|MadSci Network: Engineering|
Hi Jim The concept of "sharpness" is nether well defined nor understood. How a blade cuts, and elementary questions like "Why and when do serrations help" remain unanswered. Sharpness is NOT hardness. Thus a harder blade (or even a blunt stone) can damage a fine blade. A blade sharpened to taper to "a single line of molecules" could not be any sharper. But GOOD blades work by being resistant also to SIDEWAYS forces - which our "line of molecules" certainly would not be! Also the best blades are made of carefully tempered, heat-treated alloys - in other words combinationns of many elementary atoms, (Fe, Cr, Vd, C, S, P, etc) so simply could not exist as a "line-of-molecules" because that would change the molecular structure. It seems that a cut is made in a softer material by the pressure of the blade. This deforms the material being cut, bending and stretching it until it fractures. This allows the blade to enter the crack and force the crack to propagate by the very high stress concentration around its tip. To cut concrete you are better off with a saw. The teeth of the saw need cooling (water is fine). For the most difficult materials a cutting dust would be added (as a slurry) to the water. Diamond being the hardest material known is often used for this. So the say acts as a "conveyor belt" for the cutting dust! John
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