The present invention relates to manufacture of knife blades, and in particular relates to accurate mechanically-performed grinding of sharp edges on a series of similar knife blades.
In many knives the blade is tapered between its back and its edge by being beveled on both sides, either with a flat surface or hollow ground. It is desired in sharpening such a blade to provide a narrow edge bevel area on each side of the knife blade, ground at a somewhat steeper angle to provide the actual sharpened edge. It is desired for that narrow portion to conform closely to the profile of the blade, and for the two sides of the blade to be ground symmetrically. The edge bevel areas should be parallel with the entire knife profiles from the plunge to the tip of the blade to be cosmetically appealing.
Mass produced knife blades have slight dimensional variations resulting from the grinders used to produce the flat or hollow ground beveled side surfaces of such blades. In order to produce a desired sharp edge with symmetrical edge bevels on opposite sides of a knife whose blade has been beveled or hollow ground on both sides, it has therefore been necessary in the past for a person to hold each blade and to move the blade manually along a suitable abrasive wheel to sharpen knife blades by hand during the normal process of manufacture. That is, it has not been practical to use machines to automatically grind a final bevel surface to define a sharp edge with the necessary angle to produce a desired appearance, bevel width, and symmetry.
Some knife blade blanks intended to have serrations in an edge have been beveled flat or hollow-ground on each side to establish a tapered thickness of the blade, narrowing from the back of the blade toward the edge. The tang of such a tapered blade blank has then been clamped into a fixture, and a serrated portion of an edge has been ground into one beveled face using an abrasive wheel dressed to the shape required to provide the desired serrated edge profile. This method of holding a knife blade has not been found useful in sharpening entire knife blades during manufacture, however, because a knife blade cannot be located precisely enough by clamping the tang of the blade to form symmetrical edge bevels reliably on both sides of a blade without having to confirm or readjust the position of the blade between grinding steps. As a result, automatic sharpening of tapered knife blades has not been practical, and such blades have previously been costly because of the amount of skilled labor needed to finish the edge of each blade.
It is therefore desired to be able to grind both sides of a knife blade automatically to produce a symmetrically ground sharpened edge without having to readjust or check the blade's position in a fixture holding the blade during the process of grinding the edge.