Sharpening Knives

[dcarch]

I certainly would not dispute the expert in their finding that "The peak temps measured, walked up to 2000°C for split seconds in the very surface (some microns)."

My question would be how does heat effects the metal when it is only microns thick. Is it possible that it actually enhances the hardness of the metal? The rapid cooling by the large high heat conductance of the metal underneath is like oil quenching hardening.

I don't know if such incredibly small amount of heat can have any effect. It is like when you comb you hair with a plastic comb, you can actually generate a million volts of electricity.

dcarch

I think I didn't make myself clear. :-)

Absolutely true if you use a belt sander. You will mess up a good blade.

I was wondering about wiping a few times on abrasive paper which can cause high temperature microns thick.

dcarch

[weinoo]

With full respect to the professionals who really do wear down their edges, and the hobbyists who enjoy sharpening for its own sake (and I totally get the sexiness) - I agree with weinoo that what is usually needed for most home cooks is honing - restoring the edge.

I think if this is done religiously, I don't have to take my EP out more than twice a year.

If I was to sharpen free-hand at this point, my knives would be ugly real fast.

But an unsharpened cleaver can easily smash garlic.

Edited September 20, 2013 by weinoo (log)

[Dakki]

I certainly would not dispute the expert in their finding that "The peak temps measured, walked up to 2000°C for split seconds in the very surface (some microns)."

My question would be how does heat effects the metal when it is only microns thick. Is it possible that it actually enhances the hardness of the metal? The rapid cooling by the large high heat conductance of the metal underneath is like oil quenching hardening.

I don't know if such incredibly small amount of heat can have any effect. It is like when you comb you hair with a plastic comb, you can actually generate a million volts of electricity.

dcarch

I think I didn't make myself clear. :-)

Absolutely true if you use a belt sander. You will mess up a good blade.

I was wondering about wiping a few times on abrasive paper which can cause high temperature microns thick.

dcarch

OK, I was confused then. My bad.

Yeah, I think that is just an example made to illustrate a larger point - that temperature can spike extremely high in small volumes of material even with slow (hand) grinding, and the effect will be much greater with a (much faster) powere tool. As you can imagine, the temperatures reached in a microns thick knife edge would be enough to "burn" the steel if you applied that energy continously for several seconds.

[RobertCollins]

What is the real difference in an oil stone and a water stone? I used oil stones in my tradesman days and could shave with my electricians knife [it was crap steel but if you are an electrician cutting anything from plastic/sometimes rubber insulation to the copper itself, you would be sharpening everyday anyway] at least it started each day sharp that way.

I have some diamond stones that have a metal grid over their diamond surface that want water not oil, they seem to do a very comparable job,maybe quicker.

I do have an EP Apex, I just feel [likely wrongly] that I'm happier with the job I get with the diamond water stone, and a fine cutting edge in 4 or 5 minutes.

So when and why do I want to use either or any of the three?

An aside, I clean the [what I saw referred upthread as ]SMARF [i haven't looked up that yet] off at water stone and my ceramic "steel" with Bon Amy with water and a sponge.

ETA: The first line of this thread refered to Chad Ward's wonderful writing for eG,which was what caused me to join and learn so much all these years from this. I hope to see more of this great teaching.

Edited September 20, 2013 by RobertCollins (log)

[Dakki]

What is the real difference in an oil stone and a water stone?

With waterstones, the abrasive action is done by the slurry formed by detached stone particles and water. Oilstones' abrasive particles cut while still rigidly attached to the stone itself. You can actually use water with (new) oilstones.

The straight-edge razor community has developed (rediscovered?) a really interesting technique to essentially vary their waterstones' grit by althering the thickness of the slurry. I'll post a link as soon as I can remember what the heck it's called.

[Dakki]

Pfft, it's called "One Stone Honing." I'll turn in my smart person card now.

[dcarch]

The best knife can be forever destroyed in a fraction of a second if the fine edge is over heated.

I would never take a knife for sharpening to someone operating a grinding wheel without using water.

 

dcarch

 

 

[Laurentius]

6 minutes ago, dcarch said:

I would never take a knife for sharpening to someone operating a grinding wheel without using water.

 

The thing is, unless you're looking over their shoulder, you can't be sure.

 

While I generally agree with you about excess heat, I do sharpen on belts.  Worn belts, light touch, a water dip, and feeling with an ungloved hand work well for me...

[Anchobrie]

I sharp mine with wet stones.

[Norm Matthews]

My mom had only one knife and one sharpening stone, actually half a stone. It was shaped like an elongated football but it was broken.  When she sharpened with it, she ran the stone along the whole surface of the knife so it got thinner and thinner as time went along.  By the time she had to stop using it, it was so thin that it was about as flexible as a piece of spring steel and it must have been two inches shorter.  

[paulraphael]

“The goal is to get the knife sharp while taking off the least amount of material"

 

This is great to see, but not the practice of most of the sharpener trucks I've seen. Choose wisely.

[weinoo]

8 hours ago, paulraphael said:

“The goal is to get the knife sharp while taking off the least amount of material," says the Green Point Knife Truck man. This means he's not the typical knife truck man. 

 

Perhaps I should have entitled it thusly: "Take Your Knives to This Truck!"

 

These guys even sell some nice looking stuff out of their truck:

 

 

 

[weinoo]

On 1/28/2024 at 5:45 PM, paulraphael said:

Choose wisely.

 

That's good advice...for life too!