I've not yet achieved BESS values below 200 for edges with obtuse apex angles, e.g., 30 dps or greater.

Versus acute edges, I'm guessing obtuse edges require greater precision at all stages in the sharpening protocol, for similar reasons as why obtuse edges have poorer edge retention ... but that's just speculation on my part.

What are the best BESS scores folks have achieved for highly obtuse apex angles?

I wanted to do a BESS test on my turning spindle roughing gouge. I then discovered that its half round shape was too thick for the standard Edge on Up test filament holder. What to do? I could have referred the problem to our crack volunteer design team. I thought I might try using the Disposable Test Clips. They work very well; the thichness is not a constraint. EOU saved the day once again.

Incidentally, my BESS reading, after the gouge had been used and was hand held, was 255. Nothing stellar, but not quite childproof.

Ken

Woodturners sharpen their tools with bench grinder & 8" CBN wheel.(RPM is 1750 or 3400) But I can't find anybody who use CBN wheel for knife sharpening at high speed. Do you know why?

Check 8m30s

A fellow Exchange member sent me one knife of a set to check out.  He said it was Damascus style, difficult to sharpen and expensive when purchased a very long time ago.
 
Indeed, it is a made in Japan, 17 layer Damascus, Sweden Stainless Steel blade, and seems like a very nice knife.  But that is not what I found most interesting.  What sparked my curiosity was this:

   

Really!  Who knew?  And it’s not flexible plastic that burps to form a vacuum of freshness when you squeeze the handle.
 
I’ve searched around and have found no references to it on-line.  None at all.  I even searched through vintage sections on eBay.  Nothing.
 
Has anyone ever come across a set of knives like this?

   

Many thanks to Mike B. for the A2 blades - they keep us entertained with testing this weekend.
A2 tool steel is high carbon, high molybdenum.
The A2 blade #7 has been hardened to HRC 54, while the A2 blade #11 to HRC 62 - they represent extremes of the knife hardness range.

This simple study is to compare how the blades differing only by hardness respond to deburring.
These two blades have been sharpened exactly the same way, and edge sharpness scores recorded through the process.

The results have come with no surprises: the harder steel is easier to deburr and get sharper.

The blades were bevelled at 15 dps on Tormek using CBN wheels, the edge set on CBN #1000 edge-leading.
Off the #1000 CBN wheel a tiny burr was visible.



Deburring was done on a paper wheel with 5 micron diamonds at the exact edge angle, i.e. 15 dps, with the help of our support for controlled-angle honing and computer software.
Finished on a paper wheel with 0.5 micron diamonds to see effect of burnishing.

5 microns correspond to JIS #3000, and 0.5 micron to # 30,000



In the context of this study, higher BESS numbers indicate a larger burr.

SHARPENING STEP - HRC54 - HRC62 (BESS sharpness score)
Off #1000 CBN - 197 BESS - 159 BESS

Paper Wheel with 5 micron diamonds at 15 dps
2 passes alternating sides - 193 BESS - 138 BESS
4 passes alternating sides - 187 BESS - 127 BESS
6 passes alternating sides - 127 BESS - 72 BESS

Paper Wheel with 0.5 micron diamonds at 15 dps
1 pass alternating sides - 321 BESS - 114 BESS     << burnishing effect - in the softer steel more metal gets displaced over the edge apex, forming a wire edge.

Paper Wheel with 0.5 micron diamonds at 15.4 dps i.e. higher-angle honing at 0.4 degree higher
1 pass alternating sides - 109 BESS - 95 BESS
final sharpness

That's it, only will have to update this post with sharpness scores taken in 24 hours to see if there is difference in the post-sharpening spontaneous dulling.

I have found that in many cases, the Tester(PT50B) is often rocked. 

So I think it should be improved so that the length of the leg can be adjusted to eliminate the rocking. 


How about your testers? Is the EOU aware of this and improving?

I used the same 5” Victorinox Chef’s knife for this test that I used in the blade dulls overnight after sharpening test.
https://www.amazon.com/Victorinox-Fibrox...B000QCLEFC
 
I sharpened the knife then did a series of 10 slices perpendicularly through a carrot making a bunch of carrot rounds each about 1/8” thick.
 
To make the slices I put a marker line on the knife about in the center of the blade, held the tip of the blade against the cutting board and very gently sliced through the carrot.  Occasionally the edge lightly impacted the cutting board, but not with every cut and when it did touch the board it was extremely lightly.  Far, far, far more lightly than the average person cutting carrots would.  I ran out of carrot after making 40 slices.
 
After each 10 cuts I performed 3 measurements from handle towards the tip, just before the marker line, on the line and just past it about 1/8” apart.
 
Results:
 
95, 95, 85 – Starting sharpness
110, 120, 125 – 10 slices
125, 130, 120 – 10 slices
135, 130, 125 – 10 slices
125, 130, 140 – 10 slices
 
It is interesting that the majority of sharpness reduction occurred in the first 20 slices.
 
Taking an average, the mighty Victorinox decreased in sharpness about 40 points with only the most minor, extremely light cutting board contact.  To be honest, it perform better than I suspected it would.  

It should be noted that I was extremely grandmotherly to the edge when slicing.  No normal person that I know of would go about cutting carrots with such a dainty hand.  Umm… Hold on now…  Just because I used that phrase don’t even BEGIN to think I have dainty hands.  Rest assured, I have MAN hands! 
 
I would like to be able to have an unsuspecting chef chop 10 carrots into 40 slices each and see what happened. A wild guess?  We’d be looking at numbers in the 200 – 250 range. 
 
I would like to see other Exchange members perform some real world tests and report the results.  Sharpen a knife and measure the sharpness.  Then put the knife through some normal short-term use, take another set of sharpness readings and report your findings. 

I'm fully aware this test was not very controlled or done scientifically.  That said, it is what it is.
 
This concludes the Great Victorinox Carrot Test.

There are two reasons why a variable speed belt grinder is required. One is over-heat, the other is over-grinding. But....

1. Over-heat
: The heat can be controlled by the pressure as well as the speed. And we can often cool the blade with water(Of course, ice water is better). In addition, Bark River and Ken Schwartz said OK.(https://youtu.be/4cfCYb-Gamg) As you know, Bark River is one of the world leading outdoor knife maker and Ken is one of the masters of knife sharpening. 

2. Over-grinding
: In same belt, the amount of grinding can be controlled by the pressure as well as the speed. And besides, we can use finer belts. 

So I'm not sure the variable speed belt grinder is necessary for sharpening. 

How do you think about it?

This test was performed on a a piece of the cold rolled steel used in the EOU SET tests before hardening.  It is unhardened cold rolled steel.  I sharpened it to a 20 dps bevel using a well used 600 grit 3M Microfinishing film belt and gently deburred using a leather belt on the Kally.  Obviously I did not do a good job of removing burr.
 
The shiny line at the top of edge is remaining burr.
 
The dent in the edge is from the test media, and clearly penetrates well below the edge.  The edge tested 840.

     
 
As the sharpness test was performed, first the burr was crushed against the edge increasing edge width and providing enough support for the test media to allow for more pressure.  As more pressure was applied, the steel edge started to collapse, and as it crushed under the test media load the edge became wider and duller further preventing cleaving of the test media. 
 
As still more pressure was applied, the steel collapsed further and the edge became duller allowing for even more pressure to be applied.  Because the edge was a 20 dps bevel, the edge width continued to increase until the test media finally severed @ 840g.
 
I’m pretty sure I could actually feel that process happening.  The harder I pressed the more pressure I could apply.  It was an interesting feeling.  I’m not really sure the final edge actually cut the test media or the media just ripped in half.  840g is a lot of pressure.
 
It is very interesting that the tiny little plastic test media only of only .009” diameter can actually crush steel.  Yes, the steel was not hardened, but it is steel nonetheless and test media is just plastic.  How can that be?
 
I think it demonstrates how structurally weak knife edges are because they are so incredibly thin.  Even hardened steel rolls when stressed under only 150gf.  That’s not much force.  It takes far more force than that to slice a carrot or potato.
 
While HRC 62 steel may be harder than HRC 50 steel, that hardness difference is more or less irrelevant because our sharp edges are so thin and therefore structurally weak.  It’s the supporting a car on one egg or two type of thing.   While two eggs would provide twice the support the difference is grossly insufficient under that amount of load.

Anyway, I found actually observing a tiny little piece of plastic crushing steel to be a good example of how structurally weak very thin steel edges are.