Overheated edge BESS scores

[KnifeGrinders]

As you can guess, they don't apply any microbevels.
And microbevels is my primary interest ATM, after a tentative trial on 2 knives showed that one particular microbevel I have tested at the plant that performs better on a rope, has worse edge retention in boning compared to a regular edge.
Staring at the scores gave me a cognitive dissonance.

Hard to arrange further tests, but will see...

I knew the city consumes lots of meat, but just imagining a herd of 2,500 pigs daily walking into the plant all the year round - and this is only one plant.
When I travel in the country, I don't see too many pigs, bur they are there in drillions

[grepper]

" I thought we are the best in Sydney till I met their sharpener; to start with, he sharpens almost all knives at about 100 BESS.  But when I asked him to sharpen to his best, and he spent a minute per knife instead of the usual 20-30 sec, the 4 knives we tested scored 40-50.  Can you beat it? I can't, at least not at this speed."

I don't see how he could fail to get 100 or sharper considering he spent an entire minute at!    

100?  40-50???  That's amazing.  What method of sharpening?  Hand?  Powered?  Belt?  Wheel?  Stone?

I want to do that too!

[KnifeGrinders]

Off their heavy-duty industrial grinder the knives come between 150-200 BESS, then he hones freehand.

You realize that little findings can be shared in the public domain, as long as we don't want to subject ourselves to the peril of knife makers' brand war. When I discussed with the plant if any of the data can be published, they denied for that reasoning.

[grepper]

“You realize that little findings can be shared in the public domain”
 
That's too bad, but understandable I guess.
 
If you are able to and I completely understand if you can’t, I’d be interested in learning more about that guy’s sharpening method.  30 seconds to 1 minute is very quick with some amazing results.  Can you discuss the grinding grit and honing methods?  Finish with toothy/smooth?

What does that guy do to so quickly sharpen with such good results?

I’m not interested in any proprietary information, but obviously that guy is a very skillful sharpener and I’d like to learn from it if possible.

[KnifeGrinders]

There is no method there, he is just a freehand talent, and we cannot replicate talents, unfortunately.
His sharpening is chiefly 2-step.
Off their slow grinder grit #400, the edge has a burr.
He then freehand deburrs & hones it on a rock-hard felt wheel with a buffing compound similar to White Rouge, at high RPM.
As a result, the toothiness gets buffed away, and the edge shoulders (the bevel line) get smoothed into the blade face.
No traces of the burr, even foil, even wire.

[grepper]

Thanks.

I hate your answer.  It's not fair.  Nobody told me I'd ever have to have any talent!

[KnifeGrinders]

Now, with that 2-step sharpening they use, and looking back to the diagram, what may be an explanation for the difference we see?
The grinding is done at 250 RPM with a circulating fluid coolant, and can be ruled out.
We have the felt wheel left.
My sharpening was different in that instead of the felt wheel I used a slotted paper wheel - the slotted wheel cools like a fan.

Asking myself how a felt wheel might cause the quicker edge blunting over the first hour, the only explanation I can think of is the apex overheating.
So I put a finger on his rock-hard felt rotating at 2850 RPM, and got a burn in a fraction of a sec, indicative of 80-90 C.
The steel in these knives is relatively low-carbon, around 0.5% - for them intermediate annealing starts at 260 C.
Watching him honing, he spends on the felt about 2 sec per blade side, alternating sides 4-6 times - around 10 sec overall.
I think some annealing of the apex in the area up to 0.5 micron thick is probable.
0.5 micron or 250 BESS is where the two knives start scoring the same.

[me2]

Are the workers able to tell between your knives and his? Their sharpness requirement is fairly high.

Are the knives carbon or stainless steel? Any idea of hardness?

[MaxtheKnife]

good read here so far for 2018......keep adding more.
.
my butcher store guys still like the 60 grit blades for their meat cuts here........that is 60 grit belt.....followed by felt with 400 grit black with pressure maybe 10 to 12 passes each side on platen and then 3 or 4 on leather w/white........no clue what edge tests at since i did not have pt50b until several days ago. will test the next go round......i know they are very sharp and toothy.

[grepper]

“I think some annealing of the apex in the area up to 0.5 micron thick is probable.  0.5 micron or 250 BESS is where the two knives start scoring the same.”
 
Very interesting.  That seems a reasonable hypothesis in consideration of your supporting data.
 
It’s curious that they go to the trouble of using a slow grinding wheel with circulating fluid coolant, but on the other hand use a high speed, heat producing wheel for honing.  I’m guessing that they don’t fully understand the possible heating issues in the honing step.  It would be interesting to see if they tried using a less heat producing process for honing if blade performance more closely matched the blades you sharpened.
 
As Mr. Max mentioned, I have also been curious how a well sharpened toothy edge would perform in that production level environment.   I’m guessing that pig disassembly is a mixture of both chopping and slicing with the majority being slicing.