Note: Descriptions are shown in the official language in which they were submitted.
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INDEXABLE_FINI'SHING I
- The subject invention relates to an indexable
finishing insert for use in a milling cutter tool.
More particularly, a finishing insert is disclosed
having curved cutting edges to provide an accurate
finishing cut in a workpiece. The front and rear
rake surfaces of the new and improved finishing insert
of the subject invention are planar in configuration
and thus maintain the structural integrity of the
insert. Further, the mounting of the insert is
facilitated by both the planar configuration of the
rake surfaces~, as well as by the inclusion of planar
locating lands on~each'of the edge faces of the insert.
Ba'ckgr~und of t-he Invention - Indexable inserts,
15~ formed from a hardéned material are used in conjunction
with cutting tools in milling operations when machining
cast iron,~aluminum or steel parts. To provide for
smoo~h, high~quality cutting pro~iles, finishing
inserts have been developed whiah~have elliptical
~ cutting edges. An ellipitical cutting edge allows
for the removal of an extermely thin, tapered chip of
metal leaving a cut surface which is rounded and
amoothed~ Typical example~s of the finishing inserts
found in the prior;art~ar~e~disclosed in U.S. Patent
25 ~ Mo. 3,279,034-issued on October 18, 1966 to Kaiser for
an '~Indexable Clltting~B~lade"~; D.S. Patent No.3,434,190,
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issued on March 25, 1969 to Kaiser, for an "Indexable
Cutting Blade"; and U.S. Patent No. 3,762,005, issued
on October 2, 1973 to Erkfritz, for an "Indexable
Cutting Insert". These patents disclose indexable
inserts, having a cutting edge which is ellipitically
curved. More specifically, the patents to Kaiser
disclose finishing inserts where the rake faces of the
inserts are altered to provide a curved cutting edge.
The earlier patent to Kaiser alters the front rake
face of the insert by curving its outer edges to
conform to the surface of an imaginary sphere. The
latter Kaiser patent discloses an insert wherein the
rake face is grooved to define a curved cutting edge.
Similarly, the present to Erkfritz discloses a finishing
insert having grooves undercut along the length of each
rake surface.
; The indexable inserts disclosed in the prior art
were useful in providing finishing type cuts in a
wo~kpiece when used in conjunction with a milling tool.
However, the changes necessary to alter a standard
insert to an elliptical finishing insert resulted in
the reduction of the integrity of the rake face of the
insert. More particularly, the rounding of the rake
face of the insert, or the addition of grooves thereto,
for defining the elliptical cutting edges of the insert,
effectively reduced the thickness of the insert thereby
resulting in a loss of structural strength along the
;; ;~ cutting edges. These changes also effectively reduced
the surface area of the locating lands which were provided
3~ on the edge faces of the inserts. The locating lands
were provided to facilitate clamping of the insert
within the pocket of a cutter body and serve to locate
the inserts in a precise position relative to the body
thereby creating the desired axial and radical rake
angles.
In addition to the above shortcomings of the prior
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art systems, it is noted that when these prior art
inserts having modifications designed to produce
ellipitical cutting edges were inserted into a pocket
of a milling cutter, the effective geometry of the
S pocket was altered such that the desired rake angle
was not achieved.
~ ccordingly, it is an object of the subject
invention to provide an indexable finishing insert
including planar fronk and rear rake surfaces which
provide for the improved structural integrity o~ the
insert.
It is a further object of the subject invention
to provide an indexable finishing insert wherein each
shape face thereof includes a planar locating land to
facilitate the mounting of the insert in the pocket
of the cutter body.
It is another object of the subject invention to
provide an indexable finishing insert having improved
: rake face and locater integrity, and in addition, does
not alter the rake geometry inherently ~uilt into the
insert pockets of milling cutters.
It is still a further object of the subject
invention to provide an indexable finishing insert
: having either a positive or a negative geometry.
Summary of_the Invention - In accordance with these
and other objects of the subject invention, an inde~able
finishing insert is provided for use with a milling
: cutter. The subject insert comprises a flat wafer
of cutting material such as a hardened tungsten
~: 30 carbide, having parallel, spaced front and rear planar
: rake surfaces and a plurality of edge faces disposed
therebetween. The rake faces are formed in an equilateral
polygonal configuration and in the preferred embodiments
are square. The side edges of at least one of the
~ 35 square rake surfaces correspond to the cutting edges of
: the insert, and are arcuate in configuration having a
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radius of c~rvature which is several times greater
than the width of the planar surface of the insert.
The arcuate curvature of the cutting edges, which
defines a drop at the corners of the insert, allows
the insert to be used ~or fini~hing purposes. More
specifically, a corner drop is provided which corres-
ponds to the spacing between the end points of the
cutting edges and an imaginary line tangent to the
midpoint of the arcuate cutting edge. This arrangement
allows the insert to be used for machining tapered cuts,
result in a smooth, flat finish for the workpiece.
The intermediate portion of each edge Eace of the
subject insert is substantially planar and defines a
locating land to facilitate the clamping of the insert
in the pocket of the milling cutter. The locating of
the planar lands corresponds to the location of the
edge faces of a standard insert such that when the
insert is mounted in a milling cutter, the inherent
geometry of the insert pocket does not have to be
altered. In order to provide clearance along the edge
faces, the opposed ends or corner portions of the edge
faces are contoured and slope away from the cutting
edge. The configuration of the contoured corner
portions of the edge faces is determined by the
~particular geometry of the insert, as well as the
particular geometry of the insert pocket of the milling
cutter. The indexable insert of the subject invention
may be adapted for use with both positive and negative
clearance angle geometries.
30 ~ ~ Description_of the Drawings
Figure 1 is perspective view of a standard, posi-
tively cleared, indexable insert of the prior art.
Figure 2 is a perspective view of an indexable
finishing insert in accordance with the subject invention.
~ Figure 3 is a front elevational view of the
finishing insert of the subject invention.
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Figure 4 is a side elevational view of the finishing
insert of the subject invention.
Figure 5 is a partial side elevational view of the
finishing insert of the subject invention, illustrating
the slope at a corner portion of the edge face.
Figure 6 is a partial sectional view of the
finishing insert of the subject invention, taken along
the liner 6-6 in Figure 3.
Figure 7 is a partial sectional view of the
finishing insert of the subject invention, taken along
line 7-7 in Figure 3.
Figure 8 is a partial, rear elevational view of
the finishing insert of the subject invention.
Figure 9 is a perspective view of a second
embodiment of the finishing insert of the subject
invention.
Figure 10 is a front elevational view of the
second embodiment of the finishing insert of the
subject invention.
`~ ~ 20 Figure 11 is a side elevational view of the second
embodiment of the finishing insert of the subject
invention.
Figure 12 is a partial side elevational view of
the second embodiment of the finishing insert of the
subject invention, illustrating the slope at the corner
portions of the edge face.
Figure 13 is a partial sectional view of the second
embodiment of the finishing insert of the subject
invention, taken along line 13-13~of Figure 10.
Description of th Preferred Embodiments -
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Referring now mbre particularly to Figure 1, a
standard prior art indexable insert is illustrated and
is indicated generally by the numeral 10. The lnsert
10 is~formed o~a flat wafer of cutting material,
usually a hardened tungsten carbide, and includes
opposed front and rear planar rake surfaces 12, 14.
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The side edges 16 of the front planar surface 12
correspond to the sharpened, clltting edges of the
insert. ~ plurality of generally trapezoidal edge
faces 18 are formed between the opposed rake surfaces
12, 14 and are disposed at an acute angle relative
to a plane normal to the planar surfaces of the insert
10. More specifically, the dimensions of the front
:rake surface 12 are larger than the dimensions of the
rear rake surface 14 such that each edge face 18 slopes
inwardly from the front rake surface 12 to the rear
surface 14. The angle of the edge faces is provided to
allow clearance therealong when the insert is mounted
in a pocket of a cutter body having a positive axial
ra]ce geometry. More particularly, the prior art insert
10, as illustrated in Figure 1, would generally be
used in conjunction with a milling cutter (not shown)
having a pocket geometry which results in a positive
rake angle between the front planar surface 12 and the
workpiece. By inwardly angling the edge faces 18 of
the insert an amount greater than the positive rake
angle, clearance may be provided along the edge faces,
as is well known in the prior art. As illustrated in
:
Figure 1, the edge faces are sloped away from a plane
normal to rake surfaces 12, 14 at an angle "a" of about
~:25 11. By this arrangement, when the prior art insert
:~10 is mounted in a pocket of a milling tool having a
positive rake geometry, only the cutting edges 16 and
:not the edge faces 18 will contact the workpiece.
Prior art insert 10 usually clamped into the
:30 pocket body, along the front and rear surfaces 12, 14,
such that one cutting edge 16 is disposed in an active
cutting position. Further, if for example, cutting
edge 16a is~in the active position, the insert may
be additionally clamped and supported along the
: 35 inactive edge faces 18b, 18c, and 18d. By using the
~; edge faces l~ for additional support, the maintenance
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of the desired rake angles of t:he insert within the
pocket body is facilitated. The prior art insert 10
is used to form grooved cuts in a workpiece. However,
the grooved cuts milled by this insert tend to be
uneven and irregular, especially adjacent edges of
the insert.
Turning to Figure 2, in accordance with the
subject invention, a new and i~lproved indexable
finishing insert 20 is provided having arcuate cutting
edges which are capable of creating smooth finishing
cuts, and which insert is of high structural integrity.
Further, the new and improved insert 20 does not alter
the pocket geometry of a milling cutter when mounted
therein.
~ The indexable finishing insert 20 is preferably
formed from a hardened tungsten carbide material and
has a flat wafer configuration including parallel,
spaced front and rear planar rake surfaces 22 and 24.
A plurality of trapezoidal edge faces 26 are disposed
therebetween with at least the intermediate portions
thereof corresponding to the inclined planar surfaces
16 of the indexable insert of the prior art, as more
fully described hereinafter.
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~` ~ As more clearly illustrated in Figures 3 and 8,
the front planar surface 22 has dimensions slightly
larger than the dimensions of the rear planar surface
24 such that the edge faces 26 are trapezoidal in
configuration and are inwardly angled to provide
clearance therealong when the insert is mounted in a
milling tool having a positive rake geometry. The
four side edges 28 of the front rake surface 22 cor-
respond to the sharpened cutting edges of the insert 20.
As illustrated in Figure 3, the cutting edges are
arcuate in configuration and have a radius which is
35~ several times greater than the width of the insert.
The arcuat curvature of the cutting edges 28 functions
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to define a drop "x", at the corners of the insert.
As illustrated in Fiyure 3, the corner drop "x"
corresponds to the spacing between a point "b" at the
end of the cutting edge 28, and a line "c" which is
tangent to the midpoint "d" of the cutting edge 28.
In the preferred embodiment of the subject invention,
wherein the insert has a width of approximately .75
o~ an inch, it is preferable that a corner drop "~"
of .003 to .006 of an inch, be provided.
In accordance with the subject invention, each
edge face 26, as illustrated in Figures 2 and 4, is
provided with a planar, locating land 30 and opposed,
contoured corner portions ~2. To achieve this
arranyement, the opposed ends of the edge faces of
the insert are confiyurated to allow for adequate
clearance therealong during a milling operation. More
specifically, a clearance angle "y" must be provided
at the opposed corner portions 32, as measured from
the end points "b" of each cutting edge 28 to the rake
surface 24. The amount of slope or clearance angle "Y"
~`~ of the end portions 32 of the edge faces 26 is deter-
mined by the geometry of the insert, as well as the
pocket geometry of the milling cutter, as more fully
described hereinafter.
The planar land 30 of the subject insert 20
corresponds to the edge face 18 of the insert 10 of
the~prior art. More particularly, to from the edge
faces 26 of~the subject invention, only the corner
portions 32 are modified while the intermediate portion
remains unaltered. With conventional pocket geometries
; at least 70~ of the edge faces 26 may be left unaltere.
The new and improved finishing insert 20 of the subject
invention is thereby provided with edge faces 26 having
a substantial unaltered portion such that the insert
20 may be securely clamped in the insert pocket of
- ~ a milling cutter along both the planar front and rear
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rake surfaces 22 ancl 24 and along the flat planar
locating lands 30. Thus, by maintaining the planar
configuration of the rake faces 22, 24, as well as the
locator integrity of the edge faces 26, an insert
capabl~ of making finishing cuts may be mounted on a
milling cutter in a manner similar to the prior art
inserts such that the inherent pocket geometry of
the cutter is unaltered.
Figures 6 and 7 are provided to illustrate the
configuration of the edge faces 26 of the subject invention.
While the partial cross-sectional views illustrate only
one edge face, it is to be understood that the subject
indexable insert is symmetrically arranged such that edge
face is identical in configuration. Figure 6, which
illustrates the configuration of the edge face 26 at a
point adjacent the corner of the insert, indicates the
slope along the corner portion 32 of the edge face 26.
Figure 7, a cross-sectioned view taken at the midpoint
of the cutting edge 28, illustrates that a portion of
the locating land 30 extends to the midpoint. As
illustrated in Figure 4, the configuration of the
locating land 30 in this embodiment of the subject
invention is semi-circular. The planar surface of the
locating land 30 corresponds essential to the surface
of the edge face 18 of the prior art insert 10. Thus,
the angle of inclination "a" (Figure 4) of the locating
land 3~0 is preferably identical to the angle of
inclination "a" of the edge face 18 of the prior art
inser-t 10. In this illustrated embodiment, an 11
30; clearance angle is provided to allow the insert 20 to
be mounted on a milling cutter with a conventional
positive rake angle. More specifically, insert 20 is
intended to be used in a milling cutter having a pocket
geometry~which provides for between 5 and 7 positive
axial rake.
As noted above, the angle "a" of the edge face 28
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is suf~icient to provide clearance therealong when the
insert is provided with standaxd, straight cutting
edges. However, when the insert is modified for finishing
cuts, the portions of the opposed ends of edge faces
adjacent the curved cutting edges are insufficiently
cleared. Therefore, in accordance with the subject
invention, the end portions 32 of the edge faces 26 are
reduced or cleared away from each cutting edge 28 an
amount sufficient to provide clearance along the entire
face 26 during the cutting operation. It has been
found that the slope of the edge portions 32 of the
edge faces 26 must be at least 2 greater than the
: positive axi.al rake geometry of the milling cutter.
As illustrated in Figure 5, the amount of slope "y"
at corner portions 32 of the edge faces is measured as
: the angle between the surface of the corner portion
"f", and the plane "g" normal to the plane of the
rake faces 12, 14. The insert 20 illustrated in
Figures 2-8 is provided with a corner slope of approxi-
mately 9 such that it may be utilized in a conventional
milling cutter having a pocket geometry of up to 7
positive axial rake~ Thus, the new and improved
arrangement of the edge faces 26 of the insert 20
permits the:insert to be mounted with a positive axial
rake while afforcing clearance along the entire edge
face. The above disclosed arrangement is superior
; ~ to the prior art inserts in that the structural
integrity of both the front and rear rake surfaces is
maintained and in addition, at least 70% of the edge
faces~are retained to ac:t as locating lands 30, such
~: : that the insext may be securely clamped within the
pocket of a milling cutter without altering its effective
geometry.~
: Inserts can be modified in accordance with the
subject invention for use with milling cutters having
various pocket geometries. For example, should the
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positive insert 20 of the type illustrated in Figures
2-8 be used with a milling cutter having a less severe
axial rake, khe slope "y" and hence the amount of
clearance along the edge faces 26 may be correspond-
ingly reduced. When the amount of clearance isreduced, the area of the locating lands 30 will be
increased thereby further facilitating the rnounting
of the insert.
As is apparent rom the figures, the finishing
insert 20 is symmetrically arranged such that it may
be indexed to expose any one of the cutting edges 28
of the front rake surface 12 for active use. More
specifically, when a single edge 28 becomes worn or
dull through use, the insert may be unclamped and
rotated 90 to expose a fresh, sharpened cutting edge.
The insert may then be reclamped in the pocket body
of the milling cutter for continued use.
Inserts having varying geometries may be modified
in accordance with the subject invention. Figures 9-13
illustrate a second embodiment of the subject invention
as used with a conventional 90 insert. More specifically,
insert 50 is formed of a flat wafer of a tungsten
carbide material and includes parallel spaced front
and rear surfaces 52 and 54 of ~enerally square
configuration. ~ plurality of edge faces 56 are provided
which are disposed perpendicular (90) to the rake faces
52, 54. The insert 50 is intended for use in a milling
cutter with a negative axial rake pocket geometry. In
a conventional 90 insert, both the front and rear faces
52j 54 are symmetrical and provide cutting edges for the
lnsert. More specifically, each rake face 52, 54 is
p~ovided with four sharpened edges 58 such that the
insert has a total of eight sharpened edges 58.
In accordance with the subject invention, a standard
90 insert is modified for use as a finishing insert by
providing each cutting edge 58 with an arcuate configuration,
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having a radius which is several times greater than the
width of the planar sur~aces. The arcuate configuration
provides for a drop at the corners "z", to allow ~or a
smooth finishing cut. The drop "Z" is measured as the
spacing between the end point "j" o~ the cutting edge
56 and an imaginary line "k", t:angent to the midpoint
of the cutting edge. In a standard insert having a
width o~ 0.75 of an inch, a drop "g" of .003 to .006
inches is desirable. To provide adequate clearance
along the edge faces 56, at least a portion of the
opposed corner portions 60 of each edge face 56 are
rounded or cleared. Since in this embodiment of the
subject invention there are cutting edges 58 on both
rake surfaces 52, 54, each cornér portion 60 of~ the
edges 56 are symmetrically cleared ~rom the opposed
rake sur~aces to a midline 62. The clearance or slope
"y"' at the corner portions 60 is illustrated in Figure
12. The angle "y~" is measured between the surface "m"
of the edge face 56 and a plane "n" normal to the plane
of rake surfaces 52, 54. The insert 50 is intended to
be used in a milling cutter having a negative rake pocket
geometry. In the illustrated embodiment, a clearance
angle "y"' of 2 i5 provided such that the insert 50
;~ may be~used in a milling cutter having a negative rake
geometry of 4 or greater.
As noted above, rounding and sloping of the corner
portions 60 provides clearance along the edge ~aces 56
o~ the i~sert ~50. The unaltered intermediate portion
of each edge ~ace 56 defines a planar locating land
64 of a tapered, semi-elliptical con~iguration. The
planar lands 64 correspond essentially to the edge
faces of a standard 90 insert. Thus, the planar
lands 64 may be used to facilitate the clamping of the
insert in a milling cutter without altering its pocket
geometry. Further, inasmuch as the insert 50 is
essentially symmetrical and has eight cutting edges 58,
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the insert may be indexed to a position wherein any
of the eight cutting edges 58 may be utilized to
produced a finishing cut.
Accordingly, there is provided a new and improved
finishing insert for use with an indexable cutting tool.
More particularly, a finishing insert is provided
formed from a ~lat wafer of cutting material having
front and rear parallel, spaced planar rake surface
and a plurality of edge faces disposed therebetween.
Each rake face is of generally equilateral polygonal
configuration, with the side edges of at least the
polygonal front surface corresponding to the cutting
edges of the insert. Each cutting edge is arcuate in
configuration having a radius of curvature several
times greater than the front rake surface. The inter-
mediate portion of each edge face is substantially planar
and defines a locating land to facilitate the clamping
of the insert in the pocket of a milling cutter. In
accordance with the subject invention, at least a portion
of the opposed ends of the edge faces are curved and
slope away from the front rake surface in order to
provide clearance aIong the edge faces when the insert
is mounted on a cutting tool at an angle between the
front rake surface and the workpiece.
It is to be understood that changes may be made
in the particular embodiments of the subject invention
in light of the above teachings, but that these will
fall within the full scope and spirit of the subject
invention as defined by the appended claims.
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