Overheated edge BESS scores

[EOU]

When you do test Max don't feel like your PT50B is broken when you see 150 - 200. 40 - 50 BESS are very low numbers for knives. We admit that we spend little time chasing low numbers on knife edges but the fact is the lowest number we've ever generated around here is 83 and then couldn't duplicate it.  That doesn't say too much because we don't claim to be skilled sharpeners but as far as we're concerned a 200 edge with tooth is flat dangerous and we've got the empty band-aid boxes to prove it.

We've got plenty of professional sharpeners who service the restaurant trade that sharpen to 200-250 and they tell us that their customers are ecstatic from both the standpoint of initial sharpness and edge longevity. If you ever feel moved to research the practicality of extremely sharp knife edges then go ahead and sharpen to 100,  chop up one carrot on a cutting board, and then test again. You'll see what we mean.

[KnifeGrinders]

Meat processing professional knives are of stainless steel, with Chromium contents 13%-14%.
Better brands have Carbon contents of 0.6% and hardness 56 to 58 HRC;
lower brands have Carbon contents of 0.5% and hardness 53-55 HRC.

I know that many volume sharpeners deburr knives on a hard felt wheel at high RPM, thinking that well loading it with a buffing compound saves from overheating.
But considering that melting point of the buffing sticks is from 70 C... and over - do they really save?

I wish someone could show me that the felt overheating hypothesis is flawed

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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.

Hi Max, so happy to hear from someone else who works with professional meat cutters.
Could you tell us how often your butchers have their knives sharpened on the 60 grit belt?

I'm asking because once a week or every other week sharpening is different to daily or twice a day when the knife lifespan sets a limit to how coarse the grit may be.
Blade height sets this limit as well - unlike butcher's knives, we generally avoid taking a narrow boner to coarse grit unless absolutely necessary, disregard of how often it is sharpened, and even then it won't be #60

[scott.livesey]

good stuff.  Did the cutters have a steel to touch up the blades as they went?  With steel this soft, one would expect the edge to fold rather than than chip.  your felt overheating hypothesis is not flawed.  industry has been researching this since the 1930's and keeps coming back with the same conclusion, sharpening blades with high speed belts, discs or wheels can cause the apex to heat enough to change the temper of the blade.  
it is interesting to see that the knives used were of basic stainless, I wonder how a blade of "Super Steel", S35VN or Elmax or PSF59 would hold up under these tests.  I know you cannot reveal knife maker's names, but I would not be surprised if they included Dexter, Mundial, Victorinox, Mercer,Icel, Winco, and Wusthof.  How long to the knives last?

[KnifeGrinders]

They prefer a softer steel in the knives for the ease of maintaining the edge with stealing, they use 3 types of steels: a smooth spring-loaded, smooth straightening and abrading rods - and have their set of best practices telling them which when to use.
A quick smooth-steeling improves sharpness by at least 50 BESS.

Super steels in meat processing plants is a pipe dream.
They would not think even of a trial use of knives made of harder steel as these would be harder to maintain sharp as they go. Even the best super steels blunt and roll quickly when hit a bone as often as it happens there, while steeling is useless on them.
Moreover so that the mass production of the professional meat processing knives made of super steels does not exist, and they would have to order them custom made.
Moreover so that they would have to replace their Aluminium Oxide sharpening wheels with CBN or diamond, and change the honing method.

BTW, hollow-grinding wheels for sharpening is preferred over belts for easing-off maintaining the edge sharp by steeling at these plants.

How long do the knives last? - it depends, as I've commented to the MaxtheKnife above, whether you re-edge on grit #60 or #600

[grepper]

Mr. Livesey – What does “high speed” mean when you say, “…sharpening blades with high speed belts, discs or wheels…”?

What SFPM constitutes “high speed”?
How does pressure relate?
How does the coarseness of the abrasive relate?
What about abrasive to blade contact duration?

Can you point me to any references that I could check out?

[scott.livesey]

you gave the answers I was expecting. tests done here http://www.cliffstamp.com/knives/ showed basic knives like the ones in the processing plant had the best cutting efficiency, they might cut less than high carbide knives before loosing edge, but the edge was restored in a minutes work.
can you tell any of the knife brands?

[KnifeGrinders]

Somewhat cautious in naming  brands here...
Scott, like Grepper said I would be obliged if you could point to the overheating studies you mentioned.
Coarse grits are less likely to cause overheating, but I am looking at somebrand SM-111 that has 200 grit coarse wheels running wet at 250 RPM, when its honing wheels run dry at 800 RPM, plus a felt buffing wheel - does this renown sharpening machine maker recognize the overheating, or we see the issue where there is none?
And if we find out that they knowingly ignore facts known since 1930, how can we name their brand/company here and not shame?

[scott.livesey]

Somewhat cautious in naming  brands here...  that is ok, just guessing that the brands are the same ones I would see at a industry supply store here in US
Scott, like Grepper said I would be obliged if you could point to the overheating studies you mentioned.
Coarse grits are less likely to cause overheating, but I am looking at somebrand SM-111 that has 200 grit coarse wheels running wet at 250 RPM, when its honing wheels run dry at 800 RPM, plus a felt buffing wheel - does this renown sharpening machine maker recognize the overheating, or we see the issue where there is none?  they do recognize the issue which is why they run the wheels wet.  the felt buffing wheel you found heated the blade more than your paper wheel
And if we find out that they knowingly ignore facts known since 1930, how can we name their brand/company here?

As one would expect from a company in this day and time, efficiency is king.  
it sounds like each person cutting has access to three steels and is trained on which steel to use depending on condition of the knife.  do the cutters use the same knife every day or do they just pick one up at start of shift?  do they change knives after the 5 hour period or was that just your time there.  or do the knives get resharpened while they have meal break?
there are several very large pork and chicken processing plants nearby, but getting access is harder than getting access to military base. 
i have not come up with exact numbers on how to NOT overheat.  you can sense overheating by keeping a finger on the back side of the blade while grinding or by seeing sparks or by noticing color changes in the steel.  on my grinder I finish with fine(220 zirc or P220 ceramic) belts at about 350 SFPM, wet.  I also use a disc sander with very fine(400 to 1200 silicon carbide) discs at about 300 rpm.  once I have an edge that easily slices copy paper, I go to a fine Norton India, then Smith's 750 diamond, then JewelStik 1200 diamond.

[EOU]

Somewhat cautious in naming  brands here...
Scott, like Grepper said I would be obliged if you could point to the overheating studies you mentioned.
Coarse grits are less likely to cause overheating, but I am looking at somebrand SM-111 that has 200 grit coarse wheels running wet at 250 RPM, when its honing wheels run dry at 800 RPM, plus a felt buffing wheel - does this renown sharpening machine maker recognize the overheating, or we see the issue where there is none?
And if we find out that they knowingly ignore facts known since 1930, how can we name their brand/company here?

You're welcome to pass on that information via email or PM.

[KnifeGrinders]

New Zealand researchers have compared durability of the edge on a knife sharpened with a commercial electrically-driven abrasive-belt knife sharpener (the maker is in their article) with the same blade sharpened manually with a whetstone.

The results showed that using a belt sharpener causes a blade to dull two times faster than the same blade sharpened on a stone.
"... it is thought that powered sharpening overheats and thus detempers an edge.
The softer, detempered structure of the metal causes the edge to fold over more quickly and more easily, resulting in a dull blade..."

Full article can be downloaded from the New Zealand Academy website https://waikato.researchgateway.ac.nz/ha...0289/10004
or from here:
https://core.ac.uk/download/pdf/44290183.pdf