JPH0112893Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an improvement of a ball end mill.

[Prior Art] Conventionally, in the most commonly used so-called one-cut end mill, the tip cutting edge is formed to extend linearly outward in the radial direction from the tool rotation center when viewed from the tip in the axial direction of the tool. was. In this case, since the cutting speed of the tip cutting edge at the tool rotation center is 0, the cutting resistance is particularly large during axial plunge cutting, and the cutting edge near the tool rotation center is severely seized and worn. There was a problem with the short lifespan.

In order to prevent this, a so-called spiral-blade ball end mill has recently been developed in which the tip cutting edge is spirally extended from the center of rotation of the tool toward the outer periphery when viewed from the tip in the axial direction of the tool.

[The problem that the idea aims to solve]

According to the above-mentioned spiral blade ball end mill, the life of the cutting edge near the center of rotation of the tool can be improved; however,
The tip of the cutting edge has a spiral bottom shape, and
Since the side surface shape is an arcuate curve, it is difficult to form the cutting edge, that is, grind and re-grind, and a special grinding machine dedicated for this purpose is required.

The present invention was developed to solve these problems, and it improves tool life by minimizing seizure, wear, and damage to the cutting edge near the center of rotation of the tool. Another object of the present invention is to provide a ball end mill that facilitates re-grinding and improves mass productivity.

[Means to solve the problem]

In order to achieve the above object, the ball end mill of the present invention has a pair of cutting blades, one cutting blade has its starting end near the tool rotation center, and the other cutting blade has its cutting edge starting point near the tool rotation center. The two cutting edges are located at a farther apart position and include a linear cutting edge that extends obliquely from the starting end of the cutting edge toward the front of the tool rotation when viewed from the tip in the axial direction of the tool, and a linear cutting edge that extends from the end of the linear cutting edge to the outer periphery of the tool. The cutting edge is provided with an arcuate cutting edge whose rotation projection surface is spherical, and each arcuate cutting edge is formed by an arcuate flank face and a flat rake face inclined at a predetermined helix angle in the direction of the tool axis. , each linear cutting edge has a flat inclined rake face that intersects at a predetermined angle of inclination in the radial direction with respect to the rake face of the arcuate cutting edge;
It is characterized in that it is formed by a flank continuous to the arcuate flank.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1 is a shank with a tip 11 formed in a spherical shape, and a pair of chip discharge grooves 12, 1 on the circumferential surface of the tip.
3 are provided almost symmetrically. 2 and 3 are carbide tips, and arcuate flanks 26 and 3 are provided on the outer periphery of the tips.
6 is formed and is fixed by brazing at a predetermined twist angle α to the side surface of each of the chip discharge grooves 12 and 13 on the rear side of the rotation of the tool. The chips 2 and 3 may be replaceably attached to the shank 1 using clamp bolts or the like, or may be of a solid type.

At the tips and outer sides of both chips 2 and 3,
Linear cutting edges 21, 31 and arcuate cutting edges 22, 32 for cutting the bottom surface, and linear cutting edges 23, 33 for cutting the circumferential surface are provided, respectively.

However, the linear cutting edge 21 at the tip of one chip is formed by a rake face 24 and a flank face 26, and when viewed from the tip in the tool axis direction (hereinafter referred to as bottom view), the starting edge 20 of the cutting edge is It is located near the tool rotation center 0, and is formed so as to extend in a straight line at an inclination angle β from the cutting edge starting end 20 toward the front of the tool rotation. In this case, the distance l between the cutting edge starting end 20 and the tool rotation center 0 is set to 0 to 2.5 mm so that the non-cutting part (core) near the tool rotation center during cutting is as small as possible. Further, if the inclination angle β of the linear cutting edge 21 is too small, the chip discharge efficiency will be poor, and if it is too large, the cutting resistance will increase, so β = 0 to 50°. moreover,
The rake face 24 of the linear cutting edge 21 is inclined at the inclination angle β when viewed from the bottom on the front side of the chip 2,
The flat surface is inclined at a predetermined axial rake angle γ with respect to the axial direction, and while ensuring a certain level of height h at the starting end of the cutting edge, the height h' increases toward the end of the cutting edge. do.

In this way, by making the rake face 24 a flat surface, it is possible to easily grind the rake face 24 near the center of rotation of the tool and to form the linear cutting edge 21, and the height of the rake face 24 can be easily By gradually increasing h to h' from the starting end to the end of the cutting edge, even if there is no overhang on the chip 2 during re-grinding, it is possible to easily grind the linear cutting edge 21 and the arcuate cutting edge 22. It can be carried out. Furthermore, the flat rake face 24 allows the axial rake angle α of the linear cutting edge 21 to be arbitrarily set within a wide range of -15 to 20 degrees depending on the workpiece material.

Note that the linear cutting edge 31 at the tip of the other tip is
It is formed by a rake face 34 and a flank face 36, and when viewed from the bottom, its cutting edge starting end 30 is located at a position away from the tool rotation center 0, and the cutting edge starts from the cutting edge starting end 30 toward the front of the tool rotation. It extends in a straight line with an inclination angle β' that is approximately the same as the angle β. In this case, the rake face 34 of the cutting edge 31 is also
Form into the same shape as 4. However, the distance l' between the cutting edge starting end 30 and the tool rotation center 0 is such that when a core is generated near the tool rotation center during cutting with the linear cutting edge 21, the core can be easily ejected, and each straight line In order to make the grinding of the shaped cutting edges 21 and 31 easier, the distance is larger than the above-mentioned interval l, and l'=0.5 to 0.5.
Set to 8.0mm.

Each of the arcuate cutting edges 22, 32 is formed by a rake face 25, 35 formed on the front surface of the chip and an arcuate relief surface 26, 36 formed at the tip end of the chip, and each of the linear cutting edges 22, 32 is Point 0' on the tool axis C extending from the end of the cutting edge of the blades 21 and 31 to the outer circumference of the tool
It is curved with a radius R around , and its rotational projection surface is formed into a spherical curve. In this case, since the arcuate cutting edges 22, 32 are spherical starting from the ends of the linear cutting edges 21, 31 that are far away from the tool rotation center, they can be formed as easily as or more easily than conventional ball end mills. Furthermore, by making the linear cutting edges 21, 31 longer, the axial rake angle of the arcuate cutting edges 22, 32 can be increased, reducing the mechanical shock at the point of cutting during cutting, and reducing the mechanical impact during one rotation of the tool. This increases the rotational angle at which the cutting edge cuts into the workpiece, reducing thermal shock.

Further, each linear cutting edge 23, 33 is linearly extended upward from the terminal end of the curved cutting edge 22, 32 at the twist angle α. This cutting blade 23,3
There are no particular problems with the processing in step 3.

[Effect of idea]

As explained above, according to the ball end mill of the present invention, the tool tip has two types of flat rake faces with a straight cutting edge that extends obliquely toward the front of the tool rotation with the cutting edge starting point near the tool rotation center. Since the cutting edge starts at a point far from the tool rotation center and has a linear cutting edge that extends obliquely toward the front of the tool rotation, there is no need for a special grinder like with conventional spiral-blade ball end mills. , each rake face can be easily ground with a normal grinding machine, and each linear cutting edge can be easily formed, improving mass productivity and significantly reducing costs. In addition, regrinding is easy, increasing the number of times regrinding is used, and is very economical. Moreover, during cutting with this tool, it is difficult to form a so-called core at the center of rotation of the tool, and even if a core does form, the distances between the linear cutting edges from the center of rotation of the tool are unequal, so that the core is difficult to form. It is easy to break and be ejected, and it is possible to prevent chips from seizing or getting caught near the center of rotation of the tool, and also to prevent wear and damage to the cutting edge, thereby extending the tool life. Furthermore, the inclined linear cutting edge as described above can improve the cutting efficiency near the tool rotation center and the evacuation efficiency of chips, and the cutting ability is not reduced in axial thrust cutting. , the finished surface roughness is improved even in cross-feed cutting, and high-precision cutting is always possible. It has great practical effects.

[Brief explanation of the drawing]

Fig. 1 is a front view of essential parts showing an example of a ball end mill according to the present invention, Fig. 2 is a bottom view thereof, Fig. 3 is a partial side view thereof, and Fig. 4 shows the shape of the cutting edge near the center of rotation of the tool. The enlarged bottom view shown in FIG. 5 is a perspective view of the same portion. 1...shank, 2, 3...carbide tip, 0...
... Tool rotation center, 20, 30 ... Cutting edge starting end, 2
1, 31... linear cutting edge, 22, 32... arcuate cutting edge, 24, 34... flat rake face, 2
5, 35...Flat rake face, 26, 36...
...Arc-shaped relief surface.

Claims (1)

[Scope of utility model registration request] It has a pair of cutting edges, one cutting edge has its starting edge near the tool rotation center, the other cutting edge has its cutting edge starting edge located away from the tool rotation center, and both cutting edges are When viewed from the tip in the tool axis direction, there is a linear cutting edge that extends obliquely from the starting end of the cutting edge toward the front of the tool rotation, and an arcuate cutting edge that extends from the end of the linear cutting edge to the outer periphery of the tool and has a rotational projection surface that is spherical. Each arcuate cutting edge is formed by an arcuate flank and a flat rake face inclined at a predetermined helix angle in the direction of the tool axis, and each linear cutting edge is formed by the arcuate cutting edge. A ball end mill characterized in that it is formed by a flat inclined rake face that intersects the rake face in the radial direction at a predetermined angle of inclination, and a flank face that is continuous with the arcuate flank face.