Cutting tool and method for manufacturing machined product

Abstract

This cutting tool comprises: a column-shaped shaft portion; a first protruding portion which protrudes from the shaft portion toward an outer circumference and includes a first cutting edge on an edge portion of the outer circumference; a second protruding portion which protrudes from the shaft portion toward the outer circumference and includes a second cutting edge on an edge portion of the outer circumference; and a first beam which is positioned spaced apart from the shaft portion, and which is connected to the first protruding portion and the second protruding portion. The second protruding portion is positioned rearward of the first protruding portion in a direction of rotation of a rotating shaft, and the first beam has a convex shape that protrudes toward the outer circumference when seen from a tip end side.

Description

[Technical Field]

[0001] The present disclosure relates to a cutting tool and a method for manufacturing a machined product. Examples of cutting tools include so-called rotary tools. Rotary tools include milling tools and boring tools. Boring tools can be used to cut the inner surface of a cylindrical workpiece. [Background technology]

[0002] Rotary tools described in Patent Documents 1 to 3 are known as cutting tools. When a rotary tool is used as a milling tool, chips are discharged to the outside by moving toward the outer periphery. On the other hand, when a rotary tool is used as a boring tool, chips are discharged to the outside by moving toward the rear end. Therefore, it is necessary to ensure both space for chip discharge and strength of the cutting portion. For example, the cutting tool described in Patent Document 3 has a rim that connects multiple pockets in which cutting inserts are attached. The rim is separated from a central hub, allowing chips to flow through the gap between the rim and the central hub. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japan Special Publication No. 2019-511385 [Patent Document 2] U.S. Patent Publication No. 2021 / 0060665 [Patent Document 3] U.S. Patent Publication No. 2014 / 0161543 Summary of the Invention

[0004] A cutting tool according to one non-limiting embodiment of the present disclosure includes a cylindrical shank extending from a front end to a rear end along a rotation axis, a first protruding portion protruding from the shank toward an outer periphery and having a first cutting edge at an end of the outer periphery, a second protruding portion protruding from the shank toward an outer periphery and having a second cutting edge at an end of the outer periphery, and a first beam positioned away from the shank and connected to the first and second protruding portions. The second protruding portion is positioned rearward of the first protruding portion in the rotation direction of the rotation axis, and when viewed from the front end side, the first beam has a convex shape protruding toward the outer periphery. [Brief explanation of the drawings]

[0005] [Figure 1] FIG. 1 is a perspective view of a cutting tool according to a non-limiting embodiment of the present disclosure, as viewed from the tip side. [Figure 2] FIG. 2 is a perspective view of the cutting tool shown in FIG. 1 as viewed from the rear end side. [Figure 3] FIG. 2 is a front view of the cutting tool shown in FIG. 1 as viewed from the tip side. [Figure 4] 2 is a rear view of the cutting tool shown in FIG. 1 as seen from the rear end side. [Figure 5] 4 is a side view of the cutting tool shown in FIG. 1 as seen from the direction of arrow Y1 shown in FIG. 3. [Figure 6] 4 is a side view of the cutting tool shown in FIG. 1 as seen from the direction of arrow Y2 shown in FIG. 3. [Figure 7] FIG. 7 is a cross-sectional view taken along the line VII-VII shown in FIG. 6. [Figure 8] FIG. 8 is a cross-sectional view taken along the line VIII-VIII in FIG. 6. [Figure 9] FIG. 7 is a cross-sectional view taken along line IX-IX in FIG. 6. [Figure 10] FIG. 6 is a cross-sectional view taken along the line XX in FIG. 5. [Figure 11] 10(a) to 10(c) are schematic cross-sectional views showing the shape of a first beam according to an embodiment, and FIG. 10(d) is a schematic cross-sectional view showing the shape of a first beam according to a reference example. [Figure 12] FIG. 4 is a schematic perspective view showing the cross-sectional shape of a first beam. [Figure 13] FIG. 2 is a schematic explanatory diagram showing one step of a method for manufacturing a machined product according to a non-limiting embodiment of the present disclosure. [Figure 14] FIG. 2 is a schematic explanatory diagram showing one step of a method for manufacturing a machined product according to a non-limiting embodiment of the present disclosure. [Figure 15] FIG. 2 is a schematic explanatory diagram showing one step of a method for manufacturing a machined product according to a non-limiting embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0006] In the cutting tool described in Patent Document 3, the frame has a linear shape when viewed from the tip side. Therefore, the gap between the frame and the central member is narrow, and improved chip discharge performance is required. Furthermore, when the cutting tool is used as a boring tool, a gap occurs between the workpiece and the frame, and there is a risk of chips getting stuck in this gap. Therefore, there is a need for a highly versatile cutting tool that can smoothly discharge chips to the outside even when used as a boring tool. The present disclosure relates to a cutting tool with excellent chip discharge performance.

[0007] Hereinafter, a cutting tool and a method for manufacturing a machined product according to an embodiment of the present disclosure will be described in detail with reference to the drawings. However, for the sake of convenience, the drawings referred to below show only the main components necessary for explaining the embodiment in a simplified form. Therefore, the cutting tool may include optional components not shown in the drawings. Furthermore, the dimensions of the components in the drawings do not faithfully represent the actual dimensions of the components, the dimensional ratios of the components, etc.

[0008] The cutting tool 10 is, for example, a rotary tool, and a specific example is a boring tool. The boring tool can be used to cut the inner surface of a cylindrical workpiece. In the following description, the side of the cutting tool 10 where the fourth cutting edge 85a is located is referred to as the leading end side, and the side opposite the leading end side is referred to as the trailing end side.

[0009] (cutting tools) FIG. 1 is a perspective view of a cutting tool 10 according to a first embodiment, as viewed from the tip side. FIG. 2 is a perspective view of the cutting tool 10 shown in FIG. 1, as viewed from the rear end side. FIG. 3 is a front view of the cutting tool 10 shown in FIG. 1, as viewed from the tip side. FIG. 4 is a rear view of the cutting tool 10 shown in FIG. 1, as viewed from the rear end side. FIG. 5 is a side view of the cutting tool 10 shown in FIG. 1, as viewed from the direction of arrow Y1 shown in FIG. 3. FIG. 6 is a side view of the cutting tool 10 shown in FIG. 1, as viewed from the direction of arrow Y2 shown in FIG. 3. FIG. 7 is a cross-sectional view taken along line VII-VII in FIG. 6. FIG. 8 is a cross-sectional view taken along line VIII-VIII in FIG. 6. FIG. 9 is a cross-sectional view taken along line IX-IX in FIG. 6. FIG. 10 is a cross-sectional view taken along line XX in FIG. 5.

[0010] A non-limiting example cutting tool 10 shown in Figures 1 to 10 may include a shaft portion 1, a first protrusion 2, a second protrusion 3, a first beam 4, a third protrusion 5, a fourth protrusion 6, a second beam 7, and a fifth protrusion 8.

[0011] Examples of materials for the shank 1, first protrusion 2, second protrusion 3, first beam 4, third protrusion 5, fourth protrusion 6, second beam 7, and fifth protrusion 8 of the cutting tool 10 include steel such as stainless steel, cast iron, and aluminum alloy. In particular, when steel is used among these members, the toughness of the above-mentioned members is high. These members may be constructed integrally or individually. When these members are constructed individually, the cutting tool 10 may be constructed by assembling these members.

[0012] <Shaft> The shank 1 may have a cylindrical shape extending along the rotation axis (center axis) L of the cutting tool 10 from the tip 1a to the rear end 1b.

[0013] There is no particular limitation on the size of the shaft portion 1. For example, the length in the direction along the rotation axis L can be set to about 150 mm to 300 mm. The diameter, which corresponds to the thickness of the shaft portion 1, can be set to about 50 mm to 120 mm.

[0014] <First protrusion> The first protrusion 2 protrudes from the shaft portion 1 toward the outer periphery. The first protrusion 2 is not limited to a configuration extending in a direction perpendicular to the rotation axis L as shown in FIGS. 1 and 3. The first protrusion 2 may extend at an angle with respect to the rotation axis L. The first protrusion 2 may have a leading end surface 21, an outer periphery surface 22, a pocket 23, a cartridge 24, a cutting insert 25, a first cutting edge 25a, and a trailing end surface 26.

[0015] The tip surface 21 may be located on the side of the tip 1a of the shaft portion 1, on the outer circumferential side of the shaft portion 1. The tip surface 21 is not limited to a configuration that is perpendicular to the rotation axis L. The tip surface 21 may be configured to be inclined with respect to the rotation axis L.

[0016] Rear end surface 26 may be located on the side of rear end 1b of shaft portion 1, on the outer circumferential side of shaft portion 1. Rear end surface 26 is not limited to a configuration that is perpendicular to rotation axis L. Rear end surface 26 may be configured to be inclined with respect to rotation axis L.

[0017] The outer peripheral surface 22 may connect the front end surface 21 and the rear end surface 26 and have a curved shape that follows the outer periphery of the shaft portion 1. The pocket 23 may be located on the front end 1a side of the outer peripheral surface 22. The pocket 23 may be formed, for example, by cutting out the outer peripheral surface 22 in the forward direction of the rotation direction T, while leaving a portion on the rear end surface 26 side. The pocket 23 may be continuous with the front end surface 21, or may extend from the front end surface 21 toward the rear end 1b. A cartridge 24 can be attached to the pocket 23.

[0018] The cartridge 24 located in the pocket 23 is not limited to a specific shape. The cartridge 24 may be in the shape of a rectangular plate. The cartridge 24 may extend from the leading end surface 21 toward the rear end 1b. The cutting insert 25 may be located on the leading end surface 21 side (the outer peripheral end) of the cartridge 24. The cutting insert 25 may be in the shape of a rod, a polygonal plate, or a polygonal column. In this embodiment, the cutting insert 25 is in the shape of a diamond-shaped plate, as shown in FIG. 5.

[0019] Examples of the material of the cutting insert 25 include cemented carbide and cermet. Examples of the cemented carbide composition include WC-Co, WC-TiC-Co, and WC-TiC-TaC-Co. Here, WC, TiC, and TaC may be hard particles, and Co may be a binder phase.

[0020] The cermet may also be a sintered composite material in which a ceramic component is combined with a metal. An example of a cermet is a titanium compound mainly composed of titanium carbide (TiC) or titanium nitride (TiN). The material of the cutting insert 25 is not limited to the above composition.

[0021] The surface of the cutting insert 25 may be coated with a coating formed using a chemical vapor deposition (CVD) method or a physical vapor deposition (PVD) method, and the coating composition may include titanium carbide (TiC), titanium nitride (TiN), titanium carbonitride (TiCN), alumina (Al2O3), and the like.

[0022] When the cutting insert 25 is in the shape of a diamond plate, the first cutting edge 25a may be located at the intersection of two side surfaces that sandwich the vertex on the tip 1a side of the cutting insert 25. Cutting can be performed by bringing this first cutting edge 25a into contact with a workpiece 103, which will be described later.

[0023] The cutting tool 10 may have two or more first protrusions 2. When the cutting tool 10 has two first protrusions 2, the two first protrusions 2 may be positioned opposite each other with respect to the rotation axis L and arranged to be point symmetric. As shown in FIGS. 1 and 3, in this embodiment, two first protrusions 2 are arranged opposite each other with respect to the rotation axis L.

[0024] <Second protrusion> The second protrusion 3 protrudes from the shaft portion 1 toward the outer periphery. The second protrusion 3 is not limited to a configuration extending in a direction perpendicular to the rotation axis L as shown in FIGS. 1 and 3. The second protrusion 3 may extend at an angle with respect to the rotation axis L. The second protrusion 3 may have a leading end surface 31, an outer periphery surface 32, a pocket 33, a cartridge 34, a cutting insert 35, a second cutting edge 35a, and a rear end surface 36.

[0025] The tip surface 31 may be located on the side of the tip 1a of the shaft portion 1, on the outer periphery of the shaft portion 1. The tip surface 31 is not limited to a configuration that is perpendicular to the rotation axis L. For example, the tip surface 31 may be configured to be inclined with respect to the rotation axis L.

[0026] The rear end surface 36 may be located on the rear end 1b side of the shaft portion 1, on the outer circumferential side of the shaft portion 1. The rear end surface 36 is not limited to being perpendicular to the rotation axis L. For example, the rear end surface 36 may be inclined with respect to the rotation axis L.

[0027] The outer peripheral surface 32 may connect the front end surface 31 and the rear end surface 36 and have a curved shape that follows the outer periphery of the shaft portion 1. The pocket 33 may be located on the front end 1a side of the outer peripheral surface 32. The pocket 23 may be formed, for example, by cutting out the outer peripheral surface 32 in the forward direction of the rotation direction T, while leaving a portion on the rear end surface 36 side. The pocket 23 may be continuous with the front end surface 31, or may extend from the front end surface 31 toward the rear end 1b. A cartridge 34 can be attached to the pocket 33.

[0028] The cartridge 34 located in the pocket 33 is not limited to a specific shape. The cartridge 34 may be in the shape of a rectangular plate. The cartridge 34 may extend from the leading end surface 31 toward the rear end 1b. The cutting insert 35 may be located on the leading end surface 31 side (the outer peripheral end) of the cartridge 34. The cutting insert 35 may be in the shape of a rod, a polygonal plate, or a polygonal column. In this embodiment, the cutting insert 35 is in the shape of a triangular plate, as shown in FIG. 5.

[0029] The material of the cutting insert 35 is the same as the material of the cutting insert 25. When the cutting insert 35 has a triangular plate shape, the second cutting edge 35a may be located at the intersection of two side surfaces that sandwich the vertex on the tip 1a side of the cutting insert 35.

[0030] The cutting tool 10 may have two or more second protrusions 3. When two second protrusions 3 are provided, the two second protrusions 3 may be positioned opposite each other with respect to the central axis and arranged in point symmetry. As shown in FIGS. 1 and 3, in this embodiment, two second protrusions 3 are arranged opposite each other with respect to the rotation axis L.

[0031] As shown in FIG. 5, the second protrusion 3 may be located rearward of the first protrusion 2 in the rotation direction T of the rotation axis L. For example, as shown in FIGS. 1 and 3, two first protrusions 2 and two second protrusions 3 are arranged. In this case, the first protrusions 2 and the second protrusions 3 that are not connected by a first beam 4 described later may be adjacent to each other in the circumferential direction of the cutting tool 10, as shown in FIGS. 1 to 3. Furthermore, the first protrusions 2 and the second protrusions 3 may be connected via a recess recessed toward the center of the shaft 1 (the rotation axis L).

[0032] <1st beam> 2 and 5, the first beam 4 is located away from the shaft 1 and is connected to the first protrusion 2 and the second protrusion 3. The second protrusion 3 is located behind the first protrusion 2 in the rotation direction T.

[0033] As shown in FIG. 3, the first beam 4 may have a convex shape that protrudes outward when viewed from the tip 1a.

[0034] 11 is a diagram showing the relationship between the shape of the first beam 4 according to the embodiment and the reference example and the cutting load applied to the first beam 4 for each shape. Specifically, the shapes of the first beam 4 according to the embodiment are shown in (a) to (c) of FIG. 11, and the shape of the first beam 4 according to the reference example is shown in (d) of FIG. 11. For ease of explanation, in FIG. 11, the first protrusion 2 and the second protrusion 3 connected by the first beam 4 are arranged so as to form a 90-degree angle when viewed from the side of the tip 1a of the shaft portion 1.

[0035] The first beam 4 may have a convex curved shape curving toward the outer periphery, as shown by reference numeral 1102 in FIG. 11 (FIG. 11(b)). In the drawing, the circumscribing circle of the cutting tool 10 when viewed from the tip 1a side, in other words, the circumscribing circle with which the cutting edge of the cutting tool 10 contacts, is indicated by S. The first beam 4 may also have an arc shape curving toward the outer periphery, as shown by reference numeral 1101 in FIG. 11 (FIG. 11(a)). The arc may have a shape that follows the arc of the circumscribing circle S when the circumscribing circle of the cutting tool 10 when viewed from the tip 1a side, in other words, the circumscribing circle S with which the cutting edge of the cutting tool 10 contacts, is set. Alternatively, the first beam 4 may have a shape of a bent straight line, as shown by reference numeral 1103 in FIG. 11 (FIG. 11(c)).

[0036] The first beam 4 has a convex shape that protrudes outward, and the part that protrudes most to the periphery is inside the circumscribed circle S. Therefore, as shown by reference numeral 1103 in Fig. 11 (Fig. 11(c)), it may have a polygonal line shape rather than a curved shape.

[0037] As shown by reference numerals 1101 to 1103 in FIG. 11 (FIGS. 11(a) to (c)), when the first beam 4 has a convex shape, the gap between the shaft 1 and the first beam 4 can be made wider compared to the case of reference numeral 1104 in FIG. 11 (FIG. 11(d)) in which the beam 14 has a straight shape. As a result, chips can flow more easily through this gap. In addition, the gap between the first beam 4 and the circumscribed circle S shown by reference numerals 1101 to 1103 is smaller than the gap between the beam 14 and the circumscribed circle S shown by reference numeral 1104, so chips are less likely to clog the gap. In addition, since more chips can flow inside the first beam 4 and the amount of chips flowing outside the first beam 4 where the machining surface is located can be reduced, the risk of damaging the machining surface can be reduced.

[0038] As shown by the thick black arrows in FIG. 11, the principal component of the cutting load generated by the first cutting edge 25a is applied rearward in the rotation direction T of the cutting tool 10. The angle formed between the extension direction of the first beam 4 and the direction of the principal component at the portion of the first beam 4 connected to the first protrusion 2, indicated by reference numerals 1101 to 1103, is smaller than the angle at the linear beam 14, indicated by reference numeral 1104. In other words, the principal component is more easily received by the first beam 4. This provides the effect of improving the durability of the cutting tool 10 in addition to improving the chip discharge performance.

[0039] In the case of the first beam 4 indicated by reference numeral 1102 in FIG. 11, the angle between the extension direction of the first beam 4 and the direction of the principal component of force at the part of the first beam 4 connected to the first protrusion 2 is smaller than in the first beam 4 bent as indicated by reference numeral 1103, so the applied cutting load can be absorbed more easily. Also, there is less risk of chips getting caught between the first beam 4 and the machined surface. In the case of the first beam 4 indicated by reference numeral 1103, the load is more likely to be applied to the bent part. As the shape changes from the broken line shape indicated by reference numeral 1103 to the convex curve shape indicated by reference numeral 1102 and the arc shape indicated by reference numeral 1101, the cutting load is more easily absorbed. Also, since the curved shape is more flexible than the broken line shape, the force of bearing the load is increased even when the first beam 4 is bent, resulting in excellent durability.

[0040] 11, the first beam 4 can more easily absorb the cutting load. There is less risk of chips getting caught between the first beam 4 and the machined surface, and the first beam 4 is less likely to come into contact with the workpiece 103 during cutting than the first beam 4 shown by reference numeral 1102.

[0041] The first beam 4 may have a leading end surface 41, an outer peripheral surface 42, and a rear end surface 43. The leading end surface 41 is located on the leading end 1a side of the shaft portion 1. The rear end surface 43 is located on the rear end 1b side of the shaft portion 1. The outer peripheral surface 32 is a surface connecting the leading end surface 31 and the rear end surface 36.

[0042] Fig. 12 is a schematic perspective view showing the cross-sectional shape of the first beam 4. In Fig. 12, dimension a is the dimension in the direction along the rotation axis L, and dimension b is the dimension in the direction perpendicular to the rotation axis L. The cross section 44 of the first beam 4 indicated by reference numeral 1201 in Fig. 12 is substantially square in which dimension a and dimension b are substantially equal.

[0043] The cross section 44 of the first beam 4, indicated by reference numeral 1202 in Fig. 12, is a substantially rectangular shape in which the dimension a is smaller than the dimension b. That is, the dimension a in the direction along the rotation axis L is smaller than the dimension b in the direction perpendicular to the rotation axis L, resulting in a flat shape. In this case, the first beam 4 is less likely to bend in the radial direction and is less likely to come into contact with the machined surface of the workpiece 103. This also has a significant effect of pushing chips toward the rear end 1b.

[0044] The cross section 44 of the first beam 4 indicated by reference numeral 1203 in Fig. 12 is a substantially rectangular shape in which the dimension a is larger than the dimension b. In other words, it is a flat shape in which the dimension a in the direction along the rotation axis L is larger than the dimension b in the direction perpendicular to the rotation axis L. In this case, the space on the inner periphery side of the first beam 4 can be made larger.

[0045] The cross section 44 of the first beam 4, indicated by reference numeral 1204 in FIG. 12, is generally trapezoidal in shape, with dimension a being larger on the outer periphery side than on the inner periphery side. Dimension a2 on the outer periphery side is larger than dimension a1 on the inner periphery side. In this case, the first beam 4 is less likely to bend in the radial direction. When chips are forced to flow rearward, they are directed toward the inner periphery side rather than the outer periphery side where the machining surface is located, making it less likely that they will come into contact with the machining surface.

[0046] 11 and 3, the distance m between the shaft portion 11 and the first beam 4 may be larger than the dimension n of the first beam 4 in the direction (radial direction) perpendicular to the rotation axis L. In this case, the distance m can be increased to easily ensure space for chip flow.

[0047] 11 and 3, when the circumscribing circle S of the cutting tool is set, the distance k between the circumscribing circle S and the first beam 4 may be narrower than the distance m between the shaft 1 and the first beam 4. In this case, the space formed between the machining surface and the first beam 4 can be reduced, making it difficult for chips to become caught between the first beam 4 and the machining surface.

[0048] The first beam 4 may approach the rear end 1b as it approaches the second protrusion 3. That is, as shown in FIG. 5, the rear end surface 43 is inclined obliquely from the front end 1a toward the rear end 1b. In this case, when the cutting tool 10 is rotated, it is easy to encourage chips to flow in a screw-like manner toward the rear end 1b. Even when coolant is used, it is easy to encourage the coolant to flow toward the rear end 1b, making it easy to discharge chips.

[0049] The first beam 4 may be spaced further away from the leading edge 1a as it approaches the second protrusion 3. That is, as shown in FIG. 5, the leading edge surface 41 is inclined obliquely from the leading edge 1a toward the rear end 1b. In this case, a space for chips generated by the second cutting edge 35a to flow can be secured. A chip pocket 45 is formed at the connection portion of the first beam 4 with the second protrusion 3, making it easier for chips generated by the second cutting edge 35a to flow through the chip pocket 45 to the rear end 1b. With this configuration, compared to a configuration in which the rear end of the first protrusion 2 and the rear end of the second protrusion 3 are connected, it is possible to more accurately withstand the principal component of force acting on the first cutting edge 25a of the first protrusion 2 and to more effectively discharge chips generated by the second cutting edge 35a.

[0050] <Third protrusion> The third protrusion 5 protrudes from the shaft portion 1 toward the outer periphery. The third protrusion 5 is not limited to a configuration extending in a direction perpendicular to the rotation axis L as shown in FIG. 1 . The third protrusion 5 may extend at an angle with respect to the rotation axis L. The third protrusion 5 may have a tip surface 51, an outer periphery surface 52, a pocket 53, a cartridge 54, a cutting insert 55, a third cutting edge 55a, and a rear end surface 56.

[0051] The tip surface 51 may be located on the side of the tip 1a of the shaft portion 1. The tip surface 51 may be perpendicular to the rotation axis L or may be inclined relative to the rotation axis L. The rear end surface 56 may be located on the side of the rear end 1b of the shaft portion 1. The rear end surface 56 may be perpendicular to the rotation axis L or may be inclined relative to the rotation axis L.

[0052] The outer peripheral surface 52 may connect the front end surface 51 and the rear end surface 56 and have a curved shape that follows the outer periphery of the shaft portion 1. The pocket 53 may be located on the front end 1a side of the outer peripheral surface 52. The pocket 53 may be formed, for example, by cutting out the outer peripheral surface 52 in the forward direction of the rotational direction T of the upper third protrusion 5 in FIGS. 1 and 2, while leaving a portion on the rear end surface 56 side. The pocket 53 may be continuous with the front end surface 31, or may extend from the front end surface 51 toward the rear end 1b. A cartridge 54 can be attached to the pocket 53.

[0053] The cartridge 54 located in the pocket 53 is not limited to a specific shape. The cartridge 54 may be in the shape of a rectangular plate. The cartridge 54 may extend from the front end surface 51 toward the rear end 1b. The cutting insert 55 may be located on the front end surface 51 side (the outer peripheral end) of the cartridge 54. The cutting insert 55 may be in the shape of a rod, a polygonal plate, or a polygonal column. In this embodiment, the cutting insert 55 is in the shape of a triangular plate, as shown in FIG. 5.

[0054] The material of the cutting insert 55 is the same as the material of the cutting insert 25. When the cutting insert 55 has a triangular plate shape, the third cutting edge 55a may be located at the intersection of two side surfaces that sandwich the vertex on the tip 1a side of the cutting insert 55.

[0055] The cutting tool 10 may have two or more third protrusions 5. When the cutting tool 10 has two third protrusions 5, the two third protrusions 5 may be positioned opposite each other with respect to the rotation axis L and arranged to be point symmetric. As shown in FIG. 2 , in this embodiment, two third protrusions 5 are arranged opposite each other with respect to the rotation axis L.

[0056] <4th protrusion> The fourth protrusion 6 protrudes from the shaft portion 1 toward the outer periphery. The fourth protrusion 6 is not limited to a configuration extending in a direction perpendicular to the rotation axis L as shown in FIG. 1 . The fourth protrusion 6 may extend at an angle relative to the rotation axis L. The fourth protrusion 6 may have a tip surface 61, an outer periphery surface 62, and a rear end surface 63.

[0057] The tip surface 61 may be located on the side of the tip 1a of the shaft portion 1. The tip surface 61 may be perpendicular to the rotation axis L or may be inclined relative to the rotation axis L. The rear end surface 63 may be located on the side of the rear end 1b of the shaft portion 1. The rear end surface 63 may be perpendicular to the rotation axis L or may be inclined relative to the rotation axis L.

[0058] The outer peripheral surface 62 may connect the front end surface 61 and the rear end surface 63 and have a curved surface shape that follows the outer periphery of the shaft portion 1 .

[0059] The cutting tool 10 may have two or more fourth protrusions 6. When the cutting tool 10 has two fourth protrusions 6, the two fourth protrusions 6 may be positioned opposite each other with respect to the central axis and arranged in point symmetry. As shown in FIG. 2 , in this embodiment, two third protrusions 5 are arranged opposite each other with respect to the rotation axis L.

[0060] The fourth protrusion 6 may be located rearward of the third protrusion 5 in the rotation direction of the rotation axis L. The third protrusion 5 and the fourth protrusion 6 may be located closer to the rear end 1b than the first protrusion 2 and the second protrusion 3. The third protrusion 5 and the fourth protrusion 6 may be adjacent to each other in the circumferential direction of the cutting tool 10 shown in FIG. 3 . Furthermore, the third protrusion 5 and the fourth protrusion 6 may be connected in the circumferential direction of the cutting tool 10.

[0061] <Second beam> The second beam 7 is located away from the shank 1 and is connected to the third protrusion 5 and the fourth protrusion 6. When viewed from the tip 1a side, the second beam 7 may have a convex shape that protrudes toward the outer periphery. When the second beam 7 has a convex shape, the gap between the shank 1 and the second beam 7 can be made wider compared to when it has a linear shape. As a result, chips can flow more easily through this gap.

[0062] The first beam 4 approaches the rear end 1b as it approaches the second protrusion 3, and the second beam 7 may extend in a direction perpendicular to the rotation axis L. The first cutting edge 25a and the second cutting edge 35a on the front end 1a side perform main cutting. The third cutting edge 55a on the rear end 1b side is used for finishing cutting, so the fourth protrusion 6 may not have a cutting edge. Therefore, there is no need to form a space (chip pocket) in the fourth protrusion 6 for chips to flow through.

[0063] <5th protrusion> The fifth protrusion 8 protrudes from the shaft 1 toward the outer periphery at the tip 1a of the shaft 1. The fifth protrusion 8 is not limited to a configuration extending in a direction perpendicular to the rotation axis L as shown in FIGS. 1 and 3. The fifth protrusion 8 may extend at an angle with respect to the rotation axis L. The fifth protrusion 8 may have a tip surface 81, an outer periphery surface 82, a pocket 83, a cartridge 84, a cutting insert 85, and a fourth cutting edge 85a.

[0064] The tip surface 81 may be located on the side of the tip 1a of the shaft portion 1. The tip surface 81 may be perpendicular to the rotation axis L or may be inclined relative to the rotation axis L.

[0065] The outer peripheral surface 82 may be located on the outer peripheral side of the fifth protrusion 8 and may be curved along the outer periphery of the shaft portion 1. The pocket 83 may be formed, for example, in the upper fifth protrusion 8 in FIGS. 1 and 2 , in the forward direction of the rotational direction T of the outer peripheral surface 82. The pocket 83 may be continuous with the front end surface 81, or may extend from the front end surface 81 toward the rear end 1 b. A cartridge 84 can be attached to the pocket 83.

[0066] The cartridge 84 located in the pocket 83 is not limited to a particular shape. The cartridge 84 may be in the shape of a rectangular plate. The cartridge 84 may extend from the front end surface 81 toward the rear end 1b. The cutting insert 85 may be located on the front end surface 81 side of the cartridge 84. The cutting insert 85 may be in the shape of a rod, a polygonal plate, or a polygonal column. In this embodiment, the cutting insert 85 is in the shape of a diamond plate, as shown in FIG. 5.

[0067] The material of the cutting insert 85 is the same as the material of the cutting insert 25. When the cutting insert 85 has a diamond-shaped plate shape, the fourth cutting edge 85a may be located at the intersection of two side surfaces that sandwich the vertex on the tip 1a side of the cutting insert 55.

[0068] The cutting tool 10 may have two or more fifth protrusions 8. When two fifth protrusions 8 are provided, the two fifth protrusions 8 may be positioned opposite each other with respect to the central axis and arranged in point symmetry. The fifth protrusion 8 may be positioned in a radially aligned line with the first protrusion 2, as shown in FIG. 3 .

[0069] <Method of manufacturing machined products> Next, a non-limiting method for manufacturing a machined product according to the present disclosure will be described with reference to the drawings. The method will be described for forming a large-diameter hole 104 in a workpiece 103 using the first cutting edge 25a, the second cutting edge 35a, and the third cutting edge 55a, and forming a small-diameter hole 105 using the fourth cutting edge 85a.

[0070] The machined product 101 is produced by cutting a workpiece 103. The manufacturing method of the machined product 101 in this embodiment includes the following steps: (1) rotating the cutting tool 10; (2) contacting the cutting tool 10 with the workpiece 103; (3) removing the cutting tool 10 from the workpiece 103; Equipped with.

[0071] More specifically, first, as shown in Fig. 13, the cutting tool 10 may be rotated around the rotation axis L and brought relatively close to the workpiece 103. Next, as shown in Fig. 14, at least a part of the cutting edge of the cutting tool 10 may be brought into contact with the workpiece 103 to cut the workpiece 103. Then, as shown in Fig. 15, the cutting tool 10 may be moved relatively away from the workpiece 103 (machined object 101).

[0072] As shown in FIG. 13, the cutting tool 10 may be moved forward, in other words, downward in FIG. 13, while being rotated, to bring the cutting tool 10 closer to the workpiece 103.

[0073] Alternatively, as shown in FIG. 14, the workpiece 103 may be cut by moving the cutting tool 10 forward with at least a part of the cutting edge in contact with the workpiece 103.

[0074] 15, the cutting tool 10 may be moved away from the workpiece 103 by moving the cutting tool 10 rearward, in other words, upward in FIG. 13, while rotating.

[0075] In each step, the cutting tool 10 is moved to bring the cutting tool 10 into contact with the workpiece 103 or to move the cutting tool 10 away from the workpiece 103, but this is not limited to this case.

[0076] For example, in step (1), the workpiece 103 may be brought closer to the cutting tool 10. In step (3), the workpiece 103 may be moved away from the cutting tool 10. When continuing the cutting process, the cutting tool 10 may be kept rotating, and the step of bringing at least a part of the cutting edge into contact with different locations on the workpiece 103 may be repeated.

[0077] Typical examples of the material of the workpiece 103 include hardened steel, carbon steel, alloy steel, stainless steel, cast iron, and non-ferrous metals.

[0078] The invention according to the present disclosure has been described above based on the drawings and embodiments. However, the invention according to the present disclosure is not limited to the above-described embodiments. In other words, the invention according to the present disclosure can be modified in various ways within the scope of the present disclosure, and embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the invention according to the present disclosure. In other words, it should be noted that a person skilled in the art could easily make various modifications or corrections based on the present disclosure. It should also be noted that these modifications or corrections are included in the scope of the present disclosure. [Explanation of symbols]

[0079] 1 Shaft 2 First protrusion 21, 31, 51, 61 Tip surface 22, 32, 52, 62 outer surface 23, 33, 53 pockets 24, 34, 54 cartridges 25, 35, 55 cutting inserts 25a 1st cutting edge 26, 36, 56, 63 Rear end surface 3 Second protrusion 35a 2nd cutting edge 4 1st beam 41 Tip surface 42 Outer surface 43 Rear end surface 5 Third protrusion 55a 3rd cutting edge 7 Second beam 10 Cutting Tools L rotation axis T rotation direction

Claims

1. a cylindrical shaft portion extending from the front end to the rear end along the rotation axis; a first protruding portion protruding from the shaft portion toward an outer periphery and attached to an end of the outer periphery, the first protruding portion including a first cutting insert having a first cutting edge; a second protruding portion protruding from the shank toward the outer periphery and attached to an end of the outer periphery, the second protruding portion including a second cutting insert having a second cutting edge; a first beam located away from the shaft portion and connected to the first protrusion and the second protrusion, the second protrusion is located rearward of the first protrusion in the rotation direction of the rotation shaft, When viewed from the tip end side, the first beam has a convex shape curved toward the outer periphery, the first beam is connected to the first protruding portion at a rear side in the rotational direction relative to the first cutting insert, and moves away from the tip as it approaches the second protruding portion.

2. The cutting tool according to claim 1 , wherein the first beam has a convex curved shape that curves toward the outer periphery when viewed from the tip side.

3. The cutting tool according to claim 2 , wherein the first beam has an arc shape curved toward the outer periphery when viewed from the tip end side.

4. 2. The cutting tool according to claim 1, wherein in a cross section including the rotation axis, the first beam has a flat shape in which a dimension along the rotation axis is smaller than a dimension in a direction perpendicular to the rotation axis.

5. The cutting tool according to claim 1 , wherein in a cross section perpendicular to the rotation axis, a distance between the shaft portion and the first beam is larger than a dimension of the first beam in a direction perpendicular to the rotation axis.

6. 2. The cutting tool according to claim 1, wherein when a circumscribing circle of the cutting tool is set as viewed from the tip side, a distance between the circumscribing circle and the first beam is narrower than a distance between the shaft portion and the first beam.

7. The cutting tool according to claim 1 , wherein the first beam approaches the rear end as it approaches the second protruding portion.

8. a third protruding portion protruding from the shaft portion toward the outer periphery and having a third cutting edge at an end of the outer periphery; a fourth protrusion protruding from the shaft portion toward the outer periphery; a second beam located away from the shaft portion and connected to the third protrusion and the fourth protrusion, the fourth protrusion is located rearward of the third protrusion in the rotation direction of the rotation shaft, the third protruding portion and the fourth protruding portion are located closer to the rear end than the first protruding portion and the second protruding portion, The cutting tool according to claim 1 , wherein the second beam has a convex shape curved toward an outer periphery when viewed from the tip side.

9. the first beam approaches the rear end as it approaches the second protruding portion, The cutting tool according to claim 8 , wherein the second beam extends in a direction perpendicular to the rotation axis.

10. a cylindrical shaft portion extending from the front end to the rear end along the rotation axis; a first protruding portion protruding from the shaft portion toward an outer periphery and having a first cutting edge at an end of the outer periphery; a second protruding portion protruding from the shaft portion toward the outer periphery and having a second cutting edge at an end of the outer periphery; a third protruding portion protruding from the shaft portion toward the outer periphery and having a third cutting edge at an end of the outer periphery; a fourth protrusion protruding from the shaft portion toward the outer periphery; a first beam positioned away from the shaft portion and connected to the first protrusion and the second protrusion; a second beam located away from the shaft portion and connected to the third protrusion and the fourth protrusion, the second protrusion is located rearward of the first protrusion in the rotation direction of the rotation shaft, the fourth protrusion is located rearward of the third protrusion in the rotation direction of the rotation shaft, the third protruding portion and the fourth protruding portion are located closer to the rear end than the first protruding portion and the second protruding portion, When viewed from the tip side, the first beam has a convex shape curved toward the outer periphery, The cutting tool, wherein the second beam has a convex shape curved toward the outer periphery.

11. A step of rotating the cutting tool according to any one of claims 1 to 10; contacting the cutting tool with a workpiece; and removing the cutting tool from the workpiece.

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