BACKGROUND OF THE INVENTION
This invention relates to a method of producing a tool
insert including at least one ultra-hard abrasive body at an edge thereof (see for
example
EP-A-0 744 242
).
Various types of tool inserts and methods of making such
tool inserts are known.
South African Patent No. 84/6619
teaches providing a tungsten carbide substrate with a single recess therein,
brazing an abrasive compact, for example a diamond abrasive compact, into the recess,
and cutting the product to form a single tipped insert.
European Patent No. 278703
teaches providing a tungsten carbide substrate with a plurality of recesses
therein, filling each recess with a layer of abrasive particles, e.g. diamond or
cubic boron nitride (CBN) in an organic binder, subjecting the assembly to high
temperature/high pressure to bond the abrasive particles together and to the carbide
support, and cutting the product to form multiple tipped inserts.
United States Patent No. 5,676,496
teaches a method of producing a multiple tipped insert which is similar
to the method of
EP 278703
, except that the tungsten carbide substrate includes holes which pass
right through the substrate, rather than recesses in the substrate.
SUMMARY OF THE INVENTION
According to the invention, there is provided a method
of producing tool insert which includes the steps of:
- (a) providing a substrate having a plurality of recesses therein;
- (b) placing in each recess an ultra-hard abrasive body of substantially the
same size and shape as the recess;
- (c) brazing the bodies to the substrate; and
- (d) cutting the substrate through the recesses containing the bodies to produce
at least one tool insert comprising a section of the substrate to which is bonded
at least one ultra-hard abrasive body at an edge thereof.
In step (a) the substrate may, for example, be steel but
is preferably a cemented carbide substrate. The recesses may be pre-sintered, i.e.
formed in the substrate before sintering, or may be die sunk or ground into the
substrate.
The recesses may be of any suitable shape and size, and
of any suitable number.
Generally, the recesses are arranged in an ordered pattern
to facilitate the cutting step, step (d).
For example, the recesses may be arranged in spaced rows
and columns, preferably equidistantly spaced, and may, for example, be circular
in shape. Other recess shapes are possible.
The area of the substrate adjacent each recess may be shaped
to provide any tool insert cut therefrom with a positive or a negative chip breaker.
This may be achieved by providing a region adjacent at least some of the recesses
higher or lower than the top exposed surfaces of the abrasive bodies located in
those recesses.
The ultra-hard abrasive body is preferably a polycrystalline
diamond body, also known as PCD, or a polycrystalline cubic boron nitride body,
also known as PCBN or CVD diamond. CVD diamond is diamond produced by chemical vapour
deposition.
The body must be of substantially the same size and shape
as the recess in which it is to be placed, preferably so as to be a snug fit therein.
The top surface of the body may be in the same plane as the surface of the substrate
in which the recess is formed or in a different plane where a chip breaker is present,
as described above.
The body may be unbacked or backed with a suitable backing
layer such as a cemented carbide, e.g. cemented tungsten carbide.
Each recess will generally have a base and side walls.
Thus, in step (c), a layer of a suitable braze will typically be located between
the base of the recess and a surface of the body and the temperature raised to cause
the braze to bond the surface and base together.
A suitable braze for polycrystalline diamond or CVD diamond
bodies is a copper/silver alloy braze and for polycrystalline cubic boron nitride
bodies a high temperature active braze containing a reactive element such as titanium.
In step (c), the bodies will all preferably be simultaneously
brazed into the recesses, e.g. by vacuum brazing, or brazing in a reduced or air
controlled atmosphere.
In step (d), the substrate is cut through the recesses
containing the bodies, for example by EDM cutting. The cutting may be perpendicular
to the substrate surface in which the recesses are formed or at any other angle
to this surface.
The result is at least one and generally a plurality of
tool inserts each comprising a section of the substrate to which is bonded at least
one ultra-hard abrasive body at an edge thereof, and more preferably two or more
ultra-hard abrasive bodies at edges thereof. The ultra-hard abrasive bodies will
provide cutting edges for the tool insert. Different ultra-hard abrasives may be
used for a single insert. This allows for an insert having different ultra-hard
abrasive bodies at each or some of the edges to be produced.
After step (d), the tool inserts, if required, may be processed
to ensure that the ultra-hard abrasive bodies are flush with a surface of the substrate.
The tool inserts produced by the method of the invention
may be used in tools for cutting, machining, drilling or abrading of workpieces
and may also be used as a wear part.
BRIEF DESCRIPTION OF THE DRAWINGS
-
Figure 1
- is a sectioned side view of a substrate including a plurality of recesses, each
recess containing an ultra-hard abrasive body;
-
Figure 2
- is a plan view of the substrate of Figure 1;
-
Figure 3
- is a plan view of a further embodiment of a substrate including a plurality
of recesses, each recess containing an ultra-hard abrasive body;
-
Figure 4
- is a section through an insert cut from a substrate of Figure 3;
-
Figure 5
- is a plan view of a further embodiment of a substrate including a plurality
of recesses, each recess containing an ultra-hard abrasive body;
-
Figure 6
- is a section through an insert cut from a substrate of Figure 5;
-
Figure 7
- is a plan view of a further embodiment of a substrate including a plurality
of recesses, each recess containing an ultra-hard abrasive body;
-
Figure 8
- is a section through one form of an insert cut from a substrate of Figure 7;
and
-
Figure 9
- is a section through another form of an insert cut from a substrate of Figure
8.
DESCRIPTION OF EMBODIMENTS
The crux of the invention is a method of producing a tool
insert or, more generally, a plurality of similar tool inserts in a single brazing
operation. The method includes the steps of providing a substrate, the substrate
having a plurality of recesses therein; placing in each recess an ultra-hard abrasive
body, e.g. PCD, PCBN or CVD diamond of substantially the same size and shape as
the recess; brazing the bodies to the substrate; and cutting the substrate through
the recesses containing the bodies to produce at least one tool insert, each tool
insert comprising a section of the substrate to which is bonded at least one ultra-hard
abrasive body at an edge thereof.
The substrate is preferably made of cemented carbide such
as cemented tungsten carbide, cemented tantalum carbide or cemented molybdenum carbide.
Embodiments of the invention will now be described with
reference to the accompanying drawings.
Referring first to Figures 1 and 2, there is shown a cemented
tungsten carbide substrate 10 having a plurality of pre-sintered recesses 12 formed
therein.
There is located in each recess 12 a polycrystalline ultra-hard
abrasive body 14 consisting of an ultra-hard abrasive layer 16 and a backing layer
18 of cemented tungsten carbide.
Located between the base 12a of each recess 12 and the
base 18a of each body 14 is a layer 20 of a braze.
Once the bodies 14 are all located in the recesses 12 in
the substrate 10, the whole assembly is brazed, i.e. heated, in an air controlled
atmosphere or vacuum depending on the braze alloy used to bond the bodies 14 to
the substrate 10.
Thereafter, the substrate 10 is cut through the recesses
12 containing the bodies 14 to produce one, and preferably a plurality of tool inserts.
For example, referring to Figure 2, the substrate 10 may be cut along the lines
A, B, C and D to produce a tool insert 22 consisting of a section 24 of the substrate
10 to which are bonded four abrasive bodies 26 at each of the four corners of the
section 24.
It can be seen that if the lines A, B, C, D are extended,
and if similar cutting lines are made through the remainder of the substrate 10
and bodies 14, a plurality of substantially similar tool inserts 22 can be produced.
After the tool insert 22 has been cut from the substrate
10, the abrasive bodies 26 may be lapped so that they have outer surfaces 26a flush
with the outer surfaces 24a of section 24 of the substrate 10. Each abrasive body
26 provides a cutting edge and cutting point for the tool insert 22,
The tool insert 22 may be used as an insert for a conventional
cutting tool.
A second embodiment of the invention is illustrated by
Figures 3 and 4. Referring to these Figures, a cemented carbide substrate 30 has
a plurality of recesses 32 formed therein and abrasive bodies 34 placed in each
recess and brazed to the substrate in the same manner as described above for the
embodiment of Figures 1 and 2. Between each four adjacent recesses, e.g. those indicated
as A, B, C and D, is a surface 36 of the substrate which is raised relative to the
top exposed surface of the bodies. The surface 36 is bounded by sloping surfaces
38.
A tool insert may be produced from the substrate 30 by
cutting along the dotted lines 40. The resulting tool insert 42 is shown in section
by Figure 4, the section being along the line 4-4 of Figure 3. The tool insert 42
comprises a cemented carbide section 44 having an abrasive body 46 located in each
corner thereof. Each abrasive body 46 comprises a polycrystalline diamond or CBN
layer 48 bonded to a cemented carbide support 50.
The section 44 has a portion defined by upper flat surface
52 and sloping surfaces 54 which is raised relative to the top exposed surface 56
of layer 48. This portion acts as a positive chip breaker for the tool insert, in
use.
A further embodiment is illustrated by Figures 5 and 6.
Referring to these Figures, a cemented carbide substrate 60 is provided. Abrasive
bodies 62 are located in recesses 64 in the substrate and brazed to the substrate
in the same manner described above in relation to the embodiment of Figures 1 and
2.
In this embodiment, each recess 60 is surrounded by a shallow
groove or depression 66.
One or more tool inserts may be produced from the substrate
60 by cutting along the dotted lines 68. A section of a tool insert 70 thus produced
is shown by Figure 6, the section being along line 6-6 of Figure 5.
Tool insert 70 comprises a cemented carbide section 72
having an abrasive body 74 located in each corner thereof. Each abrasive body 74
comprises a polycrystalline diamond or CBN layer 76 bonded to a cemented carbide
support 78. A depression or groove 80 lies adjacent the top exposed surface 82 of
each layer 76. This depression or groove functions as a negative chip breaker.
A further embodiment is illustrated by Figures 7 and 8.
Referring to these Figures, a cemented carbide substrate 90 has a plurality of shaped
recesses 92 formed therein and similarly shaped abrasive bodies 94 placed in each
recess and brazed to the substrate in the same manner as described above for the
embodiment of Figure 1 and 2. Between each four adjacent recesses, e.g. those indicated
as E,F,G and H is a surface 96 of the substrate which is bounded by a shallow groove
or depression 98. The recesses 92 are shaped such that the corners of the groove
or depression 98a are each partially surrounded by the recess 92.
A tool insert may be produced from the substrate 90 by
cutting along the dotted lines 100. The resulting tool insert 102 is shown in section
by Figure 8, the section being along the lines 8-8 of Figure 7. The tool insert
102 comprises a cemented carbide section 104 having an abrasive body 106 located
in each corner thereof. Each abrasive body 106 comprises a polycrystalline diamond
or CBN layer 108 bonded to a cemented carbide support 110. A groove or depression
114 lies adjacent the top exposed surface 116 of each layer 108. This groove or
depression functions as a negative chip breaker.
Figure 9 illustrates a section of an alternative embodiment
of a tool insert which can be cut from the substrate of Figure 7. For this embodiment,
the surface 96 is raised relative to the top surface of the abrasive bodies 94 and
the groove or depression 98 is replaced by sloping surfaces.
A tool insert may be produced from the substrate 90 by
cutting along the dotted lines 100. The resulting tool insert 120 is shown in section
by Figure 9, the section being along the lines 8-8 of Figure 7. The tool insert
120 comprises a cemented carbide section 122 having an abrasive body 124 located
in each corner thereof. Each abrasive body 124 comprises a polycrystalline diamond
or CBN layer 126 bonded to a cemented carbide support 128. The section 122 has a
portion defined by upper flat surface 130 and sloping surface 132 which is raised
relative to the top exposed surface 134 of layer 126. This acts as a positive chip
breaker for the tool insert, in use.
It will be noted in the embodiments of Figures 3 to 9 that
the cemented carbide substrates are shown as being cut at an angle other than 90°
to the top and bottom surfaces of the substrates. Cutting may be effected at other
angles to these surfaces.
An advantage of the invention is that a plurality of tool
inserts may be prepared simultaneously in a simple and economical manner.
