U.S. patent application number 11/422454 was filed with the patent office on 2006-09-21 for tangential cutting insert and insert holder.
This patent application is currently assigned to Iscar, Ltd.. Invention is credited to Gil Hecht.
Application Number | 20060210365 11/422454 |
Document ID | / |
Family ID | 27772952 |
Filed Date | 2006-09-21 |
United States Patent
Application |
20060210365 |
Kind Code |
A1 |
Hecht; Gil |
September 21, 2006 |
Tangential Cutting Insert and Insert Holder
Abstract
A tangential indexable cutting insert can be used for metal
cutting processes in general and for radial and axial turning of a
stepped square shoulder in particular. The cutting insert exhibits
180.degree. rotational symmetry about three mutually perpendicular
axes. The cutting insert has generally "S"-shaped cutting edges
extending between raised and lowered corners. The cutting edges and
side surfaces are concave in an end view of the cutting insert. The
cutting insert enables radial and axial turning operations of a
square shoulder with unlimited depth of cut.
Inventors: |
Hecht; Gil; (Nahariya,
IL) |
Correspondence
Address: |
WOMBLE CARLYLE SANDRIDGE & RICE, PLLC
ATTN: PATENT DOCKETING 32ND FLOOR
P.O. BOX 7037
ATLANTA
GA
30357-0037
US
|
Assignee: |
Iscar, Ltd.
Tefen
IL
|
Family ID: |
27772952 |
Appl. No.: |
11/422454 |
Filed: |
June 6, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10375112 |
Feb 28, 2003 |
7073987 |
|
|
11422454 |
Jun 6, 2006 |
|
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|
Current U.S.
Class: |
407/103 ;
407/113 |
Current CPC
Class: |
B23B 2200/082 20130101;
B23B 2200/3627 20130101; Y10T 407/2274 20150115; B23B 2200/123
20130101; Y10T 407/1924 20150115; B23B 2200/083 20130101; B23B
27/1622 20130101; B23B 2205/16 20130101; B23B 27/08 20130101; B23B
2200/0423 20130101; B23B 2200/121 20130101; Y10T 407/23 20150115;
B23B 2200/207 20130101; B23B 2200/369 20130101; B23B 2205/12
20130101; B23B 27/1614 20130101; Y10T 407/235 20150115; B23B
2200/202 20130101; B23B 2200/161 20130101 |
Class at
Publication: |
407/103 ;
407/113 |
International
Class: |
B23B 27/16 20060101
B23B027/16 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 6, 2002 |
IL |
148535 |
Claims
1. An indexable cutting insert comprising: two identical opposing
end surfaces having 180.degree. rotational symmetry about a first
axis passing therethrough, a peripheral side surface extending
between the two opposing end surfaces, and a peripheral edge formed
at the intersection of each end surface and the peripheral side
surface, at least two sections of each peripheral edge constituting
cutting edges; the peripheral side surface comprising: two
identical opposing major side surfaces having 180.degree.
rotational symmetry about a second axis passing therethrough, the
second axis being perpendicular to the first axis; and two
identical opposing minor side surfaces having 180.degree.
rotational symmetry about a third axis passing therethrough, the
third axis being perpendicular to the first axis and the second
axis; a median plane being defined by the second axis and the third
axis; each end surface having four corners, two lowered corners and
two raised corners, the lowered corners being closer to the median
plane than the raised corners; the four raised corners belonging to
the two end surfaces being equidistant from the median plane; and
the four lowered corners belonging to the two end surfaces being
equidistant from the median plane.
2. The indexable cutting insert according to claim 1, wherein, in
an end view, the cutting insert is generally rectangular in
shape.
3. The indexable cutting insert according to claim 2, wherein
adjacent major and minor edges extend from a corner edge of a
raised corner to a respective lowered corner.
4. The indexable cutting insert according to claim 3, wherein the
cutting insert further comprises an insert through bore having a
bore axis.
5. The indexable cutting insert according to claim 1, wherein the
cutting insert has a first distance between the minor side surfaces
that is greater than a second distance between the major side
surfaces.
6. The indexable cutting insert according to claim 5, wherein each
peripheral edge has at least one major edge comprising a major
cutting edge which slopes from an associated raised corner towards
a first lowered corner for a major cutting edge length, the major
cutting edge length being greater than one half of the first
distance between the minor side surfaces.
7. The indexable cutting insert according to claim 6, wherein a
slope of the at least one major edge decreases adjacent the lowered
corner.
8. The indexable cutting insert according to claim 6, wherein each
peripheral edge has at least one minor edge, the at least one minor
edge comprising a minor cutting edge which slopes from said
associated raised corner towards a second lowered corner for a
minor cutting edge length, the minor cutting edge length being
approximately one half of the second distance between the major
side surfaces.
9. The indexable cutting insert according to claim 5, wherein each
peripheral edge has at least one minor edge, the at least one minor
edge comprising a minor cutting edge which slopes from an
associated raised corner towards a first lowered corner for a minor
cutting edge length, the minor cutting edge length being
approximately one half of the second distance between the major
side surfaces.
10. The indexable cutting insert according to claim 1, wherein each
minor side surface merges with an adjacent major side surface at a
corner side surface, wherein each corner side surface extends
between a raised corer of a first of the two opposing end surfaces
and a lowered corner of a second of the two opposing end
surfaces.
11. The indexable cutting insert according to claim 10, wherein,
each cutting edge comprises a major edge, a minor edge and a corner
edge, therebetween.
12. The indexable cutting insert according to claim 11, wherein
each major edge, corner edge, and minor edge is formed at the
intersection of adjacent major side surface, corner side surface,
and minor side surface, respectively with an adjacent end
surface.
13. The indexable cutting insert according to claim 12, wherein
each raised corner forms a corner cutting edge and adjacent major
and minor edges form major and minor cutting edges,
respectively.
14. The indexable cutting insert according to claim 13, wherein the
major cutting edge has a major cutting edge length that is greater
than one half of a first distance between the minor side
surfaces.
15. The indexable cutting insert according to claim 14, wherein the
minor cutting edge has a minor cutting edge length that is
approximately one half of a second distance between the major side
surfaces.
16. The indexable cutting insert according to claim 13, wherein the
minor cutting edge has a minor cutting edge length that is
approximately one half of a distance between the major side
surfaces.
17. A cutting tool comprising: the cutting insert according to
claim 1; an insert holder having an insert pocket in which cutting
insert is securely retained.
18. The cutting tool according to claim 17, wherein: the cutting
insert has an insert through bore; the insert pocket comprises a
base surface provided with a threaded receiving bore; a securing
screw extends through the insert through bore and threadingly
engages the threaded receiving bore of the base surface to secure
the cutting insert to the insert pocket.
Description
RELATED APPLICATIONS
[0001] This is a Continuation of U.S. Patent Application Serial No.
10/375,112 filed Feb. 28, 2003, now U.S. Patent No.______. The
contents of the aforementioned application are incorporated by
reference in their entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to a tangential indexable
cutting insert for use in metal cutting processes in general and
for radial and axial turning of a stepped square shoulder in
particular.
BACKGROUND OF THE INVENTION
[0003] Tangential cutting inserts, also known as on-edge, or lay
down, cutting inserts, are oriented in an insert holder in such a
manner that during a cutting operation on a workpiece the cutting
forces are directed along a major (thicker) dimension of the
cutting insert. An advantage of such an arrangement being that the
cutting insert can withstand greater cutting forces than when
oriented in such a manner that the cutting forces are directed
along a minor (thinner) dimension of the cutting insert. Another
advantage of such an arrangement is that with the minor dimension
directed perpendicular to the cutting forces it is possible to
maneuver the cutting insert between obstacles close to the
workpiece.
[0004] For turning a stepped square shoulder on a workpiece, a
cutting tool assembly requires a cutting insert with an acute
operative insert cutting corner, a tool back clearance angle along
its inoperative cutting edge and an obtuse entering angle along its
operative cutting edge. Such an entering angle enables an outwardly
directed feed out movement to square out a shoulder, in particular,
an outwardly directed radial feed out movement in the case of
external axial turning operations and an outwardly directed axial
feed out movement in the case of radial turning operations.
[0005] In view of these restrictions, cutting inserts for turning
stepped square shoulders are usually either rhomboidal or
triangular; thereby having respectively, two or three indexable
insert cutting corners for single-sided cutting inserts. Such
cutting inserts are, for example, as illustrated and described in
U.S. Pat. No. 4,632,608, each insert cutting corner being formed as
a protruding nose portion at the junction between centrally
depressed insert sides. The cutting inserts are preferably double
sided so as to be respectively formed with four or six indexable
insert cutting corners.
[0006] With a view to increasing the number of cutting corners, a
fully indexable non-tangential cutting insert is described in U.S.
Pat. No. 6,074,137. The cutting insert comprises four substantially
concave side edges extending between substantially square opposing
upper and lower surfaces. Adjacent side edges meet at a cutting
corner having an angle in the range of about
83.degree..+-.5.degree.. Although the cutting insert is
substantially square and although it offers eight cutting corners,
its depth of cut is limited. In fact, the maximal depth of cut is
limited to less than the length of a side of an imaginary square,
in which the insert is inscribed, in a top view of the insert.
Furthermore, it is not a tangential cutting insert.
[0007] FIGS. 1 and 2 show a cutting tool 20 with a tangentially
seated cutting insert 22 for both axial and radial turning
operations, also known as longitudinal and face turning operations.
The cutting insert 22 is oriented with relief angles .gamma.1 and
.gamma.2 for radial and axial turning operations, respectively. The
cutting insert 22 has one operative cutting corner 24, a first
trailing non-operative cutting corner 26 during axial turning
operations and a second trailing non-operative cutting corner 28
during radial turning operations. Major and minor cutting edges 30,
32 extend between the operative cutting corner 24 and non-operative
cutting corners 28, 26.
[0008] FIG. 3 is an illustrative drawing showing the cutting tool
20 during either radial or axial turning operations of a workpiece
33. Dashed lines 34 show an ideal square shoulder and the dash-dot
line 35 is an imaginary extension of the worked face 36 of the
workpiece 33. As can be seen, for a radial turning operation, the
second trailing non-operative cutting corner 28 and a portion of
the major cutting edge 30 are oriented such that they "extend
beyond" the imaginary extension 35 of the worked face 36 and would
engage the workpiece 33 if an attempt were made to increase the
depth of cut beyond a depth of cut, d, where the dashed line
intersects the major cutting edge 30. Thus, the depth of cut is
limited during radial turning of a square shoulder. For axial
turning in the configuration shown in FIG. 3, the depth of cut is
also limited to d. Any increase in the depth of cut would lead to a
non-square shoulder. Similarly, the insert could be configured with
an orientation such that for an axial turning operation, the first
trailing non-operative cutting corner 26 and a portion of the minor
cutting edge 32 are disposed such that they have a limited depth of
cut. Likewise, the insert could be configured with an orientation
so that it has a limited depth of cut for both axial and radial
turning operations due both to the first trailing non-operative
cutting corner 26 and a portion of the minor cutting edge 32 and
also to the second trailing non-operative cutting corner 28 and a
portion of the major cutting edge 30.
SUMMARY OF THE INVENTION
[0009] In accordance with the present invention there is provided
an indexable cutting insert, comprising: [0010] two identical
opposing end surfaces having 180.degree. rotational symmetry about
a first axis passing therethrough; [0011] a peripheral side surface
extending between the two opposing end surfaces, and [0012] a
peripheral edge formed at the intersection of each end surface and
the peripheral side surface, at least two sections of each
peripheral edge constituting cutting edges; [0013] the peripheral
side surface comprising: [0014] two identical opposing major side
surfaces having 180.degree. rotational symmetry about a second axis
passing therethrough, the second axis being perpendicular to the
first axis; and [0015] two identical opposing minor side surfaces
having 180.degree. rotational symmetry about a third axis passing
therethrough, the third axis being perpendicular to the first axis
and the second axis; [0016] a median plane being defined by the
second axis and the third axis; [0017] each end surface having four
corners, two lowered corners and two raised corners, the lowered
corners being closer to the median plane than the raised corners;
[0018] the four raised corners belonging to the two end surfaces
being equidistant from the median plane; and [0019] the four
lowered corners belonging to the two end surfaces being equidistant
from the median plane.
[0020] In an end view, the cutting insert may be generally
rectangular in shape.
[0021] Adjacent major and minor edges may extend from a corner edge
of a raised corner to a respective lowered corner.
[0022] The cutting insert may further comprise an insert through
bore having a bore axis.
[0023] The cutting insert has a first distance between the minor
side surfaces that is greater than a second distance between the
major side surfaces.
[0024] Each peripheral edge may have at least one major edge
comprising a major cutting edge which slopes from an associated
raised corner towards a first lowered corner for a major cutting
edge length, the major cutting edge length being greater than one
half of the first distance between the minor side surfaces.
[0025] A slope of the at least one major edge decreases adjacent
the lowered corner.
[0026] Each peripheral edge may have at least one minor edge, the
at least one minor edge comprising a minor cutting edge which
slopes from an associated raised corner towards a first lowered
corner for a minor cutting edge length, the minor cutting edge
length being approximately one half of the second distance between
the major side surfaces.
[0027] Each peripheral edge may have both a minor edge and a major
edge which slope from a common associated raised corner and towards
first and second lowered corners.
[0028] Each minor side surface may merge with an adjacent major
side surface at a corner side surface, wherein each corner side
surface extends between a raised corner of a first of the two
opposing end surfaces and a lowered corner of a second of the two
opposing end surfaces.
[0029] Each cutting edge comprises a major edge, a minor edge and a
corner edge, therebetween.
[0030] Each major edge, corner edge, and minor edge may be formed
at the intersection of adjacent major side surface, corner side
surface, and minor side surface, respectively with an adjacent end
surface.
[0031] Each raised corner may form a corner cutting edge and
adjacent major and minor edges form major and minor cutting edges,
respectively.
[0032] The major cutting edge may have a major cutting edge length
that is greater than one half of a first distance between the minor
side surfaces.
[0033] The minor cutting edge has a minor cutting edge length that
is approximately one half of a second distance between the major
side surfaces.
[0034] In another aspect, the present invention is directed to a
cutting tool comprising the above-described cutting insert and an
insert holder having an insert pocket in which cutting insert is
securely retained.
[0035] The cutting insert has an insert through bore, the insert
pocket comprises a base surface provided with a threaded receiving
bore, and a securing screw extends through the insert through bore
and threadingly engages the threaded receiving bore of the base
surface to secure the cutting insert to the insert pocket.
BRIEF DESCRIPTION OF THE DRAWINGS
[0036] For a better understanding, the invention will now be
described, by way of example only, with reference to the
accompanying drawings in which:
[0037] FIG. 1 is of a side view of a typical prior art cutting
tool;
[0038] FIG. 2 is an end view of the cutting tool in FIG. 1;
[0039] FIG. 3 is a plan view of the cutting tool in FIG. 1 in a
turning operation.
[0040] FIG. 4 is a perspective view of the cutting insert in
accordance with the present invention;
[0041] FIG. 5 is a first side view of the cutting insert in FIG.
4;
[0042] FIG. 6 is a second side view of the cutting insert shown in
FIG. 4;
[0043] FIG. 7 is a cross-sectional view of the cutting insert shown
in FIG. 6 taken along C-C;
[0044] FIG. 8 is an end view of the cutting insert shown in FIG.
4;
[0045] FIG. 9 is a side view of a cutting tool in accordance with
the present invention;
[0046] FIG. 10 is an end view of the cutting tool in FIG. 9;
[0047] FIG. 11 is a plan view of the cutting tool in accordance
with the present invention in an axial turning operation;
[0048] FIG. 12 is a detailed view of FIG. 11;
[0049] FIG. 13 is a plan view of the cutting tool in accordance
with the present invention in a radial turning operation;
[0050] FIG. 14 is a detailed view of FIG. 13;
[0051] FIG. 15 is a perspective exploded view of cutting tool in
accordance with the present invention; and
[0052] FIG. 16 is an end view of a cutting insert shown insert in
accordance with the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0053] Attention is first drawn to FIGS. 4 to 8, showing a
tangential indexable cutting insert 38 in accordance with present
invention. The cutting insert 38 is generally manufactured by form
pressing and sintering a cemented carbide, such as tungsten
carbide, and can be coated or uncoated. The cutting insert 38 is
generally rectangular in an end view and comprises two identical
end surfaces 40, and a peripheral side surface 42 extending between
the end surfaces 40. The cutting insert 38 and the end surfaces 40
have 180.degree. rotational symmetry about a first axis R1 that
passes through the end surfaces 40. Since the end surfaces 40 are
identical, only one will be described, it being understood that the
other end surface 40 has identical structure.
[0054] The peripheral side surface 42 comprises two opposed
identical minor side surfaces 44, two opposed identical major side
surfaces 46, and four opposed corner side surfaces 48. Adjacent
major and minor side surfaces 46, 44 merge at a common corner side
surface 48. The cutting insert 38 and the major side surface 46
have 180.degree. rotational symmetry about a second axis R2
perpendicular to the first axis of rotational symmetry R1 and
passing through the major side surfaces 46. The cutting insert 38
and the minor side surface 44 also has 180.degree. rotational
symmetry about a third axis R3 that passes through the minor side
surfaces 44 and is perpendicular to both the first and second axis
of 180.degree. rotational symmetry R1, R2.
[0055] The peripheral side surface 42 intersects each end surface
40 at a peripheral edge 50. The peripheral edge 50 comprises two
identical opposed major edges 52, two identical opposed minor edges
54, and four opposed corner edges 56. Adjacent major and minor
edges 52, 54 merge at a common corner edge 56. The major edges 52
are formed at the intersection of the major side surfaces 46 with
the end surfaces 40, the minor edges 54 are formed at the
intersection of the minor side surfaces 44 with the end surfaces
40, and the corner edges 56 are formed at the intersection of the
corner side surfaces 48 with the end surfaces 40.
[0056] For further description of the geometrical properties of the
cutting insert 38, a minor plane P1, to which the major edges 52
are generally parallel in an end view of the cutting insert 38, is
defined by the first and third axis of rotational symmetry R1, R3.
A major plane P2, to which the minor edges 54 are generally
parallel in an end view of the cutting insert 38, is defined by the
first and second axis of rotational symmetry R1, R2. A median plane
M, which is perpendicular to both the minor and major plane P1, P2,
is defined by the second and third axis of rotational symmetry R2,
R3. A width dimension D1 of the cutting insert 38 is defined as a
maximum distance dimension between the minor side surfaces 44
measured parallel to the third axis R3. A length dimension D2 of
the cutting insert 38 is defined as a maximum distance dimension
between the major side surfaces 46 measured parallel to the second
axis R2. For the tangential cutting insert 38, the width dimension
D1 is greater than the length dimension D2.
[0057] Associated with each of the four corner edges 56 of a given
end surface are four corners comprising two diametrically opposed
raised corners 58 and two diametrically opposed lowered corners 60.
The lowered corners 60 are closer to the median plane M than are
the raised corners 58. In a side view of either of the minor side
surfaces 44, all four corners 58, 60 are equidistant from the minor
plane P1. In a side view of either of the major side surfaces 46,
all four corners 58, 60 are equidistant from the major plane P2.
Each corner side surfaces 48 extends between a given raised corner
58 of one end surface 40 and an adjacent lowered corner 60 on the
opposing end surface 40. Each corner side surface 48 has uniform
radius of curvature along its length, and typically forms an arc
angle of 95.degree..+-.3.degree.. The alternating raised and
lowered corners 58, 60 enable the cutting insert 38 to have four
same-handed raised corners 58 for indexing.
[0058] Adjacent major and minor edges 52, 54 extend from the corner
edge 56 of a given raised corner 58 with a variable slope to a
respective lowered corner 60. In a side view of the cutting insert
38, adjacent each raised corner 58, the slope of each major edge 52
(see FIG. 6) is generally constant with the major edge 52
substantially parallel to the median plane M. Moving along the
major edge 52 towards an adjacent lowered corner 60, the slope
gradually increases and finally decreases adjacent the lowered
corner 60. As can be seen in FIG. 5 each minor edge 54 has a
generally similar form to that of the major edges 52. Thus in a
respective side view, each major and minor edge 52, 54, has a
similar wavy elongated "S"-shape.
[0059] In an end view of the cutting insert 38, the major edges 52
are concave. In other words, the major edges 52 are recessed in an
end view wherein, the distance between the opposed major edges 52
varies from approximately D2 adjacent the corner edges 56 to a
minimum distance d2 at the intersection of the major edges 52 with
the major plane P2. The minimum distance d2 is defined by D2-t. In
a non-binding example, t is greater than or equal to 0.3 mm and
less than or equal 0.4 mm. In an end view of the cutting insert 38,
each major side surface 46 is also concave, being recessed in the
same manner as its associated major edge 52. It should be noted
that the variation of the distance between the opposed major edges
52 (and likewise the opposed major side surfaces 46) need not
decrease uniformly from the maximum value D2 to the minimum value
d2.
[0060] In an end view of the cutting insert 38, the minor edges 54
are also concave, in a similar manner to the major edges 52. The
distance between the opposed minor edges 54 in an end view, varies
from approximately D1 adjacent the corner edges 56 to a minimum
distance d1 at the intersection of the minor edges 54 with the
minor plane P1. The minimum distance d1 is defined by D1-s. In a
non-binding example, s is greater than or equal to 0.05 mm and less
than or equal 0.25 mm. Likewise, in an end view of the cutting
insert 38, each minor side surface 44 is concave, being recessed in
the same manner as its associated minor edge 54. The variation of
the distance between the opposed minor edges 54 (and likewise the
opposed minor side surfaces 44) need not decrease uniformly from
the maximum value D1 to the minimum value d1.
[0061] It will be appreciated that whereas the whole of the
peripheral edge 50 can function as a cutting edge, in practice,
sections of the peripheral edge 50 adjacent the lowered corners 60
will not function as cutting edges. In accordance with a specific
application of the present invention, each given peripheral edge 50
has an effective major cutting edge 66 that extends from an
associated given raised corner 58 along the given corner edge 56
and the given major edge 52 for a given major cutting edge length
L1, which is greater than one half of the width dimension D1.
Additionally, in accordance with the specific application of the
present invention, each peripheral edge 50 has an effective minor
cutting edge 68 that extends from an associated given raised corner
58 along the given corner edge 56 and the given minor edge 54 for a
given minor cutting edge length, L2, which is approximately one
half of the length dimension D2, and more preferably is slightly
greater than one half of D2.
[0062] Attention is now drawn to FIGS. 9 and 10, showing side views
of a cutting tool 70 in accordance with the present invention. The
cutting insert 38 has relief angles .gamma.1, .gamma.2 and presents
an operative raised corner 58' outwardly projecting from the
cutting tool 70.
[0063] Attention is now drawn to FIGS. 11 and 12, showing the
cutting insert 38 in an insert holder 72 in a plan view during an
axial turning operation of a stepped square shoulder 74 of a
workpiece 76 rotating about an axis A. Adjacent the stepped square
shoulder 74 is a operative major edge 52', an operative corner edge
56' of an operative raised corner 58' an operative minor edge 54',
and a trailing lowered corner edge 78'. It will be appreciated that
an operative minor edge 54' constitutes a secondary cutting edge or
wiper and that only a small section of it adjacent the operative
corner edge 56' contacts the workpiece 76. Due to the relief angles
.gamma.1, .gamma.2 and any other required orientation of the
cutting insert 38, an entering angle K is formed between the major
edge 52 and the feed direction FI, and a back clearance angle Kn is
formed between the operative minor edge 54' and a cylindrical
surface 80 of the workpiece 76. As can be seen, the trailing
lowered corner edge 78' is completely relieved from the cylindrical
surface 80 of the workpiece 76, whereby the depth of cut for axial
turning is unlimited.
[0064] Attention is now drawn to FIGS. 13 and 14, showing the
cutting insert 38 in an insert holder 72 in a plan view during an
radial turning operation of a cylindrical surface 80 of a workpiece
76 rotating about an axis A. Adjacent the cylindrical surface 80 is
an operative major edge 52', an operative corner edge 56' of the
operative corner edge 58' an operative minor edge 54', and a
trailing lowered corner edge 78''. It will be appreciated that an
operative major edge 52' constitutes a secondary cutting edge or
wiper and that only a small section of it adjacent the operative
corner edge 56' contacts the workpiece 76. Due to the relief angles
.gamma.1, .gamma.2 and any other required orientation of the
cutting insert 38, an entering angle K is formed between the
operative minor edge 54' and the feed direction F2, and a back
clearance angle Kn is formed between the operative major edge 52'
and a stepped square shoulder 74 of the workpiece 76. As can be
seen, the trailing lowered corner edge 78'' is completely relieved
from the stepped square shoulder 74 of the workpiece 76, whereby
the depth of cut for radial turning is unlimited.
[0065] The seating and securing of the cutting insert 38 will now
be described with reference to FIG. 15, showing various elements
not mentioned above. These elements include two frustums 82 on each
end surface 40, an insert pocket 84 of the insert holder 72, an
insert through bore 86, a securing screw 88, a shim 90, and a shim
screw 92.
[0066] The insert pocket 84 comprises first and second side walls
94, 96 uprightly extending from a base surface 98 of the insert
pocket 84. The shim 90 comprises a top surface 100, a flat opposing
bottom surface 102, and a perimeter surface 104 extending
therebetween. The top surface 100 of the shim 90 comprises a raised
area 106 extending away from the bottom surface 102 of the shim 90.
A shim through bore 108 extends between the top surface 100 and the
bottom surface 102. The two frustums 82 of each end surface 40
extend away from the median plane M and are located on either side
of the major plane P2. The frustums 82 are likely to impede chip
flow, thereby limiting the lengths L1, L2 of the major and minor
cutting edges 66,68.
[0067] The shim 90 is secured in the insert pocket 84 with its
bottom surface 102 abutting the second side wall 96. The shim screw
92, extends through the shim through bore 108 and threadingly
engages with a threaded second bore 110 passing through the second
side wall 96, securing the shim 90 to the insert pocket 84. The
cutting insert 38 is secured in the insert pocket 84 with a
non-operative end surface 40 adjacent the top surface 100 of the
shim 90. The first side wall 94 abuts the minor side surface 44 of
the cutting insert 38, and the base surface 98 abuts the major side
surface 46. The two frustums 82 of a non-operative end surface 40
abut the raised area 106 of the top surface 100 of the shim 90. The
securing screw 88 extends through the insert through bore 86 and
threadingly engages a threaded receiving bore 112 in the base
surface 98 of the insert pocket 84.
[0068] It will be appreciated that the particular form of the end
surfaces 40 will depend on the design factors that take into
account various working conditions. For example, in order to
increase the effective cutting wedge angle, a land 114 is provided
adjacent the peripheral edge 50 (see FIG. 7). A rake surface 116
slopes downwardly and inwardly from the land 114. If desired the
rake surface can be provided with suitable chip control
elements.
[0069] It is advantageous to have recessed side surfaces and side
edges to take into consideration manufacturing tolerances so that
the sides will not become convex or partially convex, when viewed
in an end view, and interfere with the workpiece. It is possible to
use straight side edges, i.e., the major side surface 46 and the
major edges 52 could be straight, as in FIG. 16, either by tight
manufacturing tolerances during pressing and sintering or by
additional steps of grinding.
[0070] Although the present invention has been described to a
certain degree of particularity, it should be understood that
various alterations and modifications could be made without
departing from the spirit or scope of the invention as hereinafter
claimed.
* * * * *