JPS6332564B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a ball end mill, and particularly for small diameter ones, by adopting a rational cutting edge configuration, stable cutting can be ensured and accuracy can be maintained by re-grinding. It is.

Conventionally, this type of ball end mill, especially the small diameter solid carbide ball end mill, has many symmetrical two-flute blades, and the chip pocket in the center is small, so it has poor chip evacuation and is prone to chipping in practical use. had. Furthermore, it was not possible to perform sufficient cutting on difficult-to-cut materials such as SKD11 and SUS304 due to the aforementioned chip evacuation and cutting blade configuration.

On the other hand, as small-diameter ball end mills are increasingly used for mold machining, there is a growing demand for the development of ball end mills that can improve cutting efficiency and can be applied to difficult-to-cut materials.

For these reasons, it is desired to provide a small-diameter ball end mill that can solve the above-mentioned problems from the viewpoint of developing a highly tough cemented carbide and improving the cutting edge configuration.

The present invention was made with a focus on improving the cutting blade configuration, and the hemispherical side of the tip of the cylindrical main body has a
An arc-shaped cutting edge is formed by the intersection of the curved rake face and flank face, and this cutting edge is configured for cutting hemispherical parts by locating the starting point of the cutting edge near the center of rotation. It provides a ball end mill with a

That is, the curved rake face passes through the center point O ₁ on the shaft center line that constitutes the cutting edge radius R, and is located on the shaft center line, with reference to the direction in which the cutting edge ridge exhibits _a straight line. It is constituted by a part of the conical surface of a virtual cone determined by the vertical reference line forming an inclination angle α between the center point O and the starting point of the cutting edge of the cutting edge that presents a straight line; On _{the first} side, a concave chip pocket is arranged in series.

In addition, when viewed from a direction in which the cutting edge has an arc shape due to the curved rake face, the cutting edge angle θ of the arc from the cutting edge starting point A to the ending point B is set within the range of 90° to 150°. It is something that

Furthermore, the hemispherical side portion of the tip of the main body forms a removal end in which about half of the side opposite to the cutting edge is cut out when viewed in a direction in which the cutting edge is straight; The chip space in the axial direction with respect to the curved rake face including the blade starting point A constitutes the chip space.

Hereinafter, one embodiment of the ball end mill of the present invention will be described with reference to the drawings.

In FIGS. 1 to 3, reference numeral 1 denotes a ball end mill integrally formed of, for example, cemented carbide, and the diameter of its cutting edge is generally about 3 to 10 mm. A cutting edge portion 3 is formed on the hemispherical side of the tip of the cylindrical main body 2.

The cutting edge 6 of the cutting edge portion 3 extends from the starting point A of the cutting edge near the center of rotation toward the ending point B in the diagonal direction when viewed in a straight line direction as seen in FIG. As shown in FIGS. 2 and 3, the conical curved rake face 7 forms a three-dimensional arc shape that creates a hemispherical surface by cutting.

The configuration of this cutting edge 6 is that if a sphere 50 is cut along a certain plane 51 as shown in FIGS. It is based on the fact that a cone 53 is formed by connecting the center points O of 50, and that if the obtained circular ridgeline 55 is rotated about the center line 54, a hemispherical surface for the hatched part is formed. That is, based on this virtual cone, the conical surface is the curved rake face 7, the circular ridgeline is the cutting edge edge,
The idea is to use the conical bottom side as the relief surface 8. In the case of FIG. 1, with respect to the axis center line 4,
Place the cutting edge 6 at a linear inclination angle (90°-α),
Assuming a virtual vertical reference line 5 at an angle of α,
If we consider a cone having its apex at the intersection of the vertical reference line 5 and the axis center line 4, a cutting blade configuration having a constant cutting edge radius R can be obtained. Therefore, the cutting edge radius R
The center point O ₁ of is the intersection point mentioned above. in this case,
The angle of α is set, for example, in the range of 45° to 75°,
The inclination angle (90°-α) of the cutting edge 6 relative to this is:
The angle will be between 25° and 45°.

In addition, the cutting edge 6 is, as seen in FIG.
The cutting edge starting point A is located near the center of rotation and forms a cutting edge angle θ between the cutting edge starting point A and the ending point B. This angle θ is set in the range of 90° to 150°. This is because it is preferable that the depth of cut into the work material be smaller than the radius R of the cutting edge.

Furthermore, the conical curved rake face 7 formed on the cutting edge portion 3 is based on a part of the conical face, as described above. Therefore, if grinding is performed from the side of the flank 8, a three-dimensional arcuate cutting edge 6 that can always create a spherical surface is formed. In this case, the conical curved rake face 7 is provided with a concave chip pocket 9 on the side of the center point _O1 described above, which improves chip removal. Further, in order to further improve chip removal, a removal end is formed on the hemispherical side of the tip of the main body 2 so that about half of the side opposite to the cutting edge 6 is cut out when viewed in a direction in which the cutting edge 6 is a straight line. 10 is formed. Along with this, a chip space in the axial direction with respect to the curved rake face 7 including the cutting edge starting point A is formed.

In addition, when considering the strength of the cutting edge on the flank 8 side,
It is not necessary to grind down to the conical bottom surface, and in this embodiment, it is formed as a belt-shaped surface constituting the primary flank surface within the range of providing a relief angle.

Further, FIGS. 5 to 7 specifically show the ball end mill 11 of the brazing type. In this case, a brazed ball end mill 1
1 generally has a cutting edge diameter of 6 mm or more, and the one shown is larger than the solid type mentioned above.

And, on the tip hemispherical side of the steel main body 12,
A chip seat 13 is cut out, and a cutting edge portion 14 is brazed into the chip seat 13. In this case, regarding the configuration of the cutting edge 15, the angle α between the axis center line 16 and the above-mentioned virtual vertical reference line 17 is set to 45 degrees, and the cutting edge angle from the starting point A to the ending point B of the cutting edge 15 is set to 45 degrees. θ is set to 130°.

The flank surfaces 18 and 10 are formed as a band-shaped surface 18a and a circular surface 18b, and a concave tip pocket 20 is provided in series on the center point _O1 side of the curved rake surface 19. Further, as shown in FIG. 5, approximately half of the hemispherical side portion of the distal end of the main body 12 is notched in the axial direction to form a removal end 21, thereby securing space for chips in the axial direction.

(Cutting Example) In the cutting example, the nominal tool diameter of the ball end mill 11 is 16 mmφ, the settings are α=60° and θ=130°, and the work material is S55C. The cutting conditions at this time were rotation speed N = 1000 r.pm, cutting speed V = 50 m/min, feed f = 0.05 mm/rev, depth of cut d = 6 mm, and cutting width (pick feed) PF =
Cut 600mm with 4mm. In this case, flank wear
At V _B =0.1 mm, cutting was still possible.

On the other hand, using a conventional ball end mill with a flat rake face and the same nominal tool diameter (16mmφ), severe vibrations occurred after cutting 300mm, so cutting was stopped. As a result, a chip was found in the center of the cutting edge, making it impossible to cut.

The product of the present invention, which is a solid type with a tool nominal diameter of 6 mm, was applied to SKD11 and SUS304, and it was able to cut satisfactorily. The cutting conditions at this time are cutting speed V = 30 to 50 m/min, feed f
= 0.03 to 0.06 mm/rev, depth of cut d is (1/2 to 1/4) mm of tool nominal diameter, cutting width (pick feed)
PF was (1/2 to 1/4) mm of the tool nominal diameter.

On the other hand, conventional solid carbide end mills with planar rake faces were unable to perform satisfactory cutting.

In the ball end mills 1, 11 constructed in this manner, when re-grinding the cutting edge edges 6, 15, a high degree of roundness can be obtained by removing the flank surfaces 8, 18.

As explained above, the present invention can make the cutting action effective by forming a three-dimensional arcuate cutting edge.
It is also suitable for cutting SUS materials, and has the advantage of improving the sphericity of the workpiece.

[Brief explanation of the drawing]

Fig. 1 is a front view showing an embodiment of the ball end mill of the present invention applied to a small-diameter solid type, Fig. 2 is a bottom view thereof, Fig. 3 is a right side view from an oblique direction, and Fig. 3 is a right side view from an oblique direction. Figures 4a and 4b are diagrams explaining the cutting blade configuration of the present invention, where a is a front view, b is a side view from diagonally below the right side, and Figure 5 is a modified example of the ball end mill of the present invention. Figure 6 is a front view of the main parts applied to the formula, Figure 6 is its bottom view, Figure 7 is
It is a right side view from an oblique direction. 1, 11... Ball end mill, 2, 12... Main body, 3, 14... Blade edge portion, 6, 15... Cutting edge ridge,
7, 19... Rake face, 8, 18... Relief face, 9, 2
0...Chip pocket, 10, 21...Removal end.

Claims (1)

[Scope of Claims] 1. Arc-shaped cutting edge ridges 6, 15 are formed by the intersection of curved rake surfaces 7, 19 and flank surfaces 8, 18 on the hemispherical side portions of the tip ends of the cylindrical main bodies 2, 12. In this ball end mill, the cutting edge edges 6 and 15 are configured for cutting a hemispherical part by locating the cutting edge starting point A near the center of rotation. Axis center lines 4 and 1 are based on the direction in which 6 and 15 are straight lines.
6, a center point O ₁ constituting the cutting edge radius R, a vertical reference line 5, 17 passing through this center point O ₁ and forming an inclination angle α with the shaft center line 4, 16, and the straight line It is constituted by a part of the conical surface of the virtual cone determined by the cutting edge start point A of the cutting edge edges 6, 15, and has concave chip pockets 9, 20 on the center point _O1 side. The cutting edge ridges 6, 15 are connected to the curved rake face 7,
19, the cutting edge angle θ of the arc from the cutting edge starting point A to the ending point B is
The hemispherical side of the tip of the main body 2, 12 is set within the range of 90° to 150°. The removal ends 10, 21 are formed so that about half of them are notched, and a chip space in the axial direction with respect to the curved rake faces 7, 19 including the cutting edge starting point A is formed accordingly. ball end mill.