JP2016215294A - End mill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an end mill capable of securing a large feeding amount in an axial direction and cutting with high efficiency.SOLUTION: An end mill comprises in an order from a tip end side: a cutting blade part 4; a neck part 3 having diameter which is smaller than outer diameter of the cutting blade part 4; and a shank part 2. An outer periphery of the cutting blade part 4 comprises: a chip discharge groove 5 which is twisted spirally with respect to an axial line O of the cutting blade part 4; and an outer peripheral cutting blade 6 formed on a side ridge part on the outer peripheral side of the chip discharge groove 5. When outer diameter of the outer peripheral cutting blade 6 is D, outer diameter of the neck part 3 is d, and when a cutting amount in a radial direction to the workpiece during processing is (D-d)/2, for processing, blade length L of the cutting blade part 4 in the axial direction is longer than length when a next forefront part starts cutting at a time point when a last end part of the outer peripheral cutting blade 6 in a spiral state finishes cutting, and is shorter than length when the next forefront part also finishes the cutting at a time point when the last end part of the outer peripheral cutting blade 6 finishes the cutting.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an end mill, and more particularly, to an end mill having a small cutting edge and a long neck.

End mills used for processing metal parts, etc., have a shank on the rear end side of the main body held in a cantilevered state by a machine tool, rotated at high speed around the axis of the end mill, and fed while cutting in the direction intersecting the axis. It is used by cutting the outer peripheral cutting edge of the blade part into the work material. For this reason, generally, at the time of cutting, a reaction force in a direction intersecting the axis from the work material acts, and a bending that the axis is curved occurs in the end mill body, and is used for cutting in this state.
In particular, when performing so-called deep engraving, where the depth to be processed is deeper than the length of the end mill cutting edge, the neck having a smaller diameter than the outer diameter of the cutting edge on the rear end side of the cutting edge described above. Alternatively, a so-called long neck end mill having a shank portion is used, and cutting operations are performed in multiple stages in the depth direction.

In the conventional end mill, for example, the following technique is disclosed as a technique for obtaining a high machining surface accuracy by preventing the lower part of the neck from falling even on a deep machining surface.
A cutting edge is provided on the tip side of the end mill body, a chip discharge groove is formed on the outer periphery of the end mill body from the cutting edge to the tip of the neck, and a cutting edge is formed on the outer side edge of the cutting edge of the chip discharge groove. And the cutting edge portion outer diameter D is larger than the outer diameter of the neck portion, and the blade length L in the axial direction of the cutting edge portion is 0.2 × D to the cutting edge portion outer diameter D. In addition to the range of 0.8 × D, the cutting length M in the axial direction of the chip discharge groove from the tip of the cutting edge is set to be equal to or larger than the cutting edge outer diameter D, and the cutting length M and the cutting edge length L of the cutting edge (M−L) is in the range of 0.1 × D to 1.0 × D (see, for example, Patent Document 1).

  In addition, for example, a cutting edge portion is provided on the tip side of the substantially cylindrical rod-shaped end mill body that rotates about the axis, and on the outer periphery of the cutting edge portion, there is a chip discharge groove and an outer peripheral side ridge portion of the chip discharge groove. In the case where the cutting edge is formed, the outer diameter of the cutting edge portion gradually decreases from the front end of the cutting edge portion toward the rear end side, and this diameter reduction ratio is larger on the rear end side than on the front end side. An end mill formed so as to become is disclosed (for example, see Patent Document 2).

Japanese Patent Laying-Open No. 2005-279899 (page 3, FIG. 1-2) JP 2007-245278 A (page 4, Fig. 1-2)

In an end mill that performs deep engraving, particularly in the case of a small diameter, it is necessary to make the amount of cut in the axial direction as small as possible in order to minimize the influence of bending.
In the end mill of Patent Document 1, the blade length in the axial direction of the cutting edge portion is made shorter than the outer diameter dimension, and the bending is reduced by shortening the contact length of the cutting edge. However, machining to a predetermined axial depth is performed. In order to do so, a large number of cutting operations must be performed, and it takes a very long time to complete the processing.
Further, even in the end mill as in Patent Document 2, since the feed amount in the axial direction at the time of machining is limited to be shorter than the length of the cutting blade, it takes a lot of cutting operations and machining time to perform deep engraving. was there.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide an end mill capable of securing a large amount of feed in the axial direction and capable of cutting with high efficiency.

  The end mill according to the present invention has a cutting edge portion on the front end side, a shank portion on the rear end side, a neck portion having a diameter smaller than the outer diameter of the cutting blade portion in the middle, and an axis of the cutting edge portion on the outer periphery of the cutting blade portion An end mill having a spirally twisted chip discharge groove and an outer peripheral cutting edge formed on a peripheral edge of the chip discharge groove, the outer diameter of the outer peripheral cutting edge being D, When the machining is performed with the diameter d and the cutting depth in the radial direction for the workpiece set to (D−d) / 2, the blade length of the cutting edge in the axial direction is the spiral outer peripheral cutting edge. It is longer than the length at which the most advanced part starts cutting when the last end finishes cutting, and the most advanced part also finishes cutting when the last end of the outer peripheral cutting edge finishes cutting. The length is shorter than the desired length.

  According to the end mill of the present invention, when the workpiece is machined with a predetermined cutting amount, the blade length of the axial cutting edge portion is the maximum when the last end portion of the spiral outer peripheral cutting edge finishes cutting. Since the tip is longer than the length at which cutting is started and the rearmost end of the outer peripheral cutting edge finishes cutting, the leading edge is also formed to be shorter than the length at which cutting ends. It is possible to suppress fluctuations in cutting resistance at the time. This makes it possible to increase the length of the outer peripheral cutting edge while suppressing fluctuations in bending, so that cutting up to a predetermined depth can be realized with a small number of cutting operations by performing cutting for the length of the blade with a single cutting operation. Processing time can be greatly reduced.

It is a side view which shows the end mill by Embodiment 1 of this invention. It is the schematic diagram which expanded the front-end | tip part of the end mill shown in FIG. It is explanatory drawing explaining the blade length L1 of the end mill by Embodiment 1. FIG. It is explanatory drawing explaining the blade length L2 of the end mill by Embodiment 1. FIG. FIG. 3 is an explanatory diagram showing a reaction force during cutting of the end mill according to the first embodiment. It is a figure which shows the cross-sectional shape of a process surface in case the blade length L is shorter than L1. It is explanatory drawing which shows the reaction force during cutting in case the blade length L is longer than L1 and shorter than L2. FIG. 3 is an explanatory diagram of deep drilling in the end mill according to the first embodiment. It is explanatory drawing of the deep digging by the conventional end mill.

Embodiment 1 FIG.
FIG. 1 is a side view of an end mill according to Embodiment 1 of the present invention. FIG. 2 is an enlarged schematic view of the tip of the end mill of FIG.
In FIG. 1, an end mill main body 1 is formed using a hard material such as a cemented carbide, has a substantially cylindrical rod shape with an axis O as a center, and a rear end 1b side (right side in the figure) shows the end mill main body 1 as a machine tool. This is a shank portion 2 for mounting on the main shaft. One tip 1a side includes a neck portion 3 having a smaller diameter than the shank portion 2, and a cutting edge portion 4 formed at the tip thereof.
With the shank portion 2 gripped by the spindle of the machine tool, the workpiece is cut by the cutting edge portion 4 by being sent around in the direction intersecting the axis O while rotating around the axis O as indicated by the rotation direction T. To form a processed surface.

The shape of each part will be described in more detail.
The shank portion 2 is composed of a straight cylindrical portion 2a that is a portion to be gripped by the spindle of the machine tool, and a truncated cone-shaped portion 2b that is gradually reduced in diameter on the tip side of the cylindrical portion 2a. .
The tip of the truncated cone portion 2 b has the same diameter as the neck portion 3 and is connected to the neck portion 3. That is, the shank part 2 is a part that combines the columnar part 2a and the truncated cone part 2b.
The neck portion 3 following the truncated cone portion 2b has a straight cylindrical shape, and a cutting edge portion 4 is formed on the tip side thereof. The shank portion 2, the neck portion 3 and the cutting edge portion 4 are both centered on the axis O.
The connecting part between the neck 3 at the tip of the truncated cone part 2b becomes the boundary between the neck 3 and the shank part 2, the tip side of the boundary is the neck lower part, and the length from the boundary to the tip 1a is N below the neck. is there.

Next, the detail of the cutting blade part 4 is demonstrated.
The cutting edge portion 4 has an outer diameter slightly larger than the outer diameter of the neck portion, and the cutting edge portion 4 has a back taper so that the outer diameter slightly decreases from the front end side toward the rear end side. Is attached and has a truncated cone shape with the axis O as the center.
Then, from the front end to the rear end of the outer periphery of the cutting edge portion 4, that is, from the front end 1a side of the end mill body 1 to the front end side portion of the neck portion 3, the chip discharge spirally twisted toward the rear side in the rotation direction T. The grooves 5 are formed to be rotationally symmetric with respect to a plurality of strips (two strips in the present embodiment) axis O.
An outer peripheral cutting edge 6 extending over the entire length in the axial direction of the cutting edge portion 4 is formed on the intersecting ridge line portion between the wall surface facing the rotational direction T of the chip discharge groove 5 and the outer peripheral surface facing the outer side in the radial direction.

FIG. 2 is an enlarged schematic view of the tip of the end mill body 1 shown in FIG.
In the drawing, D indicates the outer diameter of the outer peripheral cutting edge 6 (hereinafter referred to as cutting edge portion outer diameter D), and L indicates the blade length in the same direction as the axis O of the outer peripheral cutting edge 6. That is, the blade length L is the length from the tip 1a to the tip of the neck 3 when viewed as shown in FIG. D indicates the outer diameter of the neck 3 (hereinafter referred to as the neck outer diameter d).
Further, γ represents an angle formed by the axis O and the outer peripheral cutting edge 6, that is, a twist angle γ, and θ is a back taper angle θ. Note that the back taper angle θ is exaggerated for easy understanding. A stepped portion 7 is formed between the rear end of the cutting edge portion 4 and the outer peripheral surface of the neck portion 3.

Here, the blade length L of the present invention will be described.
When cutting a workpiece, when the cutting amount in the direction (radial direction) perpendicular to the direction (axial direction) for feeding the end mill at the time of machining is Ae, this cutting amount Ae is the amount of relief of the neck portion 3, that is, When it is set to a value (Ae = (D−d) / 2) obtained by subtracting the neck outer diameter d from the cutting blade outer diameter D and dividing by 2 (Ae = (D−d) / 2), the blade length L of the present invention is L1 to L2 described next. In other words, it is longer than L1, and shorter than L2. Then, next, the detail of the blade length L1 and the blade length L2 is demonstrated based on FIG. 3 and FIG.

  FIG. 3 is an explanatory diagram for explaining the blade length L1 of the cutting blade portion 4, and FIG. 4 is an explanatory diagram for explaining the blade length L2. Both are schematically shown for explanation. 3 and 4, (a) is a side view corresponding to FIG. 2, and (b) is a plan view of (a) viewed in the axial direction. For ease of explanation, the back taper angle θ is not shown. In addition, the workpiece to be cut is shown as a work material W in the drawing.

As shown in FIG. 3, the blade length L1 is when the cutting of the rearmost end portion (hereinafter referred to as the rearmost end portion) of one outer peripheral cutting blade 6a having a spiral shape of the cutting blade portion 4 is completed. The case where the most distal end portion (hereinafter referred to as the most advanced portion) of the next outer peripheral cutting edge 6b is formed to such a length as to start cutting is shown.
An angle φ shown in FIG. 3B indicates an angle formed by the cutting end point and the cutting start point with respect to the axis.
That is, in the case of the blade length L1, when the rearmost end of one outer peripheral cutting edge 6a reaches the cutting end point, the most distal end of the next outer peripheral cutting edge 6b comes to the cutting start point. .
The blade length L1 can be expressed by the following equation (1) using the twist angle γ, the neck outer diameter d, the cutting blade outer diameter D, and the number n of the chip discharge grooves 5.
L1 = (2π−nφ) D / (2n · tan γ) (1)
Where φ = cos ⁻¹ (d / D) (in units of radians)

Next, as shown in FIG. 4, the blade length L2 is determined so that the cutting edge portion 4 has a spiral end of the outer peripheral cutting edge 6a, and the cutting edge portion 6b ends at the same time as the cutting of the rearmost end portion of the next outer peripheral cutting edge 6b. The case where it formed in the length which also complete | finishes cutting of this is shown. That is, when the rearmost end portion of one outer peripheral cutting edge 6a reaches the cutting end point, the most distal end portion of the next outer peripheral cutting edge 6b also comes to the cutting end point.
This blade length L2 can be expressed by the following equation (2) using the twist angle γ, the cutting blade outer diameter D, and the number n of the chip discharge grooves 5.
L2 = πD / (n · tan γ) (2)
In the present invention, the blade length L is L1 <L <L2.

As an example, in the case where the twist angle γ = 30 °, the neck outer diameter d = 0.46 mm, the cutting edge outer diameter D = 0.5 mm, and the number n of the chip discharge grooves 5 = 2, the above formula (1) And from equation (2), L1 = 1.19 mm and L2 = 1.36 mm can be obtained.
From the shape of the equation, if the twist angle γ and the number n of the chip discharge grooves 5 are the same as above, and the ratio of the neck outer diameter d and the cutting edge outer diameter D is the same as above, the cutting edge outer diameter D It can be found that the blade length L should be 2.38D <L <2.72D.

Here, the significance represented by the range of L will be described.
FIG. 5 is a sectional view around the axis O during the cutting process in the end mill body 1. In the processing of the end mill, the thickness at which the outer peripheral cutting edge 6 cuts the workpiece W is the largest at the cutting start point, gradually decreases as the cutting progresses, and becomes zero at the cutting end point. Generally, it is known that the reaction force received by the end mill during cutting is proportional to the thickness to be cut. Accordingly, the reaction force received by the end mill main body 1 when the work material W is cut is the largest at the cutting start time of (a), and is almost 0 at the cutting end time of (b). On the other hand, since the surface at the start of cutting is scraped off by the next blade, the surface finally left by processing is the surface processed at the end point of cutting.

FIG. 6 is a diagram showing a cross-sectional shape at the machining end of the workpiece W being machined when the blade length L is shorter than L1.
If the blade length L is shorter than L1, when the cutting is performed at the rear end portion of the outer peripheral cutting edge 6, a very small reaction force is generated. Accordingly, the bending of the end mill body 1 is instantaneously suppressed, and the portion cut at the rear end as shown in FIG. 6 is left on the processing surface as a hollow shape. In the cross section of the processed surface, as shown by the shaded area in the drawing, a processing residue occurs and the quality of the processed surface is deteriorated.

When the blade length L is longer than L1 and shorter than L2, as shown in FIG. 7, when the cutting ends at the rear end of the cutting blade portion 4, the cutting starts at the tip of the next cutting blade portion. Therefore, a reaction force is applied to the tip of the cutting edge portion 4 and the variation of the reaction force applied to the end mill body 1 is reduced, so that stable machining can be performed without the occurrence of a hollow shape as described above. .
Moreover, when the blade length L is longer than L2, the part which becomes a cutting start point arises in several places. That is, the reaction force applied to the end mill body 1 is increased, the deflection is increased, and stable machining becomes difficult.

Further, as described above, the outer diameter of the cutting edge portion 4 is, as described above, strictly a truncated cone shape in which the outer diameter slightly decreases gradually toward the rear end side. The outer peripheral cutting edge 6 formed on the outer periphery is also inclined so that the outer diameter thereof becomes slightly smaller toward the rear end side, and has a back taper.
In this way, when the outer peripheral cutting edge 6 is back-tapered and its outer diameter gradually decreases toward the rear end side, the maximum value of the outer diameter, that is, the outer peripheral length is set for the blade length L of the outer peripheral cutting edge 6. The cutting edge outer diameter D at the tip of the cutting edge 6 is used as a reference. Further, as described above, the stepped portion 7 is formed between the rear end of the outer peripheral cutting edge 6 and the outer peripheral surface of the neck portion 3.

Here, the back taper is set so that the processed surface left when the end mill body 1 is bent by the reaction force at the time of cutting is parallel to the axis O. If the back taper is smaller than this range, the back taper is bent. The shape of the curved cutting edge portion 4 is transferred to the processing surface. On the other hand, if the back taper is larger than the above range, it becomes larger than the angle of bending due to the bending, and the back tapered shape is left on the processed surface.
The end mill of the present invention is intended for a long neck end mill having a cutting edge portion outer diameter D of a few millimeters or less. Therefore, in the present embodiment, the back taper angle θ is 0.1 ° to 1 ° in consideration of the bending of the material in the case of using a hard material such as a generally used cemented carbide or the amount of cut at the time of processing. .0 degrees. By doing so, it was verified that the influence of bending can be effectively removed and the surface accuracy of the machined surface can be improved.
Depending on the shape of the end mill, there may be no back taper.

Next, a method of cutting the workpiece W using the end mill body 1 having the above-described configuration will be described with reference to FIG. The machining will be described in the case of performing so-called deep digging in which a machining surface perpendicular to the workpiece W is formed and the depth to be machined is deeper than the edge length L of the outer peripheral cutting edge 6 of the end mill body 1. .
First, the end mill main body 1 is held in a cantilever state by causing the machine tool (not shown) such as a machining center to grip the shank portion 2. Next, the rotation driving means of the machine tool is driven to rotate the end mill main body 1 at a high speed in the rotation direction T around the axis O while feeding it in the direction intersecting the axis and the axis O, so that the outer peripheral cutting edge 6 of the cutting edge 4 is removed. Cut into the work material W.

For comparison with the present application, deep digging in the case of an end mill in which the blade length is shorter than the outer diameter of the outer peripheral cutting edge of the cutting edge portion as in the prior art will be briefly described.
FIG. 9 is an explanatory diagram when deep digging is performed by an end mill whose blade length is shorter than the outer diameter of the outer peripheral cutting edge of the cutting edge portion.
As shown in FIG. 9, in order to suppress bending, the axial depth of cut shorter than the blade length was repeated many times to perform processing to a predetermined depth.

On the other hand, in the case of the end mill of the present application, as shown in FIG. 8, the axial cut amount is set to the blade length L, and the radial cut amount is reduced by subtracting the neck outer diameter d from the cutting blade outer diameter D to 2 Set to the value divided by and process. When such conditions are set, the reaction force received by the end mill body 1 during cutting is larger than that of the conventional processing method, and the end mill body 1 is bent and the cutting edge portion 4 is curved, but the processing is performed. In the present invention, by setting the blade length L to the length as described above, the reaction force applied to the end mill main body 1 during processing can be suppressed, and the cutting edge portion 4 is further back-tapered. A vertical machining surface can be obtained.
Further, when the end mill body 1 cannot be processed to a predetermined width in the radial direction at a time due to the bending of the end mill body 1, the end mill body 1 is cut again in the radial direction and processed to a predetermined radial dimension. When it can be processed to a predetermined width in the radial direction, it is processed to a predetermined depth by repeating the procedure of cutting in the axial direction again.

In the above description, the number n of the chip discharge grooves 5 of the cutting edge portion 4 has been described as 2, but is not limited thereto, and may be 1 or 3 or more.
However, in the case of a single thread, the blade length L1 is such that when the last end of the spiral outer peripheral cutting edge 6 comes to the cutting end point, the cutting edge of the same outer peripheral cutting edge 6 is the cutting start point. The blade length L2 is the length at which the tip end portion of the same outer peripheral cutting edge 6 comes to the cutting end point when the rearmost end portion of the outer peripheral cutting edge 6 reaches the cutting end point.
Further, in the case where the chip discharge grooves 5 are a plurality of strips, a case where a plurality of strips are formed rotationally symmetric with respect to the axis O will be described. However, the present invention is not limited to this. It is also possible to adopt a so-called unequal pitch or unequal lead shape with the phases shifted to each other. By adopting such a configuration, it is possible to obtain effects such as suppressing the occurrence of “chatter” during cutting.

  Moreover, the material of the end mill main body 1 is not limited to the cemented carbide, but may be one having a hard film such as DLC (diamond-like carbon) on the surface, for example. By adopting such a configuration, it is possible to suppress tool wear, reduce friction between the work material W and the outer peripheral cutting edge 6, and lead to suppression of bending.

Moreover, in FIG. 1 and FIG. 2, although demonstrated as the shape in which the step part 7 was formed in the boundary of the rear end of the cutting blade part 4, and the neck part 3, the blade length L of the cutting blade part 4 is ensured, and from it. Alternatively, the rear end may be smoothly connected to the neck portion 3 so that the stepped portion 7 may not be formed.
By adopting such a configuration, by eliminating the stress concentration, it is possible to prevent the cutting edge portion 4 from being lost, to slightly improve rigidity, and to reduce bending.
In addition, when the end mill is cut a plurality of times in the axial direction, it leads to prevention of streaking on the processed surface. However, in the case where a smooth connecting portion is provided between the cutting edge portion 4 and the neck portion 3, the angle is larger than the back taper θ of the outer peripheral cutting edge 6, and the work material is cut when the cutting edge portion 4 is bent. It is necessary not to interfere with W.

    Instead of providing the neck portion 3, a so-called reverse stage type in which the outer diameter of the shank portion 2 is made smaller than the outer diameter D of the cutting edge portion may be used.

  As described above, according to the end mill of the first embodiment, the cutting edge portion is provided on the front end side, the shank portion is provided on the rear end side, and the neck portion having a diameter smaller than the outer diameter of the cutting blade portion is provided in the middle. Is an end mill comprising a chip discharge groove spirally twisted with respect to the axis of the cutting edge, and an outer peripheral cutting edge formed on the outer edge of the chip discharging groove. When the outer diameter is D, the outer diameter of the neck is d, and the cutting amount in the radial direction when machining the workpiece is set to (D−d) / 2, the length of the cutting edge in the axial direction is: When the last end of the spiral outer peripheral cutting edge is longer than the length at which the cutting edge starts cutting when the cutting ends, and the last end of the outer peripheral cutting edge ends when the cutting ends. Since the tip portion is also formed with a length shorter than the length at which cutting is completed, fluctuations in cutting resistance during processing can be suppressed. As a result, since the blade length of the outer peripheral cutting edge can be increased while suppressing fluctuations in bending, the number of cutting operations in the axial direction can be greatly reduced by performing cutting for the blade length in one cutting operation. Therefore, machining to a predetermined depth can be realized with few cutting operations, and the machining time can be greatly shortened.

  In addition, since the cutting edge is provided with a back taper that reduces the diameter toward the rear end of the cutting edge, even if the end mill is bent by the reaction force during cutting, the influence of bending on the machining is affected. It is possible to improve the surface accuracy of the processed surface.

  Further, the ratio N / D between the neck length N including the length of the neck portion and the cutting edge portion and the outer diameter D of the outer peripheral cutting edge is 20 or more, and the outer diameter D of the outer peripheral cutting edge is 1 mm or less. Is within the range of 0.1 degree to 1.0 degree. In particular, the ratio N / D between the neck length N and the outer diameter D of the outer peripheral cutting edge is 20 or more and the outer diameter of the outer peripheral cutting edge. In the case of a low-rigid end mill with D of 1 mm or less, the influence of bending can be effectively removed, and the surface accuracy of the processed surface can be improved.

  It should be noted that the embodiment of the present invention can be modified or omitted as appropriate within the scope of the invention.

1 End mill body, 1a tip, 1b back end, 2 shank part, 2a cylindrical part,
2b frustoconical part, 3 neck part, 4 cutting edge part, 5 chip discharge groove,
6, 6a, 6b Outer peripheral cutting edge, 7 steps, d Neck outer diameter, D Cutting edge outer diameter,
L, L1, L2 Blade length, n number of strips, N neck length, O axis, T rotation direction,
W Work material, γ Torsion angle, θ Back taper angle

Claims (3)

It has a cutting edge part on the front end side, a shank part on the rear end side, and a neck part having a diameter smaller than the outer diameter of the cutting edge part in the middle, and the outer periphery of the cutting edge part spirals with respect to the axis of the cutting edge part An end mill comprising a chip discharge groove twisted in a shape and an outer peripheral cutting edge formed on the outer peripheral side ridge of the chip discharge groove,
When processing by setting the outer diameter of the outer peripheral cutting edge as D, the outer diameter of the neck as d, and setting the cutting amount in the radial direction when machining the workpiece to (D−d) / 2,
The blade length of the cutting edge portion in the axial direction is longer than the length at which the most advanced portion starts cutting when the rearmost end portion of the spiral outer peripheral cutting edge finishes cutting, and An end mill characterized in that the end mill is formed to have a length shorter than the length at which the most distal end also ends cutting when the rearmost end of the outer peripheral cutting edge ends cutting. The end mill according to claim 1,
The end mill is characterized in that a back taper that is reduced in diameter toward the rear end side of the cutting blade portion is attached to the cutting blade portion. The end mill according to claim 2, wherein
The ratio N / D between the neck length N including the length of the neck and the cutting edge and the outer diameter D of the outer cutting edge is 20 or more and the outer diameter D of the outer cutting edge is 1 mm or less, An end mill characterized in that an angle of the back taper is in a range of 0.1 degree to 1.0 degree.

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