後端までの範囲（すくい面の前半部Ｌ１）におけるその後端より前方に位置している。このように、本例では、各隆起部５０を横逃げ面４３側から見たとき、すなわち、各隆起部５０を横逃げ面４３側から、前切れ刃２１の両端を結ぶ直線と平行な直線（仮想直線）に沿う方向において見たとき、隆起部５０の三角山の頂部５２における前後の連なり状態（稜線Ｔ）は、隆起部５０の前後長における前半部Ｚａと後半部Ｚｃとを２つの直線で接続する上向き凹となす連なり状態となっている。ただし、上向き凹となす連なり部（中間部位Ｐ１）では上向き凹アールで連なっており、また、隆起部５０の前半部における前端部５０ａでは上向き凸曲線で隆起しこの凸曲線を介して前半部の直線の前端に連なるものとなっている。 Further, in the present example, the pair of left and right raised portions 50 has a height from the rake face 30 as H1 <H2 <H3, as shown in FIG. 8, from the front toward the rear (part near the rear end). It is supposed to become higher gradually. However, the change in the front-rear direction of the height from the rake face 30 of the top portion 52 in the raised portion 50, when viewed from the side of the side flank (see FIG. 4), the ridge line T is an intermediate portion P1 in the front-rear direction of the raised portion 50. In FIG. 4, there are two straight lines that bend upward and bend (see FIG. 4). That is, in FIG. 4, the ridgeline T is slightly in the front-rear range (front half portion Za) from the front end portion 50 a of the raised portion 50 to the intermediate portion P <b> 1 toward the rear, following the positive inclined surface of the rake face 30. Presents a straight line with a downward slope, and the front-rear range (second half part Zc) from P1 toward the rear end 50c exhibits a straight line that has turned upward, and the height of the raised part 50 from the rake face 30 is closer to the rear end. It is formed so as to gradually increase toward the part. This intermediate portion P1 is located in front of the rear end in the range up to the rear end of the positive angle of the front cutting edge 21 in the front-rear direction of the rake face 30 (the front half L1 of the rake face). Thus, in this example, when each bulging part 50 is seen from the side flank face 43 side, that is, each straight line parallel to a straight line connecting both ends of the front cutting edge 21 from the side flank face 43 side. When viewed in the direction along the (virtual straight line), the front and rear continuous state (ridge line T) at the apex 52 of the triangular mountain of the ridge 50 is divided into two parts, the front half Za and the rear half Zc in the front and rear length of the ridge 50. It is a continuous state with an upward concave connecting with a straight line. However, the continuous part (intermediate part P1) which becomes an upward concave is continuous with an upward concave radius, and the front end part 50a in the front half of the raised part 50 is raised with an upward convex curve, and the first half via the convex curve. It is connected to the front end of the straight line.

また、本例では、隆起部５０をなす三角山の頂部５２の挟角γが前方から後方に向かうに従い小さくなるものの、隆起部５０における頂部５２のすくい面３０からの高さが後方に向かうに従い高くなっていることに対応し、隆起部５０における前半部では、その三角山の、山の幅（裾野を含む三角山の幅）は、の前後方向における変化は、前方に対し後方（後半部）が大きくなっている。そして、すくい面３０側から見たとき、各隆起部５０は、中間部位よりも後方に連なる三角山の幅（裾野を含む三角山の幅）が、中間よりも前方に連なる三角山の幅（裾野を含む三角山の幅）よりも広く形成されている。なお、三角山断面において、各三角山を挟む両斜面５４，５５と、すくい面３０，３０ｂとはそれぞれ凹となす円弧で接続されている（図８参照）。 Moreover, in this example, although the included angle γ of the top portion 52 of the triangular mountain forming the raised portion 50 decreases from the front to the rear, the height from the rake face 30 of the top portion 52 in the raised portion 50 increases toward the rear. Corresponding to the increase, in the first half of the raised portion 50, the width of the mountain (the width of the triangle including the base) of the triangular mountain changes in the front-rear direction with respect to the front (back half). ) Is getting bigger. When viewed from the rake face 30 side, each raised portion 50 has a triangular mountain width (width of the triangular mountain including the skirt) connected to the rear of the intermediate portion, and a width of the triangular mountain connected to the front of the intermediate portion (width). It is formed wider than the width of the triangular mountain including the base. In addition, in the triangular mountain cross section, both slopes 54 and 55 sandwiching each triangular mountain and the rake surfaces 30 and 30b are connected to each other by a concave arc (see FIG. 8).

さて、このような本例における切削インサート１０１をホルダに固定して切削工具とし、旋盤の刃物台に取付け、被削材（例えば、ステンレス鋼製丸棒）の外周面に旋削により溝入れ加工をする場合においては次のような効果が得られる。すなわち、この溝入れ加工において発生する切り屑は、前切れ刃２１の刃先にて、その刃幅を横幅とする帯板状のものとなって生成される。そしてこの切り屑は、すくい面３０において左右一対の隆起部５０の前端部５０ａに、下面における両側端寄り部位が押し付けられつつ、後方に向けて上向きにカールするように流れる。この押し付けられにより、切り屑は、その幅方向変形を受け、硬化して、後方に向けて上向きにカールするように流れるが、その流れ過程では、前後に延びる隆起部５０にて後方にガイドされながら流れる。結果、切り屑は、横断面において上面において凹となす円弧状に変形をし、或いは、左右一対の隆起部（三角山）５０の横断面の頂部５２形状に対応した２条の、すじ状の変形が付けられながら、すくい面３０上を後方に流れる。これにより、切り屑は、横ぶれ、ないし横滑りなく後方に流れ、上向きカールされることにより、ぜんまい状に巻かれて排出される。 Now, the cutting insert 101 in this example is fixed to a holder to form a cutting tool, which is attached to a tool post of a lathe, and the outer peripheral surface of a work material (for example, a stainless steel round bar) is grooved by turning. In such a case, the following effects can be obtained. That is, the chips generated in the grooving process are generated in the form of a band plate having a width of the blade width at the cutting edge of the front cutting edge 21. Then, the chips flow so as to curl upward toward the rear side while the portions near the both end portions on the lower surface are pressed against the front end portions 50 a of the pair of left and right raised portions 50 on the rake face 30. By this pressing, the chips are deformed in the width direction, hardened, and flow so as to curl upward toward the rear. In the flow process, the chips are guided rearward by the ridges 50 extending forward and backward. It flows while. As a result, the chips are deformed into a circular arc that is concave on the upper surface in the cross section, or two streaky lines corresponding to the shape of the top 52 of the cross section of the pair of left and right raised portions (triangular mountain) 50. It flows backward on the rake face 30 while being deformed. As a result, the chips flow backward without slipping or slipping and are curled upward to be wound into a mainspring and discharged.

そして、注目されるべきは、各隆起部５０が上記したように、その頂部５２が平坦ではなく鋭利な断面三角山で前後に延びる軌道（又は凸条）をなしていることによる作用効果が得られる点である。すなわち、上記した従来の切削インサートでは、隆起部の頂部の横幅が広く、比較的平坦なもので前後に延びているため、切り屑は、その頂部（面）において横ずれし、或いは、その頂部を横に乗り越えやすい。これに対し、上記例のインサート１０１では、すくい面３０上を流れる切り屑に対し、三角山の鋭利な頂部５２が食い込みやすいから、切り屑が横ずれしにくく、その頂部５２を横に乗り越えにくい。さらに、この鋭利な山をなす左右の各隆起部５０の三角山の頂部５２相互の間隔Ｋが、前方から後方に向かうに従って小さくされているため、その隆起部５０上を後ろに流れる切り屑は、その頂部５２相互間の中央から横ずれすることなく、また、横ずれしようとしてもその中央へとガイドされる。その上、その流れ過程では、間隔Ｋが後方に向かうに従い小さくされているため、幅方向の変形を促進する作用を受けることになるから、上向きカールされてぜんまい状に巻かれる際にも、綺麗な巻のぜんまい状の切り屑となる。しかも、このような三角山の断面の頂部５２は、前方から後方に向かうに従いその鋭利性が高められているため、こうした作用効果が高められる。かくして、外周面の溝入れ加工においては、このような一対の隆起部５０による上記の作用効果が重畳することにより、すくい面３０を後方に流れる切り屑が、安定し、横ぶれもなく、ち密な巻状態のぜんまい状のものとなり、後方の傾斜状壁面４７に押し付けられて分断され、排出される。このような効果は、突っ切り加工においても同様である。 It should be noted that, as described above, each of the raised portions 50 has an action effect obtained by forming a trajectory (or ridge) extending forward and backward with a sharp triangular cross section, not the flat portion 52 as described above. It is a point. That is, in the above-described conventional cutting insert, since the width of the top of the raised portion is wide and is relatively flat and extends back and forth, the chips are laterally displaced at the top (surface) or the top is Easy to get over to the side. On the other hand, in the insert 101 of the above example, the sharp top 52 of the triangular mountain tends to bite into the chips flowing on the rake face 30, so that the chips do not easily shift laterally, and it is difficult to get over the top 52 sideways. Furthermore, since the distance K between the tops 52 of the triangular peaks of the left and right ridges 50 forming this sharp mountain is reduced from the front to the rear, the chips flowing backward on the ridges 50 are , Without being laterally displaced from the center between the top portions 52, and even when attempting to laterally shift, it is guided to the center. In addition, in the flow process, since the interval K is reduced toward the rear, it is subjected to the action of promoting the deformation in the width direction, so that it is beautiful even when curled upward and wound into a mainspring shape. It becomes a mainspring-shaped chip of naval winding. In addition, since the sharpness of the top portion 52 of the cross section of such a triangular mountain increases from the front to the rear, such an effect is enhanced. Thus, in the grooving of the outer peripheral surface, the above-described effects of the pair of raised portions 50 are superimposed, so that the chips flowing rearward on the rake face 30 are stable, do not sway, and are dense. It becomes a mainspring in a wound state, is pressed against the inclined wall surface 47 at the rear, is cut off, and is discharged. Such an effect is the same in parting-off processing.

また上記例においては、一対の隆起部５０相互の間隔Ｋが小さくなる割合（変化割合）について、一対の隆起部５０を後方においてその相互間の間隔が比例的に小さくなるように直線状に延ばしたというものでなく、その間隔Ｋが小さくなる割合について、前切れ刃２１側に位置する前寄り部位では、相対的にそれを小さくし、中間部位では、相対的にそれを大きくし、さらに、後寄り部位ではそれを小さくし、前後方向において、緩、急、緩の変化割合となるようにしている。しかも、その変化を、上面視、上記したようなカーブ変化のものとしている。さらに上記例では、一対の隆起部５０の高さを前方から後方に向けて次第に高くしている。これらにより、後方に向けて流れる切り屑は、隆起部５０の前寄り部位では、後方へのガイド作用が保持され、左右の振れが防止される上、中間部位では、幅方向の変形が円滑に促進され、しかもその高さ変化の付与により、上向きカール性を一層高めることができる。かくして、得られる切り屑は、安定し、横ぶれもなく、ち密な巻状態の綺麗な、ぜんまい状のものとなるため、一層、高い切り屑処理性が得られる。 In the above example, with respect to the ratio (change ratio) in which the distance K between the pair of raised portions 50 is reduced, the pair of raised portions 50 are linearly extended at the rear so that the distance between the raised portions 50 is proportionally reduced. It is not said that the ratio of the interval K to be reduced is relatively small at the front portion located on the front cutting edge 21 side, relatively large at the intermediate portion, and further, The rear part is made smaller so that the rate of change is slow, steep, or slow in the front-rear direction. Moreover, the change is a curve change as described above when viewed from above. Furthermore, in the above example, the height of the pair of raised portions 50 is gradually increased from the front to the rear. As a result, the chips flowing rearward are maintained in the rear guide action at the front portion of the raised portion 50 to prevent left and right vibrations, and the intermediate portion is smoothly deformed in the width direction. The upward curling property can be further enhanced by the promotion of the height change. In this way, the obtained chips are stable, free from side wobbling, and become beautiful and mainspring-like in a densely wound state, so that even higher chip disposal is obtained.

なお上記例では、上面視、頂部５２の連なりである稜線Ｔに上記したようなカーブ変化をつけたが、このような変化がなく直線となるものとしてもよい。また、上記例では、各隆起部５０を横逃げ面４３側から見たとき、隆起部５０の三角山の頂部５２における前後の連なり状態を、隆起部５０の前後長における前半部と後半部とを２つの直線で接続する上向き凹となす連なり状態としたが、図９に示したように、１つの直線（実線図示）５０ｔで接続する連なり状態の稜線Ｔとなるようにしてもよい。すなわち、隆起部をその前端部５０ａでは上向き凸曲線で隆起させ、この凸曲線の後方において１つの直線５０ｔで頂部が連なるようにしてもよい。 In the above example, the above-described curve change is applied to the ridge line T that is a series of the top portions 52 in a top view, but it may be a straight line without such a change. Further, in the above example, when each bulging portion 50 is viewed from the side of the side flank 43, the front and rear continuous state at the top 52 of the triangular mountain of the bulging portion 50 is represented by the first half portion and the second half portion in the front and rear length of the bulging portion 50. However, as shown in FIG. 9, the ridgeline T may be connected in a straight line (shown by a solid line) 50t. That is, the raised portion may be raised with an upward convex curve at the front end portion 50a, and the apex may be continuous with one straight line 50t behind the convex curve.

一方、隆起部５０の前後長における前半部と後半部とを、図４に示したような２つの直線で接続する上向き凹となす連なり状態とすることで、ぜんまい状に巻かれる切り屑が、隆起部５０の前後方向における後半部において、強く押し付けられ、上向きカール性も高められるため、一層、ち密な、ぜんまい巻となり、切り屑処理性が高められる。なお、このような頂部の前後方向の高さ変化の変形例としては、図９中において破線で示したようにしてもよい。すなわち、左右の各隆起部５０を横逃げ面４３側から見たとき、隆起部５０の三角山の頂部における前後の連なり状態を、隆起部５０の前後長において１つの連続した上向き凹曲線（破線図示）５０ｋの稜線となるようにしてもよい。なお、この場合にも、その連なりの前端部５０ａでは上向き凸曲線で隆起させ、この凸曲線の後方において、続く上向き凹曲線５０ｋの前端に連なるものとすればよい。 On the other hand, by making the front half and the rear half in the front and rear length of the raised portion 50 into a continuous state that is an upward concave connecting the two straight lines as shown in FIG. 4, the chips wound in the mainspring shape are The latter half of the raised portion 50 in the front-rear direction is strongly pressed and the upward curling property is enhanced, so that the winding becomes more dense and the mainspring winding is improved, and the chip disposal is enhanced. In addition, as a modification of the height change in the front-rear direction of such a top portion, it may be as indicated by a broken line in FIG. That is, when the left and right raised portions 50 are viewed from the side of the lateral flank 43, the front and rear continuous state at the top of the triangular mountain of the raised portion 50 is represented by one continuous upward concave curve (dashed line) in the longitudinal length of the raised portion 50. It may be a ridgeline of 50k. Also in this case, the continuous front end portion 50a may be raised with an upward convex curve and connected to the front end of the subsequent upward concave curve 50k behind the convex curve.

上記各例では、一対の隆起部５０の高さを前方から後方に向けて次第に高くしたものについて説明したが、上記もしたように本発明では、その高さの変化はないものとしても、相応の効果は得られる。理由は次のようである。上記したように、本発明のインサートにおける隆起部（三角山）の断面における両斜面（山腹）の傾斜角α、βは、前方から後方に向かうに従い大きくなり、その三角山の断面における頂部の挟角γが前方から後方に向かうに従い小さく、鋭くなるように形成されている。これにより、左右の各隆起部相互間のすくい面（平坦面）からの三角山の頂部の高さが、その前後方向において例え同じであるとしても、上面視、三角山の断面における斜面（山腹）の範囲内において、三角山の頂部を前後方向に連ねた稜線と、同一の間隔で引いた線（上記例（図３）ではカーブ曲線を含む稜線Ｔと、横方向に同一間隔で引いた線（図示せず））の各箇所（三角山断面）からみた、頂部までの高さは、前方から後方（後端寄り部位）に向かうに従い高くなる。しかも、三角山の頂部相互間の間隔は後方において小さくされているのであるから、三角山の頂部の、一対の隆起部相互間のすくい面（平坦面）からの高さが、その前後方向において同じであっても、一対の隆起部相互間におけるすくい面上を流れる切り屑を、後方に向けて一層、その幅を狭めるように幅方向において上向き凹に変形させ得る作用は得られるためである。 In each of the above examples, the height of the pair of raised portions 50 is gradually increased from the front to the rear. However, as described above, in the present invention, even if the height does not change, it is appropriate. The effect is obtained. The reason is as follows. As described above, the inclination angles α and β of both slopes (hillsides) in the cross section of the raised portion (triangular mountain) in the insert of the present invention increase from the front to the rear, and the top portion of the cross section of the triangular mountain is sandwiched between them. The angle γ is formed to be smaller and sharper from the front to the rear. As a result, even if the height of the top of the triangular mountain from the rake face (flat surface) between the left and right raised parts is the same in the front-rear direction, the slope (hillside) ), The ridge line connecting the tops of the triangular mountains in the front-rear direction, and the line drawn at the same interval (in the above example (FIG. 3), the ridge line T including the curve curve is drawn at the same interval in the horizontal direction. The height to the top as seen from each part (triangle mountain cross section) of the line (not shown) increases from the front toward the rear (part near the rear end). In addition, since the distance between the tops of the triangular mountains is reduced in the rear, the height of the top of the triangular mountains from the rake face (flat surface) between the pair of raised parts is in the front-rear direction. Even if it is the same, it is because the chip | tip which flows on the rake face between a pair of ridge parts can obtain the effect | action which can be deform | transformed into a concave upward in the width direction so that the width | variety may be narrowed further back. .

なお、上記例の切削インサート１０１におけるそのすくい面３０については、図１０、図１１に示した変形例のようにしてもよい。すなわち、このものでは、左右一対の隆起部５０の間であって、すくい面３０におけるその幅方向の中央に、前切れ刃２１寄りの部位の位置を前端として、後方の傾斜状壁面４７に向かう前後範囲部位に、所定の横幅（本例では前切れ刃２１の１／３程度の幅）で、前後方向において略一定深さで陥没する（凹む）平坦な底面をなす帯状凹部３５を設けたものである。これにより、このような本例では、すくい面３０における上面視、この帯状凹部３５領域（すくい面部分）が、上記例のすくい面３０よりも低位をなすものとなる。結果、例えば、図８中のＳ３−Ｓ３線断面図、Ｓ４−Ｓ４線断面図中にそれぞれ鎖線で示したように、その各位置における左右一対の隆起部５０間のすくい面３０ｈは、上記例におけるそれより低位となり、相対的に、この帯状凹部３５の底面であるすくい面３０ｈから見た三角山の頂部５２までの高さが高くなる。このようにすることで、前方から後方に流れる切り屑が、幅方向において上向き凹となす上下の変形を大きく受けるとしても、帯状凹部３５の底面であるすくい面３０ｈに接触することを防止、又は低減できる。なお、図１０、図１１においては、この帯状凹部３５の前後方向における中間寄り部位に、左右一対の隆起部５０における後半部位の上記仮想直線Ｇ向きの斜面５４が入り込むように位置している。 Note that the rake face 30 in the cutting insert 101 of the above example may be the modification shown in FIGS. 10 and 11. That is, in this case, it is between the pair of left and right raised portions 50 and is directed to the rear inclined wall surface 47 with the position of the portion near the front cutting edge 21 at the center in the width direction of the rake face 30 as the front end. A belt-like recess 35 having a predetermined bottom width (in this example, a width of about 1/3 of the front cutting edge 21) and having a flat bottom that is recessed (depressed) at a substantially constant depth in the front-rear direction is provided in the front-rear range portion. Is. Thereby, in this example, the top view of the rake face 30, the band-shaped recess 35 region (rake face portion) is lower than the rake face 30 of the above example. As a result, for example, the rake face 30h between the pair of left and right raised portions 50 at each position as shown by the chain lines in the cross-sectional view taken along the lines S3-S3 and S4-S4 in FIG. The height from the rake face 30h, which is the bottom surface of the band-shaped recess 35, to the top 52 of the triangular mountain is relatively high. By doing in this way, even if the chips flowing from the front to the rear are greatly subjected to the vertical deformation that becomes the upward concave in the width direction, it is prevented from coming into contact with the rake face 30h that is the bottom surface of the belt-shaped concave portion 35, or Can be reduced. In FIGS. 10 and 11, the slope 54 facing the virtual straight line G of the rear half portion of the pair of left and right raised portions 50 is located in the middle portion in the front-rear direction of the band-shaped recess 35.

本発明に係る切削インサートは、上記した各例におけるものに限定されるものではなく、その要旨を逸脱しない範囲において適宜に変更して具体化できる。上記例では２コーナタイプのものとして具体化したが、１コーナ又は３コーナ以上の切削インサートにおいても適用できる。左右一対の隆起部の頂部相互間の間隔の前後方向における変化割合、或いはその高さの変化割合も、加工条件等に応じ適宜に設定すればよい。また、上記例では、ポジタイプの切れ刃のものとして具体化したが、粗削り等、必要に応じてネガタイプのものとしても具体化できる。また、本発明に係る切削インサートは外周面への溝入れ（縦送り）において説明したが、端面への溝入れにも、さらには、縦送り状態で横送りする場合にも適用できる。 The cutting insert according to the present invention is not limited to those in the above-described examples, and can be embodied with appropriate modifications within a range not departing from the gist thereof. In the above example, it is embodied as a two-corner type, but it can be applied to a cutting insert having one corner or three corners or more. What is necessary is just to set suitably the change rate in the front-back direction of the space | interval between the top parts of a pair of right and left protruding parts, or the change ratio of the height according to processing conditions etc. In the above example, a positive type cutting edge is used, but a negative type such as rough cutting may be used as necessary. Further, the cutting insert according to the present invention has been described in the description of grooving (vertical feed) to the outer peripheral surface, but it can also be applied to grooving to the end face and also to the case of lateral feed in the vertical feed state.

２１前切れ刃
２３横切れ刃
３０すくい面
４０前逃げ面
４３横逃げ面
５０、５０左右一対の隆起部
５０ａ隆起部の前端部
５０ｋ上向き凹曲線
５４，５５三角山の斜面
１０１切削インサート
Ｓ２−Ｓ２線前切れ刃に平行な直線
５２隆起部の三角山の頂部
Ｋ頂部相互の間隔
α、β 三角山の斜面の傾斜角
γ 三角山の断面における頂部の挟角
Ｇ前切れ刃に垂直に、すくい面において前後に引いた直線（仮想直線）
Ｐ１隆起部の前後方向の中間部位
Ｈ１，Ｈ２，Ｈ３隆起部の三角山の頂部のすくい面からの高さ
Ｚａ隆起部の前後長における前半部
Ｚｃ隆起部の前後長における後半部 21 Front cutting edge 23 Horizontal cutting edge 30 Rake face 40 Front relief face 43 Side relief faces 50, 50 A pair of left and right raised parts 50a Upward end parts 50k Upward concave curves 54, 55 Triangular mountain slope 101 Cutting insert S2-S2 line Straight line 52 parallel to the front cutting edge K The top of the triangular mountain K of the protuberance α, β Inclination angle γ of the triangular mountain slope Gap angle of the top in the cross section of the triangular mountain Rake surface perpendicular to the front cutting edge A straight line drawn back and forth in (virtual straight line)
P1 Middle part H1, H2, H3 in the front-rear direction of the ridge part Height Za from the rake face of the top of the triangular mountain Za Front part Zc in the longitudinal part of the ridge part The latter part in the longitudinal part of the ridge part

Claims

A front cutting edge is provided at the crossing ridge of the rake face and the front flank, and the front cutting edge is sandwiched in the width direction of the flank so that the cross ridge is formed between the side flank and the rake face located on both sides. A cutting insert comprising a blade,
The rake face is provided with a pair of left and right raised portions that are symmetrically arranged with a straight line drawn back and forth on the rake face perpendicular to the front edge at the middle position of the edge width of the front edge, Each ridge extends continuously in the front-rear direction, and is a straight line parallel to the straight line connecting both ends of the front cutting edge, and exhibits a cross-sectional shape of a triangular mountain when cut from the rake face side. ,
The distance between the tops of the triangular peaks of the left and right ridges decreases from the front to the rear,
In addition, the ridges on the left and right sides of the triangular mountain section increase in inclination angle of both slopes from the front to the rear, and the apex angle in the triangular mountain section decreases from the front to the rear. A cutting insert characterized by being formed as follows.

The rate at which the interval decreases from the front toward the rear is such that the middle part in the front-rear direction of each of the left and right ridges is larger than the front part and the rear part. The cutting insert according to claim 1.

The height from the rake face of the top of the triangular mountain of each of the left and right ridges is increased from the front toward the rear end portion of the rear, according to claim 1 or 2. Cutting insert.

When the left and right raised portions are viewed from the side of the lateral relief surface in a direction along a straight line parallel to a straight line connecting both ends of the front cutting edge, the front and back continuous state at the top of the triangular mountain of the raised portion, The front half and the rear half of the raised part are connected in a straight line connecting the upper half and the rear half, and the front end of the front half of the series rises with an upward convex curve and continues behind the convex curve. 4. The intermediate portion including a connection portion that is connected to a front end of a straight line of the front half portion and connects the front half portion and the rear half portion by two straight lines, and is connected by an upward concave curve. Cutting inserts.

When the left and right raised portions are viewed from the side of the lateral relief surface in a direction along a straight line parallel to a straight line connecting both ends of the front cutting edge, the front and back continuous state at the top of the triangular mountain of the raised portion, It is a continuous state with an upward concave curve in the front and rear length of the raised portion, and the front end portion of the continuous portion is raised with an upward convex curve and is connected to the front end of the upward concave curve following the convex curve. The cutting insert according to claim 3.