Rotary cutting tool, insert, and holder

Abstract

The present invention suppresses the cost of a rotary cutting tool in which a holder and an insert are separate, while enhancing the precision of centering in the rotary cutting tool. In this rotary cutting tool, the insert comprises a cutting blade formed in one end part and / or side surface, a protruding part formed in the other end part, and a through-hole that runs through the insert along the axial direction thereof, the protruding part has a tapered surface that tapers so that the outside diameter thereof decreases progressively from the one end part toward the other end part, the holder has a long shape, and has formed therein a recessed part which is recessed to the one end part and in which the insert is fixed, and the recessed part is provided with a concave accommodating part in which the protruding part is accommodated, the accommodating part having formed therein a tapered seat surface which is tapered so that the inside diameter thereof increases progressively from the other end part toward the one end part, and a threaded part which is positioned closer to the other end part of the holder than the accommodating part and in which an open end part of the threaded part is connected to the accommodating part.

Description

Rotary Cutting Tools, Inserts, and Holders

[0001] The present invention relates to a rotary cutting tool, an insert, and a holder.

[0002] Rotary cutting tools such as end mills are known (see, for example, Patent Documents 1 to 3). In the end mill described in Patent Document 1, a male thread formed on an end mill body having a peripheral cutting edge is threadedly engaged with a female thread formed on the shank, thereby fixing the shank and the end mill body. In a removable tip rotary tool described in Patent Document 2, a mounting screw passing through the tip is threadedly engaged with a female thread formed on the body, thereby fixing the body and the tip. In a rotary tool described in Patent Document 3, a mounting screw passing through the replaceable cutting tool is threadedly engaged with a female thread formed on the shank, thereby fixing the shank and the replaceable cutting tool.

[0003] International Publication No. 2019 / 188135 Patent No. 5731643 Patent No. 4791826

[0004] If a holder such as a shank attached to the device and an insert with a cutting edge formed at the tip were manufactured as an integrated tool, the entire tool would need to be replaced if the insert were damaged, which would increase manufacturing costs. Therefore, as described in Patent Documents 1 to 3, by making the holder and the insert separate, the manufacturing costs of the rotary cutting tool can be reduced.

[0005] However, in the tools described in Patent Documents 1 and 2, the alignment between the central axis of the holder and the central axis of the insert is determined by the mating female and male threads, leaving room for improvement in centering accuracy. Furthermore, in the end mill described in Patent Document 1, the male thread is brazed to the insert, so improving the accuracy of the brazing process is also necessary to improve centering accuracy. Furthermore, in the rotary tool described in Patent Document 3, the holder and the insert are formed with symmetrical mating shapes across the central axis to allow the holder and the insert to fit together. While the mating shapes formed in the holder and the insert improve centering accuracy, machining the complex mating shapes increases processing costs.

[0006] The present invention has been made to solve at least some of the above-mentioned problems, and aims to reduce costs while improving the centering accuracy of rotary cutting tools in which the holder and insert are separate.

[0007] The present invention has been made to solve at least part of the above-mentioned problems, and can be realized in the following forms.

[0008] (1) According to one aspect of the present invention, there is provided a rotary cutting tool including a holder and an insert fixed to the holder. In this rotary cutting tool, the insert comprises a cutting edge formed on at least one of one end and a side surface of the insert in the axial direction, a convex portion formed on the other end of the insert in the axial direction and protruding along the axial direction of the insert, and a through hole penetrating the insert along the axial direction of the insert, the convex portion having a tapered surface such that the outer diameter of the convex portion decreases from the one end side of the insert toward the other end side, the holder has an elongated shape and has a recess formed along the axial direction of the holder at one end to which the insert is fixed, the recess being a concave-shaped accommodating portion that accommodates the convex portion of the insert, the accommodating portion having a tapered seat surface formed such that the inner diameter increases from the other end side of the holder toward the one end side, and a female threaded portion located closer to the other end of the holder than the accommodating portion and formed along the axial direction of the holder, the open end of the female threaded portion being connected to the accommodating portion.

[0009] According to this configuration, a screw is inserted into the through-hole of the insert, and the male thread of the inserted screw threads into the female thread of the holder, thereby securing the insert to the holder. In other words, since the holder and the insert are formed separately, if the cutting edge of the insert is damaged, only the insert can be replaced without having to replace the entire rotary cutting tool, including the holder. In particular, this configuration eliminates the need for centerless machining, which is performed on the holder when the holder and the insert are integrated. Furthermore, since the insert can be replaced while the holder is still attached to the device that rotates the rotary cutting tool, the time required to adjust the origin of the rotary cutting tool relative to the device can be reduced. This reduces the cost of the rotary cutting tool and the manufacturing cost of the parts cut by the tool. Furthermore, when the male thread and female thread are tightened, the tapered seating surface formed in the holder's housing contacts the tapered surface formed on the insert's protrusion. When the screw is rotated in the tightening direction after contact, the holder and the insert approach each other along the axial direction, and the contact between the tapered seating surface and the tapered surface aligns their central axes. In this configuration, the tapered seating surface formed on the holder and the tapered surface formed on the insert are not complex in shape, which simplifies the machining of the recessed portion of the holder and the protruding portion of the insert. Furthermore, because positioning is achieved by the fit between the tapered seating surface and the tapered surface, misalignment of the insert relative to the holder can be suppressed.

[0010] (2) In the rotary cutting tool described in the above aspect (1), the angle between the tapered bearing surface and the holder axis in a longitudinal cross section of the holder including the holder axis may be 30 degrees or more and 60 degrees or less. With this configuration, since the angle between the tapered bearing surface and the holder axis is 30 degrees or more, the thickness of the portion of the holder where the recess is formed does not become too thin, and a decrease in the rigidity of the holder can be suppressed. Furthermore, since the angle between the tapered bearing surface and the holder axis is 60 degrees or less, misalignment of the insert with respect to the holder during fastening can be suppressed, and the insert can be prevented from being fixed at an angle with respect to the holder.

[0011] (3) In the rotary cutting tool according to the above-mentioned aspect (1) or (2), the insert may be fixed to the holder by a bolt that is inserted through the through hole and threaded into the female thread portion, and the rotary cutting tool may further include a rotation prevention mechanism that prevents the insert from rotating relative to the holder about an axis of the holder. According to this configuration, the insert fixed to the holder is prevented from rotating about an axis of the holder by the rotation prevention mechanism, so that the rotary cutting tool can fully function as a rotary cutting tool.

[0012] (4) In the rotary cutting tool according to any one of the above-described modes (1) to (3), the through hole may have an inner diameter larger at the one end side of the insert than at the other end side, and an engagement surface may be formed at a position where the inner diameters change. With this configuration, the head of a bolt inserted into the through hole can be hooked onto the engagement surface. This allows the position of the bolt in the axial direction relative to the insert to be regulated.

[0013] (5) In the rotary cutting tool according to any one of the above-mentioned modes (1) to (4), the cutting edge may be an end mill having at least one of a peripheral cutting edge and a bottom cutting edge. With this configuration, it is possible to provide an end mill at reduced cost.

[0014] (6) According to another aspect of the present invention, there is provided an insert that is fixed to a holder for a rotary cutting tool. This insert includes a cutting edge formed at one axial end of the insert, a convex portion formed at the other axial end of the insert and projecting along the axial direction of the insert, and a through-hole that penetrates the insert along the axial direction of the insert. The convex portion has a tapered surface such that the outer diameter of the convex portion decreases from the one end to the other end of the insert. According to this configuration, if a holder has a tapered seating surface that engages with the tapered surface of the insert and has a female threaded portion on the side opposite the tapered seating surface facing the insert, the insert is fixed to the holder by a screw inserted through the through-hole threading into the female threaded portion. Therefore, if the cutting edge of the insert is damaged, it is possible to replace only the insert without replacing the holder to which the insert is fixed. This reduces the cost of the rotary cutting tool. In addition, since the positioning of the insert relative to the holder is determined by the tapered surface, which does not have a complex shape, machining of the holder and the insert is simplified. Furthermore, because positioning is determined by the tapered surface, misalignment of the insert relative to the holder can be suppressed.

[0015] (7) According to another aspect of the present invention, a holder for use in a rotary cutting tool and for securing an insert is provided. The holder has an elongated shape, and a recess formed along the axial direction of the holder on at least one of the end and side surfaces to which the insert is secured. The recess is a concave-shaped receiving portion for receiving at least a portion of the insert. The receiving portion has a tapered seating surface formed so that the inner diameter increases from the other end of the holder toward the one end, and a female threaded portion located closer to the other end of the holder than the receiving portion and formed along the axial direction of the holder, the open end of the female threaded portion being connected to the receiving portion. With this configuration, if a through hole through which a screw can be inserted is formed in an insert having a tapered surface that engages with the tapered seating surface of the holder, the screw inserted through the through hole threads into the female threaded portion, thereby securing the insert to the holder. Therefore, if the cutting edge of an insert secured to the holder is damaged, only the insert needs to be replaced. This reduces the cost of the rotary cutting tool. In addition, since the positioning of the insert relative to the holder is determined by the tapered seating surface, which does not have a complex shape, machining of the holder and the insert is simplified. Furthermore, because positioning is determined by the tapered seating surface, misalignment of the insert fixed to the holder can be suppressed.

[0016] The present invention can be realized in various forms, for example, in the form of a rotary cutting tool, a holder, an insert, an end mill, a reamer, a cutter, and a system including these, a method for manufacturing a rotary cutting tool, and a system including these, etc.

[0017] 1 is a schematic perspective view of a rotary cutting tool according to one embodiment of the present invention; FIG. 2 is a schematic exploded perspective view of the rotary cutting tool; FIG. 3 is a schematic cross-sectional view of the rotary cutting tool; FIG. 4 is a schematic exploded perspective view of a holder and an insert according to a second embodiment; FIG. 5 is a schematic cross-sectional view of the rotary cutting tool according to the second embodiment; FIG. 6 is a schematic exploded perspective view of a holder and an insert according to a third embodiment; FIG. 7 is an enlarged perspective view of a recess of the holder according to the third embodiment; FIG. 8 is a schematic cross-sectional view of the rotary cutting tool according to the third embodiment; FIG. 9 is a schematic exploded perspective view of a holder and an insert according to a fourth embodiment; FIG. 10 is a schematic cross-sectional view of the rotary cutting tool according to the fourth embodiment.

[0018] 1 is a schematic perspective view of a rotary cutting tool 100 according to one embodiment of the present invention. In the rotary cutting tool 100 of this embodiment, a holder 10, which is attached to an apparatus and rotates about a central axis OL1, and an insert 20, which has a cutting edge 25 formed on its outer peripheral surface and is attached to the holder 10, are configured as separate, detachable components. Therefore, even if the cutting edge 25 is damaged due to its lifespan or the like, the damaged insert 20 can be removed and replaced with a new insert 20, eliminating the need to replace the holder 10. This allows the cost of the rotary cutting tool 100 to be reduced.

[0019] As shown in Fig. 1, the rotary cutting tool 100 of this embodiment includes an insert 20 having a cutting edge 25 formed at one end in the axial direction of a central axis OL1, a holder 10 having an elongated shape along the central axis OL1, a bolt 30 that fixes the insert 20 to the holder 10 by bolt tightening, and a cylindrical pin 40. In Fig. 1, the holder 10, the insert 20, and the bolt 30 are fixed so that the central axes of the holder 10, the insert 20, and the bolt 30 all overlap the central axis OL1. Hereinafter, the side of the holder 10 along the central axis OL1 will also be referred to as the base end side, and the side of the insert 10 along the central axis OL1 will also be referred to as the tip end side.

[0020] Fig. 2 is a schematic exploded perspective view of the rotary cutting tool 100. As shown in Fig. 2, the insert 20 has, in addition to the cutting edge 25, a protrusion 21 that protrudes along the central axis OL1 on the base end side, and a through-hole 24 that penetrates the insert 20 along the central axis OL1. The cutting edge 25 has a bottom cutting edge 25b formed on the end face on the tip side of the insert 20, and a peripheral cutting edge 25o formed on the outer peripheral side surface on the tip side. Note that the rotary cutting tool 100 of this embodiment is an end mill that rotates about the central axis OL1.

[0021] FIG. 3 is a schematic cross-sectional view of the rotary cutting tool 100. FIG. 3 shows a longitudinal cross section passing through the central axis OL1 and parallel to the central axis OL1. The protrusion 21 has a tapered surface 21A formed at the tip end as a part of a conical surface having the central axis OL1 as its axis, a bottom surface 21B formed at the base end as a part of the central axis OL1, and a notch 21C formed in a part of the tapered surface 21A. The tapered surface 21A is a conical surface in which the outer diameter of the protrusion 21 decreases from the tip end toward the base end along the central axis OL1. The tapered surface 21A is formed by machining based on the central axis of the insert (the same axis as the central axis OL1 in FIGS. 1 to 3 ). The notch 21C is a surface obtained by cutting out a part of the tapered surface 21A along an axis perpendicular to the radial direction of the bottom surface 21B. Details of the notch 21C will be described later together with the pin 40.

[0022] As shown in FIG. 3 , the through hole 24 formed in the insert 20 has a base-side hole 24A formed on the base end side along the central axis OL1, and a tip-side hole 24B connected to the base-side hole 24A and formed on the tip end side along the central axis OL1. The base-side hole 24A and the tip-side hole 24B are holes with circular cross sections of different inner diameters extending along the central axis OL1. The inner diameter of the base-side hole 24A is smaller than the inner diameter of the tip-side hole 24B. Therefore, as shown in FIG. 3 , a step (engagement surface) ST is formed at the position where the inner diameters of the base-side hole 24A and the tip-side hole 24B change. The inner diameter of the base-side hole 24A is larger than the inner diameter of the cross section of the male thread portion 31 of the bolt 30 and smaller than the inner diameter of the cross section of the head 32 of the bolt 30. The inner diameter of the tip side hole 24B is larger than the inner diameter of the cross section of the male thread portion 31 and the inner diameter of the cross section of the head 32. Therefore, the position of the head 32 of the bolt 30 inserted from the tip side of the through hole 24 along the central axis OL1 is restricted by the step ST. Furthermore, the length of the tip side hole 24B along the central axis OL1 is formed so that the tip side end face of the bolt 30 is located closer to the base end than the tip side end face of the insert 20 when the bolt 30 fixes the insert 20 to the holder 10.

[0023] As shown in Fig. 2, the holder 10 is a member having a circular cross section perpendicular to the central axis OL1. A recess 11 is formed at the tip end of the holder 10, recessed along the central axis OL1. A cylindrical pin hole 15 is formed in the holder 10, perpendicular to the central axis OL1 and penetrating along a central axis OL2. The central axis OL2 is an axis perpendicular to the radial direction of the cross section of the holder 10. A pin 40 is inserted into the pin hole 15. Note that the pin 40 inserted into the pin hole 15 is not shown in Fig. 2.

[0024] As shown in FIG. 3, the recess 11 is formed by a tapered seating surface 12, a bottom surface 14, and a female thread portion 13. The tapered seating surface 12 is part of a conical surface formed on the tip side of the recess 11 and having a central axis OL1 as its axis. The tapered seating surface 12 has an inner diameter that increases from the base end side to the tip side along the central axis OL1. The tapered seating surface 12 is formed by machining based on the central axis of the holder 10 (the same axis as the central axis OL1 in FIGS. 1 to 3). The bottom surface 14 is a circular flat surface that connects to the base end side of the tapered seating surface 12 and is perpendicular to the central axis OL1.

[0025] As shown in FIG. 3 , the inner diameter of the tip side of the tapered bearing surface 12 is larger than the inner diameter of the bottom surface 21B on the base end side of the convex portion 21 of the insert 20 and smaller than the inner diameter of the tip side of the tapered surface 21A of the convex portion 21. Furthermore, the inner diameter of the bottom surface 14 of the recess 11 is smaller than the inner diameter of the bottom surface 21B of the convex portion 21. Therefore, at least a portion of the convex portion 21 is accommodated in a concave-shaped accommodation portion formed by the tapered bearing surface 12 and the bottom surface 14, and the bottom surface 21B of the convex portion 21 does not contact the bottom surface 14 of the recess 11. Note that, as shown in FIG. 3 , portions of the tapered bearing surface 12 and the bottom surface 14 are machined into pin holes 15. In this embodiment, in a vertical cross section of the holder 10 including the central axis OL1, the angle formed by the tapered bearing surface 12 and the central axis OL1 is 30 degrees. The angle formed by the tapered surface 21A of the insert 20 and the central axis OL1 is 30 degrees, the same as the angle formed by the tapered seating surface of the holder 10.

[0026] 3, the female thread portion 13 is formed in the center portion of the bottom surface 14 so as to extend toward the base end along the central axis OL1. In other words, the female thread portion 13 is formed closer to the base end than the tapered seat surface 12 and the bottom surface 14. The open end on the tip side of the female thread portion 13 is connected to the base end side of the bottom surface 14.

[0027] The pin 40 inserted into the pin hole 15 of the holder 10 has a cross section that is shorter than the overall length of the pin hole 15 and has an outer diameter slightly smaller than the inner diameter of the pin hole 15. The longitudinal cross section shown in FIG. 3 is a cross section perpendicular to the central axis OL2 of the pin hole 15. As shown in FIG. 3, when the pin 40 is inserted into the pin hole 15 and the insert 20 is fixed to the holder 10, the tip-most portion of the cylindrical side surface of the pin 40 is located further forward than the bottom surface 21B of the insert 20. In the state shown in FIG. 3, the notch 21C formed in the insert 20 prevents contact between the protrusion 21 of the insert 20 and the pin 40. However, when the insert 20 rotates around the central axis OL1 relative to the holder 10 from the state shown in FIG. 3, the notch 21C of the protrusion 21 contacts the pin 40. When the tapered surface 21C contacts the pin 40, the relative rotation of the insert is restricted by this contact. That is, the pin 40 inserted into the pin hole 15 formed in the holder 10 functions as an anti-rotation mechanism that restricts the rotation of the insert 20 fixed to the holder 10 relative to the central axis OL1 with respect to the holder 10.

[0028] To secure the insert 20 to the holder 10 from the state shown in FIG. 2 where the insert 20 is not secured, first, the bolt 30 is inserted into the through-hole 24 from the tip side, where the cutting edge 25 of the insert 20 is formed. The male thread portion 31 of the bolt 30, which has been inserted into the through-hole 24 and protrudes from the base end side of the through-hole 24, is inserted into the female thread portion 13 of the recess 11 of the holder 10. When the inserted bolt 30 is rotated around the central axis OL1 in the tightening direction, the insert 20 together with the bolt 30 moves along the central axis OL1 toward the base end side approaching the holder 10. When the bolt 30 and the insert 20 move a certain amount, the tapered surface 21A of the protrusion 21 of the insert 20 begins to contact the tapered seating surface 12 of the recess 11 of the holder 10. When the bolt is further turned in the tightening direction, contact between the tapered seating surface 12 of the recess 11 and the tapered surface 21A of the protrusion 21 aligns the central axis of the holder in which the recess 11 is formed with the central axis of the insert 20 in which the protrusion 21 is formed. After the insert 20 is fixed to the holder 10 to a position where it will not move, a pin 40 is inserted into the pin hole 15 of the holder 10, thereby restricting rotation of the insert 20 fixed to the holder 10 about the central axis OL1. To remove the insert 20 fixed to the holder 10, the bolt 30 is rotated in the loosening direction about the central axis OL1.

[0029] As described above, in the rotary cutting tool 100 of this embodiment, the insert 20 includes a protrusion 21 protruding from the base end along the central axis OL1 and a through-hole 24 penetrating the insert 20 along the central axis OL1. The tapered surface 21A formed on the protrusion 21 is a conical surface whose outer diameter decreases from the tip end toward the base end along the central axis OL1. The holder 10 to which the insert 20 is fixed has a recess 11 recessed along the central axis OL1 at the tip end. The tapered seating surface 12 formed in the recess 11 has an inner diameter that increases from the base end toward the tip end along the central axis OL1. Therefore, at least a portion of the protrusion 21 is accommodated in a concave-shaped accommodation portion formed by the tapered seating surface 12 and the bottom surface 14. The female thread portion 13 is formed closer to the base end than the tapered seating surface 12 and the bottom surface 14. In the rotary cutting tool 100 of this embodiment, a bolt 30 is inserted into the through-hole 24 of the insert 20, and the male thread portion 31 of the inserted bolt 30 threads into the female thread portion 13 of the holder 10, thereby securing the insert 20 to the holder 10. In other words, because the holder 10 and the insert 20 are formed separately, if the cutting edge 25 of the insert 20 is damaged, only the insert 20 needs to be replaced, without having to replace the entire rotary cutting tool 100, including the holder 10. In particular, in this embodiment, centerless machining, which is performed on the holder 10 when the holder 10 and the insert 20 are integrated, does not need to be performed when replacing the insert 20. Furthermore, because the insert 20 can be replaced while the holder 10 remains attached to the device that rotates the rotary cutting tool 100, the time required to adjust the origin of the rotary cutting tool 100 relative to the device can be reduced. As a result, the cost of the rotary cutting tool 100 and the manufacturing costs of the parts cut by the rotary cutting tool 100 can be reduced. Furthermore, when the male thread portion 31 and the female thread portion 13 are fastened together, the tapered seating surface 12 formed in the housing portion of the holder 10 comes into contact with the tapered surface 21A formed on the convex portion 21 of the insert 20. When the bolt 30 is rotated in the tightening direction after contact, the holder 10 and the insert 20 approach each other along the central axis OL1, and the contact between the tapered seating surface 12 and the tapered surface 21A aligns the central axes of the two.In this embodiment, the tapered seating surface 12 formed on the holder 10 and the tapered surface 21A formed on the insert 20 do not have complex shapes, which simplifies the machining of the recess 11 of the holder 10 and the machining of the protrusion 21 of the insert 20. Furthermore, because positioning is achieved by the engagement between the tapered seating surface 12 and the tapered surface 21A, misalignment of the insert 20 with respect to the holder 10 can be suppressed.

[0030] Furthermore, in the present embodiment, in a vertical cross section of the holder 10 including the central axis OL1, the angle formed between the tapered bearing surface 12 and the central axis OL1 is 30 degrees. In the present embodiment, because the angle formed between the tapered bearing surface 12 and the central axis OL1 of the holder 10 is 30 degrees, the thickness of the portion of the holder 10 where the recess 11 is formed does not become too thin, and a decrease in the rigidity of the holder 10 can be suppressed. Furthermore, because the angle formed between the tapered bearing surface 12 and the central axis OL1 of the holder 10 is 60 degrees or less, misalignment of the insert 20 with respect to the holder 10 during fastening can be suppressed, and the insert 20 can be prevented from being fixed at an angle with respect to the holder 10.

[0031] In addition, in this embodiment, the pin 40 inserted into the pin hole 15 formed in the holder 10 functions as an anti-rotation mechanism that restricts the rotation of the insert 20 fixed to the holder 10 relative to the central axis OL1 with respect to the holder 10. In other words, since the fixed insert 20 is prevented from rotating around the central axis OL1 with respect to the holder 10, the rotary cutting tool 100 can fully function as a tool.

[0032] Furthermore, in the insert 20 of this embodiment, a step ST is formed at a position where the inner diameter of the base-side hole 24A and the inner diameter of the tip-side hole 24B of the through hole 24 change. Therefore, the head 32 of the bolt 30 inserted into the through hole 24 can be caught on the step ST. This allows the position of the bolt 30 along the central axis OL1 relative to the insert 20 to be regulated.

[0033] Second Embodiment Fig. 4 is a schematic exploded perspective view of a holder 10a and an insert 20a according to a second embodiment. Fig. 5 is a schematic cross-sectional view of a rotary cutting tool 100a according to the second embodiment. The rotary cutting tool 100a according to the second embodiment has a different anti-rotation mechanism for the insert 20a compared to the rotary cutting tool 100 according to the first embodiment. Therefore, in the second embodiment, the anti-rotation mechanism different from that of the first embodiment will be described, and a description of the same configuration as that of the first embodiment will be omitted.

[0034] As shown in FIG. 4, the holder 10a of the second embodiment is formed with a pin hole 15a along the central axis OL2a, which is aligned radially of the cross section of the central axis OL1. FIG. 5 shows a longitudinal cross section parallel to both the central axis OL1 and the central axis OL2a. As shown in FIGS. 4 and 5, unlike the pin hole 15 of the first embodiment, the pin hole 15a does not penetrate the entire holder 10a along the cross section of the holder 10a. The pin hole 15a removes a portion of the tapered seat surface 12a and the bottom surface 14a that form the recess 11a. The pin 40a has a circular cross section slightly smaller than the pin hole 15a and, as shown in FIG. 5, has a cylindrical shape extending along the central axis OL2a.

[0035] As shown in Figures 4 and 5, a notch 21Ca is formed in the protrusion 21a. As shown in Figure 5, the notch 21Ca is formed in a position where the protrusion 21a does not contact the pin 40a when the pin 40a is inserted into the pin hole 15a and the insert 20a is fixed to the holder 10a. As in the first embodiment, the tip-most portion of the cylindrical side surface of the pin 40a is located more distal than the bottom surface 21Ba of the insert 20a. Therefore, when the insert 20a rotates around the central axis OL1 relative to the holder 10a, the notch 21Ca in the protrusion 21a contacts the pin 40a. In other words, the pin 40a inserted into the pin hole 15a formed in the holder 10a functions as a rotation prevention mechanism.

[0036] Third Embodiment Fig. 6 is a schematic exploded perspective view of a holder 10b and an insert 20b according to a third embodiment. Fig. 7 is an enlarged perspective view of a recess 11b of a holder 10b according to the third embodiment. Fig. 8 is a schematic cross-sectional view of a rotary cutting tool 100b according to the third embodiment. The rotary cutting tool 100b according to the third embodiment has a different anti-rotation mechanism for the insert 20b compared to the rotary cutting tool 100 according to the first embodiment and the rotary cutting tool 100a according to the second embodiment. Therefore, in the third embodiment, a description will be given of an anti-rotation mechanism that is different from that of the first and second embodiments, and a description of the same configuration as that of the first and second embodiments will be omitted.

[0037] Fig. 7 shows a schematic enlarged perspective view of the recess 11b shown in Fig. 6. As shown in Fig. 7, the holder 10b of the third embodiment has an end surface 17 that connects the recess 11b to the outer circumferential surface of the holder 10b. The end surface 17 has a shape in which the hollow portion of the recess 11b is hollowed out with respect to a circle perpendicular to the central axis OL1. The end surface 17 is located at the tip end of the holder 10b.

[0038] As shown in Fig. 7, a protrusion 16 that protrudes toward the radial center is formed on a portion of the tapered seating surface 12b that forms the recess 11b. The protrusion 16 has a protruding surface 16c that protrudes toward the radial center from the end face 17 along a cross section parallel to the end face 17, and a sloped surface 16s that connects to the protruding surface 16c. As shown in Fig. 8, the sloped surface 16s is a slope that slopes toward the center as it moves from the connected protruding surface 16c toward the base end. The sloped surface 16s connects to the open end face of the female thread portion 13.

[0039] As shown in Fig. 8, a notch 21Cb is formed in a portion of the protruding portion 21b of the insert 20b by cutting out a portion of the tapered surface 21Ab. As shown in Fig. 8, the notch 21Cb is a slope formed to engage with the slope 16s of the protruding portion 16 when the insert 20b is fixed to the holder 10b. Specifically, the notch 21Cb is a slope that approaches the center as it approaches the base end. Furthermore, the angle formed by the slope of the notch 21C and the central axis OL1 is the same as the angle formed by the slope 16s of the holder 10b and the central axis OL1.

[0040] 8, the protrusion 16 in the recess 11b of the holder 10b protrudes radially toward the center beyond the tapered seating surface 12b and the tapered surface 21Ab of the protrusion 21b of the insert 20b. Therefore, when the insert 20b rotates around the central axis OL1 relative to the holder 10b, the protrusion 16 comes into contact with the tapered surface 21Cb. In other words, the protrusion 16 formed in the recess 11b of the holder 10b functions as a rotation prevention mechanism.

[0041] <Fourth embodiment> Figure 9 is a schematic exploded perspective view of a holder 10c and an insert 20c of a fourth embodiment. Figure 10 is a schematic cross-sectional view of a rotary cutting tool 100c of the fourth embodiment. The rotary cutting tool 100c of the fourth embodiment has a different anti-rotation mechanism for the insert 20c compared to the rotary cutting tools 100 of the first embodiment to the rotary cutting tool 100b of the third embodiment. Therefore, in the fourth embodiment, the anti-rotation mechanism that differs from that of the first to third embodiments will be described, and a description of the same configuration as that of the first to third embodiments will be omitted.

[0042] 9, the holder 10c of the fourth embodiment has an end face 17 that connects the recess 11c and the outer circumferential surface of the holder 10c. The end face 17 has a shape in which the hollow portion of the recess 11c is hollowed out with respect to a circle perpendicular to the central axis OL1. The end face 17 is located at the tip end of the holder 10c.

[0043] As shown in FIG. 10 , a portion of the tapered seating surface 12c forming the recess 11c has an insertion hole 18 extending from the distal end toward the proximal end in a direction parallel to the rotation axis OL1. The insertion hole 18 and the through-hole 24 are separated by a partition wall. A locking pin 50 is inserted (press-fitted) into the insertion hole 18 and protrudes from the insertion hole 18 onto the tapered seating surface 12c. While the insertion hole 18 and the locking pin 50 preferably have circular cross sections as shown in this embodiment, the present invention is not limited to this cross-sectional shape and also encompasses polygonal shapes. In addition, in this embodiment, the insertion hole 18 penetrates the holder 10c from the distal end toward the proximal end. However, this is merely an example of the preferred embodiment, and the insertion hole 18 need not necessarily be a through hole. It is sufficient for the locking pin (described later) to be inserted therein. Therefore, the insertion hole 18 may be a blind hole.

[0044] As shown in Fig. 10, a groove 21Cc is formed in a part of the protruding portion 21c of the insert 20c by cutting out a part of the tapered surface 21Ac in a square shape. As shown in Fig. 9, the groove 21Cc is an engagement groove formed to engage with the anti-rotation pin 50 inserted into the insertion hole 18 when the insert 20c is fixed to the holder 10c. Specifically, the notch 21Cc is formed by boring out a part of the protruding portion 21c of the insert 20c toward the through-hole 24.

[0045] 10 , the anti-rotation pin 50 inserted into the insertion hole 18 in the recess 11c of the holder 10c protrudes radially toward the center beyond the tapered seating surface 12c and the tapered surface 21Ac of the protrusion 21c of the insert 20c. Therefore, when the insert 20c rotates around the central axis OL1 relative to the holder 10c, the anti-rotation pin 50 contacts the groove 21Cc in the tapered surface 21c. In other words, the tip 50c of the pin 50 formed in the recess 11c of the holder 10c (the portion protruding beyond the tapered seating surface 12c) functions as an anti-rotation mechanism.

[0046] According to the anti-rotation mechanism of this embodiment, the anti-rotation pin 50 is pressed into the holder 10c perpendicularly, i.e., parallel to the rotation axis OL1, so that even if a load is applied to the anti-rotation pin 50 due to the rotation of the tool during use, the anti-rotation pin 50 will not come out and can still serve to prevent the insert 20c from rotating during use.

[0047] Furthermore, by forming a groove 21Cc in the tapered surface 21c with which the tip 50c of the anti-rotation pin 50 contacts, the sides of the tip 50c of the anti-rotation pin 50 can be held by both side walls of the groove 21Cc even when a rotational force, i.e., a lateral force relative to the axial direction of the anti-rotation pin 50, is applied to the tip 50c. This can also be achieved by using the notch 21C or the like shown in other embodiments. However, in this case, if a lateral force relative to the axial direction of the anti-rotation pin 50 is applied, when a force is applied in the rotational direction of the insert 20c, the tip 50c of the anti-rotation pin 50 generates an oblique force, which causes the insert 20c to lift up and tilt. Therefore, the groove configuration shown in this embodiment is the optimal embodiment.

[0048] In the present embodiment, the holder 10c has a step 10ca formed on its peripheral surface closer to the tip than the base end, and a narrow-diameter portion 10cb, where the diameter of the holder 10c is narrower, is formed at the tip end of the step 10ca. By forming this narrow-diameter portion 10cb, the outer shape of the holder 10c becomes thinner relative to the outer diameter of the insert 20c, which is effective in preventing the holder 10c from coming into contact with the workpiece during machining. However, if the outer shape of the holder 10, 10a, or 10b shown in the first to third embodiments were simply narrowed to form the narrow-diameter portion 10cb, the thickness of the end of the end face 17 of the holder 10c would be thin, which could reduce the strength required to support the insert 20c during cutting.

[0049] Therefore, in order to ensure the wall thickness, it is possible to reduce the size of the tapered surface, but in this case, since the same size insert as in the first to third embodiments is used in this embodiment, the size of the tapered surface becomes smaller than the size of the insert 20c, so there is a concern that the insert 20c will float up, and it is not possible to ensure a sufficient contact area between the holder and the insert. In this case, in order to ensure the contact area between the holder and the insert, it is necessary to reduce the taper size on the insert side, but reducing the size of the entire insert leads to a shortening of the cutting edge on the side of the insert, which restricts the cutting depth during cutting.

[0050] Therefore, in this embodiment, as shown in Figures 9 and 10, a step 21Dc is formed between the convex portion 21c of the insert 20c and the cutting edge, making it a stepped insert, which allows the size of the tapered surface 21Ac to be reduced while also ensuring the cutting edge length on the side, thereby making it possible to ensure both the contact area between the holder 10c and the insert 20c and the cutting edge length.

[0051] <Modifications of this embodiment> The present invention is not limited to the above-described embodiment, and can be implemented in various forms without departing from the spirit of the present invention. For example, the following modifications are also possible.

[0052] In the first embodiment, the rotary cutting tool 100 is described as including a holder 10 having a recess 11 formed therein, an insert 20 having a protrusion 21 at least partially received in the recess 11, and a bolt 30 inserted through a through-hole 24 of the insert 20 and threadedly engaging with the female thread portion 13 of the holder 10. However, the configuration of the rotary cutting tool 100 can be modified. For example, the rotary cutting tool 100 may be configured only with the holder 10 and the insert 20, without including the bolt 30 and the pin 40. The rotary cutting tool 100 may be a tool other than an end mill, such as a reamer or a cutter. The cutting edge 25 may have at least one of a peripheral cutting edge 25o and a bottom cutting edge 25b. Alternatively, the holder 10 or the insert 20 alone may be distributed as a component of the rotary cutting tool 100.

[0053] In the first embodiment, the angles formed by the tapered bearing surface 12 of the holder 10 and the tapered surface 21A of the insert 20 with respect to the central axis of each component were 30 degrees. However, the angles may be less than 30 degrees or greater than 30 degrees. The angle formed by the tapered bearing surface 12 and the central axis is preferably 30 degrees or greater to suppress a decrease in the rigidity of the holder 10. Furthermore, the angle formed by the tapered bearing surface 12 and the central axis is preferably 60 degrees or less to stabilize the edge runout (inclination) of the cutting edge 25 of the insert 20 fixed to the holder 10. The anti-rotation mechanisms in each of the first to third embodiments are merely examples, and well-known configurations may be used. For convenience, in each of the first to third embodiments, the central axis of the holder 10 and the central axis of the insert 20 are described as overlapping the central axis OL1 and being the same axis.

[0054] In the first embodiment described above, the step ST formed at the position where the inner diameters of the base-side hole 24A and the tip-side hole 24B of the through hole 24 change restricts the position along the central axis OL1 of the head 32 of the bolt 30 inserted through the through hole 24. However, the shape of the engagement surface that engages with the head 32 of the bolt 30 to restrict the position of the bolt 30 may be a shape other than the step ST and can be modified. For example, the inner diameter of the base-side hole 24A may be a tapered surface formed by gradually decreasing toward the open end surface of the tip-side hole 24B.

[0055] This aspect has been described above based on embodiments and modifications. However, the above-described embodiments are intended to facilitate understanding of this aspect and are not intended to limit this aspect. This aspect may be modified or improved without departing from the spirit and scope of the claims, and equivalents thereof are included in this aspect. Furthermore, if a technical feature is not described as essential in this specification, it may be deleted as appropriate.

[0056] 10, 10a, 10b... Holder 10ca... Step portion 10cb... Thin diameter portion 11, 11a, 11b... Recess 12, 12a, 12b... Tapered seat surface 13... Female thread portion 14, 14a... Bottom surface of recess 15, 15a... Pin hole 16... Protrusion 16c... Protruding surface 16s... Slope 17... End surface 18... Insertion hole 20, 20a, 20b, 20c... Insert 21, 21a, 21b, 21c... Protrusion 21A, 21Aa, 21Ab, 21Ac... Tapered surface 21B, 21Ba, 21Bb, 21Bc... Bottom surface of protrusion 21C, 21Ca, 21cb... Notch 21Cc... Groove 21Dc... Step portion 24... Through hole 24A...Base end side hole 24B...Tip side hole 25...Cutting edge 25b...Bottom edge 25o...Peripheral edge 30...Bolt 31...Male thread portion 32...Head 40, 40a...Pin 50...Anti-rotation pin 50c...Tip portion 100, 100a, 100b...Rotary cutting tool OL1...Center axis of rotary cutting tool OL2, OL2a...Center axis of pin hole ST...Step (engagement surface)

Claims

1. A rotary cutting tool comprising a holder and an insert fixed to the holder, The insert is a cutting edge formed on at least one of one end and a side surface of the insert in the axial direction; a protrusion formed at the other end of the insert in the axial direction and protruding along the axial direction of the insert; a through hole passing through the insert along the axial direction of the insert, the protrusion has a conical tapered surface such that the outer diameter of the protrusion decreases from the one end side of the insert toward the other end side, the holder has an elongated shape, and a recess is formed at one end to which the insert is fixed, the recess being recessed along the axial direction of the holder; The recessed portion is a recessed receiving portion into which the protrusion of the insert is received, the receiving portion having a conical tapered seat surface formed therein such that the inner diameter of the receiving portion increases from the other end side of the holder toward the one end side; a female screw portion located closer to the other end of the holder than the accommodation portion, formed along the axial direction of the holder, and having an open end formed in the accommodation portion; a bolt that is inserted into the through hole and threadedly engaged with the female screw portion to fix the insert to the holder; a rotation prevention mechanism that prevents the insert from rotating relative to the holder around the axis of the holder, The anti-rotation mechanism includes an insertion hole formed in a tapered surface forming the recess of the holder, from the tip end side toward the base end side, parallel to the axial direction; an anti-rotation pin inserted into the insertion hole and protruding from the insertion hole toward the tapered surface; and a groove formed in the tapered surface of the insert so that the anti-rotation pin can engage with the insertion hole; and when the insert is fixed to the holder, the anti-rotation pin inserted into the insertion hole engages with the groove. A rotary cutting tool characterized by:

2. 2. The rotary cutting tool of claim 1, In a vertical cross section of the holder including the axis of the holder, the angle formed between the tapered seat surface and the axis of the holder is 30 degrees or more and 60 degrees or less. A rotary cutting tool characterized by:

3. (delete)

4. 2. The rotary cutting tool of claim 1, The through hole has an inner diameter on the one end side of the insert that is larger than the inner diameter on the other end side, and an engagement surface is formed at a position where the inner diameters change. A rotary cutting tool characterized by:

5. 3. The rotary cutting tool according to claim 1 or 2, A rotary cutting tool characterized in that it is an end mill having the cutting edge.

6. An insert that is fixed to a holder of a rotary cutting tool and used, a cutting edge formed on at least one of one end and a side surface of the insert in the axial direction; a protrusion formed at the other end of the insert in the axial direction and protruding along the axial direction of the insert; a through hole passing through the insert along the axial direction of the insert, the protrusion has a conical tapered surface such that the outer diameter of the protrusion decreases from the one end side of the insert toward the other end side, The insert may further include a rotation prevention mechanism that prevents the insert from rotating relative to the holder around an axis when the insert is fixed to the holder, the anti-rotation mechanism has a groove on the tapered surface, and when the insert is fixed to the holder, a pin engages with the groove to restrict rotation; An insert characterized by:

7. A holder used in a rotary cutting tool for fixing an insert, comprising: The holder has an elongated shape, and a recess is formed in at least one of the end portion and the side surface to which the insert is fixed, the recess being recessed along the axial direction of the holder, The recessed portion is a recessed receiving portion in which at least a portion of the insert is received, the receiving portion having a conical tapered seat surface formed therein such that the inner diameter increases from the other end side of the holder toward the one end side; a female screw portion located closer to the other end of the holder than the accommodation portion, formed along the axial direction of the holder, and having an open end formed in the accommodation portion; The insert may further include a rotation prevention mechanism that prevents the insert from rotating relative to the holder around an axis when the insert is fixed to the holder, The anti-rotation mechanism includes an insertion hole formed in a tapered surface that forms the recess of the holder, from the tip end side toward the base end side, parallel to the axial direction, and an anti-rotation pin that is inserted into the insertion hole and protrudes from the insertion hole toward the tapered surface side, and when the insert is fixed to the holder, the anti-rotation pin inserted into the insertion hole engages with the insert to restrict rotation. A holder characterized by: