JPS5828727Y2 - ball end mill - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a ball end mill used for machining or engraving the bottom of a hemispherical or similar hole.

BACKGROUND OF THE INVENTION Conventionally, a ball end mill used for hole bottom cutting or die-sinking has a cutting edge provided at the tip of a tool body.

However, when cutting with this type of ball end mill, the cutting speed differs between the cutting edge on the rotation center line and the outer circumference of the cutting edge because the circumferential speed is different. There are problems such as cutting resistance and cutting edge wear between the ball end mill and its outer periphery, making it impossible to balance the machinability, resulting in poor machinability for the ball end mill as a whole and the cutting speed being forced to be limited. Ta.

This idea was made in view of the above circumstances, and its purpose is to achieve high-speed cutting by making the machinability almost uniform between the part of the cutting edge on the center line of rotation and its outer periphery during cutting. The purpose of the present invention is to provide a ball end mill that can do the following.

Hereinafter, one embodiment of this invention will be described in detail based on FIGS. 1 to 4.

In the figure, reference numeral 1 denotes a tool body, and the tip of this tool body 1 is formed in a semicircular shape, and the center line a
Further, half of the semicircular sphere is formed to be slightly shifted from the center line a, and one side thereof is cut out in a substantially fan-shaped column shape along the center axis a so as to be line symmetrical with respect to the center line a. As a result, cutting edges 2, 2, cutting edge portions 3, 3 each having a rake face and a flank face are formed, and furthermore, pockets 4, 4 for discharging cutting waste are formed at the tip of the semicircular spherical shape.

A breaker groove 5 is formed in the rake surface of the cutting edge 3 along the cutting edge 2 and having a rake angle that gradually decreases from the tip of the center of rotation toward the outer periphery.

That is, the radius of curvature R1tR2 of this breaker groove 5 gradually increases from the tip of the center of rotation of the cutting blade 2 toward the outer circumference (R,≦R2), and the depth H of the breaker groove 5 gradually increases (R,≦R2).
l, H2 gradually becomes shallower (H, > H2).

Furthermore, one side edge 5a of the breaker groove 5 on the cutting edge 2 side is gradually spaced apart from the tip of the rotation center along the cutting edge 2 toward the outside to form a slight flat surface 6.

Note that the slope on the other side edge 5b on the rear side of the breaker groove 5 is formed as a breaker surface that folds back the cutting waste generated by the cutting blade and cuts it finely.

Next, the operation when cutting is performed using the ball end mill configured as described above will be explained.

In FIG. 2, when the tool body 1 rotates in the direction of arrow X (counterclockwise), the cutting blades 2 perform cutting.

At this time, the center of rotation of the cutting blades 2, 2 (point 0 in the figure)
The cutting speed is very close to zero, and the cutting speed at the outer periphery of the cutting edges 2 is faster, but the rake angle gradually decreases from the center to the outer periphery due to the breaker groove 5. Therefore, cutting resistance, cutting edge wear, and other machinability are almost uniform, and as a result, high-speed cutting is possible.

In addition, when continuous cutting is performed using the ball end mill, the depth of the breaker groove 5 is shallower on the outer circumferential side, which distorts the chips, and the other side edge 5b of the breaker groove 5 becomes the cutting edge. The cutting waste produced by steps 2 and 2 is folded back and cut into small pieces to facilitate the discharge of the cutting waste.

Furthermore, a slight flat surface 6 formed along said cutting edge 2.2
This has the effect of preventing wear of the outer circumferential portion of the cutting blades 2, 2 during cutting, and increasing the strength of that portion.

Note that this invention is not limited to the above-mentioned embodiments; for example, as shown in FIGS. 5 and 6, the breaker groove 5 described above is formed in the carbide tip 10° 10 of a ball end mill with a carbide tip. Of course, it can be anything.

In addition, in this case, the length of the carbide tips 10, 10 is set to the sixth
As shown in the figure, the lengths may be different and the portion corresponding to the cutting edge 11 of the cutting blade may be cut with only one blade.

Also, in the above embodiment, each side edge 5a of the breaker groove 5
, 5b are formed in an arc shape, but the present invention is not limited to this. For example, the rake angle of the cutting edges on the rake surfaces of the cutting edges 3, 3 gradually decreases from the tip on the rotation center side toward the outer periphery. It may also be formed into an inclined surface shape.

As explained in detail above, this invention provides a cutting edge portion with a cutting edge at the tip of the tool body, and the rake angle of the cutting edge is directed outward from the tip on the rotation center side on the rake face of this cutting edge portion. Since it is a cross-cut with a breaker groove that gradually becomes smaller, even if the cutting speed of the part of the cutting blade on the rotation center line of the cutting blade and its outer circumferential part is different, cutting resistance, edge wear, etc. in each part will be reduced. As a result, compared to conventional ball end mills, the cutting speed, especially when cutting steel materials, can be improved, which is an excellent effect.

[Brief explanation of drawings]

Fig. 1 is a side view showing an embodiment of this invention, Fig. 2 is a front view thereof, Fig. 3 is a sectional view taken along the line ■-■ in Fig. 1, and Fig. 4 is a TV-- FIG. 5 is a sectional view taken along the TV line, FIG. 5 is a side view showing another embodiment, and FIG. 6 is a front view thereof. 1... Tool body, 2... Cutting blade, 3... Cutting blade part, 5
...flaker groove.

Claims (1)

[Scope of utility model registration request] A cutting edge portion having a cutting edge is provided at the tip of the tool body, and a breaker groove is formed on the rake surface of this cutting edge portion in which the rake angle of the cutting edge gradually decreases from the tip on the rotation center side toward the outer circumference. Characteristic ball end mill.