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Knife Grinders -- What Edge Angle Is Good For SuperSteels

Posted by jasonstone20 
Knife Grinders -- What Edge Angle Is Good For SuperSteels
June 04, 2020 09:39AM
[www.youtube.com]




------------------------------------------------------------------------------------------------------------------------------------------------------
"Gotta love living in 2019 baby, (63rc too soft on a production knife)"
--Shawn Houston
__
"I am still discussing issues of steels and performance at this stage."
--Cliff Stamp
__
"Cause geometry cuts, .....steel determines the level and the duration"
--Roman Landes
__
"But in general, I'm all about high performance, Ergos, safety. That's why I've been accused of 'designing in the dark' "
--Sal Glesser
------------------------------------------------------------------------------------------------------------------------------------------------------
StoneSharpEdges

Jason D. Stone on YouTube
Re: Knife Grinders -- What Edge Angle Is Good For SuperSteels
June 04, 2020 11:37AM
Interesting there, a lot going on, this is the article for that experiment :

[knifegrinders.com.au]

He has a general article page :

[knifegrinders.com.au]

I have concerns about his results, mainly because his initial sharpness results are odd,



Note he can't sharpen D2 and that simple stainless steel at 11 dps or under, I have gone under that significantly, D2 as low as ~5 dps with very high sharpness, very resistant to cutting deformation (it doesn't deform on carboard/ ropes, cutting on hard woods, etc.).

I can't explain why that simple stainless steel just won't even get sharp at all on 10 dps, he notes that score is a super dull blade, and again I have sharpened simple stainless steels well below that angle, Kyley has as well (more than us).

Jason, maybe reach out to him, invite him here, see if we can talk. Some of his result seem in line with what I expect, not all of them, and it doesn't look like he has tried to correlate his measurements to actual use (from what I can see).
Re: Knife Grinders -- What Edge Angle Is Good For SuperSteels
June 04, 2020 12:13PM
Cliff,
I have tried a few times to contact him. I will try again, as I believe he is on the right track, and asking great questions that I would like to see the results for. I believe he has an advanced degree also, I think in a technical field.

------------------------------------------------------------------------------------------------------------------------------------------------------
"Gotta love living in 2019 baby, (63rc too soft on a production knife)"
--Shawn Houston
__
"I am still discussing issues of steels and performance at this stage."
--Cliff Stamp
__
"Cause geometry cuts, .....steel determines the level and the duration"
--Roman Landes
__
"But in general, I'm all about high performance, Ergos, safety. That's why I've been accused of 'designing in the dark' "
--Sal Glesser
------------------------------------------------------------------------------------------------------------------------------------------------------
StoneSharpEdges

Jason D. Stone on YouTube
Re: Knife Grinders -- What Edge Angle Is Good For SuperSteels
June 04, 2020 01:31PM
Perhaps deburring is more of a problem at the low angles.
Re: Knife Grinders -- What Edge Angle Is Good For SuperSteels
June 04, 2020 02:47PM
[www.youtube.com]




------------------------------------------------------------------------------------------------------------------------------------------------------
"Gotta love living in 2019 baby, (63rc too soft on a production knife)"
--Shawn Houston
__
"I am still discussing issues of steels and performance at this stage."
--Cliff Stamp
__
"Cause geometry cuts, .....steel determines the level and the duration"
--Roman Landes
__
"But in general, I'm all about high performance, Ergos, safety. That's why I've been accused of 'designing in the dark' "
--Sal Glesser
------------------------------------------------------------------------------------------------------------------------------------------------------
StoneSharpEdges

Jason D. Stone on YouTube
Re: Knife Grinders -- What Edge Angle Is Good For SuperSteels
June 04, 2020 02:56PM
Cliff,
I am not sure what the problem is with the sharpening. You should be able to take those steels to low edge angles. I have done it also, with no loss in initial sharpness compared to other steels. He has an elaborate sharpening method, which looks like it should work. Could the use of the paper and felt wheels on a powered machine be causing an issue? I sent a video of his sharpening method to Roman Landes, and in an email he said that was his concern about the sharpening process.

------------------------------------------------------------------------------------------------------------------------------------------------------
"Gotta love living in 2019 baby, (63rc too soft on a production knife)"
--Shawn Houston
__
"I am still discussing issues of steels and performance at this stage."
--Cliff Stamp
__
"Cause geometry cuts, .....steel determines the level and the duration"
--Roman Landes
__
"But in general, I'm all about high performance, Ergos, safety. That's why I've been accused of 'designing in the dark' "
--Sal Glesser
------------------------------------------------------------------------------------------------------------------------------------------------------
StoneSharpEdges

Jason D. Stone on YouTube
Re: Knife Grinders -- What Edge Angle Is Good For SuperSteels
June 04, 2020 03:04PM
I do find it odd that the high carbide PM steels don't have an issue, while the ingot steels do have an issue. He is just measuring initial sharpness, and I can't think of anything that would cause a drop in initial sharpness just from lowering the edge angle. If anything, the initial sharpness should increase.

------------------------------------------------------------------------------------------------------------------------------------------------------
"Gotta love living in 2019 baby, (63rc too soft on a production knife)"
--Shawn Houston
__
"I am still discussing issues of steels and performance at this stage."
--Cliff Stamp
__
"Cause geometry cuts, .....steel determines the level and the duration"
--Roman Landes
__
"But in general, I'm all about high performance, Ergos, safety. That's why I've been accused of 'designing in the dark' "
--Sal Glesser
------------------------------------------------------------------------------------------------------------------------------------------------------
StoneSharpEdges

Jason D. Stone on YouTube
Re: Knife Grinders -- What Edge Angle Is Good For SuperSteels
June 04, 2020 03:24PM
I sent him an email inviting him to join this discussion.

------------------------------------------------------------------------------------------------------------------------------------------------------
"Gotta love living in 2019 baby, (63rc too soft on a production knife)"
--Shawn Houston
__
"I am still discussing issues of steels and performance at this stage."
--Cliff Stamp
__
"Cause geometry cuts, .....steel determines the level and the duration"
--Roman Landes
__
"But in general, I'm all about high performance, Ergos, safety. That's why I've been accused of 'designing in the dark' "
--Sal Glesser
------------------------------------------------------------------------------------------------------------------------------------------------------
StoneSharpEdges

Jason D. Stone on YouTube
Re: Knife Grinders -- What Edge Angle Is Good For SuperSteels
June 04, 2020 03:26PM
Quote
Larrin
Perhaps deburring is more of a problem at the low angles.

I have not used that equipment so I have contacted a few people who do and who I know run very sharp blades.

It doesn't surprise me that the Tormek is prone to causing large burrs, especially with cbn/diamond abrasives (as they don't form a slurry), and the sharpening method to keep the same angle and switch sides is known to create large burrs. But with skill/experience I would find it odd that could not be overcome.

However I would not generalize from that result to sharpening in general, and even a casual glance at data should show why. In general 15 dps is a very large angle, it is often used for chopping blades. I don't normally even run that high, closer to 10-12 dps unless I am cutting very harsh woods. It would seem odd that a small utility knife would need higher angles than 1.2 kg blades doing this :

[www.youtube.com]

The major problem with that article is that over generalization :

"However, we recommend not to sharpen conventional tool steels (e.g. D2, M4, Lohmann PGK etc) under 15 dps even when sharpened with diamonds/CBN – they require a 15 dps edge for stable performance."

The data doesn't support that, it only supports that one guy sharpening one knife with one type of equipment in one example of those steels has an issue under 15 dps on a very artificial test which has not been shown to correlate to actual use. It is just odd to me how a person has a problem sharpening a knife and they conclude without reservation that it is a steel issue.

However I don't like to talk about work externally, I prefer to talk to people directly, so I am going to contact that guy, invite him here, IF he isn't interested, well then there is no way to discuss the work aside from external commentary.
Re: Knife Grinders -- What Edge Angle Is Good For SuperSteels
June 04, 2020 05:39PM
Quote
jasonstone20
If anything, the initial sharpness should increase.

It has to be a technique thing, Alvin Johnston used to run 6-8 dps apexes on everything, including those steels. He would deep hollow grind full flat knives as they didn't cut well enough, sharpen flat to the stone, so the edge was 2-3 dps, and the micro-bevel at 6-8 dps. His own knives were full hard 1095/M2, but he would regrind anything, including Buck's etc. and he always sharpened them the same way.

I have a dialogue started with Vadim, I will basically take an article, do a response and send it to him in email, and get him to respond, and then I will repost the dialogue, once I confirm he knows it is semi-public (the dialogue*)

(*) I don't mind having private dialogues, but won't have them about public issues, i.e. if you make a public claim I won't have a private dialogue about it, I have had enough of them in the past it is just insanely annoying. You read problems, people make false conclusions, but you can't correct them because the reason why you know they are wrong can't be revealed.
Re: Knife Grinders -- What Edge Angle Is Good For SuperSteels
June 04, 2020 06:01PM
Regarding low angles and Tormek :

"These results indicate that as the 2β edge angle is dropped from 40o to 20o it
becomes more difficult to sharpen blades to the same edge quality. This probably results
from the reduced thickness of the blade at locations just behind the edge. This reduced
thickness will increase bending stresses of the sharpening operation which can lead to
bending and cracking of the metal along the edge. Hence, the more gentle abrading
action of the waterstone over the 220 grit wheels becomes more of an advantage at the
lower 2β angles."



That edge is just mangled.

From :

[www.tf.uni-kiel.de]

In short, Verhoeven had issues sharpening at ~10 degrees on the Tormek (note when he says 40 to 20, he is talking included).

I am always skeptical think about moving from high speed power sharpening on non-slurry abrasives to hand sharpening on slurried abrasives, there is just way too much changing there.

(Kyley noted Verhoeven spoke about issues in his work, hence why it pays off to talk to people).
Re: Knife Grinders -- What Edge Angle Is Good For SuperSteels
June 04, 2020 06:20PM
Cliff,
Interesting. Good find. I would think that the edge might even be more damaged, since the CBN wheels used are #160, #400, and #1000:
[youtu.be]

------------------------------------------------------------------------------------------------------------------------------------------------------
"Gotta love living in 2019 baby, (63rc too soft on a production knife)"
--Shawn Houston
__
"I am still discussing issues of steels and performance at this stage."
--Cliff Stamp
__
"Cause geometry cuts, .....steel determines the level and the duration"
--Roman Landes
__
"But in general, I'm all about high performance, Ergos, safety. That's why I've been accused of 'designing in the dark' "
--Sal Glesser
------------------------------------------------------------------------------------------------------------------------------------------------------
StoneSharpEdges

Jason D. Stone on YouTube
cKc
Re: Knife Grinders -- What Edge Angle Is Good For SuperSteels
June 04, 2020 06:43PM
Quote
Larrin
Perhaps deburring is more of a problem at the low angles.

if you use the sharpen to form a burr method, yes i think so. it will be a struggle, at 5dps maybe.. 10dps.. its not that thin, but maybe with the swibo steel its very malleable when thin.. myabe with pressure its flexing while sharpening and making a foil edge over and over that rolls on itself.

can only speculate.

using buffing wheels edge trailing might not be taking off the burr cleanly.

i wonder if anyone has done any testing on paperwheel honing.

i know from experience using buffing wheels as a convex maker that this is the time with the most heat build up of any process. without extremely light and rapid movement feathering a blade i can change the color on a simple steel very easily.. the secret is that many people just flip and buff off the burn color in the blink of an eye and wont know if they are not paying attention that they are doing it.

id feel more encouraged by the slow tormek leather hone speed.

----------------------------------------------------------------------
It's not Cliff, its Dr Stamp
#kebabstickcut, it's a thing - make it happen
Re: Knife Grinders -- What Edge Angle Is Good For SuperSteels
June 05, 2020 06:16PM
We see this 10 dps barrier in mainstream steels since our experiments in 2018 http://knifegrinders.com.au/SET/SET_research.pdf

Our data do not contradict Cliff's, as we put different edge on the knives - the edges are not comparable.

We grind straight to the apex, and our edge cross-section is a symmetric triangle.


This edge splits hair, but at low angles its apex becomes so weak that the test line dents it, and the sharpness tester shows a catastrophic drop in sharpness.

Cliff grinds short of the apex (the burrless method), and then microbevels, so that the edge cross-section is a "bevelled triangle", so to say.


Obviously, Cliff's technique gives a stronger edge, but what you get is not a 5-8 dps edge, it is a 5-8 dps edge with a more obtuse micro-bevel.
Such an edge will not dent on the test line, and the sharpness tester will show an excellent score.

Still, disregard of the sharpening methods, at some low angle both these edges will not withstand the rolling, and the lateral forces will crush them.

We know that the best performing edge angle is the lowest a given steel can retain under the load.
This experiment was to show how low we can go with this or that steel for it to resist the controlled rolling.
There is no such thing as "just put the lowest angle you can" - every class of knife steels has its best performing angle.

The superhard supersteel S290 showed the best resistance, and we say that it will retain a working edge at 10 dps. It may do well even at lower angles, but we did not test that.

The premium M390 knife showed the best resistance to rolling at 12 dps, and the D2 at 15 dps.
We had established long ago that the 12 dps edge is also the best performing for mainstream knives.

This does not mean, of course, that you cannot cut with the M390 and D2 at 10 dps. This means that the 10 dps in these steels will not resist the serious rolling as well.

This and other controlled experiments guide our practical sharpening, they are our basement.
This experiment is only one of many we take into account
Edge stability testing >
Re: Knife Grinders -- What Edge Angle Is Good For SuperSteels
June 05, 2020 10:09PM
I will respond more in depth on this later, but just to clarify something.

In science, we generally learn from that which contradicts us, in opposed to Math where we learn by constantly expanding what we can figure out based on what we already know. If we were not willing to be contradicted, well we would all still believe that things fell because solid things "belonged" on the ground and gasses "belonged" in the sky, so that's why steam rose.

If anyone finds out something that contradicts something I have said or done :

-be specific about what I have said/done, ideally provide a link
-be very specific about what you have done, and why it leads to a contradictory conclusion

Then the fun begins as we have to figure out :

-did one of us to an experiment prone to some kind of bias or error that we didn't account for
-deductions not supported from the data, outside influences not considered

If we never changed our perspectives, well we are as dumb today as we were yesterday, so by all means, fire away if anyone has issues.
Re: Knife Grinders -- What Edge Angle Is Good For SuperSteels
June 06, 2020 10:33AM
As a response to the edge stability work :



1 " The general consensus is that supersteels shall not be sharpened at the low angles of mainstream knives, because of their large carbides"

Here I am concerned simply with the vagueness of the references, what
exactly are the super steels, what is a low angle, and what are large
carbides. Some of this is explained further on, but it can be
critical to be specific because so many times generalizations are made
which will end up not at all matching what you are thinking
because the reader assumes you mean something else. This I
realize is a bit of a pedantic point, but in general, the more clarity
and the more detail, the lower the risk of misinterpretation.


2 "Carbides in conventional tool steels like D2 are near 20 microns in size. Powder metallurgy forms smaller carbides, near 1 micron, but still oversized compared to the mainstream steel."

Ok here is the first major point of concern, while P/M carbides in
general are really small, P/M steels used in knives can have very
high carbide volumes and this can force carbide aggregates which are
even larger than 20 microns (10V, 15V, 121REX). Hence any problems due
to the large carbides in conventional steels have the potential to be even
worse in such P/M steels because you are now going to deal with the inter-carbide
fracture in the aggregates.


3 "Supersteels for knife making typically have hardness near 60 HRC."

Here we have to take care between what is common, and what is
possible. For a lot of mass production knives, the hardness can be in
the mid-fifties for a number of reasons such as
resistance to gross damage, easily ground
on any abrasive, responsive to steeling, etc. . But, it should be
noted that almost all of those production steels can be hardened to 60
HRC, and a lot of them are capable of being hardened well beyond that.
It only takes around 0.5% free carbon to achieve maximum hardness (~66
HRC). This is again being very pedantic, but if you look at
discussions you will see people thinking that you have to use some
very extreme alloy P/M steel to have 60+ HRC when in fact they are
only needed for extreme wear resistance, simple 1095 can achieve 66-68
HRC as tempered.


4 "As Larrin Thomas has shown, there is a good correlation between the CATRA test and rope cutting tests - these two tests test the same thing - the wear-resistance to abrasion in perpendicular cuts"

Two points here; first you really need a link here so that people can
see what is being referenced, and second I don't think Larrin's work
shows that at all, for reasons I can discuss in detail (in short, none
of those tests are blinded so they are all subject to expectation
bias, and the correlation coefficients at times show high unexplained
variances > 30%). Now to be clear, I would expect CATRA tests to
correlate to that kind of cutting, and the more CATRA-like you do the
cutting, the higher the correlation I would expect.


5 "Next, we see that beginning with 11 dps sharpness drops in the D2 conventional tool steel. At 10 dps sharpness of the D2 steel deteriorates further, and in the mainstream steel it becomes really bad, worse than just dull"

This is my first real point of concern. It would not surprise me that
a knife out of a ~55 HRC steel is less resistant to
compression/lateral loading, and so it would have lower edge stability
than a knife at 60+ HRC with similar alloy content. This is essentially just replicating a HRC
reading. If the load is actually applied with a contact area which is
on the scale of the carbides then you could also see carbide level
effects (Roman Landes) otherwise you are essentially measuring hardness.
But, I have concerns if the initial sharpness
simply isn't present as I would have concerns then on the sharpening
method. I have sharpened those steels at angles less than 10 dps
without issues on initial sharpness, more on that in a separate post.

Here micro-graphs of those steels in the as-sharpened state would have
been useful. If I had to guess, I would suspect what is happening is
what Verhoeven found when sharpening knives at very low angles on the
Tormek, see above.


6 "From 20 to 12 dps we see difference in the edge stability between the supersteels and the mainstream knife. Among the supersteels, the superhard supersteel S290 is definitely a leader in the edge stability. M390 shows better than D2, and the D2 shows worse of all supersteels."

I disagree the data shows this, what I would argue the data shows is
that there is no difference between any of those steels until 10 dps,
and then only the X50CrMoV shows a significantly lower reading, but
that is suspect because its initial sharpness was not present. The
actual change in sharpness it experienced was the lowest, which I
suspect means the apex was just the thickness after sharpening (hence
why the initial sharpness was so low).


7 "BESS sharpness score after 100 roller cycles"

Similar here, I think only the X50Cr13MoV steel is behind the others,
the other three steels do not look to be significantly different in
performance based on the spread in the data. To be specific, look at
this from the S290 data "324 286 381" now it is clear that this
doesn't represent the knife actually doing better at 12 degrees than
it did at 13 and then getting worse at 11, this jumping around of > 40
points is just scatter in the results. Now if we assume that is a
decent estimate of one-shot scatter then in order for any of those
numbers to be significantly different, we would want them separated by
2x that number (assuming a normal distribution, that gets you in the 5% range)
which would mean they should be ~160 apart to be confident they are really likely
to be different and that you are not just seeing random variances.

What you really need, at a minimum is about 3-5 runs to get a decent
estimate of the scatter, and then you can do a statistical test of
significance to see does the reading actually decrease with apex
angle and does it decrease from one steel to another.

8 As a couple of general points of concern :

I would want to see a commentary/comparison to Roman's work on edge
stability, as that is peer reviewed, and done to the rigor of a PhD
thesis, and is preexisting so at a minimum it has to be evaluated
especially as it is appears to contradict the claims in this work, as
Roman argues high carbide steels have very low edge stability because
they sufferer from carbide related failures even though they have very
high compressional strengths. This difference may be due to the fact
that the loads applied are very different in contact area between your
work and Roman's so he is seeing effects on the scale of the carbides,
but you are seeing gross steel properties.

There has to be correlation established between this test and behavior
in use, and ideally that use has to be at least single blinded, OR use
such large scale samples that you can be semi-confident that you are
not seeing user bias. I am concerned myself that a metal roller on an
apex is measuring something similar to what a knife experiences in use
cutting soft materials like ropes, cardboard, foods, etc. .

As well, a push cutting test of sharpness doesn't correlate well at all to
edge retention in a large scale of applications which are draw cutting.
It is possible for knives to score very low on push cutting tests and yet
have very high sharpness on a draw, hence they are still very sharp even though
a push cutting test shows otherwise. In short, the BESS test is simply an invalid
way to measure sharpness for that type of cutting, it isn't even measuring
sharpness. I developed a simple push cutting test in ~2000 on light cord
but quickly found it was insensitive to actually measuring sharpness in
use because it wasn't replicating the type of cutting the knife was doing.
Hence I developed another way of measuring sharpness was to set the
load fixed, and measure the amount of draw/travel along the blade required.


As well, even IF say you look at X50Cr13MoV and find that the edge does
require 15 dps to resist rolling, that doesn't even imply that you should not
grind at 10 dps because the increase in cutting ability at 10 dps could easily
mean the blade has a longer lifetime in use, lower fatigue rates, higher
productivity etc. .
Re: Knife Grinders -- What Edge Angle Is Good For SuperSteels
June 06, 2020 12:12PM
Ok, to clarify on my sharpening, this is a bit long.

Summary : I don't leave a large flat on the edge, and apply a very high angle micro-bevel.

In detail :

When I started sharpening, I quickly figured out there were two steps :

-grinding the edge to meet
-getting rid of the damage at the apex

The first part is easy, you can literally see it happen if you use a coarse stone, the second part, well there was a mix of myth and magic about that and the techniques described literally went off into deep fantasy land about how you would burn the burr off on a strop and similar. My background was physics, so I did a bunch of reading, came up with some ideas on what was happening physically, had my own ideas and started talking to people who were doing the same. In a short period of time I came up with a very simple sharpening method :

-grind the knife just until the apex forms
-do a few passes at a very high angle to remove any damage
-do a few passes at the original angle to minimize the micro-bevel

This was very much influenced by Sal Glesser, Joe Talmadge, Jeff Clark, Phil Wilson, and Wayne Goddard. These were the people who wrote more about facts and data vs myth and legend.

As I started working with more stones, I realized a few things :

-the stone that does the first part has to be sharp and not loaded and be able to efficiently cut the steel

This meant unfortunately that different stones had to be used on different steels and you had to maintain stones, even on ones that almost everyone said never had to be maintened. I had to recut India stones often for example as in a short period of time they were just galling the steels as all the abrasive was rounded. I later discovered if money was not an issue at all, then one set of stones would be fine, just use the SPS-II stones with silicon carbide and you were good to go for shaping and then finish on diamond plates.

Then with experiments with more stones I realized you want different types, so now I do something like this :

-grind the edge with a very friable stone that produces a slurry to set the edge (this minimizes damage at the apex from over grinding)
-set the apex with a few high angle passes with a very flat stone which does not release grit
-back bevel at the original angle with the first stone, flushed (no slurry)

Using procedures like this I could get sharpness levels well in exceeding commercial utility blades, and would do things like a true 90 push cut on newsprint at > +2" from the point of hold, and this was with a 600 grit DMT apex. These knives would do silly things like whittle hair like it was wood, shave hair well above the arm, etc. .

With minor modifications, that's how I sharpen now. But in some cases it isn't ideal because the knives are not ideal. For example I sharpened a bunch of kitchen knives yesterday and it was :

-10 dps with a India stone, coarse
-20 dps for the micro-bevel, fine India

No back bevel, and I was not concerned about slurry because I knew I was going to set a significant micro-bevel (you could barely see it, so fraction of a mm). I wanted this 20 dps micro-bevel because the knives see impacts off of metal, and I wanted the 10 dps edge bevel to increase cutting ability, reduce fatigue, increase control etc. . I also recut the edges down to < 0.005" because they were not chopping/prying knives, for those I typically go 0.015" to 0.035" depending on how hard the person is going to be. If they are going to take that knife and pound it through a frozen chicken, well 0.035" bevels are needed.

The method I use now can typically reset an edge on a knife which is even visibly damaged in 1-2 mins, by properly matching the stone/grit to the steel and having a pre-set optomized edge bevel. If I had to regrind the blade, well I would typically do that power sharpening, unless I was bored in which case it would be ~5 mins for a small blade, I don't think I would regrind a 10" chef's by hand and lower the bevel, I am never that bored. I would just use a sub-100 grit belt and reset the primary grind, by applying a very small convex blend next to the edge.
Re: Knife Grinders -- What Edge Angle Is Good For SuperSteels
June 06, 2020 06:28PM
Here is a quick data point :



This knife isn't martensitic steel, it isn't hardened (I bent one of them into a complete 180, it tears like plastic). It is horrible to sharpen as it is gummy. The knife is :

0.040" thick
0.6" wide
0.3" high bevel

The primary bevel is ~2 degrees I normally run it with a secondary edge bevel, usually at 20 dps because it is really soft steel so it will get impacted easily on bone/metal etc. . However I ground it off and sharpened it flat.

-2 mins on a coarse no-name alumina stone, ~100 grit
-remove the secondary bevel
-no light reflecting

At this point the knife is very close to having an apex, but if you form a burr on this or other steels, especially with a coarse stone you might as well put on the Lord of the Rings, extended edition while you remove it.

-switch to a very friable waterstone, ~400 grit, lots of slurry
-grind the flat again, ~2 mins
-run the knife against my nail, check for visible impaction (none)
-the knife catches on the thumbnail, passes the 4-finger test

At this point I can set the apex, most people would consider it sharp, but leaving this knife with a ~2 dps apex is kind of pointless. I switch to a 600 grit DMT :

-rinse the stone, make sure it is wet
-I want barely no contact pressure and no friction (so lubricant)
-very light passes with the knife barely elevated, ~11 dps
-a few passes and check

The knife shaves with barely any contact force, it won't push cut light paper, but will cut on a 45 without a draw which is decent for a 600 grit finish on this knife made out of some low grade mystery steel.

Now to be clear, it won't have great edge retention here, the finish is too fine. If you want slicing edge retention with that kind of steel you need a really coarse finish. For reference :

[www.cliffstamp.com]

At the time, that was 3-5 times more rope cuts than people were doing with custom knives :

[sharpeningmadeeasy.com]

It was just to show the influence of angle/grit on edge retention was so much more than steel that IF you were willing to optimize those, you could get better performance out of a piece of mild steel than a knife in a super-duper-steel from a custom knifemaker.

That did not make me very popular as people kept saying things like I was advocating "junk" steels for knives. What I was saying was a little knowledge of geometry/grit was more important than people thought.

Now of course IF you have a high grade steel and do the same, you get the same kind of performance increase. I have a completely silly run where I took at D2 blade at 62 HRC at ~5 dps with an x-coarse finish and it basically cuts that much rope I got bored :

[www.cliffstamp.com]

I always wanted to repeat that, because I know I mangled the last run as you can see the huge jump, I know I got sloppy there and was pressing way to hard and fast, but after 1000+ cuts I just wanted it to end and the knife would not stop cutting.

I am fairly confident based on the performance up to then, looking at the data and extrapolating, I should have been able to get to 10, 000 cuts before the knife hit 20 lbs.

The edge at ~5 dps with that very coarse finish was kind of insane looking, it had massive "teeth" in the edge, and the teeth were that big that they had teeth on them.

To be clear, I was not the first person to do that work, Joe Talmage and Mike Swaim noted in the late 90's how a decrease in edge angle / grit finish made a huge difference in cutting ability AND edge retention, I just put numbers on it.

(note lowering the grit finish only helps cutting ability and edge retention IF you are slicing, it makes everything worse if you are push cutting)

(lowering the angle/thickness in general makes cutting/edge retention better in push cutting and slicing unless fracture of the material is a concern in which case at some point the performance reverses as you keep thinning)
Re: Knife Grinders -- What Edge Angle Is Good For SuperSteels
June 12, 2020 07:44PM
[www.bladeforums.com]

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"Gotta love living in 2019 baby, (63rc too soft on a production knife)"
--Shawn Houston
__
"I am still discussing issues of steels and performance at this stage."
--Cliff Stamp
__
"Cause geometry cuts, .....steel determines the level and the duration"
--Roman Landes
__
"But in general, I'm all about high performance, Ergos, safety. That's why I've been accused of 'designing in the dark' "
--Sal Glesser
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Jason D. Stone on YouTube
Re: Knife Grinders -- What Edge Angle Is Good For SuperSteels
June 13, 2020 06:11AM
The “SET test” does not appear to be testing “edge stability” or resistance to rolling. Results correlate very closely with expected wear resistance. See this study, for example: [knifegrinders.com.au]

Higher carbide and higher vanadium steels do better even at lower hardness.
cKc
Re: Knife Grinders -- What Edge Angle Is Good For SuperSteels
June 13, 2020 08:03AM
Quote
Larrin
The “SET test” does not appear to be testing “edge stability” or resistance to rolling. Results correlate very closely with expected wear resistance. See this study, for example: [knifegrinders.com.au]

Higher carbide and higher vanadium steels do better even at lower hardness.

but the claim is that this is what it does
Quote
link
Structural Edge Tester (SET) is a method and device developed by Edge On Up for testing edge
stability. In a nutshell, the edge is subjected to controlled rolling, the extent of which is quantified.
Edge sharpness tester used in the study: PT50A Industrial.


one of my main questions is the comment above that the edges are done differently and are a perfect 12dps no microbevel, yet they are being honed on a leather pasted strop. in my experience, it is literally impossible for this to not alter the apex. either it will become slightly higher angle convex, or thinner convex, but it wont stay at 12dps exactly any more than the light passing at a higher angle on a stone might do

I'm really curious about those laser angle measurement tools.. how much metal does the apex require at a given angle to be accurate?
if I had a 12dps bevel with a micro bevel formed by stripping only 14dps at say a few microns high... 5-6microns even.. will this be detected? or will it read as 12dps.. i don't know.. I'm curious though.

there was a comment on one of the tests that at 10dps the edges just failed terribly, but 12 is good.. but no information about this SET tester has determined for how much of the cross section has been damaged..

if 12 is good, but 10 is bad, but the damage is only for say 10 microns, then you could say, make a 12dps micro bevel for 10 microns, and the rest is 7-8,10 dps and get better overall performance.

i also wonder how the angle and weight of the SET roller has been determined, and how there is any indication that this weight has the same relevance to different steel compositions.

----------------------------------------------------------------------
It's not Cliff, its Dr Stamp
#kebabstickcut, it's a thing - make it happen
Re: Knife Grinders -- What Edge Angle Is Good For SuperSteels
June 13, 2020 01:57PM
Quote
Larrin

Higher carbide and higher vanadium steels do better even at lower hardness.

I am not sure that the data show anything significant at all, as :

-the scatter is very high
-there is no statistical analysis done which takes the noise/scatter into account
-they are dealing with nonlinear effects, they are not trivial to draw conclusions on and prone to error amplification

In some more detail, this is for the first knife :



Consider :

-the scatter in the readings is far greater than the difference between the two sharpening methods
-the run is stopped using a method that is insanely sensitive to random scatter

At multiple times the AO edge is better than the CBN/Diamond edge, and at 100, they test the same. Now if you look at the numbers graphically, it is more obvious that there is a large random influence :



You can NOT make a comparison on a nonlinear scale which is subject to high scatter because the nonlinear nature of the effect amplifies the scatter, this is obvious in the results :



That Elmax result should show the kind of wild deviation you can get when nonlinear dependencies hit high scatter (that's why you can't extrapolate from such graphs).

Now how do you actually try to make sense out of that data, well you have to use some kind of comparison which will do a running average of some kind to inherently reduce the scatter. Here is one such statistic :

TCE = 0.33 for the AO
TCE = 0.37 for the CBN/Diamond

The difference is 10%, and there is no way given the scatter in the data that could be argued to be significant, and this is for the highest Vanadium steel which is argued to show the strongest result.

(TCE is calculated by adding up pass count / average sharpness through the pass over the run)

Now when you have this statistic you ask yourself this question, lets assume (and this is a dangerous assumption) that what I am measuring is basically the effect on an edge through deformation in use, even if this is the case, considering :

-I am doing careful jigged sharpening
-decently skilled at sharpening
-carefully maintaining abrasives
-doing very controlled simulated cutting

etc. .

In actual use, by a random dude, what is the chance they will see a 10% decrease in force/bite on the edge during the lifetime of that blade before they sharpen?

I would also be very skeptical because :

-there is no blinding, hence you are very prone to experimental biases
-there is no correlation to user data, hence it isn't clear what is actually being measured
-there is no analysis of Roman's work which should be striking as it is isn't in agreement

All of this being said, it would not surprise me if a roller on an edge didn't cause significant wear, especially adhesive depending on the contact pressure and nature of the roller/edge. There are steels which are designed to have very low adhesive wear rates, I would be curious what would happen with them.

But at a minimum :

-blind the results
-repeat them 3-5 times to reduce the scatter and estimate ranges
-use a robust method to compare data sets which isn't sensitive to nonlinear error amplification
Re: Knife Grinders -- What Edge Angle Is Good For SuperSteels
June 14, 2020 05:05AM
I understand the point with blinding but in such case where a person tests a finished knife..
He always knows what it is before the testing.. once controlled testing method
isnt dumbproof and simple enough.. You cant just ask another random person
to sharpen it and test it..

I was thinking about this since we first time talked about testing of Pavol Sandor..

f.e. If I wanna see ht differences I make sample blades
with same stock thickness, primary grind angle and same thick bte
All I say is they are same steel with no further spec for ht etc..

1) So he shouldnt have a bias towards one of the samples relative to other ones from the comparison
2) I am not too intersted to compare that with other blades tested.
All I am looking for is different properties as result of ht from 3 or 4 samples..

That is about the furthest I could get with blinding in practice..

But I dont really see how ppl could blind test something unless test takes
too long and you cant recall anything from memory or something...

www.instagram.com/jscuttingtools
Re: Knife Grinders -- What Edge Angle Is Good For SuperSteels
June 14, 2020 05:47AM
I ve read over some Vadims papers longer ago and noticed strange manner to me..

He measured some differences between edges performace or sharpnesses
and made a conclusion/s / what was an actual cause of that without an evidence.

Or the categorization of steels (perhaps completely different alloys)
based on the wt%C content exclusively.. And based on his explanation
and measured values I still wouldnt see why that would make any sense or purpose..
Even his own measured results did not actually support that categorization..

www.instagram.com/jscuttingtools
Re: Knife Grinders -- What Edge Angle Is Good For SuperSteels
June 14, 2020 05:19PM
As an example of why you should blind test, take a look at this guy :

[www.youtube.com]

He seems like a decent guy, doesn't want to promote himself, just learning/experimenting. I watched a few of his videos and his steel performances just go all over the place [*] :

VG-10 - 2
8Cr13Mov - 8
S30V - 8
CTS-XHP - 24
S110V - 30

The numbers are the cuts on cardboard the knife has to make to lose shaving sharpness. But now what is telling is if you watch his video's you can see him :

-do some work, take a reading, note he thinks that reading is off as it is too high (120)
-take another reading, that comes out much lower, he thinks that is a good one and keeps it (70)

Now maybe you can see this is ridiculous - you can just force data to be what you expect, if you do you are just going to get what you expect regardless of what the measurements already show. Alex Steingraber is another guy who seems decent, but when he does comparisons he will often start out by saying things like - "we know what is going to happen" etc. .


[*] His results look like real data to me, that kind of wild scatter you can get easily if you have a sharpness test which is really low in precision and accuracy which is what he is using, and you extrapolate off of a nonlinear graph which is what he is doing
Re: Knife Grinders -- What Edge Angle Is Good For SuperSteels
June 14, 2020 05:40PM
Interesting comment from his latest video :

"No I'm not doing them anymore as the BESS system is not consistent across different users. Good idea to gauge sharpness and that is works well for. But it's a system that can vary with how people use it, So no good as a "standard" if your comparing numbers with other users (Which is kind of how I found that out)."

I was going to buy a BESS awhile ago just to compare it to what I normally do for that type of sharpness measurement (which costs $5) until I saw the price and the ridiculous over promotion. I have to give the guy credit though, he created a niche industry, excellent marketing skills and a hell of a lot of hard work.
Re: Knife Grinders -- What Edge Angle Is Good For SuperSteels
June 14, 2020 05:42PM
Cliff,
This is what I find myself doing in cutting tests, even taking measurements. It makes me uncomfortable, I really do not like it and I am not sure why it happens.

------------------------------------------------------------------------------------------------------------------------------------------------------
"Gotta love living in 2019 baby, (63rc too soft on a production knife)"
--Shawn Houston
__
"I am still discussing issues of steels and performance at this stage."
--Cliff Stamp
__
"Cause geometry cuts, .....steel determines the level and the duration"
--Roman Landes
__
"But in general, I'm all about high performance, Ergos, safety. That's why I've been accused of 'designing in the dark' "
--Sal Glesser
------------------------------------------------------------------------------------------------------------------------------------------------------
StoneSharpEdges

Jason D. Stone on YouTube
Re: Knife Grinders -- What Edge Angle Is Good For SuperSteels
June 14, 2020 05:44PM
Cliff,
A lot of people have the BESS sharpness testers, maybe you could borrow one. I also wanted to see how my sharpness tester I made compared number wise to the BESS.

------------------------------------------------------------------------------------------------------------------------------------------------------
"Gotta love living in 2019 baby, (63rc too soft on a production knife)"
--Shawn Houston
__
"I am still discussing issues of steels and performance at this stage."
--Cliff Stamp
__
"Cause geometry cuts, .....steel determines the level and the duration"
--Roman Landes
__
"But in general, I'm all about high performance, Ergos, safety. That's why I've been accused of 'designing in the dark' "
--Sal Glesser
------------------------------------------------------------------------------------------------------------------------------------------------------
StoneSharpEdges

Jason D. Stone on YouTube
Re: Knife Grinders -- What Edge Angle Is Good For SuperSteels
June 14, 2020 06:24PM
Shipping to and from would be comparable to just buying one, I am in no rush and it is far down on my list of priorities.

Quote

This is what I find myself doing in cutting tests, even taking measurements. It makes me uncomfortable, I really do not like it and I am not sure why it happens.

Data collection is supposed to be like that, everything that can go wrong does, and when everything goes right and smooth, it usually means you are just making up numbers. I mean there is a reason why we have huge industries and ISO standards, these things are difficult to get right and very easy to just end up misleading yourself.
Re: Knife Grinders -- What Edge Angle Is Good For SuperSteels
June 15, 2020 03:02AM
Quote
CliffStamp
Shipping to and from would be comparable to just buying one, I am in no rush and it is far down on my list of priorities.

Since I ve talked to Pavol (he has one, but consider it the least accurate/reliable method)
and played with bess for a while, criticize it quite often..

There quickly became a trend that if you are bess testing as a sharpener you do it better.
You are more credible.
Its like a gizmo that all would walk around with amazement perhpaps they dedicated
so much thinking to the actual test method as a cat passing by on your table..

More ppl now openly admit that bess numbers arent comparable between the users..
perhaps I clearly remember the initial marketing which claimed it to be
the standardised method that will allow comparisons from user to user.

www.instagram.com/jscuttingtools
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