Chip and cutting tool

Abstract

To realize blade tip design and the like advantageous for improvements in sharpness and in chip discharging performance in BTA processing.SOLUTION: A chip 30 is attached to a body of a cutting tool 10, and comprises a tip 330 provided with a cutting edge CE and a rear end part 340 facing the same. At the tip 330, the cutting edge CE is formed into a step (stair) shape including a central edge 31 arranged on an inside surface 350 side and an outer peripheral edge 33 arranged on an outside surface 360 side. Further, In a rake face (second face 320) concerning the cutting edge CE, chip breakers B1, B3 are formed at parts corresponding to the central edge 31 and the outer peripheral edge 33, respectively. A maximum width W1max of the chip breaker B1 at the part corresponding to the central edge 31 is so made as to be larger than a maximum width W3max of chip breaker B3 at the part corresponding to the outer peripheral edge 33.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to a chip and a cutting tool including the chip.

Background Art

[0002] As one of the processing methods for forming deep holes in a workpiece, there is a processing method called "BTA" (Boring and Trepanning Association). Generally, in BTA machining, the chips generated by cutting are discharged to the outside through a discharge hole formed inside the cutting tool. For this reason, for example, a cutting tool is known that has a mechanism for dividing and subdividing chips on the center cutting edge side and the outer peripheral cutting edge side of the cutting edge by providing a step on the cutting edge of the chip to form a stepped shape. At that time, the chips on the center cutting edge side tend to be relatively thick, while the chips on the outer peripheral cutting edge side tend to be relatively thin and easy to extend. Therefore, in order to more suitably adjust the shape of the chips according to such a tendency, measures are required. As a candidate for a measure to meet such a requirement, a chip in which a step provided on the cutting edge is formed by a notch having a substantially V-shaped shape has been proposed (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above conventional chip, it is intended to suppress excessive stretching in the chips on the outer peripheral edge side by controlling the direction (stretching direction) in which the chips extend. However, as the chip shape control desired from the viewpoint of improving the cutting performance of the workpiece and the chip dischargeability in BTA machining, it has not yet been sufficiently solved. In particular, it is earnestly desired to favorably control the shape of relatively thin and easily extensible chips on the outer peripheral edge side.

[0005] Therefore, an object of the present disclosure is to provide a chip capable of suppressing excessive extension in relatively thin and easily extensible chips that can occur in BTA machining, and thereby realizing a cutting edge design and chip processing advantageous for improving the cutting performance and chip dischargeability in BTA machining, and a cutting tool provided with the chip.

Means for Solving the Problems

[0006] In order to solve the above problems, the present disclosure adopts the following configuration.

[0007] 〔1〕An example of the chip according to the present disclosure is, for example, a chip used for drilling a workpiece and attached to the body of a cutting tool. Specifically, the chip includes a tip portion provided with a cutting edge, a rear end portion facing the tip portion, a first side surface connecting the tip portion and the rear end portion, and a second side surface facing the first side surface. Further, at the tip portion, the cutting edge is formed in a stepped shape including a first cutting edge disposed on the first side surface side and a second cutting edge disposed on the second side surface side. Furthermore, on the rake face related to the cutting edge, a chip breaker is formed at a portion corresponding to each of the first cutting edge and the second cutting edge. And the maximum width of the chip breaker at the portion corresponding to the first cutting edge is made larger than the maximum width of the chip breaker at the portion corresponding to the second cutting edge.

[0008] Here, the "width of the chip breaker" in the present disclosure refers to the width along the direction (for example, but not limited to, the orthogonal direction) intersecting the extending direction of each cutting edge in the plan view of the chip, or refers to the width of the boundary between the cutting edge and the upper surface of the chip breaker (wall) facing the cutting edge.

[0009] In such a configuration, the cutting edge is formed in a step (staircase) shape, and a step is defined between the first cutting edge and the second cutting edge, so that the chips are segmented and fragmented. Also, due to the above relationship of the maximum width of the chip breaker at the parts corresponding to the first cutting edge and the second cutting edge respectively, with respect to the first cutting edge, the distance to the "wall" in the chip breaker becomes farther, so the action of forcibly curling the chips becomes weaker, and thereby, even if the chips are thick, they are easier to bend. On the other hand, with respect to the second cutting edge, the distance to the "wall" in the chip breaker becomes closer, so the action of forcibly curling the chips becomes stronger, and thereby, even if the chips are thin, they are moderately easy to be rounded or easily broken into small pieces. That is, according to the present disclosure, since the width of the chip breaker at the part corresponding to the second cutting edge is relatively narrower than the width of the chip breaker at the part corresponding to the first cutting edge, the curl diameter of the chips that are easy to extend thinly can be made smaller. As a result, it is possible to realize and provide a cutting edge design and chip processing that are advantageous for improving the cutting performance and chip dischargeability in BTA machining.

[0010] 〔2〕In the above configuration, the width of the chip breaker at the portion corresponding to the second cutting edge may be continuously or intermittently widened from the first side surface side toward the second side surface side. In such a configuration, there is an advantage that it becomes easier to further control the shape of the chips by the second cutting edge and thus the cutting edge. More specifically, as a feature of drilling, the cutting speed is substantially zero at the rotation center of the cutting tool, and the cutting speed increases toward the outer peripheral side. Therefore, the chips on the outer peripheral side flow relatively fast, and the chips on the center side tend to flow relatively slowly. At this time, when the chips are viewed from the rake face side, they curl into a fan shape with the center on the inside. Thus, when the width of the chip breaker corresponding to the cutting edge is constant (the same), the chips only hit the chip breaker as a "wall" on the outer peripheral side, whereas by widening the width of the chip breaker toward the outer peripheral side as in the above configuration (that is, making the chip breaker also fan-shaped), the chips can be made to hit the entire "wall".

[0011] Note that the "first side surface" side and the "second side surface" side of the chip in the present disclosure correspond to the "tool center side" and the "tool outer peripheral side", respectively, when the chip is attached to the cutting tool. From this, the configuration can also be expressed as that the width of the chip breaker at the portion corresponding to the first cutting edge continuously or intermittently increases from the tool center side toward the tool outer peripheral side.

[0012] 〔3〕In the above configuration, it is also preferable that a chamfered portion is formed between the second side surface and the outer peripheral edge at the tip portion. According to such a configuration, stress concentration on the outer surface side end portion of the outer peripheral edge can be relieved, and breakage of that portion can be prevented.

[0013] 〔4〕In the above configuration, it is also preferable that a recess is formed on the rake face, which has an inclined surface descending toward the rear end portion facing the tip end portion, and is connected to the coolant and chip discharge holes provided in the body of the cutting tool. In such a configuration, when the tip is attached to the body of the cutting tool, the recess is connected to the discharge hole of the body, and a path for discharging the coolant and chips from the tip side is defined. And since the recess has an inclined surface, the pressure loss when the coolant and chips flow is reduced, and their dischargeability is improved. As a result, it becomes easier to prevent chip jamming during BTA machining.

[0014] 〔5〕An example of the cutting tool according to the present disclosure can be effectively configured to include a body and a tip according to the present disclosure attached to the body. That is, the tip includes a tip end portion provided with a cutting edge, a rear end portion facing the tip end portion, a first side surface connecting the tip end portion and the rear end portion, and a second side surface facing the first side surface. At the tip end portion of the tip, the cutting edge is formed in a stepped shape including a first cutting edge disposed on the first side surface side and a second cutting edge disposed on the second side surface side. Further, on the rake face regarding the cutting edge, chip breakers are formed at positions corresponding to the first cutting edge and the second cutting edge respectively, and the maximum width of the chip breaker at the position corresponding to the first cutting edge is made larger than the maximum width of the chip breaker at the position corresponding to the second cutting edge.

Advantages of the Invention

[0015] According to the present disclosure, excessive elongation in relatively thin and easily extendable chips that can occur in BTA machining can be suppressed. As a result, it is possible to realize a cutting edge design and chip processing that are advantageous for improving the cutting performance and chip dischargeability in BTA machining.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0017] Hereinafter, the present embodiment will be described with reference to the accompanying drawings. For ease of understanding the description, the same components in each drawing are denoted by the same reference numerals as much as possible, and overlapping descriptions are omitted.

[0018] FIG. 1 is a perspective view showing an outline of the overall configuration of the cutting tool according to the present embodiment, and FIG. 2 is a perspective view showing a schematic configuration of a tip included in the cutting tool according to the present embodiment. Further, FIGS. 3(A) to (C) are a plan view (top view in FIGS. 1 and 2) schematically showing a tip included in the cutting tool according to the present embodiment, a left side (tip side) side view in FIG. 3(A), and a lower side (outer side) side view in FIG. 3(A), respectively. Furthermore, FIG. 4 reproduces FIG. 3(A) and is a plan view showing a slightly enlarged view of FIG. 3(A).

[0019] <Outline of the cutting tool 10> The cutting tool 10 according to the present embodiment is a cutting tool for BTA machining used for drilling. As shown in FIG. 1, the cutting tool 10 includes a body 20, a tip 30, and a guide pad 40. Among these, first, the body 20 is a member that generally constitutes the entire cutting tool 10 and is formed of, for example, steel.

[0020] As shown in Fig. 1, the tip 21 of the body 20 has a substantially cylindrical shape, a part of its side surface is cut away, and a chip 30 described later is attached to a seat 210 provided at that part. Also, the rear end 22 of the body 20 has a substantially cylindrical shape, similar to the tip 21, and is integrally formed with the tip 21. The cutting tool 10 is appropriately gripped by a machine tool (not shown) on the rear end 22 side, and is driven to rotate around the rotation center axis AX during BTA machining of the workpiece. The rotation center axis AX coincides with the center axis of the body 20 having a substantially cylindrical shape. Also, in Figs. 1 and 2, the rotation direction Y of the cutting tool 10 during BTA machining is indicated by a round arrow.

[0021] Further, a discharge hole 23 is formed in the body 20. The discharge hole 23 is a communication hole for guiding and discharging the coolant supplied along the outer peripheral surface of the body 20 to the outside together with the chips generated during BTA machining. This discharge hole 23 extends along the rotation center axis AX and is formed so as to penetrate the entire body 20. Also, the discharge hole 23 is a through hole having a substantially circular cross section, and its central axis generally coincides with the rotation center axis AX. Furthermore, in the connection portion to the chip 30 in the vicinity of the chip 30 described later, the inner surface of the discharge hole 23 is inclined so as to approach the rotation center axis AX toward the chip 30 side.

[0022] The chip 30 is a component having a cutting edge CE including a center cutting edge 31 (first cutting edge), an intermediate cutting edge 32, and an outer peripheral cutting edge 33 (second cutting edge) arranged in order from the inner surface 350 side (tool center side Rc) toward the outer surface 360 side (tool outer peripheral side Rp). The material of this chip 30 is not particularly limited, and for example, it is preferably entirely formed of cemented carbide. Further, at least a portion of the chip 30 including the cutting edge CE may be formed including, for example, hard materials such as cermet, ceramics, and sintered bodies containing cubic boron nitride, those having a coating layer formed on the surface of these hard materials by PVD or CVD, and single crystal diamond or sintered bodies containing diamond. Furthermore, the chip 30 is fixed to the seat 210 of the body 20 by, for example, brazing.

[0023] Also, for example, the plurality of guide pads 40 are members for suppressing deformation of the body 20 by contacting the inner surface of the machining hole (the hole formed in the workpiece as the cutting tool 10 rotates) during BTA machining. With these guide pads 40, the straightness and roundness of the machining hole can be improved.

[0024] In addition, when BTA machining is performed by the cutting tool 10, a coolant, which is a fluid, is supplied from the outside through the gap between the inner peripheral surface of the machining hole and the outer peripheral surface of the body 20. After reaching near the tip of the chip 30, the coolant flows into the discharge hole 23 of the body 20 together with the chips generated by BTA machining. The coolant and the chips then flow from the discharge hole 23 toward the rear end side and are discharged to the outside of the cutting tool 10.

[0025] <Specific Configuration of Chip 30> A more specific configuration of the chip 30 will be described below. As shown in FIG. 2, the chip 30 includes a first surface 310 (the lower surface shown in the figure), a second surface 320 (the upper surface shown in the figure, the rake face), a tip portion 330, a rear end portion 340, an inner surface 350 (the left surface shown in the figure, the first side surface), and an outer surface 360 (the right surface shown in the figure, the second side surface).

[0026] The first surface 310 is the surface facing the rear side in the rotational direction Y when the chip 30 is attached to the body 20. On the other hand, the second surface 320 is the surface facing the front side in the rotational direction Y when the chip 30 is attached to the body 20, and is the portion that is open and exposed in the notch of the body 20. That is, the second surface 320 is located on the opposite side to the first surface 310 and is the surface on the traveling direction side when the body 20 rotates around the rotation center axis AX. Also, as shown in FIG. 2, the second surface 320 has a portion parallel to the first surface 310.

[0027] The tip portion 330 is a portion connecting between the first surface 310 and the second surface 320, and is the most tip-side Rf portion in a state where the chip 30 is attached to the body 20. At this tip portion 330, a cutting edge CE for BTA machining is formed on a part of the intersection ridge line between the tip surface (relief surface) and the second surface 320 (rake surface).

[0028] Also, the rear end portion 340 is also a portion connecting between the first surface 310 and the second surface 320, and is the most rear end-side Rb portion in a state where the chip 30 is attached to the body 20. Note that the rear end portion 340 is a portion located on the opposite side facing the tip portion 330 in the direction along the rotation center axis AX, and is a surface that is substantially perpendicular and substantially flat with respect to the first surface 310.

[0029] <Tip portion 330 of chip 30> A more specific configuration of the tip portion 330 of the chip 30 will be described below. On the rake surface (second surface 320) regarding the cutting edge CE formed at the tip portion 330, chip breakers B1, B2, and B3 are formed at portions corresponding to the center cutting edge 31, the intermediate cutting edge 32, and the outer peripheral cutting edge 33, respectively. Also, in the cutting edge CE, the center cutting edge 31, the intermediate cutting edge 32, and the outer peripheral cutting edge 33 are formed in a plurality of stepped (staircase) shapes. Among the above ridge lines, in the plan view shown in Fig. 3(A) and Fig. 4, the portion C12 of the step C12 between the center cutting edge 31 and the intermediate cutting edge 32, and the portion C23 of the step C23 between the intermediate cutting edge 32 and the outer peripheral cutting edge 33 are not regarded as cutting edges. Note that the cutting edge CE can also be expressed as being formed in a serrated shape in the plan view shown in Fig. 3(A) and Fig. 4.

[0030] Furthermore, in the plan view shown in Fig. 3(A) and Fig. 4, the maximum width W1 of the chip breaker B1 at the portion corresponding to the center cutting edge 31 max , the maximum width W2 of the chip breaker B2 at the portion corresponding to the intermediate cutting edge 32 max , and the maximum width W3 of the chip breaker B3 at the portion corresponding to the outer peripheral cutting edge 33 max satisfy the relationship expressed by the following formula (1). W1 max >W2 max≧W3 max …(1)

[0031] At this time, in the shape design of the chip 30, the cutting edge CE is determined, and based on the cutting edge CE, the shapes of the chip breakers B1, B2, and B3 are determined. Then, when formulating the "wall" position in the chip breaker and the shape connecting the respective walls, the relationship expressed by the above formula (1) can be adjusted as appropriate so as to be satisfied.

[0032] Also, in the present embodiment, in FIGS. 2, 3(A) and (B), and FIG. 4, the center blade 31 is bent in a "Z" shape (a "く" shape) as shown in the figure and functions as a blade up to the vicinity of the rotation center axis AX. Therefore, the chip breaker B1 at the portion corresponding to the center blade 31 is also bent in a "Z" shape (a "く" shape) in the same manner. On the other hand, in the same view, the chip breaker B2 at the portion corresponding to the intermediate blade 32 and the chip breaker B3 at the portion corresponding to the outer peripheral blade 33 are regions each having a substantially trapezoidal shape in plan view. Thereby, both the width W2 of the chip breaker B2 and the width W3 of the chip breaker B3 are configured to continuously or intermittently increase from the inner surface 350 side (tool center side Rc) toward the outer surface 360 side (tool outer peripheral side Rp).

[0033] Furthermore, in the present embodiment, in the plan view shown in FIGS. 3(A) and 4, a step D12 is formed on the rear end portion 340 side between the chip breaker B1 at the portion corresponding to the center blade 31 and the chip breaker B2 at the portion corresponding to the intermediate blade 32. Thereby, the boundary portion T12 connecting between the chip breakers B1 and B2 has a constricted shape on both sides. In contrast, the boundary portion T23 connecting between the chip breakers B2 and B3 has a constricted shape on one side. Still further, in the present embodiment, in the plan view shown in FIGS. 3(A) and 4, a chamfered portion T34 that linearly connects (joins) the outer surface 360 exposed on the tool outer peripheral side Rp and the outer peripheral blade 33 is formed.

[0034] In addition, in the present embodiment, a concave portion E321 having an inclined surface 321 that recedes toward the first surface 310 (descends toward the rear end portion 340 facing the tip portion 330) is formed in a portion of the second surface 320 on the rear end portion 340 side. The concave portion E321 is smoothly connected to the coolant and chip discharge hole 23 provided in the body 20 without a step on the rear end portion 340 side. Further, inclined surfaces 322 that are inclined in the same direction as the inclined surface 321 are provided on both sides of the concave portion E321.

[0035] According to the chip 30 configured as described above and the cutting tool 10 to which the chip 30 is attached, the cutting edge CE is formed in a step (staircase) shape, and steps C12 and C23 are defined at the boundary portions T12 and T23 between adjacent blades of the center blade 31, the intermediate blade 32, and the outer peripheral blade 33. Therefore, the chips generated by the BTA machining using the cutting tool 10 are fragmented into small pieces by being divided at the portions of the steps C12 and C23. At this time, since a plurality of steps C12 and C23 are defined, the chips can be divided more finely than in the case where there is a single step.

[0036] In addition, the maximum width W1 of the chip breaker B1 at the portion corresponding to the center blade 31 max is larger than the maximum widths W2 max , W3 max of the chip breakers B2 and B3 at the portions corresponding to the intermediate blade 32 and the outer peripheral blade 33, respectively (see the above formula (1)). As a result, with respect to the center blade 31, the distance to the "wall" in the chip breaker B1 becomes longer, so the action of forcibly curling the chip is weakened, and as a result, even if the chip is thick, it is easily bent. On the other hand, with respect to the intermediate blade 32 and the outer peripheral blade 33, the distance to the "wall" in the chip breakers B2 and B3 is closer than in the case of the chip breaker B1 corresponding to the center blade 31, so the action of forcibly curling the chip is strengthened. As a result, even if the chip is thin, it is easily curled appropriately, or it is easily broken into small pieces. From the above, it is possible to realize and provide a cutting edge design and effective chip processing that are advantageous for improving the cutting performance and chip dischargeability in BTA machining.

[0037] Furthermore, the widths W2 and W3 of the chip breakers B2 and B3 at the portions corresponding to the intermediate cutting edge 32 and the outer peripheral cutting edge 33 are configured to continuously or intermittently increase from the inner surface 350 side (tool center side Rc) toward the outer surface 360 side (tool outer peripheral side Rp). Generally, in BTA machining, when the chips are viewed from the second surface 320 (rake face) side, they curl into a fan shape with the center on the inner side. Therefore, when the widths of the chip breakers B1, B2, and B3 corresponding to the cutting edge CE are constant (the same), the chips only hit the chip breaker as a "wall" on the outer peripheral side. On the contrary, as in the configuration of the present embodiment, by gradually widening the widths W2 and W3 of the chip breakers B2 and B3 toward the outer surface 360 side (tool outer peripheral side Rp) (that is, making the chip breakers also fan-shaped), the chips can be applied to the entire "wall". As a result, it becomes easier to control the shape of the chips by the intermediate cutting edge 32 and the outer peripheral cutting edge 33, and thus the cutting edge CE.

[0038] Moreover, at the tip portion 330, a chamfered portion T34 that linearly connects (joins) the outer surface 360 and the outer peripheral cutting edge 33, for example, is provided, so that stress concentration at the side end portion of the outer surface 360 of the outer peripheral cutting edge 33 is effectively alleviated. Thereby, breakage at that portion can be prevented.

[0039] Furthermore, generally, in a cutting tool used for BTA machining, as in the cutting tool 10 according to the present embodiment, in order to reliably discharge the chips, the inlet of the discharge hole 23 is often provided as close as possible to the cutting edge CE of the chip 30. For this reason, the inlet of the discharge hole 23 is narrowed by the chip 30, and it becomes difficult for the coolant containing the chips to flow into the discharge hole 23. In that case, in some cases, chips may clog at the inlet of the discharge hole 23. On the contrary, according to the present embodiment, since the concave portion E321 is provided on the second surface 320 of the chip 30, a wide discharge path for the coolant to flow toward the discharge hole 23 is ensured. Thereby, since the inlet of the discharge hole 23 is not narrowed by a part of the chip 30, the pressure loss when the coolant and the chips flow is reduced, and it becomes easier to prevent clogging of the chips during BTA machining.

[0040] The above has described this embodiment while referring to specific examples, but it is for facilitating the understanding of the present disclosure and not for limiting the interpretation of the present disclosure. That is, the present disclosure is not limited to these specific examples, and those obtained by appropriately making design changes to these specific examples by those skilled in the art are also included in the scope of the present disclosure as long as they have the features of the present disclosure. In addition, each element, arrangement, material, condition, shape, dimensional size, scale, etc. provided in each of the above-described specific examples are not limited to those illustrated unless otherwise specified, and can be changed as appropriate. Furthermore, each element provided in each of the above-described specific examples can be changed in combination as appropriate unless a technical contradiction occurs.

[0041] That is, for example, if the center blade 31 and the outer peripheral blade 33 are provided, the intermediate blade 32 may not be provided. Also, the shape of the tip portion 330 and the shapes of the center blade 31, the intermediate blade 32, and the outer peripheral blade 33 constituting the cutting edge CE may of course be different from those shown in the figures. Furthermore, in the above embodiment, the "width of the chip breaker" is shown in FIG. 4 as the width along the direction orthogonal to the extending direction of the center blade 31, the intermediate blade 32, and the outer peripheral blade 33 in the plan view of the chip. However, as described above, the "width of the chip breaker" in the present disclosure is not limited to the illustration as long as it is a direction intersecting the extending direction thereof. Also, for example, the width of the boundary portion between the cutting edge CE and the upper surfaces of the chip breakers B1, B2, B3 (walls) facing it may be defined as the "width of the chip breaker". Additionally, in the above embodiment, the case where the extending directions of the center blade 31, the first outer peripheral blade 32, and the second outer peripheral blade 33 are substantially the same is illustrated, but this is also not limited to the illustration.

[0042] In addition, as the chip breakers B1, B2, and B3, it is only necessary to have a functional shape as a "wall", and for example, it may be formed as a part having grooves, islands, or the like. Further, the chip 30 may be detachably fastened and fixed to the seat 210 of the body 20 by screws. In this case, the chip 30 is used as a "cutting insert". Furthermore, in the plan view of FIG. 4, the shape of the boundary portion T12 connecting the chip breakers B1 and B2 can be arbitrarily adjusted. In the above embodiment, the left and right sides shown in the figure are curved and bulging like steps C12 and D12, but for example, they may be straight lines or broken lines, and the step D12 may not be provided. Similarly, the shape of the boundary portion 31 connecting the chip breakers B2 and B3 can also be arbitrarily adjusted. In the above embodiment, the left and right sides shown in the figure are straight lines without curves or steps like the step C23, but for example, both may be straight lines, or steps like the step D12 may be provided to form a bulging shape on both sides. In addition, in the plan view of FIG. 4, the chamfered portion T34 connecting the outer surface 360 and the outer peripheral edge 33 is linear, but as long as it helps to prevent damage to the end portion of the outer peripheral edge 33 on the outer surface 360 side, it may be curved or have other shapes.

Explanation of Signs

[0043] 10... cutting tool, 20... body, 21... tip, 22... rear end, 23... discharge hole, 30... chip, 31... center edge (first cutting edge), 32... intermediate edge, 33... outer peripheral edge (second cutting edge), 40... guide pad, 210... seat, 310... first surface, 320... second surface (rake face), 321... inclined surface, 322... inclined surface, 330... tip, 340... rear end, 350... inner surface (first side), 360... outer surface (second side), AX... rotation center axis, B1, B2, B3... chip breakers, C12, C23... steps, CE... cutting edge, D12... step, E321... recess, Rb... rear end side, Rc... tool center side, Rf... tip side, Rp... tool outer peripheral side, T12, T23... boundary portions, T34... chamfered portion, W1, W2, W3... widths of the chip breakers, W1 max , W2 max , W3 max ,... maximum width of the chip breaker, Y... rotation direction.

Claims

1. A tip used for drilling, comprising: a tip portion provided with a cutting edge, a rear end portion facing the tip portion, a first side surface connecting the tip portion and the rear end portion, and a second side surface facing the first side surface; At the tip portion, the cutting edge is formed in a stepped shape including a first cutting edge disposed on the first side surface side and a second cutting edge disposed on the second side surface side; On the rake face related to the cutting edge, chip breakers are formed at positions corresponding to the first cutting edge and the second cutting edge respectively; The maximum width of the chip breaker at the position corresponding to the first cutting edge is larger than the maximum width of the chip breaker at the position corresponding to the second cutting edge; Tip.

2. The tip according to claim 1, wherein the width of the chip breaker at the position corresponding to the second cutting edge becomes wider continuously or intermittently from the first side surface side toward the second side surface side.

3. The tip according to claim 1 or 2, wherein at the tip portion, a chamfered portion is formed between the second side surface and the second cutting edge.

4. The tip according to any one of claims 1 to 3, wherein the rake face has an inclined surface descending toward the rear end portion facing the tip portion, and a recess is formed which is connected to a coolant and chip discharge hole provided in the body of the cutting tool.

5. A body, a tip attached to the body, and comprising: the tip includes a tip portion provided with a cutting edge, a rear end portion facing the tip portion, a first side surface connecting the tip portion and the rear end portion, and a second side surface facing the first side surface; At the tip portion of the tip, the cutting edge is formed in a stepped shape including a first cutting edge disposed on the first side surface side and a second cutting edge disposed on the second side surface side; On the rake face related to the cutting edge, chip breakers are formed at positions corresponding to the first cutting edge and the second cutting edge respectively; The maximum width of the chip breaker at the position corresponding to the first cutting edge is larger than the maximum width of the chip breaker at the position corresponding to the second cutting edge; Cutting tool.

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