Edge temper

[Ordener]

Hey guys, 
I’ve been thinking about something for awhile now. I’m still fairly new at this sharpening thing, only been doing it for a few years now. I hope this thread doesn’t seem silly to you guys, but here goes. With wet sharpening, there are no sparks, because the steel particles never get hot. In dry sharpening, like I do (I do almost all of my sharpening on a 1X42 Viel), obviously it creates sparks. Sparks are nothing more than superheated bits of metal. I’m very diligent about keeping my fingers on the blade, and dipping the knife in water at the first sign of heat. My question is about the heat creating the sparks. I’m not concerned about the burr, because it’s gets removed. I’m talking about the super fine line that makes up the edge of the edge. Even though the blade never gets hot, is it possible that the edge does? Is it also possible that as the superheated sparks come off the blade, the edge gets superheated as well, only to cool down immediately because of it’s thinness. Could it be that a wet ground edge holds up better? Let me know what you guys think. 

Garry

[grepper]

Only a person gifted with extreme intelligence would pose such a perspicacious question.  I say that because I considered that exact same question myself.  It totally makes sense that the very apex of the edge could get really hot and cool quickly which logically begs the question of how that could effect temper.   You are not alone in pondering this.  It has been considered, examined and tested for in depth here on the Exchange.
 
Unless the Viel has been modified for variable speed, its high SFPM could indeed heat metal to cherry glowing hot simply due to friction and those bits of super heated metal particles you refer to as “sparks” are actually red hot glowing bits of metal torn from the edge and then cooling as they fall through the air.  But, depending on the type of steel being ground, there is another cause of sparks that has nothing to do with edge heating.  This may or may not apply to what you are observing but it is worth mentioning:
 
http://bessex.com/forum/showthread.php?t...60#pid4260
 
EOU performed tests to try and determine if edge heating during sharpening impacted edge retention.  This was done by SET testing the resistance to edge rolling between edges that that were hardened and then sharpened and edges that were hardened after sharpening.
 
Grossly summarizing, testing indicates any difference, if it exists, is negligible. 
 
SET testing measures edge sharpness after a 150g roller is applied to the edge, thereby testing for edge retention.  That is not much pressure applied to the edge.  It is important to understand that slicing a potato will apply 4-5 POUNDS of pressure to an edge which in comparison makes SET testing most grandmotherly. 
 
The theory that you propose may well be true, but more importantly, we probably don’t have any way to test for it.  Even more importantly, the area of the edge is so small and so thin any difference in temper is inconsequential.
 
It’s the bulldozer and the egg syndrome.  Obviously a bulldozer could not sit on an egg without crushing it.  But what about a dozen eggs?  12 eggs could support 12X more weight than 1 egg.  12X or not, the bulldozer would not even notice.  All the king’s horses and all the king’s men couldn’t put Humpty together again.
 
IMHO, from available testing it is my current understanding that, while intellectually entertaining, the effect on edge retention from any heating during normal sharpening is negligible.

If you are truly interested, this is a long thread but addresses your question in depth:

http://bessex.com/forum/showthread.php?tid=391

[SHARPCO]

I believe that even if the belt runs quickly, passing quickly and lowering the pressure can minimize edge overheating. My customers are more satisfied with a knife sharpened with a Viel S5(fixed speed) than Tormek.

[Ordener]

Thanks, guys!