Collet

Abstract

To provide a collet which can inhibit vibration of a cutting tool.SOLUTION: A collet 30 is held with a cutting tool T which rotates around an axis AX coaxially with the axis AX by a holder body. The collet 30 includes: a cylindrical holding part 32 which houses a part of the cutting tool T and is held with the holder body by the outer peripheral surface 321G being fastened; a fitting hole 32H in which a fixing member 60 disposed between the cutting tool T and the holding part 32 to fix the cutting tool T to the holding part 32 is fitted; and a hole facing part 331 which is recessed to the radial inner side DR1 from the outer peripheral surface 321G and disposed at a position where the hole facing part 331 is point symmetrical to the fitting hole 32H with respect to the axis AX. When viewed along the radial direction DR of the holding part 32, the area of the hole facing part 331 is larger than or equal to the area of the fitting hole 32H.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a collet. [Background technology]

[0002] As various techniques relating to structures for holding cutting tools, for example, Patent Document 1 discloses an end mill adapter for mounting a cutting tool to a milling machine, drilling machine, etc. The end mill adapter includes a tapered shank mounted to a milling machine, drilling machine, etc., a collet that houses the shank of a cutting tool (an end mill in Patent Document 1) inside, a notch formed in the shank of the cutting tool and a wedge disposed between a wedge aperture formed in the collet, and a lock nut that radially compresses the collet, and the collet with the wedge disposed between the notch and the wedge aperture is tightened with the lock nut, thereby restraining the cutting tool from rotating relative to the collet. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 9-500336 Summary of the Invention [Problem to be solved by the invention]

[0004] As disclosed in Patent Document 1, a collet having a hole in which a wedge is placed between the collet and a cutting tool has the problem that when it is tightened with a lock nut, the tightening force causes the collet to deform, resulting in vibration of the cutting tool.

[0005] For these reasons, a collet capable of suppressing runout of a cutting tool is desired. [Means for solving the problem]

[0006] The collet of the present invention is characterized in that it is a collet that is held by a holder body coaxially with a cutting tool that rotates around an axis, and comprises a cylindrical holding portion that accommodates a part of the cutting tool and is held in the holder body by tightening its outer peripheral surface, a fitting hole into which a fixing member that is placed between the cutting tool and the holding portion to fix the cutting tool to the holding portion is fitted, and a hole opposing portion that is recessed radially inward from the outer peripheral surface and is positioned in a position that is point-symmetrical with respect to the fitting hole about the axis, and when viewed radially along the holding portion, the area of ​​the hole opposing portion is greater than or equal to the area of ​​the fitting hole.

[0007] According to this configuration, the tightening force acting on the hole-facing portion can be reduced, which improves the balance of the tightening forces acting on the fitting hole and the hole-facing portion, thereby suppressing deformation of the collet and suppressing runout of the cutting tool.

[0008] As another feature, a length of the hole opposing portion in a direction along the axis may be equal to or greater than a length of the fitting hole in a direction along the axis.

[0009] According to this configuration, since the length of the hole-facing portion in the direction along the axis is greater than or equal to the length of the mating hole in the direction along the axis, for example, it is possible to suppress bending around the mating hole.

[0010] As another feature, the bearing may further include a hole containing portion recessed toward the inside in the radial direction and disposed so as to contain the fitting hole.

[0011] According to this configuration, since the hole containing portion is disposed so as to include the fitting hole, the tightening force acting on the fitting hole can be further reduced. This further improves the balance of the tightening forces acting on the fitting hole and the hole facing portion, thereby further suppressing deformation around the fitting hole and effectively suppressing deformation of the collet.

[0012] As another feature, the hole facing portion and the hole containing portion may be connected in a circumferential direction of the holding portion to form one recess.

[0013] According to this configuration, the hole-facing portion and the hole-containing portion are connected in the circumferential direction to form a single recess, so that the balance of the fastening force acting on the collet in the circumferential direction including the fitting hole can be further improved. As a result, deformation around the fitting hole can be further suppressed, and deformation of the collet can be further suppressed. In addition, since a single recess is formed around the entire circumference of the collet, it is possible to avoid the complication of processing work such as forming the hole-facing portion and the hole-containing portion separately.

[0014] As another feature, the hole facing portion and the hole containing portion may be spaced apart in a circumferential direction of the holding portion.

[0015] According to this configuration, since the hole facing portion and the hole containing portion are arranged to be spaced apart in the circumferential direction, the force acting on the collet can be locally reduced, that is, the fastening force acting on the collet can be dispersed, and deformation of the collet can be effectively suppressed.

[0016] As another feature, a central angle formed by both ends of the hole facing portion in a circumferential direction of the holding portion may be equal to or larger than an angle formed by both ends of the fitting hole in the circumferential direction.

[0017] According to this configuration, the central angle formed by both ends of the hole opposing portion in the circumferential direction is greater than or equal to the angle formed by both ends of the fitting hole in the circumferential direction, thereby further improving the balance of the tightening forces acting on the fitting hole and the hole opposing portion.

[0018] The collet of the present invention is characterized in that it is a collet that is held by a holder body coaxially with a cutting tool that rotates around an axis, and comprises a cylindrical holding portion that accommodates a part of the cutting tool and is held in the holder body by tightening its outer peripheral surface, a fitting hole into which a fixing member that is placed between the cutting tool and the holding portion to fix the cutting tool to the holding portion is fitted, and a gap portion that forms a gap between the holder body and the outer peripheral surface and is positioned in a position that is point-symmetrical with respect to the fitting hole about the axis, and when viewed radially of the holding portion, the area of ​​the gap portion is greater than or equal to the area of ​​the fitting hole.

[0019] According to this configuration, since a gap portion that forms a gap with the outer peripheral surface of the holding portion held by the holder body is provided, the fastening force acting around the gap portion can be reduced. This improves the balance of the fastening forces acting on the fitting hole and the hole facing portion, thereby suppressing deformation of the collet due to the fastening force and suppressing runout of the cutting tool. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is an exploded perspective view showing a tool holder for holding a cutting tool according to a first embodiment. [Diagram 2] 1 is a cross-sectional view showing a tool holder to which a cutting tool according to a first embodiment is attached. [Diagram 3] 1 is a perspective view showing a part of a cutting tool and a collet according to a first embodiment. FIG. [Figure 4] FIG. 2 is a view showing the keyhole side of the collet according to the first embodiment. [Diagram 5] 1 is a cross-sectional view showing a collet according to a first embodiment. [Figure 6] 5 is a plan view showing the opposite side of the collet shown in FIG. 4. [Figure 7] FIG. 11 is a perspective view showing a part of a cutting tool and a collet according to a second embodiment. [Figure 8] FIG. 11 is a view showing the keyhole side of a collet according to the second embodiment. [Figure 9]FIG. 11 is a cross-sectional view showing a collet according to a second embodiment. [Figure 10] 9 is a plan view showing the opposite side of the collet shown in FIG. 8. FIG. [Figure 11] FIG. 11 is a perspective view showing a part of a cutting tool and a collet according to a third embodiment. [Figure 12] FIG. 11 is a view showing the keyhole side of a collet according to a third embodiment. [Figure 13] FIG. 11 is a cross-sectional view showing a collet according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, an embodiment of a tool holder including a collet according to the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiment, and various modifications are possible without departing from the spirit and scope of the present invention.

[0022] [Embodiment 1] [Tool holder] First, the tool holder 100 will be described with reference to Fig. 1. As shown in Fig. 1, the tool holder 100 is used to fix a cutting tool T to a machine tool. The machine tool is a milling machine, a machining center, or the like. The cutting tool T is fixed to the tool holder 100 fixed to the machine tool, and rotates together with the tool holder 100 about an axis AX. Hereinafter, the direction along the axis AX will be referred to as the "axial direction DX".

[0023] The cutting tool T has a cutting portion T1 and a shank portion T2. ​​In this embodiment, the cutting tool T is an end mill.

[0024] The blade portion T1 cuts the cutting target (workpiece). The shank portion T2 is held by the collet 30. The shank portion T2 is a circular columnar shape when viewed along the axial direction DX, and a part of the outer circumferential surface is cut out. Hereinafter, a plane formed by cutting out the outer circumferential surface of the shank portion T2 is referred to as a "cutout surface T3". The cutout surface T3 is a plane including the axial direction DX and a direction perpendicular to the axial direction DX. Hereinafter, in the direction along the axial direction DX, the side of the blade portion T1 when viewed from the shank portion T2 is referred to as the "DX1 side", and the opposite side is referred to as the "DX2 side".

[0025] The tool holder 100 includes a holder body 10, a connecting member 20, a collet 30, a biasing member 40, a fastening member 50, and a key member 60 (an example of a fixing member). The holder body 10, the connecting member 20, the collet 30, the biasing member 40, and the fastening member 50 are arranged in this order from the DX2 side to the DX1 side. The tool holder 100 is arranged on the DX1 side with respect to the machine tool.

[0026] [Holder body] The holder body 10 holds the cutting tool T via the collet 30. The holder body 10 has a circular tubular shape when viewed along the axial direction DX, and has a mounting portion 11 and a chuck portion 12.

[0027] The mounted portion 11 is disposed at the end of the holder body 10 on the DX2 side and is mounted to a machine tool. The mounted portion 11 is tapered in diameter from the DX1 side toward the DX2 side (see FIG. 2).

[0028] The chuck portion 12 is disposed at the end portion on the DX1 side of the holder body 10. The chuck portion 12 has a first housing space 12S capable of housing the collet 30 therein.

[0029] [Connecting member] The connecting member 20 connects the holder body 10 and the collet 30, and prevents the collet 30 from slipping out of the tool holder 100. The connecting member 20 has a first connecting portion 21, a second connecting portion 22, and an intermediate portion 23. The first connecting portion 21, the intermediate portion 23, and the second connecting portion 22 are arranged in this order from the DX2 side toward the DX1 side. The connecting member 20 has a through hole 20H that penetrates the connecting member 20 along the axial direction DX. Both ends of the through hole 20H are formed in a shape (e.g., a hexagon) that can be engaged with a rotation operating tool such as a wrench.

[0030] The first connecting portion 21, the second connecting portion 22, and the intermediate portion 23 are cylindrical with different radii when viewed along the axial direction DX. A male thread is formed on the outer periphery of each of the first connecting portion 21 and the second connecting portion 22.

[0031] For example, the first connection portion 21 of the connecting member 20 that fastens the collet 30 and the second connection portion 22 is inserted into the first accommodation space 12S of the holder body 10, and a rotation operating tool is inserted from the side of the mounted portion 11 of the holder body 10 to fasten the holder body 10 and the first connection portion 21. As a result, the holder body 10 and the collet 30 are connected via the connecting member 20.

[0032] [Colette] As shown in FIG. 1, the collet 30 has a circular cylindrical shape when viewed along the axial direction DX, and is held by the holder body 10 together with the cutting tool T coaxially with respect to the axis AX.

[0033] The collet 30 has a connected portion 31 and a holding portion 32. Hereinafter, the radial direction of the holding portion 32 (collet 30) will be referred to as the "radial direction DR", the inside of the radial direction DR will be referred to as the "radial inner side DR1", and the outside of the radial direction DR will be referred to as the "radial outer side DR2". In addition, the circumferential direction of the holding portion 32 (collet 30) will be referred to as the "circumferential direction DC".

[0034] The connected part 31 is disposed at the end on the DX2 side. The connected part 31 has a connecting wall part 311 and a second accommodation space 31S (see FIG. 2). The connecting wall part 311 divides the inside and the outside of the connected part 31. The second accommodation space 31S is capable of accommodating the second connecting part 22. Note that a collet inner peripheral surface 31N (see FIG. 2) of the connecting wall part 311 is formed with a female thread into which the second connecting part 22 is screwed, as described above.

[0035] The holding portion 32 is disposed at the end of the collet 30 on the DX1 side. The holding portion 32 has a holding wall portion 321 and a third housing space 32S. The holding wall portion 321 divides the inside and the outside of the holding portion 32. The third housing space 32S is capable of housing at least a part of the shank portion T2 of the cutting tool T and the biasing member 40.

[0036] The retaining wall 321 is formed with a key hole 32H (an example of a fitting hole) and a plurality of slits 32G. The key member 60 fits into the key hole 32H. Each of the plurality of slits 32G extends along the axial direction DX. In this embodiment, there are three slits 32G, and the three slits 32G are arranged at intervals of 120 degrees around the axial center AX. One of the three slits 32G communicates with the key hole 32H and functions as a guide groove 30M that guides the key member 60 to the key hole 32H. The key hole 32H and the slit 32G penetrate the retaining wall 321 along a radial direction DR that is perpendicular to the axial direction DX.

[0037] 2, when the collet 30 is held by the holder body 10, the outer peripheral surface 321G comes into contact with the chuck inner peripheral surface 12N of the chuck portion 12 of the holder body 10. More specifically, the outer peripheral surface 321G is pressed (fastened) toward the radially inward direction DR1 by the chuck inner peripheral surface 12N.

[0038] [Using member] The biasing member 40 is disposed on the DX2 side with respect to the shank portion T2 of the cutting tool T in the third housing space 32S, and biases the cutting tool T toward the DX1 side. In this embodiment, the biasing member 40 is a compression coil spring.

[0039] [Fastening member] The fastening member 50 is a circular cylindrical (ring-shaped) member centered on the axis AX, and applies a fastening force to the chuck portion 12. The fastening member 50 is held rotatably by a specified angle with respect to the holder body 10. As shown in FIG. 1, the fastening member 50 has a fourth accommodation space 50S, a fastening wall portion 51, and a plurality of needle rollers 52 (see FIG. 2). As shown in FIG. 2, the fourth accommodation space 50S is capable of accommodating the chuck portion 12 of the holder body 10. In addition, the fastening wall portion 51 divides the inside from the outside. The plurality of needle rollers 52 are arranged on a fastening inner peripheral surface 51N of the fastening wall portion 51.

[0040] The needle rollers 52 are configured to be spirally oriented around the axis AX. Therefore, when the needle rollers 52 (fastening members 50) rotate around the axis AX, they revolve around the axis AX while rotating along the chuck outer circumferential surface 12G of the chuck portion 12. For example, when the needle rollers 52 (fastening members 50) rotate in a first direction (e.g., clockwise when viewed from the DX1 side to the DX2 side), a fastening force acts on the chuck portion 12. As a result, the cutting tool T is fixed via the collet 30 inserted in the chuck portion 12. On the other hand, when the needle rollers 52 (fastening members 50) rotate in a second direction opposite to the first direction (e.g., counterclockwise when viewed from the DX1 side to the DX2 side), the fastening force on the chuck portion 12 is released. As a result, the fixing of the cutting tool T (collet 30 inserted in the chuck portion 12) is released.

[0041] [Key member] The key member 60 prevents the cutting tool T from slipping out of the collet 30. The key member 60 also prevents the cutting tool T from rotating relative to the collet 30. The key member 60 has a base 61 and a protruding portion 62. The base 61 includes a flat surface (hereinafter referred to as a "base surface 61S") parallel to the cutout surface T3. The protruding portion 62 protrudes in a direction perpendicular to the base surface 61S.

[0042] [How to install the tool holder] Hereinafter, a method of assembling the tool holder 100 will be described with reference to FIGS. 1 to 3. The worker assembles the tool holder 100 in the following procedure. First, the second connecting portion 22 of the connecting member 20 is fastened to the connected portion 31 of the collet 30. Next, the collet 30 to which the connecting member 20 is fastened is accommodated in the first accommodation space 12S of the chuck portion 12, and a rotation operating tool is inserted from the DX1 side of the holder body 10 to fasten and fix the holder body 10 and the first connecting portion 21. Next, the biasing member 40 is accommodated in the third accommodation space 32S of the collet 30. Next, the cutting tool T with the key member 60 abutting against the cutout surface T3 is inserted into the third accommodation space 32S of the collet 30 so that the protruding portion 62 of the key member 60 is aligned with the guide groove 30M, and then moved to the position of the key hole 32H. Next, the cutting tool T and the key member 60 are rotated in the first direction so that the protrusion 62 contacts the first outer edge 321E. Next, the fastening member 50 is rotated about the axis AX to apply a tightening force to the chuck portion 12. This fixes the cutting tool T to the collet 30. The first outer edge 321E is an edge that constitutes the key hole 32H in the circumferential direction DC.

[0043] [Detailed configuration of collet] Next, the configuration of collet 30 will be described in detail with reference to Figures 5 and 6. Figure 5 is a cross-sectional view of the part of collet 30 where keyhole 32H is formed, cut in a direction perpendicular to axial direction DX, and Figure 6 shows collet 30 showing the opposite side of keyhole 32H (the side rotationally symmetrical by 180 degrees with respect to keyhole 32H about axis AX). In Figure 6, keyhole 32H is indicated by a dashed line.

[0044] 5 and 6, the collet 30 further has a relief portion 33. As shown in Fig. 5, the relief portion 33 is recessed from the outer peripheral surface 321G of the holding portion 32 toward the radially inner side DR1 of the holding portion 32. Hereinafter, a surface of the relief portion 33 on the radially inner side DR1 than the outer peripheral surface 321G will be referred to as an "relief plane 33S." A difference d1 (step d1) between the outer peripheral surface 321G and the relief plane 33S in the radial direction DR is, for example, 0.1 mm.

[0045] When the collet 30 is fastened (held) in the holder body 10, as shown in FIG. 2, a gap (hereinafter referred to as "gap portion 34") is formed between the escape plane 33S and the chuck inner surface 12N of the chuck portion 12.

[0046] In this embodiment, as shown in FIG. 5, the relief portion 33 includes a hole facing portion 331. The hole facing portion 331 is disposed at a position that is point symmetrical with respect to the keyhole 32H about the axis AX (in this embodiment, it is 180 degrees rotationally symmetrical with respect to the keyhole 32H about the axis AX). In this embodiment, the hole facing portion 331 is rectangular when viewed along the radial direction DR. The relief portion 33 includes only the hole facing portion 331. In the example shown in FIG. 5, the center of the hole facing portion 331 in the circumferential direction DC is 180 degrees rotationally symmetrical with respect to the keyhole 32H about the axis AX, but the hole facing portion 331 may include a portion that is 180 degrees rotationally symmetrical with respect to the keyhole 32H about the axis AX.

[0047] 6, the hole facing portion 331 is disposed so as to include all of the keyholes 32H (overlap with all of the keyholes 32H) when viewed in the radial direction DR. In other words, the area of ​​the hole facing portion 331 is equal to or greater than the area of ​​the keyholes 32H when viewed in the radial direction DR.

[0048] Specifically, as shown in Fig. 5, the first relief portion length LN1 of the hole facing portion 331 in the circumferential direction DC is greater than the first hole length LH1 of the keyhole 32H in the circumferential direction DC. In the example shown in Fig. 5, the first central angle θ1 formed by both ends of the hole facing portion 331 in the circumferential direction DC when viewed along the axial direction DX is 120 degrees.

[0049] 6, the first relief portion length LN2 of the hole facing portion 331 in the axial direction DX is greater than the second hole length LH2 of the keyhole 32H in the axial direction DX shown in FIG. 4. The second hole length LH2 is the distance (length) between the two second outer edges 322E of the keyhole 32H facing each other in the axial direction DX. However, the second hole length LH2 may be the distance between the two second outer edges 322E of the keyhole 32H facing each other in the axial direction DX plus the length of the machining mark portion 32K protruding in the axial direction DX beyond the second outer edges 322E (see FIG. 4).

[0050] As described above, when the multiple needle rollers 52 (fastening members 50) rotate in the first direction, a fastening force acts on the collet 30 via the chuck portion 12. At this time, the chuck inner peripheral surface 12N does not contact the key hole 32H and the hole facing portion 331. Therefore, the fastening force at the key hole 32H and the hole facing portion 331 is smaller than the fastening force acting on other portions of the collet 30.

[0051] [Effects of the First Embodiment] As in the above configuration, the hole facing portion 331 is disposed as the relief portion 33 at a position that is point symmetric (180-degree rotational symmetric) with respect to the axis center AX as the center, with respect to the keyhole 32H, thereby making it possible to reduce the fastening force acting on the keyhole 32H and the hole facing portion 331. This improves the balance of the fastening force acting on the keyhole 32H and the hole facing portion 331 in the circumferential direction DC, suppresses deformation of the collet 30 (for example, bending such that the collet 30 is wound in the axial direction with the periphery of the keyhole 32H as the base end), and suppresses runout of the cutting tool T.

[0052] [Embodiment 2] Next, a tool holder 100 according to a second embodiment will be described with reference to Fig. 7 to Fig. 10. In the second embodiment, the configuration of the relief portion 33 of the collet 30 is different from that of the first embodiment. Note that a detailed description of the same configuration as in the first embodiment will be omitted.

[0053] 7 to 10, the escape portion 33 of the collet 30 according to the second embodiment includes a hole containing portion 332 in addition to the hole facing portion 331 described in the first embodiment. The hole containing portion 332 is disposed at a position that is rotationally symmetrical by 180 degrees with respect to the hole facing portion 331 about the axis AX, and is spaced apart from the hole facing portion 331 in the circumferential direction DC as shown in Fig. 9. The hole containing portion 332 is rectangular when viewed along the radial direction DR.

[0054] 8, the hole-encompassing portion 332 is disposed so as to include (overlap with) all of the keyholes 32H when viewed in the radial direction DR. In other words, the area of ​​the hole-facing portion 331 is equal to or greater than the area of ​​the keyholes 32H when viewed in the radial direction DR.

[0055] Specifically, as shown in Fig. 8, the fourth relief portion length LN4 of the hole-facing portion 331 in the axial direction DX is greater than the second hole length LH2 of the keyhole 32H in the axial direction DX. Also, as shown in Fig. 9, the third relief portion length LN3 of the hole-enclosing portion 332 in the circumferential direction DC is greater than the first hole length LH1 of the keyhole 32H in the circumferential direction DC. Note that in this embodiment, in the example shown in Fig. 9, the hole-enclosing portion 332 has a second central angle θ2 formed by both ends in the circumferential direction DC when viewed along the axial direction DX of 90 degrees, so that the third relief portion length LN3 of the hole-enclosing portion 332 is smaller than the first relief portion length LN1 of the hole-facing portion 331 (see Fig. 9). Also, the fourth relief portion length LN4 of the hole-enclosing portion 332 (see Fig. 8) is equal to the second relief portion length LN2 of the hole-facing portion 331 (see Fig. 10). Therefore, in this embodiment, the hole containing portion 332 has a smaller area than the hole facing portion 331 .

[0056] [Effects of the second embodiment] As in the above configuration, by arranging the relief portion 33 (hole containing portion 332) so as to overlap with the entire keyhole 32H, the tightening force acting on the keyhole 32H can be further reduced. This further improves the balance of the tightening forces acting on the keyhole 32H and the hole facing portion 331, further suppresses deformation around the keyhole 32H, and effectively suppresses deformation of the collet 30.

[0057] Furthermore, since the hole facing portion 331 and the hole containing portion 332 are disposed to be spaced apart in the circumferential direction DC, it is possible to locally reduce the force acting on the collet 30. In other words, it is possible to distribute the fastening force acting on the collet 30, and deformation of the collet 30 can be effectively suppressed.

[0058] [Embodiment 3] Next, a tool holder 100 according to a third embodiment will be described with reference to Fig. 11 to Fig. 13. In the third embodiment, the configuration of the relief portion 33 of the collet 30 is different from that of the first and second embodiments. Note that detailed description of the same configuration as in the first and second embodiments will be omitted.

[0059] 11 to 13, the relief portion 33 of the collet 30 according to the third embodiment is configured such that the hole facing portion 331 and the hole containing portion 332 described in the second embodiment are connected in the circumferential direction DC of the retaining portion 32 to form one recess (a recess that is continuous in the circumferential direction DC). In other words, the relief portion 33 is formed continuously over the entire circumference of the retaining portion 32 in the circumferential direction DC.

[0060] [Effects of the Third Embodiment] As in the above configuration, the relief portion 33 is continuously formed around the entire circumference of the holding portion 32 in the circumferential direction DC, so that the tightening force acting on the collet 30 can be reduced around the entire circumference, and the balance of the tightening force acting on the key hole 32H and the hole facing portion 331 can be further improved. As a result, deformation around the key hole 32H is further suppressed, and deformation of the collet 30 can be further suppressed. Furthermore, since one recess is formed around the entire circumference of the collet 30, it is possible to avoid the complication of the processing work of forming the hole facing portion 331 and the hole containing portion 332, respectively. In addition, for example, the cutting fluid transmitted from the slit 32G flows along the relief portion 33 around the entire circumference of the holding portion 32, so that the holder body 10 can be cooled, and the thermal displacement of the holder body 10 can be suppressed. As a result, the accuracy of processing the cutting object can be improved.

[0061] [Another embodiment] The present invention may be configured as follows other than the above-described embodiment (common numbers and symbols as in the embodiment are used to designate components having the same functions as in the embodiment).

[0062] (1) In the above first to third embodiments, the cutting tool T is an end mill. However, the cutting tool T may be a tool other than an end mill, such as a drill.

[0063] (2) In the above embodiments 1 to 3, the number of slits 32G is three. However, the number of slits 32G can be changed as appropriate.

[0064] (3) In the above-described first and second embodiments, the hole facing portion 331 has a first central angle θ1 of 120 degrees between both ends in the circumferential direction DC as viewed along the axial direction DX. However, the first central angle θ1 may be equal to or larger than the angle (third central angle θ3) between both ends of the key hole 32H (fitting hole) in the circumferential direction DC as viewed along the axial direction DX (see FIG. 5). Specifically, the first central angle θ1 may be equal to or larger than 20 degrees and smaller than 180 degrees, for example, 90 degrees. Similarly, in the above-described second embodiment, the hole containing portion 332 has a second central angle θ2 of 90 degrees between both ends in the circumferential direction DC as viewed along the axial direction DX. However, the second central angle θ2 may be equal to or larger than the third central angle θ3. Specifically, the second central angle θ2 may be equal to or larger than 20 degrees and smaller than 180 degrees, for example, 120 degrees. In the second embodiment, the first central angle θ1 and the second central angle θ2 have an upper limit such that the hole facing portion 331 and the hole containing portion 332 are not connected. The first central angle θ1 and the second central angle θ2 may be the same or different from each other. In particular, the length of the hole containing portion 332 in the circumferential direction DC (the third relief portion length LN3) may be the same as the length of the hole facing portion 331 (the first relief portion length LN1), may be greater than the length of the hole facing portion 331, or may be smaller than the length of the hole facing portion 331. Similarly, the length of the hole containing portion 332 in the axial direction DX (the fourth relief portion length LN4) may be greater than or smaller than the length of the hole facing portion 331 in the axial direction DX (the second relief portion length LN2). In other words, it is sufficient that the hole facing portion 331 and the hole containing portion 332 each have an area equal to or larger than that of the key hole 32H, and the size and shape of at least one of the hole facing portion 331 and the hole containing portion 332 can be appropriately adjusted according to the magnitude and inclination of the runout of the cutting tool T, thereby suppressing the runout of the cutting tool T. This makes it possible to achieve a balance between the suppression of runout of the cutting tool T and the gripping force by the holder body 10. [Industrial Applicability]

[0065] The present invention can be used in a collet. [Explanation of symbols]

[0066] 10: Holder body 30:コレット 32: Holding part 32H: キーhole (fitting hole) 34: Gap part 60: Corrosion parts (fixed parts) 321G: Outer surface 331: Hole facing part 332: hole inclusion part AX: Axis DC : Circumferential direction DR : radial direction DR1: radial inner side T : Cutting tools

Claims

1. A collet held by a holder body coaxially with a cutting tool that rotates about an axis, the collet comprising: a cylindrical holding portion that houses a part of the cutting tool and is held by the holder body by fastening an outer circumferential surface of the holding portion; a fitting hole into which a fixing member is fitted to fix the cutting tool to the holding portion and is disposed between the cutting tool and the holding portion; a hole facing portion that is recessed radially inward from the outer circumferential surface and is disposed at a position that is point symmetrical with respect to the fitting hole about the axis, A collet, wherein an area of ​​the hole facing portion is equal to or greater than an area of ​​the fitting hole when viewed along a radial direction of the holding portion.

2. The collet according to claim 1 , wherein a length of said hole facing portion in a direction along said axis is equal to or greater than a length of said fitting hole in a direction along said axis.

3. The collet according to claim 1 or 2, further comprising a hole containing portion recessed toward the inside in the radial direction and arranged to contain the fitting hole.

4. The collet according to claim 3 , wherein the hole facing portion and the hole containing portion are connected in the circumferential direction of the holding portion to form one recess.

5. The collet according to claim 3 , wherein the hole facing portion and the hole containing portion are spaced apart in a circumferential direction of the holding portion.

6. The collet according to claim 5 , wherein a central angle formed by both ends of the hole-facing portion in the circumferential direction of the holding portion is equal to or larger than an angle formed by both ends of the fitting hole in the circumferential direction.

7. A collet held by a holder body coaxially with a cutting tool that rotates about an axis, the collet comprising: a cylindrical holding portion that houses a part of the cutting tool and is held by the holder body by fastening an outer circumferential surface of the holding portion; a fitting hole into which a fixing member is fitted to fix the cutting tool to the holding portion and is disposed between the cutting tool and the holding portion; a gap portion that forms a gap between the holder body and the outer circumferential surface and is disposed at a position that is point symmetrical with respect to the fitting hole about the axis, A collet, wherein an area of ​​the gap is equal to or greater than an area of ​​the fitting hole when viewed along a radial direction of the holding portion.

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