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Rocking Tester
Forum: Edge Sharpness Testing
Last Post: SHARPCO
5 hours ago
» Replies: 0
» Views: 2
Knife dulls overnight aft...
Forum: All About Edges
Last Post: grepper
6 hours ago
» Replies: 21
» Views: 339
The Great Victorinox Carr...
Forum: All About Edges
Last Post: grepper
6 hours ago
» Replies: 0
» Views: 11
Forum: Relevant General Discussion
Last Post: Mike Brubacher
Yesterday, 03:48 PM
» Replies: 10
» Views: 237
Need variable speed belt ...
Forum: All About Edges
Last Post: Ken S
Yesterday, 09:16 AM
» Replies: 1
» Views: 18
What is good strop belt?
Forum: All About Edges
Last Post: Ken S
Yesterday, 05:36 AM
» Replies: 11
» Views: 73
The ‘Sharpest Knife’ Comp...
Forum: Relevant General Discussion
Last Post: Mark Reich
08-14-2018, 08:21 PM
» Replies: 6
» Views: 160
Edge Structual Weakness -...
Forum: All About Edges
Last Post: KnifeGrinders
08-14-2018, 03:54 PM
» Replies: 3
» Views: 53
Forum: Edge Sharpness Testing
Last Post: EOU
08-11-2018, 10:30 AM
» Replies: 97
» Views: 2,247
The Sharpest Knife Contes...
Forum: BESS
Last Post: grepper
08-10-2018, 05:35 PM
» Replies: 16
» Views: 287

  Rocking Tester
Posted by: SHARPCO - 5 hours ago - Forum: Edge Sharpness Testing - No Replies

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?

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  The Great Victorinox Carrot Test
Posted by: grepper - 6 hours ago - Forum: All About Edges - No Replies

I used the same 5” Victorinox Chef’s knife for this test that I used in the blade dulls overnight after sharpening test.
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.
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.

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  Need variable speed belt grinder?
Posted by: SHARPCO - Yesterday, 06:12 AM - Forum: All About Edges - Replies (1)

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?

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  Edge Structual Weakness - Plastic Crushes Steel
Posted by: grepper - 08-13-2018, 10:28 PM - Forum: All About Edges - Replies (3)

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.

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  What is good strop belt?
Posted by: SHARPCO - 08-13-2018, 10:18 PM - Forum: All About Edges - Replies (11)

Hello everyone. 

A few days ago, I ordered Viel S-5-M 1/3HP. This is my first 1X42" belt grinder.(It has not arrived yet)

So I have to choose belts. For the grit belts, I think 3M Cubitron recommended by grepper is the best choice. But I don't know about strop belt. 

The easiest choice is this.

But I'm also considering a linen belt or an another leather belt. 

I want to hear your recommendation. 

Thank you.

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  Knife dulls overnight after sharpening
Posted by: grepper - 08-10-2018, 09:40 PM - Forum: All About Edges - Replies (21)

This is the knife:
I ground it at about 15° (dps) on my Kally with a 150 grit Cubitron belt.  The 150 Cubitron is my go to belt for general use knife sharpening.  It is very fast, and especially considering I use a light touch when sharpening they seem to last a very, very long time.  I've been using the same belt for a long time now and it seems like new.  Pretty amazing.  Additionally, the 150 grit produces just the toothy edge I’m looking for.
I ground on alternate sides until I noticed a barely visible burr forming on one side of the blade.  I continued grinding on the opposite side as the burr until the very small, barely visible with careful examination under a good light burr formed evenly along the entire length of the blade.  Then I ground the other side in the same manner. 
My new method of deburring is to use a very fine Scotch-Brite belt.  It is by far the quickest method I’ve ever found, and does a most excellently complete job of removing burr without smoothing the toothy edge.
To deburr, alternating sides I did four passes each side with the S-B belt.  I could still see some little flecks of burr, so I ran my fingernail at 45° down each side of the edge and the burr sprinkled off the edge like tinsel rain.
Then I did one swipe on each side of the blade with the rough side of a clean leather belt on the Kally, wiped the blade a few times on my jeans against the top of my thigh to clean off any loose crud and took four sharpness reading from handle to tip:
110, 130, 110, 125
Now here is the interesting part.  I put the knife in one of those flat in-drawer knife blocks overnight.  The knife was not used it just sat in the drawer overnight.  The next day, today, I removed it and checked the sharpness.  The readings were:
160, 150, 150, 175
That’s a maximum 50 point reduction in sharpness from just sitting in a drawer overnight.  Without real proof, I suspect this sharpness reduction is due to a lesser extent oxidation but mostly from metal memory as the extremely thin toothy edge returned to whatever position it was in after the tortuous micro heating, tearing at the steel and bending that happened during grinding.
So, I did one pass each side of the blade using the rough side of the leather belt on the Kally, wiped it clean on my jeans and took four readings from handle to tip:
125, 110, 105, 100

Here is a picture of the edge:


 My best guess is that the one swipe on each side of the blade with the leather belt straightened the edge.
You may be thinking this is just a fluke.  Well, consider this:
The same day I sharpened the Victorinox I sharpened an 8” Calphalon chef’s knife.  It’s a nothing special, big, heavy blade with a full tang that is 1/8” wide at the spine and tapers to the edge.
Unfortunately I didn’t write down all the numbers documenting the saga but I did when I had finished sharpening and pretty accurately remember the rest.  I also noted the final sharpness numbers after checking it today.  So the first and final numbers are completely accurate.
I sharpened it using the same method as the Victorinox.  After sharpening the readings were:
95, 85, 115, 105
After sitting in the drawer next to the Victorinox overnight, the reading were all between
125 – 185
That’s up to a 100 point lower sharpness reading!  So today, as on the Victorinox, I did one swipe each side with the leather belt on the Kally and the readings were:
110, 130, 110, 125
So…, Hey Kids!  Try this at home!  Get a blade as sharp as you can, take four sharpness readings along the edge from handle to tip and let it sit for 24 hours or so.  The next day do another four sharpness readings.  Let us know your results!

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Posted by: EOU - 08-07-2018, 04:05 PM - Forum: Relevant General Discussion - Replies (10)

We may not know much but we do know how to listen. Here are two accessory improvements that came to us via two very good customers, Grepper and Mark Reich. The first is our new ATF-10G (G for Grepper). This new design addresses several use issues with ease and speed of rerunning test media first and foremost of those issues. We also listened to Rick KR on this design and made it about 30% more efficient in the use of test media. It really is a huge improvement and many thanks to Grepper and Rick for suggesting the changes.


We've also made changes to the Knife Fulcrum with new part number KF-10R (R for Reich). Mark Reich suggested a cork cradling point for the knife/straight razor edge and we've now included it. The slot is now .5mm wider as well. The cork insert will be provided with every fulcrum henceforth but use of the cork is optional. The pictures below show fulcrums both with and without cork insertion.


A big thank you to all who have helped us by providing helpful suggestions and ideas. Both of these new items will appear in our online store next week.

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  Sharpness vs Cutting Ability
Posted by: Larrin - 08-06-2018, 10:33 AM - Forum: All About Edges - Replies (9)

New article on the definitions of sharpness and cutting ability, where I answer such questions as:

How is sharpness defined in the scientific literature?
Is sharpness better measured with its cutting behavior or by observing the edge?
Is a thinner edge automatically sharper than a thicker edge?


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  The Sharpest Knife Contest in Sydney 2018
Posted by: KnifeGrinders - 07-31-2018, 04:25 PM - Forum: BESS - Replies (16)

[Image: promo.png]

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  How sharp is this?
Posted by: Ghowe - 07-25-2018, 09:49 AM - Forum: Knife Making & Bladesmithing - Replies (2)

Can't wait to finally qualify some of my knives with the Edge On Up coming in the mail.   This is old school testing along with arm and leg shaving.   I have run out of hair....  LOL


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