JPH06170630A - Ball end mill - Google Patents

Abstract

PURPOSE:To obtain a sharp cutting and long life for cutting of metal material especially for general machining of curved surfaces (copy cutting) etc. CONSTITUTION:The rake angle of an outer cutting blade in a cross-section at right angle to axial direction of a blade section is set at -29 deg. to 0 deg., the core thickness of the blade section is set within a range of 70 to 90% of a tool blade diameter, a cutting blade rise section is provided near the center of rotation in a ball blade 3 and, as viewed from the bottom, the cutting blade is formed in roughly f-shape with respect to the center of rotation. Therefore, a bulge 4 is provided so that the cutting blade is positioned at a blade diameter of 15 to 35% and a ball blade R of 40 deg. to 50 deg..

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ball end mill used for curved surface processing of metal materials, especially high hardness materials and difficult-to-cut materials.

[0002]

2. Description of the Related Art At present, the mainstream of end mills for cutting metal materials is right-handed right-handed helix and the cutting edge rake angle is set to a positive value to improve the machinability. Also,
The same applies to ball end mills, and right-hand blade right-hand twist is indispensable especially from the viewpoint of manufacturing.

[0003]

However, in the case of a ball end mill, it is impossible for the cutting edge of the ball tip to have rigidity even from the design standpoint, and since it is the center of rotation, a cutting speed can be obtained. The sharpness is poor. Further, as shown in FIGS. 1 and 2, in the case of the conventional ball end mill,
Since cutting is started from the tip of the ball, which has low rigidity and poor sharpness, there are many abrasions, abrasions and chippings due to slippage, and the machined surface roughness and accuracy cannot be obtained, and there is a problem in tool life.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to eliminate the above drawbacks and to provide a ball end mill which has a long tool life and is capable of cutting in general use by minimizing the load on the ball tip.

[0005]

In order to achieve the above object, the present invention sets the rake angle of the outer peripheral cutting edge in the cross section perpendicular to the axis of the blade portion to -29 ° to 0 °, and The core thickness of the portion is in the range of 70 to 90% with respect to the tool blade diameter, and in the ball blade, the cutting blade has a rising edge near the center of rotation, and when viewed from the bottom, the cutting blade is Since it has a substantially f-shape, a bulge is provided so as to come to a position of 15 to 35% of the blade diameter and 40 ° to 50 ° R of the ball blade. Also, Al, Si, periodic table 4a, 5a, 6a
Group 1 transition metal carbides, nitrides, oxides, borides, and one or more hard selected from the group consisting of boron carbide, hard boron nitride, hard carbon, and solid solutions or mixtures thereof. The substance is coated with one layer or two or more layers in a thickness of 0.2 to 20 μm, and T is used as the outermost layer.
iN was covered and the color tone was gold.

[0006]

By applying the present invention, since the cutting is started from the side of the outer peripheral blade which has good sharpness and high rigidity, the cutting is stable. In addition, the cutting amount decreases as it approaches the ball tip, and the cutting edge strength increases by making the rake angle negative, and chipping near the ball tip is suppressed,
Further, by setting the rake angle of the outer peripheral cutting edge to a negative value of 0 ° to -29 °, the cutting edge strength and rigidity can be obtained, so that chipping and chipping can be prevented, and good cutting is possible.

Furthermore, the ball blade has a cutting blade rising portion near the center of rotation, and when viewed from the bottom, the cutting blade is substantially f-shaped with respect to the rotation center. %, By providing a bulge so that the ball blade is located at a position of 40 ° to 50 ° R, it is formed into a substantially f shape.
This is to improve the fracture resistance of the ball blade by cushioning the impact when biting.

In the present invention, the core thickness is increased in order to increase the rigidity of the outer peripheral blade portion. In the conventional product, it is about 60% of the blade diameter, but in the present invention, it is increased to about 80%. Particularly, this is an effective means in this application where the amount of tool protrusion is long. The core thickness is 70 to 90% of the blade diameter. If it is less than 70%, the rigidity is insufficient and the tool performance deteriorates. Since the space of the chip pocket becomes small and the chip processing cannot be performed, it is set to 70 to 90%.

Further, regarding the rake angle of the outer peripheral cutting edge,
Although a sufficient effect is obtained in the range of -29 ° to 0 °, it is desirable to set the rake angle in the cross section perpendicular to the axis to -25 ° to -10 ° in order to obtain a further effect. -2
If it is 9 ° or less, it can be practically used for finish cutting, but it lacks general versatility, and if it exceeds 0 °, it becomes the same as the conventional product, so it was set to -29 ° to 0 °.

Further, the shape of the ball blade is a substantially f-shaped blade shape having a negative rake angle, so that sufficient strength can be maintained even in a low speed portion near the center of rotation and stable cutting can be performed. In order to make it approximately f-shaped, the ball blade is smoothly connected from the outer peripheral blade, and the ball blade portion is provided with a bulge so as to come to a position of 15 to 35% of the blade diameter and 40 ° to 50 ° R of the ball blade. With the f-shape, sufficient cutting edge strength can be maintained even at low speeds.

Next, the effect can be further enhanced by using an ultrafine particle cemented carbide with a hard film coated on the tool material. In particular, the adhesion between ultra-fine particles cemented carbide and a hard film is good, the friction resistance of the hard film is small, and the characteristics of excellent welding resistance are utilized, and the rake face receives chips when the rake angle is negative. Therefore, the hard film is less likely to be chipped or peeled. Further, as the film quality, a TiN coating which has been put into practical use is sufficient, but TiCN and TiN-Al are used to further improve wear resistance.
Even a film of N or the like can be sufficiently used as long as it has a low affinity for chips.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 3 to 5 show an embodiment of the present invention. The cutting edge has a right-handed and left-handed twist, and is a cross section perpendicular to the axis of the outer peripheral blade.
At -2, the rake angle of the outer peripheral cutting edge is -2
0 °, clearance angle is 10 °, the core thickness of the blade is set to 85% of the tool blade shape, that is, 8.5 mm, and the blade is smoothly connected to the cutting edge of the ball to make the rake angle of the ball blade negative. It has been set. A comparison was made between a product of the present invention in which a cemented carbide was used as a material and a TiN coating was applied to the surface thereof and a conventional cemented carbide ball end mill shown in FIG. 1 by cutting a die material prehardened steel having a hardness of HRC40. Cutting speed is 100 mm / min, feed amount is 0.15 mm / blade, cutting is 0.5 to 3 mm in axial direction, pick feed is 1 mm,
FIG. 6 shows the result of testing by copying cutting with a tool protrusion amount of 50 mm.

In the conventional cemented carbide ball end mill, chattering occurs in a portion having a large cutting depth due to the profile cutting, and the cutting edge of the ball portion is chipped violently after cutting 10 m, whereas the product of the present invention also causes chattering and vibration. Even after a small 50 m cutting, normal wear was shown and no chipping was observed.

[0014]

As described above, according to the present invention, in order to improve the performance of the ball end mill having a long tool protrusion amount and using only the tip, the outer peripheral blade portion has a high rigidity and the edge strength of the ball blade portion is increased. A high-performance, general-purpose ball end mill was obtained by making the rake negative in order to raise it, and by providing a bulge so that the ridge of the ball blade has a substantially f-shape to cushion the impact when biting.

[Brief description of drawings]

FIG. 1 is a front view showing an example of a conventional product.

FIG. 2 is a bottom view of FIG.

FIG. 3 shows an embodiment of the present invention and shows a side view thereof.

FIG. 4 shows a bottom view of FIG.

5 is a sectional view of the blade portion of FIG.

FIG. 6 is an explanatory view showing the cutting effect of the product of the present invention.

[Explanation of symbols]

 1 body 2 cutting edge 3 ball cutting edge 4 bulge θa helix angle θr rake angle θc clearance angle

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Keiji Ishikawa 1-13-20 Nonakakita, Yodogawa-ku, Osaka City Hitachi Tool Co., Ltd. Osaka Plant (72) Inventor Osamu Goto 1-13-1 Nonakakita, Yodogawa-ku, Osaka City No. 20 Hitachi Tool Co., Ltd. Osaka Plant

Claims (2)

[Claims] 1. A ball comprising a plurality of cutting edges having twists formed on the outer periphery of a tool body, and a ball having one or more pairs of grooves and a pair of cutting edges having a ball-shaped cross section at the tip of the grooves. In the end mill, the rake angle of the outer peripheral cutting edge in the cross section perpendicular to the axis of the blade is set to -29 ° to 0 °,
And, the core thickness of the blade portion is in the range of 70 to 90% with respect to the tool blade diameter, and the ball blade has a cutting blade rising portion near the center of rotation, and the cutting blade rotates in bottom view. Since the shape is approximately f-shaped with respect to the center, the blade diameter is 15 to 3
5%, a ball end mill having a bulge at a position of 40 ° to 50 ° R of a ball blade. 2. The ball end mill according to claim 1, wherein Al, Si, carbides, nitrides, oxides and borides of transition metals of Group 4a, 5a and 6a of the periodic table, boron carbide and hard boron nitride, Hard carbon, and one or more hard substances selected from the group consisting of solid solutions or mixtures thereof in a single layer or a multi-layer structure of 0.2 to 0.2
A ball end mill characterized by being coated with a thickness of 20μ.