Drill and manufacturing method of cutting workpiece

Abstract

Provided is a drill of which chip-discharge performance is improved, while an influence on an inner peripheral surface of a processed hole is suppressed.　The drill (1) has a main body (3) extending from a tip end (3a) toward a rear end (3b) along a rotation axis (O1). The main body has a first cutting blade (13) and a first discharge groove having a first portion and a second portion. In a cross section of the first discharge groove orthogonal to the rotation axis, assuming that an angle formed by a virtual straight line connecting the rotation axis and a front end part and a virtual straight line connecting the rotation axis and a return end part is set as a return amount, the return amount in the first portion is larger than the return amount in the second portion.

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 to 3 are known as drills used for cutting workpieces such as metal members. The drills described in these Patent Documents each have a cutting edge and a discharge flute. Furthermore, the discharge flutes described in these Patent Documents have a radial width that is not constant but varies in the direction along the rotation axis in order to improve chip discharge performance.

[0003] Japanese Unexamined Patent Publication No. 09-277108 Japanese Unexamined Patent Publication No. 2004-090197 Japanese Special Publication No. 2022-512198

[0004] A non-limiting example of a drill in the present disclosure has a rod-like shape rotatable around a rotation axis and a body extending from a front end to a rear end along the rotation axis. The body has a first cutting edge located at the front end and a first discharge flute extending from the first cutting edge. The first discharge flute has a first portion located toward the front end and a second portion located toward the rear end of the first portion. In this case, in a cross section of the first discharge flute perpendicular to the rotation axis, the end of the first discharge flute located most forward in the rotation direction of the rotation axis is referred to as the front end, the portion of the first discharge flute extending from the front end to the heel end is referred to as the outer portion, and the end of the outer portion located most rearward in the rotation direction is referred to as the barb end. The angle formed by an imaginary line connecting the rotation axis and the front end and an imaginary line connecting the rotation axis and the barb end is referred to as the barb amount. In this case, the barb amount in the first portion is greater than the barb amount in the second portion.

[0005] 1 is a perspective view showing a drill according to an embodiment of the present disclosure; FIG. 2 is an enlarged view of region II shown in FIG. 1; FIG. 2 is a view of the drill shown in FIG. 1 as viewed from the tip side; FIG. 3 is a side view of the drill shown in FIG. 3 as viewed from direction IV; FIG. 4 is an enlarged view of region V shown in FIG. 4; FIG. 3 is a side view of the drill shown in FIG. 3 as viewed from direction VI; FIG. 6 is a cross-sectional view of the drill shown in FIG. 6 taken along line VII-VII; FIG. 6 is a cross-sectional view of the drill shown in FIG. 6 taken along line VIII-VIII; FIG. 6 is a cross-sectional view of the drill shown in FIG. 6 taken along line IX-IX; FIG. 7 is the same cross-sectional view as FIG. 7; FIG. 8 is the same cross-sectional view as FIG. 8; FIG. 9 is a schematic diagram showing one step of a method for manufacturing a machined product according to an embodiment of the present disclosure; FIG. 10 is a schematic diagram showing one step of a method for manufacturing a machined product according to an embodiment of the present disclosure; FIG. 11 is a schematic diagram showing one step of 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 referred to in this specification. 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, chips generated at the tip of a drill are sent from the tip to the rear end through the discharge flute and discharged to the outside at the rear end of the discharge flute. However, for example, the drills described in Patent Documents 1 to 3 only focus on simply improving chip discharge performance. Therefore, there is a risk that chips will fly out before reaching the rear end of the discharge flute. This can cause damage to the inner surface of the drilled hole.

[0008] An aspect of the present disclosure aims to provide a drill that has improved chip discharge properties while minimizing the impact on the inner surface of a drilled hole.

[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 an enlarged view of region II 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 example 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 tip end 3a to a rear end 3b along the rotation axis O1. In this embodiment, the main body 3 includes a gripping portion 5 called a shank that is gripped by a rotating spindle of a machine tool or the like, and a cutting portion 7 called a body that is located on the tip end 3a 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. Note that the arrow Y1 shown in Figure 1 indicates the rotation direction Y1 of the drill 1 (body 3).

[0012] In the drill 1 of this embodiment, the portion of the cutting portion 7 on the side of the tip 3a is detachable from the portion on the side of the rear end 3b. In this case, the portion of the body 3 on the side of the tip 3a is called an insert 9, and the portion of the body 3 on the side of the rear end 3b is called a holder 11. Of course, in the drill 1 according to the example of the present disclosure, there is no problem even if the body 3 is configured as a single member rather than as described above, that is, as generally known as a solid drill.

[0013] The drill 1 having a main body 3 with an insert 9 attached to a holder 11 will be described in detail below. In the following description, the main body 3, cutting portion 7, and insert 9 may be interchanged as long as there is no contradiction. The configuration (technical concept) of the main body 3 having the insert 9 described below can also be applied to a main body 3 (or cutting portion 7) having the configuration of a solid drill. In Figure 2 and other figures, the reference symbol for the main body 3 is written alongside the drill 1.

[0014] The body 3 (cutting portion 7 or insert 9) has a cutting edge 13 located at a tip 3a and a discharge groove 15 extending from the cutting edge 13. The body 3 also has a flank 17 located at the tip 3a. The cutting edge 13 is located at the front edge of the flank 17 in the rotational direction Y1. In other words, the flank 17 extends from the cutting edge 13 toward the rear in the rotational direction Y1 (the opposite side to the rotational direction Y1).

[0015] The number of flanks 17, cutting edges 13, and discharge flutes 15 is not limited to a specific number. In the drill 1 in a non-limiting example shown in Figure 2, the cutting portion 7 has three flanks 17, three cutting edges 13, and three discharge flutes 15, which is a so-called three-flute drill configuration. In the drill 1 in the example of the present disclosure, there is no problem even if the cutting portion 7 has two flanks 17, two cutting edges 13, and two discharge flutes 15, which is a so-called two-flute drill configuration.

[0016] The multiple flanks 17, cutting edges 13, and discharge flutes 15 may be positioned in a rotationally symmetrical relationship about the rotation axis O1. In the non-limiting example of the drill 1 (insert 9) shown in Fig. 3, three flanks 17 are positioned to have 120° rotational symmetry. Similarly, in the non-limiting example shown in Fig. 3, three cutting edges 13 are positioned to have 120° rotational symmetry, and three discharge flutes 15 are positioned to have 120° rotational symmetry.

[0017] Since the three flanks 17 have a rotationally symmetrical configuration, attention will be focused on one of the three flanks 17, and detailed description of the other two flanks 17 will be omitted. Similarly, since the three cutting edges 13 and the three discharge grooves 15 each have a rotationally symmetrical configuration, attention will be focused on one of the three cutting edges 13 and one of the three discharge grooves 15. Hereinafter, the cutting edge 13 and discharge groove 15 of interest will be referred to as the first cutting edge 13a and the first discharge groove 19. There is no problem if the other two cutting edges 13 and two discharge grooves 15 have the configurations described below.

[0018] The first cutting edge 13a is located at the tip 3a of the main body 3, and extends from the rotation axis O1 toward the outer periphery when the main body 3 is viewed from the tip 3a side, in other words, when viewed from the tip.

[0019] Typically, the cutting edge 13 is located at the intersection of the flank 17 and the rake face. However, when there are multiple cutting edges 13, it may be difficult to provide a rake face near the rotation axis O1 in order to ensure the core thickness of the main body 3. Therefore, near the rotation axis O1, the cutting edge 13 is formed by the intersection of multiple flanks 17 corresponding to the multiple cutting edges 13. Such a portion is called a chisel edge 21. For example, the portion of the first cutting edge 13a located near the rotation axis O1 is the chisel edge 21.

[0020] <Details of Drill> The drill 1 of this embodiment will be described in detail with reference to Figures 4 to 11 as well as Figures 1 to 3. Figure 4 is a side view of the drill shown in Figure 2 as viewed from direction IV. Figure 5 is an enlarged view of region V shown in Figure 4. Figure 6 is a side view of the drill shown in Figure 2 as viewed from direction VI. Figure 7 is a cross-sectional view of the drill shown in Figure 6 taken along line VII-VII. Figure 8 is a cross-sectional view of the drill shown in Figure 6 taken along line VIII-VIII. Figure 9 is a cross-sectional view of the drill shown in Figure 6 taken along line IX-IX. Figure 10 is the same cross-sectional view as Figure 7. Figure 11 is the same cross-sectional view as Figure 8.

[0021] As shown in Figures 1 to 11, the first discharge groove 19 of the cutting portion 7 extends from the first cutting edge 13a toward the rear end 3b. The first discharge groove 19 is a portion used to discharge chips generated by the first cutting edge 13a to the outside. The first discharge groove 19 does not need to extend to the rear end 3b of the main body 3. As shown in an example in Figure 1, the first discharge groove 19 may be formed only in the cutting portion 7 and not in the grip portion 5. As shown in a non-limiting example in Figure 1, the first discharge groove 19 may extend spirally around the rotation axis O1.

[0022] 5, the first discharge flute 19 has a first portion 23 located on the leading edge 3a side and a second portion 25 located on the rear end 3b side of the first portion 23. In the drill 1 of this embodiment, as shown in FIG. 5, the first portion 23 may include a flute extending from the rake face located along the outer peripheral portion of the first cutting edge 13a of the insert 9 toward the rear end 3b, and a flute located on the leading edge 3a side of the holder 11.

[0023] Here, in a cross section S (for example, the cross section shown in Figures 7 to 11) perpendicular to the rotation axis O1 of the drill 1 of this embodiment, the front end 27, outer portion 29, return end 31 and return amount θ for the first discharge groove 19 are defined as follows.

[0024] The front end 27 is the end of the first discharge groove 19 that is located most forward in the rotation direction Y1 of the rotation axis O1 in the cross section S. The front end 27 is identified for each cross section. Specifically, in each cross section, the front end 27 is the point of contact when a tangent is drawn from the center point corresponding to the rotation axis O1 to a concave curve corresponding to the surface of the first discharge groove 19.

[0025] The outer region 29 is the region of the first discharge groove 19 extending from the front end 27 to the heel-side end 32 (see FIGS. 7 and 8 ) in the cross section S. At least a portion of the outer region 29 is formed so as to be positioned rearward in the rotational direction Y1 as it extends from the front end 27 toward the outer periphery, and has a so-called “barbed (hooking)” configuration.

[0026] The "heel-side end 32" refers to the end of the first discharge groove 19 that forms the opening and that is located forward in the rotational direction Y1 in the cross section S. Specifically, in the cross section S (a cross section perpendicular to the rotation axis O1 of the drill 1), the portion where the first discharge groove 19 and the outer peripheral surface of the body 3 intersect is the edge (rim) of the opening formed by the first discharge groove 19.

[0027] The opening of the first discharge groove 19 has two edges, one located in front of the rotational direction Y1 and the other located in the rear of the rotational direction Y1. Of the two edges of the opening in the cross section S, the one located in front of the rotational direction Y1 is the "heel-side end 32."

[0028] The return end 31 is the end of the outer portion 29 that is located furthest rearward in the rotational direction Y1 on the cross section S. The return amount θ is the angle between an imaginary line connecting the rotation axis O1 and the front end 27 and an imaginary line connecting the rotation axis O1 and the return end 31. In this case, as shown in Figures 7 and 8, the return amount θ1 in the first portion 23 may be greater than the return amount θ2 in the second portion 25.

[0029] In the drill 1 of this embodiment, the front end 27, the outer region 29, and the barb end 31 are each specified as part of the holder 11. When the first discharge flute 19 has the outer region 29, the outer region 29 can act as a barrier to prevent chips from flying out. This makes it difficult for chips to fly out unintentionally, and reduces the impact of chips on the inner surface of the drilled hole.

[0030] In particular, chips flow into the first portion 23 located on the tip 3a side of the first discharge groove 19 soon after they are generated by the first cutting edge 13a, making the flow of the chips unstable. However, the return amount θ1 in this first portion 23 is relatively large. This makes it difficult for chips to accidentally fly out. In addition, in the first portion 23, chips tend to curl due to the outer portion 29. This makes it easy for chips to gather together and be sent through the first discharge groove 19 from the tip 3a side to the rear end 3b side.

[0031] Furthermore, since the return amount θ2 in the second portion 25 is relatively small, chips are easily discharged to the outside on the rear end 3b side. In this way, when the return amount θ1 in the first portion 23 is larger than the return amount θ2 in the second portion 25, chip discharge is improved while suppressing the impact on the inner peripheral surface of the machined hole.

[0032] Note that, since it is sufficient that the amount of return θ2 in the second portion 25 is relatively small, the amount of return θ2 in the second portion 25 may be 0, i.e., the outer portion 29 may not be formed in the second portion 25. In other words, the heel-side end 32 of the second portion 25 may be located at the frontmost position in the rotational direction Y1 of the second portion 25.

[0033] Since the first discharge groove 19 has the first portion 23 and the second portion 25, the return amount θ (θ1, θ2) can be measured at a cross section S1 of the first portion 23 perpendicular to the rotation axis O1 (e.g., the cross section shown in FIG. 7 ) and at a cross section S2 of the second portion 25 perpendicular to the rotation axis O1 (e.g., the cross section shown in FIG. 8 ), and the magnitudes of these return amounts θ1 and θ2 can be compared. The return amounts θ1 and θ2 are not limited to specific values. For example, the return amount θ1 can be set to 10° to 30°. The return amount θ2 can be set to 0° to 20°.

[0034] Although the first portion 23 is located closer to the tip 3 a than the second portion 25, the first portion 23 may also include the end of the first discharge groove 19 on the tip 3 a side. Shortly after chips are generated by the first cutting edge 13 a, the outer portion 29 of the first portion 23 tends to prevent the chips from accidentally flying out.

[0035] In the drill 1 of this embodiment, in a cross section S1 that is orthogonal to the rotation axis O1 and passes through the first portion 23, the distance between two intersections (two edges of the opening in the cross section S) where the first discharge flutes 19 and the outer peripheral surface of the body 3 intersect is defined as the opening width W1 of the first portion 23 (see FIG. 10 ). In addition, in the drill 1 of this embodiment, in a cross section S2 that is orthogonal to the rotation axis O1 and passes through the second portion 25, the distance between two intersections where the first discharge flutes 19 and the outer peripheral surface of the body 3 intersect is defined as the opening width W2 of the second portion 25 (see FIG. 11 ).

[0036] In the drill 1 of this embodiment, the opening width W1 may be smaller than the opening width W2. When the opening width W1 in the first portion 23 is relatively small, chips are less likely to accidentally fly out of the first portion 23. When the opening width W2 in the second portion 25 is relatively large, chips are more likely to be discharged to the outside at the rear end 3b side of the second portion 25.

[0037] 8 , in the cross section S2 of the drill 1 of this embodiment, the outer portion 29 of the second portion 25 of the first discharge flute 19 may include a barb portion 29a extending from the front end 27 to the barb end 31, and an inclined surface portion 29b extending from the barb end 31 to the heel-side end 32. In the cross section S2, the barb portion 29a may have a concave curved shape, and the inclined surface portion 29b may have a linear shape. In the inclined surface portion 29b, the heel-side end 32 may be located further forward in the rotational direction Y1 than the barb end 31.

[0038] 1 has a plurality of (specifically, three) flank surfaces 17, cutting edges 13, and discharge grooves 15. In this case, the cutting edge 13 located forward of the first cutting edge 13a in the rotational direction Y1 is referred to as the second cutting edge 13b, the discharge groove 15 extending from the second cutting edge 13b toward the rear end 3b is referred to as the second discharge groove 33, and the region of the outer circumferential surface of the cutting portion 7 located between the first discharge groove 19 and the second discharge groove 33 is referred to as the first outer circumferential surface 35.

[0039] Furthermore, a region of the first outer peripheral surface 35 that is located between the first portion 23 and the second discharge groove 33 is referred to as a first region 35a, and a region of the first outer peripheral surface 35 that is located between the second portion 25 and the second discharge groove 33 is referred to as a second region 35b. In other words, the first outer peripheral surface 35 has the first region 35a adjacent to the first portion 23 and the second region 35b adjacent to the second portion 25.

[0040] In this case, the first region 35a may have a protrusion 37 that protrudes rearward in the rotational direction Y1. In other words, the ridgeline of the first discharge groove 19 and the first outer peripheral surface 35 may have a portion located on the side of the tip 3a that protrudes rearward in the rotational direction Y1. The protrusion 37 may form the outer portion 29 of the first portion 23 described above.

[0041] When the outer portion 29 is configured in this manner, for example, the region excluding the outer portion 29 in the first portion 23 and the region excluding the outer portion 29 in the second portion 25 can easily be configured similarly to each other. This makes it easier for chips to flow smoothly from the first portion 23 to the second portion 25.

[0042] In the cross section S1, the length (of the curve) from the front end point to the rear end point (corresponding to the return end 31 or the heel-side end 32) of the first region 35a in the rotational direction Y1 is defined as W3 (see FIG. 10). In addition, in the cross section S2, the length (of the curve) from the front end point to the rear end point (corresponding to the heel-side end 32) of the second region 35b in the rotational direction Y1 is defined as W4 (see FIG. 11).

[0043] In the drill 1 according to the present embodiment, the length W3 may be greater than the length W4. Specifically, the length W3 of the first region 35a may be greater than the length W4 of the second region 35b by the length of the protrusion 37 that protrudes rearward in the rotational direction Y1.

[0044] Furthermore, the length L1 of the first portion 23 in the direction along the rotation axis O1 may be greater than the length L2 of the second portion 25 in the direction along the rotation axis O1, or may be less than the length L2 of the second portion 25, as in a non-limiting example shown in Figure 4. When the length L1 of the first portion 23 is less than the length L2 of the second portion 25, the degree of freedom in machining the drill 1 is increased.

[0045] The flow of chips generated by the cutting edge 13 tends to become unstable shortly after the chips are generated by the cutting edge 13. Therefore, it is not necessary to set the length L1 of the first portion 23 to be excessively large. Here, since the outer portion 29 of the second portion 25 is smaller than that of the first portion 23, it is easy to ensure a larger space in the cross section S (S1, S2) perpendicular to the rotation axis O1 in the second portion 25 than in the first portion 23. Therefore, it is possible to suppress the inadvertent ejection of chips while reducing the risk of chip clogging.

[0046] Here, a virtual circle of an arbitrary radius is assumed to be centered on the rotation axis O1 in a cross section S perpendicular to the rotation axis O1 of the drill 1. In addition, in the cross section S, a partially open space formed by being partially surrounded by the first discharge groove 19 or by being partially surrounded by the first discharge groove 19 and the surface of the shank of the insert 9 is referred to as a groove space.

[0047] When two intersections between the virtual circle and the first discharge groove 19 can be identified, the distance between the two intersections is referred to as the groove width W. The groove width W is the groove width of the groove space at a depth position corresponding to the radius of the virtual circle.

[0048] Generally, the groove space in a conventional drill may have a shape in which the groove width monotonically increases from the groove bottom (the portion close to the rotation axis) to the edge of the opening (the portion connected to the outer peripheral surface) in a cross section perpendicular to the rotation axis.

[0049] In contrast to this, in the drill 1 according to an example of the present disclosure, in the cross section S1 of the first discharge flute 19 perpendicular to the rotation axis O1, the first portion 23 may have a narrowed portion 23a in which the flute width W decreases with increasing distance from the rotation axis O1. In other words, the first portion 23 may have a narrowed portion 23a in which the opening (the flute space) becomes narrower with increasing distance from the rotation axis O1.

[0050] The narrowed portions 23a may be located on the front and rear sides in the rotational direction Y1 in the first portion 23. The narrowed portion 23a located on the front side in the rotational direction Y1 may be part of the outer portion 29. When the first portion 23 has such narrowed portions 23a, it is possible to further suppress the inadvertent ejection of chips.

[0051] While the first portion 23 has the narrowed portion 23a, the second portion 25 may not have such a narrowed portion 23a. That is, in the cross section S2, the groove width W of the second portion 25 may monotonically increase with increasing distance from the rotation axis O1. In this case, good chip discharge performance is ensured in the second portion 25, making chip clogging less likely to occur.

[0052] <Configuration Example> In the main body 3 of this embodiment, for example, the outer diameter of the cutting portion 7 is set to 6 mm to 42.5 mm. Furthermore, in the main body 3 of this embodiment, for example, 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, L is set to 1D to 12D.

[0053] Examples of the material of the main body 3 (insert 9) include cemented carbide and cermet. Examples of the cemented carbide composition 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.

[0054] 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.

[0055] 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.

[0056] When the main body 3 is constituted by the insert 9 and the holder 11, examples of the material of the holder 11 include aluminum, carbon steel, alloy steel, stainless steel, cast iron, and non-ferrous metals.

[0057] <Method for Manufacturing Machined Product> Next, a non-limiting method for manufacturing a machined product 101 on one side according to the present disclosure will be described with reference to Figures 12 to 14. 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).

[0058] (1) A step of placing the drill 1 above a prepared workpiece 103 (see FIG. 12).

[0059] (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. 12).

[0060] 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.

[0061] (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 13).

[0062] 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.

[0063] (4) Step of moving the drill 1 away from the workpiece 103 in the Y3 direction (see FIG. 14).

[0064] 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.

[0065] By going through the above steps, it is possible to obtain a machined product 101 having a highly accurate machined hole 105 .

[0066] 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 13 of the drill 1 with different locations on the workpiece 103 while holding the drill 1 in a rotating state may be repeated.

[0067] Examples of the material of the workpiece 103 include aluminum, carbon steel, alloy steel, stainless steel, cast iron, and non-ferrous metals.

[0068] Summary The drill according to aspect 1 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 first cutting edge located at the front end and a first discharge flute extending from the first cutting edge. The first discharge flute has a first portion located closer to the front end and a second portion located closer to the rear end than the first portion. In a cross section of the first discharge flute perpendicular to the rotation axis, the end of the first discharge flute located most forward in the rotation direction of the rotation axis is referred to as a front end, the portion of the first discharge flute extending from the front end to a heel-side end (the edge of a pair of edges located more forward in the rotation direction) is referred to as an outer portion, and the end of the outer portion located most rearward in the rotation direction is referred to as a barb end. When the angle formed by an imaginary line connecting the rotation axis and the front end and an imaginary line connecting the rotation axis and the barb end is defined as a barb amount, the barb amount at the first portion is greater than the barb amount at the second portion.

[0069] The drill in aspect 2 of the present disclosure is based on aspect 1, and has the following elements: in a cross section of the first portion perpendicular to the rotation axis, the distance between two intersections where the first discharge groove and the outer peripheral surface of the main body intersect is the opening width of the first portion; and in a cross section of the second portion perpendicular to the rotation axis, the distance between two intersections where the first discharge groove and the outer peripheral surface of the main body intersect is the opening width of the second portion, and the opening width of the first portion is smaller than the opening width of the second portion.

[0070] The drill in aspect 3 of the present disclosure is based on aspect 1 or 2, and the main body further has a second cutting edge located forward of the first cutting edge in the direction of rotation, a second discharge groove extending from the second cutting edge, and an outer peripheral surface located between the first discharge groove and the second discharge groove, the outer peripheral surface having a first region adjacent to the first portion and a second region adjacent to the second portion, and the first region having a convex portion protruding rearward in the direction of rotation.

[0071] The drill of aspect 4 of the present disclosure is based on aspect 3 and has an element in which the length from the front end point to the rear end point of the first region in the rotation direction in a cross section of the first portion perpendicular to the rotation axis is greater than the length from the front end point to the rear end point of the second region in the rotation direction in a cross section of the second portion perpendicular to the rotation axis.

[0072] A 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 length of the first portion in a direction along the rotation axis is smaller than the length of the second portion in a direction along the rotation axis.

[0073] A drill according to aspect 6 of the present disclosure is based on any one of aspects 1 to 5, and has an element in which the first portion has a narrowed portion in a cross section of the first portion perpendicular to the rotation axis, in which the groove width decreases with increasing distance from the rotation axis.

[0074] A drill according to a seventh aspect of the present disclosure is based on the sixth aspect, and the second portion has an element in which the flute width increases with increasing distance from the rotation axis.

[0075] A drill according to an eighth aspect of the present disclosure is based on any one of the first to seventh aspects, and has an element in which the first portion includes an end portion of the first discharge groove on the tip side.

[0076] A manufacturing method of a machined product in aspect 9 of the present disclosure includes a step of rotating a drill of any one of aspects 1 to 8 around the rotation axis, a step of contacting the rotating drill with a workpiece, and a step of moving the drill away from the workpiece.

[0077] [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.

[0078] 1... Drill 3... Body 3a... Tip 3b... Rear end 5... Gripping part 7... Cutting part 9... Insert 11... Holder 13... Cutting edge 13a... First cutting edge 13b... Second cutting edge 15... Discharge groove 17... Flank surface 19... First discharge groove 21... Chisel edge 23... First part 23a... Part 25... Second part 27... Front end 29... Outer part 31... Turned end 33... Second discharge groove 35... First outer peripheral surface 35a... First region 35b... Second region 37... Convex part 101... Cutting workpiece 103... Work material 105... Machining 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 first cutting edge located at the tip; a first discharge groove extending from the first cutting edge, The first discharge groove is a first portion located on the tip side; a second portion located closer to the rear end than the first portion, In a cross section of the first discharge groove perpendicular to the rotation axis, a front end portion of the first discharge groove located most forward in the rotation direction of the rotary shaft; a portion of the first discharge groove extending from the front end to the heel side end thereof is referred to as an outer portion; A return end portion is an end portion of the outer portion located most rearward in the rotation direction; When the angle formed by the imaginary line connecting the rotation axis and the front end and the imaginary line connecting the rotation axis and the return end is defined as the return amount, A drill in which the amount of burrs in the first portion is greater than the amount of burrs in the second portion.

2. 2. The drill according to claim 1, wherein the opening width of the first portion is defined as the distance between two intersections where the first discharge groove and the outer peripheral surface of the main body intersect in a cross section of the first portion perpendicular to the rotation axis, and the opening width of the second portion is defined as the distance between two intersections where the first discharge groove and the outer peripheral surface of the main body intersect in a cross section of the second portion perpendicular to the rotation axis, and the opening width of the first portion is smaller than the opening width of the second portion.

3. The body includes: a second cutting edge located forward of the first cutting edge in the rotation direction; a second discharge groove extending from the second cutting edge; an outer circumferential surface located between the first discharge groove and the second discharge groove, The outer circumferential surface is a first region adjacent to the first portion; a second region adjacent to the second portion, The drill according to claim 1 , wherein the first region has a convex portion that protrudes rearward in the rotational direction.

4. 4. The drill according to claim 3, wherein a length from a front end point to a rear end point of the first region in the rotation direction in a cross section of the first portion perpendicular to the rotation axis is greater than a length from a front end point to a rear end point of the second region in the rotation direction in a cross section of the second portion perpendicular to the rotation axis.

5. The drill according to claim 1 , wherein a length of the first portion in a direction along the rotation axis is smaller than a length of the second portion in a direction along the rotation axis.

6. The drill according to claim 1 , wherein the first portion has a narrowed portion in which a flute width decreases with increasing distance from the rotation axis in a cross section of the first portion perpendicular to the rotation axis.

7. The drill according to claim 6 , wherein the second portion has a flute width that increases with increasing distance from the rotation axis.

8. The drill according to claim 1 , wherein the first portion includes an end portion of the first discharge flute on the tip side.

9. A step of rotating the drill according to any one of claims 1 to 8 around the rotation axis; bringing the rotating drill into contact with a workpiece; and a step of separating the drill from the workpiece.