What edge angle is good for supersteels

The knife application determines the way we should sharpen the edge.
Consider what mechanism of dulling prevails in your area of applicaton: rolling or abrasion.

The data we've got on the edge rolling are more pertinent to areas where the knife cuts a softer stuff, and requires high sharpness for quality cuts.
The preferred edge is flat-ground to the apex, i.e. the edge which cross-section is a symmetric triangle.
Stability against rolling is more important in these applications.
triangle.jpg

In our trials at the meat plant, we also tested knives sharpened with a micro-bevel - and the boning operators did not like it, they did not like the lower quality of cuts and more force in cuts.

But the data in this experiment are less pertinent to areas where knife has to cut hard and abrasive materials like cardboards, and requires only working sharpness.
Stability against abrasion is more important in these applications.
The preferred edge in these applications is micro-bevelled, so that the edge cross-section is a "bevelled triangle", so to say.
triangle_with_bevel.jpg
 
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wootzblade said:
But the data in this experiment are less pertinent to areas where knife has to cut hard and abrasive materials like cardboards, and requires only working sharpness.
Stability against abrasion is more important in these applications.
The preferred edge in these applications is micro-bevelled, so that the edge cross-section is a "bevelled triangle", so to say.
triangle_with_bevel.jpg
Click to expand...

This contradicts my reading of CARTA testing but you do not arrive at your positions without basis. What testing lead you to this conclusion and do you have a hypothesis for your observations?
 
CATRA tests edge retention in cutting silica paper, an abrasive material - it is a better controlled version of the manila rope cutting tests.
The lower the edge angle, the better is cutting performance in the CATRA tests, so that a 10 dps edge wins over more obtuse edge angles.
https://knifesteelnerds.com/2018/06/18/maximizing-edge-retention/

By our experiments, however, low angle edges do not withstand the rolling well.
This experiment was to show how low we can go with this or that steel for it to resist the controlled rolling.
All edges in this experiment are flat-ground to the apex (no microbevels).

How to combine the both, and give the edge better retention both to the abrasion and rolling?

In the areas where a knife has to cut hard and abrasive materials like cardboards, and requires only working sharpness, micro-bevelling may be a good option.
In these applications, the knife can be sharpened at 10 dps for better cutting performance, and given a 15-20 dps micro-bevel to improve the edge stability.

Where, for example, our D2 knife without microbevels at 10dps crushes under laterel forces of the rolling - a 15 dps microbevel can improve its retention to rolling and it will score excelent on the sharpness tester. So if we sharpen it at 10 dps, and then microbevel at 15, we will give it the improved cutting performance.

Many people, however, do not like microbevels when they do precision and quality cuts with very sharp knives - and they do not like them for a reason.
 
Thanks. If my understanding is correct, that translates to a lateral force of 0.26 N (0.057 lbs) and downward force of 1.4 N (0.32 lbs) on the apex. Without having a good estimate for the contact surface area, I will not try to estimate the stresses involved.

So, I am curious, what is the basis for choosing the 150 g weight? Or rephrased another way, what type of "real world" scenario does the roller simulate?

I am not being critical. I am just trying to better understand what kind of use (cutting meat, slicing paper, etc.) this optimization study translates to.
 
To what real world cutting scenario relates cutting through the stack of a highly abrasive silica paper in the CATRA testing? Yet, it yields lots of information about the knives.
Not every controlled testing is supposed to translate to a real-life scenario, to be useful. Neither is our edge-rolling test, but it does.

SWIBO knives used in this experiment were used in a separate research on edge retention at a meat plant.
The meat plant edge retention numbers fall within the first 5 rolling cycles on our test stand. 5 rolling cycles on our test stand cause the same effect in the edge as 4 hours of cutting in the meat plant. We use 5 rolling cycles on this test stand to preliminary predict how well this or that brand of knives will withstand rolling in the meat plant.

But SWIBO in this experiment is only for comparison of the supersteel knives to mainstream knives.
Supersteel knives are not used in meat plants, and never will.
 
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I am not trying to claim that CATRA testing is particularly representative of real life use (unless you only use your knife for cutting cardboard). All CATRA testing does is measure the wear resistance of the steel in a somewhat consistent and repeatable way. I have yet to see anyone claim that they have optimized edge geometry solely based on CATRA testing.

I personally like your idea of measuring resistance to edge rolling and chipping in a controllable and repeatable way. However, I do think that the 100 roller cycles test is more of an abrasion resistance test than a rolling/chipping resistance test. The "BESS sharpness score after 100 roller cycles" results seem to be more suggestive of dulling (loss of sharpness) due to abrasion than rolling or chipping. Without images of the edges, it is hard to confirm.

Rolling or chipping will primarily be a function of the maximum stress applied to the edge vs the resistance to deformation and fracture. During the first cycle, the edge will roll / chip or it won't. Without a frictionless material, there will be some amount of dulling due to abrasion with each cycle. After the first cycle, abrasion becomes the most important variable. As the edge dulls, the contact surface area gets larger. As the edge plastically deforms, the edge gets work hardened and and the contact suface area gets larger, increasing resistance to further rolling. The applied stress on the edge gets smaller with each successive cycle. Therefore, the likelihood of the edge rolling or chipping decreases dramatically, after the first cycle.

I don't understand why "super steel" knives wouldn't ever be used in meat plants. It seems like any noticeable increase in productivity and increased service life would eventually justify the additional cost of more expensive steels.

If you decide to do further testing, my suggestion would be to replace the 150g metal roller with meat or some other similar material and make the applied force similar to that used by the boning operators or cutting machines.
 
Karl H said:
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If you decide to do further testing, my suggestion would be to replace the 150g metal roller with meat or some other similar material and make the applied force similar to that used by the boning operators or cutting machines.
Click to expand...

Can I let you know when I need help with my test design in the future?
 
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wootzblade said:
Supersteel knives are not used in meat plants, and never will.
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May I ask you to elaborate more on that? It sounds counter-intuitive since in all areas of applications from tools for car repair to musical instruments professionals advice to use more expensive tools to get it more economical on a long run?
 
Barmaley said:
May I ask you to elaborate more on that? It sounds counter-intuitive since in all areas of applications from tools for car repair to musical instruments professionals advice to use more expensive tools to get it more economical on a long run?
Click to expand...

Because of the edge rolling.
Supersteels withstand abrasion much better than rolling.

In the meat plant operations knives are good as long as they stay shaving sharp. If they are less than "shaving sharp", the quality of cut drops, and the meat presentation worsens. Consumers prefer a piece with clear cuts to the crushed flesh.

So, as soon as the operator feels that he cannot recover the "shaving sharpness" of his knife with steeling, he drops that knife to the sharpener and takes a sharpened knife. In Australia plants have a dedicated sharpener, so that having a knife that is very sharp at all times is never a restraint for the operator. One operator typically uses 2-3 knives through the shift.

On the BESS scale "shaving sharp" means under 160 BESS. When the sharpness score of a knife worsens to 200 BESS, the operator feels that he has to change that dulled knife to a sharp one.
Now look again at the part of my video that shows sharpness after 1 rolling - here I copy the table of the sharpness scores:

1-cycle.png

What do you see? What do these data tell you?
They tell us a counter-intuitive thing: the supersteel edge rolls at the apex almost as easy as the mainstream. At any edge angle from 20 to 12 dps.
It is a counter-intuitive, but firm fact shown by us and others in a number of tests. I explain this in more detail in my Knife Deburring book, in the chapter on high-end knives.

In meat processing, the edge rolling happens more from inadvertent slices on the transporter belt, than from cutting through tendons. In pig processing, rolling is also caused by cuts through the skin.
Practically it means that, if supersteel knives were used at meat plants, because of the early edge rolling in the supersteels, the operators would be changing them at least as frequently as the mainstream knives.

It is even worse, actually. They would need more supersteel knives per shift as compared to mainstream.
While they can do the shiftload of cutting with 2-3 mainstream knives, they would need 3 supersteel knives to do the same load.

Sounds like another counter-intuitive thing, but not for those who does steeling.
Steeling recovers sharpness in mainstream knives very well, and the meat plant operators steel the knife every 10 cuts on average.
But steeling cannot recover the supersteel edge sharpness near as well as the mainstream.

Taking all that into account, and adding to that extra costs for sharpening supersteel as compared to the mainstream stainless steel - you see now why meat plants do not use supersteel knives.
 
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I am not sure if what I am going to say about the meat plant vs your local butcher may be of interest to you.
Probably it will, as I remember how my preferences changed after I did our research for the meat plant.

Butcher shops get the beef and pig carcasses once a week, and sell them through the week.
Meat plants process them the day the get them, and send to supermarkets on the same day - the meat you buy in the supermarkets is fresher than at your local butcher, just read the date on the packaging.

Hygiene at meat plants is very high, resembling that of a hospital surgical theatre. The meat processing floor is cooled to 5-10 C (40-50 F)- the operators work in this temperature with gloved hands. Thanks to that the packed meat has no foreign objects, nor bacteria.
While at butcheries, boning is often done with ungloved hands, and the hygiene is never as good as at the meat plant.

And one more observation, that many of you undoubtedly know, is that of 2 pieces of meat always pick the more pale. Pale meat compared to the red is less stressed, and comes out more tender after cooking.
 
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Wootzblade (Vadim?) - that was a very interesting writing, thank you very much! Of course, it generate more questions: A) What is the steels they use at meat processing plants? At which angle they are sharpened? Which stones do they use for sharpening and honing at the plants? B) Are there any benefits of supersteels at kitchen use? C) Is it possible to test knives edge retention after real life use (like after 5 carcasses processed?) at different angles? D) wouldn't a frequent honing by plant workers on a ceramic rod keep knives sharp without need to re-sharpen then two-three times per day?
 
Supersteel knives do not withstand the apex rolling much better than mainstream for the same reason that they do not hold a very sharp edge much longer than mainstream.
I explain this in my Knife Deburring book, in the chapter on high-end knives.
Video:

Meat plants depend on knives, and invite specialists to do researches, but none of the researches that help reduce costs and give a competitive advantage get into the public domain.
For example, of my 20-page report on the 2-week research we did for a meat plant, I was allowed to publish only a 2-page very general article in the Meat News: BE Campbell meat plant >>
Before allowed to the production floors, we sign a non-disclosure agreement.

I will try to answer your questions, what I can.
A) What is the steels they use at meat processing plants? At which angle they are sharpened? Which stones do they use for sharpening and honing at the plants?

The knife brands I've seen at the plants: Victorinox, F. Dick, Giesser, Dexter Russell.
Edge angle depends on the sharpening equipment the plant uses.
In Australia the plants have a dedicated sharpener that grinds on a set of industrial knife grinders like the US TruHone or Brasilian Cozzini, usually 2 machines - one for thinning worn knives, and one for sharpening. Typical load on the sharpener is 300 knives per shift, and they sharpen at the angle preset on these machines, 36 included. The grinding angle can be lowered on them, but not too low.
In New Zealand, each meat operator sharpens himself, the grinding machines are smaller. The edge angle depends on the views of the trainer that trains them, common in NZ is 30 included.
I saw only stone wheels - though CBN and diamond wheels are available for the industrial grinders, I didn't see them. Nowhere I saw them using bench stones.

B) Are there any benefits of supersteels at kitchen use?

Of course, as everywhere where a very sharp edge is not a requirement. Supersteels hold the "working sharp" edge 10s times longer than mainstream.
If you can control rolling, then the supersteels win in all applications.

But you cannot maintain the supersteel edge with steeling. It is more about hardness: steeling of blades that have HRC 60+ is detrimental to the edge - I write about this in the Conclusions of our Experiments on Knife Steeling >> page 14.

C) Is it possible to test knives edge retention after real life use (like after 5 carcasses processed?) at different angles?

Yes, we did that, but can't publish.

D) wouldn't a frequent honing by plant workers on a ceramic rod keep knives sharp without need to re-sharpen then two-three times per day?

They do not use ceramic rods in the plants - I explain why on the page 15 of the Experiments on Knife Steeling.
The meat processing operator has in his/her holster 3 knives and 2 steels: one steel is polished and used frequently; the second is ribbed and used only when the polished steel cannot recover the sharpness any more.
 
Vadim,
Another counter-intuitive question: after that outstanding report on angles/performance why don't meat plants sharpen at 12 DPS?
Do you have any scientific explanation what exactly happens at 13 DPS with ALL(!) steels?
I am sure you have extensive knowledge on what what restaurant chefs do to their chef's knives - would you like to share it with us since I guess more home cooks here than meat processors :D?
There is very little info about middle grade steels like VG10 etc. What would you say about them?
 
I appreciate the energy in researching these kind of topics! Very interesting!

One question tho about “steeling” “super steels” as to your argument....why can’t the processors just use diamond “steeling rods” to maintain that super sharp edge? Seems to me that solves the problem. The diamond steel rod will cut the carbide of the steel (ANY carbide of ANY steel), thus ensuring a keen and sharp apex.
 
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