Drill and method for manufacturing cut article

Abstract

Provided is a drill that has excellent cutting blade durability and chip discharge. A cutting blade that is provided to a body of the drill has a chisel edge, a first blade, and a second blade. In plan view from a direction along the rotation axis, a boundary section where a boundary between the first blade and the second blade is located has a protruding shape toward the leading side in the rotation direction. The first blade has a first honing surface, the second blade has a second honing surface, and the chisel edge has a third honing surface. In plan view from a direction along the rotation axis, the width of the third honing surface decreases toward the outer periphery of the body, and the width of the first honing surface at the boundary section is smaller than the maximum value of the width of the first honing surface.

Description

Method for manufacturing drills and cuttings

[0001] The present disclosure relates to a drill used for cutting a workpiece and a method for manufacturing a cut product.

[0002] Conventionally, drills described in Patent Documents 1 and 2 are known as drills used for cutting workpieces such as metal components. Both of the drills described in Patent Documents 1 and 2 have a honing surface formed on the cutting edge. In the drill described in Patent Document 1, the width of the honing surface (honing width) at the bottom of the concave arc is set small to reduce the cutting load on the concave arc cutting edge. In the drill described in Patent Document 2, the width of the honing surface near the leading edge is set large to suppress chipping and breakage near the leading edge located on the outer periphery of the drill.

[0003] JP 2016-002617 A JP 2023-068305 A

[0004] A non-limiting example of a drill according to the present disclosure includes a body extending from a tip to a rear end and configured to rotate around a rotation axis with the axis serving as the rotation axis. The body has a cutting edge located near the tip and an ejection flute extending from the cutting edge toward the rear end. The cutting edge has a chisel edge that intersects with the rotation axis, a first cutting edge extending from the chisel edge toward the outer periphery of the body, and a second cutting edge extending from the first cutting edge toward the outer periphery of the body. In a plan view along the rotation axis, a boundary between the first cutting edge and the second cutting edge has a convex shape that faces forward in the direction of rotation around the rotation axis. The first cutting edge has a first honing surface, the second cutting edge has a second honing surface, and the chisel edge has a third honing surface. In a plan view along the rotation axis, the width of the third honing surface decreases toward the outer periphery of the body, and the width of the first honing surface at the boundary is smaller than the maximum value of the width of the first honing surface.

[0005] 1. A perspective view showing a drill according to an embodiment of the present disclosure. 2. A perspective view showing an insert in the drill shown in FIG. 1. 3. A front view of the tip side of the insert shown in FIG. 2, viewed from above in a direction along the rotation axis. 4. An enlarged view of region B shown in FIG. 3. 5. A cross-sectional view of the V-V line cross section in FIG. 4. 6. A cross-sectional view of the VI-VI line cross section in FIG. 4. 7. A cross-sectional view of the VII-VII line cross section in FIG. 4. 8. A cross-sectional view of the VIII-VIII line cross section in FIG. 4. 9. A cross-sectional view of the IX-IX line cross section in FIG. 4. 10. A cross-sectional view of the X-X line cross section in FIG. 4. 11. A cross-sectional view of the XI-XI line cross section in FIG. 4. 12. A cross-sectional view of the XII-XII line cross section in FIG. 4. 13. A cross-sectional view of the XIII-XIII line cross section in FIG. 4. 14. A cross-sectional view of the XIV-XIV line cross section in FIG. 4. 15. A graph plotting measurements of the honing width of the tip of the cutting edge of the drill shown in FIG. 1, as viewed from the front, at multiple points. 16. A diagram showing measurement points on the horizontal axis of the graph shown in FIG. 15. 17. A schematic diagram showing one step of a method for producing a machined product according to an embodiment of the present disclosure.

[0006] The drill described in Patent Document 1 focuses on reducing the cutting load and does not consider chip evacuation performance. Therefore, it is difficult to balance the cutting load and chip evacuation performance and improve chip evacuation performance while reducing the cutting load. Furthermore, the drill described in Patent Document 2 focuses on preventing elongated chips from wrapping around the drill to improve chip evacuation performance, and does not consider reducing chip clogging.

[0007] Therefore, there is a lot of room for improvement in terms of both the durability of the cutting edge and the chip discharge performance.

[0008] A drill according to an embodiment of the present disclosure will be described in detail below with reference to the drawings. However, for the sake of convenience, the drawings referred to below show only the main components of the embodiment that are necessary for explaining the example of the present disclosure in a simplified form. Therefore, the drill according to the present disclosure may include any components not shown in the drawings. Furthermore, the dimensions of the components in the drawings do not faithfully represent the actual dimensions of the components, the dimensional ratios of the components, etc.

[0009] <Schematic Configuration of Drill> A schematic configuration of a drill 1 according to this embodiment will be described with reference to Figures 1 to 3. Figure 1 is a perspective view showing a drill according to an embodiment of the present disclosure. Figure 2 is a perspective view showing an insert 1a in the drill 1 shown in Figure 1. Figure 3 is a front view of the tip side of the insert 1a shown in Figure 2 as viewed from a plane along the rotation axis O1.

[0010] As shown in FIG. 1 , a drill 1 according to an embodiment of the present disclosure may have a body 3 extending from a leading end 3a to a rear end 3b and configured to rotate around a rotation axis O1, with its axis serving as a rotation axis O1. The body 3 in this embodiment may have a rod shape extending from the leading end 3a to the rear end 3b. The body 3 in this embodiment may include a gripping portion 5 called a shank that is gripped by a rotating spindle or the like of a machine tool, and a cutting portion 7 called a body located at the leading end of the gripping portion 5. The gripping portion 5 is a portion designed according to the shape of the spindle or the like of the machine tool. The cutting portion 7 is a portion that comes into contact with a workpiece and plays a primary role in cutting the workpiece. An arrow Y1 indicates the rotation direction of the drill 1 (body 3) that rotates around the rotation axis O1.

[0011] The cutting portion 7 (main body 3) may have a cutting edge 11 located on the side of the tip 3a, an exhaust groove 13 extending from the cutting edge 11 toward the rear end, and a clearance surface 9 located behind the cutting edge 11 in the rotational direction Y1.

[0012] The number of cutting edges 11, discharge flutes 13, and flanks 9 is not limited to a specific number. In the non-limiting example shown in Fig. 1, the cutting portion 7 has three flanks 9, three cutting edges 11, and three discharge flutes 13, which is a so-called three-flute drill configuration. There is no problem if the cutting portion 7 has two flanks 9, two cutting edges 11, and two discharge flutes 13, which is a so-called two-flute drill configuration.

[0013] In the drill 1 of this embodiment, the tip end portion of the cutting portion 7, where the cutting edge 11 and the flank 9 are formed, is configured to be detachable from the rear end portion. In this case, the tip end portion is referred to as the insert 1a, and the rear end portion of the cutting portion 7 combined with the gripping portion 5 is referred to as the holder 1b. The drill 1 of this embodiment may have a main body 3 to which the insert 1a is fixed to the holder 1b. In this case, the insert 1a can be treated as part of the main body 3. Of course, in the drill 1 of this example disclosure, there is no problem even if the cutting portion 7 has a configuration formed from a single member (a so-called solid-type structure) instead of the above-described configuration, and in the following description, a cutting portion 7 having a solid-type structure will sometimes be referred to as a "solid-type cutting portion 7."

[0014] The insert 1a of the drill 1 according to this embodiment will be described in detail below. However, the drill 1 according to one configuration example of the present disclosure may have a solid-type cutting portion 7 instead of the insert 1a as described above. The configuration (technical concept) of the insert 1a described below can also be applied to the solid-type cutting portion 7. In Figure 2 and other figures, the reference symbol of the cutting portion 7 is written alongside the insert 1a.

[0015] In the drill 1 of this embodiment, the multiple cutting edges 11 of the insert 1a may each be in a rotationally symmetric positional relationship about the rotation axis O1, and the multiple discharge flutes 13 may each be in a rotationally symmetric positional relationship about the rotation axis O1, similar to the multiple cutting edges 11. Furthermore, the multiple flank faces 9 may each be in a rotationally symmetric positional relationship about the rotation axis O1.

[0016] In the non-limiting example of the drill 1 shown in Figures 2 and 3, the three cutting edges 11 are positioned to have 120° rotational symmetry. Similarly, in the non-limiting example shown in Figures 2 and 3, the three discharge flutes 13 and the three flanks 9 are also positioned to have 120° rotational symmetry, just like the multiple cutting edges 11.

[0017] Because the three cutting edges 11 have a rotationally symmetrical configuration, the following will focus on one of the three cutting edges 11, and will omit detailed description of the other two cutting edges 11. Similarly, because the three discharge grooves 13 and the three flank faces 9 each have a rotationally symmetrical configuration, the following will focus on one of the three discharge grooves 13 and one of the three flank faces 9, and will omit detailed description of the other two discharge grooves 13 and two flank faces 9.

[0018] <Cutting edge> As shown in Figures 2 and 3 , the cutting edge 11 may have a chisel edge 21 that intersects with the rotation axis O1, a thinning edge (first edge) 23 that extends from the chisel edge 21 toward the outer periphery of the main body 3, and a main cutting edge (second edge) 25 that extends from the thinning edge 23 toward the outer periphery of the main body 3.

[0019] The chisel edge 21 extends from the rotation axis O1 toward the outer periphery. Normally, a cutting edge is located at the intersection of a flank and a rake face. However, when there are multiple cutting edges, it can be difficult to provide a rake face near the rotation axis in order to ensure the core thickness of the main body. Therefore, near the rotation axis, a cutting edge is formed by the intersection of multiple flanks corresponding to the multiple cutting edges. This portion is called a chisel edge.

[0020] The thinning edge 23 is located at the intersection of the flank 9 and the thinning surface 15, which is the rake face. In other words, in the drill 1 of this embodiment, the thinning edge 23 is located at the intersection of the thinning surface 15 and the flank 9. The main cutting edge 25 is located at the intersection of the flank 9 and the rake face, which forms part of the discharge flute 13. In other words, in the drill 1 of this embodiment, the main cutting edge 25 is located at the intersection of the rake face and the flank 9.

[0021] The thinning surface 15 is located closer to the rotation axis O1 (inside the chain line shown in FIG. 3 ) in the radial direction than the region where the discharge flutes 13 are located when the drill 1 is viewed in a plane along the rotation axis O1. In other words, the thinning surface 15 is located so as to overlap with the core thickness of the body 3 when the drill 1 is viewed in a plane along the rotation axis O1. In this way, the thinning surface 15 and the rake face may be distinguished depending on whether they are located in the region where the discharge flutes 13 are located in the radial direction (outside the chain line C1 shown in FIG. 3 ) when the drill 1 is viewed in a plane along the rotation axis O1, or inside this region.

[0022] 4 is an enlarged view of region B shown in FIG. 3. As shown in FIGS. 3 and 4, in a plan view from the direction along the rotation axis O1, a boundary portion 24 where the boundary between the thinning edge 23 and the major cutting edge 25 is located may have a convex shape facing forward in the rotation direction Y1. Also, in the above-mentioned plan view, the thinning edge 23 may have a protrusion 26 that is convex facing forward in the rotation direction Y1. Furthermore, the major cutting edge 25 may have a first portion 25-1 and a second portion 25-2 located closer to the outer periphery of the main body 3 than the first portion 25-1, and may have a concave shape that is recessed backward in the rotation direction Y1.

[0023] The planar view from the direction along the rotation axis O1 can also be expressed as a front view of the cutting edge 11 from the tip 3a side in the direction along the rotation axis O1, or simply as a front view of the tip.

[0024] As shown in Figure 4, the cutting edge 11 has been honed, and has a honed surface. Honing is a process in which a sharp cutting edge formed by the intersection of two surfaces is chamfered to form an obtuse angle or a slightly curved surface, thereby increasing the rigidity of the cutting edge and preventing breakage. Honing may be chamfer honing or R honing. Hereinafter, the width of the honed surface will also be referred to as the honing width. The smaller the honing width, the sharper the cutting edge, while the larger the honing width, the stronger the cutting edge and the better the durability of the cutting edge 11.

[0025] By subjecting the cutting edge 11 to honing processing, the thinning edge 23 has a first honing surface H1, the main cutting edge 25 has a second honing surface H2, and the chisel edge 21 has a third honing surface H3.

[0026] <Cutting Edge and Honing Width> With reference to Figures 5 to 16 in addition to Figure 4, the honing width of each portion of the cutting edge 11 of the drill 1 in this embodiment will be described. Figure 5 is a cross-sectional view taken along line V-V in Figure 4. Figure 6 is a cross-sectional view taken along line VI-VI in Figure 4. Figure 7 is a cross-sectional view taken along line VII-VII in Figure 4. Figure 8 is a cross-sectional view taken along line VIII-VIII in Figure 4. Figure 9 is a cross-sectional view taken along line IX-IX in Figure 4. Figure 10 is a cross-sectional view taken along line X-X in Figure 4. Figure 11 is a cross-sectional view taken along line XI-XI in Figure 4. Figure 12 is a cross-sectional view taken along line XII-XII in Figure 4. Figure 13 is a cross-sectional view taken along line XIII-XIII in Figure 4. Figure 14 is a cross-sectional view taken along line XIV-XIV in Figure 4.

[0027] Honing width W1 shown in Fig. 5 is the width of the third honing surface H3 of chisel edge 21. Honing width W2 shown in Fig. 6 is the width of the honing surface at the boundary between the third honing surface H3 and the first honing surface H1 of thinning edge 23. In other words, it is the width of the third honing surface H3 and also the width of the first honing surface H1.

[0028] 7 to 10 are the widths of the first honing surface H1 of the thinning edge 23. Honing width W7 shown in Fig. 11 is the width of the honing surface at the boundary between the first honing surface H1 and the second honing surface H2 of the main cutting edge 25. In other words, it is the width of the first honing surface H1 and also the width of the second honing surface H2.

[0029] Honing widths W8 to W10 shown in FIGS. 12 to 14 are the widths of the second honing surface H2 of the main cutting edge 25.

[0030] Fig. 15 is a graph in which the honing width measured at multiple points when viewed from the front of the tip of the cutting edge 11 of the drill 1 shown in Fig. 1 is plotted. In Fig. 15, the vertical axis represents the honing width, and the horizontal axis represents the measurement points. Fig. 16 is a diagram showing the measurement points on the horizontal axis of the graph shown in Fig. 15.

[0031] The chisel edge 21 is the part that is pressed against the workpiece 103 (see FIG. 17 ) during cutting, and is the part that rotates at a slow speed because it is closest to the rotation axis O1. Therefore, the chisel edge 21 is more likely to receive a larger cutting load than the thinning edge 23 and the main cutting edge 25 of the cutting edge 11.

[0032] Therefore, as shown at measurement points 1 and 2 in Figure 15, when viewed in a plane from a direction along the rotation axis O1, the width of the third honing surface H3 of the chisel edge 21 may be configured to become smaller as it approaches the outer periphery of the main body 3.

[0033] With this configuration, the durability of the cutting edge of the chisel edge 21 is increased near the center of the chisel edge 21, close to the rotation axis O1 where a large cutting load is applied, while the sharpness increases toward the outer periphery, preventing an unnecessary increase in cutting load. This ensures the durability of the chisel edge 21 while also ensuring ease of biting into the workpiece 103.

[0034] Furthermore, the boundary portion 24 between the thinning edge 23 and the main cutting edge 25 described above has a convex shape in the rotational direction Y1, and the boundary portion 24 is the portion that bites into the workpiece 103 (see FIG. 17 ). Here, because the boundary portion 24 has a convex shape, the chips generated by the thinning edge 23 and the main cutting edge 25 at the boundary portion 24 travel in different directions and tend to flow in directions that collide with each other. When the chip flows collide, the flow tends to stagnate, and chip clogging is likely to occur.

[0035] 15, the width of the first honing surface H1 at the boundary portion 24 between the thinning edge 23 and the main cutting edge 25 (hereinafter referred to as Wb1 for convenience) may be smaller than the maximum value of the width of the first honing surface H1 (hereinafter referred to as Wmax1 for convenience). In other words, the thinning edge 23 may have a portion (measurement point 5) that has a maximum value for ensuring cutting edge strength other than the boundary portion 24 (measurement point 7).

[0036] This configuration improves the sharpness of the boundary portion 24 of the thinning blade 23. This increases the flow speed of chips generated at the boundary portion 24 of the thinning blade 23, and even if the chips generated at the boundary portion 24 flow in directions that cause them to collide with each other, the flow is smoothed, making it less likely for chip clogging to occur.

[0037] Furthermore, because the chips generated at the boundary portion 24 travel in different directions from the thinning edge 23 and the main cutting edge 25, a relatively large cutting load is likely to be applied to the boundary portion 24. However, when the width of the first honing surface H1 at the boundary portion 24 is configured as described above, the thinning edge 23 is less likely to chip at a location located near the boundary portion 24. Therefore, abnormalities in the flow of chips due to chipping of the thinning edge 23 are less likely to occur, and chip clogging is less likely to occur.

[0038] Reducing the width of the first honing surface H1 overall can also smooth the flow of chips at the boundary portion 24 of the thinning edge 23. However, if the width of the first honing surface H1 is reduced overall, the rake angle of the thinning edge 23 is very small, which may reduce the durability of the thinning edge 23, which is prone to receiving a large cutting load. In contrast, by providing a portion with the maximum value in a location other than the boundary portion 24 as described above, it is possible to ensure an area with high cutting edge strength and ensure the durability of the thinning edge 23, while smoothing the flow of chips generated at the boundary portion 24 and making chip clogging less likely to occur.

[0039] When the width Wb1 is smaller than the maximum value Wmax1, the ratio of the width Wb1 to the maximum value Wmax1 is not limited to a specific value, but may be set to, for example, about 0.5 to 0.9 (50 to 90%).

[0040] The main cutting edge 25 at the boundary portion 24 may also be configured in the same manner as the thinning edge 23. That is, as shown in measurement points 7 and 8 in Figure 15 , in a plan view from the direction along the rotation axis O1, the width of the second honing surface H2 at the boundary portion 24 between the thinning edge 23 and the main cutting edge 25 (hereinafter, for convenience, referred to as Wb2) may be configured to be smaller than the maximum value of the width of the second honing surface H2 (hereinafter, for convenience, referred to as Wmax2). That is, the main cutting edge 25 may also have a portion (measurement point 8) having a maximum value for ensuring cutting edge strength, in addition to the boundary portion 24 (measurement point 7). In Figure 15 , Wb1 and Wb2 are the same value.

[0041] This configuration improves the sharpness of the boundary portion 24 of the main cutting edge 25. This increases the flow speed of chips generated at the boundary portion 24 of the main cutting edge 25, and even if the chips generated at the boundary portion 24 flow in directions that cause them to collide with each other, the flow is smoothed, making it less likely for chip clogging to occur.

[0042] Furthermore, as described above, the thinning edge 23 and the main cutting edge 25 at the boundary portion 24 generate chips in different directions, so a relatively large cutting load is likely to be applied to the boundary portion 24. However, when the width of the second honing surface H2 at the boundary portion 24 is configured as described above, the main cutting edge 25 is less likely to chip at a location located near the boundary portion 24. Therefore, abnormalities in the flow of chips caused by chipping of the main cutting edge 25 are less likely to occur, and chip clogging is less likely to occur.

[0043] When the width Wb2 is smaller than the maximum value Wmax2, the ratio of the width Wb2 to the maximum value Wmax2 is not limited to a specific value, but may be set to, for example, approximately 0.5 to 0.9 (50 to 90%).

[0044] Furthermore, the honing widths Wb1 and Wb2 of the boundary portion 24 may be smaller than the maximum honing width values ​​Wmax1 and Wmax2 of the thinning edge 23 and the main cutting edge 25. This increases the flow speed of chips generated at the boundary portion 24 in both the thinning edge 23 and the main cutting edge 25, making the flow of chips generated at the boundary portion 24 even smoother and less likely to cause chip clogging.

[0045] Furthermore, boundary portion 24 is the portion that bites into the workpiece, so chipping is likely to occur. Therefore, if the width of first honing surface H1 is made too small in order to smooth the flow of chips generated at boundary portion 24, chipping is likely to occur.

[0046] 15 , the width Wb1 of the first honing surface H1 at the boundary portion 24 between the thinning edge 23 and the main cutting edge 25 may be configured to be greater than the minimum width of the first honing surface H1 (hereinafter referred to as Wmin1 for convenience) in plan view from the direction along the rotation axis O1. In other words, the thinning edge 23 may have a portion (measurement point 4) having the minimum width other than the boundary portion 24 (measurement point 7).

[0047] This configuration ensures durability while improving the sharpness of the boundary portion 24 of the thinning edge 23. As a result, even if chips generated at the boundary portion 24 flow in directions that cause them to collide with each other, the flow can be made smooth, making it difficult for chips to clog, and also making it possible to prevent chipping at the boundary portion 24.

[0048] When the width Wb1 is greater than the minimum value Wmin1, the ratio of the width Wb1 to the minimum value Wmin1 is not limited to a specific value, but may be set to, for example, about 1.2 to 5 (120 to 500%).

[0049] Furthermore, when comparing the loads applied to each portion of the cutting edge 11 , the load applied to the chisel edge 21 is greater than the loads applied to the thinning edge 23 and the main cutting edge 25 .

[0050] 15 , the maximum width of the third honing surface H3 (hereinafter referred to as Wmax3 for convenience) may be greater than the maximum width Wmax1 of the first honing surface H1 and the maximum width Wmax2 of the second honing surface H2 in a plan view from the direction along the rotation axis O1. In other words, the maximum honing width of the chisel edge 21 included in the cutting edge 11 (measurement point 1) may be greater than the maximum honing width of the thinning edge 23 (measurement point 5) and the maximum honing width of the main cutting edge 25 (measurement point 8).

[0051] With this configuration, the cutting edge strength of the chisel edge 21 is higher than that of the thinning edge 23 and the main cutting edge 25. This ensures that the cutting edge strength is appropriate for the load applied to each part of the cutting edge 11, thereby improving the durability of the cutting edge 11.

[0052] The ratio of the maximum values ​​Wmax1 and Wmax2 to the maximum value Wmax3 is not limited to a specific value, but may be set to, for example, about 0.4 to 0.95 (40 to 95%).

[0053] 15 , the minimum width of the third honing surface H3 (hereinafter referred to as Wmin3 for convenience) may be greater than the minimum width Wmin1 of the first honing surface H1 and the minimum width Wmin2 of the second honing surface H2 in a plan view along the rotation axis O1. In other words, the minimum honing width of the chisel edge 21 included in the cutting edge 11 (measurement point 2) may be greater than the minimum honing width of the thinning edge 23 (measurement point 4) and the minimum honing width of the main cutting edge 25 (measurement point 10).

[0054] With this configuration, the cutting edge strength of the chisel edge 21 is higher than that of the thinning edge 23 and the main cutting edge 25. This ensures that the cutting edge strength is appropriate for the load applied to each part of the cutting edge 11, thereby improving the durability of the cutting edge 11.

[0055] The ratio of the minimum values ​​Wmin1 and Wmin2 to the minimum value Wmin3 is not limited to a specific value, but may be set to, for example, about 0.4 to 0.95 (40 to 95%).

[0056] Furthermore, when the thinning edge 23 and the main cutting edge 25 are compared, the rake angle of the thinning edge 23 is smaller than that of the main cutting edge 25. Here, the thinning edge 23 has a slower rotation speed than the main cutting edge 25, so it is less sharp and is subjected to a larger cutting load.

[0057] 15, the maximum width Wmax1 of the first honing surface H1 may be greater than the maximum width Wmax2 of the second honing surface H2 in plan view from the direction along the rotation axis O1. In other words, the maximum honing width of the thinning edge 23 (measurement point 5) may be greater than the maximum honing width of the main cutting edge 25 (measurement point 8).

[0058] With this configuration, the cutting edge strength of the thinning edge 23 is higher than that of the main cutting edge 25. This ensures that the cutting edge strength of the cutting edge 11 is appropriate for the loads applied to the thinning edge 23 and the main cutting edge 25, respectively, and improves the durability of the cutting edge 11.

[0059] When the maximum value Wmax1 is greater than the maximum value Wmax2, the ratio of the maximum value Wmax2 to the maximum value Wmax1 is not limited to a specific value, but may be set to, for example, approximately 0.5 to 0.95 (50 to 95%).

[0060] The thinning blade 23 has protrusions 26 formed as bent portions to form a plurality of thinning surfaces 15. The advantage of forming a plurality of thinning surfaces 15 is that it is easy to ensure a flow path for chips, and the strength of the central portion of the main body 3 can be ensured without digging too deeply.

[0061] The protrusions 26 have a convex shape in the rotation direction Y1, so that, like the boundary portions 24, the chips generated at the portions where the protrusions 26 are located flow in different directions and tend to collide with each other. When the chip flows collide, the flow tends to stagnate, and chip clogging is likely to occur.

[0062] Furthermore, the protrusion 26 is located closer to the rotation axis O1 than the boundary portion 24 and is located inside, and the discharge space provided by the thinning surface 15 is narrow, so the chip discharge performance is inferior to that of the boundary portion 24.

[0063] 15 , the width of the first honing surface H1 may be configured to be minimum at the protrusion 26 of the thinning edge 23 in plan view from the direction along the rotation axis O1. In other words, the honing width of the thinning edge 23 may be smallest at the portion of the protrusion 26 (measurement point 4).

[0064] This configuration improves the sharpness of the protrusion 26 portion of the thinning edge 23. This increases the flow speed of chips generated at the protrusion 26 portion of the thinning edge 23, and even if chips generated at the protrusion 26 portion flow in directions that collide with each other, the flow is smoothed, making chip clogging less likely to occur. In addition, because the sharpness can be improved compared to the boundary portion 24, the chip ejection ability of the cutting edge 11 as a whole can be improved.

[0065] As with the boundary portion 24, the directions of travel of chips generated at the portion where the protrusion 26 is located are different from each other, so a relatively large cutting load is likely to be applied to the protrusion 26. However, when the width of the first honing surface H1 at the protrusion 26 is configured as described above, the protrusion 26 is less likely to chip. Therefore, abnormalities in the flow of chips caused by chipping of the thinning edge 23 at the protrusion 26 are less likely to occur, and chip clogging is less likely to occur.

[0066] 4, the main cutting edge 25 may have a first portion 25-1 and a second portion 25-2 located closer to the outer periphery of the main body 3 than the first portion 25-1, and may have a concave shape recessed rearward in the rotation direction Y1. However, cutting loads tend to concentrate on a bottom 27 of the concave shape.

[0067] Therefore, as shown at measurement points 7 and 8 in Figure 15, the width of the second honing surface H2 in the first portion 25-1 may be configured to increase toward the outer periphery of the main body 3, and the width of the second honing surface H2 in the second portion 25-2 may be configured to decrease toward the outer periphery of the main body 3.

[0068] In other words, the main cutting edge 25 may have a portion located relatively inside where the width of the second honing surface H2 increases toward the outer periphery of the main body 3, and a portion located relatively outside where the width of the second honing surface H2 decreases toward the outer periphery of the main body 3. For convenience, the former portion may be designated as the first portion 25-1, and the latter portion may be designated as the second portion 25-2.

[0069] With this configuration, the width of the second honing surface H2 in the first portion 25-1 increases toward the bottom 27 of the concave shape, and the durability of the cutting edge of the main cutting edge 25 can be improved compared to a configuration in which the honing width of the main cutting edge 25 monotonically decreases.

[0070] When the drill 1 has multiple cutting edges 11, if the honing surface of at least one of the multiple cutting edges 11 has the above-mentioned configuration, it is possible to reduce the cutting load and improve chip discharge performance. Furthermore, if the honing surfaces of all of the multiple cutting edges 11 have the above-mentioned configuration, it is possible to further reduce the cutting load and further improve chip discharge performance.

[0071] In the drill 1 of this embodiment, the outer diameter of the cutting portion 7 is set to, for example, 6 mm to 42.5 mm. In addition, in the drill 1 of this embodiment, when the length of the axis (the length of the cutting portion 7) is L and the diameter (the outer diameter of the cutting portion 7) is D, for example, L is set to 1D to 12D.

[0072] Examples of the material of the main body 3 include cemented carbide and cermet. Examples of the composition of the cemented carbide include WC-Co, WC-TiC-Co, and WC-TiC-TaC-Co. Here, WC, TiC, and TaC may be hard particles, and Co may be a binder phase.

[0073] The cermet may be a sintered composite material in which a ceramic component is combined with a metal. An example of a cermet is a titanium compound mainly composed of titanium carbide (TiC) or titanium nitride (TiN). It goes without saying that the material of the main body 3 is not limited to the above composition.

[0074] The surface of the main body 3 may be coated with a film by chemical vapor deposition (CVD) or physical vapor deposition (PVD). The composition of the film may be, for example, titanium carbide (TiC), titanium nitride (TiN), titanium carbonitride (TiCN), and alumina (Al ２ O ３ ) and the like can be mentioned.

[0075] <Method for Manufacturing Machined Product> Next, a non-limiting method for manufacturing a machined product 101 of one surface according to the present disclosure will be described with reference to FIG. 17 . FIG. 17 is a schematic diagram illustrating one step of a method for manufacturing a machined product according to an embodiment of the present disclosure. The machined product 101 may be produced by cutting a workpiece 103. The method for manufacturing the machined product 101 may include the following steps (1) to (4).

[0076] (1) A step of placing the drill 1 above the prepared workpiece 103 (see reference numeral 1000 in FIG. 17).

[0077] (2) A process of rotating the drill 1 in the direction of the arrow Y1 around the rotation axis O1 and moving the drill 1 toward the workpiece 103 in the direction Y2 (see reference numeral 1000 in FIG. 17).

[0078] In the above-described steps (1) and (2), for example, the workpiece 103 may be fixed on a table of a machine tool to which the drill 1 is attached, and the drill 1 may be rotated and brought closer to the workpiece 103. In step (2), the workpiece 103 and the drill 1 may be brought relatively close to each other, and for example, the workpiece 103 may be brought closer to the drill 1.

[0079] (3) A process of bringing the drill 1 even closer to the workpiece 103, thereby contacting the rotating drill 1 with the desired position on the surface of the workpiece 103, and forming a machining hole 105 in the workpiece 103 (see symbol 1001 in Figure 17).

[0080] In the above-described step (3), cutting may be performed so that at least a portion of the cutting portion 7 of the main body 3 is located within the machined hole 105. At this time, the cutting edge 11 of the main body 3 may come into contact with the workpiece 103 to form the machined hole 105. Also, in step (3), the gripping portion 5 of the main body 3 may be set to be located outside the machined hole 105. From the viewpoint of obtaining a good finished surface, a portion of the cutting portion 7 on the rear end 3b side may be set to be located outside the machined hole 105. This portion can function as a margin region for chip evacuation, and excellent chip evacuation can be achieved via this region.

[0081] (4) Step of moving the drill 1 away from the workpiece 103 in the Y3 direction (see reference numeral 1002 in FIG. 17).

[0082] In the above-mentioned step (4), similarly to the above-mentioned step (2), the workpiece 103 and the drill 1 may be relatively separated from each other. For example, the workpiece 103 may be separated from the drill 1.

[0083] By going through the above steps, it is possible to obtain a machined product 101 having a highly accurate machined hole 105 .

[0084] When cutting the workpiece 103 multiple times, for example, when forming multiple machining holes 105 in one workpiece 103, the process of contacting the cutting edge 11 of the drill 1 with different locations on the workpiece 103 while keeping the drill 1 rotating may be repeated.

[0085] Examples of materials for the workpiece 103 include aluminum, carbon steel, alloy steel, stainless steel, cast iron, and non-ferrous metals.

[0086] <Summary> A drill according to a first aspect of the present disclosure has a body extending from a tip to a rear end and configured to rotate around an axis serving as a rotation axis, the body having a cutting edge located near the tip and an ejection groove extending from the cutting edge toward the rear end, the cutting edge having a chisel edge intersecting the rotation axis, a first blade extending from the chisel edge toward the outer periphery of the body, and a second blade extending from the first blade toward the outer periphery of the body, wherein, in a planar view along the rotation axis, a boundary portion where the first blade and the second blade are located has a convex shape facing forward in the direction of rotation around the rotation axis, the first blade has a first honing surface, the second blade has a second honing surface, and the chisel edge has a third honing surface, wherein, in a planar view along the rotation axis, the width of the third honing surface decreases toward the outer periphery of the body, and the width of the first honing surface at the boundary portion is smaller than the maximum value of the width of the first honing surface.

[0087] In a drill according to a second aspect of the present disclosure, in the first aspect, the width of the first honing surface at the boundary portion in a plan view is greater than the minimum value of the width of the first honing surface.

[0088] In a drill according to a third aspect of the present disclosure, in the first or second aspect, the width of the second honing surface at the boundary portion in the plan view is smaller than the maximum value of the width of the second honing surface.

[0089] In the drill of aspect 4 of the present disclosure, in any one of aspects 1 to 3, when viewed in the plan view, the maximum value of the width of the third honing surface is greater than the maximum value of the width of the first honing surface and the maximum value of the width of the second honing surface.

[0090] A drill according to aspect 5 of the present disclosure is any one of aspects 1 to 4, wherein, in the plan view, the maximum value of the width of the first honing surface is greater than the maximum value of the width of the second honing surface.

[0091] The drill in aspect 6 of the present disclosure is any one of aspects 1 to 5, wherein, in the planar view, the minimum value of the width of the third honing surface is greater than the minimum value of the width of the first honing surface and the minimum value of the width of the second honing surface.

[0092] In the drill of aspect 7 of the present disclosure, in any one of aspects 1 to 6, when viewed in the plan view, the first cutting edge has a protrusion that is convex toward the front in the rotation direction, and the width of the first honing surface is at its smallest value at the protrusion.

[0093] The drill in aspect 8 of the present disclosure is any one of aspects 1 to 7, wherein, in the plan view, the second cutting edge has a first portion and a second portion located closer to the outer periphery of the body than the first portion, and has a concave shape recessed rearward in the direction of rotation, and the width of the second honing surface at the first portion increases toward the outer periphery of the body, and the width of the second honing surface at the second portion decreases toward the outer periphery of the body.

[0094] A method for manufacturing a machined product in aspect 9 of the present disclosure includes a step of rotating a drill of any one of aspects 1 to 8 around the rotation axis, a step of bringing the cutting edge of the rotating drill into contact with a workpiece, and a step of moving the drill away from the workpiece.

[0095] [Additional Notes] The invention according to the present disclosure has been described above based on the drawings and embodiments. However, the invention according to the present disclosure is not limited to the above-described embodiments. In other words, the invention according to the present disclosure can be modified in various ways within the scope of the present disclosure, and embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the invention according to the present disclosure. In other words, it should be noted that a person skilled in the art could easily make various modifications or corrections based on the present disclosure. It should also be noted that these modifications or corrections are included in the scope of the present disclosure.

[0096] DESCRIPTION OF SYMBOLS 1 Drill 1a Insert 1b Holder 3 Body 3a Tip 3b Rear end 11 Cutting edge 13 Discharge groove 15 Thinning surface 21 Chisel edge 23 Thinning edge (first edge) 25 Main cutting edge (second edge) 25-1 First portion 25-2 Second portion 24 Boundary portion 26 Protrusion 101 Cutting workpiece 103 Workpiece H1 First honing surface H2 Second honing surface H3 Third honing surface Y1 Rotation direction

Claims

1. A drill having a body extending from a tip to a rear end and adapted to rotate around an axis serving as a rotation axis, the body having: a cutting edge located on the tip side; and an ejection groove extending from the cutting edge towards the rear end, the cutting edge having: a chisel edge intersecting the rotation axis; a first blade extending from the chisel edge towards the outer periphery of the body; and a second blade extending from the first blade towards the outer periphery of the body, wherein, in a planar view taken along the rotation axis, a boundary portion where the first blade and the second blade are located has a convex shape facing forward in the direction of rotation around the rotation axis, the first blade has a first honing surface, the second blade has a second honing surface, and the chisel edge has a third honing surface, wherein, in a planar view taken along the rotation axis, the width of the third honing surface decreases towards the outer periphery of the body, and the width of the first honing surface at the boundary portion is smaller than the maximum value of the width of the first honing surface.

2. The drill according to claim 1, wherein, in the plan view, the width of the first honing surface at the boundary portion is greater than the minimum width of the first honing surface.

3. The drill according to claim 1 or 2, wherein, in the plan view, the width of the second honing surface at the boundary portion is smaller than the maximum width of the second honing surface.

4. A drill according to any one of claims 1 to 3, wherein, in the plan view, the maximum value of the width of the third honing surface is greater than the maximum value of the width of the first honing surface and the maximum value of the width of the second honing surface.

5. A drill according to any one of claims 1 to 4, wherein, in the plan view, the maximum width of the first honing surface is greater than the maximum width of the second honing surface.

6. A drill according to any one of claims 1 to 5, wherein, in the plan view, the minimum width of the third honing surface is greater than the minimum width of the first honing surface and the minimum width of the second honing surface.

7. A drill as claimed in any one of claims 1 to 6, wherein, in the plan view, the first cutting edge has a protrusion that is convex toward the front in the rotation direction, and the width of the first honing surface is at its smallest value at the protrusion.

8. A drill as claimed in any one of claims 1 to 7, wherein, in the plan view, the second cutting edge has a first portion and a second portion located closer to the outer periphery of the body than the first portion, and has a concave shape recessed rearward in the direction of rotation, the width of the second honing surface at the first portion increasing toward the outer periphery of the body, and the width of the second honing surface at the second portion decreasing toward the outer periphery of the body.

9. A method for manufacturing a machined product, comprising the steps of: rotating the drill according to any one of claims 1 to 8 around the rotation axis; bringing the cutting edge of the rotating drill into contact with a workpiece; and separating the drill from the workpiece.

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