Cutters – for shaping – Comprising tool of specific chemical composition
Reexamination Certificate
2000-09-29
2004-03-30
Tsai, Henry W. H. (Department: 2183)
Cutters, for shaping
Comprising tool of specific chemical composition
C407S120000
Reexamination Certificate
active
06712564
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not Applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to tools and methods of producing and treating them. More particularly, the present invention is directed to tools that are treated by modifying at least a region on at least one surface of the tool by texturing the region in order to, for example, improve the retention capability of the tool in a tool holder. The tool may be, for example, a cutting tool insert or a chip breaker. The present invention also relates to methods of producing or treating a tool. Thus, the methods of the present invention may be applied in the production or treatment of cutting tools, and a particular application of the present methods is in the production of cutting tool inserts and/or chip breakers used in the machining of metals and other materials.
2. Description of the Invention Background
Castings, forgings, or other metal-containing preforms often are subjected to machining so as to convert the preform into a final product of the desired shape, size and/or finish. Machining is generally defined as the process of removing unwanted material from a workpiece. In a common form of a machining process known as chip machining, a surface of a cutting tool is brought into forceful contact with a workpiece and separates material from the workpiece in the form of small chips. The cutting tool may include a tool holder having a shank that can be mounted on a machine tool. A cutting tool insert formed of a high strength, high hardness material is removably secured on the tool holder, and the cutting tool insert can be replaced once worn. During the machining process, it is important that the cutting tool insert be securely seated and retained in a fixed position within the tool holder. Even slight movement of the cutting tool insert during the machining process can result in failure of the insert or production of material that is outside the desired tolerance specifications. Most manufactured products contain one or more components manufactured by machining, and often the machining step or steps produce the components to very precise tolerances. Machining, while one of the most basic and important processes used in manufacturing metal products, also is one of the more expensive. Thus, even modest improvements in the machining process may yield substantial cost savings.
There are a number of basic chip machining processes, including turning, boring, shaping, milling, drilling, sawing, and broaching. In one such process, turning, external surfaces of revolution may be generated by the action of a cutting tool insert on a rotating workpiece. Typically, the workpiece is mounted and rotated on a lathe. In turning, as in each of the other chip machining processes, the design of the cutting tool is critical to the efficiency by which material can be removed from the workpiece. Thus, substantial sums are spent each year to research and develop improved cutting tools for machining.
Cutting tool materials predominantly in use for production machining processes include high speed steels, carbides, cemented carbides (such as, for example, cemented tungsten carbide), cermets (carbide/ceramic), CBN (cubic boron nitride), PCD (polycrystalline diamond), and ceramics. Ceramics are preferred materials that are used commonly in cutting tool inserts used in turning operations. They are also one of the most recently developed classes of materials. Ceramics are particularly advantageous materials because they generally have high hardness, are relatively resistant to oxidation and, therefore, exhibit low tool wear at high cutting temperatures. The faster the cutting speeds, the higher the cutting temperature. Thus, the hardness, oxidation and wear resistance properties of ceramics allow ceramic cutting tools to be used with fast cutting speeds while maintaining long tool life, thereby improving the efficiency of the machining process.
Current ceramic materials used to produce cutting tool inserts are commonly based on either alumina (Al
2
O
3
) or silicon nitride (Si
3
N
4
). The production of ceramic articles generally, and ceramic cutting tool inserts in particular, involves the consolidation and sintering of powdered material. There are two basic methods of producing ceramic articles, cold pressing and hot pressing. In cold pressing, the powdered material is first consolidated, or pressed, into a green (unsintered) body. The green body is then sintered by heating the body to a high temperature below the melting point of the powdered material. The body is maintained at the high temperature for a time sufficient to fuse the powder particles and sufficiently densify the green body. In hot pressing, the powdered material is heated in a die while a high uniaxial pressure is applied to the body. Hot pressed ceramic usually has a finer grain size and higher density than cold pressed ceramic, thereby resulting in superior hardness and longer tool life.
Although ceramic cutting tool inserts made from hot pressed ceramic have properties superior to those made from cold pressed ceramic, cold pressed ceramic inserts are commonly used. One reason for the continued use of cold pressed ceramic cutting tool inserts is that forming ceramic by cold pressing arguably provides a greater degree of flexibility in designing the exterior contour of the inserts.
Some means is necessary to retain the cutting tool insert on the tool holder. Historically, cutting tool inserts formed by hot or cold pressing were designed with a bore therethrough, as shown in FIG.
4
(
a
). In this design, the cutting tool insert
130
is secured in the pocket
126
of the tool holder
120
by inserting and threadedly securing a locking pin
150
through the bore
132
and into a bore
124
in the tool holder
120
. Because a large volume of material is removed from a central region of the cutting tool insert
130
to provide bore
132
, the strength of the insert may be reduced.
In an alternative design, the cutting tool insert is retained on the tool holder by a clamp. An example of this design is shown in FIG.
4
(
b
). A generally L-shaped clamp
240
secures the cutting tool insert
230
to the tool holder
120
. One leg
246
of the L-shaped clamp
240
is secured within bore
122
of the tool holder
120
, while the other leg
248
is disposed against an exposed flat face
232
of the cutting tool insert
230
. Cutting tool inserts composed of either hot or cold pressed ceramic may be used in this cutting tool design. Because the cutting tool insert
230
of FIG.
4
(
b
) lacks a central bore, the strength of the insert is not compromised. On the other hand, the insert
230
of the design of FIG.
4
(
b
) is not, in general, secured to its tool holder as strongly as the insert
130
of FIG.
4
(
a
).
Another prior art cutting tool design is shown in FIG.
4
(
c
). Here, the cutting tool insert
330
includes a depression
332
in at least one surface
334
. One leg
346
of a generally L-shaped clamp
340
is secured within bore
122
of the tool holder
120
while the other clamp leg
348
is seated in the depression
332
. As will be apparent to those skilled in the art, there are many different conventional designs of L-shaped clamp
340
. This arrangement more positively secures the insert
330
in the pocket
126
of the tool holder
120
relative to the arrangement of FIG.
4
(
b
). Hot pressing cannot be economically applied readily to produce cutting tool inserts having a depression as shown in FIG.
4
(
c
).
Accordingly, there exists a need for an improved arrangement for securely retaining cutting tool inserts on tool holders. Preferably, the improved retention arrangement may be used with both hot pressed and cold pressed inserts and will not adversely affect the strength properties of the inserts.
SUMMARY OF THE INVENTION
The present invention provides a tool and a method of treating a tool for material removal. The tool is produce
Greenleaf James M.
Howles Stanley B.
Hughes Donald R.
Greenleaf Technology Corporation
Kirkpatrick & Lockhart LLP
Tsai Henry W. H.
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