JPH0319003B2 - - 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. 7, 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 with an unequal twist, 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 in an unequal twist, the intervals in the circumferential direction of the cutting blades 1 differ from each other over the entire length.

Therefore, when grooving the work material 2 as shown in FIG. Has the portion 1b reached the position 4 where it exits from the cutting of the workpiece 2 as in the case shown in FIG. 9?
Or, on the contrary, it has already passed through position 4 (this case is not shown). In other words, when the cutting edge portion 1a cuts into the workpiece 2, the cutting edge portion 1c that comes out of cutting the workpiece 2 is:
As shown in the figure, it is located on the axially distal end side of the cutting edge portion 1a, or on the contrary, it is located on the proximal end side (not shown in this case).
Therefore, the back forces Fa and Fc acting in the radial direction toward the axis by the cutting blade portion 1a and the cutting blade portion 1c act on the end mill body 3 as shearing forces, and this causes new vibration. There was a problem in that this caused a problem in that this resulted in deterioration of the finished surface accuracy.

In addition, especially when the ratio (l/D) of the overall length of the cutting blade to the end mill diameter D is large and the number of cutting blades is small, bending distortion occurs in the end mill body, resulting in poor groove width dimension accuracy. There was also the problem that the performance decreased.

Furthermore, the cutting edge 1... is set at different helix angles α ₁ , α ₂ , α ₃ ,
Because they are formed to have α ₄ , α ₅ , and α ₆ , it is difficult to determine the position that should be used as the reference point for polishing when forming the cutting edge, and the manufacturing itself requires a great deal of effort and skill. There was a drawback that it was necessary.

[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 cutting performance.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention has provided that the cutting edges of four or more unequal helical threads, which are symmetrical with respect to the axis of the even number of cutting edges, are equal to each other. The end mill body is formed at a helical angle, and these cutting edges are formed at equal intervals in the circumferential direction at the tip of the end mill body.

[Effect]

According to the end mill having the above configuration, the intervals in the circumferential direction of the cutting blades located symmetrically with respect to the axis are equal to each other over the entire length of these cutting blades. Therefore, the cutting edge portion of the cutting edge that cuts into the work material and the cutting edge portion that exits from the cutting of the work material are located at positions that are symmetrical to each other with respect to the axis. This results in
Since the back forces acting in the axial direction by the two cutting edge portions cancel each other out, no shearing force that causes vibration etc. acts on the end mill.

Further, since the tips of the cutting blades formed at equal intervals can be used as a reference when forming the cutting blades, processing of these cutting blades is easy.

〔Example〕

1 to 4 show an 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, the bottom blade 2 extends from each of the cutting blades 12 to 15 in a radial direction toward the center of rotation.
0, 21, 22, 23 are formed.

Here, the above four cutting edges 12, 13, 14, 1
5, as shown in FIGS. 2 and 4, in the tip portions 12a to 15a of the end mill main body 11,
They are formed at equal intervals P in the circumferential direction of the end mill main body 11. In addition, the bottom blades 20 to 23 connected to these cutting blades 12 to 15
are formed to equally divide the tip surface 25, respectively.

Furthermore, the four cutting edges 12, 13, 14, 1
The helix angle of No. 5 is θ 1 for the cutting blades 12 and 14, _{which are located symmetrically with respect to the axis of the end mill body 11, and θ 2 for} the cutting blades 13 and 15, respectively. .

By the way, these cutting edges 12, 14 and cutting edge 13,
As a result of setting the torsion angles θ ₁ and θ ₂ to be different from each other, as shown in FIG.
There are wide and narrow widths in the width dimension of 19. In this case, if a chip discharge groove with a width dimension that is too narrow is formed, the discharge of chips will be hindered. Therefore, the difference in magnitude between these helix angles θ ₁ and θ ₂ is 1° for an end mill with a diameter D of 3 mm to 25 mm and a ratio (l/D) of the diameter D to the total cutting edge length l of about 3. It is desirable to set it to ~5°.

In the end mill having the above configuration, the intervals in the circumferential direction between the cutting blades 12 and 14 and between the cutting blades 13 and 15, which are located symmetrically with respect to the axis, are equal to each other over the entire length of the cutting blades. Therefore, as shown in FIG. 5, for example, the cutting edge portion 12a of the cutting edge 12 that cuts into the workpiece 26 and the cutting edge portion 14a of the cutting edge 14 that exits from the cutting are aligned with respect to the axis of each other. The position will be symmetrical. This results in
Since the thrust forces Fa and Fa acting on the end mill body 11 by the two cutting edge portions 12a and 14a cancel each other out, no shearing force acts on the end mill body 11. Therefore, the end mill main body is free from vibrations caused by the thrust force of the cutting blades 12 to 15 and from a decrease in finished surface accuracy, so that stable cutting performance can always be obtained.

In addition, the tip portions 12a to 15a of the cutting blades 12 to 15
are formed at equal intervals P in the circumferential direction of the end mill main body 11, so by using these tip portions 12a to 16a as a reference when forming the cutting blades, the cutting blades 12 to 16 can be Polishing can be easily performed. In addition, since it is easy to form the bottom edges 20 to 23 in the same way, including during re-sharpening, it is possible to obtain good axial runout accuracy for these bottom edges 20 to 23. Since only the bottom cutters 20 to 23 do not wear out prematurely, a long tool life can be obtained.

Furthermore, since the bottom blades 20 to 23 are formed on the tip surface 25 of the end mill body 11 so as to equally divide the tip surface 25, equally spaced feed marks are formed on the surface of the workpiece, and as a result, Combined with the vibration damping effect of the unequal twist end mill, it is possible to obtain a good finished surface. For this reason, although it can be used for high-speed cutting that is prone to vibration and chatter due to its excellent tool rigidity, it has a remarkable effect when applied to end mills made of cemented carbide or cermet, whose cutting edges are prone to chipping. can be obtained.

[Other Examples]

FIG. 6 shows another embodiment of the end mill of the present invention, in which it is applied to an end mill having six cutting edges 30 to 35.

In the end mill of this example, these cutting blades 3
Among 0 to 35, the helix angle of the cutting blades 30 and 33, which are symmetrical with respect to the axis, is θ ₁ , the helix angle of the cutting blades 31 and 34 is θ ₂ , and the helix angle of the cutting blades 32 and 34 is θ 2. The helix angles of the blades 35 are each formed at θ ₃ .

These cutting edges 30 to 35 are also formed at equal intervals in the circumferential direction at the tip of the end mill body.

With the above configuration, the same effects as shown in FIGS. 1 to 4 can be obtained in the end mill as well.

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. Further, in the end mill of the above-described embodiment, four or six cutting edges are formed, but the cutting edge is not limited to these, and any number of cutting edges that are greater than these and an even number may be used.

Furthermore, although the twisting direction of each cutting edge is set so that the rake angle of the cutting edge is a positive rake angle, the twisting direction may be reversed.

〔Effect of the invention〕

As explained above, in the end mill of the present invention, among the four or more even number of cutting blades with unequal helix, the cutting blades at positions symmetrical with respect to the axis are set at equal helix angles. and these cutting blades are formed at equal intervals in the circumferential direction at the tip of the end mill body, so that the part of the cutting blade that cuts into the workpiece and the part of the cutting blade that exits from cutting the workpiece. The thrust forces acting in the axial direction cancel each other out. Therefore, vibrations caused by the above-mentioned thrust force and a decrease in finished surface accuracy do not occur in the end mill body, and excellent cutting performance can always be obtained. Further, by using the tips of the cutting blades formed at equal intervals as a reference when forming the cutting blades, these cutting blades can be easily processed.

[Brief explanation of drawings]

1 to 4 show an embodiment of the present invention, FIG. 1 is a side view, and FIG. 2 is a side view of FIG. 1.
3 is a sectional view taken along the - line in FIG. 1, FIG. 4 is a developed view of the cutting blade, FIG. 5 is a schematic diagram showing the thrust force that acts during cutting, and FIG. 6 is a cross-sectional view of the present invention. FIGS. 7 to 9 show a conventional end mill. FIG. 7 is a developed view of the cutting blade, and FIG. A schematic diagram showing the state, and FIG. 9 is a schematic diagram showing the thrust force acting during cutting. 11... End mill body, 12, 13, 14, 1
5, 30, 31, 32, 33, 34, 35... Cutting blade, 12a, 13a, 14a, 15a... Cutting blade tip, 20, 21, 22, 23... Bottom blade, θ ₁ , θ ₂ ,
θ ₃ ...Twisted angle.

Claims (1)

[Claims] 1. In an end mill in which four or more cutting blades with different helix angles and an even number of cutting blades are formed on the outer periphery of the tip of the end mill body, the cutting blades at symmetrical positions with respect to the axis of the cutting blades are These cutting edges are formed to have equal helix angles, and
An end mill characterized in that the distal end portion of the end mill body is formed at equal intervals in the circumferential direction.