WO2015020115A1

WO2015020115A1 - Tool body and cutting tool

Info

Publication number: WO2015020115A1
Application number: PCT/JP2014/070789
Authority: WO
Inventors: 阿曽孝洋
Original assignee: 株式会社タンガロイ
Priority date: 2013-08-07
Filing date: 2014-08-06
Publication date: 2015-02-12
Also published as: JP5962941B2; JPWO2015020115A1

Abstract

The present invention relates to a tool body of a cutting tool, the cutting tool having a mounting seat for mounting a cutting insert. The mounting seat is provided with: a bottom wall surface; a first side wall surface that extends so as to rise from the bottom wall surface; a first surface section that extends between the bottom wall surface and the first side wall surface; and a second surface section that is positioned on an inside end side of the first side wall surface and that extends so as to intersect the first side wall surface. The first surface section has a first curved surface that curves in a direction that is sunken from at least one of the bottom wall surface and the first side wall surface, at least one part of the first curved surface having a first radius of curvature. The second surface section has a second curved surface, at least one part of the second curved surface having a second radius of curvature that is smaller than the first radius of curvature at a cross section that is approximately parallel to the bottom wall surface.

Description

Tool bodies and cutting tools

The present invention relates to a tool body of a cutting tool configured to detachably mount a cutting insert, and a cutting tool including the tool body.

The cutting edge exchange type cutting tool is provided with an insert mounting seat (hereinafter referred to as “mounting seat”) for mounting the cutting insert at the tip of the tool body, and the cutting insert is detachably mounted on the mounting seat. Therefore, the cutting edge can be replaced. Many cutting tool mounting seats have a concave shape having a bottom wall surface in contact with the end face of the cutting insert and at least one side wall surface matching the thickness of the cutting insert to be mounted. The cutting insert is placed on the bottom wall surface of the mounting seat, and fixed by, for example, screwing the screw into the screw hole on the bottom wall surface through the through hole of the cutting insert. The movement and rotation at the are restricted.

On the other hand, when the tool is used, a large load is generated on the mounting seat through the cutting insert, and the stress is concentrated on the corner where the bottom wall surface and the side wall surface of the mounting seat intersect. In order to suppress the occurrence of cracks at the corners of the mounting seat due to this stress concentration, between the bottom wall surface and the side wall surface of the mounting seat, in other words, at the corner portion that is the intersection of the bottom wall surface and the side wall surface, In some cases, a rounded curved surface is provided.

This curved surface can be formed by cutting a corner where the bottom wall surface and the side wall surface intersect. For example, Patent Document 1 discloses that in a mounting seat of a blade-end-exchangeable end mill, a ball end mill is used to provide a groove having a circular arc in cross section, that is, a curved surface, at a boundary portion between a side wall surface and a bottom wall surface.

JP 2004-174684 A

The curved surface is formed between the bottom wall surface of the mounting seat at the corner and the side wall surface using, for example, a ball end mill. In that case, a ball end mill for machining the curved surface at the corner of the mounting seat is required to have a tool diameter smaller than twice the radius of curvature of the desired curved cross section. However, the smaller the tool diameter of the ball end mill, the more restrictions on cutting conditions. That is, a ball end mill having a relatively small tool diameter cannot take a large amount of cutting because its cutting edge is relatively short. For this reason, processing takes time and processing efficiency is not good. In addition, a ball end mill with a relatively small tool diameter is more likely to bend than a ball end mill with a relatively large tool diameter, and the feed cannot be increased, resulting in poor machining efficiency. As a result, there is a problem that the processing cost of the mounting seat is increased and the price of the cutting tool is increased.

On the other hand, in order to reduce the processing cost, it is conceivable to process such a curved surface with a ball end mill having a relatively large tool diameter. However, in a ball end mill with a large tool diameter, the radius of curvature of the curved surface that can be processed also increases. As the radius of curvature of the curved surface increases, the curved surface becomes wider than necessary to relieve stress concentration at the corners of the mounting seat, and the bottom wall of the mounting seat and A side wall surface becomes narrow. The cutting insert is fixed to the cutting tool by support by the bottom wall surface and the side wall surface of the mounting seat. Therefore, as the bottom wall surface and the side wall surface become narrower, the support area of the mounting seat that comes into contact with the cutting insert decreases accordingly, and the fixing performance of the cutting insert decreases. In particular, when the curved surface is widened, the area of the side wall surface connected to the curved surface is narrowed, and the support area of the side wall surface of the mounting seat with respect to the side surface of the cutting insert is reduced. If it does so, the support performance of the cutting insert by a mounting seat will become weak, and the capability to suppress rotation of the cutting insert by the load at the time of cutting will fall.

The purpose of the present invention is to provide a curved surface of a desired size at the corner to relieve stress concentration at the corner of the mounting seat, and to ensure a wide wall surface for supporting the cutting insert in the mounting seat, The object is to provide a tool body and a cutting tool capable of enhancing the holding performance of a cutting insert.

The cutting body according to one aspect of the present invention is a tool body of a cutting tool having a mounting seat for mounting a cutting insert, and the mounting seat extends so as to be connected to the outer surface of the tool body. And a first side wall surface extending so as to open to the outer surface, wherein the first side wall surface includes an outer end located on the outer surface side and an inner end opposite to the outer end. The first side wall surface extending from the bottom wall surface and extending between the bottom wall surface and the first side wall surface and extending to connect the two, A first surface portion extending along the first side wall surface; and a second surface portion disposed on the inner end side of the first side wall surface and extending so as to intersect the first side wall surface. The first surface portion is curved in a direction recessed from at least one of the bottom wall surface and the first side wall surface. The tool has a first curved surface, and an open end of the first surface portion along the outer end portion of the first side wall surface is substantially parallel to the first side wall surface and substantially parallel to the bottom wall surface. When viewed from the outside of the body, at least a portion of the first surface portion has a first radius of curvature, the second surface portion has a second curved surface, and at least one of the second curved surfaces. The portion has a second radius of curvature in a cross section substantially parallel to the bottom wall surface, and the second radius of curvature is smaller than the first radius of curvature R1.

The present invention also resides in a cutting tool having the tool body of the present invention.

In the tool body and the cutting tool according to one aspect of the present invention, the curvature of the second surface portion of the second surface portion is larger than the radius of curvature of the first surface portion between the bottom wall surface and the side wall surface of the mounting seat. The radius is reduced. Therefore, in the first surface portion where a relatively large force acts, the first radius of curvature can be ensured to an appropriate size, stress concentration at that portion can be suitably reduced, and in the second surface portion, By making the curvature radius relatively small, it is possible to secure a wide width of the wall surface of the mounting seat, particularly the side wall surface. Therefore, according to one aspect of the present invention, the occurrence of defects such as cracks in the mounting seat of the tool body can be more securely suppressed, and the holding performance of the cutting insert at the mounting seat can be sufficiently enhanced.

Preferably, the second surface portion has a main wall surface connected to the first side wall surface through the connecting wall surface. The second curved surface may extend to a connection portion between the connecting wall surface and the main wall surface. Further, the mounting seat may further include a second side wall surface. The second side wall surface has an outer end located on the outer surface side of the tool body and an inner end opposite to the outer end, and is erected from the bottom wall surface from the outer end to the inner end. It is good to extend so as to be adjacent to the first side wall surface with the second surface portion interposed therebetween. The second surface portion can further include a second connecting surface that connects the main wall surface and the second side wall surface. In this case, it is preferable that the third curved surface extends at a connection portion between the second surface portion and the main wall surface. At least a portion of the third curved surface has a third radius of curvature in a cross section substantially parallel to the bottom wall surface, and the third radius of curvature is preferably smaller than the first radius of curvature. Preferably, the second curvature radius and the third curvature radius are substantially equal. For example, the first curvature radius is 0.30 mm or more. For example, the second radius of curvature is less than 0.30 mm.

FIG. 1 is a perspective view of a tool body of a cutting tool according to an embodiment of the present invention. FIG. 2 is a perspective view of the distal end portion of the tool body including the mounting seat for the tool body of the cutting tool according to the embodiment of the present invention. FIG. 3 is a perspective view schematically showing a place where the cutting insert is mounted on the mounting seat of the cutting tool of FIG. FIG. 4 is a perspective view of the cutting tool in a state where the cutting insert is mounted on the tool body in the embodiment of the present invention. FIG. 5 is a perspective view of the mounting seat of FIG. 1 viewed from another direction. FIG. 6A is a perspective view in another direction of the tool body of the cutting tool. 6B is a cross-sectional view of the tool body taken along the line VIB-VIB in FIG. 6A, and shows a state where the cutting insert is mounted, indicated by a two-dot chain line. FIG. 7 is a perspective view of the mounting seat of FIG. 1 as viewed from a direction parallel to the bottom wall surface and the first side wall surface. FIG. 8A is a perspective view in another direction of the tool body of the cutting tool. FIG. 8B is an enlarged view of the mounting seat portion in a cross section obtained by cutting the mounting seat of FIG. 8A along the line VIIIB-VIIIB. FIG. 9A is a perspective view of the cutting tool in another direction. FIG. 9B is an enlarged view of a mounting seat portion in a cross section of the mounting seat with the cutting insert of FIG. 9A cut along the line IXB-IXB.

Embodiments of a cutting tool to which the present invention is applied will be described with reference to the drawings.

FIG. 1 is a perspective view of a tool body of a cutting tool according to an embodiment of the present invention. FIG. 2 is a perspective view of the distal end portion of the tool body including the mounting seat for the tool body of the cutting tool in the embodiment of the present invention shown in FIG. FIG. 3 is a perspective view schematically showing the mounting of the cutting insert on the mounting seat of FIG. FIG. 4 is a perspective view of the cutting tool in a state where the cutting insert is mounted on the tool body in the embodiment of the present invention. FIG. 5 is a perspective view of the mounting seat of FIG. 1 viewed from another direction. FIG. 6A is a perspective view in another direction of the tool body of the cutting tool. FIG. 6B is a cross-sectional view of the tool body taken along the line VIB-VIB in FIG. 6A, and is a diagram schematically showing a state where the cutting insert is mounted by a two-dot chain line. FIG. 7 is a perspective view of the mounting seat of FIG. 1 as viewed from a direction parallel to the bottom wall surface and the first side wall surface. FIG. 8A is a perspective view in another direction of the tool body of the cutting tool. FIG. 8B is an enlarged view of a cross section obtained by cutting the mounting seat of FIG. 8A substantially parallel to the bottom wall surface. FIG. 9A is a perspective view of the cutting tool in another direction. FIG. 9B is an enlarged view of a cross section obtained by cutting the mounting seat on which the cutting insert of FIG. 9A is mounted substantially parallel to the bottom wall surface.

Here, in describing this embodiment, terms indicating directions such as “upward”, “downward”, and “clockwise direction” are used for convenience, but these terms are absolute positional relationships in space. It is not intended to limit.

As shown in the figure, the cutting tool 1 of this embodiment is an end mill capable of shoulder cutting. Although the tool diameter of the cutting tool 1 is about 40 mm, it is not limited to this. The cutting tool 1 includes a tool body 3 on which a cutting insert 2 is detachably mounted. The tool body 3 extends from the front end 3a to the rear end 3b along the axis A, with the direction of the axis A shown in FIG. The tool body 3 has the mounting seats 4 of the cutting insert 2 arranged uniformly at three places around the tip 3a around the axis A. The cutting tool 1 is used with the cutting insert 2 mounted on each of the three mounting seats 4. The cutting tool 1 in the present embodiment is a three-blade end mill, but the present invention is not limited to this, and the present invention is also applicable to a single-blade or a plurality of cutting blades such as a two-blade. Can do. The shank on the rear end 3b side of the tool body 3 is attached to a machine tool (not shown) via a holding tool (holder) such as an arbor. The axis A can be the rotation center axis of the cutting tool 1, but the cutting tool 1 may rotate with respect to the workpiece, or the workpiece may rotate with respect to the cutting tool 1.

Hereinafter, for the sake of convenience, the tip end side of the tool body 3 is referred to as the lower side along the axis A, but the usage form of the cutting tool 1 is not limited to the one used with the tip end portion of the tool body 3 facing down. In other words, the cutting tool according to the present invention is assumed to be used in any other direction, such as a tool body 3 with the tip end side facing upward.

As shown in FIGS. 3 and 4, the cutting insert 2 attached to the tool body 3 includes an upper surface and a lower surface, which are two opposing end surfaces each having a substantially triangular shape, and a peripheral side surface extending therebetween. And a positive type having a plate-like outer shape. However, either of the two end surfaces may be the upper surface, and one of the two end surfaces shown in FIG. As will be described in detail later, the cutting insert 21 has a corner cutting edge 201 at one apex portion of a substantially triangular shape on the upper surface, a main cutting edge 202 connected to both sides of the corner cutting edge 201, and a wiping edge 203. It is comprised so that it can be used as a cutting-blade part. Therefore, as shown in FIG. 4, the cutting insert 2 is fixed to the tool body 3 such that the cutting edge portion to be used protrudes from the tip and outer periphery of the tool body 3 when the tool body 3 is mounted. In addition, the cutting insert 2 with which this invention is mounted | worn is not restricted to a positive type, You may have other various shapes (For example, the combination of a negative type and a negative type and a positive type).

On the other hand, as shown in FIGS. 2 and 5, each mounting seat 4 provided on the tool body 3 for receiving the cutting insert 2 has a bottom wall surface 5 and three sides extending in a direction intersecting the bottom wall surface 5. Wall 6. Further, each mounting seat 4 has a first surface portion 8 and a second surface portion 9.

As shown in FIGS. 1 to 4, the mounting seat 4 is provided in a space 31 that is partially hollowed from the outer peripheral side of the tool body 3 toward the axis A side. It is a dent enough to accommodate 2. The recess has the lowest bottom wall surface 5 when viewed from a direction substantially parallel to the bottom wall surface 5 of the cutting insert 2, and extends from the bottom wall surface 5 so as to stand upright and partially surrounds the bottom wall surface 5. 6 is generally formed. Since each of the upper and lower surfaces of the cutting insert 2 has a substantially triangular shape, the bottom wall surface 5 of the mounting seat 4 has a substantially triangular shape. One apex portion 501 of the substantially triangular shape of the bottom wall surface 5 is located on the outer peripheral side and the tip end side of the tool body 3 so as to face the work piece during cutting, and the other apex portion 502 of the mounting seat 4 Thus, the remaining one vertex 503 is located on the outer peripheral side and the rear end side of the tool body 3 toward the second surface portion 9 located on the axis A side. And the side wall surface 6 (61, 62, 63) which partially surrounds the bottom wall surface 5 is provided with respect to the corresponding side part of the substantially triangular bottom wall surface 5. The first side wall surface 61 is positioned with respect to the side portion of the bottom wall surface 5 connecting the two

adjacent vertex portions

502 and 501, and the second side wall surface 61 connecting the two

adjacent vertex portions

503 and 502, along the side portion of the bottom wall surface 5. And the 3rd side wall surfaces 62 and 63 are provided. The side portion of the bottom wall surface 5 connecting the two

vertex portions

501 and 503 is directly connected to the outer peripheral surface (first outer surface) 3c of the tool body 3, and there is no side wall surface there. Furthermore, the part along the vertex part 501 of the bottom wall surface 5 is directly connected to the front end surface (second outer surface) 3d of the tool body 3, and there is no side wall surface there. Therefore, when the cutting insert 2 is attached to the attachment seat 4, the cutting insert 2 is exposed to the outer peripheral side and the distal end side of the tool body 3. Hereinafter, the side from the side connecting the two

adjacent vertex portions

501 and 503 to the vicinity of one vertex portion 501 is collectively referred to as “open side”. Moreover, the 1st side wall surface 61 is extended so that it may open to the outer peripheral surface side which is the open | release side of a tool body. The first side wall surface 61 is positioned on the tip surface (second outer surface) 3d side of the tool body extending so as to intersect the outer peripheral surface of the tool body, and particularly extends so as to be substantially connected to the second outer surface. To do. The side wall surfaces 6 (61, 62, 63) do not extend directly from the bottom wall surface 5, but are arranged at an angle with a substantially constant angle with the first surface portion 8 interposed therebetween. As described above, the mounting seat 4 is a concave portion that is generally formed by the bottom wall surface 5 and the side wall surface 6, and the cutting insert 2 is configured to be accommodated in the concave portion. The angle of each side wall surface 6 (61, 62, 63) with respect to the bottom wall surface 5 is set in such a range that the contact area between the cutting insert 2 and the side wall surface 6 increases as much as possible and does not interfere with the attachment / detachment of the cutting insert 2. Has been. In the tool body 3 of the present embodiment in which the positive type cutting insert 2 is mounted, the side wall surface 6 is disposed to be inclined with respect to the bottom wall surface 5 at an angle that matches the inclination angle of the side surface of the cutting insert 2. Although the three side wall surfaces 6 have been described here, two of the second and third side wall surfaces 62 and 63 can be regarded as one wall surface. It can also be regarded as divided. Thus, if it divides | segments into two parts by an intermediate | middle dent, the both ends of a side wall surface will contact the peripheral side surface 4 of the cutting insert 2 reliably, and a fixing capability will improve stably. As shown in FIG. 3, when the tool body 3 is viewed from the outer peripheral side, that is, from the open side, the apex 502 is located at the innermost part of the mounting seat 4 (most on the axis A side in the direction toward the axis A). The cutting insert 2 is installed such that one apex portion (corner portion) 23 of the triangle is located toward the second surface portion 9 to be connected. Then, two first and second side wall surfaces 61 and 62 are formed on the mounting seat 4 with the second surface portion 9 interposed therebetween. In FIG. 3, these side wall surfaces 61, 62 are opposed to side surfaces 25, 26 along two adjacent side portions across one corner portion 23 of the upper surface 28, which is one end surface located on the front side of the cutting insert 2. To be arranged. The side wall surface 6 has the third and second side wall surfaces 63 and 62 located on one side (rear end portion side) and the first side on the other side (front end portion side) when viewed from the open side of the mounting seat 4. It is comprised so that the wall surface 61 may be located. The second surface portion 9 is located between the second side wall surface 62 and the first side wall surface 61. A recess 64 is located between the third side wall surface 63 and the second side wall surface 62, and among these, the end of the side wall surface 63 located on the outer side (open side) of the cutting tool 1 is located on the tool body 3. It is an open end 65 that spreads outward on the rear end 3b side. The height of the side wall surface 6 from the bottom wall surface 5 is determined according to the thickness of the cutting insert 2 to be mounted.

As described above, the bottom wall surface 5 of the mounting seat 4 has a shape corresponding to the shape of the cutting insert 2 to be mounted. In the present embodiment, the cutting insert 2 has an outer shape including a substantially triangular upper surface 28 and lower surface 29, and side surfaces 25, 26, 27 connecting the upper surface 28 and the lower surface 29.

The cutting insert 2 is provided with a through hole 21 for screw fixing that penetrates from the upper surface 28 to the lower surface 29 at the center. On the other hand, the bottom wall surface 5 of the mounting seat 4 is provided with a screw hole 51 for screw fixing at a position facing the through hole 21 when the cutting insert 2 is mounted. Therefore, the cutting insert 2 is placed on the bottom wall surface 5 of the mounting seat 4, the tightening screw is inserted into the through hole 21, and is tightened into the screw hole 51 until the head of the screw contacts the cutting insert 2. The cutting insert 2 is fixed to the mounting seat 4 by this screwing. Here, since the side wall surfaces 61, 62, 63 abut against the side surfaces 25, 26 of the cutting insert 2, the cutting insert 2 cannot rotate around the axis of the through hole 21, resulting in cutting The insert 2 is supported and fixed by the side wall surface 6 in a rotational direction in which the fixing is insufficient only by screw fixing.

The cutting insert 2 of the present embodiment has a plate shape with a substantially triangular end face as described above. Therefore, the upper surface 28 of the cutting insert 2 has three apex portions (corner portions) 22, 23, and 24, and a cutting edge is formed at the intersecting ridge line portion between the upper surface 28 and the side surfaces 25, 26, and 27. ing. As shown in FIG. 3, the cutting edge is located at the corner cutting edge 201 provided at each

vertex portion

22, 23, 24 and the intersecting ridge line connecting each vertex portion, with the corner cutting edge 201 interposed therebetween. The main cutting edge 202 and the wiping edge 203 extending from the center are formed. The cutting insert may be modified so that the cutting edge is formed not only at the intersecting ridge line portion with the upper surface 28 but also at the intersecting ridge line portion between the lower surface 29 and the side surfaces 25, 26, 27. In this case, the configuration of the blade on the lower surface side is the same as that on the upper surface 28. Furthermore, it is needless to say that the configuration of the cutting edge is not limited to this, and other configurations (for example, an inclined shape and a curved shape) may be further provided.

As seen in FIGS. 2 and 5, among the side wall surfaces 6, the first side wall surface 61 is disposed on the most distal end portion 3 a side of the cutting tool 1 as compared with the second side wall surface 62 and the third side wall surface 63. Is done. As described above, the mounting seat 4 including the first side wall surface 61 is opened toward the distal end side of the cutting tool 1. That is, the first side wall surface 61 includes an inner end 611 connected to the second surface portion 9 on the back side of the mounting seat 4 and an open side opposite to the inner end 611, that is, the tip of the cutting tool 1. And an outer end 612 positioned on the side facing the workpiece, and the outer end 612 is an open end. Here, as described above, the first side wall surface 61 is a portion that supports and fixes the side surface 25 of the cutting insert 2. Further, the open end portion, that is, the outer end portion 612 and the vicinity thereof is a portion that supports the vicinity of the blade that contacts the workpiece of the cutting insert, and is also a portion that is strongly subjected to stress due to cutting resistance during cutting. The problem that cracks and the like are likely to occur at the corners of the mounting seat 4, which is a connecting portion between the bottom wall surface 5 and the side wall surface 6, due to stress concentration during cutting is as described above. Therefore, also in the present embodiment, a curved first surface portion 81 (8) is formed between the first side wall surface 61 and the bottom wall surface 5 in order to relieve stress concentration. The first surface portion 81 is curved in a direction recessed in both the bottom wall surface 5 and the side wall surface 6, and has a curved surface (first curved surface) (see FIGS. 6B and 7). That is, as shown in FIG. 6B, the first surface portion 81 has a corner 52 (portion indicated by a dotted line in the figure) formed by the extended surface of the first side wall surface 61 and the extended surface of the bottom wall surface 5. It is a portion that is evenly cut into a curved shape on both the side wall surface 61 side and the bottom wall surface 5 side. As shown in FIG. 7, when the first surface portion 81 is viewed from the direction parallel to the bottom wall surface 5 and the first side wall surface 61 on the open side of the tool body 3, the minimum curvature radius of the first surface portion 81. Is R1. Here, the minimum curvature radius R <b> 1 is roundness at the open end on the outer peripheral side of the first surface portion 81. The first surface portion 81 may be a curved surface that curves with the same radius of curvature throughout, or may have a different radius of curvature depending on the part. In the cutting tool 1 of this embodiment, the curvature radius R1 was 0.80 mm. The curvature radius R1 is preferably set to 0.30 mm or more. When the curvature radius R1 is 0.30 mm or more, the stress concentration is more appropriately mitigated, and it is more preferable that the mounting seat 4 is damaged when the fastening force or cutting force of the cutting insert 2 is applied. Can be prevented. The curvature radius R1 is more preferably 0.50 mm or more. When the curvature radius R1 is 0.20 mm, the dent of the first surface portion 81 is insufficient to relieve stress concentration, and the cutting tool is repeatedly used so that a large load of a certain degree or more is applied. The mounting seat was damaged due to stress concentration. On the other hand, when the radius of curvature R1 was set to 0.30 mm or more, no crack occurred in the corner of the mounting seat under the same experimental conditions. Thus, by setting the curvature radius R1 to 0.30 mm or more, stress concentration at the corner of the mounting seat 4 can be relaxed, crack formation can be sufficiently suppressed, and the tool life of the tool body is greatly extended. be able to. Moreover, the larger the radius of curvature, the wider the processing area of the curved surface and the easier it is to process. However, as the first surface portion 81 becomes wider, the areas of the first side wall surface 61 and the bottom wall surface 5 are scraped, and the holding area of the cutting insert 2 decreases. Therefore, the radius of curvature R1 is provided with a predetermined upper limit so that the area of the first side wall surface 61 can ensure a range in which the area of the first side wall surface 61 can sufficiently act in terms of fixing the cutting insert 2. This upper limit can be determined according to the thickness of the cutting insert 2 to be mounted and the depth of the concave portion to be the mounting seat 4.

In this embodiment, as shown in FIG. 6B, the first surface portion 81 includes a corner portion 52 (a portion indicated by a dotted line in the figure) composed of an extended surface of the first side wall surface 61 and an extended surface of the bottom wall surface 5. ) Was cut into a curved surface evenly on both the first side wall surface 61 side and the bottom wall surface 5 side. However, the present invention is not limited to the one that is evenly scraped on both the first side wall surface 61 side and the bottom wall surface 5 side. That is, the first surface portion 81 may be formed by recessing only the first side wall surface 61 side, or by recessing only the bottom wall surface 5 side, or even if both are recessed. It doesn't have to be. The first surface portion 81 may be a curved surface that smoothly connects the first side wall surface 61 and the bottom wall surface 5 from one surface to the other surface without being angular so that stress concentration at the corners can be reduced. That's fine.

Further, the stress at the time of cutting is the strongest acting near the open end 612 closest to the corner cutting edge, but the stress is not limited to the open end 612 but the third and second side wall surfaces 63, It also acts between 62 and the bottom wall surface 5. Further, not only at the time of cutting, stress is generated only by tightening with a screw to fix the cutting insert 2. Therefore, a curved first surface portion 82 (8) is also provided between the third and second side wall surfaces 63 and 62 and the bottom wall surface 5 to relieve stress concentration.

Further, the cutting insert 2 is formed with cutting edges around the

corner portions

22, 23, 24, and when the cutting insert 2 is mounted on the mounting seat 4, the cutting blade that has acted on the workpiece is rotated to be adjacent to the cutting insert 2. As a result, it can be used three times. As described above, each cutting edge has a main cutting edge 202, a corner cutting edge 201, and a front or bottom edge that acts as a wiping edge 203. Since the cutting tool 1 is an end mill for shoulder machining, the main cutting edge performs wall machining for shoulder machining and the bottom edge performs planar machining.

As described above, the cutting edge in the cutting insert 2 may be formed not only on one side but also on both sides. In the case of the cutting insert formed on both sides, it can be used a total of 6 times by turning the mounting surface upside down. However, if the cutting insert 2 is pressed and fixed to the mounting seat 4 in a state where the cutting blade portion is in contact with the mounting seat 4, the cutting blade portion in contact with the mounting seat 4 may be damaged. For example, when the cutting insert 2 is mounted with the upper surface 28 of the cutting insert 2 facing upward, the cutting blade on the lower surface 29 side must not be in contact with the mounting seat 4. Therefore, the

first surface portions

81 and 82 described above are portions where the cutting edges of the lower surface 29 are located. Therefore, the cutting edges of the lower surface 29 and the mounting seat 4 are formed by the curved surfaces of the

first surface portions

81 and 82. Is formed so that the cutting edge does not contact the mounting seat 4. As a result, the cutting edge does not contact the mounting seat 4 and is prevented from being damaged. In this case, both the first side wall surface 61 side and the bottom wall surface 5 side are recessed on the curved surface so that the cutting edge is not in contact with the side wall surface and the bottom wall surface. It is preferable.

The radius of curvature of the first surface portion 82 along the third and second side wall surfaces 63 and 62 may be the same as or different from that of the first surface portion 81 along the first side wall surface 61. Also good. When different, it is preferable that the radius of curvature of the surface portion 82 along the third and second side wall surfaces 63 and 62 is smaller than the radius of curvature of the surface portion 81 along the first side wall surface 61. As described above, the upper limit of the radius of curvature of the surface portion 82 can be appropriately determined within a range in which a certain area or more can be secured on the third side wall surface 63 and the second side wall surface 62.

Further, as seen in FIG. 2, the tool body 3 has a second surface portion 9 between the first side wall surface 61 and the second side wall surface 62. That is, the first side wall surface 61 and the second surface portion 9 are arranged from the front end side of the tool body 3 toward the axis A side and the rear end side, and further toward the open side, the second side wall surface 62, the concave portion 64, In the order of the third side wall surface 63, the respective wall surface portions or surface portions are continued. Here, the second surface portion 9 extends so as to intersect with the first side wall surface 61 and the second side wall surface 62, and further extends so as to intersect with the bottom wall surface 5. However, even when the crossing angle of the second surface portion 9 with respect to the bottom wall surface 5 is gentle so that the second surface portion 9 substantially constitutes an extended surface of the bottom wall surface 5 when viewed as a whole. Good.

Here, during cutting of the cutting tool 1, the cutting insert 2 has a cutting resistance that causes the cutting insert 2 to rotate in the clockwise direction CA when viewed from the surface side of the cutting insert 2 (upper surface side in FIG. 3). It acts in the direction to do. In other words, the entire working cutting edge portion of the substantially triangular side portion of the upper surface rarely acts at once, and only the cutting edge and the bottom edge in the vicinity of the corner portion of the working cutting edges often act on the cutting. The resultant cutting force is intended to rotate the cutting insert 2 in the clockwise direction in FIG. In order to counteract this rotational force, it is desirable that the side surfaces 25, 26 of the cutting insert 2 be firmly supported by the side wall surfaces 6 that can come into contact with the side surfaces 25, 26 of the cutting insert 2. In that case, the area of the side wall surface 6 should be large. In other words, the side surfaces 25 and 26 of the cutting insert 2 should be in contact with the side wall surface 6 as much as possible. Here, in order to ensure a large area of the side wall surface 6, as shown in the cross-sectional views of FIGS. 8B and 9B, when the second side wall surface 62 is as close as possible to the first side wall surface 61, the second surface 9 is obtained. , The width L1 of the cutting insert 2 is reduced, and the portion of the side surface in the vicinity of the apex 23 facing the second surface portion 9 of the cutting insert 2 is not in contact with the second and first side wall surfaces 62 and 61. When the reference line B1 parallel to the axis A that is the rotation center axis is positioned at the inner end 621 of the second side wall surface 62 as shown in FIG. 8B, the angle of inclination of the second side wall surface 62 from the reference line B1 Can be defined as the angle α. Similarly, when the reference line B2 parallel to the axis A is positioned at the inner end 611 of the first side wall surface 61 as shown in FIG. 8B, the angle of inclination of the first side wall surface 61 from the reference line B2 is an angle. It can be defined as β. The angles α and β are determined according to the angle of the corner portion of the cutting insert. When the second and first side wall surfaces 62 and 61 are provided at the angles α and β, the second surface portion 9 is as far as possible from the back of the mounting seat 4 (downward in the cross-sectional view of FIG. 8B, that is, the mounting seat). 2), the second and first side wall surfaces 62 and 61 contacting the side surfaces 25 and 26 of the cutting insert 2 are widened. Therefore, the inner end 621 of the second side wall surface 62 on the second surface portion 9 side may be extended to a position further away from the axis of the screw hole 51 that substantially coincides with the rotation center of the cutting insert.

Now, in order to make the second side wall surface 62 as close to the first side wall surface 61 as possible, it is conceivable that the second surface portion 9 is not provided. That is, in forming the mounting seat 4, the second surface portion 9 is not provided, but the second side wall surface 62 and the first side wall surface 61 are provided with corner portions that match the corner 23 of the cutting insert 2. Is also possible. However, if the corner portion is directly formed by the second side wall surface 62 and the first side wall surface 61, stress is concentrated on the corner portion during cutting, and cracks are likely to be generated from the corner portion. Further, in the alignment with the cutting insert 2, the strict shape corresponding to the corner 23 of the cutting insert 2 is troublesome in forming the mounting seat 4, and there are aspects such as an increase in cost. Therefore, by providing the second surface portion 9, the stress concentration in the back portion (inner portion) of the mounting seat 4 is relieved, and the cutting insert 2 is disposed at a more appropriate position on the mounting seat 4. And it can support more firmly by the 1st side wall surfaces 62 and 61. FIG. For these reasons, the second surface portion 9 is necessary, but its width L1 is desirably small. The width of the second surface portion 9 is minimized, and the second side wall surface 62 is as small as possible. Is preferably brought closer to the first side wall surface 61 side.

As shown in FIGS. 8B and 9B, the second surface portion 9 is specifically shaped as follows. Specifically, the second surface portion 9 includes a connecting wall surface 911 connected to the inner end 611 of the first side wall surface 61, a main wall surface 912 substantially orthogonal to the connecting wall surface 911, and approximately orthogonal to the main wall surface 912. The connecting wall surface 913 is connected to the inner end 621 of the second side wall surface 62. The main wall surface 912 is arranged so as not to interfere with various cutting inserts assumed to be used, and to minimize the distance from the outer shape of the various cutting inserts. Further, the main wall surface 912 is disposed at an angle γ of 90 ° or more with respect to the bottom wall surface 5 and is formed so as to expand the space on the bottom wall surface 5. With such an angle, when machining the main wall surface 912 with a tool such as an end mill, the tool prevents interference with the bottom wall surface 5 or damage to the bottom wall surface 5 caused by the generated chips. it can. There is no upper limit to the angle γ formed by the main wall surface 912 and the bottom wall surface 5, but it is preferably set to an angle of 130 ° or less in order to minimize the distance from the outer shape of the cutting insert. The connection between the connecting wall surfaces 911 and 913 and the main wall surface 912 is illustrated as being substantially orthogonal. However, the present invention is not limited to this, and the intersection angle depends on the shape of the tool forming the second surface portion 9 and the like. It is set appropriately. A curved surface (second curved surface) 901 is provided at a connection portion between the connecting wall surface 911 and the main wall surface 912, and a curved surface (third curved surface) 902 is provided at a connection portion between the main wall surface 912 and the connecting wall surface 913. Is provided. In forming the second surface portion 9, corners are also formed at the end portions of the connecting wall surfaces 911 and 913 formed by digging the tool body 3. Since stress concentration easily occurs in this portion, stress concentration at the corner can be reduced by providing

curved surfaces

901 and 902 at the corner.

However, as can be seen from FIG. 8B, when the sizes of the

curved surfaces

901 and 902 are increased, the inner end 621 opposite to the outer end located on the outer peripheral surface 3c side in the second side wall surface 62 is It will be separated from the inner end 611 of the first side wall surface 61. Therefore, the curvature radius R2 of the curved surface 901 and the curvature radius R3 of the curved surface 902 shown in FIG. 8B are made as small as possible so that the inner end 621 of the second side wall surface 62 and the inner end 611 of the first side wall surface 61 are brought closer. Is preferred. In particular, the curvature radius R3 at the cross section of the curved surface 902 (a cross section substantially parallel to the bottom wall surface) is important. The second side wall surface 62 can be brought closer to the first side wall surface 61 by reducing the curvature radius R3 of the curved surface 902. The curvature radius R3 is preferably less than 0.30 mm. That is, it is preferable that the curvature radius R3 is smaller than the curvature radius R1 described above. In the cutting tool of this embodiment, the radius of curvature R3 was about 0.20 mm. As described above, the curvature radius R3 is made smaller than the curvature radius R1, so that the width of the second side wall surface 62, that is, the length from the open side to the second surface portion 9 is extended. The portion of the second side wall surface 62 that contacts the side surface 26 can be increased, and the holding performance of the side surface 26 can be improved. As a result, the conflicting problem of preventing the cutting insert 2 from rotating and, on the other hand, relaxing the stress concentration and preventing the mounting seat 4 from being damaged can be solved. The curvature radius R2 of the curved surface 901 may be as large as R3. Moreover, both may be the same value or different values. However, even if they are different, both are preferably less than 0.30 mm. The curvature radii R2 and R3 are preferably 0.05 mm or more. If curvature radii R2 and R3 are the size which can be formed by cutting, for example, possibility that it will become the starting point of destruction of cutting tool 1 is low.

The mounting seat 4 of the cutting tool 1 of the present embodiment, in particular, the first surface portion 8 and the second surface portion 9 can be easily processed by using an end mill such as a ball end mill, a radius end mill, or a square end mill. Can do. However, when machining by a ball end mill, in order to reduce the curvature radii R2 and R3 of the

curved surfaces

901 and 902, a ball end mill having a small tool diameter must be used. Accordingly, the cutting cost such as the cutting depth is reduced when the tool diameter is small, which may increase the processing cost. The shape of the mounting seat 4 in this embodiment can be processed by a radius end mill or a square end mill. Therefore, it is possible to process under highly efficient cutting conditions, and the processing cost can be greatly suppressed. In particular, when a radius end mill having a rounded corner corresponding to the radii of curvature R2 and R3 is used, machining can be performed under highly efficient cutting conditions. In this case, the radius of curvature R2 and R3 are transferred as they are in the corner shape of the radius end mill.

The second surface portion 9 has a main wall surface connected to the first and second side wall surfaces via two connecting wall surfaces 911 and 913, and has a second and third curved surface therebetween. However, the second surface portion 9 may have a non-square shape in a cross section substantially parallel to the bottom wall surface of the mounting seat, for example, a substantially arc shape such as a substantially semicircular shape. In this case, the 2nd surface part 9 is good to have a 2nd curvature radius smaller than the said 1st curvature radius at least partially in the cross section substantially parallel to a bottom wall surface.

These cutting tools can be used for cutting steel materials by being mounted on a machine tool via a holder. The present invention is applied to lathe tools, rotary cutting tools, and the like, and there are almost no restrictions on the applicable cutting tools. Although only the rotary cutting tool is described in the embodiment, the present invention is also applicable to a lathe tool. According to the form of each cutting tool, the side wall surface closest to the cutting edge to which cutting resistance is applied is defined as the first side wall surface.

The present invention is not limited to the embodiment described above, and various modifications and additions can be made without departing from the gist of the present invention. For example, the present invention can be applied to a cutting tool using a cutting insert without a through hole. Further, for example, chamfering may be further performed around the outer end of the first surface portion 8, that is, around the open end.

Claims

A tool body (3) of a cutting tool (1) having a mounting seat (4) for mounting a cutting insert (2),
The mounting seat (4)
A bottom wall surface (5) extending to connect to the outer surface (3c) of the tool body;
A first side wall surface (61) extending to open to the outer surface side, wherein the first side wall surface is opposite to the outer end portion (612) located on the outer surface side and the outer end portion. An inner end (611) of the first side wall surface (61) extending so as to stand upright from the bottom wall surface,
The first wall surface is located between the bottom wall surface and the first side wall surface, extends to connect the bottom wall surface and the first side wall surface, and extends along the first side wall surface (61). A surface portion (81) of
A second surface portion (9) disposed on the inner end (611) side of the first side wall surface and extending so as to intersect the first side wall surface;
The first surface portion (81) has a first curved surface that curves in a direction recessed from at least one of the bottom wall surface (5) and the first side wall surface (61), and the first surface portion An open end along the outer end (612) of the first side wall surface (61) in (81) is substantially parallel to the first side wall surface (61) and substantially parallel to the bottom wall surface (5). When viewed from the outside of the tool body, at least a portion of the first surface portion (81) has a first radius of curvature (R1);
The second surface portion (9) has a second curved surface (901), and at least a part of the second curved surface (901) has a second radius of curvature (R2) in a cross section substantially parallel to the bottom wall surface. The second radius of curvature (R2) is smaller than the first radius of curvature (R1),
Tool body (3).
The second surface portion (9) has a main wall surface (912) connected to the first side wall surface (61) via a connecting wall surface (911),
The second curved surface (902) extends to a connection portion between the connecting wall surface (911) and the main wall surface (912).
The tool body (3) according to claim 1.
The mounting seat (4) further has a second side wall surface (62),
The second side wall surface (62, 63) has an outer end located on the outer surface side and an inner end (621) opposite to the outer end, from the outer end to the inner end. Extending from the bottom wall surface over a portion, adjacent to the first side wall surface (61) with the second surface portion (9) in between,
The second surface portion (9) further includes a second connecting surface (913) connecting the main wall surface (912) and the second side wall surface (62), and the second surface portion (9 ) And the main wall surface (912) have a third curved surface (902), and at least part of the third curved surface (902) has a third radius of curvature in a cross section substantially parallel to the bottom wall surface. (R3)
The third radius of curvature (R3) is smaller than the first radius of curvature (R1).
Tool body (3) according to claim 2.
The tool body (3) according to claim 3, wherein the second radius of curvature R2 and the third radius of curvature R3 are substantially equal.
The tool body (3) according to any one of claims 1 to 4, wherein the first curvature radius R1 is 0.30 mm or more.
The tool body (3) according to any one of claims 1 to 5, wherein the second curvature radius R2 is less than 0.30 mm.
Cutting tool (1) having the tool body (3) according to any one of claims 1 to 6.