End mill

Abstract

To provide an end mill configured so that strength of a cutting blade can be enhanced to extend tool life, while securing edge and suppressing burr from occurring.SOLUTION: A body 3 has: a chip ejection groove 4 extending spirally toward the opposite side of a rotating direction of an end mill as going from a tip surface toward a rear end of the body 3; a rake face 5; a bottom blade 71; an outer peripheral blade 72; and a sharp corner part 8 arranged in a connection part between the bottom blade 71 and the outer peripheral blade 72. In a side view in which the body 3 is viewed from a radial direction that is orthogonal to a center shaft, a torsional angle formed by the outer peripheral blade 72 and the center shaft crossing each other is 45° or more and 55° or less, and a rake angle of the outer peripheral blade 72 is -10° or more and -2° or less. The rake face 5 has an outer peripheral rake face 51 that is connected to the outer peripheral blade 72, the corner part 8 and an outer end part 71b in a radial direction of the bottom blade 71, and a tip rake face 52 that is connected to a part 71a other than the outer end part in the radial direction of the bottom blade 71, where the tip rake face 52 is arranged away from the outer peripheral blade 72.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an end mill. [Background technology]

[0002] Conventionally, there is known an end mill having a body (cutting edge portion) extending axially along a central axis and a shank connected to a rear end portion of the body. When a workpiece is cut using an end mill, burrs may be generated at the machined portion. If burrs are generated, a process of removing the burrs manually or the like is required in a later process, which is not preferable.

[0003] In the burr-suppressing end mill described in Patent Document 1, the rake angle (radial rake angle) of the peripheral cutting edge is set to a positive angle (positive angle) of 5° or more to ensure sharpness and suppress the generation of burrs. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-27595 A Summary of the Invention [Problem to be solved by the invention]

[0005] In this type of end mill, if the rake angle of the peripheral cutting edge is simply set to a positive angle to ensure sharpness and suppress burrs, the strength of the cutting edge decreases. This causes the peripheral cutting edge to wear out or break prematurely, resulting in the end of its tool life. It is particularly difficult to suppress burrs while extending the tool life in small diameter end mills.

[0006] An object of the present invention is to provide an end mill that can ensure sharpness and suppress the generation of burrs, while increasing cutting edge strength and extending tool life. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides the following means.

[0008] [First aspect of the present invention] The cutting tool has a body extending in the axial direction along a central axis, the body having a chip discharge groove extending in a spiral shape in a direction opposite to the end mill rotation direction around the central axis as it moves from the front end surface of the body toward the rear end side, a rake face disposed on a wall surface of the chip discharge groove facing the end mill rotation direction, a bottom blade disposed on a ridge portion connecting the rake face and the front end surface of the body, a peripheral blade disposed on a ridge portion connecting the rake face and the outer peripheral surface of the body, and a sharp edge disposed on a connection portion between the bottom blade and the peripheral blade. an outer rake surface connected to the outer blade, the corner portion, and the radial outer end portion of the bottom blade, and a tip rake surface connected to a portion of the bottom blade other than the radial outer end portion, the tip rake surface being positioned away from the outer blade, wherein, in a side view of the body seen from a radial direction perpendicular to the central axis, a twist angle formed by the intersection of the outer rake surface and the central axis is 45° or more and 55° or less, and a rake angle of the outer rake surface is -10° or more and -2° or less, and the rake surface has an outer rake surface connected to the outer rake surface, the corner portion, and the radial outer end portion of the bottom blade, and a tip rake surface connected to a portion of the bottom blade other than the radial outer end portion, and the tip rake surface is positioned away from the outer rake surface.

[0009] [Aspect 2 of the present invention] The end mill according to aspect 1, wherein the distance from the intersection of the boundary line between the tip rake face and the peripheral rake face and the bottom cutting edge to the corner is 30% or less of the cutting edge diameter dimension of the body.

[0010] [Embodiment 3 of the present invention] 3. The end mill according to claim 1 or 2, wherein the blade diameter dimension of the body is 4 mm or less.

[0011] [Embodiment 4 of the present invention] An end mill according to any one of aspects 1 to 3, wherein when the tip cutting face is viewed from the front in the direction of rotation of the end mill, the bottom cutting edge extends linearly over its entire length.

[0012] [Embodiment 5 of the present invention] An end mill described in any one of aspects 1 to 4, wherein a plurality of cutting edges including the bottom blade and the outer blade are provided on the body, and the plurality of cutting edges are arranged at an uneven pitch around the central axis. Effect of the Invention

[0013] According to the end mill of the above aspect of the present invention, it is possible to ensure sharpness and suppress the generation of burrs, while increasing the cutting edge strength and extending the tool life. [Brief description of the drawings]

[0014] [Figure 1] 1 is a side view showing an end mill according to an embodiment of the present invention, a portion of which is shown in a simplified cross-sectional view. [Diagram 2] FIG. 2 is a front view of the end mill of the embodiment of the present invention as viewed from the tip side in the axial direction. [Diagram 3] 1 is a side view of a body tip portion of an end mill according to one embodiment of the present invention, viewed from the rotation direction of the end mill. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] An end mill 1 according to an embodiment of the present invention will be described with reference to the drawings. The end mill 1 according to the present embodiment is a cutting tool (turning tool) that performs milling (turning) on ​​a workpiece such as a metal. Specifically, the end mill 1 according to the present embodiment is a square end mill.

[0016] As shown in FIG. 1, the end mill 1 is columnar about a central axis C. The end mill 1 includes a shank 2 and a body 3. The body 3 may also be referred to as a cutting edge portion or a blade portion. The diameter dimension of the body 3, that is, the blade diameter dimension, is, for example, 4 mm or less. The blade diameter dimension of the body 3 may be 3 mm or less, or may be 2 mm or less. Since the blade diameter dimension of the body 3 is small as described above, the end mill 1 of this embodiment may also be referred to as a small diameter end mill.

[0017] The shank 2 and the body 3 are arranged coaxially with each other, with the central axis C being a common axis. Moreover, the shank 2 and the body 3 are disposed at different positions in the direction in which the central axis C extends.

[0018] In this embodiment, the direction in which the central axis C of the end mill 1 extends is referred to as the axial direction. Within the axial direction, the direction from the shank 2 to the body 3 is referred to as the axial tip side or simply the tip side, and the direction from the body 3 to the shank 2 is referred to as the axial rear end side or simply the rear end side.

[0019] The direction perpendicular to the central axis C is called the radial direction. Within the radial direction, the direction approaching the central axis C is called the radially inner direction, and the direction away from the central axis C is called the radially outer direction. The direction rotating around the central axis C is called the circumferential direction. Among the circumferential directions, the direction in which the end mill 1 is rotated during cutting is called the end mill rotation direction T, and the opposite rotation direction is called the side opposite to the end mill rotation direction T, or the counter end mill rotation direction (see Figure 2).

[0020] As shown in Fig. 1, the shank 2 is cylindrical and extends axially about a central axis C. The shank 2 is connected to the rear end of the body 3. In this embodiment, the outer diameter of the shank 2 is larger than the outer diameter (blade diameter) of the body 3. The tip of the shank 2 connected to the body 3 is tapered such that the outer diameter decreases toward the tip.

[0021] The shank 2 is detachably held on a spindle or the like of a machine tool (not shown in the figure) (hereinafter, may be abbreviated to the spindle or the like). The shank 2 is rotated in the end mill rotation direction T by the spindle or the like, while being moved in the radial and axial directions relative to a workpiece (not shown in the figure). As a result, the end mill 1 cuts into the workpiece with cutting edges 7 (bottom cutting edge 71 and peripheral cutting edge 72) of the body 3 (described later) to perform various milling processes. The blade diameter dimension of the body 3 described above corresponds to the diameter dimension (outer diameter dimension) of the cutting edges 7.

[0022] The body 3 has a generally cylindrical shape extending in the axial direction along a central axis C. As shown in FIGS.

[0023] The chip discharge groove 4 is a groove that opens to a leading end surface 3a facing the leading end side in the axial direction of the body 3 and to an outer peripheral surface 3b facing radially outward. As it moves from the leading end surface 3a of the body 3 toward the rear end side, the chip discharge groove 4 extends in a spiral shape in the opposite direction to the end mill rotation direction T around the central axis C. Note that the shape of the chip discharge groove 4 is shown in a simplified form in the cross-sectional view (longitudinal cross-sectional view) partially shown in FIG. 1.

[0024] A plurality of chip discharge grooves 4 are provided at intervals in the circumferential direction on the body 3. In this embodiment, three chip discharge grooves 4 are provided at uneven pitches in the circumferential direction. The number of chip discharge grooves 4 is not limited to three, and may be two or less or four or more. The number of each of the rake faces 5, flank faces 6, cutting edges 7 and corner portions 8, which will be described later, is the same as the number of the chip discharge grooves 4.

[0025] The chip discharge groove 4 has a gash 9 arranged at the tip of the chip discharge groove 4. The gash 9 constitutes a part (tip) of the chip discharge groove 4. Therefore, the number of gashes 9 is the same as the number of chip discharge grooves 4. The gash 9 is a groove recessed from the tip surface 3a of the body 3 toward the rear end side, and extends roughly along the radial direction. The radial inner end of the gash 9 is arranged closer to the central axis C than the part of the chip discharge groove 4 other than the gash 9.

[0026] The rake face 5 is disposed on a wall surface of the chip discharge groove 4 facing the end mill rotation direction T. As shown in FIG.

[0027] The outer circumferential rake face 51 is disposed at the radially outer end of the wall surface (rake face 5) of the chip discharge groove 4 facing the end mill rotation direction T. The outer circumferential rake face 51 extends spirally along the extension direction of the chip discharge groove 4.

[0028] The tip rake face 52 is disposed at the tip of the wall surface (rake face 5) of the chip discharge groove 4 facing the end mill rotation direction T. The tip rake face 52 is disposed radially inward from the outer circumferential rake face 51. The outer circumferential rake face 51 and the tip rake face 52 are disposed adjacent to each other in the radial direction. That is, the radial outer end of the tip rake face 52 is connected to the radial inner end of the outer circumferential rake face 51. The tip rake face 52 is disposed on the wall surface facing the end mill rotation direction T of the gash 9. For this reason, the tip rake face 52 may be referred to as a gash rake face or the like.

[0029] Reference numeral 53 in Fig. 3 denotes a boundary line between the outer peripheral rake face 51 and the tip rake face 52. The boundary line 53 extends radially outward (lower in Fig. 3) as it approaches the tip side in the axial direction (left side in Fig. 3). In the illustrated example, the boundary line 53 forms a curved line that is convex radially inward (upper side in Fig. 3). The tip of the boundary line 53 reaches a bottom edge 71 of the cutting edge 7, which will be described later.

[0030] As shown in FIG. 2, the flank 6 has a front end flank 61 arranged on the front end surface 3a of the body 3 and an outer circumferential flank 62 arranged on the outer circumferential surface 3b of the body 3.

[0031] The tip flank 61 is disposed between adjacent chip discharge grooves 4 (gash 9) in the circumferential direction on the tip face 3a of the body 3. The tip flank 61 is connected to a bottom edge 71 (described later) of the cutting edge 7 and extends along the bottom edge 71. The tip flank 61 extends toward the rear end in the axial direction as it moves away from the bottom edge 71 toward the opposite side to the end mill rotation direction T. This provides the tip flank 61 with a clearance angle.

[0032] The outer circumferential flank 62 is disposed between adjacent chip discharge grooves 4 on the outer circumferential surface 3b of the body 3. The outer circumferential flank 62 is connected to a peripheral cutting edge 72 (described later) of the cutting edge 7, and extends along the peripheral cutting edge 72. The outer circumferential flank 62 extends radially inward from the peripheral cutting edge 72 toward the opposite side to the end mill rotation direction T. This provides the outer circumferential flank 62 with a clearance angle.

[0033] 1 to 3, the cutting edge 7 has a bottom edge 71 arranged on a ridge portion where the rake face 5 and the tip surface 3a of the body 3 are connected, and a peripheral edge 72 arranged on a ridge portion where the rake face 5 and the outer peripheral surface 3b of the body 3 are connected.

[0034] As shown in FIG. 2, in this embodiment, a plurality of cutting edges 7 (a set of cutting edges 7) including a bottom edge 71 and a peripheral edge 72 are provided on the body 3. The plurality of cutting edges 7 are arranged at unequal pitches in the circumferential direction around the central axis C. In this embodiment, three cutting edges 7 are provided on the body 3. That is, the end mill 1 is a three-blade end mill. The number of cutting edges 7 is not limited to three, and may be two or less or four or more.

[0035] The bottom blade 71 extends in a substantially radial direction along the extension direction of the gash 9. As the bottom blade 71 extends radially inward, it extends slightly axially toward the rear end side. The bottom blade 71 may extend along a virtual plane perpendicular to the central axis C.

[0036] The bottom blades 71 include at least one long bottom blade and at least one short bottom blade having a blade length shorter than that of the long bottom blade. Specifically, in this embodiment, one long bottom blade and two short bottom blades are provided. The blade length of the long bottom blade is longer than 1 / 2 the blade diameter dimension (diameter dimension) of the body 3 (i.e., the radial dimension of the body 3). The blade length of the short bottom blade is shorter than 1 / 2 the blade diameter dimension of the body 3.

[0037] As shown in FIG. 3, when the leading rake face 52 is viewed from the front in the end mill rotation direction T, each bottom blade 71 (long bottom blade and short bottom blade) extends linearly over its entire length.

[0038] The portion 71a of the bottom cutting edge 71 other than the radially outer end portion is disposed on the ridge portion where the tip rake face 52 and the tip flank face 61 are connected. Also, the radially outer end portion 71b of the bottom cutting edge 71 is disposed on the ridge portion where the outer peripheral rake face 51 and the tip flank face 61 are connected.

[0039] As shown in Fig. 1, the peripheral cutting edge 72 extends along the chip discharge groove 4. Specifically, the peripheral cutting edge 72 extends twistedly in the direction opposite to the end mill rotation direction toward the rear end side in the axial direction, forming a spiral shape centered on the central axis C. The peripheral cutting edge 72 is disposed on the ridge where the peripheral rake face 51 and the peripheral flank face 62 are connected. As shown in Fig. 3, the tip rake face 52 is disposed radially inwardly away from the peripheral cutting edge 72.

[0040] 1, in a side view of the body 3 seen from a radial direction perpendicular to the central axis C, the angle formed by the intersection of the peripheral cutting edge 72 and the central axis C, i.e., the helix angle θ, is 45° or more and 55° or less. More preferably, the helix angle θ is 50° or more.

[0041] The rake angle α of the peripheral cutting edge 72 is a negative angle, specifically, -10° or more and -2° or less (see FIG. 2). In this embodiment, the "rake angle α of the peripheral cutting edge 72" refers to the radial rake angle (radial rake) of the peripheral cutting edge 72. More specifically, the rake angle α of the peripheral cutting edge 72 is the angle formed between a virtual straight line VL passing through the cutting edge of the peripheral cutting edge 72 and the central axis C, and the rake face 5 (peripheral rake face 51) adjacent to the peripheral cutting edge 72 in a cross-sectional view (transverse cross-sectional view) perpendicular to the central axis C of the body 3.

[0042] As shown in Fig. 3, the corner 8 is disposed at the connection between the bottom cutting edge 71 and the peripheral cutting edge 72. Specifically, the corner 8 is located at the connection between the radial outer end of the bottom cutting edge 71 and the axial tip of the peripheral cutting edge 72. The corner 8 is sharpened toward the tip outer periphery. The distance from the intersection P between the boundary line 53 between the tip rake face 52 and the peripheral rake face 51 and the bottom cutting edge 71 to the corner 8 is 30% or less of the blade diameter dimension of the body 3.

[0043] The outer rake surface 51 is connected to the outer rake blade 72, the corner 8, and the radial outer end 71b of the bottom blade 71. That is, the outer rake surface 51 constitutes the rake surfaces of the outer rake blade 72, the corner 8, and the radial outer end 71b of the bottom blade 71. The tip rake surface 52 is connected to the portion 71a of the bottom blade 71 other than the radial outer end. That is, the tip rake surface 52 constitutes the rake surface of the portion 71a of the bottom blade 71 other than the radial outer end.

[0044] In the end mill 1 of the present embodiment described above, the rake angle α of the peripheral cutting edge 72 is a negative angle of -10° or more and -2° or less, which increases the cutting edge strength of the peripheral cutting edge 72 and suppresses wear and chipping.

[0045] However, simply making the rake angle α of the peripheral cutting edge 72 a negative angle may impair the cutting quality. Therefore, in the end mill 1 of this embodiment, the twist angle θ of the peripheral cutting edge 72 is set to a large value of 45° or more and 55° or less. This improves the cutting quality of the peripheral cutting edge 72 and suppresses the generation of burrs.

[0046] In addition, the tip rake face 52 does not reach the peripheral cutting edge 72, and the rake face of the pointed corner 8 connecting the bottom cutting edge 71 and the peripheral cutting edge 72 is formed by the peripheral rake face 51. Such corner 8 also enhances the sharpness of the cutting edge 7, suppressing the generation of burrs. The corner 8 in this embodiment may be referred to as a "pin-edge" or the like.

[0047] As described above, according to this embodiment, it is possible to ensure sharpness and suppress the occurrence of burrs, while increasing the cutting edge strength and extending the tool life.

[0048] Here, each numerical range of this embodiment will be described in detail. When the rake angle α of the peripheral cutting edge 72 is -10° or more, defects such as a significant loss of the sharpness of the peripheral cutting edge 72 are suppressed, and the occurrence of burrs is stably suppressed. Also, when the rake angle α of the peripheral cutting edge 72 is -2° or less, the cutting edge angle of the peripheral cutting edge 72 can be stably secured large, and the cutting edge strength is increased.

[0049] Furthermore, when the twist angle θ of the peripheral cutting edge 72 is 45° or more, the sharpness of the peripheral cutting edge 72 is stably improved. When the twist angle θ of the peripheral cutting edge 72 is 55° or less, the generation of a large thrust force (force acting in the axial direction) during cutting is suppressed, and chatter vibrations and the like are suppressed, so that the machining surface accuracy is maintained well.

[0050] Although not shown, the end mill 1 of this embodiment can significantly suppress the occurrence of burrs, for example, when cutting a workpiece in a reciprocating manner along the extension direction of the groove. Specifically, in the reciprocating cutting and finishing of a groove, if the cutting edge is worn during down-cutting at the time of entering the return path compared to the outward path of the groove, burrs tend to be more likely to be generated. In this regard, the end mill 1 of this embodiment ensures the cutting edge strength of the peripheral cutting edge 72, making it less susceptible to wear and chipping, and has improved sharpness, so that it is possible to stably suppress the occurrence of burrs even in the reciprocating cutting and finishing of a groove.

[0051] In this embodiment, the distance from an intersection P between the boundary line 53 between the leading rake face 52 and the outer circumferential rake face 51 and the bottom cutting edge 71 to the corner 8 is 30% or less of the cutting edge diameter of the body 3. When the distance is 30% or less of the blade diameter dimension of the body 3, the thickness of the cutting edge 7 can be sufficiently ensured, so that chipping during cutting can be suppressed.

[0052] In this embodiment, the blade diameter of the body 3 is 4 mm or less. In conventional end mills, it is more difficult to suppress burrs while extending the tool life as the cutting edge diameter becomes smaller. On the other hand, according to the present embodiment, the above-mentioned effects are stably achieved even when applied to a small-diameter end mill in which the cutting edge diameter of the body 3 is reduced to 4 mm or less. The cutting edge diameter of the body 3 is preferably 3 mm or less, more preferably 2 mm or less.

[0053] In this embodiment, as shown in FIG. 3, when the leading rake face 52 is viewed from the front in the end mill rotation direction T, the bottom cutting edge 71 extends linearly over its entire length. Unlike the present embodiment, for example, compared to a case where a bent or curved portion is formed on the bottom blade, the above-mentioned configuration of the present embodiment suppresses a large cutting resistance acting locally on the bottom blade 71 during cutting. Therefore, the cutting edge strength of the bottom blade 71 is stably increased.

[0054] In this embodiment, a plurality of cutting edges 7 including a bottom edge 71 and a peripheral edge 72 are provided on the body 3, and the plurality of cutting edges 7 are arranged around the central axis C at unequal pitches. In this case, since the cutting edges 7 are arranged at unequal pitches around the central axis C, it is possible to suppress the occurrence of chatter vibrations due to resonance during cutting. According to this embodiment, it is possible to stably perform high-precision cutting.

[0055] The present invention is not limited to the above-described embodiment, and the addition, omission, substitution, and other modifications of the configuration are possible without departing from the spirit of the present invention. The present invention is not limited to the above-described embodiment, and is limited only by the claims. EXAMPLES

[0056] The present invention will be described in more detail below with reference to examples, although the present invention is not limited to these examples.

[0057] <Cutting Verification Test> As Example 1 of the present invention, a milling test of a workpiece was performed using the end mill 1 of the above-mentioned embodiment. In addition, end mills different from the embodiment in at least one of the components of the helix angle θ (45° to 55°), the rake angle α (-10° to -2°), and the pin corner (the sharp corner 8 with the outer peripheral rake face 51 as the rake face) were prepared as Comparative Examples 1 to 6, and the workpiece was milled under the same conditions as Example 1.

[0058] The cutting conditions were as follows: Rotation speed: 10000min -1 ·Cutting speed Vc:41m / min Feed speed Vf: 500mm / min Feed per tooth: 0.017mm / t Coolant: Non-water-soluble coolant ·Work material: SUS440C equivalent

[0059] Then, in Example 1 and Comparative Examples 1 to 6, a reciprocating finish machining was performed on the workpiece to form a groove shape, and the presence or absence of burrs on the groove side surface was confirmed. Similarly, the cutting distance from the start of cutting to the end of the tool life was confirmed. The results are shown in Table 1.

[0060] [Table 1]

[0061] As shown in Table 1, in Example 1 of the present invention, no burrs were observed on the groove side surface after cutting, and cutting was possible even after 5 m of cutting. On the other hand, in Comparative Examples 1 to 4 and 6, burrs were observed on the groove side surface after cutting, and all of Comparative Examples 1 to 6 reached the end of their tool life before the cutting distance reached 4 m.

[0062] From the above results, it was confirmed that the end mill 1 of Example 1 of the present invention can enhance the cutting edge strength and extend the tool life while ensuring sharpness and suppressing the generation of burrs. In addition, the test results showed that when a pin edge is provided, it tends to be easier to suppress the generation of initial burrs (burrs that occur at the beginning of cutting). It was also found that increasing the helix angle θ improves the sharpness and makes it easier to suppress the generation of burrs (particularly burrs other than initial burrs). [Industrial Applicability]

[0063] INDUSTRIAL APPLICABILITY The end mill of the present invention can ensure sharpness and suppress the generation of burrs, while increasing the cutting edge strength and extending the tool life, and therefore has industrial applicability. [Explanation of symbols]

[0064] 1...end mill, 3...body, 3a...tip surface, 3b...peripheral surface, 4...chip discharge groove, 5...rake surface, 7...cutting edge, 8...corner, 51...peripheral rake surface, 52...tip rake surface, 53...boundary line, 71...bottom edge, 71a...portion of bottom edge other than radial outer end, 71b...radial outer end of bottom edge, 72...peripheral edge, C...center axis, P...intersection, T...end mill rotation direction, α...rake angle of peripheral edge, θ...twist angle

Claims

1. A body extending axially along a central axis, The body includes: a chip discharge groove extending in a spiral shape around the central axis in a direction opposite to a rotation direction of the end mill as the chip discharge groove moves from the front end surface of the body toward the rear end side; A rake face is disposed on a wall surface of the chip discharge groove facing the rotation direction of the end mill; a bottom cutting edge disposed on a ridge portion where the rake face and the tip surface of the body are connected; a peripheral cutting edge disposed on a ridge portion where the rake face and the outer peripheral surface of the body are connected; A sharp corner portion is disposed at a connection portion between the bottom cutting edge and the peripheral cutting edge, When the body is viewed from a side in a radial direction perpendicular to the central axis, a twist angle formed by an intersection of the peripheral cutting edge and the central axis is 45° or more and 55° or less, The rake angle of the peripheral cutting edge is -10° or more and -2° or less, The rake face is an outer rake surface connected to the radially outer end portions of the outer cutting edge, the corner portion, and the bottom cutting edge; a tip rake face connected to a portion of the bottom cutting edge other than the radially outer end portion, The tip rake face is disposed away from the peripheral cutting edge. End mill.

2. A distance from an intersection of a boundary line between the tip rake face and the peripheral rake face and the bottom cutting edge to the corner is 30% or less of a cutting edge diameter dimension of the body. The end mill according to claim 1 .

3. The blade diameter of the body is 4 mm or less. The end mill according to claim 1 or 2.

4. When the tip rake face is viewed from the front in the direction of rotation of the end mill, the bottom cutting edge extends linearly over its entire length. The end mill according to claim 1 or 2.

5. A plurality of cutting edges including the end cutting edge and the outer peripheral cutting edge are provided on the body, The cutting edges are arranged at unequal pitches around the central axis. The end mill according to claim 1 or 2.

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