JPH07204920A - End mill - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide an end mill capable of reducing the excessive load, extending the tool life, and performing stable machining when digging into a flat workpiece. [Constitution] An end mill in which a cavity 1 is provided around the center of the bottom blade 3 where the peripheral speed is zero, and an inner peripheral blade 2 is provided on the inner side surface of the cavity 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an end mill which is a cutting tool used in a milling machine, a machining center or the like.

[0002]

2. Description of the Related Art Conventional end mills are described, for example, in All of End Mills, edited by Tool Engineering, Taiga Publishing Co., Ltd., pages 140 and 146 (published June 1, 1988). An outer peripheral blade was provided on the outer periphery of the body, and a bottom blade was provided on the bottom.

FIG. 9 is a side view and a bottom view of an example of a parent-child blade end mill. When using this parent-child blade end mill to process the key groove 9 on the flat work material 10 as shown in FIG. 3, the end mill 11 is rotated clockwise as shown in FIG. Axial direction 12 with the bottom blade 3 shown
Then, the end mill was fed in the lateral direction 13 and the outer peripheral blade 4 was used for cutting.

[0004]

SUMMARY OF THE INVENTION In the above-mentioned prior art, when cutting into a flat work material in the axial direction, the peripheral speed of the center of the bottom blade of the parent-child blade end mill is zero. I haven't. Therefore, an excessive load is generated on the end mill, the work material, and the processing device, chatter is generated, the corner of the end mill is chipped, the bottom blade is greatly worn, and the tool life is significantly reduced. there were. In addition, the work piece may come off the chuck jig, or the spindle may stop in a processing device with low spindle power.

In order to prevent such a situation, when machining a deep keyway or the like, a pilot hole is drilled in advance,
The method of cutting from the center was also performed. In this method, the central portion of the bottom blade where the peripheral speed is zero does not come into contact with the work material, so that an excessive load does not occur. However, it requires two tools, a drill and an end mill, which is troublesome.

An object of the present invention is to provide an end mill that does not generate an excessive load when digging a flat work material.

[0007]

In order to achieve the above object, the end mill of the present invention is provided with a cavity at the center of the bottom blade and a cutting function on the inner side surface of the cavity. The diameter of the circle that connects the inside of the inner peripheral blade, that is, the distance between the inner peripheral blades that face each other when the number of the inner peripheral blades is even, is about 0.1 to 0.8 times the outer diameter of the end mill. The outer diameter is preferably 0.4 times to 0.7 times the outer diameter. This is because if the cavity depth and the diameter are increased, the rigidity of the bottom blade is reduced, and if the diameter is small, it is difficult to form the inner peripheral blade. Further, it is preferable that the inner peripheral blade and the bottom blade are formed continuously.

[0008]

When there is no portion where the peripheral speed of the bottom blade becomes zero when the end mill makes a cut in the workpiece in the axial direction, an excessive load is eliminated and the tool life is extended. Further, in the case of even-numbered blades, if each cutting edge is symmetrical with respect to the central axis, and in the case of three or more odd-numbered blades, the cutting edge has the same shape, so that the balance during high-speed rotation is extremely improved. The parent-child blade end mill shown in FIG. 9 is asymmetric with respect to the central axis, and therefore is not well balanced during high-speed rotation. In addition, if the inner peripheral blade inside the cavity cuts in the axial direction and then feeds in the lateral direction, the uncut remaining portion in the center can be cut, and the same use as an ordinary end mill can be performed.

[0009]

Embodiments of the present invention will be described below with reference to FIGS. 1 to 8. 1 and 2 are a side view and a bottom view of a two-blade and four-blade end mill according to an embodiment of the present invention, respectively. The bottom blade 3 has a cavity 1 in the center thereof, and the inner side surface of the cavity 1 has an inner peripheral blade 2 continuous with the bottom blade 3. The shapes of the bottom blade 3 and the outer peripheral blade 4 are symmetrical. The bottom blade middle low angle 8 is usually 2 to 3 °, but 0 to 1 ° is suitable for the end mill of this embodiment. This is because if the bottom blade middle low angle 8 is large, a load is applied to the corners of the bottom blade 3 and the outer peripheral blade 4 and the chips are easily chipped.

Here, the cavity depth 7 is about 1 to 2 mm in an end mill having an outer diameter 5 of φ10 mm or less, and φ1.
When it is 0 to 20 mm, it is preferable to set it to about 2 to 3 mm. The inner diameter 6 of the inner peripheral blade 2 is 0.1 to 0.8 times the outer diameter 5.
The outer diameter is preferably about double, more preferably about 0.4 to 0.7 times the outer diameter 5. This is because when the cavity depth 7 and the inner diameter 6 are increased, the rigidity of the bottom blade is reduced, and when the inner diameter 6 is small, it is difficult to form the inner peripheral blade 2.

Next, description will be made on a case where this end mill is mounted on a machine tool such as a milling machine or a machining center where tools rotate. Flat workpiece 1 shown in FIG.
When the key groove 9 is machined by using an end mill having an outer diameter of φ5 mm, first, as shown in FIG.
Cut to a depth of 1.7 mm. The cavity makes it possible to avoid hitting the workpiece. Figure 5
Fig. 6 is a partial plan view of the work material in that state.
5 shows a sectional view taken along line II of FIG. In this state, the bottom blade cutting portion 15 is cut, and the uncut portion 14 remains in the center.

Next, as shown in FIG. 7, if the end mill is sent in the horizontal direction 13 as it is, the outer peripheral blade cutting portion 17 is cut by the outer peripheral blade and the inner peripheral blade cutting portion of the uncut portion 14 is cut by the inner peripheral blade 2. 16 can be cut. If the end mill is fed in the lateral direction 13 more than the inner diameter 6 of the inner peripheral blade 2, the uncut portion 14 can be completely cut and the outer peripheral blade 4 can be processed like a normal end mill, as shown in FIG. When processing a deep keyway, the above may be repeated.

The axial depth of cut is preferably 0.3 to 0.5 mm less than the cavity depth 7. This is because if the cutting amount is increased, the chips cut by the inner peripheral blade 2 are clogged in the gap between the uncut portion 14 and the cavity 1. Further, when carrying out the pocket processing, as in the case of processing the key groove 9, it is sufficient to continuously feed the feed in the lateral direction 13 by changing the direction. Such a machining method is particularly suitable for high-feed high-speed machining with a relatively shallow depth of cut such as found in a high-speed machining machine.

Besides this, side surface processing and front surface processing are also possible,
It can be used like a normal end mill. If the outer diameter 5 of the end mill, the cavity depth 7 and the inner diameter 6 of the inner peripheral blade 2 are defined and only the cutting in the axial direction 12 is performed, only the bottom blade cutting portion 15 shown in FIG. It is possible to easily process the insertion groove and the like.

Further, not only the two-blade and the four-blade, but also a single-blade and a multi-blade end mill can have the same shape. In order to improve the balance during high-speed rotation, in the case of even-numbered blades, each cutting edge may have a symmetrical shape with respect to the central axis, and in the case of three or more odd-numbered blades, the same shape may be used.
That is, the use of the end mill of the present invention enables stable digging and is very effective in high-speed high-feed machining with shallow cuts.

[0016]

According to the present invention, the tool life is 2 times that of the conventional one.
~ 3 times longer, and the processing accuracy is 10 µm or less. Especially when rotating at high speed, the balance is good, so there is little vibration,
The effect becomes even clearer. When applied to mass production processing, 1
With this end mill, roughing to finishing can be performed, and the number of tools is reduced. Further, it is possible to perform stable machining even with a machining device having a small spindle power, so that the effect is extremely large.

[Brief description of drawings]

FIG. 1 is a side view and a bottom view of a two-blade end mill according to an embodiment of the present invention.

FIG. 2 is a side view and a bottom view of a four-blade end mill according to an embodiment of the present invention.

FIG. 3 is a perspective view of a workpiece for explaining processing using an end mill.

FIG. 4 is a perspective view of a workpiece for explaining processing using an end mill.

FIG. 5 is a partial plan view of a workpiece for explaining the processing by the end mill of the present invention.

6 is a cross-sectional view taken along the line I-I of the work material shown in FIG.

FIG. 7 is a partial plan view of a workpiece for explaining the processing by the end mill of the present invention.

FIG. 8 is a partial plan view of a workpiece for explaining the processing by the end mill of the present invention.

FIG. 9 is a side view and a bottom view of a conventional parent-child blade end mill.

[Explanation of symbols]

 1 ... Cavity 2 ... Inner peripheral blade 3 ... Bottom blade 4 ... Outer peripheral blade 5 ... Outer diameter 6 ... Inner diameter 7 ... Cavity depth 8 ... Bottom blade middle low angle 9 ... Key groove 10 ... Workpiece material 11 ... End mill 12 ... axial direction 13 ... lateral direction 14 ... uncut portion 15 ... bottom blade cutting portion 16 ... inner peripheral blade cutting portion 17 ... outer peripheral blade cutting portion

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideaki Sasaki 1 Horiyamashita, Hadano City, Kanagawa Prefecture

Claims (1)

[Claims] 1. An end mill having a cavity at the center of a bottom blade and a cutting function provided on the inner side surface of the cavity.