Does thinning or working extensively on a knife's profile impact hardness?

[konsuke]

I watched this video - from a professional knife shop - were they said that they actively cool the knife when doing more serious work (unspecified, even with stones) because doing lots of "strokes" can raise the temperature enough to counter the initial heat treatment? Is that true, resp. should I be worried when I re-profile/re-grind/thin my personal knife at home?

 

[myguidingmoonlight]

Not a scientific reply but unless your knife is scalding hot by the end of manual stone work, I think the heat treat will be fine. Even then, scalding hot is nowhere near heat treat temperature.

Grind wheels are a different story I'm sure.

 

[stringer]

should I be worried when I re-profile/re-grind/thin my personal knife at home?

No.

Sharpening by hand using stones will not generate enough heat to boil the water on the stone. Ergo it won't generate enough heat to alter a knife's heat treat because that would require temperatures much higher than the temperature of boiling water.

 

[HumbleHomeCook]

Queue the post about so-and-so discovering the temperature at the very edge of the knife, even on stones jumps to XXXX degrees!

 

[Pie]

I was surprised by how much heat can be generated by bench stones, more specifically oilstones. That being said there’s no way it gets hot enough to mess with the heat treat.

 

[Troopah_Knives]

If you are doing the work by hand on stones you are probably fine.

I would caution against the idea that "if the water doesn't boil you are fine". Heat from grinding is dumped directly into the edge over a very small volume of material which can raise the temperature very quickly without any noticeable increase in the temperature of the water extracting heat from it. Put another way imagine heating a very thin metal wire over a flame and quenching it into a cup of water. The water temperature would not change but that does not mean the wire didn't get extremely hot.

If you are going near power tools then I would definitely be concerned. Bench stones with a bunch of water, not so much.

 

[stringer]

If you are doing the work by hand on stones you are probably fine.

I would caution against the idea that "if the water doesn't boil you are fine". Heat from grinding is dumped directly into the edge over a very small volume of material which can raise the temperature very quickly without any noticeable increase in the temperature of the water extracting heat from it. Put another way imagine heating a very thin metal wire over a flame and quenching it into a cup of water. The water temperature would not change but that does not mean the wire didn't get extremely hot.

If you are going near power tools then I would definitely be concerned. Bench stones with a bunch of water, not so much.

Definitely different logic as soon as you move to powered mechanisms. I have burnt my fair share of edges on belt sanders.

 

[JustAnotherJoe]

Just to add, thinning would be mostly dumping heat into the body of the knife, as opposed to edge work.

If we are going to compete on how much heat we can generate with a benchstone, I'll put my money on a dry medium sintered ceramic that's is just startting to glaze. Now those are some hot stones!