Drill and method for manufacturing cut article

Abstract

This drill has a body extending from the tip end to the base end along an axis of rotation. The body includes: a rake face; a cutting edge; and a discharge groove. An inner cutting edge located along a first rake face includes: a chisel edge; and a first cutting edge extending from the chisel edge toward the outer circumference. A central cutting edge located along a second rake face has a concave curved shape. An outer cutting edge located along a third rake face includes a second cutting edge having a concave curved shape extending toward the outer circumference.

Description

Method for manufacturing drills and cuttings

[0001] The present disclosure relates to a drill used in cutting work 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 members. Generally, the cutting edge of a drill has a chisel edge located at the innermost position and extending from the central axis. The chisel edge affects the straightness stability of the drill. The drill described in Patent Document 1 has one flank face (second flank face) as a flank face for one cutting edge. The drill described in Patent Document 2 has two flank faces (a first tip flank face located on the inner periphery and a second tip flank face located on the outer periphery) as flank faces for one cutting edge.

[0003] Japanese Patent Publication No. 2022-142055 Japanese Patent Publication No. 2020-175465

[0004]

[0006] A non-limiting example of a drill according to the present disclosure includes a rod-shaped body rotatable around a rotation axis and extending from a front end to a rear end along the rotation axis. The body includes a flank located at the front end, a cutting edge located at a front edge of the flank in the rotation direction, and an exhaust flute extending from the cutting edge. The flank includes a flat first flank extending from the rotation axis toward the outer periphery and approaching the rear end as it approaches the outer periphery, a concavely curved second flank extending from the first flank toward the outer periphery, and a flat third flank extending from the second flank toward the outer periphery and approaching the rear end as it approaches the outer periphery. The cutting edges include an inner cutting edge located along the first flank, a central cutting edge located along the second flank, and an outer cutting edge located along the third flank. The inner cutting edge includes a chisel edge extending from the rotation axis toward the outer periphery and a first cutting edge extending from the chisel edge toward the outer periphery. The central cutting edge has a concave curved shape, and the outer cutting edge has a second cutting edge that extends toward the outer periphery and has a concave curved shape.

[0005] 1 is a perspective view showing a drill according to an embodiment of the present disclosure. FIG. 2 is a perspective view showing an insert in the drill shown in FIG. 1. FIG. 3 is a front view of the insert shown in FIG. 2, viewed from the tip side. FIG. 4 is an enlarged view of region IV shown in FIG. 3. FIG. 4 is a side view of the insert shown in FIG. 3, viewed from the A1 direction. FIG. 4 is a side view of the insert shown in FIG. 3, viewed from the A2 direction. FIG. 5 is a cross-sectional view taken along line VII-VII in FIG. 4. FIG. 6 is a cross-sectional view taken along line VIII-VIII in FIG. 4. FIG. 7 is a cross-sectional view taken along line IX-IX in FIG. 4. FIG. 8 is a cross-sectional view taken along line X-X in FIG. 4. FIG. 9 is a cross-sectional view taken along line XI-XI in FIG. 4. FIG. 10 is a cross-sectional view taken along line XII-XII in FIG. 4. FIG. 11 is an enlarged view of the same region shown in FIG. 4. FIG. 12 is a schematic diagram showing one step in a method for manufacturing a machined product according to an embodiment of the present disclosure. FIG. 13 is a schematic diagram showing one step in a method for manufacturing a machined product according to an embodiment of the present disclosure.

[0006] 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 present invention 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.

[0007] Conventionally, for example, the drill described in Patent Document 1 has only one flat flank as a flank for one cutting edge. Therefore, there is a risk that the chisel edge will not bite into the workpiece sufficiently after the main cutting edge has bitten into it. Furthermore, in the drill described in Patent Document 2, the first tip flank extends over a wide range from the central axis toward the outer periphery. Therefore, similar to the drill described in Patent Document 1, there is a risk that the chisel edge will not bite into the workpiece sufficiently after the main cutting edge has bitten into it.

[0008] An object of the present disclosure is to provide a drill that allows the cutting edge to bite into the workpiece well.

[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 in the drill shown in Figure 1. Figure 3 is a front view of the insert shown in Figure 2 as viewed from the tip side.

[0010] 1 to 3, a drill 1 according to an embodiment of the present disclosure has a rod-shaped main body 3 that is rotatable around a rotation axis O1. The main body 3 extends from a front end 3a to a rear end 3b along the rotation axis O1. The main body 3 in this embodiment includes 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 that is located on the front side of the gripping portion 5.

[0011] 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 the workpiece and plays a primary role in cutting the workpiece. The arrow Y1 in Figure 1 indicates the rotation direction of the drill 1 (body 3).

[0012] The cutting portion 7 (main body 3) has a flank 9 located at the tip 3a, a cutting edge 11 located at the front edge of the flank 9 in the rotational direction Y1, and an ejection groove 13 extending from the cutting edge 11. The number of flanks 9, cutting edges 11, and ejection grooves 13 is not limited to a specific number. In the non-limiting example shown in Figure 1, the cutting portion 7 has three flanks 9, three cutting edges 11, and three ejection grooves 13, and is configured as a so-called three-flute drill. There is no problem if the cutting portion 7 has two flanks 9, two cutting edges 11, and two ejection grooves 13, and is configured as a so-called two-flute drill.

[0013] In the drill 1 of this embodiment, the tip end portion of the cutting portion 7, which includes the flank 9 and the cutting edge 11, is detachable from the rear end portion. In this case, the tip end portion is called an insert 1a, and the rear end portion of the cutting portion 7 and the gripping portion 5 are collectively called a holder 1b.

[0014] The drill 1 in this embodiment may have a main body 3 in which the insert 1a is fixed to the holder 1b, and in this case, the insert 1a can be treated as part of the main body 3. Of course, in the drill 1 according to the example of the present disclosure, there is no problem even if the cutting portion 7 has a configuration consisting of a single member (a so-called solid-type structure) instead of the above-mentioned configuration, and in the following description, the cutting portion 7 having a solid-type structure may be referred to as a "solid-type cutting portion 7."

[0015] 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.

[0016] In the drill 1 of this embodiment, the multiple flanks 9 of the insert 1a may each be in a rotationally symmetric positional relationship about the rotation axis O1, and the multiple cutting edges 11 may also be in a rotationally symmetric positional relationship about the rotation axis O1. Furthermore, the multiple discharge flutes 13 may also be in a rotationally symmetric positional relationship about the rotation axis O1.

[0017] In the non-limiting example of the drill 1 shown in Fig. 2, three flanks 9 are positioned to have 120° rotational symmetry. Similarly, in the non-limiting example shown in Fig. 2, three cutting edges 11 are positioned to have 120° rotational symmetry, and three discharge flutes 13 are positioned to have 120° rotational symmetry.

[0018] Since the three flanks 9 have a rotationally symmetrical configuration, the following will focus on one of the three flanks 9, and will omit detailed description of the other two flanks 9. Similarly, since the three cutting edges 11 and the three discharge grooves 13 have a rotationally symmetrical configuration, the following will focus on one of the three cutting edges 11 and one of the three discharge grooves 13, and will omit detailed description of the other two cutting edges 11 and two discharge grooves 13.

[0019] <Flank Face> The flank face 9 of the drill 1 in this embodiment will be described with reference to Fig. 4 as well as Figs. 1 to 3. Fig. 4 is an enlarged view of region IV shown in Fig. 3.

[0020] 1 to 4, the drill 1 in this embodiment has, as the flank 9, a first flank 15, a second flank 17, and a third flank 19. In Fig. 4, these flanks are hatched to facilitate visual understanding of the regions of the first flank 15, the second flank 17, and the third flank 19.

[0021] The first flank surface 15 is a flat surface that extends from the rotation axis O1 toward the outer periphery and approaches the rear end 3 b as it approaches the outer periphery. The second flank surface 17 is a concavely curved surface that extends from the first flank surface 15 toward the outer periphery. The third flank surface 19 is a flat surface that extends from the second flank surface 17 toward the outer periphery and approaches the rear end 3 b as it approaches the outer periphery. In other words, the first flank surface 15 and the third flank surface 19 are flat surfaces, and the second flank surface 17 is a concavely curved surface that connects these surfaces.

[0022] The second flank 17 and the third flank 19 located away from the rotation axis O1 may be inclined so as to approach the rear end 3b toward the rear in the rotation direction Y1 (the opposite side to the rotation direction Y1). The angle of this inclination is the so-called clearance angle.

[0023] In a non-limiting example of an insert 1a shown in Fig. 2, the first flank 15 and the second flank 17 are smoothly connected, and no ridge line is formed at the boundary between these surfaces. Also, in a non-limiting example of an insert 1a shown in Fig. 2, the second flank 17 and the third flank 19 are smoothly connected, and no ridge line is formed at the boundary between these surfaces. Note that "no ridge line is formed at the boundary" as mentioned above means that the ridge line is not discernible with the naked eye, and does not include ridge lines resulting from microscopic irregularities on the order of surface roughness.

[0024] In Figure 2 and other figures, in order to facilitate visual understanding, the part corresponding to the boundary between the first flank 15 and the second flank 17 and the part corresponding to the boundary between the second flank 17 and the third flank 19 are clearly shown by solid lines.

[0025] <Cutting Edge> The cutting edge 11 of the drill 1 in this embodiment will be described with reference to Figures 5, 6, and 13, as well as Figures 1 to 4. Figure 5 is a side view of the insert shown in Figure 3, viewed from the A1 direction. Figure 6 is a side view of the insert shown in Figure 3, viewed from the A2 direction. Figure 13 is an enlarged view of the same area as shown in Figure 4.

[0026] 1 to 6 and 13, in the drill 1 of this embodiment, the cutting edge 11 has an inner cutting edge 21 located along the first flank 15, a central cutting edge 23 located along the second flank 17, and an outer cutting edge 25 located along the third flank 19. Because the cutting edge 11 is located at the front edge of the flank 9 in the rotational direction Y1, the first flank 15 may be considered to extend from the inner cutting edge 21 toward the rear in the rotational direction Y1.

[0027] Similarly, it may be considered that the second flank 17 extends rearward in the rotational direction Y1 from the central cutting edge 23, and the third flank 19 extends rearward in the rotational direction Y1 from the outer cutting edge 25. Note that the central cutting edge 23 is a term that indicates a relative positional relationship with the inner cutting edge 21 and the outer cutting edge 25, and is not limited to a configuration in which the central cutting edge 23 is located in a radially intermediate portion of the drill 1, nor is it limited to a configuration in which an intermediate portion of the cutting edge 11 in the longitudinal direction is included in the central cutting edge 23.

[0028] (Inner Cutting Edge) Since the first flank 15 has a surface configuration that approaches the rear end 3b as it approaches the outer periphery, the inner cutting edge 21 also has a configuration that approaches the rear end 3b as it approaches the outer periphery.

[0029] The inner cutting edge 21 has a chisel edge 27 and a first cutting edge 29. The chisel edge 27 extends from the rotation axis O1 toward the outer periphery. The chisel edge 27 is the portion of the cutting edge 21 that is closest to the rotation axis O1.

[0030] Typically, the cutting edge is located at the intersection of the flank and the 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 body. Therefore, near the rotation axis, the cutting edge is formed by the intersection of multiple flanks corresponding to the multiple cutting edges. This part is called the chisel edge.

[0031] 4, the chisel edge 27 has a linear shape. Furthermore, since the chisel edge 27 extends from the rotation axis O1 toward the outer periphery, when the cutting edge 11 is viewed from the tip side, in other words, when viewed from the tip, the chisel edge 27 extends linearly in the radial direction from a point corresponding to the rotation axis O1, and the radial rake (radial rake angle) of the chisel edge 27 is zero.

[0032] The first cutting edge 29 extends from the chisel edge 27 toward the outer periphery. As described above, the chisel edge 27 is formed by the intersection of multiple flanks 9, while the first cutting edge 29 is formed by the intersection of the first flank 15 and the rake face. Since the inner cutting edge 21 has the first cutting edge 29, a wide rake face area can be easily secured. In addition, the chisel edge 27 can easily protrude toward the tip end. This makes it easy for the chisel edge 27 to stably bite into the workpiece.

[0033] The first cutting edge 29 may be formed, for example, by a single linear portion, or may be formed by a plurality of portions as in the non-limiting example shown in Fig. 4. In the example shown in Fig. 4, the first cutting edge 29 has a first portion 31 and a second portion 33. The first portion 31 is a portion located closer to the rotation axis O1 than the second portion 33, and the second portion 33 is a portion located more radially outward than the first portion 31. The first portion 31 and the second portion 33 may each be linear.

[0034] The radial rakes in the first region 31 and the second region 33 may each be negative. In this case, the radial rake φ2 in the second region 33 may have a negative value that is greater (in absolute value) than the radial rake φ1 in the first region 31.

[0035] When the radial rake φ1 in the first portion 31 and the radial rake φ2 in the second portion 33 are different values, the cutting load applied to the first portion 31 and the cutting load applied to the second portion 33 are partially offset, as is clear from the vector composition of the direction of the cutting load applied to the first portion 31 and the direction of the cutting load applied to the second portion 33.

[0036] Furthermore, when the radial rake φ2 in the second portion 33 is a negative value (in absolute value) that is smaller than the radial rake φ1 in the first portion 31, the durability of the cutting edge 11 at the boundary between the first portion 31 and the second portion 33 is enhanced.

[0037] In particular, when the first portion 31 and the second portion 33 are each linear, the cutting load is less likely to be concentrated at specific points in the first portion 31 and the second portion 33, thereby further increasing the durability of the cutting edge 11.

[0038] A negative radial rake value means that, when viewed from the tip, the target portion of the cutting edge 11 is inclined radially backward in the rotational direction Y1 as it approaches the outer periphery, whereas a positive radial rake value means that, when viewed from the tip, the target portion of the cutting edge 11 is inclined radially forward in the rotational direction Y1 as it approaches the outer periphery.

[0039] When viewed from the tip, the first portion 31 may be longer than the second portion 33. When the first cutting edge 29 has the first portion 31 and the second portion 33, the first cutting edge 29 is configured such that the boundary between the first portion 31 and the second portion 33 protrudes forward in the rotational direction Y1.

[0040] In such a case, there is a risk that cutting loads will be concentrated at the boundary between the first portion 31 and the second portion 33. Here, if the first portion 31 is longer than the second portion 33, the boundary is likely to be located on the outer periphery of the first cutting edge 29. The closer to the outer periphery, the faster the cutting speed becomes and the better the cutting performance, thereby improving the durability of the first cutting edge 29.

[0041] Since the second flank 17 has a concave curved shape, the central cutting edge 23 located along the second flank 17 in the front in the rotation direction Y1 has a concave curved shape. More specifically, the central cutting edge 23 has a concave curved shape that is slightly recessed toward the rear in the rotation direction Y1 when viewed from the tip.

[0042] The central cutting edge 23 has a concave curved shape recessed toward the rear end 3b when viewed from the front in the rotational direction Y1 (see FIGS. 2, 5, and 6). Here, the central cutting edge 23 may have a smaller radius of curvature when viewed from the front in the rotational direction Y1 than when viewed from the tip.

[0043] (Outer Cutting Edge) The outer cutting edge 25 located along the third flank 19 in the front in the rotational direction Y1 has a second cutting edge 35 having a concave curved shape extending toward the outer periphery. When viewed from the tip, the second cutting edge 35 has a concave curved shape recessed toward the rear in the rotational direction Y1. As shown in Figure 4, the outer cutting edge 25 may be longer than the inner cutting edge 21 and the central cutting edge 23.

[0044] In this case, the amount of workpiece material cut by the outer cutting edge 25 is greater than that by the inner cutting edge 21 and the central cutting edge 23. In other words, since the outer cutting edge 25 functions as the main cutting edge portion in the cutting process, the outer cutting edge 25 is also called the main cutting edge.

[0045] The second cutting edge 35 has a concave curved shape recessed toward the rear in the rotational direction Y1 when viewed from the tip. Also, the second cutting edge 35 has a concave curved shape recessed slightly toward the rear end 3b when viewed from the front in the rotational direction Y1 (see FIGS. 2, 5, and 6). Here, the second cutting edge 35 may have a smaller radius of curvature when viewed from the tip than when viewed from the front in the rotational direction Y1.

[0046] Because the third flank 19 has a surface configuration in which it approaches the rear end 3b as it approaches the outer periphery, the outer cutting edge 25 also has a configuration in which it approaches the rear end 3b as it approaches the outer periphery. Thus, the third flank 19 is inclined so as to approach the rear end 3b as it approaches the outer periphery, and the outer cutting edge 25 is also inclined so as to approach the rear end 3b as it approaches the outer periphery. Because the outer cutting edge 25 has such an inclined configuration, the direction of travel of the drill 1 is less likely to deviate even when the outer cutting edge 25 bites into the workpiece, and good linear stability of the drill 1 is easily ensured.

[0047] As described above, in the drill 1 of the present disclosure, the inner cutting edge 21 located along the first flank 15 has the first cutting edge 29 in addition to the chisel edge 27. Therefore, the chisel edge 27 easily protrudes toward the tip, and the chisel edge 27 bites into the workpiece well. Furthermore, because the third flank 19 is configured to be inclined so as to approach the rear end 3b as it approaches the outer periphery, the outer cutting edge 25 is also configured to be inclined so as to approach the rear end 3b as it approaches the outer periphery. Therefore, good linear stability of the drill 1 is ensured even when the outer cutting edge 25 bites into the workpiece.

[0048] In the drill 1 of the present disclosure, at least a portion of the inner cutting edge 21 may be located closer to the tip 3a than a virtual rotation locus that extends the outer cutting edge 25 toward the rotation axis O1. Specifically, when the outer cutting edge 25 is viewed from the front in the rotation direction Y1 (see, for example, FIGS. 5 and 6 ), a tangent to the outer cutting edge 25 at this end passes through the end of the outer cutting edge 25 on the side of the rotation axis O1.

[0049] This tangent line is the aforementioned imaginary line, and a rotation locus around the rotation axis O1 of this imaginary line is set. In this case, at least a portion of the inner cutting edge 21 may be located closer to the tip 3a than this rotation locus. When the cutting edge 11 is configured in this manner, the chisel edge 27 is likely to protrude toward the tip, and even when the outer cutting edge 25 has bitten into the workpiece, the chisel edge 27 is likely to bite into the workpiece in a stable manner.

[0050] The outer cutting edge 25 may further include a third cutting edge 37 in addition to the second cutting edge 35. For example, as shown in an example in Figure 4, the outer cutting edge 25 may further include a third cutting edge 37 having a linear shape extending from the central cutting edge 23 toward the second cutting edge 35.

[0051] The cutting load is difficult to distribute between the central cutting edge 23 and the second cutting edge 35, which have a concave curved shape. Therefore, when the central cutting edge 23 and the second cutting edge 35, which have a concave curved shape, are connected to each other, an excessively large cutting load may be applied near the boundary between the central cutting edge 23 and the second cutting edge 35. However, when the outer cutting edge 25 has the above-mentioned third cutting edge 37, the central cutting edge 23 can be separated from the second cutting edge 35. This improves the durability of the cutting edge 11.

[0052] Furthermore, when the central cutting edge 23 and the second cutting edge 35, which are concavely curved, are connected to each other, the angle at which the central cutting edge 23 and the second cutting edge 35 intersect tends to be small. That is, the boundary between the central cutting edge 23 and the second cutting edge 35 tends to be sharp, which may increase restrictions on cutting conditions (e.g., rotational speed, feed rate, etc.) in consideration of durability near the boundary between the central cutting edge 23 and the second cutting edge 35. However, when the outer cutting edge 25 has the third cutting edge 37, the cutting edge 11 is less likely to have a sharp portion as described above, and therefore the durability of the cutting edge 11 is improved from this viewpoint as well.

[0053] <Discharge flutes, rake face> The discharge flutes 13 of the drill 1 in this embodiment will be described with reference to Figures 7 to 12 as well as Figures 1 to 6 and 13. 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.

[0054] 1 to 13, in the drill 1 of this embodiment, the discharge flutes 13 of the cutting portion 7 (insert 1a) extend from the cutting edge 11 toward the rear end 3b. In the example drill 1 shown in Figure 1, the discharge flutes 13 extend from the second cutting edge 35 of the outer cutting edge 25 toward the rear end 3b.

[0055] The discharge groove 13 is a portion used to discharge chips generated by the cutting edge 11 to the outside. The discharge groove 13 does not need to extend to the rear end 3b of the main body 3. As in the example shown in Fig. 1, the discharge groove 13 may be formed only in the cutting portion 7 and not in the grip portion 5. As in the non-limiting example shown in Fig. 1, the discharge groove 13 may extend spirally around the rotation axis O1.

[0056] The insert 1a (cutting portion 7) may have a rake face 39 located along a portion of the cutting edge 11 excluding the chisel edge 27. In the example insert 1a shown in Fig. 2 etc., the discharge groove 13 extends from the second cutting edge 35 of the outer cutting edge 25 toward the rear end 3b. The portion of the discharge groove 13 along the second cutting edge 35 can function as the rake face 39 for the second cutting edge 35.

[0057] 5, the discharge groove 13 can function as a rake face 39 for the second cutting edge 35. As is clear from FIG. 2 and the like, the discharge groove 13 has a concave curved shape, and therefore the second cutting edge 35 located at the intersection of the flat third flank face 19 and the discharge groove 13 can be shown to have a concave curved shape.

[0058] In general, the grooves that form the end cutting edge are sometimes referred to as gashes, and as shown in an example in FIG. 2 , in the drill 1 of this embodiment, the cutting portion 7 (insert 1 a) may have a flat first gash surface 41 that extends from the first portion 31 toward the rear end 3 b. The first gash surface 41 can function as a rake face 39 for the first portion 31.

[0059] 7, in one example of the insert 1a, the axial rake θ1 of the first gash surface 41 may be positive. As described above, the chisel edge 27 adjacent to the first portion 31 is located on the ridge where the two flanks 9 intersect, and therefore chips are difficult to discharge at the chisel edge 27. Here, when the first gash surface 41 has the above configuration, chips generated at the chisel edge 27 are easily discharged through the first gash surface 41. Therefore, chip clogging is difficult to occur.

[0060] The axial rake θ1 of the first gash surface 41 being positive means that, in a cross section (cross section shown in FIG. 7 ) that is perpendicular to the first portion 31 and parallel to the rotation axis O1 when viewed from the tip, the first gash surface 41 is inclined rearward in the rotation direction Y1 as it moves away from the first portion 31. In this case, the axial rake may be replaced with the rake angle (rake angle in the axial direction).

[0061] 2 and the like, the cutting portion 7 (insert 1 a) of the drill 1 according to the present embodiment may have a flat second gash surface 43 extending from the second portion 33, the central cutting edge 23, and the third cutting edge 37. The second gash surface 43 may function as a rake face 39 for the second portion 33, the central cutting edge 23, and the third cutting edge 37.

[0062] The second cutting edge 35 has a concave curved shape, and the second portion 33, the central cutting edge 23, and the third cutting edge 37 are located closer to the rotation axis O1 than the second cutting edge 35. Therefore, the cutting speeds at the second portion 33, the central cutting edge 23, and the third cutting edge 37 are slower than the cutting speed at the second cutting edge 35. Therefore, the flow of chips generated at the second portion 33, the central cutting edge 23, and the third cutting edge 37 is more likely to stagnate than the flow of chips generated at the second cutting edge 35.

[0063] When the second gash surface 43 is flat, excessive curvature of the chips is avoided and the chip dischargeability is improved compared to, for example, when the second gash surface 43 is concave. In this way, the chip dischargeability is improved in areas where the chip flow is relatively likely to stagnate, making it less likely that chip clogging will occur.

[0064] 8 to 10, the axial rake θ2 of the second gash surface 43 may be positive. When the second gash surface 43 has such a configuration, chip clogging is even less likely to occur.

[0065] In addition, the axial rake θ2 of the second gash surface 43 being positive means that, when viewed from the tip, the second gash surface 43 is perpendicular to either the second portion 33, the central cutting edge 23, or the third cutting edge 37, and in each cross section parallel to the rotation axis O1, the second gash surface 43 inclines toward the rear in the rotation direction Y1 as it moves away from the second portion 33, the central cutting edge 23, or the third cutting edge 37.

[0066] As shown in Figures 11 and 12, the portion of the discharge groove 13 along the second cutting edge 35 that can function as a rake surface 39 for the second cutting edge 35 (for convenience of explanation, referred to as the third surface) may be configured such that the axial rake θ3 is a positive value, similar to the first gash surface 41 and the second gash surface 43.

[0067] In the drill 1 of this embodiment, in the cutting portion 7 (insert 1a), the axial rake θ3 of the third surface at a portion of the second cutting edge 35 that is relatively close to the rotation axis O1 may have a larger positive value than the axial rake θ3 of the third surface at a portion of the second cutting edge 35 that is relatively far (outer circumferential side) from the rotation axis O1.

[0068] <Other Configurations> In the drill 1 according to an embodiment of the present disclosure, when the body 3 has the second portion 33, the central cutting edge 23, and the third cutting edge 37 described above, the length of the central cutting edge 23 when viewed from the tip may be longer than the length of the second portion 33 and longer than the length of the third cutting edge 37. When the central cutting edge 23, which has a concave curved shape, is longer than the second portion 33 and the third cutting edge 37, which have a linear shape, the flow of chips generated at the central cutting edge 23 is less affected by the flow of chips generated at the second portion 33 and the third cutting edge 37, and therefore chip clogging is less likely to occur.

[0069] As described above, the second flank 17 may be smoothly connected to the first flank 15. Here, "smoothly connected" means that no ridge line is formed at the boundary between the two adjacent surfaces. When the second flank 17 is smoothly connected to the first flank 15, the inner cutting edge 21 located along the first flank 15 and the central cutting edge 23 located along the second flank 17 are smoothly connected.

[0070] In the example insert 1a shown in Fig. 2 etc., the second portion 33 of the inner cutting edge 21 is smoothly connected to the central cutting edge 23. In this case, cutting load is less likely to be concentrated at the boundary between the inner cutting edge 21 and the central cutting edge 23, and durability of the cutting edge 11 is improved.

[0071] Similarly, the second flank 17 may be smoothly connected to the third flank 19. When the second flank 17 is smoothly connected to the third flank 19, the outer cutting edge 25 located along the third flank 19 and the central cutting edge 23 located along the second flank 17 are smoothly connected. In the example shown in Fig. 2, the third cutting edge 37 of the outer cutting edge 25 and the central cutting edge 23 are smoothly connected. In this case, cutting load is less likely to concentrate on the boundary between the outer cutting edge 25 and the central cutting edge 23, improving the durability of the cutting edge 11.

[0072] As described above, the second cutting edge 35 has a concave curved shape. However, the radial rake of the second cutting edge 35 does not have to be constant. For example, as shown in Fig. 13, when the second cutting edge 35 has a first end 35a located on the inner circumferential side and a second end 35b located on the outer circumferential side, the radial rake φ3 of the second cutting edge 35 at the first end 35a may be negative, and the radial rake φ4 of the second cutting edge 35 at the second end 35b may be positive.

[0073] When the radial rake φ3 of the second cutting edge 35 at the first end 35a is a negative value, chips generated at the first end 35a tend to flow toward the outer periphery. Therefore, chips generated at the inner cutting edge 21 and the central cutting edge 23 tend to flow toward the discharge groove 13, and chips generated at the inner cutting edge 21 and the central cutting edge 23 are less likely to clog.

[0074] Furthermore, when the radial rake φ4 of the second cutting edge 35 at the second end 35b is a positive value, chips generated by the second cutting edge 35 tend to remain in the discharge groove 13 and are less likely to fly out to the outer periphery immediately after generation. Therefore, the machined hole in the workpiece is less likely to be damaged.

[0075] 2 and the like, the second flank 17 may have a surface configuration that approaches the rear end 3 b as it approaches the outer periphery, and in this case, the central cutting edge 23 may have a configuration that approaches the rear end 3 b as it approaches the outer periphery. Furthermore, when viewed from the tip, the central cutting edge 23 may have a negative radial rake (not shown) of an imaginary line connecting one end point connected to the inner cutting edge 21 and the other end point connected to the outer cutting edge 25.

[0076] The radial rake of the above virtual straight line at the central cutting edge 23 may be a negative value (absolute value) smaller than the radial rake φ2 at the second portion 33, and may be a negative value smaller than the radial rake φ1 at the first portion 31.

[0077] The third cutting edge 37 of the outer cutting edge 25 may have a negative radial rake (not shown) when viewed from the tip. The radial rake of the third cutting edge 37 may have a negative value that is smaller (in absolute value) than the radial rake of the central cutting edge 23.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] The surface of the main body 3 may be coated with a film by chemical vapor deposition (CVD) or physical vapor deposition (PVD). The film may have a composition such as titanium carbide (TiC), titanium nitride (TiN), titanium carbonitride (TiCN), and alumina (Al ２ O ３ ) and the like can be mentioned.

[0082] In the case where the drill 1 has the insert 1a and the holder 1b, the drill 1 may be replaced with the insert 1a, except for the part corresponding to the holder 1b in the description of the drill 1, the body 3, and the cutting portion 7. For example, the insert 1a in the present disclosure can be said to have the following configuration.

[0083] The insert 1a according to the present disclosure has a main body portion extending from the leading end 3a to the rear end 3b along the rotation axis O1. The main body portion has a flank 9 located at the leading end 3a, a cutting edge 11 located at the front edge of the flank 9 in the rotation direction Y1, and a discharge groove 13 extending from the cutting edge 11.

[0084] The flank 9 has a flat first flank 15 that extends from the rotation axis O1 toward the outer periphery and approaches the rear end 3b as it approaches the outer periphery, a second flank 17 that has a concave curved shape and extends from the first flank 15 toward the outer periphery, and a flat third flank 19 that extends from the second flank 17 toward the outer periphery and approaches the rear end 3b as it approaches the outer periphery.

[0085] The cutting edge 11 has an inner cutting edge 21 located along the first flank 15, a central cutting edge 23 located along the second flank 17, and an outer cutting edge 25 located along the third flank 19. The inner cutting edge 21 has a chisel edge 27 extending from the rotation axis O1 toward the outer periphery, and a first cutting edge 29 extending from the chisel edge 27 toward the outer periphery.

[0086] The central cutting edge 23 has a concave curved shape, and the outer cutting edge 25 has a second cutting edge 35 that also has a concave curved shape extending toward the outer periphery.

[0087] <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 Figures 14 to 16. 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).

[0088] (1) A step of placing the drill 1 above the prepared workpiece 103 (see FIG. 14).

[0089] (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 FIG. 14).

[0090] In the above 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 brought closer to the workpiece 103 while rotating. In step (2), the workpiece 103 and the drill 1 may be brought closer to each other, for example, the workpiece 103 may be brought closer to the drill 1.

[0091] (3) A process in which the rotating drill 1 is brought closer to the workpiece 103, thereby contacting the desired position on the surface of the workpiece 103 and forming a machining hole 105 in the workpiece 103 (see Figure 15).

[0092] 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 inside 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.

[0093] (4) Step of moving the drill 1 away from the workpiece 103 in the Y3 direction (see FIG. 16).

[0094] 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.

[0095] By going through the above steps, it is possible to obtain a machined product 101 having a highly accurate machined hole 105 .

[0096] In addition, 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 holding the drill 1 in a rotating state may be repeated.

[0097] Examples of the material of the workpiece 103 include aluminum, carbon steel, alloy steel, stainless steel, cast iron, and non-ferrous metals.

[0098] Summary: A drill according to a first aspect of the present disclosure has a rod-shaped body rotatable around a rotation axis and extending from a front end to a rear end along the rotation axis. The body has a flank located at the front end, a cutting edge located at a front edge of the flank in the rotation direction, and an ejection groove extending from the cutting edge. The flank has a flat first flank extending from the rotation axis toward the outer periphery and approaching the rear end as it approaches the outer periphery, a concavely curved second flank extending from the first flank toward the outer periphery, and a flat third flank extending from the second flank toward the outer periphery and approaching the rear end as it approaches the outer periphery. The cutting edges include an inner cutting edge located along the first flank, a central cutting edge located along the second flank, and an outer cutting edge located along the third flank. The inner cutting edge has a chisel edge extending from the rotation axis toward the outer periphery and a first cutting edge extending from the chisel edge toward the outer periphery. The central cutting edge has a concave curved shape, and the outer cutting edge has a second cutting edge that extends toward the outer periphery and has a concave curved shape.

[0099] The drill in aspect 2 of the present disclosure is based on aspect 1, and has the element that the outer cutting edge further has a third cutting edge having a linear shape extending from the central cutting edge toward the second cutting edge.

[0100] The drill of aspect 3 of the present disclosure is based on aspect 1 or 2, and has the following elements: the first cutting edge has a first portion that is a negative radial rake, and a second portion that is located more radially outward than the first portion and has a larger negative radial rake than the first portion.

[0101] A drill according to a fourth aspect of the present disclosure is based on any one of the first to third aspects, and has an element in which the first portion and the second portion are each linear.

[0102] The drill in aspect 5 of the present disclosure is based on any one of aspects 1 to 4, and has an element in which the body further has a flat first gash surface extending from the first portion, and the axial rake at the first gash surface is a positive value.

[0103] The drill in aspect 6 of the present disclosure is based on any one of aspects 1 to 5, and has an element in which the body further has a flat second gash surface extending from the second portion, the central cutting edge, and the third cutting edge.

[0104] A drill according to a seventh aspect of the present disclosure is based on the sixth aspect and has an element that the axial rake on the second gash surface is a positive value.

[0105] A drill according to an eighth aspect of the present disclosure is based on any one of the first to seventh aspects, and further includes an element in which the second flank surface is smoothly connected to the first flank surface.

[0106] A drill according to a ninth aspect of the present disclosure is based on any one of the first to eighth aspects, and further includes an element in which the second flank surface is smoothly connected to the third flank surface.

[0107] A drill in aspect 10 of the present disclosure is based on any one of aspects 1 to 9, and has the following elements: the second cutting edge has a first end located on the inner peripheral side and a second end located on the outer peripheral side; the radial rake of the second cutting edge at the first end is negative; and the radial rake of the second cutting edge at the second end is positive.

[0108] The drill in aspect 11 of the present disclosure is based on any one of aspects 1 to 10, and has an element in which at least a portion of the inner cutting edge is located closer to the tip than the rotation trajectory of an imaginary line extending the outer cutting edge toward the rotation axis.

[0109] A method for manufacturing a machined product in aspect 12 of the present disclosure includes a step of rotating a drill of any one of aspects 1 to 11 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.

[0110] [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.

[0111] DESCRIPTION OF SYMBOLS 1... Drill 1a... Insert 1b... Holder 3... Main body 5... Grip portion 7... Cutting portion 9... Flank surface 11... Cutting edge 13... Discharge groove 15... First flank surface 17... Second flank surface 19... Third flank surface 21... Inner cutting edge 23... Central cutting edge 25... Outer cutting edge 27... Chisel edge 29... First cutting edge 31... First portion 33... Second portion 35... Second cutting edge 35a... First end portion 35b... Second end portion 37... Third cutting edge 39... Rake face 41... First gash surface 43... Second gash surface 101... Cutting workpiece 103... Workpiece 105... Machined hole

Claims

1. a rod-shaped body that is rotatable around a rotation axis and extends from a front end to a rear end along the rotation axis; The body includes: a flank located at the tip; a cutting edge located at a front edge of the flank in a rotational direction; a discharge groove extending from the cutting edge; The flank surface is a flat first flank surface extending from the rotation axis toward the outer periphery and approaching the rear end as it approaches the outer periphery; a second flank surface having a concave curved shape extending from the first flank surface toward the outer periphery; a flat third flank surface extending from the second flank surface toward the outer periphery and approaching the rear end as it approaches the outer periphery, The cutting blade is an inner cutting edge located along the first flank surface; a central cutting edge located along the second flank; an outer cutting edge located along the third flank surface, The inner cutting edge is a chisel edge extending from the rotation axis toward the outer periphery; a first cutting edge extending from the chisel edge toward the outer periphery, The central cutting edge has a concave curved shape, The outer cutting edge has a second cutting edge that has a concave curved shape and extends toward the outer periphery.

2. The drill according to claim 1 , wherein the outer cutting edge further includes a third cutting edge having a linear shape extending from the central cutting edge toward the second cutting edge.

3. The first cutting edge is a first section having a negative radial rake; The drill according to claim 2 , further comprising: a second portion located radially outwardly of the first portion and having a greater negative radial rake than the first portion.

4. The drill according to claim 3 , wherein the first portion and the second portion are each linear.

5. the body further includes a first planar gash surface extending from the first portion; The drill according to claim 3 or 4, wherein the axial rake on the first gash surface is a positive value.

6. The drill of claim 3 or 4, wherein the body further comprises a second flat gash surface extending from the second portion, the central cutting edge, and the third cutting edge.

7. The drill of claim 6 , wherein the axial rake at the second gash surface is a positive value.

8. The drill according to any one of claims 1 to 4, wherein the second flank surface is smoothly connected to the first flank surface.

9. The drill according to any one of claims 1 to 4, wherein the second flank surface is smoothly connected to the third flank surface.

10. The second cutting edge is a first end portion located on the inner circumferential side; a second end portion located on the outer circumferential side, The radial rake of the second cutting edge at the first end is negative; The drill according to any one of claims 1 to 4, wherein the radial rake of the second cutting edge at the second end is positive.

11. The drill according to any one of claims 1 to 4, wherein at least a portion of the inner cutting edge is located closer to the tip than a rotation locus of an imaginary line extending the outer cutting edge toward the rotation axis.

12. A step of rotating the drill according to any one of claims 1 to 4 around the rotation axis; bringing the cutting edge of the rotating drill into contact with a workpiece; and a step of separating the drill from the workpiece.