JPH045207Y2 - - Google Patents

Description

[Detailed explanation of the idea]

(Industrial Application Field) The present invention relates to a two-flute end mill, and is particularly suitable for counterboring and boring with a pilot hole, as well as for axially extending machining. be. (Prior Art) Conventionally, this type of end mill has been disclosed, for example, in Japanese Patent Publication No. 51-23748, Japanese Patent Publication No. 53-44270, and the like. The former has triangular plate-shaped throw-away tips arranged on the outer periphery and axial end of the tool body, while the latter has square plate-shaped throw-away tips arranged on the outer periphery and axial end of the tool body. This is what was placed. In addition, recently, a tool to which a diamond-shaped throw-away tip is applied has been put into practical use, but the diamond-shaped plate shape allows only two corners to be used, which is disadvantageous from the economical point of view of the tool. (Problem to be solved by the invention) However, the above-mentioned end mill does not necessarily have good cutting performance because the axial rake angle and radial rake angle of the throw-away tip are both negative angles or 0°. It wasn't. In addition, when the cutting feed rate was increased, chatter occurred and large burrs were observed in terms of sharpness. This invention uses a square plate-shaped throw-away tip to secure four corners when machining counterbore holes with prepared holes, and also improves cutting performance through the rake angle configuration and cutting edge configuration. The present invention aims to solve the above problems by providing a new end mill. (Means for Solving the Problems) The present invention was devised in view of the above-mentioned points, and two flute grooves are formed in the axial direction in the cylindrical tool body. To provide a two-blade end mill in which throwaway tips are respectively installed in tip seats provided at the tip. That is, the throwaway tip has a square plate shape with an inclined side surface, and on the upper surface side constituting the rake surface, a circumferential breaker groove with a central land portion protruding is formed, and
The cutting edge is provided with a concave and convex ridge with a linear step. In this case, since the cut has a substantially rectangular shape, the maximum length on the cutting edge side is larger than the length of the remaining convex cutting edge. Furthermore, when the throw-away tip is placed in the tip seat, the cutting edge located on the axial end side of the tool body is perpendicular to the axial direction of the tool body when viewed from the tip, and its axis The rake angle α in the direction is a regular angle of up to 10°, and the rake angle β in the radial direction is set within the range of −10° to −15°. (Function) The present invention uses a throwaway tip consisting of a positive square plate shape, and sets the rake angle α in the axial direction to a positive angle and the rake angle β in the radial direction to a negative angle. This not only improves cutting performance, but also makes it possible to use four corners when machining counterbore holes with pilot holes. Furthermore, the present invention reduces the burden of cutting force applied to the cutting edge by making the cutting edge ridge uneven and allowing the cutting to be performed separately. Furthermore, the present invention improves the disposal of chips by discharging chips having an uneven cross section. (Example) Hereinafter, an example of the end mill of the present invention will be described with reference to the drawings. In FIGS. 1 to 3, 1 is a two-blade end mill consisting of a cylindrical tool body 2 and a shank portion 3.
has two flute grooves 4 formed at its axial tip, and a throw-away tip 6 is mounted in a tip seat 5 of the flute groove 4. The throwaway tip 6 is shown in FIGS. 4a to 4d.
As clearly shown in the square plate shape with the inclined side surface 7, the so-called clearance angle θ
It constitutes a positive shape with . The throw-away tip 6 has a central mounting hole 8 and is mounted in the chip seat 5, for example by a tightening screw 9. Further, the throw-away tip 6 has a circumferential breaker groove 11 formed on the upper surface side constituting the rake surface so that the central land portion 10 remains and protrudes; Two or more approximately rectangular-shaped nicks 12 are formed (two in the illustrated case). Therefore, the cutting edge has an uneven shape with linear steps, but on the rotation locus with the axial depth of cut, the two throw-away tips 6 move the uneven cutting edge to each other. It is complementary. This mutual complementation can be achieved by forming the marks 12 in advance so as to shift the positions of the marks 12 on adjacent sides. The size of this cut 12 is such that the maximum length _L1 on the cutting edge side is larger than the length _L2 of the remaining convex cutting edge. Therefore, it is different from the V-shaped nick in which the land portion is cut out as seen in Japanese Utility Model Application Publication No. 50-11974. This is because the tool disclosed in the above-mentioned publication discharges divided so-called coil-shaped chips, so that the divided chips tend to become entangled with each other.
In contrast, in the end mill of the present invention, the cross section of the chips 13 exhibits a continuous uneven shape as shown in FIGS. 7a and 7b, and as shown in FIGS. 8a to 8c. In addition, tensile deformation due to the thickness of the chips makes them more likely to break in the width direction, making it difficult for the chips to get entangled with each other.
In this case, the center line in FIGS. 8a to 8c indicates the neutral plane of tensile deformation and compressive deformation of the chips, and ρ indicates the radius of curvature of the neutral plane. And, the effect of making Nik 12 exist is the first
This is also clarified from the chip test results shown in the table. In this case, the tool diameter applied to the test is
The machining depth is 20 mm with the prepared hole diameter of the work material (SUSS304H _B 160 to 180) being 14 mm. In addition, regarding the cutting conditions, the cutting speed V
The feed rate f was changed to 80 m/min.

[Table] In Table 1, the chips of the conventional product with only a parallel breaker have a so-called coil shape and are likely to become entangled. On the other hand,
In the present invention, the chip 12 is longer on the edge side of the cutting edge, so the cross section of the chip becomes uneven, and the width increases due to tensile deformation with respect to the thickness of the chip, as shown in Figures 7b and 8b. It was easy to break in the direction, and the chips did not get entangled with each other. Also, regarding the difference in power consumption and tearing,
This is due to the discharge status of chips and increases when galling occurs between chips and the inner wall of the hole. The end mill configured in this manner curls the chips upwardly by having the cutting edge located on the axial end side of the tool body 2 in a downwardly centered state with respect to the central land portion 10. Applicable to counterboring and boring with axial cutting, and rolling out with axial cutting. In this case, the above-mentioned nick 12 is adapted to be connected to the central land portion 10 in a direction transverse to the cutting edge, thereby facilitating upcurling of the chips. Also, Nik 1
Since the maximum length L ₁ on the cutting edge side of No. 2 is larger than the length L ₂ of the remaining convex cutting edge, the chips can be easily disposed of. Further, the rake angle formed in the throw-away tip 6 is such that the rake angle α in the axial direction is a positive angle and the rake angle β in the radial direction is a negative angle. And usually α is a conformal angle up to 10° and β is −10°
Set within the range of ~-25°. That is, the rake angle α in the axial direction is set based on the cutting resistance and the rigidity of the tool body 2. When the angle is negative, the cutting resistance increases, and when the angle exceeds +10°, the cutting resistance decreases, but on the other hand, the back support of the chip seat 5 becomes weak, which is disadvantageous in terms of tool rigidity. On the other hand, the rake angle β in the radial direction is -10° to
−15° was selected. In this case, the rake angle α in the axial direction is +5°, and the tool diameter is 20°.
The rake angle β in the radial direction is changed as mm. In addition, for the work material (S55C H _B 230), the prepared hole diameter is 13 mm and the machining depth is 20 mm.
Regarding the cutting conditions, the cutting speed V=
120 m/min, feed f = 0.16 m/min. Furthermore, in the present invention, only the cutting edge _L1 on the front side of the throw-away tip 6 is involved in cutting the workpiece 14, allowing the use of four corners. This is shown in Figures 9a-d.
The side ridge l ₂ located on the outer peripheral side is located inside the outermost cylindrical surface 15 on the rotation trajectory due to the provision of rake angles α and β in the axial and radial directions and the provision of clearance angle θ. It can be obtained by incorporating it as follows. Therefore, in counterbore machining and boring machining with prepared holes, it is possible to use four corners, as shown in the wear situation in FIG. 10. In this embodiment, the cut 12 formed in the circumferential breaker groove 11 is approximately rectangular in top view, but the cut 12 has a convex length in the ridge direction of the cutting edge. As long as the length of the blade is maintained longer than the edge of the blade, the shape can be changed, such as giving it a rounded edge. Next, an example of trial cutting of counterbore processing using the end mill of the present invention will be explained. The tool specifications are that the total length of the tool is 120 mm, the diameter of the shank part 3 is 25 mm, and the cutting edge diameter is 20 mm. applied something.
In this case, the circumferential breaker groove 11 forms two nicks 12 on each side as shown in the figure, and has an axial rake angle α of α=5° and a radial rake angle α when assembled into the tool body 2. β was set to β = −10°. In addition, a block material (250 mm in length x 180 mm in width x 37 mm in thickness) made of S55C (H _B 230) was used as the work material, and a 20 mm deep counterbore was used to dry-drill a prepared hole of 13 mm in diameter. I did it. The results of the counterbore processing were as shown in Table 2. In this case, the comparison product is a rhombic plate-shaped throw-away chip with an all-around breaker without a Nik 12, and has an axial rake angle α
= 0°, and the rake angle in the radial direction β = 0°.

[Table] As is clear from Table 2, the invented product:
Although chatter occurred at a cutting speed of 120 m/min,
There was no entanglement of chips and good chip evacuation was achieved. On the other hand, the comparative product has a speed of 70m/min.
Chattering occurred at both speeds of 120 m/min, elongated chips were ejected, and entanglement occurred at low feed speeds. FIG. 6 conceptually shows the shapes of chips in the product of the present invention and the comparative product. Furthermore, the occurrence of burrs, which affect cutting quality, was smaller at lower chip speeds and at higher feed rates. Note that this burr is generated on the inner diameter side of the prepared hole as shown in the figure, and the average value of three measurements is shown. Regarding the product of the present invention, various cutting tests revealed that recommended cutting conditions as shown in Table 3 were obtained when the cutting edge diameter was around 20 mm.

[Table] (Effects of the invention) As explained above, the present invention improves the cutting edge angle and the cutting edge configuration of the throw-away tip 6, and therefore has the following effects. First, there is no entanglement of chips, the finished surface is in good condition, and power consumption is reduced. This was also confirmed from Tables 1, 2, and Figure 6. Second, a positive square plate-shaped throw-away tip is adopted, and with the angle configuration mentioned above, the four corners can be used for counterboring and boring with pilot holes. This is now possible. This means that the tool is more economical than the conventional diamond-shaped indexable insert.

[Brief explanation of the drawing]

Fig. 1 is a front view showing one embodiment of the end mill of the present invention, Fig. 2 is a bottom view thereof, Fig. 3 is a partial side view, and Fig. 4 is a view showing the throw-away tip. Figure 4a is a front view thereof, Figure 4b is a cross-sectional view thereof, Figure 4c is a partially enlarged cross-sectional view taken along line CC in Figure a, and Figure 4d is a side view. figure,
Fig. 5 is an explanatory diagram showing the relationship between the rake angle in the radial direction and the height of the burr, Fig. 6 is an explanatory diagram showing the chip shape of the inventive product and the comparative product, and Fig. 7 is an explanatory diagram showing the relationship between the rake angle in the radial direction and the burr height. FIG. 7a is a perspective view of the fracture situation, and FIG. 7b is an explanatory diagram showing the generated chips.
is an enlarged perspective view of the fracture location, FIG. 8 is an explanatory diagram showing the deformation situation occurring in the chips, FIG. 8a is a perspective view, and FIG. 8b is a deformation stress in the convex portion A A conceptual diagram, FIG. 8c is a conceptual diagram showing the deformation stress in the concave portion B, FIG. 9 is a diagram explaining the use of four corners, FIG. 9a is a front view, and FIG. 9b is a side view. FIG. 9c is a bottom view showing the arrangement of the throw-away tip, FIG. 9d is a partial enlarged view of the main part, and FIG. 10 is a front view of the throw-away tip showing the worn state. 1... End mill, 2... Tool body, 4... Flute groove, 6... Throwaway tip, 7...
Sloped side surface, 10...Central land section, 11...Full circumference breaker groove, 12...Nick.

Claims (1)

[Claims for Utility Model Registration] Two flute grooves 4 are formed in the axial direction in the cylindrical tool body 2, and a throw-away groove is provided in each tip seat 5 provided at the tip of the flute groove 4. In a two-blade end mill to which a tip 6 is attached, the throwaway tip 6 has a positive square plate shape with an inclined side surface 7, and has a central land portion on the upper surface side constituting the rake surface. A circumferential breaker groove 11 is formed in which the groove 10 protrudes, and since the substantially rectangular nick 12 is present in the circumferential breaker groove 11, a cutting edge ridge obtained by intersecting with the inclined side surface 7 is formed. The groove is uneven with linear steps, and the maximum length L ₁ on the cutting edge side of the cut 12 is larger than the length L ₂ of the remaining convex cutting edge. Also, when placed in the chip seat 5, the cutting edge located on the tip side of the tool body 2 is aligned with the axial direction of the tool body 2 when viewed from the tip.
They are orthogonal to each other, and the rake angle α in the axial direction is a positive angle of up to 10°, and the rake angle β in the radial direction is set within the range of -10° to -15°. end mill.