WO2019188135A1

WO2019188135A1 - End mill main body and end mill

Info

Publication number: WO2019188135A1
Application number: PCT/JP2019/009441
Authority: WO
Inventors: 修介北川
Original assignee: 日本特殊陶業株式会社
Priority date: 2018-03-27
Filing date: 2019-03-08
Publication date: 2019-10-03
Also published as: JPWO2019188135A1; JP7341058B2

Abstract

Provided is an end mill main body with which highly efficient machining can be performed while damage is suppressed. The present disclosure relates to a ceramic end mill main body constituting a cutting edge portion of an end mill which rotates about an axis. This end mill main body is provided with a chip discharge groove provided at the outer periphery of a tip end portion in such a way as to twist rearward in the direction of rotation with increasing distance from a tip end side toward a rear end side, an outer peripheral cutting edge provided on an outer peripheral side ridge line of the chip discharge groove, and a chamfer surface provided at least in a part of the outer peripheral side ridge line where the chip discharge groove and a flank of the outer peripheral cutting edge intersect.

Description

End mill body and end mill

Cross-reference of related applications

This international application claims priority based on Japanese Patent Application No. 2018-060177 filed with the Japan Patent Office on March 27, 2018, and is based on Japanese Patent Application No. 2018-060177. The entire contents are incorporated by reference into this international application.

This disclosure relates to an end mill body and an end mill.

An end mill made of cemented carbide is known in which a corner blade projecting outward is formed between the bottom blade and the outer peripheral blade. In recent years, a ceramic end mill made of a material such as silicon nitride has been developed (see Patent Document 1).

In such a ceramic end mill, in order to suppress wear of the outer peripheral blade in high-speed cutting, an end mill having a negative angle on the radial rake of the outer peripheral blade has been devised (see Patent Document 2).

International Publication No. 2018/003948 JP 2016-159379 A

As described above, even if the radial rake of the outer peripheral blade is set to a negative angle, the strength of the outer peripheral blade may be insufficient. As a result, a defect may occur when the feed amount or cutting amount per blade is increased.

One aspect of the present disclosure preferably provides an end mill main body capable of cutting with high efficiency while suppressing defects.

One aspect of the present disclosure is a ceramic end mill body that constitutes a cutting edge portion of an end mill that is rotated around an axis. The end mill body includes a chip discharge groove, an outer peripheral blade, a gash, a bottom blade, a bottom rake surface, a corner blade, a corner rake surface, and a chamfer surface. The chip discharge groove is provided on the outer periphery of the front end portion so as to be twisted backward in the rotation direction from the front end side toward the rear end side. An outer peripheral blade is provided in the outer peripheral side ridgeline of a chip discharge groove. The gasche reaches the chip discharge groove from the top of the tip.

The bottom blade is provided at the top of the tip. The bottom rake face extends from the bottom blade toward the rear end side. The corner blade is provided so as to protrude outward from the bottom blade to the outer peripheral blade. The corner rake face is provided between the bottom rake face and the chip discharge groove so as to contact the corner blade. The chamfer surface is provided at an edge portion of the outer peripheral edge where at least the chip discharge groove intersects with the flank face of the outer peripheral blade.

According to such a configuration, the strength of the outer peripheral blade can be improved by providing the chamfer surface. As a result, high-efficiency cutting with a large feed amount and cutting amount per blade becomes possible while suppressing defects such as each blade and gash.

In one aspect of the present disclosure, the radial rake angle α of the chamfer surface at the outer peripheral edge line portion may be −30 ° to −15 °. According to such a configuration, it is possible to achieve both the strength of the outer peripheral blade and the machinability.

In one aspect of the present disclosure, the difference (β−α) obtained by subtracting the radial rake angle α from the radial rake angle β of the chip discharge groove may be 10 ° or more and 30 ° or less. According to such a configuration, it is possible to improve the machinability of the outer peripheral blade and promote the reduction of the cutting resistance.

In one aspect of the present disclosure, the chamfer surface may be provided on at least a part of a corner blade ridge line portion where a corner rake surface and a corner blade flank surface intersect. The radial rake angle γ of the chamfer surface at the corner edge line portion may be not less than −30 ° and not more than −15 °. According to such a configuration, high-efficiency cutting can be performed while more reliably suppressing defects such as blades and gashes.

In one aspect of the present disclosure, the chamfer surface may not be provided on the bottom blade. According to such a structure, it can suppress that the cutting efficiency in a bottom blade reduces by a chamfer surface.

In one aspect of the present disclosure, a corner having a radius of 0.5 mm or more and 2 mm or less may be attached to the corner portion that is the most spaced from the bottom blade in the gasche. According to such a structure, the defect | deletion which started from the corner | angular part of a gash can be suppressed. As a result, the cutting efficiency can be further increased.

One aspect of the present disclosure can be suitably used as an end mill body constituting a cutting edge portion of a radius end mill.

Another aspect of the present disclosure is an end mill that includes the end mill body and a shank portion that is attached to a rear end portion of the end mill body and is configured to be fixed to a rotating shaft of a machine tool. According to such a configuration, it is possible to obtain an end mill capable of cutting with high efficiency while suppressing defects such as blades and gashes.

In one aspect of the present disclosure, the shank portion may be made of ceramic. The end mill main body and the shank portion may be integrally formed. According to such a configuration, the weight of the end mill can be reduced.

In one aspect of the present disclosure, the end mill main body may have a connection portion configured such that the shank portion is detachably connected. According to such a configuration, it is possible to easily replace only the end mill body.

It is a typical side view showing an end mill of an embodiment. It is the elements on larger scale of the cutting-blade part in the end mill of FIG. 3A is a partially enlarged view showing a gash according to an embodiment different from that in FIG. 1, and FIG. 3B is a partially enlarged view showing a gash according to an embodiment different from those shown in FIGS. 1 and 3A. 4A is a schematic cross-sectional view taken along line IVA-IVA in FIG. 2, and FIG. 4B is a schematic cross-sectional view partially enlarged from FIG. 4A. FIG. 5 is a schematic partial enlarged sectional view taken along line VV in FIG. 2. It is a typical side view which shows the end mill of embodiment different from FIG. It is a schematic diagram which shows the cutting state in the test in an Example.

DESCRIPTION OF SYMBOLS 1 ... End mill, 3 ... End mill main body, 5 ... Shank part, 7 ... Tip part, 9 ... Chip discharge groove, 13 ... Outer peripheral blade, 13A ... Flank, 13B ... Outer edge ridgeline part, 15 ... Outer rake face, 17 ... Gash, 17A ... Corner, 19 ... Bottom rake face, 21 ... Bottom edge, 23 ... Corner edge, 23A ... Relief face, 23B ... Corner edge line part, 27 ... Corner rake face, 30 ... Chamfer face, 41 ... End mill 43 ... End mill main body, 44 ... Connection part, 44A ... Base part, 44B ... Screw part, 44C ... Recess, 45 ... Shank part, 45A ... Screw hole, 47 ... Projection part.

Hereinafter, embodiments to which the present disclosure is applied will be described with reference to the drawings.

[1. First Embodiment]
[1-1. Constitution]
The end mill 1 shown in FIG. 1 is a tool for cutting a metal member by being rotated around an axis O.

In the present embodiment, the end mill 1 is a radius end mill in which the top portion (that is, the bottom surface) of the cutting edge portion provided at the tip is planar and the corner of the cutting edge portion is rounded. That is, the end mill body 3 constitutes a cutting edge portion of a radius end mill.

The end mill 1 includes an end mill main body 3 and a shank portion 5. The end mill 1 is fed in a direction perpendicular to the axis O while rotating in the direction K about the axis O by a machine tool (not shown) to which the shank portion 5 is attached. ).

<End mill body>
As shown in FIG. 1, the end mill main body 3 constitutes a cutting edge provided at the tip of the end mill 1.

The end mill body 3 is made of ceramic. Here, “made of ceramic” means that a material containing ceramic as a main component, that is, containing 50 volume% or more (preferably 90 volume% or more) of ceramic. Examples of the ceramic constituting the end mill body 3 include silicon nitride, sialon, alumina, and zirconia.

The end mill body 3 includes a chip discharge groove 9, an outer peripheral blade 13, an outer peripheral rake surface 15, a gash 17, a bottom blade 21, a bottom rake surface 19, a corner blade 23, a corner rake surface 27, and a chamfer. Surface 30 (see FIG. 2).

(Chip discharge groove)
The chip discharge groove 9 is provided on the outer periphery of the front end portion 7 of the end mill body 3 so as to be twisted backward in the rotation direction from the front end side toward the rear end side.

The chip discharge groove 9 is a so-called blade groove or flute. In the present embodiment, four strip discharge grooves 9 are provided at equal intervals in the circumferential direction. However, the number of the chip discharge grooves 9 is not limited to four.

(Peripheral blade)
The outer peripheral blade 13 is provided on the outer peripheral side ridge line of the chip discharge groove 9. Specifically, the outer peripheral blade 13 is provided at the ridge line portion of the outer peripheral rake face 15 provided at the rear in the rotation direction of the chip discharge groove 9.

As with the chip discharge groove 9, the outer peripheral blade 13 is provided so as to be twisted toward the rear side in the rotational direction of the end mill body 3 from the front end side toward the rear end side. Further, the flank 13 </ b> A of the outer peripheral blade is an outer peripheral surface of the end mill body 3 that continues to the rear in the rotation direction of the outer peripheral rake surface 15.

(Gash)
The gash 17 reaches the chip discharge groove 9 from the top portion (that is, the bottom blade 21) of the tip end portion 7. That is, the gash 17 connects the chip discharge groove 9 and the bottom blade 21. The gash 17 is a region that is recessed toward the axis O from the chip discharge groove 9.

The corner (the upper right corner in FIG. 1) 17A farthest from the bottom blade 21 in the gash 17 is preferably provided with a roundness as shown in FIGS. 3A and 3B in order to avoid stress concentration. The radius of the roundness is preferably 0.5 mm or more and 2 mm or less. In other words, the corner portion 17A of the gasche 17 is preferably provided with a fillet portion having a minimum curvature of 0.5 mm or more.

The “roundness” does not mean a complete curved surface shape. For example, the shape is formed by connecting a plurality of fine steps to the corner portion 17A, and has a function substantially equivalent to roundness. It is a concept that also includes

By providing such roundness in the corner portion 17A, it is possible to suppress a defect starting from the corner portion 17A. As a result, the loss of the gasche 17 accompanying the increase in cutting resistance is suppressed, so that the cutting efficiency can be further increased.

(Bottom blade)
As shown in FIG. 1, the bottom blade 21 is provided on the top portion (that is, the bottom surface) of the distal end portion 7. The bottom blade 21 extends in the radial direction from the vicinity of the axis O.

The bottom rake face 19 extends in the direction from the bottom blade 21 toward the rear end side of the end mill body 3 (that is, the direction along the axis O). The bottom rake face 19 faces the front of the end mill body 3 in the rotational direction.

(Corner blade)
The corner blade 23 is provided so as to protrude outward from the end mill body 3 from the bottom blade 21 to the outer peripheral blade 13. In the present embodiment, the corner blade 23 has an arc shape.

Further, a corner rake face 27 is provided between the bottom rake face 19 and the chip discharge groove 9 so as to be in contact with the corner blade 23. The corner rake face 27 faces the front in the rotational direction of the end mill body 3.

(Chamfer side)
As shown in FIG. 2, the chamfer surface 30 is a concave curved surface provided at the outer peripheral edge ridge line portion 13 </ b> B where at least the chip discharge groove 9 and the flank 13 </ b> A of the outer peripheral edge 13 intersect. However, the chamfer surface 30 may be a curved surface other than the concave curved surface or a flat surface. The chamfer surface 30 faces forward in the rotational direction.

In the present embodiment, the chamfer surface 30 is provided on the entire outer peripheral edge ridge line portion 13B and a part of the corner edge ridge line portion 23B where the corner rake surface 27 and the flank 23A of the corner blade 23 intersect. Yes. Further, the chamfer surface 30 is not provided on the bottom blade 21.

Here, the intersection point B, the intersection point A between the corner blade 23 and the bottom blade 21, and the chamfer surface on a virtual plane including the axis O and passing through the intersection point B between one corner blade 23 and one outer peripheral blade 13 30 is projected onto a region Q1 that is sandwiched between a straight line P that passes through the point C and the intersection point B, and a straight line P that passes through the point C and the intersection point B. Surface 30 exists. On the other hand, the chamfer surface 30 does not exist in the region Q2 sandwiched between the straight line P and the line segment AC passing through the point C and the intersection A. Further, the corner rake face 27 exists only in the region Q1, and does not exist in the region Q2.

The point C is an intersection of a straight line passing through the intersection A and parallel to the axis O and a straight line passing through the intersection B and perpendicular to the axis O in the virtual plane. In the present embodiment, the corner blade 23 has an arc shape constituted by a part of a perfect circle, and therefore the point C coincides with the center of the corner blade 23. However, the corner blade 23 may be a part of an ellipse or a curved arc shape.

4A and 4B, the radial rake angle α of the chamfer surface 30 in the outer peripheral edge portion 13B is preferably −30 ° to −15 °, and more preferably −30 ° to less than −20 °. If the radial rake angle α is too small (that is, too large on the negative angle side), the machinability of the outer peripheral blade 13 may be reduced, and a large burr may occur during the cutting process. On the other hand, if the radial rake angle α is too large (that is, a negative angle or a positive angle close to zero), the outer peripheral blade 13 may be lost due to insufficient strength of the outer peripheral blade 13 under high-speed feeding or cutting conditions. There is.

Here, the “radial rake angle α” is defined by the chamfer surface 30 and the reference line D1 passing through the axis O and the outer peripheral edge 13 in the transverse section of the end mill body 3 (that is, the section orthogonal to the axis O). Among the angles, it is an acute angle.

The radial rake angle β of the chip discharge groove 9 is preferably -10 ° or more and 0 ° or less. If the radial rake angle β is too small (that is, too large on the negative angle side), the cutting performance of the outer peripheral blade 13 may be insufficient.

Here, the “radial rake angle β” is an angle formed by the reference line D1 and the outer peripheral rake face 15 in the rotational direction rearward of the chip discharge groove 9 adjacent to the chamfer surface 30 in the cross section of the end mill body 3. Among them, it is an acute angle.

Further, the difference (β−α) obtained by subtracting the radial rake angle α of the chamfer surface 30 from the radial rake angle β of the chip discharge groove 9 is preferably 10 ° or more and 30 ° or less. If the difference (β−α) is too small, there is a possibility that the effect of coexistence of the strength of the outer peripheral blade 13 and the machinability by the chamfer surface 30 may be insufficient. On the contrary, if the difference (β−α) is too large, the cutting performance of the outer peripheral blade 13 may be insufficient.

The width W of the chamfer surface 30 in the outer peripheral edge ridge line portion 13B is preferably 0.02 mm or more and 0.2 mm or less. However, it is preferable to change the width W of the chamfer surface 30 according to cutting conditions (for example, the feed amount per blade). The width W [mm] is preferably 1/2 or more and 2/3 or less of the feed amount [mm / t] per blade. For example, in processing with a feed amount of 0.04 mm / t, the width W is preferably 0.02 mm to 0.027 mm, and in processing with a feed amount of 0.3 mm / t, the width W is 0.15 mm to 0.2 mm. The following is preferred.

The radial rake angle γ of the chamfer surface 30 at the corner edge portion 23B shown in FIG. 5 is preferably −30 ° or more and −15 ° or less, and more preferably −30 ° or more and less than −20 °. If the radial rake angle γ is too small (that is, too large on the negative angle side), the cutting performance of the corner blade 23 becomes insufficient. On the other hand, if the radial rake angle γ is too large (that is, a negative angle or a positive angle close to zero), the strength of the corner blade 23 is insufficient and a defect may occur.

Here, the “radial rake angle γ” passes through the axis O and the corner blade 23 in a section perpendicular to the corner blade 23 of the end mill body 3 (that is, a section perpendicular to the chamfer surface 30 in the corner edge portion 23B). Of the angles formed by the reference line D2 and the chamfer surface 30, this is an acute angle.

The radial rake angle α and the radial rake angle γ may be the same angle or different angles.

Further, the width W of the chamfer surface 30 at the corner edge line portion 23B is the same as the range of the width W of the chamfer surface 30 at the outer edge edge line portion 13B. The two widths W may be the same value or different values.

<Shank part>
The shank part 5 is attached to the rear end part of the end mill main body 3 and is configured to be fixed to the rotating shaft of the machine tool. In the present embodiment, the shank portion 5 is made of ceramic and is made of the same material as the end mill body 3. Further, the shank portion 5 is configured integrally with the end mill body 3.

[1-2. effect]
According to the embodiment detailed above, the following effects can be obtained.

(1a) By providing the chamfer surface 30, the strength of the outer peripheral blade 13 can be improved. As a result, high-efficiency cutting with a large feed amount and cutting amount per blade becomes possible while suppressing the loss of each blade, the gasche 17 and the like.

(1b) Since the chamfer surface 30 is also provided on at least a part of the corner blade ridge line portion 23B, it is possible to perform cutting with high efficiency while more surely suppressing defects of each blade, the gasche 17 and the like.

(1c) Since the chamfer surface 30 is not provided on the bottom blade 21, it is possible to suppress a reduction in cutting efficiency in the bottom blade 21. As a result, the efficiency of the cutting process is increased while suppressing the chipping of the end mill body 3.

(1d) The end mill body 3 and the shank portion 5 are integrally formed of ceramic, so that the end mill 1 becomes a single ceramic part. Therefore, the weight reduction of the end mill 1 can be achieved.

[2. Second Embodiment]
[2-1. Constitution]
The end mill 41 shown in FIG. 6 is a tool for cutting a metal member by being rotated around the axis O. The end mill 41 includes an end mill main body 43 and a shank portion 45.

<End mill body>
The end mill main body 43 has a tip portion 7 and a connection portion 44. The tip 7 is the same as the end mill main body 3 of FIG.

The connecting portion 44 is configured such that the shank portion 45 is detachably connected. The connecting portion 44 is provided at the rear end portion of the end mill main body 43. The connection portion 44 includes a base portion 44A and a screw portion 44B protruding from the base portion 44A toward the rear end.

44 A of base parts have the recessed part 44C in the front end side of the end mill main body 43. As shown in FIG. A prismatic protrusion 47 provided at the rear end of the tip 7 is fitted in the recess 44C. The protruding portion 47 is joined to the base portion 44A by, for example, a brazing material.

<Shank part>
The shank portion 45 has a screw hole 45 </ b> A that is open at a connection portion with the end mill body 43. The screw portion 44B of the connection portion 44 is screwed into the screw hole 45A.

Therefore, the end mill main body 43 is attached to the shank portion 45 by screwing the screw portion 44B into the screw hole 45A. Further, the screw part 44B is detached from the shank part 45 by detachment from the screw hole 45A. Thus, the end mill main body 43 is configured as a replaceable head.

[2-2. effect]
According to the embodiment detailed above, the following effects can be obtained.

(2a) When wear or the like occurs in the end mill main body 43 with use in cutting, only the end mill main body 43 can be easily replaced.

[3. Other Embodiments]
As mentioned above, although embodiment of this indication was described, it cannot be overemphasized that this indication can take various forms, without being limited to the above-mentioned embodiment.

(3a) In the end mill body 3 of the above embodiment, the chamfer surface 30 does not necessarily have to be provided at the corner edge portion 23B where the corner rake surface 27 and the flank 23A of the corner blade 23 intersect. That is, the chamfer surface 30 may be provided only on the outer peripheral edge line portion 13B.

Conversely, the chamfer surface 30 may be provided on the entire corner edge portion 23B. Further, the chamfer surface 30 may be provided at a bottom edge portion where the bottom scoop surface 19 and the flank surface of the bottom edge 21 intersect. That is, the chamfer surface 30 may be formed from the outer peripheral edge line part 13B to the bottom edge line part.

(3b) The end mill body 3 of the above embodiment can be used for a ball end mill in addition to a radius end mill. That is, the end mill body 3 may constitute a cutting edge portion of a ball end mill.

(3c) The functions of one component in the above embodiment may be distributed as a plurality of components, or the functions of a plurality of components may be integrated into one component. Moreover, you may abbreviate | omit a part of structure of the said embodiment. In addition, at least a part of the configuration of the above embodiment may be added to or replaced with the configuration of the other embodiment. In addition, all the aspects included in the technical idea specified from the wording described in the claims are embodiments of the present disclosure.

[4. Example]
Below, the content of the test conducted in order to confirm the effect of this indication and its evaluation are demonstrated.

<Example 1-4>
An end mill body 3 having the shape shown in FIG. 1 (that is, having a chamfer surface) was produced as Example 1-4.

The end mill body had a blade diameter of 12 mm, a corner blade diameter of 1.5 mm, and six outer peripheral blades. Further, the radial rake angle α of the chamfer surface of Example 1-4 is as shown in Table 1. The radial rake angles β of the chip discharge grooves of Example 1-4 are all 0 °.

<Comparative Example 1>
An end mill body having the same shape as that of Example 1 was produced as Comparative Example 1 except that the chamfer surface 30 was not provided.

<Test 1>
The end mill body of Examples 1-4 and Comparative Example 1 was subjected to a peripheral edge cutting test. As the work material, a nickel alloy (ALLOY 718) was used.

The cutting conditions were a cutting speed of 600 m / min, a cutting amount of ap: 3 mm, ae: 12 mm, and grooving without using cutting oil. The feed amount f per blade was changed from 0.02 mm / t to 0.06 mm / t, and a defect of the outer peripheral blade was confirmed for each feed amount f. The results of Test 1 are shown in Table 1. In Table 1, A indicates no defect and B indicates a defect.

As shown in Table 1, in Comparative Example 1 having no chamfer surface, the outer peripheral edge was broken when the feed amount f was 0.04 mm / t. On the other hand, in Example 1-4 having a chamfer surface, no defect occurred even at a higher feed amount than in Comparative Example 1.

Further, in Example 2-4 in which the radial rake angle of the chamfer surface is −15 ° or less, no chipping occurs even when the feed amount f is 0.06 mm / t, and the cutting efficiency is higher than that when the feed amount f is large. It was possible.

<Test 2>
The end mill body of Example 1-4 and Comparative Example 1 was subjected to a cutting performance evaluation test of the outer peripheral blade. As the work material, a nickel alloy (ALLOY 718) was used.

The cutting conditions were a cutting speed of 600 m / min, a cutting amount of ap: 9 mm, ae: 4 mm, a feed amount f per blade of 0.032 mm / t, and shoulder cutting without using cutting oil shown in FIG. went.

7, the straight arrow indicates the feed direction of the end mill body 3, and the arc-shaped arrow indicates the rotation direction of the end mill body 3. After shoulder cutting, the height of burrs at the three points of the inlet R1, the center R2, and the outlet R3 of the work material R was measured. The results of Test 2 are shown in Table 2.

In Table 2, A indicates no defect and B indicates a defect. In Table 2, “large” indicates a burr height of 2.0 mm or more, and “small” indicates a burr height of less than 2.0 mm. In Comparative Example 1, the burr height could not be evaluated because a defect occurred in the outer peripheral blade.

As shown in Table 2, in Comparative Example 1 having no chamfer surface, a defect occurred due to insufficient strength of the outer peripheral blade. On the other hand, in Examples 1-4 having a chamfer surface, the peripheral edge was not damaged.

Furthermore, in Example 1-3 in which the radial rake angle on the chamfer surface was −30 ° or more, the burr height at the exit R3 was small, and the cutting performance of the outer peripheral blade was high.

Claims

A ceramic end mill body that constitutes a cutting edge portion of an end mill that rotates about an axis,
A chip discharge groove provided on the outer periphery of the front end portion so as to be twisted backward in the rotation direction from the front end side toward the rear end side,
An outer peripheral blade provided on an outer peripheral side ridge line of the chip discharge groove;
A gasche from the top of the tip to the chip discharge groove,
A bottom blade provided at the top of the tip;
A bottom rake face extending from the bottom blade toward the rear end;
A corner blade provided so as to protrude outward from the bottom blade to the outer peripheral blade;
A corner rake face provided between the bottom rake face and the chip discharge groove so as to contact the corner blade;
A chamfer surface provided at an outer peripheral blade ridge line portion where at least the chip discharge groove and the flank of the outer peripheral blade intersect,
An end mill body.
2. The end mill body according to claim 1, wherein a radial rake angle α of the chamfer surface at the outer peripheral edge portion is not less than −30 ° and not more than −15 °.
The end mill body according to claim 2, wherein a difference (β-α) obtained by subtracting the radial rake angle α from a radial rake angle β of the chip discharge groove is 10 ° or more and 30 ° or less.
The chamfer surface is also provided on at least a part of a corner blade ridge line portion where the corner rake surface and the flank surface of the corner blade intersect,
The end mill body according to any one of claims 1 to 3, wherein a radial rake angle γ of the chamfer surface at the corner edge portion is not less than -30 ° and not more than -15 °.
The end mill body according to claim 4, wherein the chamfer surface is not provided on the bottom blade.
The end mill body according to any one of claims 1 to 5, wherein a corner having a radius of 0.5 mm or more and 2 mm or less is attached to a corner portion of the gasche that is farthest from the bottom blade.
The end mill body according to any one of claims 1 to 6, constituting a cutting edge portion of a radius end mill.
The end mill body according to any one of claims 1 to 7,
A shank portion attached to a rear end portion of the end mill body and configured to be fixed to a rotating shaft of a machine tool;
An end mill.
The shank portion is made of ceramic,
The end mill according to claim 8, wherein the end mill body and the shank portion are configured integrally.
The end mill body according to claim 8, wherein the end mill body has a connecting portion configured to be detachably connected to the shank portion.