Wire Edge Prevention

[SteveG]

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.

[KnifeGrinders]

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.
Thanks to the high-carbon excellent steel, this base burr is more like the structural continuation of the apex, rather than a common burr - and that is what makes the high-end knife deburring different from the mainstream. But as you start real cutting, the base burr will behave as a wire edge, only on high-end knives the wire edge performs well longer than on mainstream.

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. After that, finishing on CrOx at a little higher angle cleans away the base burr - in freehand sharpening this step is usually done on a hanging strop as it naturally flexes allowing for a higher angle.

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 in higher-end steels.

[SteveG]

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.

Thanks for your input, I appreciate it, and suspect you’re correct.  I wouldn’t think it too big a jump if there were no base burr (and it’s all I had handy at the time), but given the evidence I’m compelled to agree.

The evidence does look pretty good, I’ll keep at it as time allows and report anything of interest.

[KnifeGrinders]

It is worth highlighting that the edge withstands frontal load much better than the lateral.
We've seen how easy an edge rolls under a 150 g load applied through a roller at an angle as little as 5-10 degrees, but withstands very well the same load applied perpendicular to the edge.
In line with this is that double-bevel blades outperform single-bevel. A single-bevel blade edge is less supported on the flat side and rolls towards it, while the double-bevel edge has symmetric support on both sides that makes it stronger.

[KnifeGrinders]

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/vb...nives.html

[SteveG]

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/vb...nives.html

Thanks for that input, I’ve sometimes wondered about the ceramics, as they seem to polish without really cutting.  I’ll try omitting them and look for the difference.

[KnifeGrinders]

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.

Today I've completed a set of additional experiments and am happy to see how Steve's bright idea is shaping into a method for detecting the wire edge.




The study method is the same as in the first experiment on Elmax: the heel half of the blade has a wire edge, and the tip half is cleaned by higher-angle honing on felt with 1-micron diamonds. 3 samples of sharpness are taken on each half, and the numbers averaged.
In this post I will give averaged numbers, the raw data are here: Link to the Raw Data >>

Steel: S110V HRC 63
Edge angle 13 dps
Copper roller Ø 3/4”
Impact assembly weight 153 gram
1-cycle roll (FW-BW) perpendicular to the edge
Sharpness tester BESS PT50A



Averaged BEFORE - AFTER roll difference:
- clean apex: Improved by 10 BESS
- wire edge: worsened by 12 BESS

The copper-roller worsening of sharpness in the S110V blade is less pronounced than we saw in Elmax, but still is over the cutoff value for clean apex of <=10 BESS that we have established for Elmax.

I have no explanation to the copper-roller caused improvement of sharpness on the clean apex, but this is not an isolated case, and we will see the same on D2 tool steel later.

***

Steel: Victorinox SWIBO HRC 58
Edge angle 13 dps
Copper roller Ø 3/4”
Impact assembly weight 153 gram
1-cycle roll (FW-BW) perpendicular to the edge
Sharpness tester BESS PT50A

Averaged BEFORE - AFTER roll difference:
- clean apex: worsened by 10 BESS
- wire edge: worsened by 50 BESS

We see on this mainstream blade a pattern similar to the high-end knives.

***

Intrigued by the improved sharpness from copper-rolling the S110V clean apex, I subjected to rolling a D2 knife that has a perfectly cleaned apex.

Steel: D2 - Bastinelli Raptor
Edge angle 13 dps
Copper roller Ø 3/4”
Impact assembly weight 153 gram
1-cycle roll (FW-BW) perpendicular to the edge
Sharpness tester BESS PT50A

Averaged BEFORE - AFTER roll difference:
- clean apex: no change

Steel: D2 - Bastinelli Raptor
Edge angle 13 dps
Copper roller Ø 3/4”
Impact assembly weight 153 gram
2-cycles roll (FW-BW & FW-BW) perpendicular to the edge
Sharpness tester BESS PT50A

Averaged BEFORE - AFTER roll difference:
- clean apex: Improved by 7 BESS

We've seen that the copper roller not only is safe for cleanly deburred apex on blades of high-end and tool steels, but can even be beneficial.
Looking close at the copper roller I see a tiny circular groove where the roller contacted the super-steel edges - my vague explanation for the sharpness improvement we've observed is that the apex might get somehow shaped in this groove???

Naturally, we got curious if this wire edge detecting method is copper-specific - the next experiment was to answer this question.

STEEL ROLLER
We repeated an experiment on the Elmax knife in the same way we did with the copper roller, but this time used the standard SET steel roller.



Steel: ELMAX HRC 62
Edge angle 13 dps
Steel roller (linear bearing)
Impact assembly weight 150 gram
1-cycle roll (FW-BW) perpendicular to the edge
Sharpness tester BESS PT50A

Averaged BEFORE - AFTER roll difference:
- clean apex: worsened by 116 BESS
- wire edge: worsened by 142 BESS

Compare this to the copper-roller numbers we had got earlier:
- clean apex: worsened by 8 BESS
- wire edge: worsened by 42 BESS

I think we can congratulate ourselves with the birth of the new method for detecting a micro-burr. For regular owners of BESS sharpness testers I see it as a primitive device of a copper roller weighing near 150 gram on a handle.
There are many more steels to test, and we will be gathering data as we sharpen and deburr more high-end knives of our customers.

*************************************************

WIRE EDGE PREVENTION
We have several ways to successfully clean the apex of the micro-burr:

1) By honing at the edge angle, the base burr can be honed away on hard, relatively brittle steels that are not prone to produce a secondary burr by burnishing from honing - I've seen it on A2 and D2 tool steels, high-end steels of lower toughness, and quality Japanese kitchen knives.
Note that this method will not deburr steels in which toughness and ductility prevail over hardness.

2) By higher-angle honing.
- For high-end and tool steels it is by 0.4 - 1 degree higher than the edge angle;
- For mainstream steels it is by 1.2 - 1.6 degree higher than the edge angle;
- For lower-end steels it is by 2 degrees higher than the edge angle.

The higher-angle deburring works for virtually any steel.

3) Edge-leading deburring.

Before you go to any of these honing modes, you have to thin away the bulk of the burr to expose the base "mother burr". That's why I say that the proper deburring requires minimum 2 steps. Let me detail how I do each mode.

Honing mode 1) at the edge angle
I set 2 honing wheels - one at a shallower than the edge angle, by 0.1 - 0.3 degree less (e.g. a 15 dps edge will be honed at 14.7 - 14.9 dps), and the second wheel at the exact edge angle.
The first shallow honing wheel is thinning away the bulk of the burr, and has a 3-6 micron honing substrate.
The 2nd wheel is honing away the base burr to the clean apex, and has 0.5 micron honing substrate.
In the process of honing I may move the blade between these 2 wheels several times, each time checking sharpness on the tester.

I use the honing mode 1) on blades of hard steels when asked to sharpen a knife to the "bragging rights" utmost sharpness. Typical sharpness score is 25-50 BESS, sometimes 15-20 BESS - i.e. that of a production razor or sharper.
As noted above, this method will not deburr mainstream stainless steels, tough, ductile and poorly hardened steels.

Honing mode 2) at a higher angle
I set 2 honing wheels - one at the exact edge angle, it will hone away the bulk of the burr with a 3-6 micron honing substrate; and the second at 0.4 - 2 degree higher angle depending on the steel as specified above (e.g. a 15 dps edge will be honed at 15.4 - 17 dps), it will hone away the base burr and has 1-micron honing substrate.

I use the honing mode 2) for the majority of practical edges. Typical sharpness score is 55-90 BESS.

The finishing step includes gentle swipes on a clean leather, or a nano-cloth hone or a paper wheel with <=0.25 micron honing agent, at the exact edge angle or a slightly higher angle up to 0.5 degree higher than the edge angle.

[SteveG]

Very nice, KG, thanks for continuing the effort on this, and the superb reporting. And, for the record, I got the idea from you, but thanks for crediting me.

One thing I’ll note is that our sample sizes are small, and variances are pretty high, so some of the data is likely “noise.” I’m looking forward to seeing how this plays out; my roller is now mounted next to my sharpening station.

[grepper]

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.

[SteveG]

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.

How do you orient the microscope; i.e., do you change the angle on that as well, or keep it fixed (and if fixed, then above the edge or to one side)?