Metal tools and implements – making – Blank or process – Cutlery
Patent
1993-12-08
1995-07-11
Watts, Douglas D.
Metal tools and implements, making
Blank or process
Cutlery
30350, B26B 900
Patent
active
054310717
DESCRIPTION:
BRIEF SUMMARY
This invention relates to knife blades and is particularly concerned with a method of producing knife blades.
It has long been known that the surface hardness and wear resistant properties of metal objects can be enhanced by the provision of a hard surface on the metal objects. Thus it is known to generate a carbide and/or nitride enriched or transformed surface, by an appropriate heat treatment, and also known to provide a hard surface coating such as by carburising or nitriding, chemical or physical vapour deposition, electroplating, plasma arc spraying, and other equivalent processes.
When considering a knife blade, providing a hard surface particularly at the cutting edge, it is difficult to put into practice by either of the general techniques outlined above, as a consequence of the very thin sections of blank ordinarily employed in knife blade construction, and the acute angle to be found at the cutting tip. To take a finished blade and subject it to a heat treatment to provide an enriched or transformed hard surface layer, there is the inevitable depletion of carbon from the body of the blade, leaving a blade of insufficient strength, and with surface coatings there is an inevitable build-up of coated material at the cutting edge which has a major adverse effect on the sharpness of the blade.
Attempts have been made hitherto to apply a hardened surface to a knife blade such as by a diffusion heat treatment and by vapour deposition of carbides or nitrides. Here the situation has been the treatment of a tapered blank followed by a single whetting or grinding to form a chisel cutting edge and to put the cutting edge in line with one side face of the blank. When subjected to recognised edge testing procedures, such knives demonstrated no significant improvement in either their original sharpness or in edge retension in comparison with untreated blades of the same configuration.
The object of the present invention is to provide a knife blade with a cutting edge of a harder material than the body of the blade, and a method of producing knife blades with such harder edge, and which display a major improvement in cutting performance in comparison with conventional blades.
According to the present invention, a method of producing a knife blade comprising grinding a first face of a V-shaped cutting edge to locate the lower edge of the first side face at the approximate mid-point across the thickness of the blank, and grinding a second side face of the V-shaped cutting edge to the opposite side of the blank to locate the V-shaped cutting edge at the approximate mid-point across the thickness of the blank, characterised in that following the grinding of the first side face a hard surface is formed on the periphery of the blank over at least the height of the first ground face and after the formation of the hard surface, the second face of the V-shaped cutting edge is ground.
Whilst the whole of the partly ground blank may be provided with a hard surface, it is preferable to shield the blank to limit the application of the hard surface to the cutting edge.
As a consequence of the part-grinding of the blank for the knife, a considerably greater width of the hard enriched, transformed or coated surface of the blade at the intended location of the cutting edge is provided, in comparison with the treating of a finished blade. Thus when it is the case of forming the hard surface by a heat treatment process, the weakening of the body of the blade is reduced, and when the second face is subsequently ground to complete the V-shaped cutting edge some at least of the depleted zone of the body is removed. However, the principal advantage of the invention is that at the actual cutting tip the whole of the cutting edge itself is formed by the hard enriched, transformed or coated surface, and vertically behind which is the body part of the blade providing support for the hard surface at the tip. Equally, and when it is the case of providing a surface coating, the application of the coating to a partly-ground blank is such tha
REFERENCES:
patent: 4653373 (1987-03-01), Gerber
McPherson's Limited
Watts Douglas D.
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