Rotary cutting tool

Abstract

The problem to be solved by the present invention is to provide a rotary cutting tool with a helical angle that can be easily manufactured compared to conventional methods. It comprises: an insert (20), the cutting edge (E) being at least the ridge line of the rake face and flank face, formed of a hard sintered body containing diamond and / or cubic boron nitride; and a body (10), the insert (20) being engaged with the back surface (111) of a seat of the body, the back surface (111) of the seat being planar and inclined relative to the axis (Ax), the rake face and flank face being curved surfaces having a predetermined clearance angle, a predetermined rake angle, and a predetermined helical angle. Particularly preferably, when viewed in the vertical direction as a plane perpendicular to the back surface (111) of the seat and including the axis (Ax), one end of the back surface (111) of the seat engaging with the insert (20) is located in front of the axis (Ax) in the direction of rotation of the rotary cutting tool, and the rear end of the back surface (111) of the seat is located behind the axis (Ax) in the direction of rotation of the rotary cutting tool. In conventional rotary cutting tools, the two ends of the back of the base are located behind the axis (Ax) in the direction of rotation.

Description

Technical Field

[0001] This invention relates to a rotary cutting tool for processing non-ferrous metals such as aluminum and aluminum alloys, wood, resin, CFRP, etc., with a cutting edge formed from a hard sintered body including polycrystalline diamond (PCD) sintered body and / or cubic boron nitride (CBN) sintered body, and having a helix angle of the cutting edge. Background Technology

[0002] There are cases where the cutting edge of a rotary cutting tool is formed from a hard sintered body. In conventional rotary cutting tools with a helix angle, when the cutting edge is formed from a hard sintered body, it is manufactured by grinding a round bar formed by sintering PCD together with a cemented carbide body. The hard sintered body is arranged in a helical shape according to the helix angle of the cutting edge (Patent Documents 1-4, etc.).

[0003] Patent Document 1: Japanese Patent No. 2934927

[0004] Patent Document 2: Japanese Patent Application Publication No. 2002-18630

[0005] Patent Document 3: Japanese Utility Model Publication No. 5-2247

[0006] Patent Document 4: Japanese Patent No. 3477183

[0007] In the past, rotary cutting tools required the preparation of cylindrical parts such as round bars to integrate hard sintered bodies at different angles according to the size of the helix angle, which was not suitable for manufacturing a wide variety of products. Summary of the Invention

[0008] The present invention was made in view of the above-mentioned actual situation, and the problem to be solved is to provide a rotary cutting tool with a cutting edge having a helical angle that can be easily manufactured compared with the past.

[0009] The rotary cutting tool of the present invention, which solves the above-mentioned problems, comprises: an insert, wherein at least the cutting edge forming the ridge where the rake face and the flank face intersect is formed of a hard sintered body comprising diamond and / or cubic boron nitride; and a body to which the insert is joined.

[0010] The back of the aforementioned seat is flat and inclined relative to the axis of the aforementioned rotary cutting tool, while the rake face and flank face are curved surfaces.

[0011] Within the effective range of the aforementioned cutting edge, the difference between the maximum and minimum values ​​of the helix angle at the axis of the aforementioned rotary cutting tool, as well as the clearance angle and rake angle observed from a vertical section, is less than 10°.

[0012] When viewed vertically in a plane perpendicular to the back of the aforementioned seat and containing the aforementioned axis, one end of the back of the aforementioned seat, which engages with the aforementioned blade and is referenced to the aforementioned axis direction, is located in front of the aforementioned rotary cutting tool in the direction of rotation, and the other end is located behind the aforementioned axis ...

[0013] Furthermore, the difference between the maximum and minimum values ​​of the aforementioned helix angle, clearance angle, and rake angle is 5° or less, 3° or less, 2° or less, and more preferably 0°. The effective range of the cutting edge refers to the range between one end and the other end of the cutting edge formed on the insert.

[0014] In addition, it is preferable that the radial lengths at both ends of the blade are shorter than the length in the middle.

[0015] More preferably, the blade is composed of a laminate, which is a laminate of a hard sintered body layer composed of a hard sintered body and a hard alloy layer made of hard alloy forming a mating surface that engages with the seat, wherein at the end in front of the rotation direction, the axial side of the rake face is the hard alloy layer.

[0016] The rotary cutting tool of the present invention has the above-described structure, thereby achieving high performance by controlling the size of the back angle, front angle, and helix angle within a specified range, and is easy to manufacture because the back of the seat is flat. Attached Figure Description

[0017] Figure 1 This is a side view of the rotary cutting tool according to Embodiment 1. Figure 1 It is a diagram of a plane that is perpendicular to the back of the seat and contains the aforementioned axis, viewed in the vertical direction.

[0018] Figure 2 It refers to the points from which the rotary cutting tool of Embodiment 1 is located in the direction perpendicular to the axis of the axis and at positions S to Z of the axis. Figure 1 The left-side view of the end face and sectional view. Distance from the front end of the main body ( Figure 1 The distances (on the left side of the paper) are as follows: S is 0mm, T is 5mm, U is 10mm, V is 15mm, W is 20mm, X is 25mm, Y is 30mm, and Z is 34mm.

[0019] Figure 3 This is a side view of the main body of Embodiment 1.

[0020] Figure 4 This is a side view of the rotary cutting tool according to Embodiment 2.

[0021] Figure 5It refers to the points located at positions S to X of the axis perpendicular to the axis of the rotary cutting tool in Embodiment 2. Figure 4 The left-side view of the end face and sectional view. Distance from the front end ( Figure 4 The distances (on the left side of the paper) are as follows: S is 0mm, T is 5mm, U is 10mm, V is 15mm, W is 20mm, and X is 23mm.

[0022] Figure 6 This is a side view of the main body of embodiment 2.

[0023] Figure 7 This is a partial perspective view of the rotary cutting tool according to embodiment 3.

[0024] Figure 8 This is a partial front view of the rotary cutting tool according to embodiment 3.

[0025] Figure 9 This is a partial perspective view of the components constituting the rotary cutting tool of Embodiment 3.

[0026] Figure 10 This is an enlarged view of the part of the main body where the blade is joined in Embodiment 3.

[0027] Figure 11 This is a side view of a traditional rotary cutting tool. Figure 11 It is a diagram of a plane that is perpendicular to the back of the seat and contains the aforementioned axis, viewed in the vertical direction.

[0028] Figure 12 It refers to the points from which the axis is perpendicular to the axis of a conventional rotary cutting tool, at positions S to X of the axis. Figure 11 The left-side view of the end face and sectional view. Distance from the front end ( Figure 11 The distances (on the left side of the paper) are as follows: S is 0mm, T is 5mm, U is 10mm, V is 15mm, W is 20mm, and X is 23mm.

[0029] Figure 13 This is a partial perspective view of the front end of the rotary cutting tool in variant form 2.

[0030] Figure 14 yes Figure 13 A magnified view of a portion of the image.

[0031] Figure 15 This is a close-up view of the front end of the rotary cutting tool in variant form 2. Detailed Implementation

[0032] The rotary cutting tool of the present invention will now be described in detail based on embodiments. The rotary cutting tool of this embodiment is a tool with a cutting edge formed on its outer periphery, capable of performing cutting operations on the outer periphery. A cutting edge can also be formed on the front end side. The rotary cutting tool of this embodiment is applicable to end mills such as end mills. The cutting edge of the rotary cutting tool of this embodiment is formed of a hard sintered body. The hard sintered body is formed of PCD and / or CBN. The size of the rotary cutting tool of this embodiment is not particularly limited. The lower limit for the diameter can be set to 10mm, 15mm, 20mm, 25mm, or 30mm, and the upper limit can be set to 50cm, 30cm, 20cm, or 10cm, etc. Furthermore, the accompanying drawings in this specification are schematic diagrams; for ease of explanation, scale bars and details have been emphasized or omitted. Also, regarding reference numerals, even for different components, the same reference numerals (axis, cutting edge, etc.) may sometimes be used to label the same functional components.

[0033] (Implementation Method 1)

[0034] like Figure 1 as well as Figure 2 As shown, the rotary cutting tool 1 in this embodiment is operated from the front end side ( Figure 1 When observing from the left, rotate counterclockwise. Figure 2 A rotary cutting tool 1 is a tool that performs cutting operations by rotating in the R direction. The rotary cutting tool 1 has a body 10 ( Figure 3 The blade 20 is fixed to the back side 111 of a seat provided in a groove 10a in the main body 10. The groove 10a is formed in a spiral shape on the outer periphery of the blade portion 11 from the front end to the rear. The blade 20 engages with the groove 10a.

[0035] Two cutting blades 20 are arranged at 180° intervals on the outer periphery of the main body 10, and engage with the back surface 111 of the seat disposed in the groove 10a via a mating surface 20a. The groove 10a also serves to discharge cutting chips generated during cutting. Figure 2 As shown, a plane perpendicular to the back surface 111 of the seat and containing the axis Ax (when viewed in the vertical direction) Figure 1 When the plane is parallel to the paper surface, the two ends of the back surface 111 of the seat with the axis Ax as the reference ( Figure 1 One of the left and right ends) Figure 1 The left end and front end are located in front of the rotation direction of the rotary cutting tool 1, closer to the axis Ax. Figure 1 The position above ( Figure 2 (S)), the other end ( Figure 1 The right end and rear end are located behind the rotation direction of the rotary cutting tool 1, closer to the axis Ax. Figure 1 (below) position ( Figure 2(Y) and (Z)). In the conventional rotary cutting tool 3, such as Figure 11 , Figure 12 Therefore, when viewing the back surface 311 of the seat in a vertical direction along a plane perpendicular to the back surface 311 and including the axis Ax, both ends (one end and the other end) of the back surface 311 of the seat, with the axis Ax as a reference, are located behind the axis Ax in the direction of rotation of the rotary cutting tool 5. Figure 11 , Figure 12 (S)).

[0036] The main body 10 is formed of common materials such as tool steel or cemented carbide. The main body 10 consists of a cutting edge 11, a transition part 12, and a shank 13, starting from the front end side in the axial direction Ax. The cutting edge 11 can be cylindrical or conical.

[0037] In the cutting edge 11, the back surface 111 of the seat is formed in the groove 10a. The back surface 111 of the seat is part of a plane that is inclined at a predetermined angle (10° in the rotary cutting tool 1) relative to the rotation axis, i.e., the axis Ax of the rotary cutting tool 1. The cutting tool 20 is joined to the back surface 111 of the seat and the bottom surface by welding or the like.

[0038] The blade 20 has a mating surface 20a that engages with the back surface 111 of the seat, and a cutting edge E is formed thereon. The blade 20 has a double-layer structure formed by joining a hard sintered body layer 21, which is made of hard sintered body and has the cutting edge E, with a hard alloy layer 22, which is made of hard alloy and is on the mating surface 20a side.

[0039] For the insert 20, after the double-layered cuboid insert blank is joined to the back surface 111 and bottom surface of the body 10, the cutting edge E can be formed by electrical discharge machining, laser machining, grinding based on a diamond wheel, etc., so that the rake angle and clearance angle are constant in any section of rotation in the axial direction. Here, the clearance angle is 8° and the rake angle is 10°, but it is not particularly limited. Compared with forming the cutting edge E first and then joining it to the back surface 111 of the body, it can be manufactured more simply. Furthermore, the method of forming the cutting edge E first is not excluded.

[0040] The back surface 111 of the seat is part of a plane, i.e., a flat surface. A blade 20 is joined to the back surface 111 of the seat. The radial length of the back surface 111 of the seat shortens near the front end and near the rear end. Specifically for machining reasons, it becomes curved after the mating surface beyond the rear end side of the back surface 111 of the seat. The blade 20 is a cuboid component, and its surface (inner surface 20b) orthogonal to the surface of the back surface 111 of the seat (matting surface 20a) and closest to the axis Ax is a surface that is approximately parallel to the axis Ax. The surface that intersects the back surface 111 of the seat of the body 10 and abuts against the inner surface 20b of the blade 20 has a shape complementary to the shape of the inner surface 20b of the blade 20 (a plane in this embodiment).

[0041] The rotary cutting tool of this embodiment can be manufactured as follows. First, the main body 10 is manufactured. The main body 10 can be manufactured by cutting the same bar stock as a whole, or it can be manufactured by forming multiple parts separately (e.g., the cutting edge 11, the transition part 12, and the shank 13) and then connecting and engaging these multiple parts. A spiral groove 10a extending from the front end to the rear end is formed on the cutting edge 11 by cutting or the like. A back surface 111 for engaging the blade 20 is also formed in the groove 10a. The formation of the back surface 111 of the seat can be performed together with the groove 10a, or it can be performed independently after the groove 10a is formed.

[0042] After forming the back surface 111 and bottom surface of the base, the insert 20 is joined to the back surface 111 and bottom surface of the base by brazing or the like. After joining the insert 20, the cutting edge E is formed by electrical discharge machining, grinding or the like, so that it has a specified flank face and a specified rake face. The cutting edge E is the ridge line where the flank face and the rake face intersect. When forming the cutting edge E, the portion of the insert 20 that protrudes outward from the outer peripheral surface of the body 10 is also removed by grinding or the like to obtain a specified diameter. In this structure, the radial length of the two ends (the front end and 34 mm) of the insert 20 is shorter than the length in the middle.

[0043] (Implementation Method 2)

[0044] like Figure 4 as well as Figure 5 As shown, the rotary cutting tool 5 of this embodiment has a body 50 and a cutting blade 60. For the body 50 ( Figure 6 Regarding the blade 60, it has the same structure except that the inclination of the spiral groove 50a (i.e., the inclination of the blade 60) is 15°, which is different from the 10° in the main body 10. The blade 60 has a double-layer structure formed by bonding the hard sintered body layer 61 and the hard alloy layer 62. Except for the slight difference in shape formed by cutting according to the shape of the groove 50a provided in the main body 50, it has the same structure as the blade 20.

[0045] like Figure 4 Therefore, when viewing a plane perpendicular to the back surface 511 of the seat and containing the axis Ax in the vertical direction, the front end of one of the two ends of the back surface 511 of the seat, with the axis Ax as a reference, is located in front of the rotation direction of the rotary cutting tool 5, which is closer to the axis Ax. Figure 5 (S)), as the back end of the other end ( Figure 5 The (W)(X)) is located behind the axis Ax in the rotational direction of the rotary cutting tool 5. In conventional rotary cutting tools 3, such as Figure 11 , Figure 12 Thus, when the back surface 311 of the seat is viewed in the vertical direction in a plane perpendicular to the back surface 311 of the seat and including the axis Ax, the front end of the back surface 311 of the seat is located behind the axis Ax in the rotation direction of the rotary cutting tool 5. Figure 11 , Figure 12 (S)).

[0046] When the inclination of the insert 60 increases, in the conventional structure of rotary cutting tools, the inclination at both ends of the insert 60 is too large to be accommodated within the groove 50a, resulting in a shorter length of the insert 60 capable of forming the cutting edge E. Alternatively, as... Figure 11 This weakens the helix angle. By employing this structure, the radial length of the insert 60 housed within the groove 50a of the body 50 ensures that the length of the insert 60 in the axial direction Ax, required to form the cutting edge E, is increased. In this structure, the radial length of the insert 60 at both ends (the tip and at 23 mm) is shorter than its length in the middle.

[0047] (Implementation Method 3)

[0048] like Figure 7 as well as Figure 8 As shown, the rotary cutting tool 7 of this embodiment is a tool that rotates along the rotation direction R, and has a main body 70 and 80, and a cutting blade 90 (91 and 92). The main body 70 and 80 are generally disk-shaped components that overlap and are integrated in the thickness direction (axial direction).

[0049] like Figure 9 As shown, in the main body 70, six blades 91 arranged on the outer periphery are configured to open outward toward the axis of rotation R (at an angle of 70° counterclockwise with respect to the axis). In the main body 80, six blades 92 arranged on the outer periphery are configured to open outward toward the axis of rotation R (at an angle of 70° clockwise with respect to the axis). Blades 91 and 92 are configured to overlap in the axis of rotation when the main bodies 70 and 80 are integrated.

[0050] Blade engagement portions 71 and 81 are formed in the main bodies 70 and 80, and flat seat back surfaces 711 and 811 are formed in the blade engagement portions 71 and 81, through which blades 91 and 92 are engaged.

[0051] Regarding the back surface 711 of the seat, when viewed in the vertical direction as a plane perpendicular to the back surface 711 of the seat and including the axis, one end 71a of the two ends 71a and 71b of the back surface 711 of the seat, with the axis direction as a reference, is located in front of the rotation direction of the rotary cutting tool 7, which is closer to the axis Ax. Figure 8 The other end 71b is located below the axis (below the axis), and is positioned behind the axis of rotation of the rotary cutting tool 7 (in the direction of rotation). Figure 8 (above)

[0052] Regarding the back surface 811 of the seat, the helix angle is opposite to that of the back surface 711 of the seat. When viewed in the vertical direction, on a plane that is perpendicular to the back surface 811 of the seat and includes the axis, with the axis direction as the reference, one end 81a of the two ends 81a and 81b of the back surface 811 of the seat is located in front of the axis in the rotation direction of the rotating cutting tool 7, and the other end 81b is located behind the axis in the rotation direction of the rotating cutting tool 7.

[0053] The cutting blades 91 and 92 are processed by electrical discharge machining, laser machining, grinding, etc., so that the rake angle and clearance angle are constant at any part of the cutting edge.

[0054] (Deformation 1)

[0055] In the embodiment, the inner surface 20b of the blade 20 near the axis Ax is flat, but preferably the portion of the inner surface 20b near the axis Ax (in... Figure 2 The middle is near V, in Figure 5 The most concave surface is formed near the center of the U. Correspondingly, the shape of the surface for engaging the blade can also be a shape complementary to the inner surface of the blade.

[0056] Therefore, the size of the blades 20 and 60 can be increased while maintaining the strength of the main bodies 10 and 50. Based on Figure 5 Explanation. In the front end ( Figure 5 (S)), part at 23mm ( Figure 5 The radial length of the blade 60 is shorter than the length of the portion at 10 mm because the size of the blade 60 (radial length) is determined such that the portion at 10 mm, where the inner surface of the blade 60 is closest to the axis Ax ( Figure 5Sufficient strength can be achieved using (U) as a reference. Therefore, although the radial length of the insert 60 is sometimes insufficient in the portions at both ends, by making the shape of the inner surface of the insert 60 a concave surface near the axis Ax (as is the shape of the bottom surface of the seat, conversely, a bulging shape near the center), the radial length of the insert 60 increases as it moves away from both ends from this concave surface. As a result, the length of the insert 60 in the axis Ax direction can be increased, thus the cutting edge E can be lengthened, and on this basis (or instead), the inclination of the cutting edge E can be further increased. Furthermore, although the back surface of the seat is basically flat, it is permissible if slight irregularities, grooves, or pits are provided around it, and it is almost flat when the irregularities are removed.

[0057] (Deformation 2)

[0058] Furthermore, the helix angle (angle of the cutting edge) of the rotary cutting tool 1 in Embodiment 1 is positive, but it can also be negative. For example, as Figures 13-15 As shown, the rotary cutting tool A1 in this modified form is operated from the front end side ( Figure 13 The rotary cutting tool A1 is a tool that performs cutting operations by rotating counterclockwise when viewed from the upper right. It has: a main body A10 with two grooves A10a spaced 180° apart on its outer circumference; and a cutting blade A20 fixed to the back of a seat A112 located between the two grooves A10a on the main body A10. The back of the seat is part of a plane, i.e., a flat surface.

[0059] The front end of the main body A10 is fixed with a bottom cutting edge A30 and a front peripheral cutting edge A40. The bottom cutting edge A30 has a cutting edge in a direction perpendicular to the axis Ax of the rotary cutting tool A1 of this modified form, and is used to machine the front end by rotating the rotary cutting tool A1 of this modified form. The front peripheral cutting edge A40 is set with a helix angle that is positive to the axis Ax of the rotary cutting tool A1 of this modified form, and is used to machine the outer peripheral direction of the front end by rotating the rotary cutting tool A1 of this modified form.

[0060] The groove A10a is formed on the outer periphery of the cutting edge A11 in a manner that extends from the front end toward the rear and has a positive helix angle. The groove A10a also serves to remove cutting chips generated during the cutting process.

[0061] The blade A20 has four blades each on the outer periphery of the body A10 with a negative helix angle, for a total of eight. For example... Figure 15As shown, when viewing a plane perpendicular to the back of the seat and containing the axis Ax in the vertical direction, one end Tf of the back of the seat, which is based on the axis Ax direction, is located behind the rotation direction of the rotary cutting tool A1, which is closer to the axis Ax. Figure 15 The other end Te is located to the left of the axis Ax, and is positioned in front of the rotation direction of the rotary cutting tool A1. Figure 15 (to the right of)

[0062] The four blades A20 disposed in each cutting edge section are evenly arranged in the direction of the axis Ax of the main body A10, and their ends are arranged at a position that overlaps with a portion of the cutting edge of another cutting edge section in the direction of the axis Ax with the adjacent blade A20.

[0063] The insert A20 has a mating surface that engages with the back of the seat and has a cutting edge E formed thereon. The insert A20 has a double-layer structure formed by joining a hard sintered body layer A21, which is made of hard sintered body and has the cutting edge E, with a hard alloy layer A22, which is made of hard alloy and is on the mating surface side.

[0064] For insert A20, after the double-layered cuboid insert blank is joined to the back and bottom surfaces of the body A10, a curved cutting edge E can be formed through electrical discharge machining, laser machining, or grinding based on a diamond wheel, so that the rake angle and clearance angle are constant at any point in the axial direction. Here, the clearance angle is 8° and the rake angle is 10°, but this is not particularly limited. It is also possible to make the clearance angle of one end of the insert (the front end side of the rotating cutting tool A1) 15° and the rake angle 5°, and gradually change it so that the clearance angle of the other end (the shank side) is 5° and the rake angle is 15°. This is simpler to manufacture than forming the cutting edge E first and then joining it to the back surface of the body. Furthermore, the method of forming the cutting edge E first is not excluded.

[0065] In this modified rotary cutting tool A1, the cutting resistance is reduced and the sharpness and accuracy of the machined surface are improved by increasing the helix angle of the insert A20. In particular, by forming the rake face of the cutting edge E with a curved surface, the rake angle of the cutting edge E can be made to an appropriate value, thus further improving the accuracy of the machined surface. Furthermore, the cutting chips are discharged in the rearward direction by forming a groove A10a with a positive helix angle, thus providing superior chip removal compared to the case where the groove is also formed with a negative helix angle.

[0066] Explanation of reference numerals in the attached figures

[0067] 1, 5, 7, A1... Rotary cutting tool; 3... Rotary cutting tool (conventional); 10, 30, 50, 70, 80, A10... Body; 10a, 50a, A10a... Groove; 11, 31, 51, A11... Cutting edge; 111, 311, 511, 711, 811... Back side of seat; A112... Seat; 12, 32, 52, A12... Transition section; 13, 33, 53, A13... Shank; A30... Bottom cutting edge; A40... Front peripheral cutting edge; 20, 40, 60, 90, 91, 92, A20... Insert; 20a... Joint surface; 20b... Inner surface; 21, 41, 61, A21... Hard sintered body layer; 22, 42, 62, A22... Carbide layer.

Claims

1. A rotary cutting tool, The rotary cutting tool comprises: an insert, consisting of a laminate of a hard sintered body layer and a hard alloy layer, wherein at least the cutting edge serving as the ridge line of the rake face and flank face is formed of a hard sintered body containing diamond and / or cubic boron nitride; and a body to which the insert is engaged. The rotary cutting tool is characterized in that... The back surface of the seat, located behind the rotating direction of the rotary cutting tool, is part of a flat surface and inclined relative to the axis of the rotary cutting tool. It engages with the surface of the carbide layer of the cutting tool. The rake face and flank face are curved surfaces. The surface of the main body that intersects the back of the seat and abuts against the inner side of the blade has a shape complementary to the shape of the inner side of the blade. Within the effective range of the cutting edge, the difference between the maximum and minimum values ​​of the helix angle, the clearance angle, and the rake angle of the rotary cutting tool, as observed from a section perpendicular to the axis, is less than 10°. When viewed vertically in a plane perpendicular to the back of the seat and containing the axis, one end of the back of the seat, with the axis direction as a reference, is located in front of the axis in the direction of rotation of the rotary cutting tool, and the other end is located behind the axis in the direction of rotation of the rotary cutting tool.

2. The rotary cutting tool according to claim 1, characterized in that, The difference between the maximum and minimum values ​​of the helix angle, the back angle, and the front angle is 0°.

3. The rotary cutting tool according to claim 1 or 2, characterized in that, The radial lengths at both ends of the blade are shorter than the length in the middle.

4. The rotary cutting tool according to any one of claims 1 to 3, characterized in that, The blade is composed of a laminate consisting of a hard sintered body layer made of hard sintered body and a hard alloy layer made of hard alloy forming a mating surface that engages with the back of the seat. At the end in front of the direction of rotation, the axial side of the rake face is the cemented carbide layer.

5. The rotary cutting tool according to claim 1, characterized in that, Within the effective range of the cutting edge, the difference between the maximum and minimum values ​​of the helix angle of the rotary cutting tool, as well as the difference between the maximum and minimum values ​​of the clearance angle and the rake angle observed from a section perpendicular to the axis, is less than 5°.

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