JPH11197932A - Throw-away tip and ball end mill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a good cutting quality of a tip and keep the tip from slipping off from a tool main body at the time of return cutting. SOLUTION: A tip 2 is so constructed that a first cutting edge 26 and a second cutting edge 33 which are substantially 1/4 circular arc on the outer peripheral surface are rotation symmetrical about the center line L. Both end parts of the first cutting edge 26 and the second cutting edge 33 are connected to end cutting edges 42, 43 reaching a chamfer face 24a or 24b of a cut-off surface 24. The end cutting edges 42, 43 are longer than the return cutting width, and a cut face 40 forming a flank has a positive clearance angle. This tip is inserted in a groove 5 of a tool main body 2 of a ball end mill 50 to be bolted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ball end mill used for machining a die and the like, and a throwaway tip suitable for use in the ball end mill.

[0002]

2. Description of the Related Art Conventionally, a throw-away type ball end mill disclosed in Japanese Patent Application Laid-Open No. Hei 8-25271 has been known. FIGS. 10 and 11 show an example of such a throw-away type ball end mill. That is, in the throw-away type ball end mill 1 shown in FIGS. 10 and 11, the tip 3 of the tool body 2 is formed in a substantially hemispherical shape.
The center portion including the rotation axis O of the tool main body 2 is removed in a substantially flat plate shape with a predetermined thickness in the diametric direction, and is opened at both outer peripheral surfaces of the tip end portion 3. It has been. The groove 5 is formed by cutting out a flat plate having a predetermined thickness and a substantially semicircular arc. For this reason, the distal end portion 3 is divided into two at the lower portion by the groove 5 to form the holding portions 6a and 6b.

In the groove 5, a plate-like throw-away chip 8 having an arc exceeding a substantially semicircle is mounted and screwed, and an arc-shaped outer peripheral surface of the chip 8 exceeding a substantially semicircle is provided. The first and second cutting blades 10 and 12 each having an arc shape of approximately 1/4 from both end portions are provided on the upper surface side and the lower surface side of the side surface of the chip 8, and are formed to be 180 ° rotationally symmetric. ing. Therefore, at the time of rotary cutting, the first cutting edge 10 and the second cutting edge 12 draw a rotation trajectory having a substantially hemispherical shape. In the indexable insert 8, corners are formed on the base end 10a of the first cutting edge 10 (and the second cutting edge 12) along the rake face of the first cutting edge 10 by the upper and lower surfaces 1.
The chamfered surface 14 is cut in the directions 1 and 13, and the intersection ridge line between the chamfered surface 14 and the rake face of the first blade 10 is a base end cutting edge 15. The chamfered surface 14 is the base cutting edge 1
The flank of No. 5 is set to negative.

[0004] By the way, such a ball end mill 1
When cutting a die or the like using a tool, in the case of return cutting in which the tool main body 2 is cut back while returning the tool body 2 in the base end direction (the direction of arrow A in FIG. 10), as shown in FIG. Cutting material 17
The draft of the shoulder portion 17a of the processed surface has an inclination angle of about 1.5 °, and the cutting width is c (for example, 1.
(About 5 mm) (see FIG. 12). for that reason,
While rotating the tool body 2 in the return direction, the first blade 1
The shoulder 17a of the processing surface is cut (shoulder cut) with the base cutting edge 15 from the base end 10a of the base cutting edge 0 (and the second cutting edge 12). Thus, the base cutting edge 15 cuts, for example, about the width c in a direction perpendicular to the rotation axis O.

[0005]

However, the base cutting edge 15 cannot be sufficiently cut over the cutting width c due to its short length, and the flank (chamfered surface 14) has a negative flank. Since the corners are set, the sharpness is poor and it is not useful as a cutting edge, and the return cutting cannot be performed sufficiently. for that reason,
At the time of return cutting, there is a disadvantage that the tip 8 comes off the tool main body 2 by abutting the shoulder portion 17a on the negative cut surface 14 of the tip 8. In view of such problems, an object of the present invention is to provide a throw-away insert capable of performing sufficient shoulder cutting without coming off from a tool main body at the time of return cutting. Another object of the present invention is to provide a sharp away indexable ball end mill which can perform sufficient shoulder cutting for return cutting and has good sharpness.

[0006]

The indexable insert according to the present invention has a notch formed by cutting a part of a disk,
A substantially plate-shaped throw-away in which a substantially arc-shaped cutting edge is formed along a substantially arc-shaped outer peripheral surface of the disk, and a flank is provided on a side surface in a thickness direction of the arc-shaped cutting blade. In the insert, an end cutting edge is formed between the end of the arcuate cutting edge and the notch, and the flank of the end cutting edge is formed in the thickness direction, and the positive clearance angle is set. It is characterized by being.
For this reason, the indexable insert is mounted on, for example, a ball end mill and cut, so that when the return cutting is performed, the end cutting edge of the tip can cut over the cutting width of the return cutting, and the escape of the end cutting edge can be performed. Since the surface has a positive clearance angle, the edge cutting edge is sharp and the insert does not come off the tool body. Note that the end cutting edge may be formed in a straight line or a convex curve.

Further, the ball end mill according to the present invention comprises:
An arc-shaped cutting blade protrudes and is formed at the tip of the tool body,
In a ball end mill in which the rotation trajectory of the arc-shaped cutting blade has a substantially hemispherical shape, an end cutting edge is further formed following the base end of the arc-shaped cutting blade, and The flank is characterized in that a positive clearance angle is set. Therefore, when the return cutting is performed, the end cutting edge can sufficiently cut over the cutting width of the return cutting, and the flank of the end cutting edge has a positive clearance angle. The sharpness is good without the cutting edge being lost. Note that the end cutting edge may be formed in a straight line or a convex curve. Alternatively, the ball end mill may be a throw-away type ball end mill, and the throw-away tip may be provided with an arc-shaped cutting edge and an end cutting edge.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a throw-away chip according to an embodiment of the present invention will be described with reference to FIGS.
1 to 5 show a throw away tip according to a first embodiment. FIG. 1 is a front view of the throw away tip, FIG. 2 is a right side view of the throw away tip shown in FIG. 1, and FIG. 1 is a left side view of the throw away tip, FIG. 4 is a bottom view of the throw away tip shown in FIG.
FIG. 5 is a plan view of the throw-away tip shown in FIG. The throw-away tip 20 according to the embodiment has a plate shape having a circular portion that is partially cut out and has an arc portion larger than a semicircle, and has an upper surface 21, a lower surface 22, and a substantially arc-shaped side surface 23 in a thickness direction. have. The cut-out side surface is a cut surface 24 that forms a convex curved surface having a larger diameter than the side surface 23,
Both sides are chamfered to form chamfered surfaces 24a and 24b. The upper and lower surfaces 21 and 22 are formed with through holes 25 for penetrating chips for penetrating through the centers thereof.
reference).

In FIG. 1, for example, the right half of the arc-shaped side surface 23 is substantially 1 /
A four-arc-shaped first all blade 26 is formed, is connected from the first all blade 26 toward the upper surface 21 through a rake surface 27 having a predetermined width to a vertical wall 29, and further has a stepped shape reaching the upper surface 21. Are formed. Moreover, on the arc-shaped side surface 23, the first blade 26 is located closer to the upper surface 21 than the lower surface 22, and the first flank 3 is located on the lower surface 22 side from the first blade 26.
0 and the second flank 31 are sequentially formed. Moreover, the first blade 26 extends parallel to the upper and lower surfaces 21 and 22 on the side of the end portion 26 a in the side view shown in FIG. 2 and then curves along the side surface 23 so as to gradually approach the lower surface 22. Have been.
The first flank 30 has a small width and is formed along the first blade 26.

A second cutting edge 33 is formed in the left half of the arc-shaped side surface 23 in FIG. 1 to form a substantially 1/4 arc starting from the end 33a on the cut surface 24 side. From the bottom surface 22 to the lower surface 22 through the vertical wall 35 via the rake face 34 having a predetermined width. Moreover, in the arc-shaped side surface 23, the second cutting edge 33 is located closer to the lower surface 22 than the upper surface 21, and the first flank 37 and the second flank 38 are sequentially formed from the second cutting edge 33 toward the upper surface 21. Is formed. The second cutting edge 33 extends parallel to the upper and lower surfaces 21 and 22 on the end 33a side in the side view shown in FIG. 3 and thereafter gradually approaches the upper surface 21 side.
It is formed to be curved along. The first flank 3
The clearance angles of 0 and 37 are, for example, 10 ° and the second clearance surfaces 31 and 3
The clearance angle of 8 is, for example, 15 °, and a positive clearance angle is set, respectively, and the rake faces 27, 34 have a positive rake angle of, for example, 8 ° (relative to the upper surface 21 or the lower surface 22). As shown in FIG. 4, the first blade 26 and the second cutting edge 33 extend from the ends 26a and 33a and extend in the thickness direction of the side surface 23 at the center of the arc-shaped side surface 23 of the chip 20. Deviated from each other and ended at an oblique intersection line 36.

The first blade 26 and the second cutting blade 33 are
The rake faces 27, 34, the first flank faces 30, 37, and the second flank faces 31, 38 are formed to be rotationally symmetric with respect to the center line L of the chip 20 shown in FIG. Also, both corners of the side surface where the side surface 23 and the cut surface 24 intersect are cut into cut surfaces 39 and 40, respectively, and the cut surfaces 39 and 40 are rake surfaces 27 and 3 in plan view shown in FIG.
4. Standing walls 29, 35 and chamfer 24 of cut surface 24
a and 24b are formed to extend by cutting out a part thereof. Then, the cut surfaces 39 and 40 and the rake surfaces 27 and 3
4. The ridges formed by the upright walls 29, 35 and the chamfered surfaces 24a, 24b are end cutting edges 42, 43 for return cutting, and the cut surfaces 3 forming flank surfaces of the end cutting edges 42, 43.
The relief angles 9 and 40 are set to a positive angle of 8 °, for example.

The indexable tip 20 according to the present embodiment has the above-described configuration.
Are mounted on the tool body of the ball end mill 50 shown in FIGS. 6 and 7. The tool body of the ball end mill 50 according to the present embodiment has substantially the same configuration as the tool body 2 of the above-described conventional ball end mill 1, and the same or similar parts as those in the related art are denoted by the same reference numerals and description thereof is omitted. I do. FIG. 6 is a side view of the ball end mill according to the embodiment, and FIG. 7 is a side view of the ball end mill as viewed at an angle different from that of FIG. That is, in the throw-away type ball end mill 50 shown in FIGS. 6 and 7, the two holding portions 6 a, the lower portions of which are separated by the grooves 5 of the distal end portion 3 of the tool body 2,
6b, a bolt hole is drilled perpendicular to the groove 5, and a flat seating portion 52 in which the head 51a of the bolt 51 is located is formed on the top of the holding portion 6a, and the holding portion 6b of the bolt hole is formed. A female screw that is screwed with the bolt 51 is cut in the side part.

Then, the throw-away tip 2 is inserted into the groove 5.
0 is inserted into the bolt holes of the holding portions 6a and 6b through the insertion holes 25 of the throw-away tip 20.
The chip 50 is pressed and held by the holding portions 6a and 6b to be fixed by inserting and screwing the chip 1. In this state, the first circular blade 26 and the second cutting blade 37, which are substantially arc-shaped, project from the groove 5 to the outside of the distal end portion 3 by approximately 1/4 arc and are positioned 180 ° rotationally symmetric. And its rotation trajectory is formed in a substantially hemispherical shape. In addition, in the holding portion 6a of the distal end portion 3, a region sandwiched between the first blade 26 protruding from the groove 5 and the seating portion 52 is cut out substantially in an L-shape along these portions, and the first concave groove 54 is formed. Similarly, a second groove 55 is formed in the other holding portion 6b so as to be rotationally symmetric with the first groove 54. At the base ends of the first and second cutting edges 26 and 37, almost all of the end cutting edges 42 and 43 project outward from the outer peripheral portion of the groove 5.

Ball end mill 50 according to the present embodiment
Is configured as described above, and when cutting a work material, the tool body 2 is rotary-cut while being fed to the tip end side of the rotation axis O. As a result, the rotation trajectory of the first all blade 26 and the second cutting blade 37 becomes substantially hemispherical, and the chips cut by the first all blade 26 travel on the rake face 27 of the chip 20 to form the vertical wall 29. Is guided into the first groove 54 of the holding portion 6a to be curled, divided, and discharged. Chips cut by the second cutting blade 33 are similarly guided from the rake face 34 and the standing wall 35 to the second groove 55 of the holding portion 6b and are separated and discharged.

When the tool body 2 is returned to the base end side of the rotation axis O with respect to the processing surface, the tool body 2 is rotated and cut by the end cutting blades 42 and 43, and the end body is covered by the end cutting blades 42 and 43. The shoulder portion 15a of the work surface is cut by a width c, for example, 1.5 mm.
Although the cutting is performed over the width, the end cutting edge 4
2 and 43 have the lengths extending to the rake faces 27 and 34, the vertical walls 29 and 35, and the chamfered surfaces 24a and 24b of the cut surface 24.
The cutting edges 42 and 43 can be cut sufficiently over the cutting surface 39 and the clearance angle of the flank formed by the cut surfaces 39 and 40 is set to a positive value, so that the sharpness is good (FIG. 8).
reference).

As described above, according to the present embodiment, the substantially arc-shaped first and second cutting edges 2 of the indexable insert 20 are formed.
6, 33 end cutting edge 4 having a positive clearance angle
2 and 43, the shoulder portion 17a can be sufficiently cut when mounted on the ball end mill 50 and cut back.
Does not fall out of the tool body 2.

FIG. 9 shows a modification of the throw-away tip 20 according to the above-described embodiment. In FIG. 9, the cut surfaces 61 and 62 at both ends of the cutout surface 24 of the throw-away tip 60 are respectively convex curved surfaces. And the end cutting blade 63 formed by the intersection ridgeline of the cutting surface 61 and the rake face 27 of the first blade 26, the standing wall 29, and the chamfered surface 24a is formed in a convex curve shape. Similarly, the cutting surface 62, the rake face 34 of the second cutting edge 33, the standing wall 35, and the chamfered face 2
The end cutting edge 64 formed by the intersection ridge line with 4b is also formed in a convex curve shape. According to this modification, the end cutting blades 63, 64
Is formed in a convex curve shape, so that the cutting edge strength is further increased.

The end cutting edges 42, 43, 63, 64 need not necessarily be provided to extend from the intersection with the first cutting edge 26 or the second cutting edge 33 to the chamfered surfaces 24a, 24b. Instead, it may be extended over a length exceeding a required cutting width c at the time of return cutting. If such a length can be secured, the rake faces 27 of the first and second cutting blades 26, 33,
There may be up to 34. Further, the present invention may be applied to a ball end mill which is not a throw-away type.

[0019]

As described above, in the indexable insert according to the present invention, the flank of the end cutting edge is formed in the thickness direction and the positive clearance angle is set. The sharpness is improved and the shoulder portion can be cut well during cutting, and the indexable insert does not come off from the tool body. Further, in the ball end mill according to the present invention, an end cutting edge is further formed following the base end of the arcuate cutting edge, and the flank of the end cutting edge is set to a positive clearance angle. From, when performing the return cutting, in addition to being able to cut sufficiently over the cutting width of the return cutting by the end cutting edge,
Since the flank of the edge cutting edge has a positive clearance angle, the edge cutting edge has good sharpness without breakage.

[Brief description of the drawings]

FIG. 1 is a front view of a throw-away tip according to an embodiment of the present invention.

FIG. 2 is a right side view of the throw-away tip shown in FIG.

FIG. 3 is a left side view of the throw away tip shown in FIG. 1;

FIG. 4 is a bottom view of the throw-away tip shown in FIG.

FIG. 5 is a plan view of the throw-away tip shown in FIG.

FIG. 6 is a side view of a ball end mill equipped with the throw-away tip shown in FIG.

FIG. 7 is a side view of the ball end mill shown in FIG. 6 when viewed from directions different from each other by 90 °.

FIG. 8 is a partially enlarged view showing a processing state of a shoulder portion when the indexable insert according to the embodiment is mounted on the tool body and cut back.

FIG. 9 is a front view similar to FIG. 1, showing a modification of the throw-away tip according to the embodiment.

FIG. 10 is a side view of a conventional throw-away type ball end mill.

11 is a side view of the ball end mill shown in FIG. 10 when viewed from directions different from each other by 90 °.

FIG. 12 is a partially enlarged view showing a processing state of a shoulder portion when the conventional ball end mill performs return cutting.

[Description of Signs] 2 Tool body 3 Tip portion 20, 60 Throwaway tip 26 First blade 30, 37 First flank 31, 38 Second flank 33 Second cutting blade 39, 40, 61, 62 Cutting surface (Relief surface) 42, 43, 63, 64 End cutting edge 50 Ball end mill

Claims (2)

[Claims] 1. A notch in which a part of a disk is cut out,
A substantially plate-shaped throw-away in which a substantially arc-shaped cutting edge is formed along a substantially arc-shaped outer peripheral surface of the disk, and a flank is provided on a side surface in a thickness direction of the arc-shaped cutting blade. In the chip, an end cutting edge is formed between an end of the arc-shaped cutting edge and the notch, and a flank of the end cutting edge is formed in a thickness direction to set a positive clearance angle. A throwaway tip characterized by being made. 2. A ball end mill in which an arc-shaped cutting edge is formed to project from a tip end portion of a tool main body, and a rotation trajectory of the arc-shaped cutting edge has a substantially hemispherical shape. A ball end mill, further comprising an end cutting edge following the base end, wherein a flank of the end cutting edge is set to a positive clearance angle.