Manufacturing methods for drills and cut workpieces

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

[Technical Field]

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

[0002] Conventionally, drills described in Patent Documents 1 and 2 are known as drills used for cutting workpieces such as metal members. Generally, a cutting edge of a drill has a chisel edge located at the innermost position and extending from a central axis. The chisel edge affects the straight running stability of the drill. The drill described in Patent Document 1 has one flank (secondary flank) as a flank for one cutting edge. The drill described in Patent Document 2 has two flanks as flanks for one cutting edge: a first tip flank located on the inner peripheral side and a second tip flank located on the outer peripheral side. [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Unexamined Patent Publication No. 2022-142055 [Patent Document 2] Japanese Unexamined Patent Publication No. 2020-175465 [Summary of the Invention]

[0004] An example drill, not limited to this disclosure, is rod-shaped and rotatable around a rotation axis, having a body extending along the rotation axis from a tip to a rear end. The body has a relief face located at the tip, a cutting edge located at the forward edge in the rotational direction of the relief face, and an evacuation groove extending from the cutting edge. The relief face has a flat first relief face extending outward from the rotation axis and approaching the rear end as it approaches the outer circumference, a concave curved second relief face extending outward from the first relief face, and a flat third relief face extending outward from the second relief face and approaching the rear end as it approaches the outer circumference. The cutting edge has an inner cutting edge located along the first relief face, a central cutting edge located along the second relief face, and an outer cutting edge located along the third relief face. The inner cutting edge has a chisel edge extending outward from the rotation axis and a first cutting edge extending outward from the chisel edge. The central cutting edge has a concave curve shape, and the outer cutting edge has a second cutting edge with a concave curve shape extending toward the outer circumference. [Brief explanation of the drawing]

[0005] [Figure 1] This is a perspective view showing a drill in one embodiment of the present disclosure. [Figure 2] Figure 1 is a perspective view showing the insert in the drill. [Figure 3] Figure 2 is a front view of the insert shown, seen from the tip side. [Figure 4] This is an enlarged view of region IV shown in Figure 3. [Figure 5] Figure 3 is a side view of the insert shown, viewed from direction A1. [Figure 6] Figure 3 is a side view of the insert shown, viewed from direction A2. [Figure 7] This is a cross-sectional view of the section along line VII-VII in Figure 4. [Figure 8] Figure 4 is a cross-sectional view taken along the line VIII-VIII. [Figure 9] Figure 4 is a cross-sectional view of the section along the line IX-IX. [Figure 10] Figure 4 is a cross-sectional view of the section along line XX. [Figure 11] Figure 4 is a cross-sectional view of the section between line XI-XI. [Figure 12] Figure 4 is a cross-sectional view of the section along line XII-XII. [Figure 13] This is an enlarged view of the same region shown in Figure 4. [Figure 14] This is a schematic diagram illustrating one step in a method for manufacturing a machined workpiece according to one embodiment of the present disclosure. [Figure 15] This is a schematic diagram illustrating one step in a method for manufacturing a machined workpiece according to one embodiment of the present disclosure. [Figure 16] This is a schematic diagram illustrating one step in a method for manufacturing a machined workpiece according to one embodiment of the present disclosure. [Modes for carrying out the invention]

[0006] Hereinafter, a drill according to an embodiment of this disclosure will be described in detail with reference to the drawings. However, for the sake of clarity, the drawings referenced below show only the main components of the embodiment that are necessary to explain the present invention. Therefore, the drill of this disclosure may have any components not shown in the drawings referenced. Furthermore, the dimensions of the components in each drawing do not faithfully represent the dimensions of the actual components or the dimensional ratios of each component.

[0007] Conventionally, for example, the drill described in Patent Document 1 has only one flat relief surface for each cutting edge. Therefore, there is a risk that the chisel edge will not adequately grip the workpiece after the main cutting edge has engaged. Also, in the drill described in Patent Document 2, the first tip relief surface extends over a wide area from the central axis toward the outer circumference. Therefore, similar to the drill described in Patent Document 1, there is a risk that the chisel edge will not adequately grip the workpiece after the main cutting edge has engaged.

[0008] The purpose of this disclosure is to provide a drill that can effectively engage the cutting edge with the workpiece.

[0009] <Outline of the drill's structure> The schematic configuration of the drill 1 in this embodiment will be described with reference to Figures 1 to 3. Figure 1 is a perspective view showing a drill in one embodiment of the present disclosure. Figure 2 is a perspective view showing the insert in the drill shown in Figure 1. Figure 3 is a front view of the insert shown in Figure 2, viewed from the tip side.

[0010] As shown in Figures 1-3, the drill 1 in one embodiment of the present disclosure has a rod-shaped body 3 that is rotatable around a rotation axis O1. The body 3 extends along the rotation axis O1 from the tip 3a to the rear end 3b. The body 3 in this embodiment includes a gripping portion 5 called a shank, which is gripped by a rotating spindle of a machine tool, and a cutting portion 7 called a body, which is located on the tip side of the gripping portion 5.

[0011] The gripping portion 5 is a part designed according to the shape of the spindle, etc., in the machine tool. The cutting portion 7 is the part that comes into contact with the workpiece and plays the main role in the cutting process of the workpiece. The arrow Y1 shown in Figure 1 indicates the rotation direction of the drill 1 (body 3).

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

[0013] In the drill 1 according to the present embodiment, the distal end portion including the flank 9 and the cutting edge 11 in the cutting portion 7 is configured to be detachable from the proximal end portion. In this case, the distal end portion is referred to as an insert 1a, and the combination of the proximal end portion of the cutting portion 7 and the gripping portion 5 is referred to as a holder 1b.

[0014] The drill 1 according to the present 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 handled as a part of the main body 3. Needless to say, as the drill 1 according to an example of the present disclosure, there is no problem even if the cutting portion 7 is not configured as described above but is formed of a single member (a so-called solid-type structure), 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] Hereinafter, the insert 1a of the drill 1 according to the present embodiment will be described in detail. 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 idea) of the insert 1a described below can also be applied to the solid-type cutting portion 7. In FIG. 2 and other drawings, the reference numeral of the cutting portion 7 is also indicated together with the insert 1a.

[0016] In the drill 1 according to the present embodiment, the plurality of flanks 9 on the insert 1a may each be in a rotationally symmetric positional relationship centered on the rotation axis O1, and the plurality of cutting edges 11 may also each be in a rotationally symmetric positional relationship centered on the rotation axis O1 in the same manner. Further, the plurality of discharge grooves 13 may also each be in a rotationally symmetric positional relationship centered on the rotation axis O1.

[0017] In the non-limiting exemplary drill 1 shown in FIG. 2, the three flanks 9 are positioned so as to be rotationally symmetric at 120°. Similarly, in the non-limiting example shown in FIG. 2, the three cutting edges 11 are positioned to be 120° rotationally symmetric, and the three discharge grooves 13 are positioned to be 120° rotationally symmetric.

[0018] Since the three relief surfaces 9 are configured to be rotationally symmetric, we will focus on one of the three relief surfaces 9 below and omit detailed explanations of the other two. Similarly, since the three cutting edges 11 and the three discharge grooves 13 are configured to be rotationally symmetric, we will focus on one of the three cutting edges 11 and one of the three discharge grooves 13 below and omit detailed explanations of the other two cutting edges 11 and the other two discharge grooves 13.

[0019] <Fleeing face> The relief surface 9 of the drill 1 in this embodiment will be described with reference to Figures 1-3 and Figure 4. Figure 4 is an enlarged view of region IV shown in Figure 3.

[0020] As shown in Figures 1-4, the drill 1 in this embodiment has a first relief surface 15, a second relief surface 17, and a third relief surface 19 as relief surfaces 9. In Figure 4, hatching is applied to these relief surfaces to facilitate visual understanding of the regions of the first relief surface 15, the second relief surface 17, and the third relief surface 19.

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

[0022] The second relief surface 17 and the third relief surface 19, located away from the axis of rotation O1, may each be inclined to approach the rear end 3b as they move towards the rear (opposite side of the rotation direction Y1) in the direction of rotation Y1. This angle of inclination is the so-called relief angle.

[0023] In the insert 1a shown in Figure 2 (not limited to this example), the first flank surface 15 and the second flank surface 17 are smoothly connected, and no ridges are formed at the boundary between these surfaces. Furthermore, in the insert 1a shown in Figure 2 (not limited to this example), the second flank surface 17 and the third flank surface 19 are smoothly connected, and no ridges are formed at the boundary between these surfaces. Note that "no ridges are formed at the boundary" means that the ridges are not discernible to the naked eye, and do not include ridges caused by microscopic irregularities such as surface roughness.

[0024] In Figure 2, etc., the parts corresponding to the boundary between the first relief surface 15 and the second relief surface 17, and the parts corresponding to the boundary between the second relief surface 17 and the third relief surface 19 are clearly indicated with solid lines to facilitate visual understanding.

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

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

[0027] Similarly, the second relief surface 17 may be considered to extend from the central cutting edge 23 toward the rear in the rotational direction Y1, and the third relief surface 19 may be considered to extend from the outer cutting edge 25 toward the rear in the rotational direction Y1. Note that the term "central cutting edge 23" indicates the relative positional relationship with respect to 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 the middle portion in the radial direction of the drill 1, nor is it limited to a configuration in which the middle portion in the longitudinal direction of the cutting edge 11 is included in the central cutting edge 23.

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

[0029] The inner cutting edge 21 has a chisel edge 27 and a first cutting edge 29. The chisel edge 27 extends outward from the axis of rotation O1. The chisel edge 27 is the part of the cutting edge 11 closest to the axis of rotation O1.

[0030] Normally, 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 place the rake face near the axis of rotation from the standpoint of ensuring sufficient core thickness of the main body. Therefore, near the axis of rotation, the cutting edge is formed by the intersection of multiple flank faces corresponding to multiple cutting edges. This area is called a chisel edge.

[0031] In the example shown in Figure 4, the chisel edge 27 is linear in shape. Furthermore, since the chisel edge 27 extends from the rotation axis O1 toward the outer circumference, when the cutting edge 11 is viewed from the tip side, in other words, when viewed from the tip side, the chisel edge 27 extends linearly along the radial direction from the point corresponding to the rotation axis O1, and the radial rake (radial rake angle) of the chisel edge 27 is 0.

[0032] The first cutting edge 29 extends outward from the chisel edge 27. As mentioned above, the chisel edge 27 is formed by the intersection of multiple relief faces 9, while the first cutting edge 29 is formed by the intersection of the first relief face 15 and the rake face. The presence of the first cutting edge 29 in the inner cutting edge 21 makes it easier to secure a wide rake face area. It also makes it easier to make the chisel edge 27 protrude towards the tip. Therefore, the chisel edge 27 can stably bite into the workpiece.

[0033] The first cutting edge 29 may be composed of, for example, a single linear portion, or it may be composed of multiple portions, as in the example shown in Figure 4. In the example shown in Figure 4, the first cutting edge 29 has a first portion 31 and a second portion 33. The first portion 31 is located closer to the axis of rotation O1 than the second portion 33, and the second portion 33 is located further outward than the first portion 31. The first portion 31 and the second portion 33 may each be linear in shape.

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

[0035] When the radial rake φ1 in the first part 31 and the radial rake φ2 in the second part 33 are different values, the cutting load applied to the first part 31 and the cutting load applied to the second part 33 are partially canceled out, as is evident from the vector sum of the directions of the cutting load applied to the first part 31 and the cutting load applied to the second part 33.

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

[0037] In particular, when the first part 31 and the second part 33 are both linear in shape, the cutting load is less likely to concentrate on specific parts of the first part 31 and the second part 33, thus further enhancing the durability of the cutting edge 11.

[0038] A negative radial rake value means that, when viewed from the tip, the portion of the cutting edge 11 is inclined radially so as it approaches the outer circumference, it moves towards the rear in the rotational direction Y1. A positive radial rake value means that, when viewed from the tip, the portion of the cutting edge 11 is inclined radially so as it approaches the outer circumference, it moves towards the front in the rotational direction Y1.

[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 a first portion 31 and a 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 cases, there is a risk that the cutting load will concentrate at the boundary between the first part 31 and the second part 33. Here, if the first part 31 is longer than the second part 33, the above boundary is likely to be located on the outer circumference side of the first cutting edge 29. The closer it is to the outer circumference, the faster the cutting speed becomes and the better the cutting performance, thus improving the durability of the first cutting edge 29.

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

[0042] Furthermore, the central cutting edge 23 has a concave curve shape that is recessed toward the rear end 3b when viewed from the front in the rotation direction Y1 (see Figures 2, 5, and 6). Here, the central cutting edge 23 may be configured such that the radius of curvature when viewed from the front in the rotation direction Y1 is smaller than the radius of curvature when viewed from the tip.

[0043] (Outer cutting edge) The outer cutting edge 25, located along the third relief surface 19 in the forward direction of rotation Y1, has a second cutting edge 35 with a concave curve shape extending toward the outer circumference. When viewed from the tip, the second cutting edge 35 has a concave curve shape that is recessed toward the rear in the direction of rotation 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 material cut by the outer cutting edge 25 is greater than that cut 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 part 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 curve shape that is recessed toward the rear in the rotation direction Y1 when viewed from the tip. Also, when viewed from the front in the rotation direction Y1, the second cutting edge 35 has a concave curve shape that is slightly recessed toward the rear end 3b (see Figures 2, 5, and 6). Here, the second cutting edge 35 may have a configuration in which the radius of curvature when viewed from the tip is smaller than the radius of curvature when viewed from the front in the rotation direction Y1.

[0046] Since the third relief surface 19 has a surface configuration that approaches the rear end 3b as it approaches the outer circumference, the outer cutting edge 25 also has a configuration that approaches the rear end 3b as it approaches the outer circumference. Therefore, the third relief surface 19 is inclined to approach the rear end 3b as it approaches the outer circumference, and the outer cutting edge 25 also has a configuration that is inclined to approach the rear end 3b as it approaches the outer circumference. 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 straight-line stability of the drill 1 is easily ensured.

[0047] As described above, in the drill 1 of this disclosure, the inner cutting edge 21 located along the first relief surface 15 has a first cutting edge 29 in addition to the chisel edge 27. Therefore, the chisel edge 27 protrudes easily toward the tip, and the chisel edge 27 bites into the workpiece well. Furthermore, since the third relief surface 19 is inclined to approach the rear end 3b as it approaches the outer circumference, the outer cutting edge 25 is also inclined to approach the rear end 3b as it approaches the outer circumference. Therefore, good straight-line stability of the drill 1 is ensured even when the outer cutting edge 25 bites into the workpiece.

[0048] In the drill 1 of this disclosure, at least a portion of the inner cutting edge 21 may be located on the tip 3a side of the rotational trajectory of a virtual line extending the outer cutting edge 25 toward the rotational axis O1. Specifically, when the outer cutting edge 25 is viewed from the front in the rotational direction Y1 (see, for example, Figures 5 and 6), a tangent line of the outer cutting edge 25 at the end passing through the end of the outer cutting edge 25 on the rotational axis O1 side is defined.

[0049] This tangent is the virtual line described above, and the rotational trajectory of this virtual line around the rotation axis O1 is defined. At this time, at least a portion of the inner cutting edge 21 may be located on the side of the tip 3a that is further along this rotational trajectory. When the cutting edge 11 is configured in this way, the chisel edge 27 tends to protrude towards the tip, and even when the outer cutting edge 25 bites into the workpiece, the chisel edge 27 tends to bite into the workpiece stably.

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

[0051] In the concave curved shape of the central cutting edge 23 and the second cutting edge 35, the cutting load is not easily distributed. Therefore, when the central cutting edge 23 and the second cutting edge 35, which are both concave curved shapes, are connected, there is a risk that an excessively large cutting load will be applied near the boundary between the central cutting edge 23 and the second cutting edge 35. However, if 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. Therefore, the durability of the cutting edge 11 is improved.

[0052] Furthermore, when the central cutting edge 23 and the second cutting edge 35, which have a concave curve shape, are connected, the angle at which the central cutting edge 23 and the second cutting edge 35 intersect tends to be small. In other words, the boundary between the central cutting edge 23 and the second cutting edge 35 tends to be sharp, and there is a risk that constraints on cutting conditions (e.g., rotational speed, feed rate, etc.) will increase in consideration of the 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 described above, it is less likely that such a sharp part will be formed on the cutting edge 11, and thus the durability of the cutting edge 11 is improved from this viewpoint as well.

[0053] <Discharge channel, scoop surface> The discharge groove 13 of the drill 1 in this embodiment will be described with reference to Figures 1-6, 13, and Figures 7-12. Figure 7 is a cross-sectional view taken along the line VII-VII in Figure 4. Figure 8 is a cross-sectional view taken along the line VIII-VIII in Figure 4. Figure 9 is a cross-sectional view taken along the line IX-IX in Figure 4. Figure 10 is a cross-sectional view taken along the line XX in Figure 4. Figure 11 is a cross-sectional view taken along the line XI-XI in Figure 4. Figure 12 is a cross-sectional view taken along the line XII-XII in Figure 4.

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

[0055] The discharge groove 13 is 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 shown in the example in Figure 1, the discharge groove 13 may be formed only in the cutting section 7 and not in the gripping section 5. The discharge groove 13 may extend spirally around the rotation axis O1, as shown in the example that is not limited to Figure 1.

[0056] The insert 1a (cutting portion 7) may have a rake face 39 located along the portion of the cutting edge 11 excluding the chisel edge 27. In one example of the insert 1a shown in Figure 2, a 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 a rake face 39 relative to the second cutting edge 35.

[0057] In the example shown in Figure 5, the discharge groove 13 can function as a rake face 39 for the second cutting edge 35. As is clear from Figure 2 and other figures, since the discharge groove 13 has a concave curved shape, the second cutting edge 35, located at the intersection of the flat third relief surface 19 and the discharge groove 13, can be represented by a concave curved shape.

[0058] Generally, the groove that forms the bottom cutting edge is sometimes called a gash, and as shown in one example in Figure 2, the drill 1 in this embodiment may have a flat first gash surface 41 extending from the first portion 31 toward the rear end 3b. The first gash surface 41 can function as a rake face 39 relative to the first portion 31.

[0059] As shown in Figure 7, in one example of insert 1a, the axial rake θ1 of the first gash surface 41 may be positive. As mentioned above, the chisel edge 27 adjacent to the first portion 31 is located on the ridge where the two relief surfaces 9 intersect, making it difficult for chips to be discharged from the chisel edge 27. Here, when the first gash surface 41 has the above configuration, the chips generated at the chisel edge 27 are easily discharged through the first gash surface 41. Therefore, chip clogging is less likely to occur.

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

[0061] Furthermore, in the drill 1 of this embodiment, as shown in one example in Figure 2, the cutting portion 7 (insert 1a) 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 can function as a rake surface 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 curve shape, and the second section 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 speed at the second section 33, the central cutting edge 23, and the third cutting edge 37 is slower than the cutting speed at the second cutting edge 35. Consequently, the chip flow generated at the second section 33, the central cutting edge 23, and the third cutting edge 37 is more prone to stagnation than the chip flow generated at the second cutting edge 35.

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

[0064] In this case, as shown in the example in Figures 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] Furthermore, a positive axial rake θ2 of the second gash surface 43 means that, when viewed from the tip, in each cross-section perpendicular to any of the second portion 33, the central cutting edge 23, and the third cutting edge 37, and parallel to the axis of rotation O1, the second gash surface 43 is inclined toward the rear in the rotation direction Y1 as it moves away from the second portion 33, the central cutting edge 23, and the third cutting edge 37.

[0066] As shown in Figures 11 and 12, the portion of the discharge groove 13 that can function as a rake face 39 relative to the second cutting edge 35 (referred to as the third surface for convenience of explanation) may have a configuration in which 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, the axial rake θ3 of the third surface of the second cutting edge 35 in a portion relatively close to the rotation axis O1 may have a larger positive value than the axial rake θ3 of the third surface of the second cutting edge 35 in a portion relatively far from the rotation axis O1 (on the outer circumference).

[0068] <Other configurations> In one embodiment of the present disclosure, when the main body 3 has the second portion 33, the central cutting edge 23, and the third cutting edge 37 as 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 curve shape, is longer than the second portion 33 and the third cutting edge 37, the chip flow generated at the central cutting edge 23 is less affected by the chip flow generated at the second portion 33 and the third cutting edge 37, so chip clogging is less likely to occur.

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

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

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

[0072] As described above, the second cutting edge 35 has a concave curve shape. Here, the radial rake of the second cutting edge 35 does not have to be constant. As shown in Figure 13, for example, if the second cutting edge 35 has a first end 35a located on the inner circumference side and a second end 35b located on the outer circumference 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, the chips generated at the first end 35a tend to flow towards the outer circumference. As a result, the chips generated at the inner cutting edge 21 and the central cutting edge 23 tend to flow into the discharge groove 13, and the 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, the 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 circumference immediately after being generated. As a result, the machined hole in the workpiece is less likely to be damaged.

[0075] Furthermore, in the insert 1a shown in Figure 2 and other examples, the second relief surface 17 may have a surface configuration that approaches the rear end 3b as it approaches the outer circumference, and in this case, the central cutting edge 23 may have a configuration that approaches the rear end 3b as it approaches the outer circumference. Also, when viewed from the tip, the radial rake (not shown) of the imaginary straight line connecting one endpoint connected to the inner cutting edge 21 and the other endpoint connected to the outer cutting edge 25 may be a negative value.

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

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

[0078] In this embodiment, the drill 1 is configured such that the outer diameter of the cutting portion 7 is set to 6 mm to 42.5 mm. Also, in this embodiment, the drill 1 is configured such that, for example, when the length of the axis (length of the cutting portion 7) is L and the diameter (outer diameter of the cutting portion 7) is D, L is set to 1D to 12D.

[0079] Examples of materials for the main body 3 include cemented carbide and cermet. Examples of cemented carbide compositions 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 bonding phase.

[0080] The cermet may be a sintered composite material in which a metal is compounded with a ceramic component. 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 using chemical vapor deposition (CVD) or physical vapor deposition (PVD). Examples of the film composition include titanium carbide (TiC), titanium nitride (TiN), titanium carbonitride (TiCN), and alumina (Al2O3).

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

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

[0084] The relief surface 9 includes a flat first relief surface 15 extending from the rotation axis O1 toward the outer circumference and approaching the rear end 3b as it approaches the outer circumference, a concave curved second relief surface 17 extending from the first relief surface 15 toward the outer circumference, and a flat third relief surface 19 extending from the second relief surface 17 toward the outer circumference and approaching the rear end 3b as it approaches the outer circumference.

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

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

[0087] <Method for manufacturing machined parts> Next, a method for manufacturing a one-sided machined workpiece 101, not limited to the present disclosure, will be described with reference to Figures 14 to 16. The machined workpiece 101 may be produced by machining a workpiece 103. The method for manufacturing the machined workpiece 101 may include the following steps (1) to (4).

[0088] (1) The step of positioning the drill 1 above the prepared workpiece 103 (see Figure 14).

[0089] (2) The drill 1 is rotated around the rotation axis O1 in the direction of arrow Y1, and the drill 1 is brought closer to the workpiece 103 in the Y2 direction (see Figure 14).

[0090] Steps (1) and (2) described above may be carried out by, for example, fixing the workpiece 103 on the table of a machine tool to which the drill 1 is attached, and bringing the drill 1 closer to the workpiece 103 while it is rotating. In step (2), the workpiece 103 and the drill 1 only need to be relatively close to each other; for example, the workpiece 103 may be brought closer to the drill 1.

[0091] (3) The step of bringing the drill 1 closer to the workpiece 103 so that the rotating drill 1 can be brought into contact with a desired position on the surface of the workpiece 103, thereby forming a machined hole 105 in the workpiece 103 (see Figure 15).

[0092] In step (3) described above, cutting may be performed such that at least a portion of the cutting portion 7 in the main body 3 is located inside the machining hole 105. Also, in step (3), the gripping portion 5 in the main body 3 may be set to be located outside the machining hole 105. From the viewpoint of obtaining a good finished surface, a portion of the cutting portion 7 on the side of the rear end 3b may be set to be located outside the machining hole 105. This portion can be made to function as a margin area for chip evacuation, and excellent chip evacuation performance can be achieved through this area.

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

[0094] In step (4) described above, as in step (2) described above, the workpiece 103 and the drill 1 only need to be separated relatively; for example, the workpiece 103 may be separated from the drill 1.

[0095] By following the above process, it is possible to obtain a machined workpiece 101 having a highly accurate machined hole 105.

[0096] Furthermore, when the workpiece 103 is cut multiple times, for example, when forming multiple machined holes 105 in a single workpiece 103, the process of bringing the cutting edge 11 of the drill 1 into contact with different locations on the workpiece 103 while maintaining the rotational state of the drill 1 may be repeated.

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

[0098] <Summary> A drill in embodiment 1 of the present disclosure is rod-shaped and rotatable around a rotation axis, and has a body extending along the rotation axis from a tip to a rear end. The body has a relief surface located at the tip, a cutting edge located at the forward edge in the rotational direction of the relief surface, and an ejection groove extending from the cutting edge. The relief surface has a flat first relief surface extending from the rotation axis toward the outer circumference and approaching the rear end as it approaches the outer circumference, a concave curved second relief surface extending from the first relief surface toward the outer circumference, and a flat third relief surface extending from the second relief surface toward the outer circumference and approaching the rear end as it approaches the outer circumference. The cutting edge has an inner cutting edge located along the first relief surface, a central cutting edge located along the second relief surface, and an outer cutting edge located along the third relief surface. The inner cutting edge has a chisel edge extending from the rotation axis toward the outer circumference, and a first cutting edge extending from the chisel edge toward the outer circumference. The central cutting edge has a concave curve shape, and the outer cutting edge has a second cutting edge with a concave curve shape extending toward the outer circumference.

[0099] A drill in aspect 2 of the present disclosure is based on aspect 1, wherein the outer cutting edge further has a linear third cutting edge extending from the central cutting edge toward the second cutting edge.

[0100] A drill in aspect 3 of the present disclosure is based on aspect 1 or 2, wherein the first cutting edge has a first portion which is a negative radial rake and a second portion which is located more circumferentially than the first portion and has a larger negative radial rake than the first portion.

[0101] The drill in aspect 4 of the present disclosure is based on any one of aspects 1 to 3, and the first portion and the second portion are each linear in shape.

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

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

[0104] The drill in aspect 7 of the present disclosure is based on aspect 6 and has the element that the axial rake on the second gash surface is a positive value.

[0105] The drill in aspect 8 of the present disclosure is based on any one of aspects 1 to 7, wherein the second relief surface is smoothly connected to the first relief surface.

[0106] The drill in aspect 9 of the present disclosure is based on any one of aspects 1 to 8, wherein the second relief surface is smoothly connected to the third relief surface.

[0107] A drill in aspect 10 of the present disclosure is based on any one of aspects 1 to 9, wherein the second cutting edge has a first end located on the inner circumference and a second end located on the outer circumference, wherein 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] A drill in aspect 11 of the present disclosure is based on any one of aspects 1 to 10, and has the element that at least a portion of the inner cutting edge is located on the tip side of the rotational trajectory of a virtual line extending the outer cutting edge toward the axis of rotation.

[0109] A method for manufacturing a machined workpiece according to aspect 12 of the present disclosure includes the steps of: rotating a drill according to any one of aspects 1 to 11 around a rotating shaft; bringing the cutting edge of the rotating drill into contact with a workpiece; and moving the drill away from the workpiece.

[0110] [Additional notes] The inventions described in this disclosure have been explained based on the drawings and embodiments described above. However, the inventions described in this disclosure are not limited to the embodiments described above. That is, the inventions described in this disclosure can be modified in various ways within the scope shown in this disclosure, and embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the inventions described in this disclosure. In other words, it should be noted that it is easy for those skilled in the art to make various modifications or alterations based on this disclosure. Furthermore, it should be noted that these modifications or alterations are included in the scope of this disclosure. [Explanation of Symbols]

[0111] 1. Drill 1a ·· Insert 1b ··Holder 3. Main unit 5...Gripping part 7...Cutting part 9. Escape 11... Cutting edge 13...Discharge groove 15...First escape route 17...Second escape route 19...Third escape scene 21...Inner cutting edge 23...Central cutting edge 25...Outer cutting edge 27... Chisel Edge 29...First cutting edge 31...1st part 33...Second part 35...Second cutting edge 35a...1st end 35b...Second end 37...Third cutting edge 39... Scoop surface 41...First Gash Surface 43...Second Gash Surface 101...Cutting workpiece 103...Work material 105... Machining hole

Claims

1. A rod-shaped object that can rotate around a rotation axis, having a body that extends from the tip to the rear end along the rotation axis, The aforementioned main body is The relief surface located at the aforementioned tip, A cutting edge located at the front edge in the rotational direction of the flank surface, It has a discharge groove extending from the cutting edge, The aforementioned relief surface is, A flat first relief surface extending from the rotation axis toward the outer circumference, and approaching the outer circumference and becoming closer to the rear end, A second relief surface having a concave curved shape extending from the first relief surface toward the outer circumference, It has a flat third relief surface that extends from the second relief surface toward the outer circumference and approaches the rear end as it approaches the outer circumference, The aforementioned cutting edge is An inner cutting edge positioned along the first relief surface, A central cutting edge located along the second relief surface, It has an outer cutting edge located along the third relief surface, The aforementioned inner cutting edge is A chisel edge extending from the rotation axis toward the outer circumference, It has a first cutting edge extending outward from the chisel edge, The aforementioned outer cutting edge has a second cutting edge that extends toward the outer circumference, A drill in which the central cutting edge and the second cutting edge have a concave curve shape when viewed from the tip side and also have a concave curve shape when viewed from the front side in the direction of rotation.

2. The drill according to claim 1, wherein the outer cutting edge further has a third cutting edge that is linear in shape and extends from the central cutting edge toward the second cutting edge.

3. The first cutting edge is, The first part is a negative radial rake, The drill according to claim 2, further comprising: a second portion located on the outer circumference of the first portion and having a negative radial rake larger than that of the first portion.

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

5. The main body further has a flat first 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 according to claim 3 or 4, wherein the body further has a flat second gash surface extending from the second portion, the central cutting edge, and the third cutting edge.

7. The drill according to claim 6, wherein the axial rake on the second gash surface is a positive value.

8. The drill according to any one of claims 1 to 4, wherein the first relief surface and the second relief surface are connected to each other without a ridge being formed at the boundary between the first relief surface and the second relief surface.

9. The drill according to any one of claims 1 to 4, wherein the second relief surface and the third relief surface are connected to each other without a ridge being formed at the boundary between the second relief surface and the third relief surface.

10. The aforementioned second cutting edge is The first end located on the inner circumference, It has a second end located on the outer periphery, 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. When viewing the outer cutting edge from the front side in the direction of rotation, the virtual tangent line of the outer cutting edge at the end of the outer cutting edge on the rotation axis side is taken as a virtual line, The drill according to any one of claims 1 to 4, wherein at least a portion of the inner cutting edge is located on the tip side of the rotational trajectory of the imaginary line around the axis of rotation.

12. A step of rotating the drill according to any one of claims 1 to 4 around the rotating shaft, A step of bringing the cutting edge of the rotating drill into contact with the workpiece, A method for manufacturing a cut workpiece, comprising the step of separating the drill from the workpiece.

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