JPH11156625A - Throw away tip, and throw away type ball end mill mounting it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent damage to a throw away tip due to a cutting load at the time of lifting work, and also ensure a proper cutting quality. SOLUTION: A pair of throw away tips mounted on the tip part of a tool main body are formed into nearly plate-shape having the same shape and size. A cutting blade 15 equipped with a circular arc cutting blade part 15a; having nearly a 1/4 circular arc state seeing from a direction opposite to an upper surface, and also having a protruded curved line state seeing from a direction opposite to a side surface 21c; is formed on the crossing ridge line part between an upper surface adopted as a rake face and a side surface 21c adopted as a flank. The tip thickness, between the cutting blade 15 and a lower surface 21b adopted as a seating surface, is set so that the maximum tip thickness EP can be obtained at a given position P on the circular arc cutting blade part, and also the tip thickness ER on the rear end position R of the cutting blade 15 can be thinner than the tip thickness EQ on the tip position Q of the cutting blade 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a throw-away tip (hereinafter referred to as a tip) having a cutting edge having a 1/4 arc-shaped cutting edge at the tip of a tool body, and the tip is mounted. The present invention relates to a throw-away type ball end mill (hereinafter, referred to as a ball end mill). In particular, the tool body is used for a so-called pulling process in which the tool body is rotated around its rotational axis while being lifted in a direction oblique to the axis to perform cutting. And a tip and ball end mill suitable for use.

[0002]

2. Description of the Related Art As this type of ball end mill, for example, the one shown in FIG. 15 has been proposed. The ball end mill shown in FIG.
And a pair of tip mounting seats 2 and 2 formed at the distal end of a tool body 1 that is rotated about an axis O, and a straight line with a substantially quarter-arc cutting blade 3a. Flat-shaped tips 4 and 4 having the same shape and the same size and having the cutting edge 3 provided with the cutting edge portion 3b position the arc-shaped cutting edge portion 3a from the rotation center side of the tool tip to the rear end outer peripheral side. At the same time, the linear cutting blade 3b is positioned so as to extend from the rear end of the arcuate cutting blade 3a to the tool rear end, and the axis O of each of the cutting blades 3, 3 is set.
It is configured to be removably mounted with the clamp screw 5 so that the rotation trajectories of the circumference coincide with each other.
Here, the tip of the cutting blades 3, 3 of the two tips 4, 4, that is, the inner peripheral end of the arc-shaped cutting blades 3a, 3a, is subjected to a cutting load as the cutting speed decreases near the rotation center of the tool tip. In order to prevent the chips 4 and 4 from being unevenly worn due to the increase in the diameter, the chips 4 and 4 are disposed at positions slightly away from the axis O.

[0003]

By the way, in such a ball end mill, the tool body 1 is sent out in a direction intersecting the axis O while rotating around the axis O, and the cutting edge 3 A groove having a bottom with a semicircular cross section is formed in the material. At this time, in addition to a general cutting process in which the tool body 1 is fed straight in a direction perpendicular to the axis O to perform cutting, for example, In the processing of a mold or the like, there is a case in which cutting is performed while raising the tool body 1 to the rear end side in a direction oblique to the axis O to form a groove or the like having a bottom portion inclined in a work material, that is, a so-called pulling process. is there. However, in the case of such a lifting process, a portion of the arc-shaped cutting edge portion 3a near the rotation center of the front end of the tool body 1 is not used for cutting, and a portion on the outer peripheral side and a rear end thereof are not provided. Cutting is performed exclusively by the side cutting edge portion 3b.

[0004] Therefore, when such a lifting process is performed, the largest cutting load among the cutting edges 3 of the tip 4 is not applied to the vicinity of the rotation center but to the cutting of the arc-shaped cutting edge portion 3a. It is a portion located on the inner peripheral side of the tool among the portions provided. For this reason, like the conventional chip 4 and the conventional ball end mill to which the chip 4 is mounted, the chip 4 is flat, that is, the chip thickness between the cutting edge 3 and the lower surface of the chip 4 is reduced. , Cutting blade 3
If the cutting edge 3 is made substantially uniform over the entire circumference, the strength of the tip 4 is insufficient at a portion where a large cutting load acts on the cutting edge 3 at the time of the above-mentioned pulling process, and the cutting edge 3 is damaged or the like. As a result, the chip 4 may be damaged.

[0005] Further, in the case of such a lifting process, the cutting is performed while the tool body 1 is raised toward the rear end side in a direction oblique to the axis O thereof.
The axial rake angle of the cutting edge 3 is substantially larger on the negative angle side than when the tool body 1 is sent out in a direction orthogonal to the general axis O. For this reason, in the above-mentioned ball end mill, the sharpness of the cutting edge 3 is impaired particularly at the outer peripheral side portion of the arc-shaped cutting edge portion 3a and the rear end side cutting edge portion 3b which are used for cutting during this lifting process. There is also a problem that the cutting resistance is increased and the chip dischargeability is impaired.

The present invention has been made under such a background, and in particular, it is possible to prevent the chip from being damaged by a cutting load even in the above-described pulling process, and to ensure a good sharpness. The aim is to provide a possible tip and ball end mill.

[0007]

SUMMARY OF THE INVENTION In order to solve the above problems and achieve such an object, a chip of the present invention has a substantially flat rake face and a rake face. A side surface and a lower surface serving as a seating surface;
A cutting edge having an arc-shaped cutting edge portion having a / 4 arc shape and a convex curve when viewed from a direction facing the side surface is formed, and a chip thickness between the cutting edge and the lower surface is determined by the above-described method. It is maximum at a predetermined position on the arcuate cutting edge,
The rear end position of the cutting blade is set smaller than the front end position of the cutting blade. Further, the ball end mill of the present invention is a ball end mill equipped with the chip configured as described above, wherein a tip mounting seat formed at a tip end portion of a tool body rotated about an axis has the same shape and size. A pair of the chips, the upper surface is oriented in the tool rotation direction, the lower surface is seated on the chip mounting seat, and the tip position of the cutting blade is located at the rotation center of the tool tip, and the arc-shaped cutting blade The part is positioned so as to extend from the center of rotation to the outer peripheral side of the tool rear end, the rotational trajectories of the cutting blades around the axis are matched with each other, and the parts are detachably mounted on opposite sides with respect to the axis. Features.

However, in the chip configured as described above, since the chip thickness between the cutting edge and the lower surface of the chip is set to be the maximum on the arcuate cutting portion, the chip is mounted. When pulling up is performed by a ball end mill, the chip strength at a portion where the largest cutting load acts on the cutting edge can be secured to prevent the cutting edge from being damaged or the like. Also, on the other hand,
In the tip having the above-described configuration, the tip thickness is set such that the rear end position of the cutting edge disposed on the outer peripheral side of the rear end of the tool is smaller than the distal end position of the cutting edge disposed at the rotation center of the tool tip. Since the setting is set, by mounting the chip, in the ball end mill, the axial rake angle of the cutting edge in a portion from the position where the chip thickness is maximum toward the rear end position of the cutting edge can be further reduced. Therefore, it is possible to prevent the sharpness of the cutting blade from being impaired during the lifting process.

Here, the position where the tip thickness between the cutting edge and the lower surface of the tip is maximum is an arc formed by this position and the arc-shaped cutting portion when viewed from the direction facing the upper surface of the tip. Is desirably set so that the included angle between a straight line connecting the center of the circular arc and a straight line connecting the center of the arc and the tip position of the cutting edge is in the range of 35 ° to 55 °. this is,
When the thickness of the chip is maximized at a position where the included angle is less than 35 ° or more than 55 °, when the chip is pulled up, the feed direction with respect to the axis of the tool body is increased. This is because, depending on the inclination angle, a position where the largest cutting load acts on the cutting edge and a position where the above-mentioned chip thickness is maximum are largely shifted, and there is a possibility that the chipping of the cutting edge cannot be prevented reliably. .

[0010] In the above-mentioned tip, the arc-shaped cutting edge portion is located rearward of the arc-shaped cutting edge portion of the cutting edge as viewed from a direction facing the upper surface, toward the rear end side. By forming the rear end side cutting edge portion extending so as to gradually recede with respect to the tangent line at the rear end, for example, compared to the case where this rear end side cutting edge portion is formed in parallel with the tangent line,
If the tangential cutting edge length is the same, the actual cutting edge length can be increased. Therefore, since the cutting load acting on the cutting edge per unit length is reduced, the chip is prevented from being damaged even when the rear end side cutting edge portion is used for cutting, especially at the time of the above-mentioned lifting processing. can do.

On the other hand, in the ball end mill equipped with such a tip, the auxiliary tip mounting seat is located at a position protruding one step further in the tool rotation direction than the tip mounting seat on at least one of the tip mounting seats. By forming an auxiliary tip having a cutting edge continuous to the rear end side of the cutting edge of the tip in the rotation locus around the axis on the auxiliary tip mounting seat, the auxiliary tip does not interfere with the tip. To extend the cutting edge length in the axial direction of the ball end mill in the rotation trajectory. Further, the chip is mounted on the chip mounting seat by screwing a clamp screw inserted into a mounting hole penetrating the upper and lower surfaces into the screw hole formed on the bottom surface of the chip mounting seat. in case of,
On the lower surface of the chip, one end communicates with the opening of the mounting hole and the other end forms a concave groove that opens on the side of the chip facing the tool inner peripheral side, while the bottom surface of the chip mounting seat is By forming a ridge that engages with the concave groove, the chip can be accurately positioned on the chip mounting seat by the engagement of the concave groove and the ridge, and the tool tip is particularly attached to the chip during lifting. The chip can be firmly held against the load acting toward the side, and the seating stability can be ensured.

[0012]

1 to 7 show an embodiment of a ball end mill of the present invention. FIGS. 8 and 9 show an embodiment of a chip of the present invention mounted on the ball end mill. It shows the form. In the ball end mill of the present embodiment, the tool body 11 has a substantially cylindrical shape, and the tip is formed in a substantially hemispherical shape, and a pair of the tips are provided on the opposite sides with respect to the rotation axis O of the tool body 11. Are formed on the wall surface of the tip pockets 12 and 12 facing the tool rotation direction T side, and a pair of tip mounting seats 13 and 13 are provided on the tool tip side, respectively. Auxiliary tip mounting seats 14A and 14B are formed on the rear end side of the tool.
Of these, the tip mounting seats 13, 13 on the tool tip side are provided with tips 16, 16 of substantially flat plate-shaped embodiments having the same shape and the same size and having a cutting edge 15 provided with an arc-shaped cutting edge portion 15a. The auxiliary tip mounting seats 14A, 14B on the end side have auxiliary tips 17, 17 of a substantially equilateral triangular plate shape, also of the same shape and size.
Are detachably mounted by means of clamp screws 18, respectively.

Here, the tip mounting seat 1 on the tool tip side.
3, 13 are formed symmetrically with respect to the axis O, and as shown in FIG.
2 is recessed rearward in the tool rotation direction T from the tool rotation direction T.
It comprises a bottom surface 13a facing the side, a wall surface 13b rising from the bottom surface 13a and facing the tool outer peripheral side, and a wall surface 13c facing the tool tip side. Further, the mounting screw hole 1 into which the clamp screw 18 is screwed is formed in the bottom surface 13a.
9 is formed, and a ridge 20 having a rectangular cross section is formed from around the opening of the mounting screw hole 19 to the wall surface 13b. In addition, this wall surface 13b is
The wall surface 13c is formed so as to be inclined toward the outer peripheral side of the tool as it goes toward the rear end of the tool.
The protrusion 20 and the wall surface 13c are formed in a direction perpendicular to the wall surface 13b when viewed from a direction facing the bottom surface 13a. . Further, in FIG.
Reference numeral d denotes an escape hole for avoiding interference of a tool when forming the wall surface 13b and the ridge portion 20.

On the other hand, the auxiliary chip mounting seats 14A, 14A
B is a substantially equilateral triangular bottom surface 14a that is recessed from the tip pocket 12 in the tool rotation direction T and faces the tool rotation direction T side, and the tool rises from two sides of the equilateral triangle formed by the bottom surface 14a. A wall surface 14b facing the rear end outer periphery and a wall surface 14c facing the tool tip outer periphery,
These wall surfaces 14b and 14c are formed so that the included angle is 60 ° when viewed from the direction facing the bottom surface 14a. Furthermore, these auxiliary tip mounting seats 14A, 14A
B, one auxiliary chip mounting seat 14A is formed immediately adjacent to the tip mounting seat 13 on the distal end side, and the wall surface 14b is shortened, while the other auxiliary chip mounting seat 14B is The wall surface 14b is formed at a distance from the tip mounting seat 13 on the tip side and intersects with the wall surface 14c of the one auxiliary tip mounting seat 14A in the rotation locus around the axis O as shown in FIG. It is arranged to be. As shown in FIG. 6, the bottom surface 14a of the auxiliary tip mounting seat 14A is formed at a position projecting one step further in the tool rotation direction T than the tip mounting seat 13 at the tip end thereof, and at the rear end of the tool. It is slightly inclined so as to approach the tool rotation direction T side.

The chip mounting seat 13 thus formed,
The tip 16 of the present embodiment, which is attached to the tip attachment seats 13 on the tool tip side, among the pieces 13, 14A and 14B.
As shown in FIGS. 8 and 9, the chip main body 21 is formed of a hard material such as a cemented carbide and has a substantially fan-shaped flat plate shape.
3 has a lower surface 21b serving as a seating surface on the bottom surface 13a, a substantially conical side surface 21c and flat side surfaces 21d to 21f arranged around the upper and lower surfaces 21a and 21b. 21c to 21f are formed so as to be inclined toward the inside of the chip body 21 toward the lower surface 21b. The cutting blade 15 is connected to the upper surface 21.
a and a substantially conical side surface 21c are formed at the intersection ridge, so that the side surface 21c is a flank of the cutting edge 15 and the tip 16 has a clearance angle at the flank. Is a positive tip.

Further, the cutting blade 15 is provided on the upper surface 21a.
When viewed from the direction opposite to the above, the above-mentioned arc-shaped cutting edge portion 15a on the tip side forming a substantially 1/4 arc shape, and this arc-shaped cutting edge portion 15a
The rear end of the cutting edge 15 extends in the form of an arc having the same radius of curvature as the arc-shaped cutting edge portion 15a, and then extends linearly in the tangential direction of the arc. And a cutting blade 15b. Accordingly, as shown in FIG. 9, as viewed from the direction facing the upper surface 21 a, the rear end side cutting edge portion 15 b has a shape of the circular arc at the rear end M of the arcuate cutting edge portion 15 a toward the rear end side. It is formed so as to gradually retreat with respect to the tangent line N. Strictly speaking, the side surface 21c is a surface in which a short plane is in contact with the rear end side of the conical surface connected to the arc-shaped cutting blade portion 15a. Further, in the present embodiment, the cutting blade 15 is
When viewed from the direction opposite to, as shown in FIG. 10, the arc-shaped cutting edge portion 15a is formed in a convex curve shape bulging to the upper surface 21a side, and the rear end side cutting edge portion 15b is
The convex-shaped curved cutting edge portion 15a extends in a tangential direction at the rear end of the arc-shaped cutting edge portion 15a, and is formed linearly toward the lower surface 21b as the distance from the rear end of the arc-shaped cutting edge portion 15a increases.

Further, in the tip 16 of the present embodiment, as shown in FIG. 9, when viewed from the direction facing the upper surface 21a, the tip 16 passes through the center C of the arc formed by the arc-shaped cutting edge portion 15a, and Assuming a straight line L having an included angle α of 45 ° with respect to a straight line S connecting the tip position Q of the cutting blade 15 with the tip C, when the side surface 21 a of the tip 16 is viewed from the straight line L direction, The blade portion 15a is formed such that the position of the intersection P of the arc-shaped cutting blade 15a and the straight line L when viewed from the direction facing the upper surface 21a forms a convex arc shape most protruding with respect to the lower surface 21b. Therefore, the cutting edge 1 in the direction perpendicular to the lower surface 21b of the tip 16
5 and the lower surface 21b, ie, the cutting edge 15 and the lower surface 2
Chip thickness between 1b is set to be the largest chip thickness E _P at the position of the intersection point P as shown in FIG. 10. Further, as described above, as the rear end side cutting edge portion 15b of the cutting edge 15 is formed toward the lower surface 21b side when viewed from the direction facing the side surface 21c, the tip thickness of the cutting edge 15 The tip thickness E _R at the rear end position R of the cutting edge 15 is set to be smaller than the tip thickness EQ at the front end position _Q , that is, the minimum tip thickness E _{R at} this rear end position _R. Becomes

In the chip body 21 of the chip 16 according to the present embodiment, the upper surface 21a which is a rake face is used.
In addition, a groove-shaped chip breaker portion 22 is formed along the cutting edge 15, so that the arc-shaped cutting edge portion 15a and the rear end side cutting edge portion 15b have a positive rake with respect to the cutting edge 15. Horns are given. In addition, a portion of the upper surface 21a inside the chip breaker portion 22 rises upward toward a radially inner circumferential side of an arc formed by the cutting blade 15 when viewed from a direction facing the upper surface 21a, and then rises to the lower surface 21b. It is formed so as to form a parallel flat surface.
As for b, the mounting hole 23 through which the clamp screw 18 is inserted is formed so as to penetrate the chip body 21. Further, as shown in FIGS. 13 and 14, on the lower surface 21b of the chip body 21, there is provided a groove 24 having a rectangular cross section having one end on the periphery of the opening of the mounting hole 23 and the other end opening on the side surface 21d. Are formed so as to be perpendicular to the side surface 21d when viewed from the direction facing the lower surface 21b.

On the tip position Q side of the cutting blade 15, a crossing ridge portion between the upper surface 21a and the side surface 21d of the tip body 21 is chamfered, and a crossing ridge line between the chamfer and the side surface 21c is formed. Part, the arc-shaped cutting blade 15
A small cutting edge 15c that intersects a at an obtuse angle is formed. Therefore, the tip position Q of the cutting edge 15 is determined by the small cutting edge 15c.
The position of the tip of. Further, the side surface 21d and the side surface 21f of the chip body 21 are formed in a direction orthogonal to each other when viewed from a direction facing the upper surface 21a, and the side surface 21e disposed between the side surfaces 21d and 21f is formed on both side surfaces. 21d and 21f are formed so as to intersect at an obtuse angle. Furthermore, the side surfaces 21d to 21f and the lower surface 2
1b is chamfered.

In the chip 16 thus configured, the lower surface 21b of the chip main body 21 is brought into close contact with the bottom surface 13a of the chip mounting seat 13, and the side surfaces 21d and 21f are brought into contact with the wall surfaces 13b and 13c. The formed groove 24 is engaged with the ridge 20 on the bottom surface 13a and is seated on the chip mounting seat 13.
Is screwed into the mounting screw hole 19 on the bottom surface 13a to be fixed to the tool body 11 by being screwed. Then, in this mounted state, the chips 16, 16 are attached to each other as shown in FIG.
The tip position Q of 5, 15 is on the axis O of the tool tip,
That is, the center C of the arcuate cutting edge 15a is located on the axis O when viewed from the direction corresponding to the rotation center of the tool tip and facing the upper surface 21a as shown in FIG. And the axis O are arranged so as to coincide with each other, and the rotational trajectories of the both cutting edges 15 around the axis O coincide with each other,
In addition, the circular trajectories of the circular cutting edges 15a, 15a around the axis O are arranged in a hemispherical shape.

On the other hand, the auxiliary chip mounting seats 14A, 14
Each of the auxiliary tips 17, 17 mounted on B is a positive tip formed from a hard material such as a cemented carbide in a substantially equilateral triangular plate shape as described above, and has a regular triangular shape as a rake face. Cutting edges 25 are formed on the three side edges of the upper surface, respectively. Then, these auxiliary chips 17, 17 are, as shown in FIG.
a each of the cutting blades 25 as viewed from the direction facing
Are parallel to the axis O, and protrude toward the tool outer peripheral side at an equal distance from the axis O, the lower surface of the equilateral triangular shape is brought into close contact with the bottom surface 14a, and two other than the side surface connected to the one cutting edge 25 are provided. The side surfaces are the wall surfaces 14b and 14c
, And is attached and fixed to the tool body 11 by the clamp screw 18. In addition,
The distance from the axis O of the cutting edges 25, 25 of these auxiliary tips 17, 17 protruding to the outer peripheral side of the tool is determined by the outermost diameter of the cutting edge 15 of the tip 16 mounted on the tool tip side from the axis O. They are set approximately equal.

Further, among the auxiliary chips 17, 17, the auxiliary chip 17 mounted on the one auxiliary chip mounting seat 14A has the one auxiliary chip mounting seat 14A immediately adjacent to the tip mounting seat 13 on the distal end side. Adjacent to the rear, it is formed so as to protrude one step in the tool rotation direction T, and its bottom surface 14a is inclined in the tool rotation direction T toward the rear end of the tool, and the auxiliary tip 17 is a positive tip. Therefore, as shown in FIGS. 5 and 6, the tip 25 a of the cutting blade 25 is located at a position closer to the tip of the tool than the rear end position R of the cutting blade 15 of the tip 16 mounted on the tip mounting seat 13 on the tip side. Located on the side. The auxiliary chip 1 mounted on the other auxiliary chip mounting seat 14B is also provided.
7, the tip 25a of the cutting blade 25 as shown in FIG.
The rear end 25b of the cutting edge 25 of the auxiliary tip 17 mounted on the one auxiliary tip mounting seat 14A is located closer to the tool tip than the cutting edge 2 of these auxiliary tips 17,17.
5 and 25 are continuous from the cutting edge 15 of the chips 16 and 16 on the tool tip side toward the tool rear end side in the rotation locus around the axis O.

However, such a ball end mill provided with the tip 16 having the above-described structure allows the tool body 11 to be used.
When cutting is performed while pulling up to the rear end side of the tool in a direction oblique to the axis O, that is, when pulling-up processing is performed, the largest cutting load acts on the cutting edge 15 of the tip 16 as described above. It is not the tip position Q located at the center of rotation of the tool tip as shown in FIG. According to the tip 16 and the ball end mill, the cutting edges 15 of the tips 16
And the chip thickness between the lower surface 21b is, because it is set to be the largest chip thickness E _P at the position of the intersection point P on the arc-shaped cutting edges 15a of the cutting edge 15, as described above Sufficient chip strength can be ensured even for a large cutting load, so that it is possible to prevent a situation in which the cutting edge 15 is damaged or the chip 16 is damaged during the lifting process.

In the chip 16 having the above-described structure, the cutting edge 1
5, the tip thickness E _{R at} the rear end position R is set smaller than the tip thickness E _{Q at the} front end position _Q. Therefore, according to the ball end mill provided with the tip 16, the maximum tip thickness E portion from a position of an intersection P to be _P to the rear end position R of the cutting edge 15, i.e. the axial rake angle of the cutting edge 15 of the portion to be subjected to cutting in the pulling process, is set to be larger and more conformal side It becomes possible. For this reason, even if the substantial axial rake angle increases toward the negative angle side as described above in such pulling-up processing, it is possible to prevent the sharpness of the cutting edge 15 from being impaired and increase the cutting resistance. And the chips generated by the cutting edge 15 can be quickly removed from the tip pocket 12.
It can be pushed out to the rear end side of the tool to reliably discharge chips.

On the other hand, in the above-mentioned ball end mill, the pair of tips 16, 16 makes the tip positions Q of the cutting edges 15, 15 coincide with the center of rotation of the tool tip, and the arc-shaped cutting portions 15a, 15a. The rotation trajectories around the axis O of the pair 15a are also attached to each other, and the tip thickness EQ at the leading end position _Q is larger than the tip thickness E _{R at the} trailing end position R, and a certain amount of tip thickness is secured. Therefore, even when a normal tool body 11 is fed in a direction orthogonal to the axis O to perform cutting, a large cutting load acting near the rotation center is applied to the pair of tips 16, 16. While dispersing to the cutting blades 15, 15 and maintaining the tip strength at the tip position Q,
It is possible to prevent a situation in which the chips 16 are damaged. Further, in particular, the chip 16 of the present embodiment
Since the small cutting edge 15c intersecting the arc-shaped cutting edge 15a at an obtuse angle is formed at the tip of the cutting edge 15, the strength at the tip of the cutting edge 15 can be further improved, 16, 16 can be more reliably prevented from being damaged.

By the way, in the chip 16 of the present embodiment,
The chip thickness is maximum chip thickness E _P position, as viewed from a direction facing the upper surface 21a of the chip 16, the cutting edge 15
Through the center C of the arc formed by the arc-shaped cutting edge portion 15a,
The position of the intersection P between the straight line L where the included angle α with respect to the straight line S connecting the center C and the tip position Q of the cutting edge 15 becomes 45 ° and the cutting edge 15 is defined as the position of the intersection P. If the included angle α of the determined straight line L with respect to the straight line S is too small, the position of the intersection point P is excessively biased toward the tip position Q of the cutting edge 15. However, the position of the intersection point P in this way the maximum chip thickness E _P is biased to the tip position Q side of the cutting edge 15, when performing the pulling process by a ball end mill fitted with the chip 16, particularly the pulling When the inclination angle of the processing is set to be larger, the greatest cutting load to the cutting edge 15 of the partial chip thickness than the chip thickness E _P is small becomes to act, defects or the like of the cutting edge 15 can not be sufficiently prevented There is a risk. On the other hand, when the included angle α is too large, the position of the intersection point P of maximum chip thickness E _P reversed cutting edge 1
5, when the inclination angle of the lifting process is small, it may be impossible to prevent the cutting edge 15 from being damaged. For this reason, it is desirable that the included angle α is set to about 45 ° ± 10 °, that is, 35 ° to 55 °.

In the tip 16 of the present embodiment, when viewed from the direction facing the upper surface 21a of the chip body 21, which is a rake face, the rear end side cutting edge portion 15b of the cutting edge 15 is
Rear end M of the above-mentioned arcuate cutting edge portion 15a which forms a substantially 1/4 arc shape
After drawing an arc connected to the arc-shaped cutting edge portion 15a,
It is formed so as to extend in a tangential direction tangent to the arc, that is, it is formed so as to gradually retreat toward the rear end with respect to the tangent N at the rear end M as described above. Therefore, such chips 16, 16
Is attached to the tool body 11 such that the straight line S coincides with the axis O as described above, the tangent N
2 is parallel to the axis O as shown in FIG. 2 when viewed from the direction opposite to the direction a. Thus, the rear end side cutting edge portion 15b is disposed so as to be closer to the inner peripheral side of the tool toward the rear end side of the tool. Becomes For this reason, according to the present embodiment, for example, when the rear end side cutting edge portion 15b is formed along the tangent line N, that is, when the auxiliary tip 1 is attached to the tool body 11,
In this embodiment, if the lengths in the direction of the axis O are the same, the actual length of the rear-end side cutting edge portion 15b is different from the case where the cutting edge 25 is formed so as to extend parallel to the axis O in the same manner as the cutting edge 25 of FIG. Can be made longer, and conversely, the cutting load acting on the rear end side cutting edge portion 15b per unit length is reduced, so that damage to the tips 16A, 16B can be more reliably prevented. .

With the rear end side cutting edge portion 15b formed in this manner, the wall surface such as the groove of the work material formed by the rear end side cutting edge portion 15b is separated from the groove bottom portion. In particular, in the case of the above-mentioned pulling process, the remaining portion is cut into an arcuate cutting edge 15a in accordance with the inclination angle of the pulling. Since it can be cut off by the outermost diameter portion on the rear end side, it is possible to prevent the machining surface accuracy from being impaired. In the present embodiment, when viewed from the direction facing the side surface 21c of the tip main body 21, the rear end side cutting edge portion 15b has a lower surface 2 toward the rear end position R.
1b, the actual shape of the arc-shaped portion of the rear end side cutting edge portion 15b is an arc portion extending in the major axis direction of the ellipse rather than a strict arc. , Which also makes it possible to prevent the overhang-shaped uncut portion from becoming large.

On the other hand, in the ball end mill of the present embodiment, auxiliary tip mounting seats 14A and 14B are formed on the tool rear end side of the tip mounting seats 13 and 13, respectively.
One of the auxiliary tip mounting seats 14A is formed at a position projecting one step further in the tool rotation direction T side than the tip mounting seat 13 on the tip side. The cutting edge 2 that is continuous with the rear end of the cutting edge 15 of the tip 13 in the rotation locus around the axis O is provided on the one auxiliary tip mounting seat 14A.
The auxiliary tip 17 having the cutting edge 25 is attached to the auxiliary tip mounting seat 14B. The auxiliary tip 17 has a cutting edge 25 continuous to the rear end 25b of the cutting edge 25 of the auxiliary tip 17 of the one auxiliary tip mounting seat 14A. Since the tip 17 is attached, the length of the cutting edge in the direction of the axis O of the ball end mill on the rotation locus can be extended without causing the auxiliary tips 17 and 17 to interfere with the tip 16 on the distal end side.

However, in the above-described pulling process, the cutting depth changes as the tool body 11 is pulled up to the rear end side of the tool. Although the cutting must be performed a plurality of times at the cut depth, according to the present embodiment, as described above, the auxiliary tips 17, 17 are used.
Since the length of the cutting edge can be extended by providing the groove, it is possible to form an inclined groove in the work material by a single processing, and it is possible to improve the processing efficiency. Moreover, in the present embodiment, the one auxiliary tip mounting seat 14
Since the bottom surface 14a of A is inclined toward the tool rotation direction T as it goes toward the rear end of the tool, and the auxiliary tip 17 is a positive tip, the tool of this auxiliary tip mounting seat 14A with respect to the tip mounting seat 13 on the front end side Even if the amount of protrusion in the rotation direction T side is not so large, both the tips 16 and 17 can be surely brought close to each other so that the cutting blades 15 and 25 can be continued in the direction of the axis O. Blade 15
It is also possible to prevent a situation in which the discharge of the chips generated by the auxiliary tip mounting seat 14A and the auxiliary tip 17 is significantly impeded.

In this embodiment, as described above, the auxiliary tip 17 is formed in a substantially equilateral triangular plate shape, and the cutting edge 2 is formed.
5 is arranged so as to be parallel to the axis O of the tool body 11 when viewed from the direction facing the upper surface 21a of the chip 16, but a chip having another shape such as a square plate is used as an auxiliary chip. It is also possible. However, as in the present embodiment, the tip 16 attached to the tool tip side has a substantially fan-shaped flat plate shape and the tip mounting seat 13
If the wall surface 13c facing the tool tip side is inclined so as to approach the tool inner peripheral side toward the rear end side in the direction of the axis O, it is attempted to attach such a square plate-shaped chip as an auxiliary chip. If the one auxiliary tip mounting seat does not protrude largely in the tool rotation direction T with respect to the tip mounting seat 13 on the tip side, the tip 16 mounted on these tip mounting seats and the auxiliary tip interfere with each other. May occur. Therefore, in such a case, when the cutting edge protruding toward the outer peripheral side of the tool is made parallel to the axis O, such as an equilateral triangular flat plate-shaped chip as in the present embodiment or a rhombic flat plate-shaped chip, It is preferable to use a tip having a shape arranged so that the side surface facing the tool tip side is inclined inward toward the rear end side as the auxiliary tip.

Further, in the ball end mill of the present embodiment, the lower surface 21b of the chip body 21 of the chip 16 is provided.
On the other hand, a concave groove 24 extending from the mounting hole 23 of the clamp screw 18 to the side surface 21 d is formed, while a projecting ridge 20 extending from the mounting screw hole 19 to the wall surface 13 b is formed on the bottom surface 13 a of the chip mounting seat 13. The chip 16 is mounted on the chip mounting seat 13 with the concave groove 24 engaged with the ridge 20. Therefore, these ridges 20 and concave grooves 2
In this embodiment, the tip 16 can be accurately positioned and attached to the tool main body 11 by the engagement with the tool body 4. In particular, at the time of the above-mentioned pulling-up process, the tip 16 can be positioned on the tool tip side. Therefore, the chip 16 does not rattle even in the pulling-up process, and it is possible to promote the processing with higher precision. This is because, as in the present embodiment, the rear end side cutting edge portion 15b of the tip 16 is disposed so as to be directed toward the inner peripheral side of the tool as it is directed toward the rear end side. This is particularly effective when a load on the distal end side is likely to occur.

In addition, the concave groove 24 of the chip 16
It is formed between the opening of the mounting hole 23 on the lower surface 21b of the chip body 21 and the side surface 21d, and does not reach the opposite side surface 21c.
between the lower surface 21b and the cutting edge 15 of the c side, it is possible to reliably ensure a sufficient maximum chip thickness E _P as described above, such a situation that the chip body 21 may be damaged from the groove portion 24 By preventing the damage beforehand, damage to the chip 16 can be more reliably prevented. Also, in the present embodiment, the wall surface 13b of the tip mounting seat 13 formed on the tool tip side facing the tool outer peripheral side is formed so as to face the tool outer peripheral side toward the rear end side in the axis O direction. As described above, even when the tip position Q of the cutting edge 15 of the tip 16 is arranged so as to coincide with the rotation center of the tool tip, the wall 13b and the tool rotation direction T rearward on the tool rear end side. Since the thickness of the tool body 11 can be ensured between the tip pocket 12 and the tip pocket 12,
There is also obtained an advantage that the rigidity at the distal end portion of the tool body 11 and the rigidity for mounting the chip 16 are sufficiently ensured so that more stable cutting can be performed.

[0034]

As described above, according to the insert of the present invention and the ball end mill to which the insert is mounted, a sufficient chip thickness is ensured particularly at a portion where a large cutting load acts on the cutting edge during the lifting process. Accordingly, it is possible to prevent chip damage such as chipping of the cutting edge and perform stable processing. In addition, since the tip thickness at the rear end position is set smaller than the tip thickness at the front end position of the cutting edge, the axial rake angle of the cutting edge of the portion to be cut during the lifting process is set to be positive. It can be increased to the corner side, and the sharpness of the cutting edge can be ensured to suppress an increase in cutting resistance.

[Brief description of the drawings]

FIG. 1 is a plan view showing one embodiment of a throw-away type ball end mill of the present invention.

FIG. 2 is an enlarged plan view of a distal end portion of the embodiment shown in FIG.

3 is an enlarged front view of the distal end portion of the embodiment shown in FIG. 1 from the distal end side in the direction of the axis O. FIG.

FIG. 4 is a view of a side surface 21c of the throw-away tip 16 in FIG.

FIG. 5 is a plan view of the distal end portion of the embodiment shown in FIG. 1 as viewed from a direction perpendicular to the axis O and facing one auxiliary tip 17;

FIG. 6 shows a tip 25 of the cutting edge 25 of one of the auxiliary tips 17, which is perpendicular to the axis O, of the embodiment shown in FIG.
It is the side view seen from the linear direction which passes through a.

7 is a plan view of the tip mounting seat 13 of the embodiment shown in FIG.

FIG. 8 is a perspective view of a throw away tip 16 according to an embodiment of the present invention, which is mounted on the throw away type ball end mill of the embodiment shown in FIG.

FIG. 9 is a plan view of the throw-away tip 16 shown in FIG.

FIG. 10 is a side view of the throw away tip 16 shown in FIG. 8 as viewed from a direction parallel to a side surface 21f.

11 is a side view of the throw away tip 16 shown in FIG. 8 as viewed from a direction parallel to a side surface 21d.

FIG. 12 is a side view of the side surface 21c of the throw-away tip 16 shown in FIG. 8 viewed from the straight line L direction in FIG.

FIG. 13 is a bottom view of the throw-away tip 16 shown in FIG.

FIG. 14 is a sectional view taken along the line ZZ in FIG. 9;

FIG. 15 is a plan view showing a conventional ball end mill.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11 Tool main body 13 Tip mounting seat 14A, 14B Auxiliary tip mounting seat 15 Cutting edge 15a Arc-shaped cutting edge part 15b Rear end side cutting edge part 16 Throwaway tip 17 Auxiliary tip 20 Protrusion 21 Tip main body 21a Throwaway tip 16 Upper surface 21c serving as a rake face 21b Lower surface serving as a seating surface of the throw-away tip 16 21c Side surface serving as a flank of the throw-away tip 16 24 Recessed groove 25 Cutting edge of the auxiliary tip 17 O Axis line of the tool body 11 T Tool rotation direction M Rear end of arcuate cutting edge 15a P Cutting edge 15 and lower surface 21b of indexable insert 16
(The straight line L and the cutting edge 15)
Top surface of the chip thickness C throwaway insert 16 in the chip thickness E _R rear position R in chip thickness E _Q tip position Q in the rear end position E _P intersection P of the tip position R cutting edge 15 at the intersection) Q cutting edge 15 of the The center of the arc formed by the arcuate cutting edge 15a as viewed from the direction facing 21a N The tangent S at the rear end M of the arcuate cutting edge 15a as seen from the direction facing the upper surface 21a of the throwaway tip S S The throwaway tip A straight line L connecting the center C and the tip position Q of the cutting blade 15 as viewed from the direction facing the upper surface 21a of the cutting surface 16. A straight line α connecting the center C and the intersection P as viewed from the direction facing the upper surface 21a of the throw-away tip 16. Angle between straight line S and straight line L when viewed from the direction facing upper surface 21a of throw-away tip 16

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yasumi Funaki 1511 Furamagi, Ishishita-cho, Yuki-gun, Ibaraki Pref. Mitsubishi Materials Corporation Tsukuba Works

Claims (6)

[Claims] An upper surface that is a rake surface, a side surface that is a flank surface, and a lower surface that is a seating surface;
The intersection ridge line portion between the upper surface and the side surface is provided with an arc-shaped cutting edge portion having a substantially 1/4 arc shape when viewed from a direction facing the upper surface and a convex curve shape as viewed from a direction facing the side surface. The tip thickness between the cutting edge and the lower surface is maximized at a predetermined position on the arcuate cutting edge portion, and the tip thickness is greater than the tip position of the cutting edge. A throwaway tip, wherein the rear end position of the blade is set to be smaller. 2. The position where the chip thickness between the cutting blade and the lower surface is maximized, when viewed from a direction facing the upper surface.
The included angle between a straight line connecting this position and the center of the arc formed by the arc-shaped cutting blade portion and a straight line connecting the center of the arc and the tip position of the cutting blade is located in the range of 35 ° to 55 °. The throw-away tip according to claim 1, wherein the tip is set as follows. 3. A rear end side of the cutting edge of the arc-shaped cutting edge portion, as viewed from a direction facing the upper surface, toward a rear end side of the arc-shaped cutting edge portion. The indexable insert according to claim 1 or 2, wherein a rear end side cutting edge portion is formed so as to extend gradually with respect to a tangent line. 4. A throw-away type ball end mill to which the throw-away tip according to claim 1 is mounted, wherein the tip is formed at a tip portion of a tool body rotated around an axis. A pair of the throw-away tips of the same shape and the same size face the upper surface in the tool rotation direction, and the lower surface is seated on the tip mounting seat, and the tip position of the cutting blade is set at the rotation center of the tool tip. And the arc-shaped cutting blade portion is positioned so as to extend from the center of rotation to the outer peripheral side of the tool rear end, so that the rotation trajectories of the cutting blade around the axis coincide with each other,
A throw-away type ball end mill, which is detachably mounted on opposite sides of the axis. 5. An auxiliary tip mounting seat is formed at a position on the rear end side of the tool body of at least one of the tip mounting seats at a position protruding one step further in the tool rotation direction than the tip mounting seat. The throw-away type according to claim 4, wherein an auxiliary tip having a cutting edge continuous to a rear end side of the cutting edge of the throw-away tip in a rotation locus around the axis is attached to the mounting seat. Ball end mill. 6. The tip of the indexable insert is formed by screwing a clamp screw inserted through a mounting hole penetrating the upper and lower surfaces into a screw hole formed in a bottom surface of the tip mounting seat. The lower surface of the throw-away tip is mounted on a mounting seat, and has a concave groove at one end communicating with the opening of the mounting hole and the other end opening at a side surface facing the tool inner peripheral side of the throw-away tip. The throw-away type ball end mill according to claim 4 or 5, wherein a projection that engages with the concave groove is formed on a bottom surface of the tip mounting seat while being formed.