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Jan. 14, 1947. '
Filed‘ Sept. 11, 1944
Char/e5 6? 6300416
E) Mm‘
24W: (ed-11
Patented Jan. 14, 1947
ED sr
Charles E‘. Kraus, Rochester, N. Y.
Application September 11, 1944, Serial No. 553,485
3 Claims. ~(Cl. 29-95)
This invention relates to the tips of metal
cutting tools, particularly those composed of ma
terial having the property known as red hard
ness, that is to say, the ability to permanently
retain a hardness ample for metal cutting even
after heating of the material above bright red
nessor substantially in excess of 1200‘degrees
There are two groups of metal cutting mate’
sectional view illustrating the action of the tip
in removing metal from a workpiece.
Fig. 3 shows a temperature gradient curve.
The cutting tool or tooth illustrated in the
drawing comprises a body or shank 5 of any con
ventional shape usually composed of steel or cast
Mounted on one side of the shank and'
extending to the end thereof is a tip 6 which, in
the case of the tooth shown, provides a gener
rials of this character now available. One of 10 ally ?at cutting face ‘I and is sharpened on the
these is sintered carbide such as the material
end and side to provide side and end cutting
sold under the trade names of Carboloy,
edges 8 and 9. The tip, which may be'of sub
Firthite, Kennametal, and Rexite and compris
stantially uniform thickness, is shown seated in
ing particles of the carbide of one or more metals
such as tungsten, tantalum, and titanium bonded
together by a metal, such as cobalt, having a very
a sguared recess formed in the shank 5 and is
?rmly bonded at II to the seat by a suitable
metallic bonding material which is capable of
high melting point. The other group of cutting
withstanding the maximum temperature at
material includes those sold under the trade
names of Stellite, Rexaloy, Tantung, or Crobalt
tained at the bond in the service use of the tool.
Silver solder is an example of a suitable bonding
and comprising cast alloys of nonferrous metals 20 metal.
including tungsten, cobalt, chromium, tantalum,
and others. The carbide materials possess
greater red hardness than the cast materials,
In metal cutting with such a tooth, a layer ll]
of metal is removed from the work by the cut
ting edge 9 and the face ‘I, the chips ?owing along
that is to saypat any given operating tempera
the face‘ ‘I so that the highest temperature is at
ture, tungsten carbide is harder than Stellite‘ 25 tained on this face adjacent the cutting edge.
and, for this reason, is preferred as a cutting
This temperature decreases progressively down
material. Such carbides are, however, more
through the tip and into the supporting matecli?cult to sharpen by grinding because their
rial or shank 5. The tip is made of a thickness
hardness approaches that of grinding abrasives.
which will insure an overall temperature drop
' Because of this, higher temperatures are pro 30 through the tip sufficient to prevent deteriora
duced frictionally during the grinding of car
tion of the bond H or the supporting material ‘5
bide tips, frequently resulting in ‘cracking and
under the severest conditions of use.
checking. This dii?culty is not nearly as serious
In accordance with the present invention, the
in the case of the cast cutting materials owing to
tip is divided along a line generally parallel to
their substantially lesser hardness.
‘ I take advantage of these inherent character-'
istics of the two groups of materials to produce
a composite cutting tip which utilizes all of the
advantages of the sinteredcarblde as a cutting
material while greatly facilitating grinding.
A‘more detailed object ‘is to provide a com
posite cutting tip comprising a relatively thin
35 the cutting face ‘I and comprises a relatively
thin layer 12 of a sintered carbide forming the
cutting face ‘I and the cutting edges 8 and 9 and
a thicker under layer E3 of a material also pos
sessing red hardness and constituting a support
40 for the carbide layer It. The supporting mate
rial is selected from the group of the cast non
ferrous alloys mentioned above so as to facilitate
layer of sintered carbide as the cutting material
grinding of the tip. In the tool shown, each
and a substantially thicker layer composed of
layer is of uniform thickness, and the two are
material of inherent red hardness but of the 45 ?rmly bonded‘ together at It as by high tem
cast type mentioned above and utilized, not as a
cutting .material, but as a support or carrier of
perature brazing with copper or the like as is
common in practice.
the carbide layer.
In order to obtain best grinding characteristics,
Other‘ objects and advantages of the inven
it is desirable to make the carbide layer as thin
tion will become apparent from the following 50 as possible. On the other hand, the carbide must
detailed description taken in connection with
be thick enough to prevent the attainment in
the accompanying drawing, in which
severest service use of a detrimentaltemperature
Figure 1 is a perspective view of a milling cut
at the bond It or in the cast metal of the support
ter tooth embodying the present invention.
ing layer l3. Fig. 3 shows diagrammatically the
Fig. 2 is an enlarged fragmentary longitudinal 65 temperature gradient curve for metallic material
such as tungsten carbide, a'being the maximum
safe operating temperature for metal cutting,
‘ points 12 and 0 being respectively the safe maxi
mum temperatures for the Stellite used in the
metallic carbides such as Carboloy, Firthite, Ken
nametal, Rexlte, etc. and cast nonferrous metal
alloys such as Stellite, Rexalloy, Tantung, Cro
balt, etc., which materials acquire their hardness
without heat treatment and retain ample hard
layer l3 and the steel used in the shank 5. Ac
cordingly, the minimum thickness of the carbide
ness for metal cutting at temperatures in excess
layer I2 is represented by the line db and, simi
of 1500 degrees Fahrenheit. High speed steel may
larly, the Stellite layer l3 should be made ofv a
be annealed by heat'treatment and,_ therefore,
does possess inherent hardness.
thickness at least equal to the length of the line
I claim as my invention:
ec. Satisfactory results have been obtained with 10
1. A cutting tool comprising a supporting body
the layer 13 about two ‘and one-half times as
of ferrous material forming a seat for a tip, and
thick as the layer II. The bonds II and M
a tip carried by said body on said seat and de
should. of course, be capable of withstanding the
temperatures developed at the junctions of the
?ning a cutting face, said tip comprising a rela
tively thin outer layer of a sintered metallic car
layers l2 and I3, and I3 and 5. the examples of
bide forming said cutting face and an under layer
bonding materials mentioned above being satis
of a castvnonferrous alloy bonded on one side
factory for this purpose.
to said carbide layer and on the other side to said
It will be apparent from the foregoing that the
overall thickness of the tip material is deter
mined by the temperature that is permissible at
the bond I I so that substantially the same thick
ness is required whether the tip is carbide mate
rial alone or a composite tip as described above.
Owing, however, to the thinness of the carbide
layer l2 and the fact that the layer_l3 may be 25
seat, the materials of both layers possessing in
herent red hardness and the red hardness of said
carbide layer being greater than that of the sec
ond layer.
2. A tip for mounting on a tooth of a cutting
tool comprising a relatively thin layer of a sin
tered carbide of uniform thickness and a sub
ground much more readily, sharpening of the
tool is greatly facilitated. There is less of the
harder carbide material to remove, and, there
stantially thicker layer of uniform thickness of
reason, more stock may be removed during each
3. A tip for mounting on the tooth of a cutting
tool comprising a relatively thin layer of a sin
tered carbide and a substantially thicker layer of
a cast nonferrous alloy bonded to said carbide
a cast nonferrous alloy bonded to said carbide
layer, the materials of both layers possessing in
fore, less frictional heat is developed, with a
herent red hardness, and the red hardness of said
consequent reduction in the danger of damaging 30 carbide layer being greater than that of said
second layer.
the tip by cracking or checking. For the same
pass with the grinding wheel thereby speeding
up the sharpening process. Furthermore, wear
ing o? of the grinding wheel is less rapid so that
layer, the materials of both layers possessing in
herent red hardness, and the red hardness of said
carbide layer being greater than that of said
tainmentyof precision in the sharpening of mul
second layer.
tiple tooth cutters is thereby facilitated.
As used in the appended claims, the term 40
"inherent red hardness” contemplates sintered
the wheel will retain its size during the grind
ing of a larger number of cutter teeth. The at
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