Note: Descriptions are shown in the official language in which they were submitted.
lZ11~9i~7
jl ckFround of the hvention
Field of the Invention
The invention relates generally to cu~t~ng tools for machining chip forming
materials. More particularly, the invention concerns cutting inserts incorporating chip
5 ¦ control geometry particularly advantageous at relatively high feed rates.
Description of the Prior Art
Conventional chip control inserts exhibit performance problems when used
at relatively high feed rates, for example, rates exceeding .020 inches per revolution.
These problems are caused by collision of chips produced by the cutting process
colliding with one or more portions of such prior art insert faces resulting in excess
friction and wear which, in turn, leads to premature wear andlor fracture of the cutting
insert material.
Examples of prior art disclosing chip control cuttlng inserts which, at higher
feed rates, present geometries resulting in adverse chip flow impediment are:
U.S. Patent 4,288,179 - Kruger et al
U.S. Patent 3,395,434- Wirfelt
U.S. Patent 3,381,349- Newcomer
U.S. Patent 3,213,716 - Getts
SIJMMARY OF TH~ INVENTION
Accordingly it is an object of this inven~ion to provide a cutting tool for use
at relatively high feed rates and utilizing chip control geometry effective to overcome
25 the above problems with the prior art.
~ lZll~9,'~ ;
The invention is embodied in a preferred form as an indexable cutting insert
for machining chip forming materials, the insert incorporating improved chip control
when used at relatively high feed rates. A land extends around at least one chipbreaking or rake face of the insert adjacent the insert cutting edges and cutting
5 I corners. Connected to the land is a first ramp or chip control surface extending
downwardly and away $rom the peripheral insert land. The first ramp surface is
¦ interrupted at each cutting corner of the insert by a corner control plateau or surface
to prevent damage caused by chip convergence to the trailing side of the active cutting
corner. A second ramp or control surface lies adjacent the first ramp surface and
10 extends downwardly and inwardly from the first ramp, preferably at a smaller
inclination angle than that of the first ramp. A third ramp surface connects an inner
boundary of the corner con~rol surfaces to the second ramp surface at each insert
¦ corner region.
ll The combined ramp and control surfaces effect relatively facile chip flow at
15 ¦I relatively high feed rates, thereby lessening attendant cutting forces and friction.
The combined geome~ries of the various insert face portions also enable
better control of chips at relatively high feeds, due to causing formation of chips having
convex shaped cross sections.
Polygonal inserts designed in accordance with this invention will exhibit
20 prolonged useful life, since their chip handling capability will more effectively combat
~ edge crater and washout.
I
lZ1(19Z~ ~
BRIEF DESCRIPTION OF THE DRI~WING
il These and other objects and features of the invention will become apparent
from a reading of a detailed description of a preferred embodimen~, taken in
conjunction with the drawing in which:
Figs. 1, 27 3 and 4 illustrate cross sectional views of various prior art chip
control configurations used in the chipbreakin~ or rake face of known cutting inserts;
Fig. 5 is a perspective view of an u sert designed in accordance with the
principles of the invention;
I Fig. 6 is a view taken from line 6-6 of Fig. 5;
10 ¦ Fig. 7 is a view taken from line 7-7 of Fig. 5;
Fig. ~ depicts a cross sectional view of a first alternative embodiment;
Fig. 9 depicts a cross sectional view of a second alternative embodiment;
Fig. 10 depicts a top plan view of an alternatively shaped cutting insert
l designed in accordance with the principles of the invention; and
Fig. 11 depicts a view taken from line 11-11 of Fig. 10.
DETAIL~D D~SCRIPllC)N
To better point out the advantages of the invention, reference is first made
to the various chip control configurations of the prior art set forth in Figs. 1-4. Prior
20 ¦ art inserts incorporating the chip control geometries depicted in Figs. 1, 2 and 4 each
¦¦ depend upon shoulders (102 of Fig. 1, 204 vf Fig. 2 ancl 404 o~ Fig. 4) to curl and direc-t
I¦ chips generated by respective cutting edges 100, 200, 400 of Figs. 1, 2 and 4. ~ach
¦! . such insert is adequate at relatively low feed rates, for examplet on the order of about .020
~ inches per revolution, or less. However, such shoulders become detrimental at thick-
lZl(~9Z~ ~
j chip-producing high feed rates. Collision of thicker chips with these shoulders
generates excessive Eriction (therefore heat) and wear. Excessive heat, in turn, causes
chemical reaction betvveen the workpiece chips and insert material (such reaction also
known as edge build-up). Such chip deflection shoulders therefore, under heavy feed
5 rate conditions, soon wear away resulting in diminished insert useful life.
The prior art insert of Fig. 3 has a cutting edge 300 defined by the
intersection of Elank surface 308 and land 302 followed by sloping surface 304 and flat
inner floor surface 306. The insert of Fig. 3 is more efficient at higher feed rates, but
since the insert must be mounted in a negative atti~ude (i.e. with face 306 ~ilted
10 upwards with respect ~o edge 300) to achieve flank clearance between the insert
surface 308 and the workpiece being machined, a fric~ion generated surface is still
presented to disrupt the chip flow.
Ano~her disadvantage to using chip control inserts designed in accordance
with Figs. 2, 3 and 4 at high feed rates arises from use of an internal cup-shaped
15 depression within the insert nose radius. Durin~ the material cutting process, the chip
is forced down into such a depression while simultaneously attempting to curl at 90
degrees to the direction of feed. This compound chip motion subjects the insert's chip
control contour geometry to excessive forces caused by attempting to bend a relath/ely
thick chip in two different directions simultaneously. Such excessive force in the nose
20 radius area tends to wash out, or fracture, the trailing edge of the nose radius at the
insert's active cutting corner, thus shortening useful insert life.
A cutting tool of the invention~ such as the insert set forth in Fi~s. 5-7,
includes rake face contouring which overcomes the aboveJescribed problems wlth prior
lZl(~9'~'7
art inserts used at relatively high feed rates. With reference to Fig. 5-7, cutting insert
10 has, for example, substantially square top and bottom chipbreaking faces joined by
flank or side walls 7, which are subs~antially perpendicular to planes containing the top
l and bottom faces. Four indexable cu~ting edges are defined by the intersection of flank
5 surface 7 with a land area 1 extending about periphery of ~ chipbreaking face. As seen
in Fig. 6, angle a5 between land 1 and flank surface 7 is substantially 90 degrees.
Adjacent an inner boundary of land 1 and extending downwardly therefrom
at an angle al tO the plane of the chipbreaking face is a first ramp or control sur~ace
designated 2a extending between the insert cuttin~ corners, a narrower portion 210 continuing from portion 2a and extending around each radiused CUttillg corner of insert
10.
Adjacent an inner boundary of each rarnp surface 2a and extending down-
wardly therefrom at an angle a2 to the plane of the chipbreaking face is a second ramp
or control surface 3, which terminates at a floor surface 6 substantially parallel to the
15 plane of the chipbreaking face. Insert 10 may be advantageously clamped in cutting
position in a variety of known manners utilizing central aperture 11.
At each insert cutting corner, ramp surface 2a is partially in~errupted by a
recessed plateau or corner control surface 4, which, in this embodiment, is substantially
parallel to tl e plane of the chipbreaking face. An inner boundary of each pedestal
2û suriace 4 is, in turn, connected to control surface 3 via ~hird ramp surfaces 5 which
extend downwardly at angle a3 to the plane of the chipbreaking face.
The width 1~1 of land 1 may lie in the range of about .015 inches to about
.035 inches, with a preferred range of about .018 inches to about .030 inches, thereby
provid ng sufficient corner mass to resist deformation.
~ 121(~9Z~ ~
Surface 2 and surface 2a extend downwardly at angle al having a range of
about 10 degrees to about 20 degrees, with a preferred range of about 15 degrees to
about 20 degrees, in order to provide a smooth, non-resistant chip flow path. A major
portion of chips resulting from relatively large depths of cut then proceeds down ramp
5 1 surface 3 which extends downwardly at an angle a2 having a range of about 5 de~rees to
about 15 degrees, with a preferred range of about 5 degrees to about 10 degrees.
Preferably, angle al is greater than angle a2. With such configuration, surface 3 offers
little or no resistance to chip flow, IJnlike the prior art flat-bottomed insert of Fig. 3
discussed above. Even if crater wear were ~o occur on surface 3, no detrimental results
10 affecting insert life should result, since surface 3 is spaced sufficiently inwardly of the
insert cutting edge
Although the inser~ of Figs. 5-7 must be mounted in a negative rake
attitude, the disclosed configuration allows for facile, smooth chip flow over surfaces 1,
1 2 and 3 with minimal resistance, yet allows chips to curl and break due to their inherent
15 ¦ thickness and dynamics. The arrangement of surfaces 1, 2 and 3 thereby overcomes the
shoulder and floor generated friction problems encountered with prior art designs. This
result is obtained, because the chip, after passing over land 1, confronts positively
oriented (i.e. sloping downwardly from a plane of feed direction) surfaces 2 and 3.
The innermost boundary of surface 2a lies a distance Hl below the plane of
land 1. Distance Hl has a range of from about .004 inches to about .010 inches, with a
preferred range of from about .004 inches to about .008 inches. The innermost
boundary of surface 3 lies a distance H2 below the plane of land 1. Distance H2 has a
range of from about .012 inches to a maximum depth limited principally by the required
121(~9z7
diarmeter of mounting aperturç 11 with a preferred range of from about .012 inches to
about .020 inches.
In order to overcorne the above discussed problem of chip convergence and
resultant high pressure in the vicinity of the cutting corner nose radius, pedestal or
5 I csrner control surface 4 with connecting ramp surface 5 is placed inwardly of each
j insert cutting corner. Surface 4 lies at a depth H3 below the plane of land 1. Depth H3
preferably is on the order of one-half the depth Hl. Surface 5 extends downwardly
from an inner boundary of surface 4 at an angle a3 having a useable range of from about
Il 10 degrees to about 25 degrees, with a preferred range of from about 15 degrees to
10 I about 20 de~rees~ With this configuration, stress is reduced in the area of the cutting
¦ corner. Another benefit of a corner control surface or pedestal is the ability to effect
good chip control at relatively shallow depths of cut- Cantrol surface 4 deflects and
breal<s chips when the depth of cut is mostly directed to surface 4. Beyond this depth
l of cut, chips will flow freely due to the configuration of surface 2 and 3. Such free
15 flow, along with the influence of corner control surface 4, creates a barrel-shaped or
convex, somewhat embrittled chip conducive to easier breaking. Dimension L2 (Fig. 5)
is govèrned by the radius of curvature of the cut~ing corner, L2 Iying in the preferred
range of about one to about one and one-half times such radius.
l Fig. 8 depicts an alternative configuration for a land surface 1' which
20 ll¦ intersects flànk surface 7 at an obtuse angle a5' (i.e. land 1' slopes downwardly toward
¦¦ the cutting edge at an angle a4). This alternative embodiment is beneficial in those
applications requiring greater edge strength, such as where hardened materials are
being machined. Angle a5 may lie in the range of from about 90 degrees to about 120
degrees, with a preferred range of fronn about 90 degrees to about lûO degrees.
Il l'Z3L6~9'~7
Fig. 9 sets forth yet another alternative to the embodiment of Figs. 5-7,
wherein each corner pedestal or control surface 4' extends downwardly at angle a6 to
the plane of the chipbreaking face. Angie a6 is selected to be less than angle al of first
¦ ramp surface 2 (Fig. 7). With a downward slope, corner control surface 4' may offer
5 ¦ less resistance to free flowing chips in the insert cutting corner region.
A triangular insert designed in accordance with the principles of the
invention is set forth in Figs. 10 and 11. In a prototype triangular insert tes~ed under
relatively heavy feed rates in excess of .020 inches per revolution, insert 20 equipped
l with conventional mounting aperture 29 includes land 23, preferably about .018 inches
10 1, wide, intersecting flank surfaces 22 at an angle of about 90 degrees to thereby define
cutting edge 21. First ramp surface 24A, 24B extends downwardly from an inner
boundary of land 23 at an angle of about 15 degrees to an ulner boundary located about
.006 inches below the plane of land 23. Second ramp surface 27 extends downwardly
l from the inner boundary of surface 24A at an angle of about 7 degrees to a floor
15 1 surface 28 located at a depth of about .016 inches below the plane of land 23. In each
i corner, pedestal surface 25 interrupts surface 24a at a depth of about .003 inches below
¦I the plane of land 23. Third ramp surface 26 extends downwardly at an angle of about 20
¦ degrees to connect the inner boundary of pedestal 25 to ramp surface 27.
l The invention has been described with reference to preferred embodiments
20 ¦ solely for the sake of example and without exclusion of those alternatives which will
become apparent to those skilled in the art. For example, the various control and rarnp
¦I surfaces described could be arcuate rather than planar, so long as the intersections of
the various surfaces are tangentially joined in a manner such that will eliminate chip
_9_
lZl(~9Z7
impinging barriers. The invention is to be limited solely by the scope and spirit of l:he
; pp nded clalms.
Il
~ .
-10-
