JPH0319004B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] This invention provides an end mill body with a
The present invention relates to an end mill in which a plurality of cutting edges are formed in an unequal twist.

[Conventional technology]

As a conventional end mill of this type,
As shown in FIG. 4, on the outer periphery of the tip of a large-diameter cylindrical end mill body, as shown in Japanese Patent No. 5244, a plurality of cutting edges 1 spiraling in the axial direction are provided with different helix angles α ₁ , Those formed at α ₂ , α ₃ , α ₄ , α ₅ , and α ₆ are known.

In this end mill, the cutting blades 1 are formed in a so-called unequal helix, so the cutting force and action time of these cutting blades 1 differ in the circumferential direction and the axial direction. Therefore, periodic vibrations that resonate with the end mill's natural frequency do not occur in the end mill body, making it possible to prevent chatter caused by cutting force, thereby improving its cutting performance. You will get some advantages.

[Problem that the invention seeks to solve]

However, in the conventional end mill described above, as a result of forming the cutting blades 1 to have an unequal twist, the sixth
As shown in the figure, the interval between the cutting edges 1 in the circumferential direction changes in the axial direction. In other words, the width of the chip discharge groove formed between the cutting edges 1 varies. For this reason, especially the total cutting edge length l
and the end mill diameter D (l/D) is large,
In addition, in the case of a tool with a large number of cutting edges, the width of the chip evacuation groove becomes excessively narrow at the distal and proximal ends of the cutting edge, resulting in chip clogging and cutting. There was a problem in that the blade could become damaged or, in severe cases, the end mill body could break.

[Purpose of the invention]

This invention was made in view of the above circumstances,
It is an object of the present invention to provide an end mill that can reliably prevent the occurrence of vibrations caused by cutting and that can provide excellent chip evacuation performance.

[Means for solving problems]

In order to solve the above-mentioned problems, this invention has a first cutting edge that has a constant helix angle from the distal end to the proximal end, and a cutting edge portion on the distal side with the center as a border and a proximal end. The helix angle of one of the side cutting edge portions is smaller than the helix angle of the first cutting edge, and the other cutting edge portion has a helix angle smaller than the helix angle of the first cutting edge. Second cutting edges having a larger helix angle are alternately formed in the circumferential direction.

[Effect]

According to the end mill having the above configuration, the first cutting blade has a constant helix angle, and the second cutting blade has a helix angle that changes at the center located at the rear of the first cutting blade in the rotational direction. The interval between the two ends becomes gradually narrower (or wider) from the distal end toward the center, but conversely becomes gradually wider (or narrower) from the center toward the proximal end. Therefore, the distance between the first and second cutting blades becomes excessively narrow compared to a case where the helix angle of all the cutting blades is constant from the tip to the base and is twisted unequally. It is possible to prevent clogging of chips, etc.

In other words, when forming the same cutting edge spacing as if the helix angle of all cutting edges were constant,
Since the difference between the helix angles of the adjacent first and second cutting edges can be made approximately twice the difference when the helix angles are constant, an even better vibration damping effect can be obtained.

〔Example〕

1 to 3 show a first embodiment of an end mill according to the present invention, and reference numeral 11 in the figures indicates an end mill main body.

The end mill body 11 is made of high-speed steel, cemented carbide, etc. and has a generally cylindrical appearance, and has four cutting blades 1 twisted in the axial direction on the outer periphery of its tip.
2, 13, 14, and 15 are formed. Between these cutting blades 12, 13, 14, 15, there are chip discharge grooves 16, 17, 18, 19, respectively.
is formed. Also, this end mill body 1
1, bottom blades 20, 2 are provided on the tip surface thereof, each extending from the cutting blades 12 to 15 in a radial direction toward the center of rotation.
1, 22, and 23 are formed.

Here, as shown in FIG. 3, among the four cutting blades 12, 13, 14, 15, the end mill main body 1
The helix angles of the cutting blades (first cutting blades) 12 and 14 that are symmetrical with respect to the axis of the tip 1 are
The angle θ ₁ is constant from 2a, 14a to the base end portions 12b, 14b. In addition, a cutting edge (second cutting edge) 1 located between these cutting edges 12 and 14
The helix angles of the cutting edges 1 and 15 are as follows:
The torsion angle θ ₂ is smaller than the torsion angle θ ₁ of 2 and 14, and furthermore, from the central portions 13c and 15c to the base end portion 13
The torsion angle θ ₃ up to b and 15b is larger than the above-mentioned torsion angle θ ₁ . These torsion angles θ ₁ , θ ₂ , θ ₃ are mutually {θ ₃ −θ ₁ =θ ₁ −θ ₂
}
is set to be.

Further, these cutting blades 12 to 15 are formed at equal intervals L in the circumferential direction at the tip portions 12a to 15a of the end mill main body 11. As a result, between these cutting edges 12 and 13 and between the cutting edges 1
The chip discharge grooves 16 and 18 between 4 and 15 are formed so that they gradually become narrower at a constant rate from the tip to the center, and then gradually widen at the same rate from the center to the base. has been done. Therefore, the cutting edges 12 to 15 have their respective proximal ends 12b.
~15b are also approximately equally spaced L in the circumferential direction.
It is formed by separating the

In the end mill having the above configuration, the first cutting edges 12 and 14 have a constant helix angle θ ₁ .
and second cutting blades 13, 15, which are located at the rear of these cutting blades 12, 14 in the rotational direction and whose helix angle changes from θ ₂ to θ ₃ at the center portions 13c, 15c. The distance between 16 and 18 gradually narrows from the distal end toward the center, but conversely becomes gradually wider from the center toward the proximal end. Therefore,
A wider spacing between the chip evacuation grooves 16 and 18 can be secured than when the cutting blades 13 and 15 have a constant helix angle of θ ₂ or θ ₃ from the tip to the base. Therefore, chips can be smoothly discharged.

In other words, when forming a chip evacuation groove of the same size as when the helix angles of all cutting edges are constant, the difference in the helix angles of adjacent cutting edges (θ ₁ −θ ₂ ) or ( θ ₁ −θ ₃ ) can be formed to be approximately twice as large as that of a case where the twist angle is constant, so an even better vibration damping effect can be obtained.

Further, these cutting blades 12 to 15 are connected to the tip portion 12a.
~ 15a are formed at equal intervals, and the torsion angles θ ₁ , θ ₂ , θ ₃ are set so that they are {θ ₃ - θ ₁ = θ ₁ - _{θ 2} }, so it is easy to cut during manufacturing. The so-called indexing operation for polishing the blade becomes easier. Therefore, the cutting edges 12 to 16 can be easily polished, thereby simplifying their manufacture.

[Other Examples]

FIG. 4 shows a second embodiment of the end mill of the present invention.

In this end mill, the end mill body 3
Four cutting edges 32, 33, 34, 3 formed in 1
5, the helix angles of the cutting blades (first cutting blades) 32 and 34 that are symmetrical with respect to the axis are constant angles θ ₁ from the tip portions 32a and 34a to the base portions 32b and 34b, respectively. It is said that Further, the helix angle of the cutting blades (second cutting blades) 33, 35 located between these cutting blades 32, 34 is
The helix angle θ 3 is larger than the helix angle θ ₁ of the cutting blades 32, 34 from 5a to the central portions 33c, 35c, and the helix angle θ ₃ is greater than the helix angle θ 1 of the cutting blades 32, 34, and the helix angle θ 3 is greater than the helix angle θ 1 from the central portions 33c, 35c to the base end portions 33b, 35b. The torsion angle θ ₂ is smaller than the angle θ ₁ . These torsion angles θ ₁ , θ ₂ , θ ₃ are mutually {θ ₃ −θ ₁ =θ ₁ −
θ ₂ }.

Even in the case of the second embodiment having the above configuration, the same effects as those of the first embodiment can be obtained.

In the above embodiments, a solid type end mill made entirely of high-speed steel or cemented carbide was described, but it is also a brazed type end mill in which a cutting tip having a cutting edge is brazed to the end mill body. Good too. In addition, although the end mill in the above embodiment has four cutting edges, it is not limited to this, and the same applies to those having two or more cutting edges. Can be done.

In addition, in the above embodiments, the cutting edge 1
2 to 15, 32 to 35 to the end mill body 11, 3
Although the second cutting edges 4 are formed at equal intervals L at the tips 12a to 15a and 32a to 35a of the first cutting edge 4, the second cutting edge 4 is not limited to this, as shown in FIG.
The helix angle of 3, 45 is the first cutting edge 4 from the tip portions 43a, 45a to the central portions 43c, 45c.
The torsion angle θ ₂ is smaller than the torsion angle θ ₁ of 2 and 44, and furthermore, from the central portions 43c and 45c to the base end portion 43
In the end mill in which the helix angle θ ₃ is larger than the helix angle θ ₁ up to the helix angle θ 1 up to b and 45b, the cutting edge 42 and the cutting edge 43 and the cutting edge 44 and the cutting edge 45
The distance L ₁ between the cutting blade 43, the cutting blade 44, and the cutting blade 4
5 and the cutting edge 42 may be formed larger than _L2 . According to this end mill, the cutting blades 42 to
45 can be made even more uniform.

Incidentally, this effect is obtained when the helix angle of the second cutting edge is opposite to that shown in FIG. 5, that is, when it is similar to that shown in _FIG. <L ₂ can be similarly obtained.

〔Effect of the invention〕

As explained above, the end mill of this invention is
The first cutting edge has a constant helix angle from the distal end to the proximal end, and the helix angle of one of the distal and proximal cutting edge sections with the center as a boundary. has a helix angle smaller than the helix angle of the first cutting edge, and the other cutting edge has a helix angle larger than the helix angle of the first cutting edge, and The unequal torsion effect reliably prevents the occurrence of vibrations caused by cutting, as well as ensuring a wider spacing between the cutting edges, resulting in excellent chip evacuation performance. You can also get

[Brief explanation of the drawing]

Figures 1 to 3 show a first embodiment of the end mill of the present invention, where Figure 1 is a side view, Figure 2 is a view taken along the - line in Figure 1, and Figure 3 is an expanded view of the cutting blade. figure,
Fig. 4 is a developed view of a cutting blade showing a second embodiment of the present invention, Fig. 5 is a developed view of a cutting blade showing another embodiment of the present invention, and Fig. 6 is a developed view of a cutting blade showing a conventional end mill. This is a developed diagram. 11... End mill body, 12, 14, 32, 3
4, 42, 44...first cutting edge, 13, 15, 3
3, 35, 43, 45...second cutting blade, 12a, 1
3a, 14a, 15a, 32a, 33a, 34
a, 35a, 43a, 45a... tip, 12b,
13b, 14b, 15a, 32b, 33b, 34
b, 35b, 43b, 45b... base end, 13c,
15c, 33c, 35c, 43c, 45c...Central part, _θ1 , _θ2 , _θ3 ...Twisted angle.

Claims (1)

[Claims] 1. On the outer periphery of the tip of the end mill body, there is a first cutting edge with a constant helix angle from the tip to the base, and a cutting edge from the tip to the center and from the center to the base. The helix angle of one of the cutting edge portions leading to the first cutting edge is smaller than the helix angle of the first cutting edge, and the other cutting edge portion has a helix angle smaller than the helix angle of the first cutting edge. An end mill characterized in that second cutting edges each having a helix angle larger than the angle are formed alternately in the circumferential direction.