Rotary tool for machining workpieces

Details Rotary tool for machining workpieces Rotary tool for machining workpieces

2000-04-06

2001-07-31

Wilson, John J. (Department: 3732)

Dentistry

Apparatus

Tool bit

C433S166000

Reexamination Certificate

active

06267595

ABSTRACT:

FIELD OF THE INVENTION
The instant invention relates to a rotary tool for machining workpieces, especially for material detaching work in dentistry, comprising a machining portion having an outer circumferential surface coated with a nickel layer in which diamond particles are embedded.
BACKGROUND OF THE INVENTION
Grinders and similar abravise tools, milling cutters and the like may be named as examples of rotary tools of the kind in question. The nickel layer protects the machining portion from corrosion and bonds the diamond particles to the machining portion. Yet nickel layers are relatively soft and tend to wear easily. During use of the tool, it is the diamond particles which do the cutting work and, therefore, suffer the greatest stress. Even so the stress in the circumferential surface of the machining portion still is great, particularly due to the resulting chips so that the nickel layer wears off in the course of the time of use.
It was found that the wear described of the machining portion may result in loosening of the diamond particles in the nickel layer from which they may become detached, thereby rendering the tool useless.
It is generally known to increase the corrosion resistance and surface hardness of work pieces by providing them with a chromium nitride coat.
SUMMARY OF THE INVENTION
It is the object of the instant invention to design a tool of the kind specified such that its operational life will be extended.
In a tool according to the invention the nickel layer, including the diamond particles embedded therein, is covered by a coat of chromium nitride, whereby not only the wear of the nickel layer is reduced but also the diamond particles are anchored more firmly than before in the nickel layer. The chromium nitride coat, at the same time, fills theÿuneven surface structure of the diamond particles as well as the gaps separating the nickel layer and the diamond particles. Thus the diamond particles become embedded more firmly. Surprisingly, that has resulted in prolonging the duration of the tool according to the invention by up to four times.


REFERENCES:
patent: 4681541 (1987-07-01), Snaper
patent: 5543210 (1996-08-01), Kullander et al.
patent: 3048383 (1982-07-01), None
patent: 3842915 (1989-12-01), None

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