JPS6389214A - End mill - Google Patents

Abstract

PURPOSE:To ensure the prevention of a vibration due to cutting by constituting cutting edges in such a way that among the even number of our or more cutting edges of unequal helix, the cutting edges symmetrically positioned about an axial line are made to have and equal helix angle and arranged at equal intervals in a circumferential direction at the tip of an end mill. CONSTITUTION:Cutting edges 12, 13, 14 and 15 are formed at the tips 12a-15a of an end mill proper 11 in such a way that end cutting edges 20-23 divide an tip face 25 equally at equal intervals P in a circumferential direction, the helix angle of the cutting edges 12 and 14 symmetrically positioned about an axial line is taken at theta1 and for the cutting edges 13 and 15, the angle is similarly taken at theta2. Therefore, the cutting edge part 12a coming into a workpiece and another cutting edge part 14 coming out of the workpiece come to be located symmetrically about an axial line, and the cutting edge parts 12a and 14 offset a back force component working on the end mill proper 11. Thus, the end mill proper 11 is free from a shear force and no vibration occurs. Also, the use of the edges 12a-15a as reference points for forming cutting edges enables an easy polishing process.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an end mill in which a plurality of cutting edges are formed in an unequal twist on the outer periphery of the tip of an end mill body.

[Prior art] As a conventional end mill of this type, the
As shown in Figure 7, on the outer periphery of the tip of the end mill body, there are multiple cutting blades that draw a spiral in the axial direction. ... are mutually different torsion angles α1. α1. α5. α4. α6. One formed at α8 is known.

In this end mill, the cutting edges 1... are formed in an unequal twist, so the cutting force and action time of these cutting edges 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, which has the advantage of preventing chatter caused by cutting force and improving its cutting performance. It will be done.

[Problems to be Solved by the Invention] However, in the above-mentioned conventional end mill, as a result of forming the cutting edges l... with unequal twists, these cutting edges l...
The intervals in the circumferential direction differ from each other over the entire length.

Therefore, when the second groove is machined as shown in FIG. The cutting edge portion 1b is
As in the case shown in FIG. 9, the position t at which the workpiece 2 exits from cutting has not been reached, or, conversely, the position 4 has already been passed (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 exits from the cutting of the workpiece 2 is located at a tip end in the axial direction from the cutting edge portion 1a as shown in the figure. or, conversely, proximally (not shown in this case). Therefore, the end mill main body 3 includes a cutting edge portion 1a and a cutting edge portion I.
Since thrust forces Fa and Fch acting in the radial direction toward the axis due to C act as a shearing force, this causes new vibrations, which leads to a problem in that the finished surface q degree deteriorates.

In particular, the ratio of the total cutting edge length Q to the end mill diameter (12
/D) is large and the number of cutting edges is small,
There is also the problem that bending strain occurs in the end mill body, resulting in a decrease in the accuracy of the width dimension of the groove.

Furthermore, the cutting edges l... are arranged at different helix angles α1. α2. α3
゜α4. α6. Since it is formed to have an angle of α8, it is difficult to determine the position to be used as a reference point for polishing when forming the cutting edge, and the manufacturing itself requires a great deal of effort and skill.

[Object of the Invention] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an end mill that can reliably prevent the occurrence of vibrations caused by cutting and that can obtain excellent cutting performance. The purpose is to

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a cutting blade that is symmetrical with respect to the axis of an even number of cutting blades having four or more unequal twists. The cutting edges at each position are formed to have the same helix angle, and these cutting edges are formed at equal intervals in the circumferential direction at the tip of the end mill body.

[Function] According to the end mill configured as described above, the circumferential spacing of the cutting blades that are symmetrically positioned with respect to the axis is equal to the spacing over the entire length of these cutting blades. Therefore, the part of the cutting blade that cuts into the workpiece and the part of the cutting blade that exits from the cutting of the workpiece are located at positions that are symmetrical to each other with respect to the axis.

As a result, the back forces acting in the axial direction by the two cutting blade portions cancel each other out, so that shearing forces that cause vibrations etc. do not act on the end mill.

In addition, since the tip portions of the cutting blades formed at equal intervals can be used as Jill when forming the cutting blades, processing of these cutting blades is easy.

[Embodiment] FIGS. 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.

This end mill body 11 is made of high-speed steel, cemented carbide, etc. and has an approximately round-shaped external appearance, and the outer periphery of its tip has four cutting blades 12, 13, 14, and 15 twisted in the axial direction.
is formed. and −++, :mTll9
IQ+71jsu/;Thself-old-1-)Q? Chip discharge groove 16.1? , 18.19 are formed. Further, the end face 25 of the end mill body 11 is formed with bottom blades 20, 21, and 22°23 extending from the cutting blades 12 to 15 in the radial direction toward the rotation center.

Here, the above four cutting edges 12. l 3,14.15 is
As shown in Fig. 2 and Fig. 4, the end mill body ll
The end portions 12a=15a of the end mill body 11 are formed at equal intervals P in the circumferential direction of the end mill body 11. Further, the bottom blades 20 to 23 connected to the cutting blades 12 to 15 are formed so as to equally divide the tip surface 25, respectively.

Furthermore, the helix angles of the four cutting edges 12, 13, 14, and 15 are such that the cutting edges 12 and 14, which are located symmetrically with respect to the axis of the end mill body 11, are each θ1, and the cutting edges and the cutting edge 15 are respectively 0. It is said that

By the way, the helix angle θ3 between these cutting edges 12.14 and 13.15. As a result of setting θ to different angles, the widths of the chip discharge grooves 16 to 19 vary, as shown in FIG. 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, these torsion angles are 04.
As for the difference in size of θ, the diameter of the end mill is 3 mm ~
At 25 mm, the ratio of diameter to total cutting edge length Q (12/D) is 3.
It is desirable to set the angle to 1° to 5° for objects of about 1° to 5°.

The end mill with the above configuration has a cutting edge 12.14 and a cutting edge 13.1 that are symmetrically positioned with respect to the axis.
The respective circumferential spacings between the cutting edges are equal over the entire length of the cutting edge. Therefore, as shown in Figure 5,
For example, a cutting edge portion 12a of the cutting edge 12 that cuts into the workpiece 26 and a cutting edge portion 14a of the cutting edge 14 that exits from the cutting position are symmetrical to each other with respect to the axis. As a result, the thrust forces Fa1Fa acting on the end mill body 11 by the two cutting blade portions 12a and 14a cancel each other out, so that no shearing force acts on the end mill body 11. Therefore, vibrations caused by the back force of the cutting blades 12 to 15 and deterioration in finished surface accuracy do not occur in the end mill body, and stable cutting performance can always be obtained.

Further, the tip portions 12a=15a of the cutting blades 12 to 15 are arranged at equal intervals P...
These tips 12a to 16 are formed so as to be separated from each other.
These cutting edges 1 can be formed by making a thicker when forming the cutting edge.
2 to 16 polishing processes 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. Because only the blades 20 to 23 do not wear out early,
Get long tool life.

Furthermore, bottom blades 20 to 20 are attached to the tip surface 25 of the end mill body 11.
23 is formed so as to equally divide the tip surface 25, so that equally spaced feed marks are formed on the surface of the workpiece.
As a result, a good finished surface can be obtained in combination with the vibration damping effect in this type of end mill with unequal twist. 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 easily chipped. effect can be obtained.

[Other Embodiments] FIG. 6 shows another embodiment of the end mill of the present invention,
An example of application to an end mill having six cutting edges 30 to 35 is shown.

In the end mill of this example, these cutting edges 30 to 35
Among them, the helix angle of the cutting blade 30 and the cutting blade 33 which are symmetrical with respect to the axis is 01, and the cutting blade 31 and the cutting blade 34 are
The torsion angle of is 9. Furthermore, twist rfl of the cutting edge 32 and the cutting edge 35 is formed at 03, respectively.

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

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

In addition, in the above example, a solid type end mill made entirely of high-speed steel or cemented carbide was described, but a brazing type in which a cutting tip with a cutting edge is brazed to the end mill body is not applicable. There may be. Furthermore, although the end mill of the above embodiment has four or six cutting edges, 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 sufficient.

Further, although the twist direction of each cutting edge is set so that the rake angle of the cutting edge is a positive rake angle, the I-skew direction may be reversed.

[Effect of the invention] As explained above, in the end mill of this invention,
The cutting edges of IiL 'Jl, which are symmetrical with respect to the axis of the even number of cutting edges with four or more threads with unequal helix, are formed to have the same helix angle, and these cutting edges are cut with an end mill. Because they are formed at equal intervals in the circumferential direction at the tip of the main body, the back force acting in the axial direction by the part of the cutting blade that cuts into the workpiece and the part of the cutting blade that leaves the workpiece from being cut is reduced. cancel each other out. Therefore, the end mill body does not experience vibrations caused by the thrust force or a decrease in finished surface accuracy, and therefore 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 the drawing]

1 to 4 show an embodiment of the present invention. FIG. 1 is a side view, FIG. 2 is a fixation view along the line ■-■ in FIG. [I-I [[Fixed sectional view, Figure 4 is a developed view of the cutting blade, Figure 5 is a schematic diagram showing the thrust force acting during cutting, Figure 6 shows another embodiment of the present invention. Developed view of the cutting blade,
Figures 7 to 9 show conventional end mills.
The figure is a developed view of the cutting blade, FIG. 8 is a schematic diagram showing the state of groove machining on a workpiece, and FIG. 9 is a schematic diagram showing the thrust force acting during cutting. 11... End mill body, 12.13, 14.15, 30, 31.32, 33゜3
4.35... Cutting blade, 12a, l 3a, 14a, 15a --- Cutting blade tip, 20.21, 22.23... Bottom blade, θ1
．． θ3. θ3...Twist angle.

Claims (1)

[Claims] In an end mill in which four or more cutting blades with different helix angles and an even number of 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 connected to each other. An end mill characterized in that the cutting edges are formed to have equal helix angles and are equally spaced in the circumferential direction at the tip of the end mill body.