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Constant-geometry edge-flaking of brittle materials


Lithic tool manufacture was the earliest technological exploitation of the brittle fracture of hard materials, and archaeologists have traced and reproduced the evolution of flake tools through various stages of development from the early simple flake knives (Fig. 1) to the sophisticated multi-faceted edges of stone axes. The technology advanced during the period of gunflint manufacture. Of special interest are the simple geometrical relationships between the dimensions of flakes formed in certain controlled conditions1,2. The phenomenon of edge-flaking is also encountered in the attrition of tool cutting edges and in the chipping of precision edges of metrological components, where it is avoided rather than understood, by empirical radiusing (rounding-off). In our effort to improve the efficiency of cutting edges, we have observed that a law of constant geometry seems to apply to the flakes formed at rectangular edges, and the effect is relatively insensitive to the test material.

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