Please understand that, not being a chemist or metallurgist, I’m speaking out of my expertise and this is just my attempt to explain what is happening here.  I would more than welcome and hopefully someone here can offer edification, clarification or refutation.
 
In this post, http://bessex.com/forum/showthread.php?t...03#pid4203 Mr. Mark spoke of creating a lot of sparks when grinding hard carbon steel.  I responded in a following post by stating that I have never encountered sparking during basic sharpening with a Kally.  Mr. Mark then suggested that I try the tip of a file.  I did, and indeed, even the lightest grinding produced glowing sparks much like burning a sparkler.  Even just barely touching the file to the 150 grit Cubitron belt created sparks.  It’s rather remarkable.  So much so that it seemed that if only one abrasive particle on the belt touched the file a corresponding spark was produced.  Try it.  You’ll like it!
 
So, what’s gong on here?  It would be logical to assume that there must be something about the steel that increases friction so dramatically as to generate enough heat to melt steel to the point of glowing red hot with even the most minor and ephemeral contact with abrasives.  That makes sense, but I think that explanation is erroneous and there is another cause of the sparking.
 
Oddly, very fine particles of iron are pyrophoric.  Pyrophoric materials spontaneously ignite when exposed to oxygen rich environments such as air, due to heat generation caused by extremely rapid exothermic oxidation.
 
I’m sure many of us have witnessed flash rusting of freshly ground iron.  They don’t call it flash rusting for nothing!  Rust starts to form almost instantly if the material is not protected.  In this case, as soon as flash rusting starts it slows dramatically because the instantaneous coating of rust (oxidation) isolates the surface from exposure to oxygen in the surrounding environment.
 
Grinding during sharpening produces extremely small iron particles.  When grinding, not only is the protective layer of oxidation stripped from the outer surface of the blade by the abrasive, but when particles are torn from the edge the freshly exposed “underside” of these particles, also not protected by a layer of oxidation, is exposed.  This creates the maximum surface area relative to the particle size possible that is available for oxidation.  Even the small additional heat generated by grinding facilitates the oxidation process and the particles burn in the air.

So, I did some searching around and found a pretty good explanation of what I think is going on:
https://www.amazingrust.com/Experiments/...ic_Fe.html

I always found it odd that iron and steel can actually burn.  My first exposure to this was when I was a kid with a chemistry set.  I remember being surprised to see iron filings burn when sprinkled into the flame of an alcohol burner, and equally fascinated to find out how easily steel wool can be ignited with a lighter.  I guess I shouldn’t have been considering I loved setting strips of magnesium on fire.  I highly recommend igniting magnesium as entertainment for kids.  Hours of fun there!  Oddly I still have all my fingers and vision in both eyes.

   

This is ROBAX glass(heat resistant ceramic like pyroceram) on my Viel platen. I thought it was very hard and hardly worn out. But it has worn like this in a few months.

I know there are people who use pyroceram here. How much wear is your glass?

I wanted to know exactly how much less media ATF-10G consumes. Media consumed by ATF-10 and ATF-10G are 55mm and 35mm respectively. i.e. ATF-10G consumed 36% less. I did my best to save media.

Great job.

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BESSU has finished updating it's policy concerning BESS Partner membership requirements for professional home-based and small business sharpeners. This is a group that provides edge sharpness assurance to its customers by placing BESS sharpness scores on sharpened products. The BESS Partner program already includes over 60 members from this business group alone but in consideration of the new guidelines, EOU will begin showcasing some of these new members and their businesses. Congratulations to Kent Hugosson of Tail Motor Scandinavia located in Kiruna, Sweden as the newest of our BESS Partner members and the first to be showcased here.

                                                                                     

                                          

Below are a couple of screenshots from one of Kent's videos . More can be found on his YouTube channel and the links to two can be found below. We like these two Tail Motor's videos in particular because they demonstrate not only a high level of sharpening acumen but also, exactly, how measurements should be taken using our electronic testers.

                                                                                                  

And then the links to two of Kent's videos:

https://www.youtube.com/watch?v=3OMG_qv0CEk&authuser=0
https://www.youtube.com/watch?v=H-iEYJo5...authuser=0

Thank you Kent with Tail Motor and welcome as a new Exchange member and a BESS Partner!

Found this small tool today on internet.

https://www.instagram.com/p/Bp7M7YLl0R-/...z62xkqqnk7

Thomas

Apparently our knife sharpening friends in Australia and New Zealand aren't the only ones reaching new lows. The Russians  in Murmansk were as well although, unlike our friends on the far side of the equator, they weren't concerned with BESS scores but rather bore holes. The picture above is the cap for the 9" diameter and 40,230' deep bore hole and it only took the Russians 19 years, 1970-89 to finish the job. While the rest of the world was engaged in traveling to the moon and probing space, the Russians were drilling holes. They were successful in drilling the deepest hole...ever. 

One thing we found interesting about this story; the temperature at the bottom of this hole is 356° F. That's about perfect for tempering high HRC blades. Our knifemakers and bladesmiths are just going to need a real long rope to take advantage of it.

https://www.facebook.com/TRNDVideos/vide...=2&theater

I found my Viel S-5 makes concave edge at the heel of blade. I think it's because the tension of belt is not even i.e. the tention of outside is lower than in the center. 

How do you prevent it? I think it's helpful to maintain low pressure, but it doesn't seem to be a complete solution.

Greetings,

It is a bit chagrined that I ask, but what are some alternatives to achieving the same function as the Tormek SJ Japanese Waterstone wheel (4000 grit)?  Deburring and polishing after bevel setting and refinement using coarser grindstones are its primary functions.  I'm exploring and in fact have embarked on acquiring and trying paper wheels with diamond pastes, with information and assistance from Mr. KnifeGrinders.  Mr. Grepper suggested I post regarding my trevails and quest as there are many here with relevant expertise. 

Trevails:

At the conclusion of a short season of knife and scissors sharpening at farmers markets, I was loading up, with only the SJ wheel still on the table.  An open can of acetone was also on the table.  The table collapsed, sending both to the pavement, chipping (and cracking) the stone and soaking it in acetone.  Documented on the Tormek forum. After the acetone evaporated, the cracks have closed up quite a bit, but the stone is still toast. 

Potential Solutions:

It has been commented that there are some great and better methods than the SJ stone.  I have the diamond pastes as used by Mr. KnifeGrinders and am awaiting delivery of paper wheels to try them out.  Mr. Grepper said his choice would be a 4000 grit belt. 

The cost of replacing the SJ wheel is quite high ($401 + shipping) and equals or exceeds the alternative of a variable speed/modified Viel 1x40 belt sander as sold/recommended by Steve Bottorff.  I was seriously looking at this option and was about to pull the trigger when I realized I might be able to modify my existing 1x30" belt sander with the variable speed drive Steve refers to.  That stalled a few weeks ago.  It seems very much more attractive now and would provide quite a bit more capability and speed for this and other tasks.  

I would like to hear from others regarding their processes and any recommendations you may care to offer. 

Thanks,

Rick

This is concerned with normal, judicious blade sharpening with something like a Kally. 
 
I’m in no way intending any declaration of fact, but rather, expressing what I think is going on and why.  I’m hoping others with chime in with evidence or suggestions pro or con.  It’s an exploration of issues rather than a collection of conclusions. 
 
I’m going the preface this with the phrase “for all intents and practical purposes”.  Admittedly, there are specific applications where, for example, a possible 10% difference may be significant.  I only add this because this about general knife sharpening and I wish to avoid becoming mired in minutia. 
 
I may be right or I may be wrong.  But, I hope to say it in such a convincing way that even if you think I’m wrong, you will have to at least think I might be right.  (That might be paraphrased from something Bob Dylan said.)
 
That said, IMHO, evidence so far presented indicates that:
 
Judicious sharpening with a Kally does not heat the blade anyway near enough to impact performance.
 
Q:  How do you know there is not flash molecular level heating at the very apex of the edge?
A:  I don’t and probably never will.  And, for all intents and practical purposes, I think it to be irrelevant.  Even if there is heating, it is an extremely ephemeral event both in heating and cooling.  Neither heating nor cooling is sustained long enough to anneal or temper hardened steel.
 
Q:  Assume there is super heating of the surface at the apex, could the super heating and rapid cooling actually harden the surface leaving soft metal just beneath?
A:  Like a chocolate chip cookie?  Do you mean like crispy on the outside and chewy on the inside?  Who knows?  Who cares? I guess maybe it’s possible at the molecular level, but again irrelevant.  If indeed something like occurs, any ramification at the apex is so insignificant that it would be undetectable whilst chopping carrots or SET testing.  While intellectually entertaining, I think this line of thinking is getting lost in minutia and missing the forest for the trees.
 
Q:  Have you seen evidence supporting that belt grinding significantly impacts edge hardness or performance?
A:  Yes.  But it is very scant.  Mr. KG presented evidence supporting the possibility that powered sharpening may impact edge performance in some circumstances.  However, and I will discuss this shortly, that for all intents and practical purposes, the bulk of evidence I’ve seen so far is indicative to the contrary.
 
Q:  Does harder steel, say, RHC 60, perform better and last longer than RHC 52?
A:  Maybe.  A little.  Both EOU SET testing and Mr. KG presented data that indicates that in some cases there may be slightly better edge retention.  However, this data is neither generalized nor conclusive and definitely not the case in most circumstances.  Furthermore, there are disadvantages to harder steel such as difficulty sharpening and chipping that may overweigh any possible advantage.  Moreover, in some of the EOU SET tests, softer steel rolled less than harder steel.
 
Mr. Reich astutely noted that all knives are ground sharp in the first place. I saw a video of the knives being sharpened at, if memory serves correctly, (correct me if I’m mistaken) the Hinckel factory.  They were sharpening on large, dry grinding wheels.  It’s not as if mother knife gave birth to baby knives and they are born, they are ground sharp.
 
Notes: 
 
EOU SET testing data indicates that that in general there is no significant difference in resistance to rolling between HRC 52 and harder steel.  Even if edge softening occurs as the result of sharpening, it is mitigated by the data indicating that as far as range of hardness used in knife steel there is little if any change in resistance to rolling of the edge. In some SET test data harder steel rolled more than softer steel.
 
EOU also performed tests comparing edges hardened and then sharpened, to edges that were sharpened and then hardened.  The latter performed no better than the former, corroborating SET tests that hardness is not substantially influential as far as resistance to rolling is concerned. 
 
But maybe the most encompassing and overriding consideration of all is that our very sharp edges are extremely thin.  We are talking fractions of a micron thin.  That’s really super thin.  There is just not much steel there.  I liken it to supporting a car with an egg.   Obviously if you attempted to support a car off the ground with an egg it would simply crush the egg and make an ugly mess of the egg.  What about two eggs?  After all that would be twice as strong!  What about 10 eggs?  Ten times the strength! 
 
Again, our very sharp edges are very thin.  I placed a potato on a scale and sliced through it with a very sharp, 150 or so edge.  It required 5+ pounds of pressure to slice the potato.  I postulate that due to the extreme thinness of sharp edges, the difference in hardness between HRC 52 and HRC 60 is more or less irrelevant.  There just is not enough steel there to significantly impact the outcome.  So, one egg or ten eggs, is still going to result in a disgusting gooey mess.  Relating this to the subject at hand, even if there is some change in hardness due to sharpening, it is again irrelevant.
 
Disclaimer:
 
I am perfectly open and willing to entertain and accept evidence showing that judicious belt sharpening substantially impacts edge performance.  And, I would do so with alacrity.  That said, I sharpen with a Kally.  It is very fast and produces extremely sharp and perfectly serviceable edges.  I have seen no real-world difference in edge performance between Kally sharpened edges and those that I have sharpened on my water cooled Tormek T7.
 
And, you are going to have to pry my Kally from my cold dead fingers before I’m going to sharpen all my knives by hand.  

Comments? Ideas? All welcome!