Topic: Proper Maintenance of a Knifes Edge

[wootz]

Our latest research on chopping boards is in the Edge Stability Testing section on our website:
http://knifegrinders.com.au/SET/Chopping_Boards.pdf

Abstract from the research conclusions:

"Of all plastic boards, the most edge-friendly is the ubiquitous high density polypropylene, while the
expensive Yoshihiro Hi-Soft board is nothing to rave about in comparison.
Acacia end-grain chopping board has no advantage over the long-grain in keeping your knife sharp;
while the end-grain bamboo board is definitely bad."
...

[john.jcb]

Our latest research on chopping boards is in the Edge Stability Testing section on our website:
http://knifegrinders.com.au/SET/Chopping_Boards.pdf

Abstract from the research conclusions:

"Of all plastic boards, the most edge-friendly is the ubiquitous high density polypropylene, while the
expensive Yoshihiro Hi-Soft board is nothing to rave about in comparison.
Acacia end-grain chopping board has no advantage over the long-grain in keeping your knife sharp;
while the end-grain bamboo board is definitely bad."
...

This was a most interesting read and I think definitely myth busting.

As I was looking at the comparison charts I thought you must had transposed the data. I am glad to see that all my boards are good for cutting. I wish a SEM was easily available to look at the differences from before and after. Did you try this using the Victorinox knives after they had been sharpened using the process outlined in your recent "Knife Deburring" book? Do knives that are at or near maximum sharpness dull following the protocol you used?

Another question is raised also; if the knife is getting sharper as shown in the tests why do they get dull cutting relatively soft things like tomatoes, potatoes and meat? I wonder if technique enters into it.

[Drilon]

Thank you for this comparison. I like data based results! Great.

Drilon

[wootz]

I have added to the end of the above PDF a page with full experimental data.

Looking at the sharpness numbers, you can see why the high-density polypropylene board comes as the best chopping board - I highlighted it in green in the table.
It was mystical to observe the knife getting sharper and sharper with every next 200 slices on it, how the edge sharpness improved twice and went on near razor sharp between 60 - 70 BESS as I kept cutting.

I am yet to digest these findings.

[van]

very interesting study

[wootz]

...
This was a most interesting read and I think definitely myth busting.

As I was looking at the comparison charts I thought you must had transposed the data. I am glad to see that all my boards are good for cutting. I wish a SEM was easily available to look at the differences from before and after. Did you try this using the Victorinox knives after they had been sharpened using the process outlined in your recent "Knife Deburring" book? Do knives that are at or near maximum sharpness dull following the protocol you used?

Another question is raised also; if the knife is getting sharper as shown in the tests why do they get dull cutting relatively soft things like tomatoes, potatoes and meat? I wonder if technique enters into it.

New identical knives with factory edge were used for this test on purpose, to rule out other variables and focus on the chopping board material.
Important is that the testing was done with the load within natural cutting forces.

Re-sharpened knives, provided they are cleanly deburred, outlast the factory edge, it is a commonplace.
With these data on hand, we can confidently say that if the knife fails early on an edge-friendly chopping board, it is due to incorrect technique and chiefly due to the edge rolling. 
Knives dull by 2 mechanisms: abrasion and rolling.
In my test knives are perpendicular to the chopping board and if they dull it is due to abrasion.
If the cutter often scrapes the board laterally, or holds the knife out of the vertical, the rolling will prevail.

E.g. the habit of scraping food pieces off the board with the spine of the knife rather than the edge eliminates one cause of rolling.

[Drilon]

Of course I started immidiately to search for a source of HDPP chopping/cutting boards. But the result was disappointing, I found no supplier for these boards in home kitchen sizes. Any suggestions where to look?
 

[Jan]

Another question is raised also; if the knife is getting sharper as shown in the tests why do they get dull cutting relatively soft things like tomatoes, potatoes and meat? I wonder if technique enters into it.

Tormek recommends to cut through the end grain of a block of wood as a deburring method for some blades. In this experiment we possibly also clean/deburr and polish the edge, which results in lowering the BESS sharpness score.

[wootz]

... In this experiment we possibly also clean/deburr and polish the edge, which results in lowering the BESS sharpness score.

Suppose it is not about the burr, suppose the apex is clean - any other explanations?

[wootz]

FACTORY EDGE VS RE-SHARPENED

I re-sharpened the knife used in our chopping board experiment at the same 16 dps, using our sharpening and deburring procedure for mainstream stainless steel knives. The edge angle was controlled with our computer software for Tormek, and verified with a laser protractor.
The only difference was that I started on #80 CBN wheel to remove the metal affected by factory sharpening, and then followed our standard procedure on CBN wheels #200, #400, #1000 and deburred as described on our website http://knifegrinders.com.au/06Procedures_SS.htm

The edge scored 80 BESS, so I had to bring it to the initial sharpness of the knives used in the experiment which was 120 BESS - I did it by rounding the apex by gently honing it on the rock-hard felt wheel with 1-micron diamonds on Tormek at 2.5 degree higher than the edge angle, till the edge started scoring the same as the knife in the experiment.

Then I tested the low-density polyethylene board the same way we did with the factory-sharpened knife.
If you ask me why i did not use the best edge-friendly high-density polypropylene board - I avoided extremes on purpose as I wanted to look further into the phenomenon of self-improved sharpness as such.



Following are the sharpness data and chart.
We see that the re-sharpened and cleanly deburred edge also gets sharper due to this mystical phenomenon, and sharper than the factory edge.
We see that it is not plastic specific, and not about the burr.
I am still scratching my head for a plausible explanation of this phenomenon.
Comments are welcome.

[john.jcb]

Of course I started immidiately to search for a source of HDPP chopping/cutting boards. But the result was disappointing, I found no supplier for these boards in home kitchen sizes. Any suggestions where to look?

Here is one source. Different colors are offered for different food.

https://www.amazon.com/Commercial-Grade-Plastic-Cutting-Board/dp/B01LZNZZX6

[john.jcb]

FACTORY EDGE VS RE-SHARPENED

Following are the sharpness data and chart.
We see that the re-sharpened and cleanly deburred edge also gets sharper due to this mystical phenomenon, and sharper than the factory edge.
We see that it is not plastic specific, and not about the burr.
I am still scratching my head for a plausible explanation of this phenomenon.
Comments are welcome.

Is it possible that during the first cuts of the experiment the knife cuts the board forming a 32° V in the material and as you make more cuts this V is acting as a strop on the sharpened edge? Since there is no burr no tearing at the apex would occur as was seen in your other deburring tests. If the knife were moved to a fresh section of the board after each cut I wonder if the data would change?

[Jan]

Yes John, I almost agree with you. 

In my understanding deburring a knife edge using low speed hard felt wheel impregnated with 1 micron diamond abrasive results in edge surface with roughness cca 0.1 micron. That can be considered a nice, smooth surface, until we realize, that the apex diameter is only some 0.2 or 0.3 micron (for edge with BESS score 100 or 150). Some of the edge surface irregularities may be caused by burr residua which were more firmly attached to the edge and survived the deburring. The experiment shows that repeated movement of the edge in a 32⁰ V groove can remove/smooth some residual edge surface irregularities and lower the BESS score.

[Drilon]

Of course I started immidiately to search for a source of HDPP chopping/cutting boards. But the result was disappointing, I found no supplier for these boards in home kitchen sizes. Any suggestions where to look?

Here is one source. Different colors are offered for different food.

https://www.amazon.com/Commercial-Grade-Plastic-Cutting-Board/dp/B01LZNZZX6

[Drilon]

Of course I started immidiately to search for a source of HDPP chopping/cutting boards. But the result was disappointing, I found no supplier for these boards in home kitchen sizes. Any suggestions where to look?

Here is one source. Different colors are offered for different food.

https://www.amazon.com/Commercial-Grade-Plastic-Cutting-Board/dp/B01LZNZZX6

Thank you, John.