Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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-l- 6~P-2085
IMPROVED INSERT AR~ANGEMENT FQR A MILLING TOOL
This invention relates to multiple indexable insert metal
working tools, and more particularly to rotary and milling kinds of
tools where the cir~w~fcr^~ of the tool is the limi.ting ~actor to
S the number of indexable inserts that can be effectively employed.
Background of the Invention
A milling cutter may take the form oE a flat faced disc or
body member which has a coaxial drive means on one side, and the other
side, ~ace, includes a numbe~ of indexable cut-ters and corresponding
lQ grooves, pockets or slots. The cutter inserts are arranged so -that
when the face of the tool is brought up against a workpiece, for
example a flat surface oE a workpiece, the inserts cut out or remove
an annular groovel a saucer depressiQn ancl the like large area cuts.
The area of the face or the periphery area of the disc which is
adapted to contain the cutter insert is the limiting Eact to the
number of inserts that can gainfully be employed co~mensurate with
the design and strength of the disc member. Obviously, existing disc
members simply limit the num~er of inser-t cutters by their original
design, since ordinarily there are no adjustment features. In the
usual design, a milling cutter face includes a plurality of generally
rectangular sockets or pockets therein. A single generally rectangular
cutte~ inse~t is positioned in each pocket and a wedge block is used
in the pocket tQ firmly wedge the in$ert in position. ~ further
hindrance to the desired use of a gr~a~r number of inserts is the
increased tool chatter which occurs when a plurality of inserts engage
the ~Yorkp~ece with the same frequency and amplitude. An increase in
the numbe~ ~f cutter inse~ts, commensurate with diminished chatter
would represent a more desirable milling kind of tool. ~
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Summary of the Invention
I~ has now been discovered that the number of
inserts in a disc cutter may nearly be doubled by a more
effective use of wedges and inserts in slightly modiEied
poc~ets.
In a given plunge milling cutter having one or
more circular rows of pockets to contain insert and
wedges, the pockets are made slightly wider, if neces-
sary~ and in each pocket there is positioned a pair of
inserts with an intermediate wedge. The insert position-
ing geometry is modified to minimize chatter.
Brief Description of the Drawings
This invention will be better understood when
taken in connection with the following description and
the drawings in which: FIG. 1 is a plan view of one
embodiment of this invention AS a plunge mill cutter;
and
FIG. 2 is a partial and side elevational view
of a double insert arrangement as used in FIG. 1.
Description of Preferred Embodiment
Referring now to FIG. 1 there is illustrated a
plunge mill cutter 10 comprising a heavy wheel or disc
member 11 and a plurality of repeating sets of inserts 12
arranged on the work- ing face thereof. The reverse face
of the cutter 10 contains the usual drive means Eor ro-
tating the disc member 11 about its concentric axis.
Disc member 11 includes a series of generally
rectangular slots 13 which progress from the periphery of
the disc towards the center 14 but purposefully not radi-
ally. The center line of each groove with the exception
of groove 15 is displaced from or offset from a center
line of the circle in the direction of rotation a suit-
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able amount to provide a proper negative radial rake.
Also, some of the peripheral angular distances between
groove centerlines at the outer periphery of the disc
member are equal and some are unequal. The slots 13 have
been slightly enlarged in width, for example about 25~,
to accommodate the insert combination as illustrated.
Each repeating insert set 12 comprises two
inserts 16 and 17, which may be the usual cobalt cemented
tungsten carbide inserts, in a generally rectangular or
diamond shape. These inserts 16 and 17 are positioned
one against the leading wall of the groove (in the direc-
tion of rotation of the disc, counterclockwise in the
case of FIG. 1) and the other one agains the trailing
wall of the groove. Each insert has its exposed cutting
p (~ e/
edge-ssr~e~ to the cutting edge of the other insert and
facing in the same direction. A typical wedge block 18
is wedged between the inserts 16 and 17 and retained
within the groove by such means as a machine screw 19
passing through the wedge block 18 and into the disc mem-
ber 11. Various combinations of tapering groove ~alls
and tapered wedge block surfaces are known to be employed
for insert retention purposes. ~n important point is
that formerly only a single insert would be used for each
groove. In this particular tool not only are two such
inserts employed in front and back relationship as a set
of inserts, but also multiple sets or pairs of sets are
employed ~ in the groove. The unique relationship
of these set inserts which permits their effective cut-
ting action in sets, is more clearly shown in ~IG. 2.
Referring now to FIG. 2, the elevational view
of an insert set 12 shows a leading insert 16 and a
trailing insert 17 residing within a groove 13. Wedge
block 18, with appropriate tapering front and back sur-
faces, and screw means 19, is positioned between the
inserts 16 and 17 to retain them in the groove in the
usual manner.
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Referring again to FIG. 1, in order -to more
effectively utilize the closely spaced inserts in each
set 12, they are arranged in pairs, as illustrated in
FIG. 1, as a pair of sets 20. In one instance, the
insert se-t 21 comprises a pair of inserts 22 and 23,
-the inserts being 3 times the length of a typical
insert 16 or having a cutting path equal in width
to the to-tal cutting path of the tool.
Each insert 16 and 17 in each set 12 is
laterally (generally radially) offset with respect
to each other to provide some overlap in the cutting
path. The overlap is predetermined among all insert
sets 12 so that a clean cut is ob-tained and
cutting forces axe more equalized amongst the inser-ts.
Also, the insert set 12 in each pair of se-ts 12
is laterally separated from an adjacent set 12 by
means of spacer members 21. Spacer members 24 may
be dowel like pins adjacent an insert 16 and
17 in each adjacent pair of sets 12 and fixes
the overlap position of all insert sets.
Disc chatter is dampened in this invention
by a combination of Eeatures. For example r the sets
12 of inserts in a given groove are mounted at uneven
heights above the face of the disc member 12. For
example, referring to FIG. 1 the pair 20 of insert sets
12 closest to the 6 o'clock position of the disc 11
are referred to as station 1, STA 1 reading counter
clockwise to STA 7. The insert sets for STA 1 and 7
project above the face of disc member 11 a given
distance ~hile STA 2 and 6 project further, and STA 3
and 5 project still further. STA 4 projects the
furthest and is effectively utilized to wipe out any
overlap marks.
A geometry change for leading and trailing
inserts 16 and 17 using the same wedge has been employed
for further vibration damping purposes. This is more
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clearly shown in FIG. 2. In FIG. 2 the leading insert
16 has its axial centerline at a positive rake ~osition
while the trailing insert 17 has its axial centerline at
a negative rake. T.1hen viewed from the disc center of
FIG. 1, the radial rake is more negative for the ieading
insert.
The forward rate of advance of the milling
cutting tool is usually constant bu~ the improved
geometrics of this invention lead to more effective metal
removal and provide a non - ~ ~}~, chatter minimizing,
tool.
This invention can be applied to various metal
working tools where but one pocket is employed in a given
tool holder. The invention, however, is more applicable
to rotary tools having a plurality of pockets therein,
and principally to a milling tool.
Although the present invention has been
described with reference to the foregoing specification,
many modifications, combinations and variations of the
invention will be apparent to those s~illed in the art in
light of the above teachings. It is therefore understood
that changes may be made to the particular embodiments of
the invention which are within the full scope of the
invention as defined by the following claims.
