Cutting tool

Abstract

To provide a cutting tool capable of avoiding interference with a machining surface, while restraining reduction in rigidity and joining strength, damage and the occurrence of chattering, especially for a cutting insert used for copying work and finishing work.SOLUTION: The cutting tool includes a base insert member 10 extending along a longitudinal direction, and a cutting edge member 20 provided at a longitudinal end of the base insert member 10. Cutting edge member 20 includes a rake face 22, a flank face, an arc-shaped cutting edge 26, a breaker wall 28, and a boss portion 30 including a boss face 32. The central angle of the cutting edge 26 is ≥180°, and at least a part of the edge parts 11, 21 behind the cutting edge 26 along the longitudinal direction is chamfered.SELECTED DRAWING: Figure 15

Description

[Technical Field]

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

[0002] Cutting inserts with arc-shaped cutting edges made of cemented carbide are sometimes used as cutting tools for copy milling and finishing (see, for example, Patent Documents 1 to 3). For machining high-hardness materials, cutting inserts with cutting edges made of sintered bodies containing cBN (cubic boron nitride), which is even harder than cemented carbide, are sometimes used. When using such cutting inserts for finishing, for example, the depth of cut is typically around 0.2 mm, which is significantly lower than that of cemented carbide inserts.

[0003] In copy cutting using a cutting insert with the above-described cutting edges, it is important that the bonding area of ​​the cutting edges is large in order to ensure bonding strength and insert rigidity, and to prevent damage to the insert and chatter. In this regard, simply replacing the cutting edge portion of an insert with a central angle of more than 180° with a sintered body containing cBN, as disclosed in Patent Documents 1 to 3, makes it difficult to ensure the bonding area of ​​the brazed portion. From this perspective, it can be said that the central angle of the cutting edges is preferably about 180°. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5592954 [Patent Document 2] Patent No. 5262528 [Patent Document 3] U.S. Patent No. 9,579,727 Summary of the Invention [Problem to be solved by the invention]

[0005] However, simply setting the cutting edge central angle to approximately 180° as described above can result in other problems, such as the following. Specifically, when the flank of such a cutting insert is positive, the clearance between the edge located higher than the cutting edge and the machined surface is narrow, which could lead to interference with the machined surface during machining. Furthermore, if the edge remains in its edge shape, there is a concern that sudden breakage may occur due to chip bite. One possible solution to this issue is to machine the edge so that its height is flush with the rake face, similar to the breaker machining area. However, this requires machining the brazed portion of the base insert and the cutting edge, which could result in a reduced joint area and insufficient joint strength. Another way to avoid edge interference is to increase the back taper. However, this inevitably narrows the insert width around the brazed portion, resulting in a reduced joint area and insufficient joint strength. Furthermore, as described above, this reduces the insert's rigidity, potentially leading to insert breakage or chatter.

[0006] Therefore, the present invention aims to provide a cutting tool that is particularly targeted at cutting inserts used in copy machining and finishing machining, and that can avoid interference with the machining surface while suppressing a decrease in rigidity and bonding strength, breakage, and the occurrence of chatter. [Means for solving the problem]

[0007] One aspect of the present invention is a cutting tool having a base insert member extending along a longitudinal direction and a cutting edge member provided at an end of the base insert member in the longitudinal direction, The cutting edge material is The scooping surface and The relief surface and A cutting edge that is formed at an intersection line between a rake face and a flank and has an arc shape when viewed from above from the side where the rake face is located; a breaker wall formed inside the cutting edge and protruding upward from the cutting tool; a boss portion including a boss surface formed continuously with the breaker wall; Equipped with The central angle of the cutting edge is 180° or more, A cutting tool in which at least a portion of the edge rearward of the cutting edge along the longitudinal direction is chamfered.

[0008] With a cutting tool of the above-described type, simply by chamfering the edge portion behind the cutting edge, it is possible to avoid interference with the machining surface without causing problems such as insufficient bonding strength due to a reduced bonding area, reduced insert rigidity, breakage, or chattering.

[0009] In the cutting tool as described above, the edge portion may be chamfered.

[0010] In the cutting tool described above, the chamfered region may include a virtual edge that is the intersection line between the boss surface and the flank surface.

[0011] In the cutting tool as described above, the edge portion may be present on both the base insert member and the cutting edge member.

[0012] In the cutting tool described above, the central angle of the cutting edge may be 185° or less.

[0013] In the cutting tool as described above, a back taper may be provided between the cutting edge and the edge portion, the width of which gradually decreases toward the edge portion.

[0014] In the cutting tool as described above, the joint between the base insert member and the cutting edge member may be stepped in side view.

[0015] In the cutting tool as described above, the joint portion between the base insert member and the cutting edge member may be wavy when viewed from above.

[0016] The cutting tool as described above may be a cutting insert comprising a base insert member made of cemented carbide and a cutting edge member made of a sintered body containing cBN. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a perspective view showing an example of a cutting tool according to an embodiment of the present invention. [Figure 2] FIG. [Figure 3] FIG. [Figure 4] FIG. [Figure 5] FIG. 2 is an enlarged perspective view of a cutting edge member of the cutting tool. [Figure 6] FIG. 2 is an enlarged top view showing a part of a cutting edge member of the cutting tool. [Figure 7] FIG. 2 is an enlarged perspective side view of a cutting edge member of the cutting tool. [Figure 8] FIG. 4 is a schematic view showing the flow of coolant in the cutting edge member. [Figure 9] FIG. 4 is a diagram showing a cross-sectional shape of a cutting edge member. [Figure 10] FIG. 10 is an enlarged perspective view of a cutting edge member, showing another example of a cutting tool. [Figure 11] FIG. 10 is an enlarged perspective view of a cutting edge member, showing yet another example of a cutting tool. [Figure 12] FIG. 10 is a schematic perspective view for explaining, for reference, the flow of coolant in a cutting edge member in which a recess is not formed in a boss portion. [Figure 13] FIG. 10 is a schematic side view for explaining, for reference, the flow of coolant in a cutting edge member in which a recess is not formed in a boss portion. [Figure 14] 10 is a top view of a cutting edge member for explaining the central angle α of the cutting edge, the back taper, etc. [Figure 15] FIG. 10 is a diagram showing a comparison between (A) a partially chamfered edge portion and (B) a non-chamfered edge portion. DETAILED DESCRIPTION OF THE INVENTION

[0018] A preferred embodiment of the cutting tool according to the present invention will be described in detail below with reference to the drawings (see Figs. 1 to 9, etc.). In the following, a cutting insert 1 consisting of a base insert member 10 and a cutting edge member 20 will be described as an example of a preferred embodiment. In the following, the longitudinal direction of the base insert member 10 (the direction along the central axis X) will be referred to as the "front-rear direction," the left-right direction in Fig. 2 as the "width direction," and the upper side in Fig. 2 (the side on which a boss portion 30, which will be described later, is located) will be referred to as the "top," and the "bottom" in Fig. 2 will be described.

[0019] [Cutting insert structure] The base insert member 10 is a member that holds the brazed cutting edge member 20 (see FIGS. 1 to 4). The base insert member 10 in this embodiment is made of a superhard material and is formed into a shape that extends along the central axis 10X.

[0020] The cutting edge member 20 is a member formed of a sintered body containing cBN (cubic boron nitride), which is even harder than cemented carbide, and is brazed to the end of the base insert member 10 to form the cutting insert 1. The cutting edge member 20 of this embodiment has a rake face 22, a flank face 24, a cutting edge 26, a breaker wall 28, a boss portion 30, a boss face 32, a depression 34, a recess 36, a groove 38, etc. (see FIG. 1, etc.).

[0021] The cutting edge 26 is formed at the intersection of the rake face 22 and the clearance face 24. In this embodiment, the cutting edge 26 of the cutting edge member 20 is formed in a substantially semicircular arc shape when viewed from above from the side where the rake face 22 of the cutting edge member 20 is located (see FIG. 3, etc.). The central angle α of the substantially arc-shaped cutting edge 26 is slightly greater than 180°, for example, approximately 185°. When the central angle α is 185°, the left and right angles about the central axis 10X are α / 2, or 92.5° (see FIG. 14). The rear of the cutting edge 26, the relief portion near the base insert member 10, is called a back taper, which gradually decreases from the maximum width of the cutting edge 26 (indicated by the reference symbol 40 in FIG. 14). The relief angle β of the back taper 40 (the angle relative to a line parallel to the central axis 10X) is, for example, 2.5° (see FIG. 14). Incidentally, in a front view of the cutting insert 1 seen from the tip end side of the base insert member 10 along the central axis 10X, the back taper 40 is hidden and cannot be seen (see Figs. 2, 3, etc.). In Fig. 3, etc., the approximate center of the cutting edge 26, which is approximately arc-shaped as described above, is indicated by the reference symbol 22c. Although not shown in detail, the cutting edge 26 may be chamfered by honing.

[0022] The rake face 22 is formed on the upper surface side of the cutting edge member 20 along the substantially arc-shaped cutting edge 26. The flank face 24 is formed on the side surface of the cutting edge member 20 along the substantially arc-shaped cutting edge 26 as a positive surface that slopes toward the lower surface as it moves away from the cutting edge 26.

[0023] The breaker wall 28 is formed inside the cutting edge 26 so as to protrude above the cutting edge member 20. The breaker wall 28 in the cutting edge member 20 of this embodiment is generally arc-shaped overall, and is divided into multiple sections by multiple recesses 36, which will be described later (see FIGS. 1, 5, etc.). In the cutting edge member 20 of this embodiment, the distance between the breaker wall 28 and the cutting edge 26 (referred to as the breaker width, and indicated by the symbol Wb in FIG. 9) is uniform, and the surface of the breaker wall 28 has a shape similar to the peripheral surface of a truncated cone (see FIG. 7, etc.).

[0024] The boss portion 30 is formed as a top portion that protrudes above the breaker wall 28. A boss surface 32 is formed on the upper side of the boss portion 30 (see FIGS. 5, 6, etc.). The boss surface 32 may be chamfered (in FIG. 5, the chamfered portion is indicated by reference numeral 32c). The boss portion 30 of the cutting edge member 20 of this embodiment has an overall shape resembling a semicircular truncated cone with a small thickness (height). The boss surface 32, which is the upper surface of the boss portion 30, is divided into multiple portions by multiple recesses 36, which will be described later (see FIGS. 1, 5, etc.). The inside of an arc-shaped depression 34, which will be described later, forms a central boss portion (the portion of the boss portion 30 near the approximate center portion 22c) (see FIG. 5, etc.).

[0025] The recesses 36 are formed in the boss portion 30 so as to extend toward the cutting edge 26, improving the supply of coolant C to the cutting edge 26 (see FIG. 5, etc.). Compared to the flow of coolant C' in a cutting edge member 20' in which no recesses are formed in the boss portion 30' (see FIGS. 12 and 13), the amount of coolant C supplied to the cutting edge 26 can be increased by passing through the grooves 38 formed by the recesses 36 (see FIGS. 7 and 8). These recesses 36 are preferably formed to more efficiently supply coolant C to the cutting edge 26. In the cutting edge member 20 of this embodiment, the recesses 36 are formed radially from the central boss portion 30c. These recesses 36 are formed as linear grooves with a constant width when viewed from above (see FIGS. 3 and 6). Furthermore, in the cutting edge member 20 of this embodiment, the height of the bottom surface 36b of the recesses 36 is lower than the height of the cutting edge 26 when viewed from the front or side (see FIGS. 8 and 9). In this case, when chips are generated, the coolant gets into the gap between the chips and the rake face 22, making it easier to deliver the coolant to the cutting point.

[0026] Here, in the cutting edge member 20 of this embodiment, the width W of the breaker wall 28 28 The width W of the groove 38 formed by the recess 36 is 38 Larger shape (width W of breaker wall 28) 28 >Width W of the groove 38 formed by the recess 36 38) (see FIG. 5, etc.). In the case of such a shape, the area where the breaker wall 28 is located is more dominant than the area where the groove 38 is located with respect to the cutting edge 26, so that the coolant C can be supplied to the groove 38 formed by the recess 36, and stable chip disposal can be achieved by the effect of the breaker wall 28. 28 " and "The width W of the groove 38 formed by the recess 36 38 There are various ways to define "," but as an example, in this embodiment, it is defined as follows. That is, first, consider the intersection line L1 (which includes a virtual intersection line or a virtual extension of the intersection line; the same applies below) between the boss surface 32 and the breaker wall 28. In this embodiment, the chamfered portion 32c described above is considered to be included in part of the boss surface 32, and a virtual intersection line L1 between the boss surface (including the chamfered portion 32c) 32 and the breaker wall 28 is assumed (see FIG. 5). The width of the breaker wall 28 along the intersection line L1 and the width of the groove 38 formed by the recess 36 along the intersection line L1 are defined as the respective widths, and are denoted by the symbol W 28 ,W 38 The width W of the breaker wall 28 thus defined is expressed as 28 and the width W of the groove 38 formed by the recess 36 38 As mentioned above, the width W of the breaker wall 28 28 >Width W of the groove 38 formed by the recess 36 38 and in some cases, the width W of the breaker wall 28 28 The width W of the groove 38 formed by the recess 36 38 In the finishing process assumed to be used in this embodiment, the cutting depth and feed rate are small, so the width W of the breaker wall 28 28 The width W of the groove 38 formed by the recess 36 38 If the width is less than twice the width of the breaker wall 28, the breaker wall 28 may not function sufficiently, resulting in poor chip control.

[0027] The recess 34 is formed so as to be continuous with the recess 36. The recess 34 is formed in a substantially arc shape around the central boss portion 30c, which is the center of the cutting edge 26, so that the coolant C that has entered the recess 34 can flow out into the connected recess 36.

[0028] [Edge structure] In the cutting insert 1 of this embodiment, the edge portions 11, 21 may be present at a position higher from the bottom surface than the cutting edge 26 behind the cutting edge 26 (i.e., on the base insert member 10 side) along the longitudinal direction (the same as the axial direction of the central axis 10X) (see FIG. 15(B) . The edge portion on the base insert member 10 side is indicated by reference numeral 11, and the edge portion on the cutting edge member 20 side is indicated by reference numeral 21). The edge portions 11, 21 present at a position higher than the cutting edge 26 have a narrow clearance with the machining surface (indicated by reference numeral WS in FIG. 15 ), and as described above, there is a risk that the edge portions 11, 21 may interfere with the machining surface WS during machining. In this regard, in this embodiment, the edge portions 11, 21 are partially chamfered to prevent interference with the machining surface (see FIG. 15(A) . In the figure, the chamfered portions are indicated by reference numerals 11C, 21C). The presence of the chamfered portions 11C, 21C means that the virtual edge (denoted by the symbol VE) between the boss surface 32 and the flank 24 is eliminated, resulting in the edge portions 11, 21 being recessed accordingly. With this cutting insert 1, simply chamfering the edge portions 11, 21 behind the cutting edge 26 can prevent interference with the machined surface WS without causing problems such as insufficient joint strength, reduced rigidity, breakage, or chatter due to a reduced joint area when the cutting edge member 20 is brazed to the base insert member 10. The joint between the base insert member 10 and the cutting edge member 20 may be stepped in side view (see FIG. 4, etc.) or wavy in top view. Increasing the joint area in this manner can increase joint strength.

[0029] The chamfered portions 11C, 21C of the edge portions 11, 21 may be formed when the cutting insert 1 or the base insert member 10 is molded, or may be formed afterward by removing the chamfered portions after molding. Note that Fig. 15 also shows the back taper 40 described above. The back taper 40 has a shape in which its width gradually decreases toward the edge portions 11, 21 (see Fig. 15).

[0030] The above-described embodiment is one example of a preferred embodiment of the present invention, but is not limited to this, and various modifications are possible within the scope of the present invention. For example, in the above-described embodiment, the present invention is applied to the cutting insert 1 having the cutting edge member 20 brazed to the base insert member 10, but this is also merely a preferred example, and it goes without saying that the present invention can be applied to cutting tools other than such cutting insert 1.

[0031] In the above-described embodiment, the cutting edge member 20 has a uniform distance (breaker width Wb) between the breaker wall 28 and the cutting edge 26 (see FIG. 7 ). However, the distance (breaker width Wb) between the breaker wall 28 and the cutting edge 26 may be non-uniform. A specific example of a cutting edge member 20 having a non-uniform breaker width Wb is one in which two protrusions 28g are provided on the breaker wall 28 (see FIG. 10 ). By providing such protrusions 28g and setting the optimal breaker width WB depending on the position of the cutting edge 26 to be used, better chip disposal is possible. Alternatively, the boss portion 30 may have a small recess 37 in the shape of a notch, separate from the recess 36 (see FIG. 11 ). In this case, coolant C is also supplied from the small recess 37, allowing more coolant C to be supplied toward the cutting edge 26. [Industrial Applicability]

[0032] The present invention is suitable for application to cutting tools. [Explanation of symbols]

[0033] 1...Cutting insert (cutting tool) 10...Base insert member 10X…center axis 11...Edge 11C...Beveled part 20...Cutting edge material 21...Edge 21C...Beveled part 22...Scooping surface 22c…approximately central part 24...flank 26...(arcuate) cutting edge 28...Breaker Wall 28g…Protrusion 30...Boss section 30c...Central boss 32...Boss stage 32c...Beveled part 34...(arc-shaped) depression 36...(multiple) recesses 36b...Bottom of recess 37...Small recess 38... (recessed) groove 40...Back taper C...Coolant L1: Intersection line between boss surface and breaker wall W 28 …Width of breaker wall 28 along intersection line L1 W 38 ...width of the groove 38 formed by the recess 36 along the intersection line L1 Wb...breaker width (distance between breaker wall 28 and cutting edge 26) WS...machined surface α...Cutting edge central angle β…Back taper relief angle

Claims

1. A cutting tool having a base insert member extending along a longitudinal direction and a cutting edge member provided at an end of the base insert member in the longitudinal direction, The cutting edge member is The scooping surface and The relief surface and A cutting edge that is formed on an intersection line between the rake face and the flank and has an arc shape when viewed from above from the side where the rake face is located; a breaker wall formed inside the cutting edge and protruding upward from the cutting tool; a boss portion including a boss surface formed continuously with the breaker wall; Equipped with The central angle of the cutting edge is 180° or more, A cutting tool wherein at least a portion of an edge rearward of the cutting edge along the longitudinal direction is chamfered.

2. The cutting tool of claim 1 , wherein the edge is chamfered.

3. The cutting tool according to claim 1 , wherein the chamfered region includes a virtual edge that is an intersection line between the boss surface and the flank surface.

4. The cutting tool according to claim 1 , wherein the edge portion is present on both the base insert member and the cutting edge member.

5. The cutting tool according to claim 1 , wherein the central angle of the cutting edge is 185° or less.

6. The cutting tool according to claim 5 , further comprising a back taper between the cutting edge and the edge portion, the width of which gradually decreases toward the edge portion.

7. The cutting tool according to claim 1 , wherein a joint between the base insert member and the cutting edge member has a stepped shape in a side view.

8. The cutting tool according to claim 1 , wherein a joint portion between the base insert member and the cutting edge member has a wavy shape when viewed from above.

9. 4. The cutting tool according to claim 1, wherein the cutting insert comprises a base insert member made of cemented carbide, and the cutting edge member made of a sintered body containing cBN.

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