(09-18-2018, 11:59 AM)SteveG Wrote: Brass-rolling test on a Spyderco Chaparral, freehand sharpened to 17dps.
Procedure: Sharpened on fine diamond, then stropped on CrOx/leather (whole blade).  Then resharpened half of the blade on extra-fine diamond (which usually leaves a burr). I rolled with less pressure this time, maybe 1/2 lb.

No-Burr section pre-rolled: Avg 185.7 StdDev 11.5 - rolled: 191.7/25.8
Burred section pre-rolled: 275.3/10.5 - rolled: 297.0/18.7

This is a pretty coarse edge, so I expected quite a bit of variance.  What I didn't expect was the very high numbers, the no-burr section of the blade still easily push-cuts newsprint and phone-book paper across the grain even after being rolled, and could nearly whittle hair right after sharpening.

(09-18-2018, 03:20 PM)KnifeGrinders Wrote:

(09-18-2018, 11:59 AM)SteveG Wrote: Brass-rolling test on a Spyderco Chaparral, freehand sharpened to 17dps.
Procedure: Sharpened on fine diamond, then stropped on CrOx/leather (whole blade).  Then resharpened half of the blade on extra-fine diamond (which usually leaves a burr). I rolled with less pressure this time, maybe 1/2 lb.

No-Burr section pre-rolled: Avg 185.7 StdDev 11.5 - rolled: 191.7/25.8
Burred section pre-rolled: 275.3/10.5 - rolled: 297.0/18.7

This is a pretty coarse edge, so I expected quite a bit of variance.  What I didn't expect was the very high numbers, the no-burr section of the blade still easily push-cuts newsprint and phone-book paper across the grain even after being rolled, and could nearly whittle hair right after sharpening.

The relatively high pre-roll "no-burr" edge score and post-roll increase in its score deviation tell us that the base burr is still there sitting on the apex.
What you actually have on your Spyderco Chaparral is half blade with the base burr, and half blade with a feather burr from the extra-fine diamond.
As you start real cutting, the base burr will behave as a wire edge.

Don't you feel that from the fine diamond to CrOx is too big of a jump? - before taking the  burr to CrOx it should be substantially thinned away. I would add an in-between honing with a 3-6 micron metal polish like Autosol or Flitz - the CTS-XHP should respond well to it.

Yet, looking at your S30V and CTS-XHP, and my Elmax results, I believe we can safely generalize that in response to "gentle" brass/copper rolling a deburred edge scores <= 10 BESS worsening, and an edge with micro-burr > 20 BESS worsening on higher-end steels.

(09-19-2018, 02:37 PM)KnifeGrinders Wrote: You know, Steve your high-vanadium edges may be not lasting because you use ceramic in refining them.

You mentioned that:
S90V
Sharpened on Wicked Edge at 20dps, progression: 800, 1000, 1500 diamond, then medium, fine ceramic.
S30V
Sharpened = Straight off the WE, progression 600, 800, 1000, 1500 Dia, Med, Fine Ceramic

Use of ceramic in your sharpening of blades with vandium contents over 3% may weaken the edge as we detail here:
Edge Rolling in High Vanadium Knives

Se also a post on the Australian forum where a user WóðanaZ compares performance of a high vanadium knife sharpened WITH vs WITHOUT ceramic:
https://www.australianbladeforums.com/vb4/sharpening/38129-sharpening-vanadium-knives.html

(09-16-2018, 03:48 AM)KnifeGrinders Wrote:

The test knife is made of ELMAX, HRC 62.
The edge was set at 13 dps on a #1000 CBN, and honed at the edge angle with 5-micron diamonds, followed by 0.5-micron diamonds.
The tip half of the blade was then cleaned of the base burr at a higher angle on felt with 1 micron diamonds, and finished at a higher angle with 0.25 micron diamonds.
This way I got the same blade having clean apex on the tip half, and wire edge on the heel half.

Marked sections on the blade edge, and took the BEFORE sharpness scores in the 3 sections of the tip half and 3 sections of the heel half.
The PT50A sharpness tester average score on the tip half and heel half has a negligible difference of 2 BESS, in other words the sharpness tester cannot detect presence of the wire edge - and as we know, this is typical of hard higher-end steels. Only by wider dispersion of the scores in the heel half one can tell that its apex is not as clean as in the tip half.
I could not take a decent image on my toy microscope, but there is a shiny line along the edge in the heel half that may indicate light dispersion by the wire edge.



For impact I used a 3/4" copper pipe over a linear bearing, the impact assembly weight 153 grams.
Positioned the copper roller perpendicular to the blade.

Rolled the copper roller along the edge 1 cycle only, i.e. once forward and backward, and took sharpness scores AFTER the impact.
The results are encouraging -


Next plan is to test more high-end steels in the similar fashion, and also see if the impact assembly weight can be adjusted not to affect the clean apex at all (if possible at all). Maybe half a rolling cycle, only one roll in one direction, will be adequate.

A regular end user who has any model of the BESS sharpness tester will not need the SET stand, just a simple copper roller of a standard load with a handle of some sort, which is easy to make.

Steve, appreciate your idea and the preliminary testing you've done. We are moving in the right direction with the copper roller.
Thanks mate, Vadim.

(09-16-2018, 05:48 PM)KnifeGrinders Wrote: As to yours "I don't really know if my edges are burr-free or not (that's the reason I started this exercise)" - we are in the same position, and gradually improve our de-burring technique as we better our burr detection. We are dealing with micro-burrs that cannot be seen or palpated, and my USB microscope can't see them either. Till recently, real cutting was the only way to reveal those burrs - but as this thread goes on we get methods to reveal them, first in mainstream and now in higher-end knives.

(09-25-2018, 08:29 PM)grepper Wrote:

(09-16-2018, 05:48 PM)KnifeGrinders Wrote: As to yours "I don't really know if my edges are burr-free or not (that's the reason I started this exercise)" - we are in the same position, and gradually improve our de-burring technique as we better our burr detection. We are dealing with micro-burrs that cannot be seen or palpated, and my USB microscope can't see them either. Till recently, real cutting was the only way to reveal those burrs - but as this thread goes on we get methods to reveal them, first in mainstream and now in higher-end knives.

I suspect that the micro-burrs can be visualized with a USB microscope but the lighting has to be correct.   Maybe this would work:  Make sure the burr is facing up and turn off internal top light in the microscope.  Take a flashlight and start by holding it about a foot away from the blade illuminating the blade from the side.  Experiment with every possible angle from from very shallow to steeper angles, closer and farther away from the blade. 

It is surprising how drastically the angle of light will change what is seen in the scope.