JP2607293Y2 - Ball end mill - Google Patents

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 which has low resistance to cutting chips and has no vibration even when used at a high cutting speed.

[0002]

2. Description of the Related Art Ball end mills are widely used for processing dies and various parts. In particular, rough cutting with a large cutting amount is performed as the first step of the cutting process, and the ball end mill for rough cutting is required to have no chatter even with a large cutting amount and cutting speed.

[0003] As a conventional ball end mill, there is no one that can sufficiently respond to a cutting speed at a high feed rate. The cause may be that the resistance due to the cutting powder is large. Another reason is that the cutting edge at the axis is easily chipped because the peripheral speed is zero.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a ball end mill having at least two blades which has little resistance due to cutting chips and has no chatter even at a large cutting amount and cutting speed.

[0005]

Means for Solving the Problems As a result of intensive research in view of the above-mentioned object, the present inventor has widened the gash,
By finding that the tip has a polygonal shape, it is possible to reduce the resistance due to the cutting chips, and it has been found that chipping is less likely to occur by removing the center cutting edge from the axis.

That is, in the ball end mill having at least two blades of the present invention, each bottom blade has a polygonal line having 3 to 16 sides .
Configured Rutotomoni, center and edge is formed so as to connect the leading end of the end cutting edge and flank a plurality of polygonal Ri
It is characterized by being formed by a shape .

[0007]

FIG. 1 shows a side view of a two-blade ball end mill according to an embodiment of the present invention, and FIG. 2 shows the ball end mill viewed from the tip. As shown in FIG. 2, the ball end mill of this embodiment has two blades, and each bottom blade 21 has a gash 22, a first flank 23, a second flank 24, and a center cutting edge 25.

As shown in FIG. 2, the gash 22 at the tip of the ball end mill is formed into a curved surface. The two bottom blades 21 have a curved shape when viewed from the tip. FIG. 3 shows a bottom blade projection view in the XX ′ direction in FIG.
The left and right sides of the point C represent different bottom blades. In the ball end mill of the present invention, at least the bottom blade at the tip is formed in a polygonal line shape as shown in FIG. By making the tip part polygonal, that is, the flank is
By forming with a square shape, the resistance due to cutting chips can be reduced. The number of sides of the bottom blade is preferably 3 to 16, more preferably 4 to 10. The adjacent angle of the dotted line connecting the center O and each vertex shown in FIG. 3 is preferably 5 ° to 45 °. In particular, the angle is preferably set to 10 ° to 30 °.

The rake angle changes almost continuously from plus to minus from points A and B on the outer periphery to point C at the tip shown in FIG. FIG. 4 is a schematic diagram showing the change in the rake angle from point A to point C and from point B to point C. If the rake angle changes continuously, it may change linearly or may change in a curve. The position where the rake angle becomes 0 ° is determined from the position by a continuous line with the center O in FIG.
Is determined to be −6 ° to 15 °.

Regarding the rake angle, the size at point C (minimum point) is -3 ° to -10 °, preferably -6 ° to -1.
0 °, and the magnitude at points A and B (maximum points) is +0
° to + 15 °, preferably + 3 ° to + 10 °. The rake angles at points A and B may be the same or different.

In FIG. 3, the shapes of the two bottom blades shown on the left and right of the center line are not symmetric even if the position of the point C is not matched. In the present invention,
It is preferable that the shapes of the both bottom blades in the projection of FIG. 3 are not symmetrical. Especially polygonal vertices of one of the end cutting edge is present in the cross section such that the same as the apex of the polygonal bottom edge of the counterpart, the chatter tends to occur undesirably.

The vertices C at the most distal ends of both the gashes are separated from the center line 32 as shown in FIG. A central cutting edge is formed so as to connect the topmost vertices of the two gashes. As shown in FIG. 2, the center cutting edge 22 does not pass through the axis 25. Although it depends on the size of the end mill, the distance from the axis 25 to the center cutting edge 22 is 1/100 to 8/10.
It is preferably 0 (mm). The length of the center cutting edge is preferably 1/20 to 1/3 of the blade diameter of the ball end mill, particularly preferably 1/20 to 1/10 of the blade diameter.

The bottom edge of the ball end mill of the present invention can have only the first flank or the first flank and the second flank. FIG. 2 shows an example having a first flank 23 and a second flank 24. If you have only the first flank,
Preferably, the first clearance angle is between 6 ° and 12 °. When the first flank and the second flank are provided, the first flank is preferably set to 6 ° to 12 °, and the second flank is set to 15 °.
It is preferable that the angle is set to 20 °.

The width of the flank of the bottom blade is shortest at point C in FIG. 3 and widest at points A and B. The width of the flank at point C is 1/20 to 1/3 of the diameter of the ball end mill, preferably 1/10 to 1/5 of the diameter. The width of the flank at points A and B is 1 of the circumference of the end mill cross section.
５〜 to １ ／, preferably １ ／ to ３.

The depth of the gash of the bottom blade is 0.3 to 1.0.
mm, and preferably 0.3 to 0.6 mm. The torsion angle of the cutting edge is 10 ° to 40 °, preferably 25 °.
３５35 °. Under such conditions, the ball end mill of the present invention can have a wide gash surface and can efficiently discharge chips.

The present invention is applicable not only to a two-flute ball end mill but also to a four-flute ball end mill, for example.

The reason why the above-mentioned effect is obtained in the present invention is not always clear, but by making the tip a polygonal shape and widening the gash, it is possible to discharge the chips naturally without forcibly discharging chips as in the conventional case. By doing so, it is considered that the resistance due to the swarf is reduced and high-speed cutting becomes possible.

If the ball end mill of the present invention is used, 2
It can be cut at a speed of 000 rpm, and when a work material made of a steel material such as Cr-Mo steel is cut with the same cutting amount and cutting speed as compared with a conventional ball end mill, the life is 2. Up 5 times or more.

[0019]

As described in detail above, since the ball end mill of the present invention has a polygonal tip and a wide gash, there is no chatter even at a large cutting amount and cutting speed. In addition, since the chips are scattered well and chipping of the cutting edge due to biting of the chips is prevented, the life is significantly increased. Such a ball end mill is particularly suitable for rough cutting.

[Brief description of the drawings]

FIG. 1 is a side view showing a ball end mill according to an embodiment of the present invention.

FIG. 2 is a plan view showing a tip of the ball end mill of FIG. 1;

FIG. 3 is a projection view of the bottom blade of the ball end mill of the present invention in the XX ′ direction of FIG. 2;

FIG. 4 is a schematic view showing a change in a rake angle of a bottom blade of a ball end mill.

[Explanation of symbols]

 11, 21 ... bottom blade 12, 22, 31 ... gash 23 ... first flank 24 ... second flank 25 ... center cutting edge 32 ... center line

Claims (6)

(57) [Scope of request for utility model registration] 1. A ball end mill of at least two blades, each end cutting edges are formed by polygonal line side number 3-16
And the central cutting edge is formed so as to connect the tip of the bottom blade , and the flank is formed by a plurality of polygons.
A ball end mill characterized by being formed . 2. The ball end mill according to claim 1, wherein the rake angle of the bottom blade changes substantially continuously from minus to plus from the tip of the end mill to the outer periphery. 3. The ball end mill according to claim 1, wherein the shape of the bottom blade is the same as that of the ball end mill.
Ball end mills that are not symmetrical about the axis . 4. The ball end mill according to claim 1, wherein a distance from the center cutting edge to the axis is 1/100 to 8/100 (mm). . 5. The ball end mill according to claim 1, wherein the rake angle at the tip is −
A ball end mill, which is 3 ° to -10 ° and 0 ° to 15 ° at an outer peripheral portion. 6. The ball end mill according to claim 1, wherein the length of the center cutting edge is 1/20 to 1/3 of the blade diameter of the end mill.