Clamp jig and cutting tool

Abstract

Provided are a clamp jig and a cutting tool that make it possible to perform a smooth cutting treatment by stably clamping a cutting insert to a tool body. This clamp jig 10 clamps a cutting insert 12 having a recess 22 and has a protrusion 52 which engages with the recess 22, wherein the protrusion 52 has a contact part 56 that comes into contact with an inner peripheral surface 23 of the recess 22 at two locations in the circumferential direction.

Description

Clamping jig and cutting tool

[0001] The present invention relates to a clamping jig and a cutting tool.

[0002] Patent Documents 1 and 2 disclose a cutting tool having a clamping structure in which a cutting insert disposed on a mounting seat of a tool body is clamped by a clamping jig by fastening a screw member to the tool body.

[0003] Japanese Patent No. 7167050 Japanese Unexamined Patent Application Publication No. 2010-522087

[0004] By the way, in the cutting tool described in Patent Document 1, when a convex portion having an annular surface of the clamping jig is fitted into a concave portion having an annular surface of the cutting insert, the respective annular surfaces do not come into surface contact but contact at a single point, and there is a possibility that the cutting insert may be displaced relative to the tool body during high-load machining.

[0005] Further, the cutting tool described in Patent Document 2 shows that a mating surface in which a plurality of radially oriented ridges and grooves are alternately provided is provided between the mounting seat and the cutting insert. According to this cutting tool, by having a V-shaped mating surface, it is possible to install different cutting edges at the cutting position by moving or rotating the cutting insert as compared with being limited to a rotation of 180-degree indexing. However, a mating surface in which a plurality of radially oriented ridges and grooves are alternately provided is particularly difficult to form from a high-hardness material such as ceramic and is liable to chipping.

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide a clamping jig and a cutting tool capable of smoothly performing cutting work by stably clamping a cutting insert to a tool body.

[0007] In order to achieve the above object, the clamping jig of the present invention is a clamping jig for clamping a cutting insert having a concave portion, and has a convex portion that engages with the concave portion, and the convex portion has a contact portion that contacts the inner peripheral surface of the concave portion at two circumferential positions.

[0008] This clamping jig has a convex portion that contacts the inner circumferential surface of the recess of the cutting insert at two points in the circumferential direction, allowing for stable clamping of the cutting insert. In particular, it can suppress displacement of the cutting insert and enable smooth cutting in high-load machining such as rough turning of heat-resistant alloys. Furthermore, it does not require the cutting insert or the mounting surface of the seat to have a complex shape in order to suppress displacement, and therefore, ceramic cutting inserts that are difficult to form into complex shapes can be used.

[0009] Furthermore, in the clamping jig of the present invention, the convex portion has an inclined surface, and the inclination angle of the inclined surface with respect to the surface perpendicular to the axis of the convex portion may be in the range of 25 to 45 degrees.

[0010] According to this clamping jig, the protrusion has an outer circumferential surface consisting of an inclined surface with an inclination angle of 25 to 45 degrees relative to the plane perpendicular to the axis. This allows the two contact points of the protrusion to smoothly contact the inner circumferential surface of the recess of the cutting insert, enabling stable clamping of the cutting insert.

[0011] Furthermore, in the clamping jig of the present invention, the convex portion may be formed in the shape of a frustoconical pyramidal structure, and a notch may be formed in a part of the circumferential direction, so that the ridges on both sides of the notch in the circumferential direction serve as contact points.

[0012] This clamping jig allows for stable clamping of a cutting insert by forming a notch in a portion of the circumferential direction of the convex portion of the frustoconical shape, and by using the ridges on both sides of the notch in the circumferential direction as contact points to bring into contact with the inner circumferential surface of the recess of the cutting insert.

[0013] Furthermore, in the clamping jig of the present invention, the tip portion has a tip inclined surface that is inclined with respect to a plane perpendicular to the axis of the convex portion, and the tip inclined surface may be 45 degrees or less.

[0014] This clamping jig allows for the smooth removal of chips generated during machining of the workpiece by the clamped cutting insert, thanks to the inclined tip surface.

[0015] Furthermore, the cutting tool of the present invention comprises a tool body having a mounting seat, a cutting insert having a recess and positioned on the mounting seat, and a clamping jig having a protrusion that engages with the recess, which is fastened to the tool body with the protrusion engaged with the recess to clamp the cutting insert, wherein the protrusion has contact portions that contact the inner circumferential surface of the recess at two locations in the circumferential direction.

[0016] This cutting tool includes a clamping jig with a convex portion that has contact points that contact the inner circumferential surface of the recess of the cutting insert at two points in the circumferential direction, allowing for stable clamping of the cutting insert. In particular, in high-load machining such as rough turning of heat-resistant alloys, displacement of the cutting insert can be suppressed, enabling smooth cutting. Furthermore, it is not necessary to make the seating surface of the cutting insert or mounting base a complex shape to suppress displacement, and therefore, ceramic cutting inserts, which are difficult to form into complex shapes, can be used.

[0017] Furthermore, in the cutting tool of the present invention, the convex portion has an inclined surface in which the angle of inclination between the axis of the convex portion and a plane perpendicular to it is in the range of 25 to 45 degrees, and the concave portion has an inclined surface in which the angle of inclination between the axis of the concave portion and a plane perpendicular to it is in the range of 25 to 45 degrees. The angle of inclination of the inclined surface of the convex portion may be greater than or equal to the angle of inclination of the inclined surface of the concave portion, and the angle of inclination of the inclined surface of the concave portion may be greater than or equal to the angle of inclination of the inclined surface of the convex portion. The difference in the angle of inclination of the respective inclined surfaces of the convex portion and the concave portion can be up to +10.0° / -6.5°. For example, if the angle of inclination of the inclined surface of the concave portion is 33.5°, the angle of inclination of the inclined surface of the convex portion can be set in the range of 27° to 43.5°.

[0018] This cutting tool allows the two contact points of the convex portion to smoothly contact the inner circumferential surface of the concave portion of the cutting insert, enabling stable clamping of the cutting insert.

[0019] Furthermore, in the cutting tool of the present invention, the convex portion of the clamping jig may be formed in a frustoconical shape, and a notch may be formed in a part of the circumferential direction, so that the ridges on both sides of the notch in the circumferential direction serve as contact portions.

[0020] This cutting tool allows for stable clamping of the cutting insert by forming a notch in a portion of the circumferential direction of the convex portion of the frustoconical shape of the clamping jig, and by using the ridges on both sides of the notch in the circumferential direction as contact points to bring into contact with the inner circumferential surface of the recess of the cutting insert.

[0021] Furthermore, in the cutting tool of the present invention, a gap may be formed between the recess and the protrusion at the tip.

[0022] This cutting tool allows for smoother removal of chips generated during machining, while minimizing chip snagging on the workpiece.

[0023] Furthermore, in the cutting tool of the present invention, the tip of the clamping jig has a tip inclined surface that is inclined with respect to a plane perpendicular to the axis of the convex portion, and the tip inclined surface may be 45 degrees or less.

[0024] This cutting tool allows for the smooth discharge of chips generated during machining along the inclined surface of the cutting tip.

[0025] According to the present invention, a clamping jig and a cutting tool are provided that enable smooth cutting by stably clamping a cutting insert to the tool body.

[0026] Figure 1 is a perspective view of a cutting tool equipped with a clamping jig according to this embodiment. Figure 2 is a perspective view of a cutting insert. Figure 3 is a longitudinal cross-sectional view of the cutting insert. Figure 4 is a perspective view of the clamping jig. Figure 5 is a side view of the clamping jig. Figure 6 is a perspective view of the clamping jig from the back side. Figure 7 is a front view of the clamping jig. Figure 8 is a plan view of the cutting insert in a state clamped by the clamping jig. Figure 9 is a schematic plan view of a cutting insert having a recess of a different shape. Figure 10 is a perspective view of the clamping jig according to Modification 1 from the back side. Figure 11 is a perspective view of the clamping jig according to Modification 2 from the back side.

[0027] Embodiments of the present invention will be described in detail below with reference to the drawings. Figure 1 is a perspective view of a cutting tool equipped with a clamping jig according to this embodiment. (Cutting tool) As shown in Figure 1, the clamping jig 10 according to this embodiment is attached to the tool body 11 and clamps the cutting insert 12. The cutting insert 12 is clamped to the tool body 11 by this clamping jig 10, thereby forming a cutting tool 100 equipped with a cutting insert 12 at its tip. The cutting tool 100 is a tool that performs cutting on a rotating workpiece using a cutting insert 12 attached to the tip of the tool body 11, and is used, for example, when performing outer diameter cutting or inner diameter cutting of a workpiece. Hereafter, the front of the tool body 11 will be referred to as the front, the rear of the tool body 11 as the rear, the upper part of the tool body 11 as the upper part, and the lower part of the tool body 11 as the lower part.

[0028] Figure 2 is a perspective view of the cutting insert. Figure 3 is a longitudinal cross-sectional view of the cutting insert.

[0029] As shown in Figures 2 and 3, the cutting insert 12 is formed in a circular shape in plan view. The cutting insert 12 is preferably made of ceramics, such as a heat-resistant alloy, which has excellent machinability. The cutting insert 12 has an upper surface 12a, a lower surface 12b, and an outer peripheral surface 12c. The upper surface 12a and the lower surface 12b are circular planes in plan view, and the outer peripheral surface 12c is provided between these upper surface 12a and lower surface 12b, extending in the circumferential direction. The lower surface 12b is a circular surface with a smaller diameter than the upper surface 12a, so that the cutting insert 12 tapers from the upper surface 12a to the lower surface 12b.

[0030] The cutting insert 12 has a cutting edge 21 along its entire circumference at the outer edge of its upper surface 12a. The cutting insert 12 also has a recess 22 on its upper surface 12a. The recess 22 is formed in a circular shape in plan view, centered on the axis CL2 of the cutting insert 12, and has an inner circumferential surface 23 and a bottom surface 24. The recess 22 is shaped to gradually narrow towards the bottom surface 24.

[0031] As shown in Figure 1, the tool body 11 has an insert mounting portion 31 at its tip, and a cutting insert 12 is mounted on this insert mounting portion 31.

[0032] The insert mounting portion 31 has a mounting seat 32. The mounting seat 32 has a seating surface 33 and a restraining surface 34. The restraining surface 34 is provided on the rear side of the seating surface 33 and is formed in a V-shape or arc shape in a plan view. The cutting insert 12 is placed in the portion of the mounting seat 32 enclosed by the seating surface 33 and the restraining surface 34. As a result, the bottom surface 12b of the cutting insert 12 abuts against the seating surface 33 and the outer peripheral surface 12c abuts against the restraining surface 34.

[0033] The insert mounting portion 31 has a clamp fixing portion 36 on the rear side of the mounting seat 32, and the clamp jig 10 is fixed and assembled to this clamp fixing portion 36 by a screw member 14. A screw hole (not shown) with an internal thread is formed in this clamp fixing portion 36, and the screw member 14 is screwed into this screw hole for fastening.

[0034] The clamp fixing portion 36 has a locking groove 37 on its rear side. The locking surface 37a of the locking groove 37 is the front side surface of the tool body 11. This locking surface 37a is an inclined surface that gradually slopes toward the rear side of the tool body 11 toward the back side of the locking groove 37.

[0035] Figure 4 is a perspective view of the clamping jig. Figure 5 is a side view of the clamping jig. Figure 6 is a perspective view of the clamping jig from the back side. Figure 7 is a front view of the clamping jig.

[0036] As shown in Figures 4 to 7, the clamp jig 10 is formed in a block shape, and a mounting hole 51 that penetrates vertically is formed in its central portion. The clamp jig 10 has a protrusion 52 that projects downward at the bottom of its front end, and a locking claw 57 that projects downward at the bottom of its rear end. The clamp jig 10 is assembled to the clamp fixing portion 36 of the insert mounting portion 31 by a screw member 14. As a result, the protrusion 52 of the clamp jig 10 engages with a recess 22 on the upper surface 12a of the cutting insert 12 placed on the mounting seat 32, and the locking claw 57 engages with the locking groove 37 of the clamp fixing portion 36. The front end side of the clamp jig 10 is a sliding surface 57a of the locking claw 57. This sliding surface 57a is an inclined surface that gradually slopes toward the rear end side of the clamp jig 10 toward the protruding side of the locking claw 57.

[0037] Furthermore, the clamping jig 10 has a tip inclined surface 58 on the upper side of its tip. This tip inclined surface 58 is an inclined surface that slopes upward toward the rear end of the clamping jig 10 and is inclined at an angle of 45 degrees or less with respect to the plane S1 perpendicular to the axis CL1 of the protrusion 52.

[0038] The protrusion 52 of the clamping jig 10 has an outer circumferential surface 53 and a bottom surface 54. This protrusion 52 is formed in a frustoconical shape that narrows downward, which is the direction of engagement with the recess 22 of the cutting insert 12. A notch 55 is formed on the rear end side of the clamping jig 10 of the protrusion 52. By forming the notch 55, contact portions 56 are provided at two locations in the circumferential direction of the protrusion 52. These contact portions 56 are provided on a pair of ridges formed at the boundary between the outer circumferential surface 53 and the notch 55 of the protrusion 52. The two circumferential contact portions 56 of the protrusion 52 then contact the inner circumferential surface 23 of the recess 22 of the cutting insert 12.

[0039] The outer circumferential surface 53 of the protrusion 52 is an inclined surface that slopes downward toward the axis CL1 of the protrusion 52 (see Figure 7). The inclination angle α of this inclined outer circumferential surface 53 with respect to the plane S1 perpendicular to the axis CL1 is in the range of 25 to 45 degrees. Preferably, this inclination angle α is in the range of 33.5 to 36.5 degrees.

[0040] Further, the concave portion 22 of the cutting insert 12 with which the convex portion 52 of the clamp jig 10 is engaged has an inclined surface on its inner peripheral surface 23 that inclines downward toward the axis CL2 of the concave portion 22 (see FIG. 3). The inclined surface, which is the inner peripheral surface 23, has an inclination angle β with respect to the perpendicular plane S2 to the axis CL2 in the range of 25 degrees to 45 degrees. Note that the inclination angle β is preferably in the range of 33.5 degrees to 36.5 degrees.

[0041] Here, the inclination angle α of the outer peripheral surface 53 of the convex portion 52 of the clamp jig 10 is set to be greater than or equal to the inclination angle β of the inner peripheral surface 23 of the concave portion 22 of the cutting insert 12 (α≧β). Conversely, the inclination angle β of the inner peripheral surface 23 of the concave portion 22 of the cutting insert 12 can be set to be greater than or equal to the inclination angle α of the outer peripheral surface 53 of the convex portion 52 of the clamp jig 10 (β≧α). Also, the difference in the inclination angles between the outer peripheral surface 53 of the convex portion 52 and the inner peripheral surface 23 of the concave portion 22 can be allowed to be up to +10.0° / −6.5°. For example, when the inclination angle β of the inner peripheral surface of the concave portion 22 is 33.5°, the inclination angle α of the outer peripheral surface 53 of the convex portion 52 can be set in the range of 27° to 43.5°.

[0042] (Fixing of the cutting insert) Next, the case of fixing the cutting insert 12 to the insert mounting portion 31 of the tool body 11 will be described. FIG. 8 is a plan view of the cutting insert clamped by the clamp jig.

[0043] The cutting insert 12 is placed on the mounting seat 32 of the tool body 11 with the concave portion 22 facing upward.

[0044] The clamp jig 10 is placed on the clamp fixing portion 36 of the insert mounting portion 31. Then, the convex portion 52 of the clamp jig 10 is engaged with the concave portion 22 on the upper surface 12a of the cutting insert 12, and the locking claw 57 is locked in the locking groove 37 of the clamp fixing portion 36.

[0045] Insert the screw member 14 into the mounting hole 51 of the clamp jig 10 and thread it into the screw hole of the tool body 11. Then, the clamp jig 10 is pressed against the tool body 11 by the fastening force obtained by fastening the screw member 14, and the sliding surface 57a of the locking claw 57 slides on the locking surface 37a of the locking groove 37, and the clamp jig 10 is pulled toward the rear side of the tool body 11.

[0046] As a result, as shown in FIG. 8, the two contact portions 56 of the convex portion 52 of the clamp jig 10 contact the inner peripheral surface 23 of the concave portion 22 of the cutting insert 12, and the cutting insert 12 is pressed downward and rearward with respect to the tool body 11 by these contact portions 56. Therefore, the bottom surface 12b of the cutting insert 12 is pressed against the seating surface 33 of the mounting seat 32, and the outer peripheral surface 12c is pressed against the restraining surface 34 of the mounting seat 32. Thus, the cutting insert 12 is firmly clamped to the mounting seat 32 of the tool body 11.

[0047] In this way, in a state where the cutting insert 12 is clamped to the tool body 11, a gap G is formed on the tip side between the concave portion 22 of the cutting insert 12 and the convex portion 52 of the clamp jig 10 (see FIGS. 1 and 8).

[0048] As described above, according to the clamp jig 10 and the cutting tool 100 according to the present embodiment, by threading the screw member 14 into the tool body 11 to clamp the cutting insert 12, the two contact portions 56 of the convex portion 52 of the clamp jig 10 contact the inner peripheral surface 23 of the concave portion 22 of the cutting insert 12. Thereby, the cutting insert 12 can be stably clamped. In particular, in high-load machining such as rough turning of a heat-resistant alloy, displacement of the cutting insert 12 can be suppressed, and smooth cutting is possible. Further, it is not necessary to make the cutting insert 12 or the seating surface 33 of the mounting seat 32 into a complicated shape in order to suppress displacement. Therefore, a ceramic cutting insert 12 that is difficult to form into a complicated shape can be used.

[0049] Furthermore, the protrusion 52 of the clamping jig 10 has an outer circumferential surface 53 which is an inclined surface with an inclination angle α in the range of 25 to 45 degrees with respect to a vertical plane S1 perpendicular to the axis CL1, and the recess 22 of the cutting insert 12 has an inner circumferential surface 23 which is an inclined surface with an inclination angle β in the range of 25 to 45 degrees with respect to a vertical plane S2 perpendicular to the axis CL2. The inclination angle α of the outer circumferential surface 53 of the protrusion 52 is set to be greater than or equal to the inclination angle β of the inner circumferential surface 23 of the recess 22. As a result, the two contact portions 56 of the protrusion 52 can smoothly contact the inner circumferential surface 23 of the recess 22 of the cutting insert 12, and the cutting insert 12 can be clamped stably.

[0050] Furthermore, the convex portion 52 of the clamping jig 10 is formed in a frustoconical shape, and a notch 55 is formed in a part of the circumferential direction, so that the edges on both sides of the notch 55 in the circumferential direction serve as contact portions 56. In other words, by forming a notch 55 in a part of the circumferential direction of the frustoconical convex portion 52, the edges on both sides of this notch 56 in the circumferential direction can be used as contact portions 56 to contact the inner circumferential surface 23 of the recess 22 of the cutting insert 12, thereby stably clamping the cutting insert 12.

[0051] Furthermore, the tip of the clamping jig 10 has a tip inclined surface 58 that is inclined with respect to a vertical plane S1 perpendicular to the axis CL1 of the protrusion 52, and the tip inclined surface 58 is set to 45 degrees or less. This allows chips generated during machining of the workpiece by the clamped cutting insert 12 to be smoothly discharged by the tip inclined surface 58.

[0052] Furthermore, in the cutting tool 100, a gap G is formed at the tip between the recess 22 of the cutting insert 12 and the protrusion 52 of the clamping jig 10, which suppresses the snagging of chips generated on the workpiece during machining and allows for smooth discharge.

[0053] In the above embodiment, an example was given of using a cutting insert 12 having cutting edges 21 around the entire circumference of the upper edge and a recess 22 on the upper surface 12a. However, the cutting insert 12 may also have cutting edges 21 around the entire circumference of the lower edge, as well as the upper edge, and a recess 22 on the bottom surface 12b. With this cutting insert 12, the upper and lower cutting edges 21 can be used around the entire circumference by reversing the front and back sides and clamping it to the tool body 11.

[0054] Furthermore, although the above embodiment illustrates a case where the recess 22 has a circular shape in plan view, the recess 22 may have a polygonal shape in plan view as long as the recess 22 and the convex portion 52 make contact at two points on the contact portion 56 of the convex portion 52. For example, as shown in Figure 9, the cutting insert 12 may have a rectangular recess 22 in plan view. Moreover, the clamping jig 10 may have a polygonal convex portion 52 in plan view. When both the inner circumferential surface of the recess 22 and the outer circumferential surface of the convex portion 52 are polygonal in plan view, it is necessary that the outer circumferential surface of the convex portion 52 presses against the inner circumferential surface of the recess 22 at two contact points 56, and that these contact points 56 are located on the rear end side of the center O of the recess 22 (the rear end side of the clamping jig 10 when the cutting insert 12 is clamped by the clamping jig 10).

[0055] Next, modified clamp jigs 10A and 10B will be described. Note that components identical to those in the clamp jig 10 according to the above embodiment are denoted by the same reference numerals and their descriptions are omitted.

[0056] (Modification 1) Figure 10 is a perspective view of the clamping jig according to Modification 1, seen from the back side. As shown in Figure 10, the clamping jig 10A according to Modification 1 has a protrusion 52A that is divided into left and right divided protrusions 62 by a groove 61 formed in the center in the width direction. Thus, the clamping jig 10A is equipped with a pair of divided protrusions 62 having a contact portion 56.

[0057] In the case of the clamping jig 10A according to this modified example 1, by clamping it to the tool body 11 with the screw member 14, the contact portions 56 of the pair of divided protrusions 62 come into contact with the inner circumferential surface 23 of the recess 22 of the cutting insert 12 positioned on the mounting seat 32, and these contact portions 56 press the cutting insert 12 downward and backward relative to the tool body 11. Therefore, the bottom surface 12b of the cutting insert 12 is pressed against the seat surface 33 of the mounting seat 32, and the outer circumferential surface 12c is pressed against the restraining surface 34 of the mounting seat 32. Thus, the cutting insert 12 is firmly clamped to the mounting seat 32 of the tool body 11.

[0058] (Modification 2) Figure 11 is a perspective view of the clamp jig according to Modification 2, taken from the back side. As shown in Figure 11, the clamp jig 10B according to Modification 2 has a convex portion 52B that is formed in a substantially trapezoidal shape in plan view. This convex portion 52B has flat side surfaces 63 on the left and right, and the ridges between these side surfaces 63 and the notch portion 55 form a contact portion 56.

[0059] In the case of the clamp jig 10B according to this modified example 2, by clamping it to the tool body 11 with the screw member 14, the contact portion 56 of the ridge between the side surface 63 of the protrusion 52 and the notch 55 contacts the inner circumferential surface 23 of the recess 22 of the cutting insert 12 positioned on the mounting seat 32, and these contact portions 56 press the cutting insert 12 downward and rearward against the tool body 11. Therefore, the bottom surface 12b of the cutting insert 12 is pressed against the seat surface 33 of the mounting seat 32, and the outer circumferential surface 12c is pressed against the restraining surface 34 of the mounting seat 32. Thus, the cutting insert 12 is firmly clamped to the mounting seat 32 of the tool body 11.

[0060] 10 Clamping jig 11 Tool body 12 Cutting insert 22 Recess 23 Inner surface 32 Mounting seat 52 Protrusion 53 Outer surface (inclined surface) 55 Notch 56 Contact area 58 Tip inclined surface 100 Cutting tool CL1 Axis CL2 Axis G Gap α Inclination angle β Inclination angle

Claims

1. A clamping jig for clamping a cutting insert having a recess, wherein the clamping jig has a protrusion that engages with the recess, and the protrusion has contact portions that contact the inner circumferential surface of the recess at two locations in the circumferential direction.

2. The clamping jig according to claim 1, wherein the protrusion has an inclined surface, and the inclination angle of the inclined surface with respect to a surface perpendicular to the axis of the protrusion is in the range of 25 to 45 degrees.

3. The clamping jig according to claim 1, wherein the convex portion is formed in the shape of a frustoconical pyramidal pyramid, and a notch is formed in a part of the circumferential direction, so that the ridges on both sides of the notch in the circumferential direction serve as the contact portion.

4. The clamping jig according to claim 1, wherein the tip portion has a tip inclined surface that is inclined with respect to a plane perpendicular to the axis of the convex portion, and the tip inclined surface is 45 degrees or less.

5. A cutting tool comprising: a tool body having a mounting seat; a cutting insert having a recess and positioned on the mounting seat; and a clamping jig having a protrusion that engages with the recess, which is fastened to the tool body with the protrusion engaged with the recess to clamp the cutting insert, wherein the protrusion has contact portions that contact the inner circumferential surface of the recess at two locations in the circumferential direction.

6. The cutting tool according to claim 5, wherein the protrusion has an inclined surface in which the angle of inclination between the axis of the protrusion and a plane perpendicular to it is in the range of 25 to 45 degrees, the recess has an inclined surface in which the angle of inclination between the axis of the recess and a plane perpendicular to it is in the range of 25 to 45 degrees, and the angle of inclination of the inclined surface of the protrusion is greater than or equal to the angle of inclination of the inclined surface of the recess.

7. The cutting tool according to claim 5, wherein the convex portion has an inclined surface in which the angle of inclination between the axis of the convex portion and a plane perpendicular to it is in the range of 25 to 45 degrees, the concave portion has an inclined surface in which the angle of inclination between the axis of the concave portion and a plane perpendicular to it is in the range of 25 to 45 degrees, and the angle of inclination of the inclined surface of the concave portion is greater than or equal to the angle of inclination of the inclined surface of the convex portion.

8. The cutting tool according to claim 5, wherein the convex portion of the clamping jig is formed in a frustoconical shape, and a notch is formed in a part of the circumferential direction, so that the ridges on both sides of the notch in the circumferential direction serve as the contact portion.

9. The cutting tool according to claim 5, wherein a gap is formed between the recess and the protrusion at the tip.

10. The cutting tool according to claim 5, wherein the tip of the clamping jig has a tip inclined surface that is inclined with respect to a plane perpendicular to the axis of the protrusion, and the tip inclined surface is 45 degrees or less.

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