Indexable insert

Details Indexable insert Indexable insert

1999-01-19

2001-05-22

Tsai, Henry (Department: 3722)

Cutters, for shaping

Including tool having plural alternatively usable cutting edges

With integral chip breaker, guide or deflector

C407S115000, C407S116000

Reexamination Certificate

active

06234726

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an indexable insert which is attached to a tool body of a cutting tool and is used for cutting metal materials, etc.
2. Discussion of the Background
Hitherto, there has been known an indexable insert in which a chip breaker having a specified sectional configuration is formed on a rake face for the ejection of chips. In such an indexable insert, in order to improve the chip ejection efficiency, the slope of a wall surface
2
of the chip breaker, which rises from a rake face
1
, has been set depending on the depth of the cut (infeed) as shown in
FIGS. 26 and 27
, for example. Specifically, an indexable insert having a cross-section shown in
FIG. 26
is intended to improve the chip ejection efficiency in a low infeed range by setting an angle &agr; of the slope of the breaker wall
2
so that the breaker wall rises steeply from an intersection
3
between rake face
1
and the breaker wall. Also, an indexable insert having a cross-section shown in
FIG. 27
is intended to improve the chip ejection efficiency in a high infeed range by setting the angle &agr; to be so small that the breaker wall
2
rises gently from the intersection
3
.
These conventionally known indexable inserts, however, have disadvantages as follows. In the indexable insert shown in
FIG. 26
, chips are apt to stuff, so that cut resistance is increased in the high infeed range because the height from an edge
4
to a boss surface
5
, i.e., the height h of the breaker wall
2
, is too large. Also, in the indexable insert shown in
FIG. 27
, the breaking action to make chips curled is weak in the low infeed range because the slope of the breaker wall
2
is too gentle. Accordingly, chips tend to become more elongate and the chip ejection efficiency is reduced. Thus, each of the indexable inserts having the above-described constructions have a superior chip ejection ability under one cutting condition, i.e., in the low infeed range or the high infeed range, but suffers from a lowering of the chip ejection efficiency or an increase of the cut resistance under the other cutting condition.
Meanwhile, as shown in
FIGS. 28
to
31
, by way of example, an indexable insert having a chip breaker with a varied sectional configuration around the corner (nose portion) of a rake face has also been proposed. The tip shown in
FIGS. 28
to
31
is constructed such that an upper surface of a tip body
11
, which is formed as a flat plate which is substantially rhombic in plan, serves as a rake face
12
, lateral surfaces of the tip body
11
each serve as a flank face
13
, and an edge
14
is formed along the ridge defined at an intersection between the rake face
12
and each flank face
13
, i.e., along the ridge defined by each side of the rhombic rake face
12
. Further, at two of the four corners C, C of the rake face
12
, where the edges
14
adjacent to each other intersect at an acute angle, a convex arc-shaped nose portion edge
15
is formed in a smooth continuous relationship with the edges
14
on both sides. The rake face
12
is recessed at a specified slope as it extends inwardly from the edge
14
and the nose portion edge
15
. The edge
14
and the nose portion edge
15
thus have a positive rake angle &thgr;.
In an inner area of the rake face
12
, a chip breaker
16
protrudes upwardly from the rake face
12
with gaps left from the edges
14
and the nose portion edges
15
. The chip breaker
16
is formed, as shown in
FIG. 28
, such that it has a breaker wall surface
17
with a rhombic shape and a size smaller than the rake face
12
inwardly of the edges
14
, in a plan view looking in a direction facing the rake face
12
with a uniform gap left from the edges
14
. At the corners C, C adjacent to the nose portion edges
15
, it extends in the diagonal direction connecting the corners C, C so as to terminate in positions close to the nose portion edges
15
. Reference numeral
18
in
FIG. 28
denotes an attachment hole in which is inserted a clamp screw or the like used for attaching the tip body
11
to a tool such as a bite.
In practical cutting with the above-mentioned indexable insert, when an infeed and/or a feed is relatively small and an area just around the nose portion edge
15
is used as occurs in finish cutting, the nose portion edge
15
produces chips which are thin and have a small width. These chips are quickly broken into pieces by the above-mentioned indexable insert because they strike against a fore end of the chip breaker
16
positioned close to the corresponding nose portion edge
15
immediately after being produced. On the other hand, when an infeed and/or a feed is relatively large and an area extending from the nose portion edge
15
to the edge
14
is used as occurs in rough cutting, the nose portion edge
15
produces chips which are thick and have a large width. These chips are broken into pieces by the above-mentioned indexable insert in such a manner that they are subject to resistance while sliding over the rake face
12
between the edge
14
and the chip breaker
16
, and then strike against the chip breaker
16
, whereby they are so bent and curled as to break into pieces. Accordingly, the above-mentioned indexable insert can achieve efficient chip ejection in general universal cutting ranging from rough cutting to ordinary finish cutting.
However, when an infeed and/or a feed is set to a smaller value than in the ordinary finish cutting as occurs in, e.g., superfinish cutting required in precision machining, the produced chips become harder to break into pieces because they are thinner, have a narrower width and tend to be more elongate. At the same time, the part of the nose portion edge
15
which is used for cutting and produces chips also becomes smaller. This results in a difficulty in causing the produced chips to surely strike against the fore end of the chip breaker
16
and break into pieces for ejection even with the universal cutting tip shown in
FIGS. 28
to
31
. When used in superfinish cutting, therefore, such a universal cutting tip must be modified to make the produced chips surely strike against the breaker wall surface
17
at the fore end of the chip breaker
16
such that the fore end of the chip breaker
16
is positioned closer to the nose portion edge
15
, or that the chip breaker
16
has an increased height in a direction of thickness of the tip body
11
, or that the breaker wall surface
17
at the fore end of the chip breaker
16
protrudes more steeply in its entirely.
These modified constructions however are not satisfactory for the following reasons. If the fore end of the chip breaker
16
is positioned too close to the nose portion edge
15
, when the modified indexable insert is employed in general universal cutting, particularly in rough cutting during which thick and wide chips are produced, the chips strike against the chip breaker
16
before sliding a sufficient distance over the rake face
12
, and a pocket space defined between the edge
14
or the nose portion edge
15
and the chip breaker
16
becomes small. As a result, the chips are apt to stuff and the chip ejection ability deteriorates which is not the desired result. Also, easier stuffing of the chips may cause the cut resistance to be so increased as to cause severe vibration, deterioration of finished surface accuracy and shortening of the tip life.
Further, if the fore end of the chip breaker
16
is positioned closer to the nose portion edge
15
, the recessed inflecting point P where the breaker wall surface
17
at the fore end of the chip breaker
16
intersects the rake face
12
is also positioned closer to the nose portion edge
15
. The closer position of the nose portion edge
15
to the recessed inflecting point P, however raises a fear that the tip body
11
may break at the recessed inflecting point P when the tip is used to cut hard materials, because stresses caused by the cutting load acting upon the nose portion edge
15
tend to be concentrated on

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