Cutting tool

Abstract

The present invention provides a cutting tool. The cutting tool (10) is a cutting tool that rotates about an axis (A0), and has a cutting edge portion (14) and a projection (24). The cutting edge portion (14) has a first cutting edge (20) and a second cutting edge (22). The first cutting edge (20) is disposed in the tip direction (D) with respect to the rake face, and the second cutting edge (22) is disposed on the radially outer side (O) with respect to the rake face. The projection is formed on the rake face and has a tip (T) that truncates the chip formed by the first cutting edge. The projection has an inner forming portion (24b) and an outer forming portion (24a). Among them, the inner forming portion is located at a position radially inside (I) of a reference line (LS), and the outer forming portion is located at a position radially outside the reference line. The width of the inner forming portion is wider than the width of the outer forming portion. Accordingly, in a cutting tool having a plurality of cutting edges, a projection with improved durability can be provided.

Description

Technical Field

[0001] The present invention relates to a cutting tool for cutting a workpiece by rotation. Background Art

[0002] A cutting tool is used to cut a workpiece to fabricate various components, such as an engine. The engine has various hole shapes with and without bottoms. These hole shapes are used, for example, for the insertion of fastening bolts, the installation of oil pipes, the guiding of intake and exhaust valves, the installation of spark plugs, and the installation of fuel injection valves. To form these hole shapes, a cutting tool is used to open a hole in the workpiece, and then the opening of the hole is faced.

[0003] Here, chips generated by cutting the workpiece sometimes remain inside the workpiece (and thus inside the fabricated component). The chips remaining inside the component may hinder the operation of the component. Therefore, generally, the cut workpiece is cleaned with a solvent to remove the chips from the workpiece. However, depending on the shape of the chips, the chips may get stuck inside the workpiece. In such a case, even if the workpiece is cleaned, the chips are not easily removed from the workpiece.

[0004] To prevent chips from remaining inside the workpiece, it is preferable to limit the width, length, or shape of the chips. When the chips become wider or longer, it is difficult to remove them by cleaning. Therefore, a cutting tool having a breaker (e.g., a protrusion) for breaking or shaping the chips has been developed (see, for example, Japanese Patent Application Publication No. 10-501472).

[0005] Due to repeated cutting with the cutting tool, the breaker of the cutting tool may be damaged. That is, in order for the breaker not to become an obstacle to cutting, the breaker is made thin and small in size, so the breaker is easily damaged. In particular, when a cutting tool has multiple cutting edges for machining multiple parts, the breaker is easily damaged. This is because multiple chips formed by the multiple cutting edges abut against the breaker from mutually different directions. Examples of machining multiple parts include the formation of a facing surface and the removal of unnecessary parts (excess parts) around the facing surface. Summary of the Invention

[0006] The technical problem of the present invention is to improve the durability of the breaker in a cutting tool having multiple cutting edges. The object of the present invention is to solve the above technical problem.

[0007] A cutting tool according to an aspect of the present invention cuts a workpiece by rotating about an axis. The cutting tool has a cutting edge portion and at least one projection. The cutting edge portion has a rake face, a first cutting edge, and a second cutting edge. The first cutting edge is disposed in the tip direction of the cutting tool with respect to the rake face, and the second cutting edge is disposed radially outside with respect to the rake face with the axis as a reference. The at least one projection is formed on the rake face and has a tip that truncates the chip formed by the first cutting edge. The at least one projection has a tapered shape that narrows in width as it approaches the tip when viewed from above with the rake face as a reference. When a line passing through the tip and parallel to the axis is used as a reference line, the projection closest to the second cutting edge among the at least one projection has an inner forming portion and an outer forming portion. The inner forming portion is located at a position radially inside the reference line, and the outer forming portion is located at a position radially outside the reference line. The width of the inner forming portion is wider than the width of the outer forming portion.

[0008] According to the present invention, a projection (chip breaker) with improved durability can be provided in a cutting tool having multiple cutting edges.

[0009] Based on the following description of the embodiments with reference to the drawings, the above objects, features, and advantages should be easily understood. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a view showing a cutting tool according to an embodiment of the present invention.

[0011] Figure 2 is a view showing an example of a workpiece cut by the cutting tool.

[0012] Figure 3 is an enlarged view showing the cutting edge portion.

[0013] Figure 4 is an enlarged perspective view showing the projection.

[0014] Figure 5 is an enlarged top view showing the projection.

[0015] Figure 6A and Figure 6B is a view showing the cutting edge portion of a cutting tool according to another configuration. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0016] Hereinafter, a cutting tool according to an embodiment of the present invention will be described.

[0017] Figure 1FIG. is a view showing a cutting tool 10 according to an embodiment of the present invention. The cutting tool 10 rotates in a rotational direction C about an axis A0 while cutting a workpiece W. The tip direction D and the base end direction B of the cutting tool 10 are respectively indicated by up and down arrows in Figure 1 The direction along the axis A0 is defined as the axial direction A. The radial direction R of the cutting tool 10 is a direction orthogonal to the axis A0. The radially outer side O is the radial direction R from the axis A0 toward the outer periphery. And, the radially inner side I is the radial direction R from the outer periphery toward the axis A0.

[0018] The cutting tool 10 has one opening edge portion 12 and a plurality (here, two) of cutting edge portions 14. The opening edge portion 12 is, for example, a drill bit and makes an opening in the workpiece W. The opening edge portion 12 is disposed at the tip portion of the cutting tool 10. That is, the opening edge portion 12 is disposed in the tip direction D with respect to the plurality of cutting edge portions 14. Each of the plurality of cutting edge portions 14 has a rake face 16, a first cutting edge 20, a second cutting edge 22, and a plurality of protrusions 24. The plurality of cutting edge portions 14 cut the periphery of the hole made by the opening edge portion 12. Each of the plurality of cutting edge portions 14 uses the first cutting edge 20 and the second cutting edge 22 for this cutting. Here, the two cutting edge portions 14 are disposed on opposite sides with respect to the axis A0.

[0019] The rake face 16 is a face through which the chip passes when the cutting edge portion 14 cuts the workpiece W. Here, the rake face 16 functions as a rake face with respect to both the first cutting edge 20 and the second cutting edge 22. That is, the chip from the first cutting edge 20 and the chip from the second cutting edge 22 pass on the rake face 16.

[0020] The first cutting edge 20 is disposed in the tip direction D of the cutting tool 10 with respect to the rake face 16. The first cutting edge 20 cuts the workpiece W while rotating about the axis A0. Thereby, a plane (specifically, a circular plane) orthogonal to the axis A0 is formed on the workpiece W. The second cutting edge 22 is disposed on the radially outer side O with respect to the rake face 16. The second cutting edge 22 cuts the workpiece W while rotating about the axis A0. Thereby, a curved surface centered on the axis A0 is formed on the workpiece W.

[0021] Here, the first cutting edge 20 and the second cutting edge 22 (finally, the cutting edge portion 14) cut a range larger than the opening edge portion 12. Therefore, the distance (radius r1) from the axis A0 to the second cutting edge 22 on the radially outer side O is larger than the radius r0 of the opening edge portion 12. That is, the radius r1 of the plane and the curved surface formed by the first cutting edge 20 and the second cutting edge 22 is larger than the radius r0 of the hole made by the opening edge portion 12.

[0022] A description will be given of the workpiece W cut by the cutting tool 10. Figure 2FIG. is an example of a workpiece W cut by a cutting tool 10. The workpiece W is, for example, a workpiece W for a cylinder head of an engine. It is considered to perform a hole machining on the workpiece W by the cutting tool 10 to form a hole 42 in the workpiece W. In this case, generally, before this hole machining, unnecessary parts (extra parts) around the hole machining part are removed. Here, a part of the side wall S surrounding the hole H is an unnecessary part.

[0023] Here, the cutting tool 10 forms a hole 42, a seat surface 44, and a side wall cutting surface 46 near the side wall S. The formation of these hole 42, seat surface 44, and side wall cutting surface 46 can be performed simultaneously by the cutting tool 10 having a plurality of cutting edges (hole opening edge part 12, first cutting edge 20, and second cutting edge 22). However, when the cutting tool 10 does not cut near the side wall S, the cutting tool 10 does not form the side wall cutting surface 46.

[0024] The hole opening edge part 12 forms a hole 42 centered on the axis A0 of the cutting tool 10. The hole 42 is, for example, a hole for a valve guide bearing. A valve guide bearing is press-fitted into the hole for the valve guide bearing. The valve guide bearing guides an intake valve (or an exhaust valve) of the engine.

[0025] The first cutting edge 20 forms a seat surface 44 around the hole 42 as a plane orthogonal to the axis A0. The seat surface 44 is, for example, a valve spring seat surface. The valve spring seat surface is located at the opening end surface of the hole for the valve guide bearing (hole 42). A spring for opening and closing the valve (valve spring) is arranged on the valve spring seat surface.

[0026] The second cutting edge 22 forms a side wall cutting surface 46 as a curved surface centered on the axis A0 by cutting the side wall S surrounding the seat surface 44. The cutting tool 10 sometimes cuts the workpiece W having the side wall S and forms the seat surface 44 near the side wall S. In this case, the cutting tool 10 may interfere with the side wall S near the seat surface 44. The part Sc of the side wall S that interferes with the cutting tool 10 needs to be removed as an extra part M. If the part Sc is not removed and the workpiece W is cut, the axis A0 may also deviate from the original machining center. Therefore, in addition to forming the hole 42 by the hole opening edge part 12 and forming the seat surface 44 by the first cutting edge 20, the cutting tool 10 also removes the extra part M by the second cutting edge 22.

[0027] Figure 3 FIG. is an enlarged view showing the cutting edge part 14. A plurality of protrusions 24 having tips T are arranged on the rake face 16. The plurality of protrusions 24 are arranged along the radial direction R and the axial direction A (the direction along the axis A0). Here, three protrusions 24 form a column G (G1 to G3) along the radial direction R, and three protrusions 24 form a row K (K1 to K3) along the axial direction A.

[0028] Among the protrusions 24 in the three columns G1 to G3, the multiple protrusions 24 in the column G1 closest to the first cutting edge 20 function as a crushing portion. The tip T of the protrusion 24 cuts the chip ch1 from the first cutting edge 20 into multiple chips ch1 (see Figure 4 ). Here, the three tips T of the protrusions 24 in the column G1 cut the chip ch1 from the first cutting edge 20 into four chips arranged along the radial direction R. On the other hand, when the protrusions 24 in the column G1 are present, the protrusions 24 in the remaining columns G2 and G3 do not cut the chip ch1 from the first cutting edge 20, and as a result, they do not function as a crushing portion.

[0029] When a new first cutting edge 20 is formed due to wear or breakage of the first cutting edge 20, the protrusions 24 in the columns G2 and G3 function as a crushing portion. That is, when the first cutting edge 20 is worn, the cutting edge portion 14 is ground from the first cutting edge 20 to the line Lc1, and a new first cutting edge 20a is formed at the position of the line Lc1. As a result, the protrusions 24 in the column G2 function as a crushing portion. In addition, when the first cutting edge 20a at the position of the line Lc1 is worn, the cutting edge portion 14 is ground from the line Lc1 to the line Lc2, and a new first cutting edge 20b is formed at the position of the line Lc2. As a result, the protrusions 24 in the column G3 function as a crushing portion. Thus, the protrusions 24 in the columns G2 and G3 are pre-formed, and when forming the new first cutting edges 20a and 20b, it is not necessary to form new protrusions 24 by laser processing or the like.

[0030] Figure 4 is an enlarged perspective view showing the protrusion 24. Figure 4 shows the protrusion 24N closest to the first cutting edge 20 and the second cutting edge 22 ( Figure 3 the protrusion 24 at the lower right). Here, the multiple protrusions 24 have the same shape.

[0031] When viewed from above with the rake face 16 as a reference, the protrusion 24 has a substantially conical shape (here, a substantially triangular shape) with a width narrowing as it approaches the tip T. More specifically, the protrusion 24 has a top surface 28, a side surface 30a, a side surface 30b, and a rear surface 32. The top surface 28 is the end surface in the protruding direction protruding from the rake face 16. The side surface 30a is the side surface on the outer side O in the radial direction. The side surface 30b is the side surface on the inner side I in the radial direction. The tip T is formed at the boundary between the side surface 30a and the side surface 30b. A ridge line Lra is formed between the top surface 28 and the side surface 30a. A ridge line Lrb is formed between the top surface 28 and the side surface 30b.

[0032] When the workpiece W is cut by both the first cutting edge 20 and the second cutting edge 22, the first cutting edge 20 forms a chip ch1, and the second cutting edge 22 forms a chip ch2. In fact, the chips ch1 and ch2 may overlap with each other because of their wide widths. However, for the sake of easy judgment, only a part of the widths of the chips ch1 and ch2 in the width direction is shown here.

[0033] As described above, the protrusion 24 truncates the chip ch1 from the first cutting edge 20 by the tip T. In addition, the protrusion 24 bends the truncated chip ch1 to form a roll. On the other hand, the protrusion 24 bends the chip ch2 from the second cutting edge 22 to form a roll. Thus, the protrusion 24 not only truncates the chip ch1, but also forms rolls of the chips ch1 and ch2.

[0034] At this time, the chip ch1 applies a force Fa to the opposite surface 30a and a force Fb to the opposite surface 30b. On the other hand, the chip ch2 applies a force Fc to the opposite surface 30a. That is, the chip ch2 applies a force Fc to the opposite surface 30a and does not apply a force to the opposite surface 30b. As a result, the protrusion 24N closest to the first cutting edge 20 and the second cutting edge 22 receives the forces Fa, Fb, and Fc from the chips ch1 and ch2. Therefore, the protrusion 24N is more likely to be damaged than the other protrusions 24. As will be described below, in the present embodiment, the protrusion 24N has an asymmetric shape on the radially inner side I and the radially outer side O. Accordingly, the protrusion 24N can resist the forces Fa, Fb, and Fc, especially the force Fc. Therefore, the protrusion 24N is not easily damaged.

[0035] Figure 5 It is a plan view showing an enlarged view of the protrusion 24N. A line passing through the tip T and parallel to the axis A0 (a line along the axial direction A) is set as a reference line LS. The protrusion 24 is distinguished by the reference line LS. The portion of the protrusion 24 on the radially outer side O (on the second cutting edge 22 side with respect to the reference line LS) with respect to the reference line LS is defined as an outer formed portion 24a. The portion of the protrusion 24 on the radially inner side I (on the axis A0 side with respect to the reference line LS) with respect to the reference line LS is defined as an inner formed portion 24b. At this time, the shape of the protrusion 24N is asymmetric with respect to the reference line LS. That is, the width wdi of the inner formed portion 24b is wider than the width wdo of the outer formed portion 24a. Here, the width wdi is preferably 3 times or more the width wdo. In addition, the volume Vdi of the inner formed portion 24b is preferably 3 times or more the volume Vdo of the outer formed portion 24a. And the angle θa formed by the ridge line Lra with respect to the axis A0 (reference line LS) is preferably 5 degrees or more and 20 degrees or less. The angle θb formed by the ridge line Lrb with respect to the axis A0 (reference line LS) is preferably 30 degrees or more and 80 degrees or less.

[0036] The side surface 30a is not a uniform flat surface. In particular, the side surface 30a has a curved surface shape near the rake face 16. As a result, the ridge line Lo between the side surface 30a and the rake face 16 has a curved shape. That is, the angle formed by the ridge line Lo with respect to the reference line LS is smaller near the tip T and has a tendency to increase as it moves away from near the tip T. The side surface 30a with a curved surface shape makes it easier for the chip ch2 from the second cutting edge 22 to flow (be deflected) toward the base end direction B than the side surface 30a with a flat surface shape. Therefore, by forming the side surface 30a into a curved surface shape, the force Fc from the chip ch2 is not easily applied to the side surface 30a (i.e., the protrusion 24).

[0037] As described above, the cutting tool 10 according to the present embodiment can perform hole opening processing based on the hole opening edge portion 12, formation of the seat surface 44 based on the first cutting edge 20, and removal of the excess portion M based on the second cutting edge 22 ( Figure 1 , Figure 2 ). The protrusion 24 of the cutting tool 10 cuts off the chip ch1 from the first cutting edge 20 and forms it into a curl, and forms the chip ch2 from the second cutting edge 22 into a curl. Thereby, it is easy to remove the chip ch1 and the chip ch2 from inside the workpiece W ( Figure 4 ). The protrusion 24 has a shape that is asymmetric in the radial direction R. That is, the width wdi of the inner forming portion 24b is wider than the width wdo of the outer forming portion 24a ( Figure 5 ). As a result, the durability of the protrusion 24 is improved. That is, the protrusion 24 is not easily broken by the chip ch2 from the second cutting edge 22.

[0038] Figure 6A And Figure 6B is a view showing the cutting edge portion 14A of the cutting tool 10A related to another structure. Figure 6A Corresponding to Figure 3 , it shows the cutting edge portion 14A as viewed from a direction perpendicular to the rake face 16. Figure 6B It shows the cutting edge portion 14A as viewed from the tip direction D of the cutting tool 10A. Except for the cutting edge portion 14A, the other structures of the cutting tool 10A are the same as those of the cutting tool 10. For the cutting tool 10A, the same reference numerals are given to the same structural elements as those of the cutting tool 10, and the description thereof is omitted.

[0039] The cutting edge portion 14A of the cutting tool 10A has a plurality of protrusions 24A and a plurality of connecting portions 34 on the rake face 16. The connecting portions 34 connect the plurality of (here, three) protrusions 24A in the radial direction R. That is, the plurality of protrusions 24A within each of the plurality of columns G (G1 to G3) are connected in the radial direction R by the connecting portions 34. Thus, by connecting the plurality of protrusions 24A by the connecting portions 34, the force Fc generated based on the chip ch2 from the second cutting edge 22 is dispersed to the plurality of protrusions 24A within each column G. As a result, the plurality of protrusions 24A can easily withstand the force Fc. In this case, the plurality of protrusions 24A of the cutting tool 10A may not be a shape that is asymmetric in the radial direction R like the plurality of protrusions 24 of the cutting tool 10.

[0040] Here, a plurality of (here, three) protrusions 24A arranged along the radial direction R and connected by the connecting portions 34 form a plurality of columns G1 to G3. Accordingly, since the first cutting edge 20 is worn, when forming a new first cutting edge 20a, it is not necessary to form the protrusions 24A and the connecting portions 34 by laser processing or the like.

[0041] (Modification example)

[0042] The present invention is not limited to the above-described embodiments, and various structures can be adopted without departing from the gist of the present invention. In the cutting tool 10 (or the cutting tool 10A), the two cutting edge portions 14 (or the two cutting edge portions 14A) are arranged at positions opposite to each other with respect to the axis A0. However, the number of the cutting edge portions 14 (or the cutting edge portions 14A) can be one, or three or more. When the number of the cutting edge portions 14 (or the cutting edge portions 14A) is plural, it is preferable that the plurality of cutting edge portions 14 are arranged at intervals along an arc centered on the axis A0.

[0043] In the cutting tool 10 (or the cutting tool 10A), the number of the protrusions 24 (or the protrusions 24A) in the radial direction R and the axial direction A is three each. However, the number of the protrusions 24 (or the protrusions 24A) in the radial direction R and the axial direction A can also be one, two, or four or more respectively. In addition, the number of the protrusions 24 (or the protrusions 24A) in the radial direction R and the axial direction A can be different. In addition, the protrusions 24 (or the protrusions 24A) can be arranged only in the radial direction R, or only in the axial direction A. The protrusions 24 (or the protrusions 24A) can also be only one.

[0044] In the cutting tool 10, all of the plurality of protrusions 24 are shapes that are asymmetric in the radial direction R. In contrast, it is also possible to make only the protrusion 24N closest to the first cutting edge 20 and the second cutting edge 22 among the plurality of protrusions 24 have an asymmetric shape in the radial direction R. The necessity for the protrusion 24N to be asymmetric in the radial direction R is relatively high, but the necessity for the other protrusions 24 is not high.

[0045] In the cutting tool 10A, a part of the plurality of protrusions 24A, for example, the protrusion 24AN, may be formed in an asymmetric shape in the radial direction R as the protrusion 24 of the cutting tool 10.

[0046] [Technical solutions obtained from the embodiments]

[0047] The following describes the technical solutions that can be grasped from the above embodiments.

[0048] [1] A cutting tool (10) that cuts a workpiece (W) by rotating about an axis (A0), having a cutting edge portion (14) and at least one protrusion (24), wherein the cutting edge portion (14) has a rake face (16), a first cutting edge (20), and a second cutting edge (22), the first cutting edge (20) is disposed in the tip direction (D) of the cutting tool with respect to the rake face, the second cutting edge (22) is disposed radially outward (O) with respect to the rake face with the axis as a reference, the at least one protrusion (24) is formed on the rake face and has a tip (T) that cuts off a chip (ch1) formed by the first cutting edge, the at least one protrusion has a tapered shape that narrows in width as it approaches the tip in a plan view with the rake face as a reference, and when a line (A) passing through the tip and parallel to the axis is used as a reference line (LS), the protrusion (24N) closest to the second cutting edge among the at least one protrusion has an inner formed portion (24b) and an outer formed portion (24a), wherein the inner formed portion (24b) is located at a position radially inward (I) of the reference line, the outer formed portion (24a) is located at a position radially outward of the reference line, and the width (wdi) of the inner formed portion is wider than the width (wdo) of the outer formed portion. Accordingly, the durability of the protrusion (chip breaker) is improved.

[0049] [2] The width of the inner formed portion is 3 times or more the width of the outer formed portion. Accordingly, the durability of the protrusion (chip breaker) is further improved.

[0050] [3] The volume (Vdi) of the inner formed portion is 3 times or more the volume (Vdo) of the outer formed portion. Accordingly, the durability of the protrusion (chip breaker) is further improved.

[0051] [4] The projection having the inner forming portion and the outer forming portion has a top surface (28), a side surface (30a), and a ridge line (Lra), wherein the top surface (28) forms an end surface in the protruding direction protruding from the rake face, the side surface (30a) is located on the radially outer side, the ridge line (Lra) is located between the top surface and the side surface, and the angle (θa) formed by the ridge line with respect to the axis is 5 degrees or more and 20 degrees or less. Accordingly, the durability of the projection (fragmentation portion) is further improved.

[0052] [5] A plurality of the at least one projection are formed along the direction of the axis. When a new first cutting edge is formed due to wear of the first cutting edge, there is no need to form a new projection (fragmentation portion).

[0053] [6] A plurality of the at least one projection are formed along the radial direction (R) of the cutting tool. Accordingly, the chip can be cut into three or more pieces by the plurality of projections.

[0054] [7] A cutting tool that cuts a workpiece by rotating about an axis, the cutting tool having a cutting edge portion, a plurality of projections (24A), and a connecting portion (34), wherein the cutting edge portion has a rake face, a first cutting edge, and a second cutting edge, the first cutting edge is disposed in the tip direction of the cutting tool with respect to the rake face, the second cutting edge is disposed on the radially outer side with respect to the rake face based on the axis, the plurality of projections (24) are formed in rows along the radial direction of the cutting tool on the rake face, and have tips that cut off the chip formed by the first cutting edge, and the connecting portion (34) connects the plurality of projections. Accordingly, the plurality of projections (fragmentation portions) can cut the chip into three or more pieces and are connected by the connecting portion, thereby improving the durability of the projections.

[0055] [8] The cutting tool has a plurality of second projections (24A) and a second connecting portion (34), wherein the plurality of second projections (24A) are disposed at a position closer to the base end direction (B) of the cutting tool than the row of the projections and have tips, and are formed in rows along the radial direction on the rake face; the second connecting portion (34) connects the plurality of second projections. Accordingly, when a new first cutting edge is formed due to wear of the first cutting edge, there is no need to form a new projection (fragmentation portion).

[0056] [9] The first cutting edge cuts the workpiece to form a plane (seat surface 44) orthogonal to the axis, and the second cutting edge cuts the workpiece to form a curved surface (side wall cutting surface 46) centered on the axis. Accordingly, the formation of the seat surface and the removal of the excess portion around the seat surface can be performed.

[0057]

[10] The cutting tool has a plurality of the cutting edge portions arranged along an arc centered on the axis. Accordingly, efficient cutting can be performed using the plurality of cutting edge portions.

[0058]

[11] A cutting tool having a punching edge portion (12) disposed at a position closer to the tip direction than the cutting edge portion and having a radius (r0) smaller than the distance (r1) from the axis to the second cutting edge. Accordingly, a hole can be formed in the workpiece by the punching edge portion, and at the same time, a seat surface can be formed on the end surface of the hole and the excess portion around the seat surface can be removed.

[0059]

[12] The workpiece is a workpiece for an engine cylinder head. The punching edge portion forms a valve guide bearing hole (42) in the workpiece, and a valve guide of an intake valve or an exhaust valve is press-fitted into the valve guide bearing hole. The first cutting edge forms a valve spring seat surface (44) on the opening end surface of the valve guide bearing hole, and the second cutting edge cuts the side wall (S) on the workpiece. Accordingly, a valve guide bearing hole and a valve spring seat surface can be formed on the engine cylinder head, and the side wall (excess portion) can be cut.

Claims

1. A cutting tool (10) that cuts a workpiece (W) by rotating about an axis (A0), characterized in that it has a cutting edge portion (14) and at least one projection (24), wherein the cutting edge portion (14) has a rake face (16), a first cutting edge (20), and a second cutting edge (22). The first cutting edge (20) is disposed in the tip direction (D) of the cutting tool with respect to the rake face, and the second cutting edge (22) is disposed radially outward (O) with respect to the rake face with the axis as a reference; the at least one projection (24) is formed on the rake face and has a tip (T) that truncates a chip (ch1) formed by the first cutting edge; the at least one projection has a conical shape whose width narrows as it approaches the tip when viewed from above with the rake face as a reference; When a line (A) passing through the tip and parallel to the axis is used as a reference line (LS), the projection (24N) of the at least one projection closest to the second cutting edge has an inner forming portion (24b) and an outer forming portion (24a). The inner forming portion is located at a position radially inward (I) of the reference line, and the outer forming portion is located at a position radially outward (O) of the reference line. The width (wdi) of the inner forming portion is wider than the width (wdo) of the outer forming portion. The ridge line between the side surface (30a) of the projection and the rake face has a curved shape. The angle formed by the ridge line with respect to the reference line has a tendency to increase as it moves away from the tip.

2. The cutting tool according to claim 1, characterized in that the width of the inner forming portion is 3 times or more the width of the outer forming portion.

3. The cutting tool according to claim 1, characterized in that the volume (Vdi) of the inner forming portion is 3 times or more the volume (Vdo) of the outer forming portion.

4. The cutting tool according to claim 1, characterized in that the projection having the inner forming portion and the outer forming portion has a top surface (28), the side surface (30a), and a ridge line (Lra). The top surface forms an end surface in the protruding direction protruding from the rake face; the side surface is located radially outward; the ridge line is located between the top surface and the side surface on the radially outer side. The angle (θa) formed by the ridge line between the top surface and the side surface on the radially outer side with respect to the axis is 5 degrees or more and 20 degrees or less.

5. The cutting tool according to claim 1, characterized in that a plurality of the at least one projection are formed along the direction of the axis.

6. The cutting tool according to claim 1, characterized in that a plurality of the at least one projection are formed along the radial direction (R) of the cutting tool.

7. The cutting tool according to claim 1, characterized in that it has a plurality of the cutting edge portions, and the plurality of cutting edge portions are arranged along an arc centered on the axis.

8. The cutting tool according to any one of claims 1 to 7, characterized in that it has an opening edge portion (12) which is arranged at a position closer to the tip direction than the cutting edge portion and has a radius (r0) smaller than the distance (r1) from the axis to the second cutting edge.

9. A cutting tool for cutting a workpiece by rotating about an axis, characterized in that it has a cutting edge portion, a plurality of protrusions (24A), and a connecting portion (34), wherein the cutting edge portion has a rake face, a first cutting edge, and a second cutting edge, the first cutting edge is arranged with respect to the rake face in the tip direction of the cutting tool; the second cutting edge is arranged with respect to the rake face on the radially outer side with reference to the axis, the plurality of protrusions are formed in a row along the radial direction of the cutting tool on the rake face, and have tips for truncating the chips formed by the first cutting edge, the connecting portion connects the plurality of protrusions.

10. The cutting tool according to claim 9, characterized in that it has a plurality of second protrusions (24A) and a second connecting portion (34), wherein the plurality of second protrusions are arranged at a position closer to the base end direction (B) of the cutting tool than the row of the protrusions and have tips, and are formed in a row along the radial direction on the rake face; the second connecting portion connects the plurality of second protrusions.

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