Cutting insert, drill bit and method of producing a machined product using the same

Abstract

A cutting insert (1) comprising: a first surface (3) which has a first side (3b1), a first corner (3a1) and a second corner (3a2) adjacent to the first side (3b1), and a breaker part (13) which is arranged along the first side (3b1), a second surface (5) which is arranged on a side opposite to the first surface (3), and a third surface (7) which is arranged between the first surface (3) and the second surface (5) along the first side (3b1), wherein the crusher part (13) has a first section (13A), a second section (13B) and a third section (13C), which are arranged sequentially starting from the first side (3b1), the first section (13A) is an inclined surface which is inclined to approach the second surface (5) as it moves away from the first side (3b1), the third section (13C) is an inclined surface which is inclined to separate itself from the second surface (5) as it moves away from the second section (13B), a whole of the second section (13B) is arranged closer to the second surface (5) than the first side (3b1), at least one section of the third section (13A) is located further away from the second surface (5) than the first side (3b1), and in a front view of the first surface (3) at a distance starting from the first side (3b1) to a topmost section of the third section (13C) on an orthogonal line with reference to the first side (3b1) a maximum value at a side of the second corner (3a2) is greater than a maximum value at a side of the first corner (3a1), wherein the crusher part (13) has a first, upper surface (13D) which is arranged further inwards on the first surface (3) on one side of the first corner (3a1) than the third section (13C), and a second, upper surface (13E) which is arranged further inwards on the first surface (3) on one side of the second corner (3a2) than the third section (13C), the first, upper surface (13D) is inclined to approach the second surface (5) as it moves from one side of the first corner (3a1) towards one side of the second corner (3a2), and the second, upper surface (13E) is inclined to approach the second surface (5) as it moves away from the first side (3b1).

Description

Technical area

[0001] The present embodiments relate to a cutting insert, a drill bit, and a method of manufacturing a machined product intended for use in a cutting operation. background

[0002] As a cutting insert, a drill for use in a drilling operation is commonly known (see, for example, WO 2014 / 046260 A1 (Patent Document 1)). The drill described in Patent Document 1 includes a base member (holder) having an axial line and two inserts (an inner cutting edge insert and an outer cutting edge insert) fixed to the base member.

[0003] The inner cutting edge insert and the outer cutting edge insert in the tool described in Patent Document 1 have different distances from the axial line of the tool. Therefore, chips generated by the inner cutting edge insert and chips generated by the outer cutting edge insert have different shapes. In each of the outer cutting edge insert and the inner cutting edge insert, chips generated on an inner peripheral side and chips generated on an outer peripheral side also have different shapes. In this regard, there is a need for chip discharge according to the shape.

[0004] For example, the chips generated by the outer cutting edge insert can cause clogging if the chips extend excessively without being divided into a suitable length. In particular, chips generated by machining mild steel or the like are soft and have a tendency to chip clogging.

[0005] Furthermore, from US 2011 / 0 044 776 A1 a cutting insert with a first, a second and a third surface is known, wherein a crusher part is arranged on the first surface.

[0006] In addition, a corresponding cutting insert is known from US 2016 / 0 193 668 A1.

[0007] It is an object of the present invention to provide a cutting insert whose chip discharge performance is good even when machining a workpiece such as structural steel in which soft chips are generated. Brief explanation

[0008] The object is achieved by a cutting insert having the features according to claim 1. The object is further achieved by a drill having the features according to claim 12. The object is further achieved by a method having the features according to claim 13. Further embodiments of the cutting insert are described in the associated dependent claims. Short description of the drawings Fig. 1 is a perspective view showing a cutting insert in one of the embodiments, Fig. 2 is a front view when a surface in the cutting insert, which is in the Fig. 1 is shown, viewed from the front, Fig. 3 is a front view when a third surface in the cutting insert, which is in the Fig. 1 is shown, viewed from the front, Fig. 4 is a partially enlarged view of the Fig. 2, Fig. 5 is a sectional view along the line AA in the cutting insert, which is shown in the Fig. 4 is shown, Fig. 6 is a sectional view along the line BB in the cutting insert, which is shown in the Fig. 4 is shown, Fig. 7 is a sectional view along the line CC in the cutting insert, which is shown in the Fig. 4 is shown, Fig. 8 is a sectional view along the line DD in the cutting insert, which is shown in the Fig. 4 is shown, Fig. 9 is a perspective view showing a drill in one of the embodiments, Fig. 10 is a side view when the drill bit, which is in the Fig. 9 is viewed from a B1 direction, Fig. 11 is a side view when the drill bit, which is in the Fig. 9 is viewed from a B2 direction, Fig. 12 is a diagram showing one of the steps in the method of manufacturing a machined product in one of the embodiments, Fig. 13 is a diagram showing one of the steps in the method of manufacturing a machined product in one of the embodiments, and Fig. 14 is a diagram showing one of the steps in a method of manufacturing a machined product in one of the embodiments. Embodiments

[0009] A cutting insert 1 (hereinafter also referred to as the "insert 1") and a drill 101 incorporating the insert 1 in one of the embodiments of the present disclosure are described in detail below with reference to the drawings. To facilitate description, the drawings referenced below show, in a simplified form, only major elements necessary to describe the embodiments. Therefore, the inserts and drills in the present disclosure may include any components not shown in the reference drawings.

[0010] Dimensions of the elements in any of the drawings are not those that faithfully represent the dimensions of actual structural elements and dimensional relationships of those elements. These facts also apply to a method of manufacturing a machined product, which is described later. Cutting inserts

[0011] The inserts 1 in embodiments will first be described with reference to the drawings. The insert 1 in one of the embodiments is suitably usable as an external cutting edge insert in a drill of the replaceable insert type. The insert 1 may, for example, have a first surface 3, a second surface 5, a third surface 7, a cutting edge 9, and a through hole 11, as shown in the Fig. 1 is shown.

[0012] For the purpose of easy visual understanding, the first surface 3, the second surface 5, and the third surface 7 are replaced by the upper surface 3, the lower surface 5, and the side surface 7, respectively. The upper surface 3 does not need to be arranged in one state the entire time when the insert 1 is attached to the drill or used in a cutting operation. The lower surface 5 does not need to be arranged in one state the entire time when the insert 1 is attached to the drill or used in a cutting operation.

[0013] For example, cemented carbide or cermet can be used as a material of the insert 1. Examples of cemented carbide compositions include WC-Co, WC-TiC-Co, and WC-TiC-TaC-Co. WC-Co is produced by adding cobalt powder (Co powder) to tungsten carbide (WC), followed by sintering. WC-TiC-Co is produced by adding titanium carbide (TiC) to WC-Co. WC-TiC-TaC-Co is produced by adding tantalum carbide (TaC) to WC-TiC-Co.

[0014] Cermet is a sintered composite material obtained by combining metal and a ceramic component. Examples of cermets include those composed primarily of a titanium compound, such as titanium carbide (TiC) or titanium nitride (TiN).

[0015] A surface of the insert 1 may be coated with a coating layer using a chemical vapor deposition (CVD) or a physical vapor deposition (PVD) method. Examples of the composition of the coating layer include titanium carbide (TiC), titanium nitride (TiN), titanium carbon nitride (TiCN), and aluminum oxide (Al2O3).

[0016] At least a portion of the upper surface 3 can serve as a rake surface. The upper surface 3 in the illustrated embodiment has a polygonal shape and includes a corner 3a and a side 3b. Specifically, the upper surface 3 has an approximately quadrilateral shape. Therefore, in the illustrated embodiment, the upper surface 3 has four corners 3a and four sides 3b. In one case, two of the four corners 3a that are adjacent to each other are referred to as a first corner 3a1 and a second corner 3a2, respectively, and a first side 3b1 is located between the first corner 3a1 and the second corner 3a2. In other words, in the illustrated embodiment, the upper surface 3 has the first side 3b1, with the first corner 3a1 and the second corner 3a2 being adjacent to the first side 3b1.

[0017] The term "polygonal shape" does not mean a precise polygonal shape. For example, each of the four corners 3a of the upper surface 3 does not have to be manufactured as a precise corner, but can have a rounded shape in a plan view. Each of the four sides does not have to be manufactured in a precise, rectilinear shape. The term "top view" refers to a state in which the insert 1 is viewed toward the upper surface 3 and, in other words, can be a front view of the first surface 3.

[0018] The lower surface 5 is a surface which is arranged on an opposite side to the upper surface 3 and can serve as a seating surface when the insert 1 is attached to the holder. Like the upper surface 3, the lower surface 5 has a polygonal shape, or alternatively can be a flat surface which is slightly smaller than the upper surface 3. An outer peripheral edge of the lower surface 5 is not visible in the front view due to the upper surface 3, which in the Fig. 2 is shown.

[0019] The shapes of the upper surface 3 and the lower surface 5 are not limited to the above embodiment. Although the upper surface 3 and the lower surface 5 have an approximate quadrilateral shape in the insert 1 of the illustrated embodiment, the shapes of the upper surface 3 and the lower surface 5 can be, for example, a triangular shape, a pentagonal shape, a hexagonal shape, or an octagonal shape. Although the upper surface 3 has an approximate square shape in the illustrated embodiment, the quadrilateral shape is not limited to this shape, but can be, for example, a rhombus shape or a rectangle.

[0020] The insert 1 may have a through-hole 11. In the illustrated embodiment, the through-hole 11 is open in the upper surface 3 and the lower surface 5. The through-hole 11 is usable when fixing the insert 1 to the drill bit holder. For example, the insert 1 is fixed to the drill bit holder by inserting a screw into the through-hole 11.

[0021] The lower surface 5 in the illustrated embodiment is a flat surface, and an extending direction of a central axis X1 of the through-hole 11, in other words, a penetration direction of the through-hole 11, is orthogonal to the lower surface 5. The central axis X1 of the through-hole 11 coincides with a central axis of the insert 1 in the illustrated embodiment. Therefore, in other words, the central axis X1 of the through-hole 11 can be the central axis of the insert 1. Specifically, the central axis of the insert 1 is an axis extending between the upper surface 3 and the lower surface 5 and serving as a rotation axis during rotation of the insert 1 in a plan view.

[0022] The upper surface 3 may be rotationally symmetrical about the central axis X1. The upper surface 3 in the embodiment shown in the Fig. 2, has four corners 3a and four sides 3b arranged to have a 90° rotational symmetry around the central axis X1. Although not specifically shown, the bottom surface 5 has a 90° rotational symmetry around the central axis X1 in a bottom view. The term "bottom view" refers to a state in which the insert 1 is viewed in a direction toward the bottom surface 5.

[0023] The side surface 7 is arranged between the upper surface 3 and the lower surface 5 and along the first side 3b1. The side surface 7 can connect the upper surface 3 and the lower surface 5. At least a part of the side surface 7 can serve as a flank or flank surface. In cases where the lower surface 5 has a slightly smaller shape than the upper surface 3, the side surface 7 can be inclined to approach the central axis X1 as it moves from one side of the upper surface 3 towards one side of the lower surface 5, as shown in the Fig. 3 is shown.

[0024] A maximum width of the upper surface 3 in a plan view can be, for example, 3 to 25 mm. A height from the lower surface 5 to the upper surface can be, for example, 1 to 10 mm. The term "height from the lower surface 5 to the upper surface 3" refers, in a side view, to a length in a direction parallel to the central axis X1 between an upper end (the highest portion) of the upper surface 3 and a lower end (the lowest portion) of the lower surface 5. The "side view" refers to a viewing of the insert 1 in a direction toward the side surface 7 and from a direction orthogonal to the central axis X1 of the through-hole 11.

[0025] The configurations of the upper surface 3, the lower surface 5, and the side surface 7 are not limited to the above embodiment. For example, the lower surface 5 may have the same shape as the upper surface 3, and an outer edge of the lower surface 5 may overlap with an outer edge of the upper surface 3 in a planar perspective. In this case, the side surface 7 may be orthogonal to the lower surface 5.

[0026] The cutting edge 9 can be arranged at least along a portion of a ridge line where the upper surface 3 intersects the side surface 7. The cutting edge 9 is arranged along at least a portion of the first side 3b1 in the illustrated embodiment. The cutting edge 9 can be used for cutting a workpiece in a cutting operation.

[0027] The cutting edge 9 can be arranged on each of the four sides 3b, as shown in the Fig. 2 and Fig. 3. Alternatively, the cutting edge 9 may be arranged over the entirety of the first side 3b1. Further alternatively, the cutting edge 9 may also be arranged at the corner 3a in addition to the side 3b.

[0028] In cases where the cutting operation is performed using the cutting edge 9 located on the first side 3b1 as a cutting edge for an outer cutting edge insert, the insert 1 may be mounted on the holder so that one side of the first corner 3a1 of the cutting edge is closer to the rotation axis of the drill than one side of the second corner 3a2. The cutting edge 9 is located on the first side 3b1 in a region of the upper surface 3 extending along the first side 3b1, as described below.

[0029] As it is in the Fig. 4 to 8, the upper surface 3 may include a crusher part 13 arranged along the first side 3b1. The crusher part 13 may have the function of winding the chips during the cutting process. The crusher part 13 may include a first section 13A, a second section 13B, and a third section 13C arranged sequentially starting from the first side 3b1. The first section 13A in the crusher part 13 is arranged closest to the first side 3b1, and the third section 13C in the crusher part 13 is arranged farthest from the first side 3b1 in the illustrated embodiment. The second section 13B is arranged between the first section 13A and the third section 13C.

[0030] As it is in the Fig. 5 to 8, the first portion 13A is an inclined surface inclined to approach the lower surface 5 as it moves away from the first side 3b1. The third portion 13C is an inclined surface inclined to separate from the lower surface 5 as it moves away from the second portion 13B. That is, the first portion 13A is a downwardly inclined surface inclined downward as it moves toward the inside of the upper surface 3. The third portion 13C is an upwardly inclined surface inclined upward as it moves toward the inside of the upper surface 3. The term "inside" refers to one side of the through-hole 11 (one side of the central axis X1). The term "upward" refers to a direction from one side of the lower surface 5 toward one side of the upper surface 3 in a direction along the central axis X1.The term “downward” means a direction starting from the side of the upper surface 3 towards the side of the lower surface 5 in the direction along the central axis X1.

[0031] The entirety of the second section 13B is in the embodiment shown in the Fig. 3, is arranged closer to the lower surface 5 than the first side 3b1. At least a part of the third section 13C is in the embodiment shown in the Fig. 3, is arranged further away from the lower surface 5 than the first side 3b1. When a maximum distance of an individual component from the lower surface 5 in a direction along the central axis X1 is regarded as a height of the individual component, a height H13 of the third portion 13C is greater than a height H3b of the first side 3b1 in the embodiment shown in the Fig. 3. In cases where the lower surface 5 does not have a flat surface shape, a distance from a virtual plane (reference plane S) orthogonal to the central axis X1 of the through hole 11 can be determined as the height described above.

[0032] As it is in the Fig. 2 and Fig. 4 in a plan view of the insert 1, in a distance from the first side 3b1 to an uppermost portion 16 of the third portion 13C on an orthogonal line with respect to the first side 3b1, a maximum value L2 of a distance at a side of the second corner 3a2 (hereinafter simply referred to as the distance L2) may be greater than a maximum value L1 of a distance at a side of the first corner 3a1 (hereinafter also simply referred to as the distance L1). That is, the distance from the first side 3b1 to the third portion 13C may be greater at the side of the second corner 3a2 than at a side of the first corner 3a1.

[0033] As it is in the Fig. 2 and Fig. 4 is shown in a plan view, the distance L1 and the distance L2 can be regarded as a distance from the first side 3b1 to an uppermost portion 16 of the third portion 13C in the direction orthogonal to the first side 3b1. As described above, since the third portion 13C is the inclined surface that slopes upward as it moves away from the first side 3b1, in other words, the uppermost portion 16 of the third portion 13C can be an inner peripheral edge of the third portion 13C.

[0034] The expression that “the distance L2 is greater than the distance L1” means that a distance in the third portion 13C located closest to the second corner 3a2 side is greater than the distance at the third portion 13C located closest to a first corner 3a1 side when the distance is determined from the first side 3b1 to the uppermost portion 16 of the third portion 13C in the direction orthogonal to the first side 3b1 and along the first side 3b1.

[0035] In one case, the distance from the first side 3b1 to the uppermost portion 16 of the third portion 13C is determined in the direction orthogonal to the first side 3b1 along the first side 3b1 and in a direction from the first corner 3a1 side to the second corner 3a2 side, and the third portion 13C may include a range in which the above distance is constant.

[0036] Therefore, the breaker part 13, which includes the third portion 13C in which the distance L1 and the distance L2 have the above relationship and at least a part of which is located above the first side 3b1, is arranged along the first side 3b1 of the present disclosure. Chips that tend to extend upward are therefore easily contacted with the third portion 13C located above the first side 3b1, and the chips that contact the third portion 13C at a front side in an advancing direction are thus bent by pressing against the second portion 13B of the breaker part 13.

[0037] In addition to the above, the distance L2 on the side of the second corner 3a2 located on an outer edge side of the drill is greater than the distance L1 on the side of the first corner 3a1 located on an inner edge side of the drill. Consequently, the effect of pressing the chips against the second portion 13B of the breaker part 13 becomes relatively strong on the inner edge side. A relatively large space in the advancing direction of the chips can be ensured on the outer edge side.

[0038] Wrinkling occurs on a chip due to the pressure action, and the chip tends to have a locally large thickness portion on the inner edge side. This portion therefore tends to break, and the chip tends to be divided. For a chip whose generation speed is relatively high, it is less likely to be caught on the breaker part 13 on the outer edge side. Therefore, even if a soft chip that tends to extend upward is generated, the chip is easily controllable by the breaker part 13, resulting in an improvement in chip discharge performance.

[0039] In particular, during a cutting operation using a machining center, the generated chips tend to be drawn toward the outer edge side of the drill by centrifugal force. When a relationship between distance L1 and distance L2, namely distance L1 < distance L2, is satisfied, the chip on the outer edge side, which tends to be drawn by centrifugal force, can be brought into contact with the third portion 13C more stably and easily. Even during the cutting operation using the machining center, the chip can be stably wound by the breaker part 13, resulting in smooth chip discharge.

[0040] For example, the distance L2 must be 130% or more of the distance L1. In this case, chips generated on the inner edge side of the drill (the first corner 3a1 side) and the outer edge side (the second corner 3a2 side) of the drill, which have different generation speeds due to different cutting speeds, are less likely to come into strong contact with the breaker part 13 and be trapped on the outer edge side.

[0041] For example, the distance L2 can be 150% or less of the distance L1. In this case, even in the cutting process using a machining center, during which chips tend to be pulled outward by centrifugal force, chip clogging is less likely to occur. For example, the distance L1 should be 0.5 to 2 mm. The distance L2 should be 0.8 to 3 mm.

[0042] As it is in the Fig. 4, the breaker part 13 may be gradually changed in a distance from the first side 3b1 to the uppermost portion 16 at the third portion 13C. That is, when the breaker part 13 is viewed along the first side 3b1, a certain area X2 having the distance L1 may be located on a side of the first corner 3a1, and a certain area X3 having the distance L2 may be located on a side of the second corner 3a2 in the third portion 13C.

[0043] In cases where the distance from the first side 3b1 to the uppermost section 16 is gradually changed at the third section 13C, it is easy to ensure large areas each having the distance L1 and the distance L2 in a direction along the first side 3b1, even if the insert 1 has a small size. Regardless of the size of the insert 1, a suitable winding action can be obtained by the crusher part 13, resulting in stable chip discharge.

[0044] In cases where the third section 13C includes the specific region X2 and the specific region X3, a dimension in a direction along the first side 3b1 of the specific region X2, which has the relatively small distance L1, can be set to, for example, 0.2d to 0.4d, where d is a length of the first side 3b1. In these cases, due to an excessively large number of regions arranged near the first side 3b1 in the third section 13C, a crushing effect becomes large and therefore the chips are less likely to burn. As shown in the Fig. 3, the length d of the first side 3b1 can be set to 0.6 to 0.85 times the length of the side 3b, and it can be set to 5 to 30 mm, for example. As shown in the Fig. 4, the above-mentioned dimension in the specific range X2 can be set to, for example, 1 to 12 mm, and the above-mentioned dimension in the specific range X3 can be set to, for example, 1 to 6 mm.

[0045] The distance from the cutting edge 9 to the uppermost section 16 at the third section 13C in the crusher part 13 is not limited to a gradually changing structure. For example, the distance from the cutting edge 9 to the uppermost section 16 at the third section 13C in the crusher part 13 may gradually increase from the first corner 3a1 toward the second corner 3a2.

[0046] An inclination angle Θ1 of the first portion 13A may be constant along the first side 3b1, as shown in the Fig. 5 to 8. With this configuration, the cutting resistance acting on the cutting edge 9 during cutting can be maintained in a well-balanced manner within a range from the inner edge side to the outer edge side of the drill. Therefore, the chip winding action by the breaker part 13 is less likely to deteriorate due to an unbalanced cutting resistance acting on the cutting edge 9 during cutting. This results in an effective chip winding action by the breaker part 13.

[0047] The inclination angle Θ1 of the first section 13A is a so-called rake angle of the first section 13A. Accordingly, the inclination angle Θ1 of the first section 13A can be regarded as, for example, an inclination angle of the first section 13A relative to an arbitrary reference plane orthogonal to the central axis X1 in the cross-section orthogonal to the first side 3b1. The inclination angle Θ1 of the first section 13A in an arbitrary cross-section orthogonal to the first side 3b1 can be constant, as shown in the Fig. 5 to 8. The term "constant" means that it must be essentially constant and can have an error of, for example, ±1°. The inclination angle Θ1 of the first section 13A can be set, for example, to 15 to 20°.

[0048] In cases where the first portion 13A has a curved surface shape, an inclination angle of the first portion 13A at the outer peripheral edge of the first portion 13A must be the inclination angle Θ1 of the first portion 13A in the cross section orthogonal to the first side 3b1.

[0049] An inclination angle Θ32 of the third portion 13C at a side of the second corner 3a2 may be smaller than an inclination angle Θ31 of the third portion 13C at a side of the first corner 3a1, as shown in the Fig. 5 and Fig. 8. With this configuration, the impact generated by contact between the third portion 13C and chips on the outer edge side, where the generation speed is relatively high, is less likely to increase excessively. This contributes to improving the effect of adequately winding the chips by the crusher part 13.

[0050] The inclination angles Θ31 and Θ32 of the third section 13C can be calculated in the same way as the inclination angle Θ1 of the first section 13A. In particular, each of the inclination angles Θ31 and Θ32 of the third section 13C can be considered, for example, as an inclination angle of the third section 13C to the arbitrary reference plane orthogonal to the central axis X1 in the cross-section orthogonal to the first side 3b1.

[0051] In other words, as in the Fig. As shown in FIG. 5, an inclination angle of the third portion 13C relative to the reference plane S in the cross section passing through the third portion 13C located on one side of the first corner 3a1 and orthogonal to the first side 3b1 can be regarded as the inclination angle Θ31. This also applies to the inclination angle Θ32 of the third portion 13C. In the third portion 13C, the inclination angle Θ31 can be, for example, 25 to 30°, and the inclination angle Θ32 can be, for example, 23 to 28°.

[0052] The expression that "the inclination angle Θ32 is smaller than the inclination angle Θ31" means that when the inclination angle of the third portion 13C is determined along the first side 3b1, an inclination angle at the third portion 13C located closest to the second corner 3a2 is smaller than an inclination angle at the third portion 13C located closest to the first corner 3a1. Therefore, when the inclination angle of the third portion 13C is determined along the first side 3b1 and in a direction from a side of the first corner 3a1 toward the side of the second corner 3a2, a region where the above-mentioned inclination angle becomes constant may exist at the third portion 13C.

[0053] As it is in the Fig. 3, a maximum value L4 of a distance from the bottom surface 5 to the third portion 13 on the second corner 3a2 side (hereinafter also simply referred to as "distance L4") may be greater than a maximum value L3 of a distance from the bottom surface 5 to the third portion 13C on a first corner 3a1 side (hereinafter also simply referred to as "distance L3"). In other words, a height of the third portion 13C on a second corner 3a2 side may be greater than that on a first corner 3a1 side.

[0054] When the distance L3 and the distance L4 have the above relationship, chips are more easily contacted by the third portion 13C of the breaker part 13 due to a relatively high generation speed on the side of the second corner 3a2 located on the outer edge side of the drill, where the chips are more likely to pass over and past the bit 1. This makes it easier to control the chips on the outer edge side, resulting in an improvement in chip discharge performance.

[0055] As it is in the Fig. 3, in a side view, the distance L3 and the distance L4 can be regarded as a distance from the bottom surface 5 to the top portion 16 of the third portion 13C in a direction along the central axis X1. The expression that "the distance L4 is greater than the distance L3" can be determined in the same way as the expression that "the distance L2 is greater than the distance L1." In other words, the expression that "the distance L4 is greater than the distance L3" means that when the distance from the bottom surface 5 to the top portion 16 of the third portion 13C is determined in the direction along the central axis X1 as along the first side 3b1, a distance at the third portion 13C located closest to the second corner 3a2 is greater than a distance at the third portion 13C located closest to the first corner 3a1.Therefore, when the distance from the lower surface 5 to the uppermost portion 16 of the third portion 13C is determined in the direction along the central axis X1 along the first side 3b1 and in a direction from the first corner 3a1 toward the second corner 3a2, there may be a region at the third portion 13C where the above-mentioned distance becomes constant.

[0056] Determining the dimensional relationship between distance L3 and a distance L4 can be carried out using a distance of the uppermost section 16 of the third section 13C based on the reference plane S orthogonal to the central axis X1 as a distance from the lower surface 5 to the uppermost section 16 of the third section 13C, as shown in the Fig. 5 and Fig. 8. In particular, a dimension of a distance from the reference plane S to the uppermost portion 16 of the third portion 13C can be determined at one side of the first corner 3a1 and at one side of the second corner 3a2.

[0057] As the distance from the lower surface 5 to the uppermost portion 16 of the third portion 13C, the distance L3 may be, for example, 0.95 to 10.4 mm and the distance L4 may be, for example, 1 to 10.5 mm.

[0058] The breaker part 13 may have a first upper surface 13D located on one side of the first corner 3a1 and a second upper surface 13E located on one side of the second corner 3a2. The first upper surface 13D in the illustrated embodiment is located further on an inner side of the upper surface 3 on one side of the first corner 3a1 than the third section 13C. The second upper surface 13E in the illustrated embodiment is located further on an inner side of the upper surface 3 on one side of the second corner 3a2 than the third section 13C.

[0059] The uppermost portion 16 of the third portion 13C on the first corner 3a1 side may be located at a boundary between the third portion 13C and the first upper surface 13D. The uppermost portion 16 of the third portion 13C on the second corner 3a2 side may be located at a boundary between the third portion 13C and the second upper surface 13E.

[0060] The first upper surface 13D may be inclined to approach the lower surface 5 as it moves from one side of the first corner 3a1 toward the side of the second corner 3a2. In cases where the upper surface 13D has the above configuration, if chips overflow the third portion 13C, the chips are less likely to flow toward the second corner 3a2 than toward the first corner 3a1. In cases where the second corner 3a2 is located farther from the rotation axis of the drill than the first corner 3a1, the chips tend to flow toward the outer edge side of the drill, resulting in excellent chip discharge performance.

[0061] The upper surface 13E may be inclined to approach the lower surface 5 as it moves away from the first side 3b1. In cases where the second surface has the above configuration, if chips overflow the third portion 13C, the chips are less likely to contact the second upper surface 13E. In cases where the second corner 3a2 is located farther from the rotation axis of the drill than the first corner 3a1, chips tend to flow toward the outer edge side of the drill, resulting in excellent chip discharge performance.

[0062] The crusher part 13 may have a bottom part 15 arranged on one side of the lower surface 5. In particular, the bottom part 15 corresponds to a part of the crusher part 13 arranged on a side closest (lowest) to the lower surface 5 in a cross-section orthogonal to the first side 3b1. In other words, the bottom part 15 corresponds to a lowermost portion of the crusher part 13 in the above cross-section. The bottom part 15 may extend along the first side 3b1.

[0063] In a plan view of the insert 1, as in the embodiment shown in the Fig. 2, with respect to a distance from the first side 3b1 to the bottom part 15 of the crusher part 13 in an orthogonal line with respect to the first side 3b1, a maximum value L6 of a distance at a side of the second corner 3a2 (hereinafter also simply referred to as “distance L6”) may be larger than a distance at a side of the first corner 3a1 (hereinafter also simply referred to as “distance L5”).

[0064] When the distance L6 is greater than the distance L5, chips generated on the outer edge side of the drill, where the chip generation speed is relatively high and a thread diameter is relatively large, are relatively slower than chips generated on the inner edge side and are pressed against the bottom part 15 of the breaker part 13. Chips with the relatively large thread diameter are less likely to be trapped in the breaker part 13.

[0065] In particular, in a top view, as shown in the Fig. 2, the distance L5 is a dimension from the first side 3b1 on a side of the first corner 3a1 to the bottom part 15 in a direction orthogonal to the first side 3b1. Similarly, the distance L6 in a plan view is a dimension from the first side 3b1 on a side of the second corner 3a2 to the bottom part 15 in a direction orthogonal to the first side 3b1. The expression that "the distance L6 is greater than the distance L5" can be determined in the same way as the above expression that "the distance L2 is greater than the distance L1."

[0066] The second portion 13B may have a circular arc-curved surface shape, as described later. In this case, the lowest portion of the bottom part 15 may be defined as a single point. However, if a bottom of the second portion 13B is a flat surface, the lowest portion of the bottom part 15 may be defined as an area with a width. In this case, in a plan view, the distance L5 and the distance L6 may be a minimum value of a dimension from the first side 3b1 to the bottom of the second portion 13B in a direction orthogonal to the first side 3b1.

[0067] For example, the distance L5 must be between 0.2 and 1.5 millimeters. The distance L6, for example, must be between 0.3 and 1.8 mm.

[0068] The distance from the first side 3b1 to the base part 15 can be changed step by step in the crusher part 13. A position of the base part 15 is in the Fig. 4 is indicated by a dashed line. Therefore, in a view along the first side 3b1, the distance from the first side 3b1 to the bottom part 15 is the distance L5 in the specific area X2, and the distance from the first side 3b1 to the bottom part 15 is the distance L6 in the specific area X3.

[0069] In cases where the distance from the first side 3b1 to the bottom part 15 is gradually changed as described above, a region having a relatively short distance can be arranged at a certain width in the direction along the first side 3b1. Therefore, it is easy to ensure stable contact between the crusher part 13 and the chips on the inner edge side. This leads to a stable chip winding action on the inner edge side.

[0070] The distance from the first side 3b1 to the bottom part 15 in a region located between the specific region X2 and the specific region X3 may increase as it moves away from the specific region X2.

[0071] As it is in the Fig. 5 and Fig. 8, a maximum value L8 of a distance from the lower surface 5 to the bottom part 15 on the second corner 3a2 side (hereinafter also simply referred to as “distance L8”) may be smaller than a maximum value L7 of a distance from the lower surface 5 to the bottom part 15 on a first corner 3a1 side (hereinafter also simply referred to as “distance L7”).

[0072] In particular, a height of the base part 15 may be smaller on a side of the second corner 3a2 than on a side of the first corner 3a1. In particular, a depth of the base part 15 may be greater on the side of the second corner 3a2 than on a side of the first corner 3a1.

[0073] When the bottom part 15 has the above configuration, chips generated on the outer edge side of the drill, where the chip generation speed is high and a thread diameter tends to become large, easily contact the bottom part 15 of the breaker part 13 at a relatively slow speed than chips generated on the inner edge side. Chips with a large thread diameter are less likely to be trapped on the breaker part 13.

[0074] The distance L7 is a dimension from the bottom surface 5 to the bottom part 15 on one side of the first corner 3a1 in a direction along the central axis X1. Similarly, the distance L8 is a dimension from the bottom surface 5 to the bottom part 15 on the side of the second corner 3a2 in the direction along the central axis X1.

[0075] Like the distance L3 and the distance L4, the distance L7 and the distance L8 can be determined using a distance to the bottom part 15 based on the reference plane S orthogonal to the central axis X1 as the distance from the lower surface 5 to the bottom part 15, as shown in the Fig. 5 and Fig. 8. Specifically, a dimension can be determined as a distance from a reference plane S to the bottom part 15 on the first corner 3a1 side and a second corner 3a2 side. The expression that "the distance L8 is smaller than the distance L7" can be determined in the same way as the above expression that "the distance L2 is greater than the distance L1."

[0076] As the distance from the lower surface 5 to the bottom part 15, the distance L7 must be, for example, 0.9 to 9.5 millimeters and the distance L8 must be, for example, 0.8 to 9 mm.

[0077] The distance from the bottom surface 5 to the bottom part 15 at the second section 13B of the crusher part 13 can be changed stepwise. Specifically, in a view along the first side 3b1, the distance from the bottom surface 5 to the bottom part 15 can be the distance L7 in the specific area X2, and the distance from the bottom surface 5 to the bottom part 15 can be the distance L8 in the specific area X3. In cases where the distance from the bottom surface 5 to the bottom part 15 is changed stepwise as described above, a region having a relatively short distance (that is, a region where the bottom part 15 has a large depth) can be located at a specific width in the direction along the first side 3b1. Therefore, the chips generated on the outer edge side and having a large winding diameter are less likely to get stuck.The distance from the lower surface 5 to the bottom part 15 in the area located between the specific area X2 and the specific area X3 may increase as it moves away from the specific area X2.

[0078] The second portion 13B may have a circular arc shape projecting toward the lower surface 5 in a cross-section orthogonal to the first side 3b1, as shown in the Fig. 5 to 8. A shape of a chip after passing the breaker part 13 becomes one obtained by transferring a shape of the second portion 13B. In cases where the second portion 13B has the above shape, chips tend to be drawn toward the breaker part 13, thereby making it possible to decrease a winding diameter of the chips.

[0079] In particular, a radius of curvature R2 of the second portion 13B in the cross section orthogonal to the first side 3b1 at a side of the second corner 3a2 may be larger than a radius of curvature R1 of the second portion 13B in the cross section orthogonal to the first side 3b1 at a side of the first corner 3a1, as shown in the Fig. 5 and Fig. 8. With this configuration, a portion of a flowing chip having a shape transmitted from the second portion 13B of the breaker part 13 located on the outer edge side of the drill and having a large thread diameter can be brought into smooth contact with a breaker surface having a relatively large radius of curvature. Therefore, the chip on the outer edge side is less likely to get stuck.

[0080] For example, the radius of curvature R1 and the radius of curvature R2 of the second portion 13B can be calculated using contact points of three arbitrary points or more on a line segment of the second portion 13B in the cross section orthogonal to the first side 3b1, as shown in the Fig. 5 and Fig. 8. The radius of curvature R1 can be set, for example, to 0.4 to 1 mm. The radius of curvature R2 can be set, for example, to 0.7 to 1.5 mm.

[0081] The crusher part 13 may include a first region 17, a second region 18, and a third region 19, which are arranged sequentially from one side of the first corner 3a1 to one side of the second corner 3a2. In this case, these regions may satisfy the following relationship.

[0082] A radius of curvature r1 of the second section 13B in the first region 17 is in the Fig. 5 embodiment shown constant. A radius of curvature r3 of the second section 13B in the third region 19 is in the Fig. 8 and is greater than the radius of curvature r1 of the second section 13B in the first region 17. In the embodiments shown in the Fig. 6 and Fig. 7, a radius of curvature r2 of the second portion 13B increases in a cross section orthogonal to the first side 3b1 in the second region 18 as it moves from a side of the first region 17 toward a side of the third region 19.

[0083] A corner portion can be formed at the third portion 13C in a boundary portion between the first region 17 and the second region 18, and at the third portion 13C in an end portion of the third region 19 located on one side of the second corner 3a2. These corner portions can serve as a guide to reduce the likelihood of generated chips flowing in an outer peripheral direction of the drill due to centrifugal force. Therefore, a chip discharge direction can be stable to improve chip discharge performance.

[0084] The radius of curvature R1 (a radius of curvature on one side of the first corner 3a1) can have the same value as the radius of curvature r1. The radius of curvature R2 (a radius of curvature on the side of the second corner 3a2) can have the same value as the radius of curvature r3.

[0085] The first region 17 may coincide with the specific region X2. Specifically, the radius of curvature of the second portion 13B (the radius of curvature R1, the radius of curvature r1) may be constant, and a distance (distance L1) from the first side 3b1 to the uppermost portion 16 of the third portion 13C in the first region 17 may be constant.

[0086] Similarly, the third region 19 may coincide with the specific region X3. Specifically, the radius of curvature of the second portion 13B (the radius of curvature R2, the radius of curvature r3) may be constant, and a distance (distance L2) from the first side 3b1 to the uppermost portion 16 of the third portion 13C in the third region 19 may be constant.

[0087] The first section 13A and the third section 13C may have a flat, inclined surface, as shown in the Fig. 5 to 8. In particular, the first portion 13A may be a flat, downwardly inclined surface and the third portion 13C may be a flat, upwardly inclined surface.

[0088] In cases where the third portion 13C is the flat, upwardly inclined surface, even when a change in the contact point between chips and the third portion 13C occurs due to a change in cutting conditions, the chips tend to be brought into surface contact with the third portion 13C. This allows the generated chips to come into stable contact with the third portion 13C even under different cutting conditions. Consequently, good chip discharge performance is ensured under a wide range of cutting conditions.

[0089] As it is in the Fig. 3, in a side view, the first side 3b1 may include a first portion 3b11 having a curved shape protruding toward the bottom surface 5, and the uppermost portion 16 of the third portion 13C may include a portion whose distance from the first portion 3b11 is constant. In other words, the first portion 3b11 having a curved shape may be the first curved portion 3b11. With this configuration, both ends of a chip generated by transferring the shape of the cutting edge 9 can be stably brought into contact with the third portion 13C. This results in an effective chip winding action by the breaker portion 13.

[0090] The expression "the distance between the uppermost section 16 and the third section 13C and the first part 3b11 is constant" means that the distance between them must be essentially constant, without being exactly constant. That is, both can deviate by approximately ±1 mm.

[0091] Examples of the curved shape of the first part 3b11 include a circular arc shape. In cases where the first part 3b11 has a circular arc shape, a radius of curvature of the first part 3b11 can be set, for example, to 15 to 35 mm.

[0092] A portion of the first part 3b11 that is closest to the lower surface 5 may be located closer to the first corner 3a1 than a center point M of the first part 3b11. In this case, a portion of the first part 3b11 that is closest to the lower surface 5 may also be located closest to the lower surface 5 in the entirety of the first side 3b1.

[0093] With the above configuration, a region of the cutting edge 9 having a relatively small cutting edge height can be ensured extensively on the inner edge side. This results in a relatively strong crushing effect by the crushing part 13 on the inner edge side, thereby improving the chip discharge efficiency on one side of the inner edge side.

[0094] As it is in the Fig. 3, each of the first region 17, the second region 18, and the third region 19 may be a region of the upper surface 3, which is arranged on the inside of the first part 3b11. In particular, when both ends of the first part 3b11 are designated as p1 and p2, respectively, in a side view, each of the first region 17, the second region 18, and the third region 19 may be arranged closer to the central axis X1 than both ends p1 and p2 of the first part 2b11, as shown in Fig. 3 is shown.

[0095] With the above configuration, the first portion 17, the second portion 18, and the third portion 19 are arranged corresponding to the first part 3b11. This enhances the effect of stably bringing both ends of a chip, which is generated by transferring the shape of the first portion 3b11 when the first portion 3b11 is used as a part of the cutting edge 9, into contact with the third portion 13C of the breaker part 13.

[0096] As it is in the Fig. 4, in a plan view, the uppermost portion 16 of the third portion 13C may have a portion whose distance from the first part 3b11 is constant.

[0097] When the uppermost portion 16 of the third portion 13C has the above configuration, the difference in cutting speed between the inner and outer edges of the drill during a turning operation is small. Therefore, it is easy to bring the chip into contact with the third portion 13C even under cutting conditions where there is no significant difference between the chip thread diameter on the inner and outer edges.

[0098] As it is in the Fig. 2 to 4, the first side 3b1 may further comprise a second part 3b12 and a third part 3b13, which is arranged closer to the second corner 3a2 than the first part 3b11. In this case, as shown in the Fig. 3, in a side view, the second part 3b12 may have a curved shape which is recessed with respect to the lower surface 5, and the third part 3b13 may have a rectilinear shape.

[0099] The above configuration ensures a smooth connection between the first part 3b11, which has the recessed, curved shape, and the third part 3b13, which has the rectilinear shape on the first side 3b1. In other words, in cases where the second part 3b12 has the curved shape, the second part 3b12 may be the second curved part 3b12.

[0100] Alternatively, as stated in the Fig. 3, in a side view, the second part 3b12 and the third part 3b13 may be arranged closer to the second corner 3a2 than the uppermost portion 16 of the third portion 13C on the side of the second corner 3a2.

[0101] Similar to the first part 3b11, examples of the curved shape of the second part 3b12 include a circular arc shape. When the second part 3b12 has a circular arc shape, a radius of curvature of the second part 3b12 can be set to, for example, 3.5 to 9 mm. When the first part 3b11 and the second part 3b12 have a circular arc shape, the radius of curvature of the first part 3b11 can be larger than the radius of curvature of the second part 3b12.

[0102] Although the first side 3b1 in the embodiment shown in the Fig. 3, the first side 3b1 is not limited to one formed only of these three parts. Specifically, a connecting portion (not shown) may be interposed to smoothly connect these parts. For example, a rectilinear portion may be interposed between the first part 3b11 and the second part 3b12.

[0103] A so-called honing process can be performed on a portion of the ridge line where the upper surface 3 intersects the side surface 7, and the cutting edge 9 is formed. That is, the ridge line where the upper surface 3 intersects the side surface 7 does not need to have a precise line shape obtained by intersecting two surfaces. The cutting edge 9 has improved strength by applying the honing process to a region where the upper surface intersects the side surface 7. Examples of the honing process include a circular honing process that converts the region into a curved surface shape. Cutting tool (drill)

[0104] A drill 101 in one of the embodiments is described below with reference to the drawings.

[0105] As it is in the Fig. As shown in FIGS. 9 to 11, the drill 101 of the embodiment includes a holder 103 having a rod shape and extending along a rotation axis Y1, and an inner cutting edge insert 105 and an outer cutting edge insert 107 fixed to a first end 103a of the holder 103. The drill 101 is usable for, for example, a drilling operation. The insert 1 shown in one of the embodiments of the present disclosure is used as the outer cutting edge insert 107 in the present disclosure. An insert (first insert) different from the insert 1 in one of the embodiments is used as the inner cutting edge insert 105 in the present disclosure. Alternatively, the insert 1 in one of the embodiments may also be used as the inner cutting edge insert 105 in addition to the outer cutting edge insert 107.

[0106] The holder 103 includes a main body 109, a first chip discharge groove 111 (hereinafter also simply referred to as "a first groove 111"), and a second chip discharge groove 113 (hereinafter also simply referred to as "a second groove 113"). The main body 109 has a rod shape extending along the rotation axis Y1 from the first end 103a to the second end 103b. The main body 109 is rotated around the rotation axis Y1 during a cutting operation.

[0107] The main body 109 may include a holder portion 115, referred to as a "shank," which is held, for example, by a rotating spindle of a machine tool (not shown), and a cutting portion 117, referred to as a "body," which is located closer to a front end side than the holder portion 115. The holder portion 115 is a portion designed according to the shape of the spindle and the like in the machine tool. The cutting portion 117 is a portion whose end is arranged on a side of the first end 103a to accept attachment of the inserts 105 and 107. The cutting portion 117 plays a pivotal role in the cutting operation of a workpiece. An arrow Y2 indicates a rotation direction of the main body 109.

[0108] An inner pocket 119 and an outer pocket 121 are provided on one side of the first end 103 of the cutting portion 117 of the main body 109. The inner pocket 119 is a recessed portion located on an inner edge side of the first end 103a of the cutting portion 117 and is configured to allow the attachment of the inner cutting edge insert 105. The outer pocket 121 is a recessed portion located on an outer edge side of the first end 103a of the cutting portion 117 and is configured to allow the attachment of the outer cutting edge insert 117.

[0109] The outer pocket 121 is located further away from the rotation axis Y1 than the inner pocket 119, as shown in the Fig. 9. To prevent contact of the inner cutting edge insert 105 with the outer cutting edge insert 107, the inner pocket 119 and the outer pocket 121 must be spaced apart from each other. The term "inner edge side" refers to a side close to the rotation axis Y1. The term "outer edge side" refers to a side remote from the rotation axis Y1.

[0110] The inner cutting edge insert 105 and the outer cutting edge insert 107 are removably secured to the inner pocket 119 and the outer pocket 121, respectively. In other words, the inner cutting edge insert 105 is secured to the inner edge side at the first end 103a of the holder 103, and the outer cutting edge insert 107 (insert 1) is secured to the outer edge side at the first end 103a of the holder 103. The inner cutting edge insert 105 is secured so that a cutting edge 106 of the inner cutting edge insert 105 intersects the rotation axis Y1.

[0111] In a front view, a rotation curve of the cutting edge 106 on the inner cutting edge insert 105 partially overlaps with a rotation curve of the cutting edge 9 on the outer cutting edge insert 107 (not shown). In the front end view, the rotation curve of the cutting edge 106 on the inner cutting edge insert 105 and the rotation curve of the cutting edge 9 on the outer cutting edge insert 107 may overlap with the entire cutting portion 117 of the main body. A drilling operation having an outer diameter of the cutting portion 117 of the main body 109 is executable by the cutting edge 106 of the inner cutting edge insert 105 and the cutting edge 9 of the outer cutting edge insert 107.

[0112] The term "front end view" refers to a state in which the drill 101 is viewed toward the first end 103a of the holder 103. An end portion of the first part located on the outer edge side corresponds to one of both end portions of the first part located on one side of the second part.

[0113] As it is in the Fig. 9 to 11, the first groove 111 may extend helically around the rotation axis Y1 in a direction from the inner cutting edge insert 105 toward a second end 103b of the holder 103. The second groove 113 may extend helically around the rotation axis Y1 in a direction from the outer cutting edge insert 107 toward the second end 103b of the holder 103. In the embodiment shown in Fig. 9, the first groove 111 and the second groove 113 are arranged on the cutting portion 117 in the main body 109 but not in the holding portion 115.

[0114] For example, an outer diameter of the cutting portion 117 can be set to 6 to 42.5 mm. For example, E = 2F to E = 12F, where E is a length of an axial line (a length of the cutting portion 117) and F is a diameter (outer diameter of the cutting portion 117).

[0115] For example, steel, cast iron, and aluminum alloy can be used as the material of the main body 109. Of these materials, high-strength steel is used for high rigidity.

[0116] The first groove 111 is primarily intended to discharge the chips generated by the cutting edge 106 of the inner cutting edge insert 105. During a cutting operation, the chips generated by the inner cutting edge insert 105 are discharged through the first groove 111 to one side of the second end 103b of the main body 109. The second groove 113 is primarily intended to discharge chips generated by the cutting edge 106 of the outer cutting edge insert 107. During the cutting operation, the chips generated by the outer cutting edge insert 107 are discharged through the second groove 113 to one side of the second end 103b of the main body 109.

[0117] A depth of each of the first groove 111 and the second groove 113 can be set, for example, to approximately 10 to 40% of an outer diameter of the cutting portion 117. The term "the depth of each of the first groove 111 and the second groove 113" refers to a value obtained by subtracting a distance between a bottom of each of the first groove 111 and the second groove 113 and the rotation axis Y1 from a radius of the cutting portion 117 in a cross section orthogonal to the rotation axis Y1.

[0118] A diameter of a web or core thickness can be set, for example, to approximately 20 to 80% of the outer diameter of the cutting section 117. The diameter of the web or core is equivalent to a diameter of a maximum circle (inner circle) that can be entered in a cross-section of the cutting section 117 orthogonal to the rotation axis Y1. In particular, for example, if the outer diameter D of the cutting section 117 is 20 mm, the depth of each of the first groove 111 and the second groove 113 can be set to approximately 2 to 8 mm.

[0119] With the drill 101 in the present disclosure, since the insert 1 is used as the outer cutting edge insert 107, chip clogging is less likely to occur, and stable chip discharge is achieved even when machining soft chips such as mild steel. This leads to improved accuracy of a machined surface of the workpiece. Process of manufacturing a machined or machined product

[0120] A method of manufacturing a machined product in one of the embodiments of the present disclosure is described below with reference to the Fig. 12 to 14 by describing the case of using the drill 101 in the foregoing embodiment.

[0121] The method of manufacturing a machined product in the embodiment comprises the following steps (1) to (4).

[0122] The step (1) serves to move the drill 101 (cutting tool) over a prepared workpiece 201 (see Fig. 12).

[0123] The step (2) serves to rotate the drill 101 around the rotation axis Y1 in a direction indicated by the arrow Y2 and to bring the drill 101 closer to the workpiece 201 in the Z1 direction (see Fig. 12 and Fig. 13).

[0124] The step (3) is to form a drilled hole 203 in the workpiece 201 by bringing the drill 101 further closer to the workpiece 201 to cause the cutting edge of the drill 101, which is rotated, to come into contact with a desired position of a surface of the workpiece 201 (see Fig. 13).

[0125] The step (4) serves to separate the drill 101 from the workpiece 201 in the Z2 direction (see Fig. 14).

[0126] Examples of materials of the workpiece 201 prepared in step (1) include aluminum, carbon steel, alloy steel, stainless steel, cast iron, and non-ferrous metals.

[0127] Step (2) can be performed, for example, by fixing the workpiece 201 to a table of the machine tool having the drill 101 attached thereto, and then bringing the drill 101, which is rotating, closer to the workpiece 201. In this step, the workpiece 201 and the drill 101 must be relatively close to each other. Alternatively, the workpiece 201 can be brought closer to the drill 101.

[0128] In step (3), in order to obtain a well-machined surface, it is preferable that a partial area on one side of the second end of the cutting portion of the drill 101 is not brought into contact with the workpiece 201. In other words, excellent chip discharge performance is achievable by the partial area, the partial area being used to serve as a chip discharge area.

[0129] Also in step (4), the workpiece 201 and the drill 101 must be separated relatively from each other, as in step (2) above. For example, the workpiece 201 can be separated from the drill 101.

[0130] The machined product having the drilled hole 203 can be obtained through the steps described above. With the method of manufacturing a machined product in the embodiment, it is possible to perform the cutting process due to the use of the drill 101 while smoothly discharging chips. Thus, it is possible to obtain the machined product having the highly accurate drilled hole 203.

[0131] When the foregoing cutting operation of the workpiece 201 is performed multiple times, for example, when a plurality of drilled holes 203 are formed in a single workpiece 201, it is necessary to repeat the step of bringing the cutting edge of the drill 101 into contact with different portions of the workpiece 201 while continuing to rotate the drill 101.

[0132] Although the embodiments in the present disclosure have been shown and described above, the present disclosure is not limited thereto. List of reference symbols 1 cutting insert or indexable insert (insert) 3 first surface (upper surface) 3a corner 3a1 first corner 3a2 second corner 3b page 3b1 first page 3b11 first part 3b12 second part 3b13 third part 5 lower surface (second surface) 7 Side surface (third surface) 9 Cutting edge 11 Through hole 13 Crusher part 13A first section 13B second section 13C third section 13D first, upper surface 13E second, upper surface 15 lower part (bottom part) 16 top section 17 first area 18 second area 19 third area 101 drills 103 holders 103a first end 103b second end 105 inner cutting edge insert (first cutting insert) 106 cutting edge 107 outer cutting edge insert 109 main body 111 first chip removal groove (first groove) 113 second chip removal groove (second groove) 115 stopping section 117 Cutting section 119 inner pocket 121 outer pocket 201 Workpiece 203 drilled hole H13 Height of the third section H3b Height of the first page L1 Distance on one side of the first corner L2 Distance on one side of the second corner L3 Distance from the bottom surface to the third section on one side of the first corner L4 Distance from the lower surface to the third section on the side of the second corner L5 Distance on one side of the first corner L6 Distance on one side of the second corner L7 Distance from the lower surface to the floor part on one side of the first corner L8 Distance from the lower surface to the floor part on the side of the second corner M Center of the first part R1 radius of curvature of the second section R2 radius of curvature of the second section r1 radius of curvature of the second section in the first area r2 radius of curvature of the second section in a cross-section orthogonal to the first side in the second region r3 radius of curvature of the second section in the third area S Reference plane X1 central axis of the through hole X2 area X3 area Y1 rotation axis Y2 arrow Z1 Z1 direction Z2 Z2 direction Θ1 Inclination angle of the first section Θ31 Inclination angle of the third section Θ32 Inclination angle of the third section P1, P2 both ends of the first part

Claims

[1] A cutting insert (1), comprising: a first surface (3) having a first side (3b1), a first corner (3a1) and a second corner (3a2) adjacent to the first side (3b1), and a breaker part (13) arranged along the first side (3b1), a second surface (5) arranged on an opposite side to the first surface (3), and a third surface (7) arranged between the first surface (3) and the second surface (5) along the first side (3b1), wherein the crusher part (13) has a first section (13A), a second section (13B) and a third section (13C), which are arranged in sequence starting from the first side (3b1), the first portion (13A) is an inclined surface which is inclined to approach the second surface (5) as it moves away from the first side (3b1), the third portion (13C) is an inclined surface which is inclined to separate from the second surface (5) as it moves away from the second portion (13B), an entirety of the second section (13B) is arranged closer to the second surface (5) than the first side (3b1), at least a portion of the third portion (13A) is arranged further away from the second surface (5) than the first side (3b1), and in a front view of the first surface (3) at a distance from the first side (3b1) to an uppermost portion of the third portion (13C) on an orthogonal line with respect to the first side (3b1), a maximum value at a side of the second corner (3a2) is greater than a maximum value at a side of the first corner (3a1), wherein the breaker part (13) has a first upper surface (13D) which is arranged on a side of the first corner (3a1) further inward on the first surface (3) than the third section (13C), and a second upper surface (13E) which is arranged on a side of the second corner (3a2) further inward on the first surface (3) than the third section (13C), the first upper surface (13D) is inclined to approach the second surface (5) as it moves from one side of the first corner (3a1) towards one side of the second corner (3a2), and the second upper surface (13E) is inclined to approach the second surface (5) as it moves away from the first side (3b1). [2] The cutting insert (1) according to claim 1, wherein the crusher part (13) has a bottom part (15) which extends along the first side (3b1), and in a front view of the first surface (3) at a distance from the first side (3b1) to the base part (15) on an orthogonal line with respect to the first side (3b1), a maximum value at a side of the second corner (3a2) is greater than a maximum value at a side of the first corner (3a1). [3] The cutting insert (1) according to claim 1 or 2, wherein the crusher part (13) has a bottom part (15) which extends along the first side, and at a distance from the second surface to the base part (15), a maximum value on one side of the second corner (3a2) is smaller than a maximum value on one side of the first corner (3a1). [4] The cutting insert (1) according to any one of claims 1 to 3, wherein in a cross section orthogonal to the first side (3b1), the second portion (13A) has a circular arc shape projecting toward the second surface (5). [5] The cutting insert (1) according to claim 4, wherein a radius of curvature of the second portion (13A) in a cross section orthogonal to the first side (3b1) at a side of the second corner (3a2) is larger than a radius of curvature of the second portion (13B) in a cross section orthogonal to the first side (3b1) at a side of the first corner (3a1). [6] The cutting insert (1) according to claim 5, wherein the crusher part (13) has a first region (17), a second region (18) and a third region (19), which are arranged in sequence from one side of the first corner (3a1) towards one side of the second corner (3a2), a radius of curvature of the first section (13A) in a cross-section orthogonal to the first side (3b1) in the first region (17) is constant, a radius of curvature of the second section (13B) in a cross-section orthogonal to the first side (3b1) in the third region (19) is constant and is greater than the radius of curvature of the second section (13B) in the cross-section orthogonal to the first side (3b1) in the first region (17), and a radius of curvature of the second portion (13B) in a cross section orthogonal to the first side (3b1) in the second region (18) increases as it moves from a side of the first region (17) toward a side of the third region (19). [7] The cutting insert (1) according to any one of claims 1 to 6, wherein, when viewed from one side of the third surface (7), the first side (3b1) has a first curved part having a curved shape projecting toward the second surface (5), and the uppermost portion of the third portion (13C) has a portion whose distance from the first curved portion is constant. [8] The cutting insert (1) according to claim 7, wherein the uppermost portion of the third portion (13C) has a portion whose distance from the first curved part is constant when viewed from a side of the first surface (3). [9] The cutting insert (1) according to claim 7 or 8, wherein, when viewed from one side of the third surface (7), the first side (3b1) further comprises a second curved part which is arranged closer to a side of the second corner (3a2) than the first curved part and which has a curved shape which is recessed against the second surface (5), and on a side of the second corner (3a2), the second curved part is arranged closer to a side of the second corner (3a2) than the uppermost portion of the third portion (13C). [10] The cutting insert (1) according to any one of claims 1 to 9, wherein an inclination angle (Θ1) of the first portion (13A) along the first side (3b1) is constant. [11] The cutting insert (1) according to any one of claims 1 to 10, wherein an inclination angle (Θ32) of the third portion (13C) at a side of the second corner (3a2) is smaller than an inclination angle (Θ31) of the third portion (13C) at a side of the first corner (3a1). [12] A drill (101), comprising: a holder (103) which has a rod shape and extends along a rotation axis from a first end (103a) towards a second end (103b), and a cutting insert (1) according to any one of claims 1 to 11, wherein the cutting insert (1) is arranged on one side of the first end (103a) of the holder (103). [13] A method of manufacturing a machined product, comprising: Rotating a drill (101) according to claim 12 around the axis of rotation, Bringing the drill (101), which is rotated, into contact with a workpiece (201), and Separating the drill (101) from the workpiece (201).

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