Tool body and cutting tool

Abstract

To provide a tool body which can suppress chattering vibration effectively while reducing costs, and to provide a cutting tool.SOLUTION: A tool body of the invention is a tool body in which a cutting insert is detachably attached to a tip and which may rotate around a rotation axis. The tool body has: a shaft-like shank part extending along the rotation axis; and a head part located at the tip side as seen in an axial direction of the shank part and may rotate around the rotation axis. The head part has: a chip pocket recessed inward from an outer peripheral surface; an insert attachment seat formed at the inner side of the chip pocket; and a cavity part at least partially located at the shank side in the axial direction relative to the insert attachment seat. A tip of the cavity part extends to a position that overlaps with the insert attachment seat in the axial direction.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a tool body and a cutting tool (boring bar) used in turning such as boring. [Background technology]

[0002] For example, a boring bar is known as a cutting tool for boring a workpiece with a pilot hole formed therein. This boring bar has a head portion of a generally cylindrical tool body, to which a tip made of, for example, cemented carbide is removably attached. This boring bar is inserted into a pilot hole in a workpiece supported by a machine tool spindle that rotates at high speed, and the cutting edge formed on the tip cuts the inner surface of the pilot hole in the workpiece. The boring bar performs cutting while the shank portion of the tool body is gripped by the machine tool and the shaft-like tool body protrudes. Therefore, chatter vibrations are likely to occur during cutting. Chatter vibrations can reduce the accuracy of the machined surface of the workpiece and shorten the tool life, thereby affecting productivity.

[0003] Therefore, in the past, attempts have been made to suppress the occurrence of chatter vibrations by increasing the rigidity of the tool body by making it out of cemented carbide, by incorporating a vibration-damping structure into the tool body, or by reducing the weight by forming grooves on the surface of the tool body (for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 3847139 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-105204 Summary of the Invention [Problem to be solved by the invention]

[0005] However, there is a concern that the cost will increase as the number of parts increases in the conventional boring bar described in Patent Document 1. Also, in the boring bar described in Patent Document 2, an end mill is used to form grooves in part of the outer circumferential surface of the tool body, but there is a limit to how much weight the tool body can be reduced by forming the grooves.

[0006] The present invention has been made in view of the above circumstances, and has an object to provide a tool body and a cutting tool that can effectively suppress chatter vibration while keeping costs down. [Means for solving the problem]

[0007] In one form of the present invention, a tool body has a cutting insert removably attached to its tip and is rotatable around the axis of a rotation shaft, and has an axial shank portion extending along the rotation shaft and a head portion located on the axial tip side of the shank portion, and the head portion has a chip pocket recessed inward from the outer peripheral surface, an insert mounting seat formed inside the chip pocket, and a hollow portion, at least a portion of which is located axially closer to the shank portion than the insert mounting seat, and the tip of the hollow portion extends to a position where it overlaps with the insert mounting seat in the axial direction, and the base end side of the hollow portion is blocked by the solid shank portion. In the above-described tool body, the hollow portion may be in communication with an opening formed in the outer peripheral surface of the head portion, and a lattice structure may be formed in at least a part of the opening and the hollow portion.

[0008] According to this configuration, by providing a cavity inside the head portion located at the tip side of the tool body, the weight of the tool tip side can be reduced, making it less likely to generate chatter vibrations that tend to occur when machining with a cutting insert attached. By reducing the weight of the tool tip side, the natural frequency of the tool body during cutting can be increased, increasing the deviation from the frequency of vibration caused by cutting and suppressing resonance with the cutting surface due to chatter. This improves the accuracy of the machined surface of the workpiece and extends the tool life. Furthermore, because the tip of the cavity extends to a position where it axially overlaps with the insert mounting seat, the weight of the tool tip side can be further reduced.

[0009] In the tool body according to one aspect of the present invention, the cavity may be configured to communicate with an opening formed in an outer peripheral surface of the head portion. According to this configuration, by providing an opening communicating with the hollow portion, it is possible to partially eliminate the thickness of the head portion, thereby achieving further weight reduction, thereby making it possible to further suppress chatter vibrations.

[0010] In the tool body according to one aspect of the present invention, the opening may be formed on a radially opposite side of the insert mounting seat across the rotation axis. According to this configuration, by providing an opening on the radially opposite side of the insert mounting seat, rigidity is ensured on the cutting insert side where the cutting load is large, and chatter vibration can be further suppressed.

[0011] In the tool body according to one aspect of the present invention, a lattice structure may be formed in at least a part of the opening and the cavity. This configuration can prevent chips and the like from entering the cavity.

[0012] In one embodiment of the tool body of the present invention, the hollow portion may extend along the rotation axis and have a tapered hole portion whose diameter increases toward the axial tip of the head portion. According to this configuration, the tapered shape of the hole allows the thickness of the axial tip side to be gradually reduced, so that the rigidity of the base end side can be ensured while reducing the weight of the tool tip side.

[0013] In one embodiment of the tool body of the present invention, the hollow portion may extend along the rotation axis and have a hole portion that is linearly shaped toward the axial tip of the head portion. This configuration reduces the overall axial weight of the head, suppressing chatter vibrations during cutting and improving machining accuracy. Furthermore, the simple hole shape makes it easy to manufacture, and the hole dimensions ensure a minimum level of tool rigidity, allowing for a minimum wall thickness and reducing material costs.

[0014] In the tool body according to one aspect of the present invention, a base end side of the hollow portion may be closed by the shank portion having a solid shape. According to this configuration, the rigidity of the base end side of the tool is ensured by the solid shank.

[0015] In the tool body according to one aspect of the present invention, the hollow portion may be formed on the axial tip side of the shank portion when the head portion is additively manufactured. According to this configuration, the head portion having the cavity can be integrally formed with the shank portion, thereby improving the rigidity of the tool and reducing costs.

[0016] A cutting tool according to one embodiment of the present invention includes the above-described tool body and a cutting insert removably attached to a tip of the tool body. According to this configuration, by providing the tool body capable of suppressing chatter vibration, it is possible to improve the accuracy of the machined surface of the workpiece. [Effects of the Invention]

[0017] According to the tool body and cutting tool of the present invention, chatter vibration can be effectively suppressed while keeping costs down. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a perspective view showing a boring bar according to a first embodiment. [Figure 2] FIG. 2 is an enlarged perspective view of a head portion of the boring bar of the first embodiment. [Figure 3] FIG. 3 is an enlarged side view of the head portion of the boring bar of the first embodiment. [Figure 4] FIG. 4 is an enlarged side view of the head portion of the boring bar of the first embodiment, as seen from the direction of arrow F in FIG. [Figure 5] FIG. 5 is a view of the boring bar of the first embodiment as seen from the axial tip side. [Figure 6] FIG. 6 is a cross-sectional view showing holes in the first modification. [Figure 7] FIG. 7 is a cross-sectional view showing holes in the second modification. [Figure 8] FIG. 8 is a cross-sectional view showing holes in the third modification. [Figure 9] FIG. 9 is a cross-sectional view showing a boring bar (cutting tool) of the second embodiment. [Figure 10] FIG. 10 is a cross-sectional view showing a boring bar according to the third embodiment. [Figure 11A] FIG. 11A is a perspective view showing a boring bar according to a first embodiment of the present invention. [Figure 11B] FIG. 11B is a perspective view showing the boring bar of Comparative Example 1. [Figure 11C] FIG. 11C is a perspective view showing the boring bar of Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0019] A boring bar (boring tool) 1 according to one embodiment of the present invention will be described below with reference to the drawings. The boring bar (cutting tool) 1 of this embodiment is used to perform turning operations such as boring on a workpiece such as a metal material that is rotated around a rotation axis. This boring bar 1 is particularly suitable for turning operations that require high precision, such as precision boring of deep holes.

[0020] First Embodiment [Outline of boring bar configuration] FIG. 1 is a perspective view showing a boring bar 1 of the first embodiment. 1, the boring bar 1 of this embodiment is an indexable boring bar equipped with a cutting insert 4 made of cemented carbide and a tool body 2 made of steel. The boring bar 1 is supported by the spindle of a machine tool and machines the inner diameter of a workpiece that rotates around a rotation axis CO.

[0021] The tool body 2 has a generally rod-like shape overall. The tool body 2 comprises a cylindrical shank portion 21 extending along the rotation axis CO, and a head portion 22 located on the axial tip side of the shank portion 21. In this embodiment, the head portion 22 is fabricated by additive manufacturing on one end side of the shank portion 21. The tool body 2 may be formed from a metal material such as steel, or from a hard material such as cemented carbide.

[0022] 1, the cutting insert 4 is disposed on the tip side of the head portion 22 of the tool body 2. The cutting insert 4 has a cutting edge 3 that protrudes radially outward, perpendicular to the rotation axis CO of the tool body 2. The cutting insert 4 is made of a hard material such as cemented carbide.

[0023] Each component will be described in detail below with reference to the drawings.

[0024] FIG. 2 is an enlarged perspective view of the head portion 22 of the boring bar 1 of the first embodiment. 3 and 4 are enlarged side views showing the head portion 22 of the boring bar 1 of the first embodiment. Fig. 4 is a view seen from the direction of arrow F in Fig. 3. Fig. 5 is a view seen from the axial tip side of the boring bar 1 of the first embodiment.

[0025] (Cutting insert) 2 and 3, the cutting insert 4 is plate-shaped, and in the illustrated example, is formed into an equilateral triangular plate shape in a plan view along the center line O. The cutting insert 4 is attached to the tool body 2 and used together with the tool body 2 as a cutting tool. The cutting insert 4 is detachably attached to an insert mounting seat 11 of the tool body 2 by a clamp screw 12. The clamp screw 12 is inserted into a mounting hole (not shown) of the cutting insert 4. When attached to the tool body 2, the cutting insert 4 is constrained by the insert mounting seat 11 of the tool body 2.

[0026] The cutting insert 4 has a rake face 4a constituting one surface axially facing the center line O, a seating surface 4b constituting the other surface, a side surface 4c connecting the rake face 4a and the seating surface 4b, a cutting edge 3 formed on the ridge line where the rake face 4a and the side surface 4c intersect, and a mounting hole (not shown) provided coaxially with the center line O. The mounting hole is a through hole formed in the thickness direction of the cutting insert 4 and opening to both the rake face 4a and the seating surface 4b. The seating surface 4b is sized so that it is included inside the area projected in the thickness direction of the rake face 4a.

[0027] (Tool body) As shown in FIGS. 2 and 3 , the tool body 2 has a head portion 22 integrally formed by additive manufacturing on the axial tip side of the shank portion 21. The head portion 22 of the tool body 2 has a recessed chip pocket 6 formed by cutting out the outer peripheral surface 22b from the axial midpoint to the tip. Furthermore, a first recess 7 is formed by cutting out the outer peripheral surface 22b adjacent to the chip pocket 6 of the tool body 2 up to the chip pocket 6. The axial length of the first recess 7 is approximately half or less of the axial length of the head portion 22. A second recess 8 is formed by cutting out a portion of the outer peripheral surface 22b circumferentially adjacent to the first recess 7. The head portion 22 also has a third recess 9 circumferentially adjacent to the first recess 7, the second recess 8, and the chip pocket 6. The third recess 9 is formed by cutting out the outer peripheral surface 22b from the axial midpoint to the tip.

[0028] An insert mounting seat 11, which is a recessed portion having a substantially triangular plate shape, is formed in the chip pocket 6. The insert mounting seat 11 is a base on which the cutting insert 4 is mounted. When the cutting insert 4 is mounted to the tool body 2, the cutting insert 4 is restrained by the insert mounting seat 11 of the tool body 2.

[0029] 3 and 5, the insert mounting seat 11 has a bottom restraint surface 11a, and first and second side restraint surfaces 11b and 11c that are substantially perpendicular to the bottom restraint surface 11a. The bottom restraint surface 11a, the first side restraint surface 11b, and the second side restraint surface 11c are all smooth surfaces.

[0030] The bottom restraint surface 11a is a surface facing one circumferential side. The bottom restraint surface 11a is a surface facing the seating surface 4b of the cutting insert 4 and has a substantially triangular shape when viewed from one circumferential side. The seating surface 4b side of the cutting insert 4 is restrained by abutting against the bottom restraint surface 11a. A screw hole (not shown) into which a clamp screw 12 is inserted is formed in approximately the center of the bottom restraint surface 11a.

[0031] The first side restraint surface 11b faces the side surface 4c2 facing radially inward among the three side surfaces of the cutting insert 4 when the cutting insert 4 is attached to the insert mounting seat 11. The side surface 4c2 side of the cutting insert 4 is restrained by abutting against the first side restraint surface 11b.

[0032] The second side restraint surface 11c faces a side surface 4c3 facing radially outward when the cutting insert 4 is attached to the insert mounting seat 11. The side surface 4c3 of the cutting insert 4 is restrained by abutting against the second side restraint surface 11c.

[0033] As shown in FIG. 3, when the cutting insert 4 is attached to the insert mounting seat 11, the side surface 4c1 faces the axial tip. The cutting insert 4 is attached so that the side surface 4c1 forms a predetermined angle θ with respect to the rotation axis CO. As a result, the cutting insert 4 is inclined so that it gradually protrudes toward the axial tip as it moves radially outward from the tool body 2. The corner where the side surface 4c1 and the side surface 4c3 of the cutting insert 4 intersect protrudes radially outward beyond the outer circumferential surface of the head portion 22. This corner becomes the cutting point Q for the workpiece.

[0034] 4 and 5, a recessed groove 14 recessed toward the insert mounting seat 11 is formed on the back side of the insert mounting seat 11. The recessed groove 14 is a groove that opens on one circumferential side and on the opposite side. By providing the recessed groove 14, the weight of the tip side of the tool body 2 is reduced.

[0035] 3 and 4, the tool body 2 of this embodiment has a hole (cavity) 13 inside the head portion 22. The hole 13 has a non-linear shape and extends along the axial direction of the tool body 2. The hole 13 has a first hole (hole) 13a that is tapered and gradually reduces in diameter from the base end on the shank portion 21 side toward the center of the head portion 22 in the axial direction, a second hole (hole) 13b that is tapered and gradually increases in diameter from the first hole 13a toward the tip end of the tool body 2, and a third hole 13c that communicates with a groove opening 15 formed on the outer peripheral surface of the head portion 22. The first hole 13a and the second hole 13b are connected at their reduced diameter sides and form tapered shapes that increase in diameter in opposite directions in the axial direction.

[0036] The axial length of the first hole 13a is shorter than the axial length of the second hole 13b and is equal to or less than half the axial length of the head portion 22. Note that the ratio of the lengths of the holes 13a and 13b to the axial length of the head portion 22 is not limited to this and can be changed as appropriate. In the head portion 22 of this embodiment, a step 16 is formed at a position approximately two-thirds of the axial length from the tip. With the step 16 as a boundary, the diameter of the portion on the base end side of the step 16 approximately matches the diameter of the shank portion 21. The diameter on the tip end side of the step 16 is slightly smaller than that on the base end side. The boundary between the first hole portion 13a and the second hole portion 13b of the hole 13 approximately matches the step 16 in the axial direction.

[0037] As shown in FIG. 4, the tip of the hole 13 (third hole portion 13c) opens into the third recess 9 of the head portion 22. A groove opening (opening) 15 communicating with the hole 13 is located on the base end side of the third recess 9 in the axial direction. As shown in FIG. 3, the hole 13 extends in the axial direction to a position overlapping with the insert mounting seat 11. The tip of the hole 13 (groove opening 15) extends to a position overlapping with the insert mounting seat 11 in the axial direction. In other words, the tip of the hole 13 (groove opening 15) is located closer to the tip of the tool body 2 than the base end 11d of the insert mounting seat 11. Furthermore, as shown in FIG. 4, the tip of the hole 13 (groove opening 15) also overlaps with the groove 14 formed on the back side of the insert mounting seat 11 in the axial direction.

[0038] The void 13 formed in the head portion 22 is formed approximately coaxially with the rotation axis CO of the tool body 2. This prevents deviation of the center of gravity of the rotation of the tool body 2 during cutting. The void 13 is formed when the head portion 22 is formed by additive manufacturing on the axial tip side of the shank portion 21. Therefore, the base end side of the void 13 is closed by the shank portion 21. In other words, the void 13 is not formed inside the shank portion 21, making it solid, thereby ensuring rigidity on the base end side of the tool. Because the void 13 is formed when the head portion 22 is formed by additive manufacturing on the axial tip side of the shank portion 21, the shank portion 21 and the head portion 22 can be made into an integrated structure. This further increases the tool rigidity and reduces costs because the number of parts does not increase.

[0039] 5, the groove opening 15 of the hole 13 and the insert mounting seat 11 are adjacent to each other in the radial direction of the tool body 2. The groove opening 15 is formed on the radially opposite side of the cutting point Q of the cutting insert 4 across the rotation axis CO of the tool body 2. Furthermore, the bottom restraint surface 11a of the insert mounting seat 11 faces toward one circumferential side, while the groove opening 15 of the hole 13 faces radially outward. The size of the groove opening 15 is not limited to the size shown in the figure and can be changed as appropriate.

[0040] According to the configuration of this embodiment, by providing the holes 13 inside the head portion 22 of the tool body 2, it is possible to significantly reduce the weight of the tip side (head portion 22) of the tool body 2. Furthermore, by forming the holes 13 in the axial direction up to a position where they overlap with part of the insert mounting seat 11, it is possible to further reduce the weight of the tip side. A boring bar 1 having a tool body 2 that is lighter than conventional tools is less likely to generate chatter vibrations that tend to occur when cutting is performed with the tool body 2 protruding a long way, and it is possible to suppress resonance with the cutting surface due to chatter vibrations. In addition, by reducing the weight of the tip of the tool while maintaining the rigidity of the tool together with the solid shank portion 21, the natural frequency of the boring bar 1 during cutting processing is increased, the deviation from the vibration frequency due to cutting is increased, and resonance with the cutting surface due to chatter vibrations can be suppressed. In this way, by preventing the occurrence of resonance during machining, chatter vibrations are less likely to occur, and the accuracy of the machined surface of the workpiece can be improved.

[0041] In addition, because the tip of the hole 13 extending axially in the head portion 22 extends to a position where it axially overlaps with the insert mounting seat 11, it is possible to further reduce the weight of the tip side of the tool. Furthermore, by forming a groove opening 15 that communicates with the tip side of the hole 13 on the outer peripheral surface of the head portion 22, it is possible to partially eliminate the thickness of the head portion 22, thereby further reducing the weight of the head portion 22. This makes it possible to further suppress chatter vibrations.

[0042] Furthermore, the tapered shape of the second hole portion 13b of the hole 13 allows the thickness of the axial tip side to be gradually reduced, so that the weight of the tool tip side can be reduced while ensuring rigidity on the base end side.

[0043] Furthermore, by suppressing chatter vibration, the boring bar 1 can be extended to a greater extent, enabling high-precision finishing of the inner surface of a deeper pilot hole. Tool life can also be extended.

[0044] The first embodiment of the present invention has been described above in detail with reference to the drawings, but the specific configuration is not limited to this embodiment, and design changes and the like are also included within the scope that does not deviate from the gist of the present invention. For example, the shape of the holes 13 is not limited to that of the first embodiment. Modifications 1 to 3 will be described below. In the following description, the same reference numerals will be used to designate components that are common to those already described, and redundant description will be omitted.

[0045] (Variation 1) The hole (hollow portion) 13 in the above embodiment has two tapered portions, a first hole portion 13a and a second hole portion 13b, which expand (contract) in diameter in opposite directions in the axial direction, but the shape of the hole 13 is not limited to this. 6 is a cross-sectional view showing holes 13A in Modification 1. Modification 1 of the first embodiment will be described with reference to FIG.

[0046] As shown in Figure 6, the hole 13A in Modification 1 has a constant hole diameter over a portion of the axial direction. Of the hole 13A, the first hole portion 13a, which is located closest to the shank portion 21, is configured as a hole with a constant diameter in the axial direction. The tip side of the first hole portion 13a is connected to the base side of the second hole portion 13b, which has a tapered shape whose diameter gradually decreases from the tip side to the base side. The diameter of the first hole portion 13a is approximately the same as the minimum diameter of the second hole portion 13b.

[0047] According to this configuration, the tapered second hole portion 13b that expands in diameter toward the tip reduces the thickness of the tip side of the head portion 22, thereby reducing the weight of the tip side of the head portion 22, while providing the first hole portion 13a that has a smaller diameter than the second hole portion 13b increases the rigidity of the base end side of the head portion 22. As a result, chatter vibration during cutting can be suppressed and machining accuracy can be improved, just like in the above embodiment.

[0048] (Variation 2) FIG. 7 is a cross-sectional view showing a hole 13B of the second modification. 7, the hole (hollow portion) 13B of the second modification has a hole portion 13d and a third hole portion 13c, which have the same diameter in the axial direction. The hole portion 13d is a linear hole that is substantially coaxial with the rotation axis CO of the tool body 2. The diameter of the hole portion 13d is set to a dimension that allows for weight reduction while ensuring the rigidity of the head portion 22.

[0049] This configuration reduces the overall axial weight of the head portion 22, thereby suppressing chatter vibration during cutting and improving machining accuracy, as in the above embodiment. In addition, the simple hole shape makes it easy to manufacture, and by setting the hole dimensions to ensure the minimum tool rigidity, the wall thickness can be minimized, thereby reducing material costs.

[0050] (Variation 3) FIG. 8 is a cross-sectional view showing a hole 13C of the third modification. 8, the hole (hollow portion) 13C of the third modification has a hemispherical hole portion 13e and a third hole portion 13c. The hole 13C is formed on the tool body 2 closer to the tip side than the axial center of the head portion 22. The base end side of the head portion 22 is solid.

[0051] This configuration makes it possible to reduce the weight of only the tip end of the tool body 2 while increasing the rigidity of the base end of the head portion 22. Chatter vibration during machining can be suppressed more effectively than when the entire head portion 22 is solid.

[0052] Although not shown in the drawings, the head portion 22 may have a hole whose diameter gradually decreases from the distal end to the proximal end. This reduces the thickness of the head portion 22 on the distal end side, thereby reducing its weight, while ensuring the thickness on the proximal end side to increase its rigidity.

[0053] Although the first embodiment and modifications 1 to 3 of the present invention have been described in detail above with reference to the drawings, the specific configurations are not limited to these embodiments and modifications, and include design changes and the like that do not deviate from the gist of the present invention. Furthermore, the components shown in the first embodiment and modifications 1 to 3 above can be configured by appropriately combining them.

[0054] Second Embodiment Next, a boring bar 20 according to a second embodiment will be described with reference to Fig. 9. In the following description, components common to those already described will be assigned the same reference numerals and duplicated description will be omitted.

[0055] FIG. 9 is a cross-sectional view showing a boring bar (cutting tool) 20 of the second embodiment. The boring bar 20 of this embodiment has a tool body 2A in which a lattice structure is partially formed. As shown in Fig. 9, a lattice structure 23 is formed inside a hole (cavity) 13 of the tool body 2A. The lattice structure (lattice structure) 23 is formed in almost the entire hole 13. The lattice structure 23 is formed together with the hole 13 when the head portion 22 is additively manufactured relative to the shank portion 21. The line width and gap dimensions of the lattice structure 23 are set appropriately in consideration of the rigidity and weight reduction of the head portion 22.

[0056] According to the configuration of this embodiment, it is possible to ensure the strength of the entire axial direction of the tool body 2A and reduce its weight by providing the lattice structure 23 on the entire inside of the holes 13 of the head portion 22. Furthermore, by forming a lattice structure inside the holes 13, it is possible to prevent chips and the like from entering the holes 13 through the groove openings 15.

[0057] In this embodiment, the lattice structure 23 is formed over the entire hole 13, but this configuration is not limited to this. For example, the lattice structure 23 may be provided in at least a portion of the hole 13 and the groove opening 15. This makes it possible to reduce material costs while ensuring tool rigidity. Also, the lattice structure 23 may not be provided inside the hole 13, but only in the groove opening 15. This makes it possible to achieve a structure that prevents chips from entering while maximizing the weight reduction of the head portion 22. Moreover, instead of the grid structure 23, a porous structure having a large number of holes may be formed within the hole 13 to form a lattice structure.

[0058] Third Embodiment FIG. 10 is a cross-sectional view showing a boring bar 30 according to the third embodiment. The boring bar (cutting tool) 30 of this embodiment has a tool body 2B in which a cavity 33 is formed inside a head portion 22. As shown in Fig. 10, there is no opening communicating with the cavity 33 on the outer peripheral surface of the head portion 22. According to the configuration of this embodiment, the hollow portion 33 reduces the weight of the tip (head portion 22) of the tool body 2B, while the absence of an opening on the outer peripheral surface prevents chips and the like from entering the head portion 22.

[0059] Although the second and third embodiments of the present invention have been described above in detail with reference to the drawings, the specific configurations are not limited to these embodiments, and the configurations (components) described in the first embodiment, modifications, and notes above may be combined within the scope of the present invention, and additions, omissions, substitutions, and other modifications of the configurations are possible. Furthermore, the present invention is not limited to the above-described embodiments, but is limited only by the claims. [Example]

[0060] The present invention will be specifically described below with reference to examples, although the present invention is not limited to these examples. Fig. 11A is a perspective view showing a boring bar 1 according to a first embodiment of the present invention. Fig. 11B is a perspective view showing a boring bar 80 according to a comparative example 1. Fig. 11C is a perspective view showing a boring bar 90 according to a comparative example 2.

[0061] 11A is the boring bar of the first embodiment described above, and has a cavity 13 in a hollow head portion 22. The cavity 13 communicates with a groove opening 15 formed on the outer peripheral surface of the head portion 22.

[0062] The boring bar 80 of Comparative Example 1 shown in FIG. 11B has a groove 81 recessed radially inward from the outer peripheral surface of the solid head portion 22. The groove 81 is a concave groove formed by cutting the outer peripheral surface of the head portion 22 with an end mill. As in the present invention, the configuration is designed to reduce the weight of the tip side of the tool body 2. The groove 81 is a groove formed by cutting the outer peripheral surface adjacent to the chip pocket 6 with an end mill. The groove 81 opens in a direction different from the insert mounting seat 11 and is located radially opposite the cutting point Q of the cutting insert 4 across the rotation axis CO.

[0063] The boring bar 90 of Comparative Example 2 shown in Figure 11C is a standard boring bar, and has an insert mounting seat 11 formed in a groove portion 91 cut out on one radial side of the tip end of the solid cylindrical head portion 22.

[0064] The various boring bars 1, 80, and 90 shown in FIGS. 11A to 11C were attached to the spindle of a machine tool, and the natural frequencies were calculated assuming cutting processing under the following conditions.

[0065] (Cutting conditions) The cutting conditions are as follows: Workpiece material: SCM440 (chromium-molybdenum steel) Tool body material: Steel Shank diameter: D=16mm Tool feed rate: f=0.05mm / rev Depth of cut: ap=1mm Cutting speed: vc=150m / min Cutting environment: DRY Processing diameter: 32mm to 38mm in diameter Ratio of protrusion to shank diameter: L / D=3 Principal force: Fy=188.1N Back force: Fx=34.1N Feed force: Fz=12.5N

[0066] [Table 1]

[0067] The weights of boring bars 1, 80, and 90 are shown in Table 1: Weight of the boring bar 1 of the present invention: 36.4 g Weight of boring bar 80 of Comparative Example 1: 52.9 g Weight of boring bar 90 of Comparative Example 2: 70.6 g

[0068] Table 1 shows the natural frequencies when cutting workpieces using various boring bars 1, 80, and 90. As shown in Table 1, the lighter the weight of the boring bar, the higher the natural frequency. Specifically, the boring bar 80 of Comparative Example 1 was 25% lighter in weight than the boring bar 90 of Comparative Example 2, and the natural frequency was approximately 25% higher. Furthermore, the boring bar 1 of the present invention was 15% lighter in weight than the boring bar 80 of Comparative Example 1, and the natural frequency was approximately 18% higher. Compared to Comparative Examples 1 and 2, the boring bar 1 of the present invention is expected to have improved chatter resistance due to the increased natural frequency. [Industrial Applicability]

[0069] According to the boring bar of the present invention, even when the ratio L / D is set large, the occurrence of chatter vibration can be significantly suppressed, and the boring bar can meet the requirements for various cutting processes. Therefore, the boring bar has industrial applicability. [Explanation of symbols]

[0070] 1, 20, 30...Boring bar (cutting tool) 2,2A,2B…Tool body 4...Cutting insert 6...Chip pocket 11...Insert mounting seat 13a...First hole (hole) 13b...Second hole (hole) 13d…hole 13e…hole 15...Groove opening (opening) 21...Shank 22...Head 22b…Outer surface 23... Lattice structure 33...Cavity part CO...Rotation axis Q…Cutting point

Claims

1. A tool body having a cutting insert detachably attached to a tip thereof and rotatable around a rotation axis, a shaft-shaped shank portion extending along the rotation axis; a head portion located on the axial tip side of the shank portion, The head portion has a chip pocket recessed inward from the outer circumferential surface. an insert mounting seat formed inside the chip pocket; a hollow portion, at least a portion of which is located closer to the shank portion in the axial direction than the insert mounting seat, a tip end of the hollow portion extends to a position overlapping with the insert mounting seat in the axial direction, The base end side of the hollow portion is closed by the shank portion having a solid shape. Tool body.

2. The hollow portion communicates with an opening formed on the outer peripheral surface of the head portion, a lattice structure is formed in at least a portion of the opening and the cavity; The tool body according to claim 1 .

3. The tool body according to claim 2 , wherein the opening is formed on a radially opposite side of the insert mounting seat across the rotation axis.

4. the cavity extends along the rotation axis, The tool body according to claim 1 , further comprising a tapered hole portion whose diameter increases toward the axial tip of the head portion.

5. the cavity extends along the rotation axis, The tool body according to claim 1 , further comprising a hole portion that is linearly shaped toward a tip end of the head portion in the axial direction.

6. The hollow portion is formed on the axial tip side of the shank portion when the head portion is additively manufactured. The tool body according to any one of claims 1 to 5.

7. The tool body according to any one of claims 1 to 6; the cutting insert being detachably attached to the tip of the tool body.

Images