EDGE RETENTION/ROLLING PART II

[grepper]

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The current design seems to produce "real use" kinds of roll characteristics. If the current design accomplishes this then we ask "why be more gentle with our test edges than real use itself is?" Here's the second reason; it requires multiple passes over the same point with the current SET force used (150 grams) to produce significant rolls. In fact it may take a total of some 50 -70 passes over the same point until maximum roll has been achieved. This indicates to us that we are probably not setting thumb tacks with a sledge hammer at 150 grams of force. 

What is important for me when considering the data produced by the SET tests is how it relates to real-world use of knives.  Considering that general kitchen use of knives exerts orders of magnitude more force on edges than the 150g SET tests, other than being intellectually tempting to ascertain how little force is necessary to differentiate HRC 54 and HRC 62 steel resistance to rolling is, it seems of little real-world consequence. 
 
I have to admit that I had always assumed that harder steel would have better edge retention, but did so only on intuition.  It makes perfect sense that it should. However, SET results indicate otherwise, and interestingly I don’t find that counterintuitive considering how thin sharp edges are.
 
Even lacking any supporting data, I still would assume that if the force applied to the edge was nominal enough that harder steel would indeed be more roll resistant, and I would even guess that hardness/force roll resistance could be proportional.  It’s just sharp edges are so thin that for knife use the hardness differential is irrelevant and inconsequential in real-world knife use.  

Mr. Jan has postulated that it may be explained with the “foil” effect.  I have yet to be able to understand that, so I’m guessing that it’s the sledge hammer vs egg effect.  Two eggs placed on an anvil may indeed offer twice the resistance to smashing as one egg, but when the sledge hammer slams down for all intents and purposes the difference in negligible.