Heating The Very Edge Whilst Sharpening

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Heating The Very Edge Whilst Sharpening

Postby John Harper » Fri Nov 22, 2013 10:34 pm

Hi,

I read a number of references to Roman Landes saying that if dry abrading whilst sharpening, the vicinity of the very edge gets overheated. Could somebody please explain what techniques he used to determine this?

Thanks in advance for any forthcoming information, and

Cheers
John
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Re: Heating The Very Edge Whilst Sharpening

Postby Roman Landes » Sat Nov 23, 2013 5:35 am

It is done by Vickers micro hardness HV 0,1, and smaller.
Requires a professional metallografic equipment and electrochemical polishing.
Over engineered is a "German" attitude and makes rockets fly...
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Re: Heating The Very Edge Whilst Sharpening

Postby Johan van Zanten » Mon Nov 25, 2013 1:01 pm

Somebody advised me to use rubber wheels loaded with aluminum oxide to sharpen my knives. I don't dare to do it for the reason Roman mentions in his book. These rubber wheels turn at pretty high rpm.

I use low rpm water cooled stones on a Tormek.
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Re: Heating The Very Edge Whilst Sharpening

Postby John Harper » Wed Nov 27, 2013 6:05 am

Hi Roman,

Thanks for your reply.

How close to the edge apex did you manage to get with the micro hardness tester and what sort of drop in hardness did you detect?

I would have thought that looking for changes in the microstructure, within a micron or two from the edge would have also given an idea of the temperatures reached there. Am I on track?

Cheers
John
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Re: Heating The Very Edge Whilst Sharpening

Postby Tony Yan » Wed Nov 27, 2013 11:14 am

Roman Landes wrote:It is done by Vickers micro hardness HV 0,1, and smaller.
Requires a professional metallografic equipment and electrochemical polishing.


Hi Roman Landes,

Wow!! HV 0.1 and smaller? That's 0.1 kgf applied force or less? I don't know metrology nor metallurgy, but that sounds like a very delicate measurement! I think I'm very impressed. :)

My understanding of Vicker's and Vicker's micro-hardness come from the Gordon England website:
http://www.gordonengland.co.uk/hardness/vickers.htm
http://www.gordonengland.co.uk/hardness ... rdness.htm

Sincerely,
--Tony Yan
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Re: Heating The Very Edge Whilst Sharpening

Postby Josh F. » Tue Jan 07, 2014 11:45 am

While speaking with a metallurgist in the scissor field I explained in layman's terms what Roman's tests had revealed (a damage of the temper at the last micron or two of the edge after dry grinding). He stated that it is such a small difference though that one couldn't really notice in day today use. He actually said that the same heat builds up in even when water grinding but it is just washed away very quickly (if I understood him correctly). Roman, did you conduct the same tests with water grinding?
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Re: Heating The Very Edge Whilst Sharpening

Postby Roman Landes » Wed Jan 22, 2014 2:08 am

Josh,
In some terms the man is right.
First the physics don`t lie, as he stated himself the effect is there.
Second lets look at geometry, scissors compared to knives usually have a rather obtuse angles for their edges.
And unlike knives the mechanical force they work with, is way greater than a single edged knife in a regular cut will experience.
The obtuse Geometry of course will lead to a bigger thermic mass behind the edge and thus lead to a smaller heat affected zone around the edge. So the heat jam that will be build up in a obtuse angel is far less effective.
Now go to the link below and check out the picture i provided Cliff Stamp and Kevin.
http://www.cliffstamp.com/knives/forum/read.php?17,17655,22265#msg-22265

What you see is a professional gardening scissor examined. It show an angle on the edge of 45° and an hardness loss on the edge of minimum 5HRC through grinding. While the scissors work with more force its not so significant when they loose some edge quickly.
Lets say they degrade form 5µm sharpness to 15µm sharpness within a few cuts.
You wont notice much difference in force through this effect.
But you start to loose cutting quality by squeezing more than clear cutting.

Now lets go to the other end of cutting a razor blade.
Your razor blade is around 0,2-0,3 microns sharp the angle is around 18°-20° total.
The volume fraction that has to absorb (cool away your heat) is far less than with a scissor.
Is will be much more effect you can see.
This is why the razor blade industry and high quality knife making companies (Japanese) cool their edges whilst sharpening.

To answer your last question the grinding tests have been done in Solingen some decades ago, that simply proved the fact on a scientific base.
Razor blade industry and probably the early knife makers centuries ago new it too.
The pics you see in the link document the latest test I have done,those are form fall 2013.
Since the physics haven't changed much the effect has been there, ever since.

Just to let me understand my fellow spirits.
Why does such a simple fact of physics, like cool grinding to get performance in a knife, always get so much brain trouble?
I'm so many times asked and sometimes even badly argued at, about this issue (Not you Josh!)
Its hard to understand for me, why ppl always want to challenge that point in particular.
Over engineered is a "German" attitude and makes rockets fly...
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Re: Heating The Very Edge Whilst Sharpening

Postby F. Page Steinhardt » Wed Jan 22, 2014 9:15 am

Roman Landes wrote:
<SNIP>

Now lets go to the other end of cutting a razor blade.
Your razor blade is around 0,2-0,3 microns sharp the angle is around 18°-20° total.
The volume fraction that has to absorb (cool away your heat) is far less than with a scissor.
Is will be much more effect you can see.
This is why the razor blade industry and high quality knife making companies (Japanese) cool their edges whilst sharpening.

To answer your last question the grinding tests have been done in Solingen some decades ago, that simply proved the fact on a scientific base.
Razor blade industry and probably the early knife makers centuries ago new it too.
The pics you see in the link document the latest test I have done,those are form fall 2013.
Since the physics haven't changed much the effect has been there, ever since.

Just to let me understand my fellow spirits.
Why does such a simple fact of physics, like cool grinding to get performance in a knife, always get so much brain trouble?
I'm so many times asked and sometimes even badly argued at, about this issue (Not you Josh!)
Its hard to understand for me, why ppl always want to challenge that point in particular.


Roman,
I have gotten in many heated (pardon the pun) arguments with people on this subject in the last couple of years, and most of the people have "an investment" in dry grinding, whether it be on paper wheels, belts whatever. There are people like a certain person on Bladeforums who have a lot of investment in promoting paper wheel sharpening, or just have a lot of knives that have been sold that were sharpened on a dry belt, they got what they think is a sharp edge, and to have someone suggest that they might not have the best, sharpest knife on the planet from whatever their particular process is devalues what they have out there, or challenges their feeling of superiority. The question of wet/cooled sharpening versus dry grinding is just as much a challenge to their worldview as the quenchant arguments that exploded a few years ago. There are people who are truly interested in making the absolute best knife possible, who will be happy to learn better ways, and feel that improvement is an evolutionary process, I personally am happy that the knives I make now are much better than the ones I made ten years ago, but there are people who seem to feel that they sprung fully formed from the hammer of Thor as the best bladesmith the world has known, and anything that challenges the superiority of any knife they ever sold is blasphemny

-Page
Without craftsmanship there is no art, only a sad suggestion of what might have been.

http://www.sunshadowdesign.com
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Re: Heating The Very Edge Whilst Sharpening

Postby Robert C » Fri Jan 24, 2014 9:44 pm

Grinding does create heat . Trick is to not create more than necessary .The best way of course is to use fluid like water. I've seen my share of soft edges and broken tips , my assumption is grinding heat.
In my bearing industry experience I've seen enormous damage from grinding so knives are not the only victim ! They usually use a cooling fluid also !
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Re: Heating The Very Edge Whilst Sharpening

Postby Roman Landes » Mon Jan 27, 2014 9:37 am

@ Robert
Its absolutely spot on.
Basically every industrial grinding professional knows this fact.
It seems just in the knife makers corner some ppl. assume physics don't apply to them.
Actually I wish that those who promote dry grinding an edge, shall make the proof, that a hot grinding will not affect their edges.
Please use standardized replicable methods such as micro hardness according to (ASTM E384 - 11e1) "Standard Test Method for Knoop and Vickers Hardness of Materials"
Until they do proof us wrong with a standardized method our "model of the world" based on physical facts counts.

So please go out and proof this wrong!
Over engineered is a "German" attitude and makes rockets fly...
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