Cutting tool and method for manufacturing cylindrical article

Abstract

To provide a cutting tool that can efficiently process a cylindrical component from a work-piece and to provide a method for manufacturing a cylindrical article using the cutting tool.SOLUTION: A cutting tool comprises a first cutting blade 11 and a second cutting blade 21. The first cutting blade 11 has a cylindrical first rotating part 12, and the second cutting blade 21 has a cylindrical second rotating part 22. The first rotating part 12 and the second rotating part 22 comprise cutting chips 15 and 25 at tip parts 13 and 23 thereof. The first rotating part 12 and the second rotating part 22 are arranged concentrically with respect to a rotary shaft. An inner diameter 18 of the first rotating part is larger than an outer diameter 28 of the second rotating part.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a cutting tool and a method for manufacturing a cylindrical article using the cutting tool. [Background technology]

[0002] Graphite crucibles are commonly used in the melting and smelting of non-ferrous metals and their alloys. Graphite also has the effect of purifying the molten metal by removing oxygen from the metal as carbon monoxide when it comes into contact with the metal.

[0003] Graphite crucibles have excellent heat resistance and high thermal conductivity, which contributes to shortening melting times and saving energy. Graphite crucibles also have high thermal conductivity and low thermal expansion, and are characterized by excellent thermal shock resistance, oxidation resistance, and corrosion resistance against molten metals.

[0004] Graphite crucibles are generally manufactured by sintering or machining. In the sintering method, graphite powder and silica are kneaded with a binder and then molded into a desired shape. This molded product is then compacted to a high density under high hydrostatic pressure to produce a molded product. The molded product is then sintered to produce a graphite crucible.

[0005] On the other hand, the manufacturing method using machining uses a block of high-density sintered artificial graphite, which is machined to form a desired cylindrical shape. For example, a typical manufacturing method involves processing the block through the following steps (a) to (e): (a) if the workpiece (artificial graphite block) is rectangular, the corners of the workpiece are cut off in advance using a cutting machine to form a block with an octagonal cross section so that it can be securely gripped in a lathe chuck. Next, using a lathe, the following steps are sequentially performed: (b) rough finishing (rough machining) of the outer diameter to form the desired circular cross section; (c) rough finishing (rough machining) of the inner diameter to form the desired inner surface; (d) finishing (finishing) of the desired inner and outer diameters; and (e) finishing (finishing) of both the upper and lower end surfaces.

[0006] BACKGROUND ART Conventionally, as a method for manufacturing a cylindrical article by cutting a workpiece, processing means using a hole saw applied to drilling work as shown in Patent Documents 1 to 3, for example, are known.

[0007] Patent document 1 describes a hole saw that has a cylindrical cutting tool consisting of a cylindrical body with a cutting edge made up of multiple teeth at the tip, a hole saw attachment part for attaching the rear end of the cylindrical cutting tool, and a shank part that is integral with the hole saw attachment part, and that has a protrusion that is lower than the tooth tips to prevent chipping of the tooth tips and improve cutting performance.

[0008] Patent Document 2 describes a hole saw having a cylindrical core body and a plurality of cutting tips made of a hard material joined to the peripheral opening of the lower part of the core body, in which the inner surface of the cutting tips has an inner flank that faces outward from the inner circumference of the rotational trajectory of the cutting tips, thereby shortening the cutting processing time.

[0009] Patent Document 3 describes a hole saw having a divided sintered diamond tip at the tip (opening) of the hole saw and a thicker sintered diamond tip on the inside.

[0010] The hole saws described above are primarily intended for drilling holes and machining cylindrical products. Trepanning, a process in which a hole is cut out while leaving the core (core) inside, is also known. For example, Patent Document 4 describes a trepanning tool that includes a cylindrical tube and a blade attached to the tip of the tube, and that is configured to supply cutting oil CF to the blade through oil passages R1 and R2. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-290112 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-254130 [Patent Document 3] Japanese Patent Application Publication No. 2023-99892 [Patent Document 4] Japanese Patent Application Laid-Open No. 2013-107150 Summary of the Invention [Problem to be solved by the invention]

[0012] The hole saws described in Patent Documents 1 to 3 and the trepanning tool described in Patent Document 4 can be used to cut a workpiece to produce a cylindrical product. However, in this case, it is necessary to first machine either the outer or inner surface of the cylindrical product before machining the other surface. As described above, the rough finishing process (rough machining) involves separate processes for outer diameter machining and inner diameter machining, which requires a long processing time. Furthermore, it is time-consuming to fix the workpiece to the machining device for each separate process. Furthermore, when pre-machining is required to create a polygonal shape from the workpiece, or when a large amount of workpiece is removed by cutting, the yield of the material decreases. Furthermore, as the diameter of the crucible increases, handling the workpiece becomes difficult when using a lathe, which cuts the workpiece while rotating it.

[0013] Therefore, conventional cutting methods for manufacturing cylindrical articles have had problems such as a decrease in material yield, an increase in the amount of work, and a decrease in productivity due to the need to perform outer diameter machining and inner diameter machining in separate processes. Furthermore, the cutting tools used have had problems such as the durability of cutting tips and the need to provide a machining method suitable for increasing the diameter of cylindrical parts.

[0014] Therefore, an object of the present invention is to provide a cutting tool that can efficiently machine a cylindrical article from a workpiece, and to provide a method for manufacturing a cylindrical article using the cutting tool. [Means for solving the problem]

[0015] As a result of investigations conducted in light of the above-mentioned problems, the inventors discovered that cylindrical articles can be efficiently manufactured by rotating two cutting blades, and thus completed the present invention. Specifically, the present invention encompasses the following aspects (1) to (6). In this specification, the expression "to" includes the numerical values ​​at both ends. In other words, "X to Y" is synonymous with "X or more and Y or less."

[0016] (1) A cutting tool comprising a first cutting blade and a second cutting blade, wherein the first cutting blade has a cylindrical first rotating part, and the second cutting blade has a cylindrical second rotating part, the first rotating part and the second rotating part have cutting tips at their tip ends, the first rotating part and the second rotating part are arranged concentrically with respect to a rotation axis, and the inner diameter of the first rotating part is larger than the outer diameter of the second rotating part.

[0017] (2) The cutting tool according to (1) above, wherein two or more of the cutting tips are spaced apart.

[0018] (3) The cutting tool according to (1) above, wherein the first cutting blade rotating portion and the second cutting blade rotating portion have a notch portion near the cutting tip.

[0019] (4) The cutting tool according to (1) above, wherein the cutting tip is a circular tip.

[0020] (5) The cutting tool according to (1) above, wherein the first rotating part and the second rotating part are made of a high-strength aluminum alloy.

[0021] (6) A method for manufacturing a cylindrical article, comprising using the cutting tool described in any one of (1) to (5) above to cut a workpiece between the first cutting blade and the second cutting blade to manufacture a cylindrical article. [Effects of the Invention]

[0022] According to the present invention, it is possible to provide a cutting tool that can efficiently machine a cylindrical part from a workpiece, and further to provide a method for efficiently manufacturing a cylindrical article using the cutting tool. [Brief explanation of the drawings]

[0023] [Figure 1] 1A and 1B are diagrams showing a cutting tool according to an embodiment of the present invention, in which FIG. 1A is a perspective view seen from above, and FIG. 1B is a perspective view seen from below. [Figure 2] 1A and 1B are diagrams showing a cutting tool according to this embodiment, in which (a) is a diagram showing a longitudinal section of a first cutting blade, (b) is a diagram showing a longitudinal section of a second cutting blade, (c) is a diagram showing a cross section of the first cutting blade, and (d) is a diagram showing a cross section of the second cutting blade. [Figure 3] FIG. 2 is a diagram showing a cutting tool according to the present embodiment with a cutting tip attached thereto; [Figure 4] 1 is a diagram showing the appearance of a cutting tool according to an embodiment of the present invention attached to a radial arm of a radial drilling machine. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0024] Hereinafter, embodiments of the present invention will be described in detail. The present invention is not limited to the following embodiments, and can be practiced with appropriate modifications within the scope of the object of the present invention.

[0025] (cutting tools) The cutting tool of this embodiment includes a first cutting blade and a second cutting blade, the first cutting blade having a cylindrical first rotating part, the second cutting blade having a cylindrical second rotating part, the first rotating part and the second rotating part having cutting tips at their tip ends, the first rotating part and the second rotating part being arranged concentrically with respect to a rotation axis, and the inner diameter of the first rotating part being larger than the outer diameter of the second rotating part.

[0026] Schematic diagrams of the cutting tool according to this embodiment are shown in FIGS. 1(a) and 1(b). As shown in these figures, the cutting tool has a dual cutting blade structure in which a first cutting blade 11 and a second cutting blade 21 are assembled together. The first cutting blade 11 has an outer cylindrical portion 12, which is a cylindrical first rotating portion, and the second cutting blade 21 has an inner cylindrical portion 22, which is a cylindrical second rotating portion. In this specification, the "first cutting blade" and the "second cutting blade" may be referred to simply as "cutting blades." The "first rotating portion" and the "second rotating portion" may be referred to simply as "rotating portion."

[0027] The outer cylinder 12 and the inner cylinder 22 are cylindrical members having a given thickness and also constitute the bodies of the first and second cutting blades 11, 21. The outer cylinder 12 and the inner cylinder 22 of the cutting blades 11, 21 are arranged concentrically with respect to the rotation axis of a rotary cutting device (e.g., a radial drilling machine) to which the cutting tools are attached. The inner diameter 18 of the outer cylinder 12 is configured to be larger than the outer diameter 28 of the inner cylinder 22 so that the outer cylinder 12 is arranged outside the inner cylinder 22. The inner diameter refers to the diameter of the inner surface when the cylindrical rotating part is viewed in cross section. The outer diameter refers to the diameter of the outer surface when the rotating part is viewed in cross section.

[0028] A cutting tip 15 is attached to the tip 13 of the outer cylindrical portion 12. A notch 14 is provided near the cutting tip 15 to facilitate the discharge of cutting powder generated during cutting. Similarly, a cutting tip 25 is attached to the tip 23 of the inner cylindrical portion 22, and a notch 24 is provided near the cutting tip 25.

[0029] According to the cutting tool of this embodiment, the cutting tip 15 of the outer cylindrical portion 12 and the cutting tip 25 of the inner cylindrical portion 22 can cut a workpiece to cut out a cylindrical article. The outer cylindrical portion 12 cuts out the outer surface of the cylindrical article, and the inner cylindrical portion 22 cuts out the inner surface of the cylindrical article. In this manner, the workpiece is cut between the first cutting blade 11 and the second cutting blade 21 to produce a cylindrical article. Therefore, when roughly cutting a workpiece using the cutting tool of this embodiment, a cylindrical article can be produced in essentially a single processing step. Furthermore, the dimensions of the components of the cutting tool (such as the inner diameter of the outer cylindrical portion and the outer diameter of the inner cylindrical portion) can be appropriately set depending on the type and dimensions of the cylindrical article to be produced and the type, shape, and dimensions of the workpiece.

[0030] 2(a) and 2(b) are schematic longitudinal cross-sectional views of the cutting tool according to this embodiment, and FIG. 2(c) and 2(d) are schematic cross-sectional views of the cutting tool as viewed from below. As shown in FIGS. 2(a) and 2(b), the cutting tool 1 is configured by combining an outer cylindrical portion 12 of a first cutting blade 11 and an inner cylindrical portion 22 of a second cutting blade 21. That is, after the inner cylindrical portion 22 is inserted into the outer cylindrical portion 12, the inward flange 16 provided on the upper portion of the outer cylindrical portion 12 and the outward flange 26 provided on the upper portion of the inner cylindrical portion 22 are overlapped and integrated to obtain a cutting tool consisting of the dual-structure cutting blades 11 and 21. When this cutting tool is mounted on a rotary cutting device for use, a rotating disk having a rotating shaft is mounted on the upper side of the cutting tool, as described below. As shown in FIGS. 2(c) and 2(d), the rotary disk and the cutting tool are engaged and fixed using through bolts at six locations on the outward flange 26 and the inward flange 16.

[0031] (Cutting tip placement) In the cutting tool according to this embodiment, it is preferable that two or more cutting tips are arranged at intervals from each other. By arranging multiple cutting tips, the cutting resistance of each cutting tip is reduced, which contributes to improving work efficiency.

[0032] (c) and (d) of Figure 2 show typical examples of mounting positions of cutting tips in the cutting tool according to this embodiment. A pair of cutting tips is mounted diagonally to ensure that the cutting force of each cutting tip is approximately equal. Hereinafter, this pair of cutting tips will be referred to as "one unit," and two one units will be referred to as "two units." When two or more cutting tips are mounted, the spacing between adjacent cutting tips is not limited. The central angles of each unit can be set at equal or uneven intervals. It is preferable to arrange the cutting tips so that they are approximately evenly spaced. This arrangement ensures that the pressure applied by the cutting tips to the workpiece is approximately equal, stabilizing the cutting resistance of each cutting tip, reducing vibration during cutting and contributing to improved machining accuracy.

[0033] 2(a) and 2(c) show an example in which the first cutting blade 11 has two units of cutting tips, i.e., four cutting tips spaced at 90° angles. FIGS. 2(b) and 2(d) show an example in which the second cutting blade 21 has one unit of cutting tips, i.e., two cutting tips spaced at 180° angles. Furthermore, when cutting large cylindrical objects, four units of cutting tips, i.e., eight cutting tips spaced at 45° angles, may be used. The outer and inner cylindrical portions 12 and 22 shown in FIGS. 2(c) and 2(d) rotate counterclockwise in this figure. The cutting tips are arranged so that their rotational direction corresponds to the cutting direction 33, as described below.

[0034] (Installing cutting tips) The cutting tip is attached to the tip of the first rotating part and the second rotating part of the cutting blade. The cutting tip may be attached along the lower end of the tip. The cutting tip may also be attached to the end face of the tip at a position perpendicular to the cutting direction.

[0035] FIG. 3 shows an example in which cutting tips 15 are attached to the tip 13 of the rotating part (external cylindrical part 12) in a position perpendicular to the cutting direction 33. This corresponds to a vertical cross section of the enclosed area 35 indicated by the dotted line in FIG. 1(a). The right side of FIG. 3 shows the enclosed area 35 as viewed from the front, and the left side shows the same as viewed from the cutting direction 33. This example uses round tips as cutting tips. As will be described later, the cutting tool is placed on a workpiece to perform cutting, so a workpiece (not shown) is placed below the external cylindrical part 12 in FIG. 3. Multiple round tips are attached to the tip of the rotating part in a position perpendicular to the cutting direction. The attachment configuration of the cutting tips for the first cutting blade shown in FIG. 3 can also be applied to the second cutting blade, and the following description of the second cutting blade will be omitted.

[0036] During cutting using a cutting tool, the outer tubular portion 12 of the first cutting blade 11 rotates. As the cutting blade 11 rotates, the cutting tip 15 attached to the outer tubular portion 12 moves along the circumferential shape of the outer tubular portion 12, cutting the surface of the workpiece and forming a groove-like cut in the surface of the workpiece. Therefore, the cutting direction 33 shown in FIG. 3 is also the rotation direction. As the cutting process progresses, the cut becomes deeper, so the outer tubular portion 12 of the cutting blade moves downward in a downward direction 34 as shown in FIG. 3.

[0037] As shown in FIG. 3 , the tip 13 of the outer tubular portion 12 has end faces corresponding to the thickness of the outer tubular portion 12 on the side facing the notch 14 and the side facing the workpiece. The cutting tip 15 is fixed to the end face 19 of the tip 13 of the outer tubular portion 12, on the side facing the notch 14. In this case, the cutting tip 15 is fixed by any mounting means near the lower end of the end face 19 so that a portion of the cutting edge protrudes outward beyond the lower end 20 of the tip 13 in the cutting direction 33. As a mounting means, for example, a screw 32 shown in FIG. 3 is preferably embedded in the outer tubular portion 12 for mounting. This mounting configuration reliably fixes the cutting tip to the rotating part, which is effective in terms of durability of the cutting tip and reduction of vibration of the cutting tool.

[0038] It is also preferable to select cutting tips 15 whose diameter is larger than the thickness of the cutting blade. As shown in Figure 3, by attaching the cutting tips 15 near the center of the end face 19, the cutting edges of the cutting tips 15 may protrude by approximately the same length outside the end face 19 as viewed from the cutting direction 33. This type of attachment is effective in moving cutting chips generated during machining behind the cutting blade, making it easier to discharge the cutting chips.

[0039] (Cutting tip type) The type of cutting tip attached to the cutting tool according to this embodiment is not limited. A cutting tip refers to a component equipped with a cutting blade. A cutting tip that can be removed and replaced is also called a throw-away tip. Cutting tips can be round, polygonal, or other shapes, and blades are provided according to the shape. For example, it is preferable to use a circular tip (round tip). Note that the term "round tip" used in this specification refers to the same type of cutting tip as the "circular tip."

[0040] Considering compatibility with various cutting tools, circular tips (round tips) have more flexibility in the circumferential direction than non-circular tips, making them easier to attach to cutting blades. Furthermore, circular tips allow the entire circumference of the tip to be used as an effective cutting blade, so by rotating the tip depending on its wear condition, it is possible to use the entire circumference, which is economical and desirable. The dimensions of the circular tip can be selected appropriately depending on the thickness of the cutting blade.

[0041] The cutting tip material is selected depending on the type of workpiece, and may be made of diamond-coated, cemented carbide, cermet, etc. When cutting a sintered material such as graphite, it is preferable to use a diamond-coated round cemented carbide tip.

[0042] (Notch of cutting tool) The cutting tool according to this embodiment preferably has notches in the first and second rotating parts near the cutting tips. The notches refer to recesses of any length and depth at the lower ends of the rotating parts facing the workpiece. The provision of such notches is useful in preventing clogging with cutting powder and in quickly discharging cutting powder. The notches are also preferable in that they provide space for attaching cutting tips to the tips of the rotating parts.

[0043] The notches may be recessed at the lower end of the rotating part, and their shape and arrangement are not particularly limited. For example, FIG. 2(c) shows an example in which notches 14 are provided at four locations at 90° intervals on the arc portion of the lower end of the outer cylindrical part 12, corresponding to an angular range 17 of a central angle of ±20°. FIG. 2(d) shows an example in which notches 24 are provided at two locations at 180° intervals on the arc portion of the lower end of the inner cylindrical part 22, corresponding to an angular range 27 of a central angle of ±20°. The arrangement, number, spacing, and central angle of the notches are not limited to the above example and can be selected appropriately depending on the mounting configuration of the cutting tip. For example, eight notches may be provided at 45° intervals. The spacing may be equal or unequal. The angular range of the central angle may be ±10° or ±30°.

[0044] (Rotary cutting device) Figure 4 shows a configuration in which the cutting tool according to this embodiment is mounted on a rotary cutting device. A radial drilling machine can be used as the rotary cutting device. As shown in Figure 4, the cutting tool 1 is mounted in a suspended state on a rotary shaft 7 attached to a radial arm 3 of the radial drilling machine 2. A workpiece 10 fixed on a base 5 can be cut by the cutting tool 1.

[0045] Conventional drilling methods for manufacturing cylindrical articles require cutting out the hole. In contrast, the cutting tool according to the present embodiment simultaneously processes the outer and inner diameters of the cylindrical article, requiring less power than conventional drilling. By providing the rigidity necessary to support the cutting tip in the outer and inner cylindrical portions of the cutting tool, even large-diameter cylindrical articles can be processed.

[0046] Furthermore, when machining the inner diameter of a cylindrical object, cutting can be performed so that only the cylindrical portion is extracted, so the central region of the workpiece is not turned into powder as cutting chips, as in conventional machining methods. Therefore, the central region of the workpiece remains even after cutting and can be used for other purposes, which is useful in increasing the yield of the material.

[0047] Furthermore, in the rotary cutting device, a jig such as an air swivel may be attached to the rotary shaft, and a means for blowing air into the cutting tool through the jig may be provided. This air blowing means can quickly discharge cutting dust, allowing cutting work to proceed stably.

[0048] (Cutting tool material) The material constituting the cutting tool according to this embodiment is not particularly limited. Any material having a sufficient rigidity for the rotating part can be used as a cutting blade. Furthermore, when the weight of the cutting tool increases as the diameter of the workpiece increases, it is preferable to use a lightweight material for the rotating part of the cutting blade, for example, a low-density Ti alloy or Al alloy, in consideration of workability and safety. In consideration of cost, availability, etc., a 5000-series high-strength aluminum alloy is preferred. To accommodate larger diameters, a 6000-series or 7000-series high-strength aluminum alloy is preferred.

[0049] In addition, the cutting blade according to this embodiment is preferably made of a metal plate having the following characteristics: (i) sufficient mechanical strength and rigidity to withstand the cutting resistance of the cutting tip; (ii) a lightweight metal cutting blade to reduce the load on the radial arm of the radial cutting machine; and (iii) high thermal conductivity to suppress the accumulation of frictional heat due to cutting. Metallic materials suitable for the above characteristics include high-strength aluminum alloys such as A5052, titanium alloys, and alloy steels. High-strength aluminum alloys are particularly preferred because they enable larger diameters and faster cutting of workpieces, and improve the thermal conductivity of the cutting blade, facilitating the dissipation of frictional heat.

[0050] (Work material) The cutting tool according to the present embodiment can be applied to any workpiece material. It can be applied to workpieces made of various materials, such as ceramic materials and metal materials. For example, ceramic materials include sintered graphite. Metal materials include steel and aluminum.

[0051] (Method for manufacturing cylindrical articles) The method for manufacturing a cylindrical article using the cutting tool according to this embodiment basically includes the following steps 1 to 4. The dimensions of the cylindrical article to be manufactured can be set appropriately depending on the intended use. (Step 1) A step of cutting a block of a predetermined shape (e.g., a rectangular parallelepiped block) with the required dimensions from the workpiece using an arbitrary cutting machine. (Step 2) Using a rotary cutting device (e.g., a radial drilling machine) equipped with the cutting tool according to this embodiment, the block obtained in step 1 is subjected to rough inner and outer diameter machining simultaneously to obtain a cylindrical article as a roughly machined product. (Step 3) A step of performing inner diameter machining and outer diameter machining by finishing the inner diameter and outer diameter of the cylindrical article obtained in step 2 using a lathe. (Step 4) A step of using a lathe to perform finish machining on both end surfaces of the cylindrical article that has been finished in step 3, thereby obtaining a cylindrical article as a finished product.

[0052] By using the cutting tool according to this embodiment to manufacture a cylindrical article in step 2, it is possible to shorten the working time and obtain useful effects in that the yield of the processed material can be improved.

[0053] FIG. 4 is a schematic diagram showing a cutting tool according to this embodiment mounted on a radial drilling machine. As shown in FIG. 4, the radial drilling machine 2 is a processing device including a radial arm 3 having a processing control panel 6, a support column 4 supporting the radial arm 3, and a base 5. The processing control panel 6 includes a rotary shaft 7 and a drive motor 8 for rotating the rotary shaft 7. The rotary shaft 7 is provided with a rotary disk 9 disposed therearound. The processing control panel 6 is movable along the arm direction of the radial arm 3, and can move the rotary shaft 7 vertically. The radial arm 3 can also rotate horizontally around the support column 4. Therefore, the rotary shaft 7 and rotary disk 9 attached to the processing control panel 6 can be moved to any position in the vertical and horizontal directions.

[0054] An example of a procedure for manufacturing a cylindrical article by cutting a workpiece with a cutting tool will be described. First, a cutting tool 1 with a dual-blade structure is assembled using a first cutting blade 11 and a second cutting blade 21. A predetermined number of cutting tips are attached to the cutting blades. After placing the rotating disk 9 of a radial drilling press 2 on the assembled cutting tool 1, the cutting tool 1 and the rotating disk 9 are fixed together with bolts. Meanwhile, a block-shaped workpiece 10 is placed on and fixed to the base 5 of the radial drilling press 2.

[0055] After the cutting tool 1 engaged with the rotary disk 9 is placed on the workpiece 10, cutting begins. The cutting tool 1 rotates in conjunction with the rotation of the rotary shaft 7 and the rotary disk 9, thereby cutting the workpiece 10. The first cutting blade 11 cuts out a portion corresponding to the outer diameter surface of the cylindrical article, while the second cutting blade cuts out a portion corresponding to the inner diameter surface of the cylindrical article. As cutting progresses, the cutting tool 1 moves downward and stops rotating after reaching the bottom end of the workpiece. [Example]

[0056] The following describes examples of the present invention, but the present invention is not limited to the following description.

[0057] In the examples, cutting was performed using a cutting tool within the scope of the present invention to produce a cylindrical article as a roughly machined product (Example of the present invention). Similar to the configuration shown in FIG. 2, an outer cylindrical portion and an inner cylindrical portion were concentrically arranged, and a dual-structure cutting tool was assembled using two cutting blades configured so that the inner diameter of the outer cylindrical portion was larger than the outer diameter of the inner cylindrical portion. The thicknesses of the outer cylindrical portion and the inner cylindrical portion of the cutting tool were both 6 mm, the inner diameter of the outer cylindrical portion was 448 mm, and the outer diameter of the inner cylindrical portion was 372 mm. Diamond-coated, 12 mm diameter, ultra-hard round tips were used as cutting tips attached to the tip ends of the outer cylindrical portion and the inner cylindrical portion, and A5052 high-strength aluminum alloy was used as the material for the outer cylindrical portion and the inner cylindrical portion.

[0058] The arrangement of the ultrahard round tips was the same as in the embodiment shown in Figure 2, with four round tips positioned at opposing positions at 90° intervals at the tip of the outer tube, and two round tips positioned at opposing positions at 180° intervals at the inner tube. Similarly to the embodiment shown in Figure 3, the round tips were attached with screws near the bottom ends of the end faces of the tips of the outer and inner tubes. Because the diameter (12 mm) of the round tips was larger than the wall thickness (6 mm) of the outer and inner tubes, they protruded approximately 3 mm outside the end faces of the outer and inner tubes.

[0059] 2(c) and 2(d), four 40 mm deep notches were provided at 90° intervals on the arc-shaped end of the outer cylinder, corresponding to an angular range of ±20° from the central angle. On the other hand, two 40 mm deep notches were provided at opposing 180° intervals on the arc-shaped end of the inner cylinder, corresponding to an angular range of ±20° from the central angle. In this example, the cutting tool was designed so that the outer diameter of the roughly machined product would be approximately the same as the outer dimensions of the workpiece, in order to increase the yield of the workpiece.

[0060] The cutting tool described above was mounted on the rotating disk of a radial drilling press, similar to the configuration shown in Figure 4. After the workpiece was secured to the base of the radial drilling press, the cutting tool was rotated to perform the cutting process. The workpiece was a rectangular block made of artificial graphite, measuring 445 mm wide x 445 mm deep x 225 mm thick. The cutting conditions were a cutting blade rotation speed of 77 rpm and a vertical feed rate of 0.18 mm per rotation. The cutting process took approximately 17 minutes. Including cleaning time to remove cutting powder during the process, the process was completed in a total of approximately 30 minutes, producing a roughly machined cylindrical product measuring 445 mm outer diameter, 375 mm inner diameter, and 225 mm long.

[0061] In the inventive example, the discharge of cutting powder during machining was good. Furthermore, no chipping of the cutting chips occurred, and chipping resistance was good. The outer surface, inner surface, and end surfaces of the roughly machined product were then subjected to finish machining, yielding a cylindrical finished product measuring 440 mm in outer diameter, 380 mm in inner diameter, and 200 mm in length.

[0062] As a comparative example, a cylindrical rough-machined product of the same dimensions as the example was produced using conventional lathe machining. The steps required to obtain the cylindrical article of the comparative example were (i) a machining operation to obtain an octagonal cross-section block for lathe machining, (ii) a rough machining operation to machine the outer diameter using a lathe, and (iii) a rough machining operation to machine the inner diameter using a lathe. The comparative example required approximately 15 minutes for (i), approximately 30 minutes for (ii), and approximately 30 minutes for (iii), for a total machining time of approximately 75 minutes. The above-mentioned example of the present invention significantly reduced the machining time compared to the conventional rough machining method (comparative example). [Explanation of symbols]

[0063] 1 cutting tools 2 Radial drilling machine 3 Radial Arm 4 pillars 5 Base 6 Processing control panel 7 Rotation Axis 8 Drive motor 9 Rotating Discs 10 Work material 11 First cutting blade 12 outer cylinder portion (first rotating portion) 13 Tip 14 Cutout 15 Cutting Tip 16 Inward flange 17 Angle Range 18 Inner diameter of outer cylinder 19 End face 20 Bottom end 21 Second cutting blade 22 inner cylinder portion (second rotating portion) 23 Tip 24 Cutout 25 Cutting Tip 26 Outward flange 27 angle range 28 Outer diameter of inner cylinder 31 Other end 32 bis 33 Cutting direction (rotation direction) 34 Descending direction 35 Enclosed Area

Claims

1. a first cutting blade and a second cutting blade; the first cutting blade has a cylindrical first rotating portion, and the second cutting blade has a cylindrical second rotating portion; the first rotating part and the second rotating part each have a cutting tip at a tip end thereof, a cutting tool, wherein the first rotating part and the second rotating part are arranged concentrically with respect to a rotation axis, and an inner diameter of the first rotating part is larger than an outer diameter of the second rotating part.

2. The cutting tool of claim 1 , wherein two or more of said cutting tips are spaced apart.

3. The cutting tool according to claim 1 , wherein the first rotating part and the second rotating part have cutouts near the cutting tip.

4. The cutting tool of claim 1 , wherein the cutting tip is a round tip.

5. The cutting tool according to claim 1 , wherein the first rotating part and the second rotating part are made of a high-strength aluminum alloy.

6. A method for manufacturing a cylindrical article, comprising cutting a workpiece between the first cutting blade and the second cutting blade using the cutting tool according to any one of claims 1 to 5 to manufacture a cylindrical article.

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