Patent Description:
The clamping intensity and rigidity of the cutting blade have a significant influence on the cutting ability thereof in the course of cutting. Particularly, the clamping stability of the cutting blade has an essential influence on cutting efficiency and precision of the cutting blade. The cutting blade stably clamped is high in cutting efficiency, high in precision and long in service life. The cutting blade clamped unstably easily vibrates to cause rapid wear of the cutting blade in cutting, even chipping, which greatly shortens the service life of the cutting blade. To improve the cutting performance of the cutting blade in the industry, the cutting blade is designed as a plurality of cutting blade clamping structures, such as briquetting clamping, lever clamping, wedge clamping and hole clamping, thereby satisfying application of the cutting blade in different cutting conditions. The concentrically clamped cutting blade is applied extensively due to very excellent clamping intensity and rigidity and convenience to load/unload. Due to tolerance on manufacturing dimension of the cutting blade side surface and for the purpose of ensuring that the side surface of each cutting blade can be completely in contact with the side surface of the cutter groove of the cutting tool, a center of a fastener shall be generally moved inward the cutter groove for a certain distance relative to a center of a round hole of the cutting blade when the fastener clamps the cutting blade through the central hole, so that the central axis of the cutting blade is capable of moving toward the side surface from the central axis of the cutting blade when the cutting blade is clamped. This ensures that a bottom surface and the side surface of the cutting blade are in good contact with each other when it is applied in the cutter groove and the cutting performance of the cutting blade is stable.

Although the cutting blade clamped by the concentrically circumferential central hole has the above advantages in cutting, the center of the fastener is arranged away from the center of the round hole of the cutting blade, and the fastener can only contact the central hole of the cutting blade in a small-area (or point) manner. Even if enough clamping force can be provided to the cutting blade, the fastener is easily distorted to induce cutting vibration in many directions in cutting, and the cutting efficiency is low when the cutting blade is finished. Furthermore, the cutting blade is easily chipped at the time of cutting at high speed, and the cutting life is short.

<CIT> relates to a cutting tool comprising a cutting tool holder having mounted thereon a cutting insert. Said cutting tool holder comprising a body formed with a seat and a seat bore configured for accommodating therein a fastening member, and wherein said holder also comprises an anchoring element received within the body of the holder, said fastening element being configured for secured engagement with said anchoring element and being free of such engagement with the seat bore. <CIT> discloses a clamp mechanism of a tip for pressing the tip, in which a fitting hole is formed through a tip body, by the use of a clamp member having a shaft portion inserted into the fitting hole and a head portion with an outer diameter larger than that of the shaft portion and thus clamping the tip to a tip fitting seat.

The aim of the present invention is to overcome the deficiencies of the prior art and to provide cutting tool having a polygonal cutting blade having a circular arc-shaped groove in a hole that is reliable and stable to position and long in service life.

In order to solve the above technical problems, the present invention adopts the following technical solution according to independent claim <NUM>.

A cutting tool comprising a polygonal cutting blade, a cutter body, and a fastening screw, wherein the cutter body is provided with at least one cutter groove. A number of the cutting blade corresponds to a number of the cutter groove and the polygonal cutting blade has a circular arc-shaped groove in a hole and comprises a blade body composed of an upper surface, a lower surface and a plurality of main side surfaces connecting the upper surface and the lower surface. The blade body is provided with a central hole penetrating through the upper surface and the lower surface, and the blade body is centrally symmetrical about a central axis of the central hole. The main side surfaces intersect the upper surface to form a main cutting edge and in the plurality of main side surfaces at least one set of positioning side surface comprised of adjacent two of the main side surfaces is provided, wherein the cutter blade is arranged in the cutter groove and is positioned by the set of the positioning side surfaces. An inner surface of the central hole has at least one circular arc-shaped groove fitting with a surface of the fastening screw for fixing the cutting blade and the fastening screw concentrically contacts the at least one circular arc-shaped groove in the central hole and presses the cutting blade into the cutter groove. A number of the circular arc-shaped groove corresponds to a number of the set of positioning side surfaces. Each circular arc-shaped groove directly faces toward an intersection of the two main side surfaces of the set of positioning side surfaces and a groove central axis of the circular arc-shaped groove has an offset distance from the central axis. A continuous arc-shaped linear contact is formed between the circular arc-shaped grooves and the fastening screw in a normal section of the central axis of the blade, and the offset distance is S, and <NUM> ≤ S ≤ <NUM>.

According to an embodiment, in the plurality of main side surfaces, at least two sets of positioning side surface are provided. The number of the circular arc-shaped groove corresponds to the number of the sets of the positioning side surface. The two adjacent circular arc-shaped grooves are connected smoothly through an angular groove.

According to an embodiment, in the positioning side surface, the adjacent two of the main side surfaces are smoothly connected through an angular side surface, and the circular arc-shaped grooves directly face toward the angular side surface.

According to an embodiment, the circular arc-shaped grooves include groove cylindrical surfaces, first groove cambered surfaces and second groove cambered surfaces.

According to an embodiment, the circular arc-shaped grooves have groove symmetrical surfaces. Each groove symmetrical surface is an angular equally-dividing surface of an angle between the two main side surfaces in the corresponding positioning side surface. Each angular groove has an angular groove symmetrical surface, and the groove symmetrical surfaces and the angular groove symmetrical surfaces penetrate through the central axis.

According to an embodiment, in any plane that is parallel to the upper surface and intersects the groove cambered surface, a distance between each angular groove and the central axis on the corresponding angular groove symmetrical surface is h', and a distance between each circular arc-shaped groove adjacent to the corresponding angular groove and the central axis on the corresponding groove symmetrical surfaces is h, both of which meet: <NUM>≤h'-h≤<NUM>.

According to an embodiment, each angular groove comprises an angular groove cylindrical surface, an angular groove cambered surface and an angular groove conical surface, and the angular groove cylindrical surfaces, the angular groove cambered surfaces and the angular groove conical surfaces correspond to the groove cylindrical surfaces the first groove cambered surfaces and the second groove cambered surfaces one by one, and the corresponding faces have the same height.

According to an embodiment, a radius of the groove cylindrical surface of each circular arc-shaped groove is R, and a radius of the angular groove cylindrical surface of each angular groove is R', both of which meet: <NUM>. 4R≤R'≤<NUM>.

According to an embodiment, in the positioning side surface, the two main side surfaces are symmetrical about the corresponding groove symmetrical surface.

According to an embodiment, the blade body is a parallelogram plate shaped blade body. Two sets of positioning side surfaces are arranged, including one set of main side surfaces at both sides of an acute angle, and the other set of main side surfaces at both sides of another acute angle. Two circular arc-shaped grooves are arranged, directly facing toward two angular side surfaces respectively.

According to an embodiment, the blade body is a square plate-shaped blade body. Four sets of positioning side surfaces are arranged, and the main side surfaces at both sides of every right angle are a set of positioning side surfaces. Four circular arc-shaped grooves are arranged, directing facing toward four angular side surfaces respectively.

According to an embodiment, the blade body has a horizontal middle section and is symmetrical about the horizontal middle section, and the inner surfaces of a central hole above the horizontal middle section and the central hole below the horizontal middle section are both provided with circular arc-shaped grooves.

Compared with the prior art, the present invention has the following advantages.

blade body; <NUM>. upper surface; <NUM>. lower surface; <NUM>. main side surface; <NUM>. angular side surface; <NUM>. central hole; <NUM>. circular arc-shaped groove; <NUM>. groove symmetrical surface; <NUM>. groove cylindrical surface; <NUM>. first groove cambered surface; <NUM>. second groove cambered surface; <NUM>. groove central axis; <NUM>. angular groove; <NUM>. angular groove symmetrical surface; <NUM>. angular groove cylindrical surface; <NUM>. angular groove cambered surface; <NUM>. angular groove conical surface; <NUM>. central axis; <NUM>. main cutting edge; <NUM>. angular cutting edge; <NUM>. horizontal middle section; <NUM>. cutter body; <NUM>. cutter groove; <NUM>. fastening screw.

The present invention will be further clarified based on the following figures and embodiments.

As shown in <FIG>, a polygonal cutting blade having an arc-shaped groove in a hole of this embodiment includes a blade body <NUM> composed of an upper surface <NUM>, a lower surface <NUM> and a plurality of main side surfaces <NUM> connecting the upper surface <NUM> and the lower surface <NUM>. The blade body <NUM> is provided with a central hole <NUM> penetrating through the upper surface <NUM> and the lower surface <NUM>, and the blade body <NUM> is centrally symmetrical about a central axis <NUM> of the central hole <NUM>. The main side surfaces <NUM> intersect the upper surface <NUM> to form a main cutting edge <NUM>. In the plurality of main side surfaces <NUM>, at least one set of positioning side surface comprised of two adjacent main side surfaces <NUM> is provided. An inner surface of the central hole <NUM> has at least one circular arc-shaped groove <NUM> fitting with the surface of a fastening screw <NUM> for fixing the cutting blade. A number of the circular arc-shaped groove <NUM> corresponds to a number of the set of the positioning side surface, each circular arc-shaped groove <NUM> directly faces toward an intersection of two main side surfaces <NUM> of a set of positioning side surface, and a groove central axis <NUM> of the circular arc-shaped groove <NUM> has an offset distance from the central axis <NUM>.

In this embodiment, the blade body <NUM> is exemplified by a parallelogram plate shaped cutter body. Two sets of the positioning side surfaces are arranged on the blade body <NUM>. The positioning side surfaces are comprised of the two adjacent main side surfaces <NUM>, including one set of main side surfaces <NUM> at both sides of an acute angle, and the other set of main side surfaces <NUM> at both sides of another acute angle. Two circular arc-shaped grooves <NUM> are arranged on the diagonals of two acute angles. The two circular arc-shaped grooves <NUM> are connected by a straight line or the protruding camber line to avoid the fastening screw <NUM>.

According to the invention, the offset distance S (the distortion of the fastener caused by the cutting force may be less than an S value if the S value is excessive, so that a plurality of sets of continuous camber line contact cannot be formed. If the S value is small, the fastener may contact the groove outside the inner side of the blade first, but not contact the groove corresponding to the positioning surface when a manufacturing error is large, so that unstable clamping will be formed and the service life of the blade will be reduced) between the groove central axis <NUM> and the central axis <NUM> ranges from <NUM> to <NUM>. In this embodiment, S is <NUM>.

When the cutting blade in this embodiment is applied, the cutting blade is mounted in the cutter groove <NUM> of the cutter body <NUM> and is pressed by the fastening screw <NUM>. In this embodiment, when in use, the blade body <NUM> is secured into the cutter groove <NUM> of the cutter body <NUM> by the fastening screw <NUM>, and the fastening screw <NUM> penetrates through the central hole <NUM>. As shown in <FIG>, the main side surfaces <NUM> at two corresponding sides of the acute angle at top right corner are positioning side surfaces, and the blade body <NUM> is pressed into the cutter groove <NUM> by screwing down the fastening screw <NUM>. After the fastening screw <NUM> is screwed down, a center of the fastening screw <NUM> is O2 (on the groove central axis <NUM>), and a center of the central hole <NUM> is O1 (on the central axis <NUM>), between which there is a certain distance. This distance is the offset distance S. A threaded hole (not shown in the figure) of the corresponding fastening screw <NUM> on the cutter body <NUM> has an offset distance S from the central hole <NUM>. At this time, one circular arc-shaped groove <NUM> concentrically contacts and fits with a surface of the fastening screw <NUM>, and the circular arc-shaped groove <NUM> is propped against the fastening screw <NUM> if the fastening screw <NUM> is eccentrically pressed, thereby forming the linear contact of continuous arc-shaped contact in the normal section of the central axis <NUM> by the fastening screw <NUM> and the central hole <NUM>. Therefore, the fastener <NUM> can enclose and clamp the cutting blade circumferentially at a large angle, a direction of the clamping force is essentially vertical to the contacted camber line and directs to the positioning surface, the circular arc-shaped groove <NUM> at the top right corner in the central hole <NUM> contacts the camber line of the fastening screw <NUM> to form continuous multi-point repeated positioning clamping, thereby greatly improving the clamping rigidity, intensity and stability of the cutting blade. Meanwhile, with increasing cutting force and distortion of the fastening screw <NUM>, the circular arc-shaped groove <NUM> at the bottom left corner relative to the circular arc-shaped groove <NUM> at the top right corner will contact the fastening screw <NUM> by accurately designing the offset distance S between the circular arc-shaped groove <NUM> and the central axis <NUM>, thereby finally forming two sets of independent continuous multi-point repeated positioning clamping. In other words, with changing cutting force, the central hole <NUM> of the cutting blade may be automatically adjusted between a set of continuous multi-point repeated positioning clamping restraints and at most two sets of independent continuous multi-point repeated positioning clamping restraints, and the clamping forces of all circular arc-shaped grooves <NUM> can be distributed reasonably, therefore, cutting vibration can be avoided in case of cutting with high efficiency and high cutting force, and cutting life and precision of the cutting blade can be still ensured. Due to one or two sets of linear, arc-shaped contacts between the two circular arc-shaped grooves <NUM> and the fastening screw <NUM>, the deformable direction and area coverage of the fastening screw <NUM> in the central holes <NUM> of the circular blade are greatly reduced, cutting vibration is restrained, and cutting precision, processing efficiency and cutting life are improved.

In this embodiment, in each positioning side surface, the two adjacent main side surfaces <NUM> are smoothly connected through the angular side surface <NUM>, and the circular arc-shaped grooves <NUM> directly face toward the angular side surfaces <NUM>. Each angular side surface <NUM> intersects the upper surface <NUM> to form an angular cutting edge <NUM>.

In this embodiment, the two adjacent circular arc-shaped grooves <NUM> are smoothly connected through a corresponding angular groove <NUM>. The two circular arc-shaped grooves <NUM> are correspondingly provided with two angular grooves <NUM>, respectively. The two angular grooves <NUM> are located on the diagonal between two obtuse angles of the parallelogram plate shaped cutter body.

In this embodiment, each of the circular arc-shaped grooves <NUM> comprises a groove cylindrical surface <NUM>, a first groove cambered surface <NUM> and a second groove cambered surface <NUM>. Each angular groove <NUM> comprises an angular groove cylindrical surface <NUM>, an angular groove cambered surface <NUM> and an angular groove conical surface <NUM>. The angular groove cylindrical surfaces <NUM>, the angular groove cambered surfaces <NUM> and the angular groove conical surfaces <NUM> correspond to the groove cylindrical surfaces <NUM>, the first groove cambered surfaces <NUM> and the second groove cambered surface <NUM> one by one, all of the corresponding surfaces have the same height. The circular arc-shaped grooves <NUM> have the groove symmetrical surfaces <NUM>. Each groove symmetrical surface <NUM> is an angular equally-dividing surface (equivalent to a surface where the corresponding diagonal between the two acute angles is) of an angle between the two main side surfaces <NUM> in the positioning side surface, each angular groove <NUM> has an angular groove symmetrical surface <NUM> (equivalent to a surface where the diagonal between the two obtuse angles is), and the groove symmetrical surfaces <NUM> and the angular groove symmetrical surfaces <NUM> penetrate through the central axis <NUM> and are vertical to each other.

In this embodiment, a radius of the groove cylindrical surface <NUM> of each circular arc-shaped groove <NUM> is R', and a radius of the angular groove cylindrical surface <NUM> of each angular groove <NUM> is R, both of which meet: <NUM>. 4R≤R'≤<NUM>. In other words, in any plane that is parallel to the upper surface <NUM> and intersects the corresponding first groove cambered surface <NUM>, a distance between each angular groove <NUM> and the central axis <NUM> on the corresponding angular groove symmetrical surface <NUM> is h', and a distance between each circular arc-shaped groove <NUM> adjacent to the corresponding angular groove <NUM> and the central axis <NUM> on the corresponding groove symmetrical surface <NUM> is h, both of which meet: <NUM>≤h'-h≤<NUM>. The angular groove <NUM> is provided to: firstly, connect two adjacent circular arc-shaped grooves <NUM>. Secondly, ensure that the fastener <NUM> is capable of automatically adjusting the ability to form one or a plurality of sets of continuous arc-shaped repeated positioning clamping restraints in the central hole of the cutting blade with changing cutting force when a plurality of circular arc-shaped grooves are provided.

In this embodiment, the two main side surfaces <NUM> are symmetrical about the groove symmetrical surface <NUM> in the each positioning side surface.

In this embodiment, after the fastening screw <NUM> is fastened in the central hole <NUM>, a cooperative relationship between the groove cylindrical surfaces <NUM>, the first groove cambered surfaces <NUM> and the second groove cambered surface <NUM> is shown in <FIG>. That is to say, in a horizontal plane that is parallel to the upper surface <NUM> and intersects the first groove cambered surfaces <NUM> through the fastening screw <NUM>, a conical surface of the fastening screw <NUM> and the first groove cambered surfaces <NUM> are overlapped (the conical surface of the fastening screw <NUM> and the first groove cambered surface <NUM> are overlapped as a circular arc line). In a vertical section (equivalent to a section overlapped with the groove symmetrical surfaces <NUM>) vertical to the horizontal plane, the conical surface of the fastening screw <NUM> intersects the first groove cambered surfaces <NUM> at a point P (an overlapped circular arc line consisting of a plurality of points P). The point P where the conical surface of the fastening screw <NUM> intersects the first groove cambered surfaces <NUM> is located at a certain point of the conical surface of the fastening screw <NUM>.

In addition to this embodiment, the cutting blade may be a double blade cutting blade.

As shown in <FIG>, the cutting tool of this embodiment comprises a cutter body <NUM> and a fastening screw <NUM>. The cutting tool further comprises the previously mentioned square cutting blade. The cutter body <NUM> is a square cutter bar, only one cutter groove <NUM> is defined in the cutter body <NUM>, and the polygonal cutting blade fits with a positioning surface of a cutter groove <NUM> through a set of positioning side surfaces. The fastening screw <NUM> concentrically contacts at least one circular arc-shaped groove <NUM> in the central hole <NUM> and the cutting blade is pressed into the cutter groove <NUM>.

In this embodiment, the circular arc-shaped grooves <NUM> and the fastening screw <NUM> form two sets of continuous arc-shaped repeated positioning clamping in final positioning.

In this embodiment, when the fastening screw <NUM> is screwed down, the fastening screw <NUM> concentrically contacts the circular arc-shaped groove <NUM> at the top right corner, and then concentrically contacts the circular arc-shaped groove <NUM> at the bottom left corner. If the fastening screw <NUM> is unscrewed, the circular arc-shaped groove <NUM> at the bottom left corner departs from the fastening screw <NUM>, and then the circular arc-shaped groove <NUM> at the top right corner departs from the fastening screw <NUM>.

In this embodiment, each of the two circular arc-shaped grooves <NUM> may be installed and positioned once, and the blade body <NUM> can be applied twice and can be installed reversely at two acute angles. That is to say, the blade body <NUM> can be used again at rotated <NUM>°. Two positioning and pressing ways are the same.

According to the cutting tool provided by the present invention, the fastening screw <NUM> and the circular arc-shaped grooves <NUM> in the central hole <NUM> of the cutting blade are concentrically designed, and the fastening screw <NUM> is not required to deviate from a center of a round hole of the cutting blade when the cutting tool is made, so that simple production is realized and good contact between the polygonal cutting blade and the side surface of the cutter groove <NUM> in batches is ensured. The fastening screw <NUM> forms circumferential omnibearing repeated positioning clamping of the circular arc-shaped grooves <NUM> for the positioning side surfaces and cutting area of the cutting blade, thereby effectively controlling unfavorable distortion directions and areas of the fastener, and effectively attenuating vibration of the cutting blade in cutting. Such cutting tools still have high-quality surface processing ability and excellent dimension precision in case of large overhang length, cutting depth and feeding, and thus can be applied to efficient rough cutting and precise cutting, with very extensive application range.

As shown in <FIG>, the polygonal cutting blade of the cutting tool of this embodiment is similar to the one of Embodiment <NUM>, and the differences therebetween are as follows.

In this embodiment, the blade body <NUM> is of a square plate shape, four sets of positioning side surfaces are arranged, and the main side surfaces <NUM> at both sides of every right angle are a set of positioning side surfaces. Four circular arc-shaped grooves <NUM> are arranged to directly face toward four angular side surfaces <NUM> respectively. Four angular grooves <NUM> directly face toward the four main side surfaces <NUM> respectively.

In this embodiment, a center distance between the circular arc-shaped grooves <NUM> on the same straight line is <NUM>.

In this embodiment, the positioning and installation process of the polygonal cutting blade is essentially shown in Embodiment <NUM>. However, four circular arc-shaped grooves <NUM> are arranged in this embodiment, including a first circular arc-shaped groove <NUM>, a second circular arc-shaped groove <NUM>, a third circular arc-shaped groove <NUM> and a fourth circular arc-shaped groove <NUM> in sequence. The first and third circular arc-shaped grooves <NUM> are located on the same straight line through the central axis <NUM>, and the second and fourth circular arc-shaped grooves <NUM> are located in the same straight line through the central axis <NUM>. Thus, the fastening screw <NUM> concentrically contacts the first circular arc-shaped groove <NUM> first to form a set of continuous arc-shaped repeated positioning clamping. With increasing cutting force and distortion of the fastening screw <NUM>, the fastening screw <NUM> concentrically contacts the third circular arc-shaped groove <NUM> (due to the fact that the fastening screw <NUM> is distorted in a direction relative to the first circular arc-shaped groove <NUM>), so as to form two sets of continuous arc-shaped repeated positioning clamping. Then, with increasing distortion of the fastening screw <NUM>, the fastening screw <NUM> concentrically contacts the second circular arc-shaped groove <NUM> and the fourth circular arc-shaped groove <NUM> at both sides in sequence, so as to form four sets of continuous arc-shaped repeated positioning clamping finally.

In this embodiment, the blade body <NUM> has a horizontal middle section <NUM> and is symmetrical about the horizontal middle section <NUM>, and the inner surfaces of a central hole <NUM> above the horizontal middle section <NUM> and the central hole <NUM> below the horizontal middle section <NUM> are both provided with circular arc-shaped grooves <NUM>. A cutting edge <NUM> is formed between the lower surface <NUM> and the side surface <NUM>, namely, the cutting blade of this embodiment is a double blade with the completely same structures at both surfaces. Each surface can be applied four times after rotated <NUM>° once, so as to ensure that at least one circular arc-shaped groove <NUM> concentrically contacts and fits with the fastening screw <NUM>. Double surfaces can be applied eight times.

In addition to this embodiment, the polygonal cutting blade may be a single cutting blade as well.

<FIG> shows the cutting tool of this embodiment. The cutter body <NUM> is a disc cutter bar with an axis, the cutter body <NUM> is provided with four cutter grooves <NUM>. The cutting tool further comprises the previously mentioned polygonal cutting blade. The number of cutting blades corresponds to the number of cutter grooves <NUM>, the cutter blades are arranged in the cutter grooves <NUM> and are positioned by a set of positioning side surfaces, and the fastening screw <NUM> concentrically contacts at least one circular arc-shaped groove <NUM> in the central hole <NUM> and presses the cutting blade into the cutter groove <NUM>.

With increasing cutting force and distortion of the fastening screw <NUM>, the fastening screw <NUM> concentrically contacts the circular arc-shaped grooves <NUM>. The circular arc-shaped grooves <NUM> and the fastening screw <NUM> form four sets of continuous multi-point repeated positioning clamping in final positioning.

The cutting tool of this embodiment is similar to Embodiment <NUM>, and the differences therebetween are as follows.

In this embodiment, one circular arc-shaped groove <NUM> is provided on an inner surface of the central hole <NUM>, and one circular arc-shaped groove <NUM> and the fastening screw <NUM> form repeated positioning clamping. The polygonal cutting blade of this embodiment can be positioned and installed once.

In addition to this embodiment, the polygonal cutting blade may be a double cutting blade as well.

In the above embodiment <NUM>, embodiment <NUM> and embodiment <NUM>, the blade body <NUM> is constituted by the quadrilateral cutting blade through single and double groove structures. There are <NUM>-<NUM> circular arc-shaped grooves <NUM> respectively. When the blade body <NUM> is put into use, the circular arc-shaped grooves <NUM> in the central <NUM> are clamped and restrained, changing from one to four sets of continuous arc-shaped repeated positioning clamping.

In the above embodiment <NUM> and embodiment <NUM>, the quadrangular cutting blade is mainly applied to turning or milling, but the present invention is not limited to this. According to different processing methods, the cutting blade of the cutting tool can be designed as other shapes applied to boring and drilling tools, etc..

Claim 1:
A cutting tool comprising a polygonal cutting blade, a cutter body (<NUM>), and a fastening screw (<NUM>), wherein the cutter body (<NUM>) is provided with at least one cutter groove (<NUM>), a number of the cutting blade corresponds to a number of the cutter groove (<NUM>); the polygonal cutting blade having a circular arc-shaped groove in a hole and comprising a blade body (<NUM>) composed of an upper surface (<NUM>), a lower surface (<NUM>) and a plurality of main side surfaces (<NUM>) connecting the upper surface (<NUM>) and the lower surface (<NUM>); the blade body (<NUM>) is provided with a central hole (<NUM>) penetrating through the upper surface (<NUM>) and the lower surface (<NUM>), and the blade body (<NUM>) is centrally symmetrical about a central axis (<NUM>) of the central hole (<NUM>); the main side surfaces (<NUM>) intersect the upper surface (<NUM>) to form a main cutting edge (<NUM>); in the plurality of main side surfaces (<NUM>), at least one set of positioning side surface comprised of adjacent two of the main side surfaces (<NUM>) is provided; wherein: the cutter blade is arranged in the cutter groove (<NUM>) and is positioned by the set of the positioning side surfaces; an inner surface of the central hole (<NUM>) has at least one circular arc-shaped groove (<NUM>) fitting with a surface of the fastening screw (<NUM>) for fixing the cutting blade and the fastening screw (<NUM>) concentrically contacts the at least one circular arc-shaped groove (<NUM>) in the central hole (<NUM>) and presses the cutting blade into the cutter groove (<NUM>); a number of the circular arc-shaped groove (<NUM>) corresponds to a number of the set of positioning side surfaces; each circular arc-shaped groove (<NUM>) directly faces toward an intersection of the two main side surfaces (<NUM>) of the set of positioning side surfaces, and a groove central axis (<NUM>) of the circular arc-shaped groove (<NUM>) has an offset distance from the central axis (<NUM>); a continuous arc-shaped linear contact is formed between the circular arc-shaped grooves (<NUM>) and the fastening screw (<NUM>) in a normal section of the central axis of the blade, and the offset distance is S, and <NUM>≤S≤<NUM>.