JPS6332565B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a solid type ball end mill, and particularly to a two-flute ball end mill in which a main cutting edge ridge and a minor cutting edge ridge are respectively formed so as to improve cutting performance. Conventionally, this type of ball end mill, especially solid carbide ball end mills, often had two symmetrical blades and a small diameter, so the chip pocket in the center was small and the helix angle was small. .
Therefore, there was a problem in that the chip dischargeability was poor and chipping was likely to occur in practical use. Also, SKD11 and
For high-hardness materials such as SUS304, difficult-to-cut materials, etc., it was not possible to perform sufficient cutting 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 has been made in view of the above-mentioned points, and has an arc-shaped main cutting edge ridge formed by the intersection of a curved rake face and a flank face on the hemispherical side of the tip of the cylindrical main body. The main cutting edge is configured for cutting hemispherical parts by locating the starting point of the cutting edge near the center of rotation, and also has a cutting edge offset of about 180° in the circumferential direction based on the cutting edge starting point of the main cutting edge. In a solid-type ball end mill in which a secondary cutting edge ridge is formed at the position for cutting the hemispherical part and then for cutting the outer peripheral part, the main cutting edge ridge and the secondary cutting edge ridge each have an effective cutting action. The cutting edge configuration has been improved to achieve this. Hereinafter, one embodiment of the solid type ball end mill of the present invention will be described with reference to the drawings. In Figs. 1 to 6, reference numeral 1 denotes the body of a solid type ball end mill having a cylindrical shape, and a main cutting edge 3 of approximately 1/4 circular shape is formed by grinding on the hemispherical side of the tip. It is integrally formed. The main cutting edge 3 extends from the cutting edge starting point 5 located near the center of rotation toward the cutting edge ending point 6 in the diagonal direction when viewed in a straight line direction as seen in FIG. As seen in the drawings and FIG. 3, the conical curved rake face 8a forms a three-dimensional, substantially quarter-circular arcuate edge that cuts and generates a hemispherical surface. Therefore, based on Figure 1,
This main cutting edge 3 is relative to the axis center line 2 of the main body 1.
It is located in a linear inclined relationship from the cutting edge starting point 5 to the cutting edge ending point 6. The idea behind the configuration of this main cutting edge 3 is the 7th
As shown in Figures a and b, if the sphere 50 is cut along a certain plane 51, a circular cut surface 52 can be obtained, and the center point O between this circular cut surface 52 and the sphere 50.
This is based on the fact that if the circular ridge line 55 is connected, a cone 53 is formed, and if the obtained circular ridge line 55 is rotated about the center line 54, a hemispherical surface for the hatched portion is formed. That is, based on this virtual cone, the idea is to use the conical surface as the curved rake face, the circular ridgeline as the cutting edge, and the conical bottom side as the relief surface. In the case of Fig. 1, the main cutting edge 3 is set at a linear inclination angle (90°-α) with respect to the axis center line 2.
Assuming a virtual vertical reference line 4 at an angle of α, and considering a right circular cone with its apex at the intersection of this vertical reference line 4 and the shaft center line 2, the constant cutting edge radius R as described above can be obtained. A cutting edge configuration having the following is obtained.
Therefore, the center point _O1 of the radius R of the cutting edge becomes the above-mentioned intersection point. In this case, the angle α is set, for example, in the range of 45° to 75°, and the inclination angle (90°−α) of the main cutting edge 3 to this is 25° to 45°. In addition, the curved rake face 8 that constitutes this main cutting edge ridge 3
A concave chip pocket 7 is provided in series on the center point _O1 side of a. On the flank side, a belt-shaped primary flank 8b is formed. This is because if the conical bottom is used directly as the flank, the clearance angle will become too large and the strength of the cutting edge will be impaired.
As a result, the chip pocket 7 can be formed without sacrificing the strength of the main body 1 because the straight main cutting edge 3 is inclined with respect to the axial center line 2 of the main body 1, as shown in FIG. , can take up enough space. Furthermore, about half of the hemispherical side portion of the tip of the main body 1 is removed at a portion on the opposite side to the main cutting edge 3, which is shifted by about 180 degrees when viewed in the direction in which the main cutting edge 3 is a straight line. This removal was done in order to secure a space for chips at the cutting edge starting point 5 of the main cutting edge 3. From this removed end 11, the auxiliary cutting edge 10 for cutting the outer peripheral part is integrally formed with the main body 1. It is formed along the twisted groove 9. In this case, the twist angle θ of the twist groove 9 is set to be larger than that of conventional products, for example, θ=20° to 45°. While the main cutting edge 3 is involved in cutting a hemispherical surface, the auxiliary cutting edge 10 is involved in cutting the outer periphery and performs so-called right-angled shoulder cutting. Therefore, the minor cutting edge ridge 10 is the same as the main cutting edge 3.
It extends axially longer than the
Enables deep cutting and grooving. in this case,
The axial length of the auxiliary cutting edge 10 is about three times longer than the radius R of the cutting edge (edge diameter D=2R). The amount of removal of the end 11 is approximately 1/2R in the axial direction. As described above, what was removed was to secure a space for chips near the cutting edge starting point 5 of the main cutting edge 3. In this embodiment, the entire main body 1 is made of cemented carbide, but if economic efficiency is considered, the blade portion where the main cutting edge 3 and the minor cutting edge 10 are formed is made of cemented carbide. with a steel handle (not shown) at the rear end.
A so-called top solid type may also be used. The ball end mill of the present invention constructed in this way is generally applied to those having a cutting edge diameter of about 3 to 10 mmφ, and the recommended cutting conditions are as shown in the table below. In this case, D is the cutting edge diameter, H _S is Shore hardness, and H _S is Brinell hardness.

[Table] (Cutting example) The nominal diameter of the ball end mill was 10 mmφ, and the work material was S55C (Shoer hardness 35 to 38). The cutting conditions are: rotation speed N = 1800r.pm, cutting speed V = 56m/min, table feed F = 126mm/
min, feed per tooth f = 0.04 mm/tooth. As a result, the product of the present invention has two passes (one pass = 200 mm)
The flank wear showed normal wear when V _B =0.07 to 0.1 mm, and cutting was still possible. On the other hand, with conventional two-flute (symmetrical blade shape) ball end mills that have an arc-shaped cutting edge formed by the intersection of a flat rake face and a curved flank face, during two-pass cutting,
Boundary burrs have occurred. Burnt chips were also observed,
The vibration also increased, so cutting was stopped. The flank wear at this time was V _Bnax = 0.35, with significant chipping. This difference is due to the cutting edge configuration, chip evacuation performance, and tool rigidity. As explained above, the present invention constitutes a two-flute structure with a three-dimensional arcuate main cutting edge 3 and a twisted secondary cutting edge 10 suitable for a solid-type small-diameter end mill. Furthermore, since the space for discharging chips is taken into consideration, it is expected that cutting performance will be improved.

[Brief explanation of the drawing]

Fig. 1 is a front view showing one embodiment of the ball end mill of the present invention, Fig. 2 is a bottom view thereof, Fig. 3 is a partial side view as seen diagonally from below in Fig. 1, and Fig. 4 is: Similarly, a partial side view seen from diagonally above Figure 1.
5 is a partial side view of FIG. 2 taken from diagonally below to the left, FIG. 6 is a partial side view of FIG. 2 taken from diagonally above to the right, and FIGS. FIG. 2 is a diagram illustrating the configuration of a cutting edge, in which a is a front view and b is a side view from diagonally below to the right. 1...Main body, 2...Shaft center line, 3...Main cutting edge ridge, 4...
Vertical reference line, 7...Chip pocket, 8...Primary flank surface, 9...Twisted groove, 10...Sub-cutting edge ridge, 11...Removal end.

Claims (1)

[Claims] 1. On the hemispherical side of the tip of the cylindrical main body 1, an arcuate main cutting edge ridge 3 is formed by the intersection of the curved rake face 8a and the flank surface, and this main cutting edge ridge 3 is configured for cutting a hemispherical part by locating the cutting edge starting point 5 near the center of rotation, and the main cutting edge 3 is offset by about 180 degrees in the circumferential direction from the cutting edge starting point 5 of the main cutting edge 3. In a solid type ball end mill in which a secondary cutting edge ridge 10 is formed at a position for cutting the outer peripheral part following cutting of the hemispherical part, the curved rake face 8a is formed so that the main cutting edge ridge 3 forms a straight line. The center point O ₁ constituting the cutting edge radius R on the shaft center line 2, passing through this center point O ₁ ,
In addition, a portion of the conical surface in the virtual cone determined by the perpendicular reference line 4 with respect to the straight line forming an inclination angle α with the shaft center line 2 and the cutting edge starting point 5 of the main cutting edge 3 exhibiting a straight line. In addition, a concave chip pocket 7 is continuously provided on the center point _O1 side, and the main cutting edge 3 is formed at the intersection of the curved rake face 8a and the flank face. When viewed in the direction of an arcuate shape, the cutting edge has an approximately 1/4 circular shape from the starting point 5 to the ending point 6, and the hemispherical side of the tip of the main body 1 is connected to the main cutting edge. Ridge 3
The removal end 11 is formed so that approximately half of the opposite side to the main cutting edge ridge 3 is cut out when viewed in a direction in which the main cutting edge ridge 3 is a straight line. With the formation of the axial chip space, the auxiliary cutting edge 10 starts axially rearward of the cutting edge starting point 5 of the main cutting edge 3, and its axial length increases. A solid-type ball end mill characterized in that the main cutting edge edge 3 is longer than the main cutting edge 3, and the helix angle θ is formed along the helix groove 9.