Cutting inserts and rotary cutting tools containing them

Abstract

The cutting insert includes an upper surface, a lower surface opposite to the upper surface, a first side surface and a second side surface connecting the upper surface and the lower surface, a mounting hole penetrating the upper surface and the lower surface, a first cutting edge formed at an edge of the upper surface meeting the first side surface, and a second cutting edge formed at an edge of the upper surface meeting the second side surface. The lower surface includes a ridge portion, and a first inclined surface and a second inclined surface respectively located on both sides of the ridge portion. When viewed from the lower surface, the first inclined surface and the second inclined surface have asymmetric shapes with respect to the ridge portion.

Description

Technical Field

[0003] , , , screw , , screw

[0001] The present disclosure relates to a rotary cutting tool used for milling a workpiece. The present disclosure also relates to a cutting insert mounted on such a rotary cutting tool.

Background Art

[0002] As an example of a rotary cutting tool used for milling, an end mill (also referred to as an "end milling cutter") is known. Different from a drill used only for hole drilling, an end mill has cutting edges on its outer periphery and tip, so it can be used for groove cutting, side cutting, etc. of a workpiece. Among end mills, a ball nose end mill with a round tip is divided into a solid ball nose end mill in which the end mill body and the ball nose part are integrally formed depending on whether a cutting insert is mounted, and an indexable ball nose end mill in which a cutting insert is replaceably mounted on the end mill body (or tool body).

Summary of the Invention

Problems to be Solved by the Invention

[0003] In an indexable ball nose end mill, usually, a cutting insert is screw coupled to the tool body by, but screw provides only a fastening force in the vertical direction of the cutting insert (for example, the direction in which the cutting insert is in close contact with the tool body by tightening of screw ), so it cannot sufficiently support the reaction force due to the cutting force. In particular, since a cutting insert used for a ball nose end mill has an arc-shaped edge for curved surface cutting, <​​​ screw This presented problems such as deformation and breakage of the cutting insert.

[0004] To solve these conventional problems, a ball nose end mill is disclosed that modifies the mounting structure of the cutting insert and the insert pocket provided in the tool body. In such a ball nose end mill, a groove is formed on the lower surface of the cutting insert, and a projection corresponding to the groove is formed on the bottom surface of the insert pocket into which the cutting insert is secured. screw The insert is fixed perpendicularly to the insert pocket and firmly secured to prevent rotation within the insert pocket by the connection between the projection and the groove. However, in the case of ball nose end mills with such a mounting structure, an additional manufacturing process is required to form the projection on the bottom surface of the insert pocket, and an additional grinding process is required to precisely machine the groove on the lower surface of the cutting insert, resulting in an increase in the unit cost of manufacturing the cutting insert. Furthermore, since cutting vibrations or cutting forces are concentrated at these connection points while the projection is coupled to the groove, fatigue increases, making the cutting insert more prone to breakage. [Means for solving the problem]

[0005] Various embodiments of this disclosure provide cutting inserts having a ridge formed on their lower surface so as to be stably fastened to the tool body of a rotary cutting tool. Furthermore, various embodiments of this disclosure provide cutting inserts having both a center edge and a peripheral edge. Also, various embodiments of this disclosure provide rotary cutting tools equipped with such cutting inserts.

[0006] One aspect of the present disclosure relates to a cutting insert. A cutting insert according to an exemplary embodiment includes a top surface; a bottom surface opposite the top surface; a first side surface and a second side surface connecting the top and bottom surfaces; a mounting hole penetrating the top and bottom surfaces; a first cutting edge formed on the edge of the top surface meeting the first side surface; a second cutting edge formed on the edge of the top surface meeting the second side surface; and first and second corner portions provided at both ends of the top surface where the first and second sides meet. The bottom surface includes a ridge and a first and second inclined surface located on both sides of the ridge, respectively, and when viewed from the bottom surface, the first and second inclined surfaces have an asymmetrical shape with respect to the ridge.

[0007] In one embodiment, the first cutting edge includes a peripheral edge extending in a curved shape from the first corner and a long edge connected to the peripheral edge and extending to the second corner, and the second cutting edge includes a center edge extending in a curved shape from the second corner and a short edge connected to the center edge and extending to the first corner, wherein the straight-line distance between the two sides of the long edge is longer than the straight-line distance between the two sides of the short edge.

[0008] In one embodiment, the long edge and the short edge may each have a linear shape.

[0009] In one embodiment, when the lower surface of the cutting insert is viewed, the ridge portion is separated from the second corner portion, inclined with respect to an imaginary line connecting the point where the peripheral edge and the long edge meet and the second corner portion, and can cross the mounting hole.

[0010] In one embodiment, when viewing the lower surface of the cutting insert, the ridge portion may be formed to extend from the edge of the lower surface adjacent to the long edge to the edge of the lower surface adjacent to the short edge.

[0011] In one embodiment, the ridge portion may be formed into a surface shape having a set width between the first inclined surface and the second inclined surface.

[0012] In one embodiment, the ridge portion may be formed in a linear shape where the first inclined surface and the second inclined surface meet.

[0013] In one embodiment, the first inclined surface and the second inclined surface may each be formed with an upward inclination as they move away from the ridge.

[0014] In one embodiment, the first and second inclined surfaces may be inclined at an angle of inclination within the range of 5° to 30° with respect to a reference line that is perpendicular to the central axis passing through the center of the mounting hole and extending in the direction of extension of the mounting hole.

[0015] In one embodiment, the upper surface includes a center surface where a mounting hole is formed, a land surface formed along the first cutting edge and the second cutting edge, and a rake surface formed between the center surface and the land surface, and when the cutting insert is viewed from the side, the first corner portion and the second corner portion may each be raised above the center surface.

[0016] Another aspect of this disclosure relates to rotary cutting tools for milling workpieces. A rotary cutting tool according to an exemplary embodiment comprises a cylindrical tool body having two rows of helical flutes formed at the longitudinal tip; a pair of cutting inserts interchangeably mounted on the tool body; and a pair of fasteners for securing each of the cutting inserts to the tool body. screw Includes: Each of a pair of cutting inserts has a top surface; a bottom surface facing the top surface and having a first and second inclined surface located on both sides of the ridge and the boundary of the ridge, respectively, and having an asymmetrical shape with respect to the ridge; a first and second side connecting the top and bottom surfaces; a pair screwThe device includes mounting holes penetrating the top and bottom surfaces so that each of the inserts can be fitted; first and second corner portions provided at both ends of the top surface where the first and second sides meet; a first cutting edge formed between the first side and the top surface, including a peripheral edge that extends in a curved shape from the first corner portion; and a second cutting edge formed between the second side and the top surface, including a center edge that extends in a curved shape from the second corner portion, with each of the two rows of spiral flutes having a first insert pocket and a second insert pocket for accommodating each of a pair of cutting inserts. The first cutting insert, provided in a pair of cutting inserts, is mounted in the first insert pocket such that its first corner is located axially forward of the tip of the tool body, and the peripheral edge of the first cutting insert is located radially outward of the tool body and axially forward of the tool body compared to the center edge. The second cutting insert, provided in a pair of cutting inserts, is mounted in the second insert pocket such that its second corner is located axially forward of the tool body, and the center edge of the second cutting insert is located radially outward of the tool body and axially forward of the tool body compared to the peripheral edge.

[0017] In one embodiment, when the first cutting insert is viewed from the side, the lower surface of the first cutting insert may have a V-shape. The first insert pocket may include a first bottom surface that supports the V-shaped lower surface of the first cutting insert, and a first side wall that extends from the inside of the first bottom surface in a radially outward direction from the tool body to support the second side surface of the first cutting insert. Also, when the second cutting insert is viewed from the side, the lower part of the second cutting insert may have a V-shape. The second insert pocket may include a second bottom surface that supports the V-shaped lower surface of the second cutting insert, and a second side wall that extends from the inside of the second bottom surface in a radially outward direction from the tool body to support the first side surface of the second cutting insert.

[0018] In one embodiment, the first bottom surface may include a first outer bottom surface that contacts a first inclined surface adjacent to the peripheral edge of the first cutting insert, a first inner bottom surface that contacts a second inclined surface adjacent to the center edge of the first cutting insert, and a first ridge receiving groove that is formed between the first outer bottom surface and the first inner bottom surface and that receives the ridge portion of the first cutting insert. Further, the second bottom surface may include a second inner bottom surface that contacts a first inclined surface adjacent to the peripheral edge of the second cutting insert, a second outer bottom surface that contacts a second inclined surface adjacent to the center edge of the second cutting insert, and a second ridge receiving groove that is formed between the second inner bottom surface and the second outer bottom surface and that receives the ridge portion of the second cutting insert.

[0019] In one embodiment, the rotary cutting tool may be a ball nose end mill.

Advantages of the Invention

[0020] According to an embodiment of the present disclosure, due to the protruding V-shaped role of the bottom surface of the cutting insert, the rotary cutting tool has stable fastening ability even in three-dimensional cutting in the rotational direction, radial direction, and axial direction. Since the lower surface of the cutting insert has a pair of inclined surfaces formed in an asymmetric shape, cross-mounting of the cutting inserts can be prevented (that is, it is prevented that the second cutting insert is mounted in the first insert pocket, and it is prevented that the first cutting insert is mounted in the second insert pocket). Further, the lower surface of the cutting insert is distributed by the ridge portion so that the pair of inclined surfaces have a pocket contact surface that is maximally uniform. Therefore, a stable tool life can be expected, and through this, the productivity of the cutting process can be improved.

Brief Description of the Drawings

[0021] The accompanying drawings, which are included in and constitute a part of this specification, illustrate embodiments of the present disclosure.

[0022] FIG. 1 is a perspective view showing a cutting insert according to an embodiment of the present disclosure.

[0023] FIG. 2 is a perspective view of a cutting insert according to an embodiment of the present disclosure as viewed from another direction.

[0024] FIG. 3 is a plan view of a cutting insert according to an embodiment of the present disclosure.

[0025] FIG. 4 is a bottom view of the cutting insert shown in FIG. 1.

[0026] FIG. 5 is a side view of a cutting insert according to an embodiment of the present disclosure.

[0027] FIG. 6 is a side view of a cutting insert according to another embodiment of the present disclosure.

[0028] FIG. 7 is a perspective view showing a rotary cutting tool according to an embodiment of the present disclosure.

[0029] FIG. 8 is an exploded perspective view of a rotary cutting tool according to an embodiment of the present disclosure.

[0030] FIG. 9 is a drawing showing the separation of the first cutting insert from the tool body in a rotary cutting tool according to an embodiment of the present disclosure.

[0031] FIG. 10 is a drawing showing the separation of the second cutting insert from the tool body in a rotary cutting tool according to an embodiment of the present disclosure.

[0032] FIG. 11 is a drawing of a rotary cutting tool according to an embodiment of the present disclosure as viewed from the front in the axial direction.

[0033] FIG. 12 is a drawing schematically showing the state in which a workpiece is being milled by a rotary cutting tool according to an embodiment of the present disclosure.

MODE FOR CARRYING OUT THE INVENTION

[0034] The embodiments of the present disclosure are exemplified for the purpose of explaining the technical idea of the present disclosure. The scope of rights according to the present disclosure is not limited to the embodiments presented below or the specific descriptions regarding these embodiments.

[0035] All technical and scientific terms used in this disclosure, unless otherwise defined, have meanings that would be generally understood by a person with ordinary skill in the art to which this disclosure pertains. All terms used in this disclosure have been chosen for the purpose of further clarifying this disclosure and not to limit the scope of rights granted by this disclosure.

[0036] Expressions such as “includes,” “equipped with,” and “possess” as used in this disclosure should be understood as open-ended terms that may include other embodiments, unless otherwise specifically mentioned in the phrase or sentence containing such expression.

[0037] Unless otherwise specified, singular expressions described in this disclosure may have plural meanings, and this also applies to singular expressions described in the claims.

[0038] The terms "First," "Second," etc., used in this disclosure are used to distinguish between multiple components and do not limit the order or importance of those components.

[0039] Directional indicators such as "up" and "top" used in this disclosure are based on the direction in which the top surface is located relative to the bottom surface in the attached drawings. Directional indicators such as "down" and "bottom" mean the opposite direction to "up" or "top". The cutting inserts shown in the attached drawings may be oriented differently, and these directional indicators may be interpreted accordingly.

[0040] The following describes embodiments of cutting inserts and cutting tool assemblies including them with reference to the attached drawings. In the attached drawings, identical or corresponding components are given the same reference numerals. In the following description of embodiments, redundant descriptions of identical or corresponding components may be omitted. However, the omission of technical information regarding a component does not mean that such a component is not included in the embodiment.

[0041] Figure 1 is a perspective view showing a cutting insert (100) according to one embodiment of the present disclosure. Figure 2 is a perspective view of the cutting insert (100) shown in Figure 1 from another direction.

[0042] Referring to Figures 1 and 2, a cutting insert (100) according to one embodiment has an upper surface (110), a lower surface (120) opposite the upper surface (110), and a plurality of side surfaces connecting the upper surface (110) and the lower surface (120). Cutting edges are provided on the edges of the upper surface (110) that meet the plurality of side surfaces. Such a cutting insert (100) may be referred to as a single-sided cutting insert.

[0043] In one embodiment, the cutting insert (100) has a plurality of sides, namely a first side (130) and a second side (140). Each of the first side (130) and the second side (140) may be partially curved and partially flat. However, it is not limited to this, and depending on the shape of the cutting edge, each of the first side (130) and the second side (140) may be entirely curved.

[0044] The cutting insert (100) has mounting holes (150) that penetrate the top surface (110) and bottom surface (120) so that the cutting insert (100) can be mounted on a rotary cutting tool. screw When tightened, the mounting hole (150) is designed so that the cutting insert (100) is pressed against the tool body of the rotary cutting tool and makes close contact. screw A stepped portion (150A) is formed that allows the head to catch on.

[0045] The cutting insert (100) has a first cutting edge (160) formed on the edge of the top surface (110) that meets the first side surface (130). The cutting insert (100) also has a second cutting edge (170) formed on the edge of the top surface (110) that meets the second side surface (140). With respect to the cutting insert (100) as a reference to the central axis (CL) that passes through the center (CP) of the mounting hole (150) and extends in the direction of extension of the mounting hole (150), the first cutting edge (160) and the second cutting edge (170) of the cutting insert (100) have different shapes. That is, the cutting insert (100) according to one embodiment can be mounted on a rotary cutting tool to use the first cutting edge (160) or to use the second cutting edge (170). In other words, all the cutting edges provided on the cutting insert (100) can be used, making it economical to use.

[0046] As shown in Figures 1 and 2, the upper surface (110) of the cutting insert (100) has a shape similar to an ellipse. The upper surface (110) has a first corner portion (C1) and a second corner portion (C2) at both ends where the first side portion (130) and the second side portion (140) meet. Various mark portions (111, 112), such as grooves or protrusions, may be formed on the upper surface (110) of the cutting insert (100) so that the mounting direction of the cutting insert (100) can be easily confirmed with the naked eye when the cutting insert (100) is mounted on a rotary cutting tool. The first corner portion (C1) is located relatively closer to the mark portions (111, 112) than the second corner portion (C2).

[0047] A cutting insert (100) according to one embodiment has a V-shaped lower surface (120) so that it can be stably mounted on a rotary cutting tool even when subjected to radial force (main force), transfer direction force (distributed force), and axial force (axial force) during machining of the workpiece (e.g., end milling). That is, the lower surface (120) includes a ridge portion (121) and a first inclined surface (122) and a second inclined surface (123) located on both sides of the ridge portion (121), respectively. The ridge portion (121) is formed to traverse between the edge of the lower surface (120) corresponding to the first cutting edge (160) and the edge of the lower surface (120) corresponding to the second cutting edge (170).

[0048] The first inclined surface (122) and the second inclined surface (123) of the lower surface (120) have an asymmetrical shape with respect to the ridge portion (121), which prevents the cutting insert (100) from being incorrectly mounted on the rotary cutting tool. This will be explained again in relation to the rotary cutting tool described later.

[0049] On the other hand, in the cutting insert (100), in order to improve cutting force, the first side surface (130) and the second side surface (140) may each be formed inclined with respect to the top surface (110) so as to have a positive relief angle.

[0050] Figure 3 is a plan view of a cutting insert (100) according to one embodiment of the present disclosure. Figure 4 is a bottom view of a cutting insert (100) according to one embodiment of the present disclosure.

[0051] As shown in Figure 3, the upper surface (110) of the cutting insert (100) includes a center surface (151) in which a mounting hole (150) is formed in its central portion. The upper surface (110) also includes a land surface (152) formed along the first cutting edge (160) and the second cutting edge (170). The land surface (152) may be formed as a negative land surface having a set width (WL). The land surface (152) prevents breakage of the cutting insert that occurs in the initial stages of cutting the workpiece and helps maintain the strength of the cutting edge. The upper surface (110) includes a rake surface (153) formed between the center surface (151) and the land surface (152). In the cutting insert (100), the first corner portion (C1) and the second corner portion (C2) are formed to be raised above the center surface (151) (see Figures 5 and 6). The rake surface (153) is formed to include a curved surface. The chips generated during the cutting process of the workpiece can be guided along the rake surface (153) and discharged smoothly.

[0052] Referring to Figures 3 and 4, the first cutting edge (160) includes a peripheral edge (161) that extends in a curved shape from the first corner (C1), and a long edge (162) that is connected to the peripheral edge (161) and extends to the second corner (C2). The second cutting edge (170) includes a center edge (171) that extends in a curved shape from the second corner (C2), and a short edge (172) that is connected to the center edge (171) and extends to the first corner (C1).

[0053] In one embodiment, the straight-line distance (D1) between the two sides of the long edge (162) is longer than the straight-line distance (D2) between the two sides of the short edge (172). Here, the straight-line distance (D1) between the two sides of the long edge (162) means the straight-line distance between one side of the long edge (162) that meets the peripheral edge (161) and the other side of the long edge (162) that extends to the second corner (C2), and the straight-line distance (D2) between the two sides of the short edge (172) means the straight-line distance between one side of the short edge (172) that meets the center edge (171) and the other side of the short edge (172) that extends to the first corner (C1).

[0054] In one embodiment, the long edge (162) and the short edge (172) each have a straight shape. However, the long edge (162) and the short edge (172) can be transformed into a variety of shapes, including curved shapes.

[0055] As shown in Figure 4, the lower surface (120) is divided into a first inclined surface (122) and a second inclined surface (123) by the ridge portion (121). The ridge portion (121) is formed such that the first inclined surface (122) and the second inclined surface (123) have asymmetrical shapes, that is, the first inclined surface (122) and the second inclined surface (123) differ in area and shape. In one embodiment, the ridge portion (121) is formed to be inclined with respect to a virtual line (VL) connecting the point (P) where the peripheral edge (161) and the long edge (162) meet, separated from the second corner portion (C2), and the second corner portion (C2). The ridge portion (121) is formed to cross the mounting hole (150). As in one embodiment, if the long edge (162) has a linear shape, the virtual line (VL) may be formed to extend along the long edge (162).

[0056] In one embodiment, the ridge portion (121) is formed to extend from the edge of the lower surface (120) adjacent to the long edge (162) to the edge of the lower surface (120) adjacent to the short edge (172). In the cutting insert (100), the lower surface (120), like the upper surface (110), has a shape similar to an ellipse having two corner portions [i.e., a first corner portion (C1) and a second corner portion (C2)]. Here, for example, the edge of the lower surface (120) adjacent to the long edge (162) formed on the upper surface (110) may mean the edge of the lower surface (120) located below the long edge (162) from the direction in which the cutting insert (100) shown in Figure 1 is positioned. If the ridge portion (121) extending from the edge of the lower surface (120) adjacent to the long edge (162) extends toward the edge of the lower surface (120) adjacent to the peripheral edge (161), or toward the edge of the lower surface (120) adjacent to the center edge (171), then the first inclined surface (122) and the second inclined surface (123) cannot be formed to have equal size (for example, the size of the area of ​​the portion that contacts the rotary cutting tool when mounted on the rotary cutting tool). Furthermore, since the cutting insert (100) is mounted on the rotary cutting tool such that the first corner portion (C1) or the second corner portion (C2) faces axially forward at the tip of the rotary cutting tool (see Figures 9 and 10), if the ridge portion (121) is formed to extend from the edge of the lower surface (120) adjacent to the peripheral edge (161) to the edge of the lower surface (120) adjacent to the center edge (171), even if the lower surface (120) of the cutting insert (100) is formed in a V shape, it becomes difficult to stably support the axial component of the cutting force generated during machining of the workpiece. As a result, cutting vibration may occur, potentially degrading the machining quality of the workpiece. In addition, problems such as breakage or detachment of the cutting insert (100) may occur, reducing tool life and potentially lowering machining productivity.

[0057] In this way, by forming the ridge portion (121) to extend from the edge of the lower surface (120) separated from the second corner portion (C2), and by forming the ridge portion (121) to be inclined with respect to the imaginary line (VL), the two inclined surfaces [first inclined surface (122) and second inclined surface (123)] on the lower surface (120) can be distributed as evenly as possible. Therefore, whether the cutting insert (100) is mounted on a rotary cutting tool to use the first cutting edge (160) or to use the second cutting edge (170), a sufficient support surface (for example, the area of ​​the part that contacts and is supported by the rotary cutting tool) can be provided, enabling a firm and stable mounting. Furthermore, by having the first inclined surface (122) and the second inclined surface (123) separated by the ridge portion (121) have an asymmetrical shape, it is possible to prevent the cutting insert (100) from being incorrectly mounted on the rotary cutting tool. In other words, the cutting insert (100) can be efficiently mounted onto the rotary cutting tool.

[0058] The angle (A) at which the ridge portion (121) is inclined with respect to the imaginary line (VL) can be set to a range that allows for the most even distribution of the areas of both inclined surfaces [first inclined surface (122) and second inclined surface (123)] within the limits of error-proofing.

[0059] Figure 5 is a side view of a cutting insert (100) according to one embodiment of the present disclosure. Figure 6 is a side view of a cutting insert (100') according to another embodiment of the present disclosure.

[0060] Referring to Figures 5 and 6, the ridge portion (121) can be formed as a surface shape having a set width (WR) between the first inclined surface (122) and the second inclined surface (123) (see Figure 5). However, the shape of the ridge portion (121) is not limited to this, and it can also be formed as a linear shape, such as the boundary line where the first inclined surface (122) and the second inclined surface (123) meet (see Figure 6).

[0061] As shown in Figures 5 and 6, when viewing the cutting inserts (100, 100') in the direction facing approximately the first corner (C1), the first inclined surface (122) and the second inclined surface (123) are formed to be inclined upward as they move away from the ridge (121). That is, each of the cutting inserts (100, 100') has a V-shaped or similarly shaped lower surface (120).

[0062] Each of the first inclined surface (122) and the second inclined surface (123) is inclined at an angle of inclination (B) in the range of 5° to 30° with respect to a reference line (BL) that is perpendicular to the central axis (CL) extending in the direction of the mounting hole (150). In one embodiment, each of the first inclined surface (122) and the second inclined surface (123) has an angle of inclination (B) of 10° with respect to the reference line (BL). If the angle of inclination (B) is less than 5°, the lower surface (120) becomes nearly flat, making it difficult to effectively support the radial force component (main force component), transfer direction force component (distributed force), and axial force component (axial force) generated during the cutting of the workpiece in the insert pocket of the tool body into which the cutting insert (100) is mounted. Furthermore, if the angle of inclination (B) exceeds 30°, a deep groove must be formed in the insert pocket of the tool body into which the cutting insert (100) is mounted, which structurally weakens the rigidity of the tool body itself.

[0063] The following describes a rotary cutting tool to which the cutting insert described in the above embodiment is interchangeably mounted. In the following description, any information that overlaps with the description of the cutting insert (100) described above will be briefly mentioned or omitted.

[0064] Figure 7 is a perspective view showing a rotary cutting tool (1000) according to one embodiment of the present disclosure. Figure 8 is an exploded perspective view of the rotary cutting tool (1000) shown in Figure 7.

[0065] In Figure 8, the rotary cutting tool (1000) has a rotation axis (RA) that defines the direction of rotation (S). The rotary cutting tool (1000) may be referred to as a milling cutter. On the rotation axis (RA), arrow (FAD) points in the axial direction toward the front of the rotary cutting tool (1000), and arrow (RAD) points in the axial direction toward the rear of the rotary cutting tool (1000). Also, in Figure 8, arrow (ROD) points in the radially outward direction of the rotary cutting tool (1000), and arrow (RID) points in the radially inward direction of the rotary cutting tool (1000). Here, the radially inward direction (RID) of the rotary cutting tool (1000) points toward the center of rotation of the rotary cutting tool (1000), and the radially outward direction (ROD) of the rotary cutting tool (1000) points in the opposite direction.

[0066] Referring to Figures 7 and 8, a rotary cutting tool (1000) according to one embodiment comprises a pair of cutting inserts (100), a tool body (200), and a pair screw (300) is included. The rotary cutting tool (1000) may be referred to as a ball-nose end mill capable of machining curved surfaces of workpieces. In particular, the rotary cutting tool (1000) may be referred to as an indexable ball-nose end mill having two cutting edges.

[0067] The tool body (also called the shank) (200) is cylindrical. A pair of cutting inserts (100) are mounted on the longitudinal front end (201) of the tool body (200), and the tool body (200) is mounted on the milling machine by its longitudinal rear end (202).

[0068] The tip (201) of the tool body (200) has two rows of spiral flutes (210) to facilitate chip ejection during cutting of the workpiece. Each of the two rows of spiral flutes (210) has a pocket for accommodating a cutting insert (100), namely a first insert pocket (220) and a second insert pocket (230) (see Figures 9 and 10). The cutting insert (100) is mounted in the first insert pocket (220) and the second insert pocket (230) with opposite orientations, and a pair screw Each is fixed to the tool body (200) by (300).

[0069] The cutting insert (100) is mounted on the tool body (200) such that different cutting edges of the cutting insert (100) are used for milling. For example, when milling a workpiece using a rotary cutting tool (1000) according to one embodiment, one of the cutting edges of the cutting insert (100) may be used to cut the side surface of the workpiece, and the other cutting edge of the cutting insert (100) may be used to cut the top surface (flat or groove) of the workpiece.

[0070] Figure 9 is a drawing showing the first cutting insert (100A) separated from the tool body (200) in a rotary cutting tool (1000) according to one embodiment of the present disclosure. Figure 10 is a drawing showing the second cutting insert (100B) separated from the tool body (200) in a rotary cutting tool (1000) according to one embodiment of the present disclosure. Figure 11 is a drawing of the rotary cutting tool (1000) according to one embodiment of the present disclosure viewed from the axial front (FAD).

[0071] For the sake of explanation, in the following, the cutting insert (100) fitted into the first insert pocket (220) of the rotary cutting tool (1000) will be referred to as the first cutting insert, and the cutting insert (100) fitted into the second insert pocket (230) of the rotary cutting tool (1000) will be referred to as the second cutting insert.

[0072] Referring to Figures 9 to 11, the first cutting insert (100A) is mounted in the first insert pocket (220) such that the first corner portion (C1) is located axially forward (FAD) and in a similar direction to the tip of the tool body (200). Therefore, the peripheral edge (161) of the first cutting insert (100A) is located radially outward (ROD) and axially forward (FAD) of the tool body (200) compared to the center edge (171). Similarly, the second cutting insert (100B) is mounted in the second insert pocket (230) such that the second corner portion (C2) is located axially forward (FAD) and in a similar direction to the tool body (200). Therefore, the center edge (171) of the second cutting insert (100B) is located radially outward (ROD) and axially forward (FAD) of the tool body (200) compared to the peripheral edge (161).

[0073] Since the first cutting edge (160), consisting of a peripheral edge (161) and a long edge (162), and the second cutting edge (170), consisting of a center edge (171) and a short edge (172), have different shapes, when the tool body (200) rotates, the cutting edges that contribute to the cutting of the first cutting insert (100A) and the second cutting insert (100B) rotate in such a way that they have different trajectories.

[0074] When the first cutting insert (100A) is viewed from the side, its lower surface (120) has a V-shape. The first insert pocket (220) comprises a first bottom surface (221) and a first side wall (222). When the first cutting insert (100A) is fitted into the first insert pocket (220), the first bottom surface (221) supports the V-shaped lower surface (120) of the first cutting insert (100A), and the first side wall (222), which extends from the inside of the first bottom surface (221) in the radially outward direction (ROD) of the tool body (200), supports the second side surface (140) of the first cutting insert (100A). A fastening hole (223) is formed in the first bottom surface (221), and the fastening hole (223) is for mounting the first cutting insert (100A). screw(300) may be concluded.

[0075] Similarly, when the second cutting insert (100B) is viewed from the side, its lower surface (120) has a V-shape. The second insert pocket (230) comprises a second bottom surface (231) and a second side wall (232). When the second cutting insert (100B) is fitted into the second insert pocket (230), the second bottom surface (231) supports the V-shaped lower surface (120) of the second cutting insert (100B), and the second side wall (232), which extends from the inside of the second bottom surface (231) in the radially outward direction (ROD) of the tool body (200), supports the first side surface (130) of the second cutting insert (100B). A fastening hole (233) is formed in the second bottom surface (231), and the fastening hole (233) is for mounting the second cutting insert (100B). screw (300) may be concluded.

[0076] The first bottom surface (221) of the first insert pocket (220) includes a first outer bottom surface (221A), a first inner bottom surface (221B), and a first ridge housing groove (221C). When the first cutting insert (100A) is mounted in the first insert pocket (220), the first inclined surface (122) of the bottom surface (120) adjacent to the peripheral edge (161) is supported in contact with the first outer bottom surface (221A), and the second inclined surface (123) of the bottom surface (120) adjacent to the center edge (171) is supported in contact with the first inner bottom surface (221B). At this time, the ridge portion (121) of the bottom surface (120) is located within the first ridge housing groove (221C).

[0077] Furthermore, the second bottom surface (231) of the second insert pocket (230) includes a second outer bottom surface (231A), a second inner bottom surface (231B), and a second ridge housing groove (231C). When the second cutting insert (100B) is mounted in the second insert pocket (230), the second inclined surface (123) of the adjacent bottom surface (120) is supported in contact with the second outer bottom surface (223A), and the first inclined surface (122) of the adjacent bottom surface (120) is supported in contact with the second inner bottom surface (231B). At this time, the ridge portion (121) of the bottom surface (120) is located within the second ridge housing groove (231C).

[0078] Relief grooves (240) are formed between the first bottom surface (221) and the first side wall (222) of the first insert pocket (220), and between the second bottom surface (231) and the second side wall (232) of the second insert pocket (230) by end milling or drilling. The relief grooves (240) prevent damage to the cutting edges of the first cutting insert (100A) and the second cutting insert (100B), and allow the first cutting insert (100A) and the second cutting insert (100B) to be accurately positioned in the insert pockets.

[0079] Furthermore, grooves (250) are formed in the radially outward (ROD) portions of the first side wall (222) and the second side wall (232) of the tool body (200), extending axially backward (RAD) from the tip of the tool body (200), thereby allowing the cutting insert (100) to be easily mounted into the insert pocket. When the cutting insert (100) is mounted on the tool body (200), a portion (260) of the groove (250) located axially backward (RAD) can cover a portion of the inner edge of the upper surface (110). Therefore, it is possible to structurally prevent chips generated during milling of the workpiece from flowing between the cutting insert (100) and the insert pocket.

[0080] As shown in Figures 9 and 10, the tool body (200) is provided with openings (270) that open toward the first insert pocket (220) and the second insert pocket (230), respectively. Furthermore, the tool body (200) is provided with a tool hole (not shown) that extends longitudinally and connects to the opening (270). During milling of the workpiece, cutting oil supplied from the milling machine is supplied through the tool hole and ejected through the opening (270) to facilitate chip removal.

[0081] Figure 12 is a schematic diagram showing how a workpiece (10) is milled by a rotary cutting tool (1000) according to one embodiment of the present disclosure.

[0082] As shown in Figure 12, when cutting a workpiece (10) by making radial cuts (M1) and axial cuts (M2) while moving a rotating cutting tool (1000) (M3), radial force components (Fx), transport force components (Fy), and axial force components (Fz) act on the rotating cutting tool (1000). In one embodiment of the rotating cutting tool (1000), the lower surface (120) of the cutting insert (100) is formed in a V shape, and the insert pocket into which the cutting insert (100) is mounted has a corresponding bottom shape. Therefore, the rotating cutting tool (1000) can stably support the force components acting in the three axial directions. In other words, during milling, the radial force (Fx) and axial force (Fz) can be supported by the first outer bottom surface (221A) and first inner bottom surface (221B) of the first insert pocket (220), and the second outer bottom surface (231A) and second inner bottom surface (231B) of the second insert pocket (230), while the transport force (Fy) can be supported by the first side wall (222) of the first insert pocket (220) and the second side wall (232) of the second insert pocket (230) (see Figures 9 and 10).

[0083] In one embodiment, since the first side wall (222) and the second side wall (232) include portions that extend radially outward (ROD) of the tool body (200), the first side wall (222) and the second side wall (232) can also support a portion of the axial force component (Fz).

[0084] Although the technical concept of this disclosure has been explained above by some embodiments and examples shown in the attached drawings, it is important to understand that various substitutions, modifications, and alterations may be made, provided that they do not deviate from the technical concept and scope of this disclosure as understood by a person with ordinary skill in the art to which this disclosure pertains. Furthermore, such substitutions, modifications, and alterations should be considered to fall within the scope of the attached claims.

Claims

1. Top surface; The lower surface opposite the upper surface; A first side surface and a second side surface connecting the upper surface and the lower surface; Mounting holes penetrating the upper surface and the lower surface; A first cutting edge formed on the edge of the upper surface that meets the first side surface; A second cutting edge formed on the edge of the upper surface that meets the second side surface; and Including first corner portions and second corner portions provided at both ends of the upper surface where the first side and the second side meet, The lower surface comprises a ridge portion and a first inclined surface and a second inclined surface located on both sides of the ridge portion, respectively. When viewed from the lower surface, the first inclined surface and the second inclined surface have an asymmetrical shape with respect to the ridge portion, and each of the first inclined surface and the second inclined surface is formed to incline upward as it moves away from the ridge portion.

2. The first cutting edge includes a peripheral edge that extends in a curved shape from the first corner and a long edge that is connected to the peripheral edge and extends to the second corner. The second cutting edge includes a center edge that extends in a curved shape from the second corner portion, and a short edge that is connected to the center edge and extends to the first corner portion. The cutting insert according to claim 1, wherein the straight-line distance between both sides of the long edge is longer than the straight-line distance between both sides of the short edge.

3. The cutting insert according to claim 2, wherein each of the long edge and the short edge has a linear shape.

4. The cutting insert according to claim 2, wherein, when viewed from the lower surface, the ridge portion is separated from the second corner portion, inclined with respect to a virtual line connecting the point where the peripheral edge and the long edge meet with the second corner portion, and crosses the mounting hole.

5. The cutting insert according to claim 2, wherein, when viewed from the lower surface, the ridge portion is formed to extend from the edge of the lower surface adjacent to the long edge to the edge of the lower surface adjacent to the short edge.

6. The cutting insert according to claim 1, wherein the ridge portion is formed in a surface shape having a set width between the first inclined surface and the second inclined surface.

7. The cutting insert according to claim 1, wherein the ridge portion is formed in a linear shape where the first inclined surface and the second inclined surface meet.

8. The cutting insert according to claim 1, wherein the first inclined surface and the second inclined surface are each inclined to an angle of inclination within the range of 5° to 30° with respect to a reference line that is perpendicular to a central axis passing through the center of the mounting hole and extending in the direction of extension of the mounting hole.

9. The upper surface includes a center surface in which the mounting hole is formed, a land surface formed along the first cutting edge and the second cutting edge, and a rake surface formed between the center surface and the land surface. The cutting insert according to any one of claims 1 to 8, wherein, when the cutting insert is viewed from the side, the first corner portion and the second corner portion are each raised above the center surface.

10. It is a rotary cutting tool used for milling workpieces. A cylindrical tool body with two rows of spiral flutes formed at the longitudinal end; A pair of cutting inserts that are interchangeably mounted on the tool body; and Includes a pair of screws for securing each of the pair of cutting inserts to the tool body, Each of the pair of cutting inserts is Top surface; Opposite the upper surface, the lower surface comprises a first inclined surface and a second inclined surface located on both sides of the ridge portion and the boundary of the ridge portion, and having an asymmetrical shape with respect to the ridge portion, wherein each of the first and second inclined surfaces is formed to incline upward as it moves away from the ridge portion; A first side surface and a second side surface connecting the upper surface and the lower surface; Mounting holes formed to penetrate the upper and lower surfaces, into which the pair of screws are each fitted; First corner portion and second corner portion provided at both ends of the upper surface where the first side and the second side meet; A first cutting edge formed between the first side surface and the top surface, including a peripheral edge that extends in a curved shape from the first corner portion; and It includes a second cutting edge formed between the second side surface and the upper surface, and including a center edge that extends in a curved shape from the second corner portion, Each of the two rows of spiral flutes has a first insert pocket and a second insert pocket formed therein for accommodating each of the pair of cutting inserts. The pair of cutting inserts includes a first cutting insert that is mounted in the first insert pocket such that the first corner portion is located axially forward of the tip of the tool body, and the peripheral edge of the first cutting insert is located radially outward of the tool body and axially forward of the tool body compared to the center edge. The pair of cutting inserts includes a second cutting insert that is mounted in the second insert pocket such that the second corner portion is located axially forward of the tool body, and the center edge of the second cutting insert is located radially outward of the tool body and axially forward of the tool body than the peripheral edge. Rotary cutting tool.

11. When the first cutting insert is viewed from the side, the lower surface of the first cutting insert has a V-shape, and the first insert pocket comprises a first bottom surface that supports the lower surface of the first cutting insert, and a first side wall that extends from the inside of the first bottom surface in a radially outward direction of the tool body and supports the second side surface of the first cutting insert, When the second cutting insert is viewed from the side, the lower surface of the second cutting insert has a V-shape, and the second insert pocket comprises a second bottom surface that supports the lower surface of the second cutting insert, and a second side wall that extends from the inside of the second bottom surface in a radially outward direction of the tool body and supports the first side surface of the second cutting insert. The rotary cutting tool according to claim 10.

12. The first bottom surface includes a first outer bottom surface that contacts the first inclined surface adjacent to the peripheral edge of the first cutting insert, a first inner bottom surface that contacts the second inclined surface adjacent to the center edge of the first cutting insert, and a first ridge-receiving groove formed between the first outer bottom surface and the first inner bottom surface for accommodating the ridge portion of the first cutting insert. The rotary cutting tool according to claim 11, wherein the second bottom surface includes a second inner bottom surface that contacts the first inclined surface adjacent to the peripheral edge of the second cutting insert, a second outer bottom surface that contacts the second inclined surface adjacent to the center edge of the second cutting insert, and a second ridge-receiving groove formed between the second inner bottom surface and the second outer bottom surface to accommodate the ridge portion of the second cutting insert.

13. The rotary cutting tool is a ball nose end mill, according to any one of claims 10 to 12.

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