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Edge retention with different grit finishes on 3Cr13 stainless

Posted by CliffStamp 
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Re: Edge retention with different grit finishes on 3Cr13 stainless
November 02, 2014 04:33PM
Interesting update - Henckels 3000 waterstone :

-very fine stone
-hard binder
-abrasive is not friable
-splash and go

These properties (strong binder + nonfriable traditional abrasive) results in a very slow cutting stone, but considering the general steel/hardness that Henckels uses it makes sense as a weaker binder and more friable abrasive would be over kill for 5C13 type steels and simply produce a stone that wore excessively.

Now sharpening with this is a bit interesting, if I use the standard method :

-set the edge with the 320 Suehiro 'Chemical'
-micro-bevel with the finishing stone

then the edge will not form at the finish of the Henckels 3000, it looks like this :



+



The reason this happens is that this stone is so slow cutting that it simply doesn't remove enough metal in generating the micro-bevel to remove the coarse scratches and when the edge is apexed those coarse scratches and the fractures around them will generate those little chips in the edge.

In order to get an apex which represents the finish of the 3000 Henckels then you have to make sure there are no coarse scratches left and this means that you pretty much have to over grind with a stone similar to the Naniwa Superstone 400 which doesn't produce jagged scratch lines. Now why do you have to over grind? Because this stone (3000 Henckels) is so slow cutting that if you don't form an apex with the shaping stone then you will take forever to cut it with this stone. However when you over grind on steels like this one (soft, less than ideal hardening) you often get a pretty ragged burr even on stones which generally won't do it. This is off a King 1000 which was even fairly muddy :




+



Now that looks like it is even worse, but all that jagged bit along the apex is just over ground and the Henckels will cut it off immediately and produce this :



The edge retention performance is a bit interesting :



and I produced a scaled graph of the TCE alone :



Watch how the behavior goes to a minimum and starts to increase again. At this stage I am not confident that is real, there is simply not enough data behind it, however it would make sense that it does that from even basic experience in cutting things. If you take how the performance decreases from the 120 Sigma Power down it can't do this in a linear manner forever as that would predict if you used an ultra-fine finish (sub-micron) the edge retention would be essentially zero.

I expected this to happen because the blunting itself starts to change in basic fundamentals with the ultra-high polishes because they simply don't cut the same. If you take the edge off the 3000 Henckels and start to cut the rope then as you press into the rope it will just sink right through it. It takes little effort to pull it along and little benefit to doing it, the blade won't go any further into the rope. It is starting to become a push cut even if you try to draw. With the 120 Sigma Power the cutting mechanic is almost the exact opposite.

With the very coarse finish if you try to push hard then nothing happens, the blade just binds and the force has to be really ramped up to complete the cut, but as you draw it (which takes a little force horizontally) then the blade cuts the rope between the teeth and starts to then drop into the rope and the cycle continues. With the ultra-fine polishes there is essentially no rope in between the teeth and thus there is little benefit from the draw and thus the way it cuts and blunts is very different.

Now here is a curious question, what happens at the ultra fine finishes, do they rebound as strongly up as the 120 Sigma Power (I don't think so) or will they stabilize at a lower level, but still far higher than what you would expect given the behavior of the more coarse stones (likely this option). However again I don't have enough data at this stage to say anything definite, but still it is interesting.

The other thing I will say is that if you look at not simply the edge retention in slicing alone, but this :

(TCE in slicing) * (TCE in push cuts)

Then that represents a kind of average edge retention in a mix of slicing and push cutting and if you were to do that I suspect that the ideal finishes may be towards the fine side of the spectrum. Now you might ask well why not do this instead :

(TCE in slicing) + (TCE in push cuts)

The reason is because a multiplication average is more representative when an extreme event, even if infrequent basically dominates. Consider these two finishes :

a) TCE of 10 on slicing, TCE of 1 on push cuts

b) TCE of 5 on slicing, TCE of 6 on push cuts

They both have the same + type average (5.5) but the multiplication average is very different :

a) 10 * 1 = 10
b) 5 * 6 = 30

If you use the (a) one for a mix of slicing and push cutting you find it will go dull very fast because even a tiny amount of push cuts makes it completely dull. However (b) works very well on either and thus for a general purpose edge it works much better. Hence why an edge retention average for a general purpose knife should be of the multiplication type of average.

--

I also did a few runs with the 600 DMT and added that, nothing surprising there, medium coarse edge, very trivial to set / refine the apex.
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 02, 2014 08:44PM
Quote
CliffStamp

If you use the (a) one for a mix of slicing and push cutting you find it will go dull very fast because even a tiny amount of push cuts makes it completely dull. However (b) works very well on either and thus for a general purpose edge it works much better. Hence why an edge retention average for a general purpose knife should be of the multiplication type of average.
.

I'm really looking forward to this work. My own preference tends to be for highly polished edges on my knives, so I'm both extremely curious as to how large the rebound will be and where the best combination of slicing vs. push cutting can be obtained.

One question I have as you get into the very fine stones is whether you plan to keep using the fine stones by themselves to set the micro-bevel? I use a Spyderco M-F-UF progression on my micro-bevels because I believed that the UF would be too fine for setting a micro-bevel on its own (even though I usually highly refine my apex through a stone progression before applying the micro-bevel).
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 03, 2014 01:31AM
Quote
Steel_Drake

One question I have as you get into the very fine stones is whether you plan to keep using the fine stones by themselves to set the micro-bevel?

I would like to, but without using a jig it isn't practical. This is an attempt to skip a lot of grits and produce a 8000 Henckels edge :



There is still too much of the lower grit finish remaining. In order to get this :



Which is decently close to the pure apex of a 8000 Henckels I have to do similar to :

-Suehiro 'Chemical', edge bevel
-King 1000, very muddy, edge bevel
-Naniwa Aotoshi 2000 or Henckels 3000, half way between the edge and micro-bevel angle

If I was jigging the angle control would be much higher and thus it would be possible to skip grits. Plus in practical use where you are not trying to actually measure the "pure" 8000-Henckels edge then you can be much simpler.

This stone is basically the same as the 3000 just a finer grade so it is really only suitable for easy to grind steels, it won't even cut steels like M4/10V at all, they just slide on it like glass.

Here is the worn edge :



very easy to restore to a high sharpness, it responds very well to steeling, the ultra-coarse edges, not so much as by the time they really do there is a lot of actual damage to the edge.



I am getting the hang of setting the apex with these waterstones and looking forward to trying the Bester and Suehiro again to see if I can get them to decent sharpness. I also don't think that result with the 8000 Henckels is optimal, I just don't like the way that stone cuts, it is very slippery and lacks abrasion, even on this easy to grind steel.

--

As an aside, if I could sharpen them at the same speed, I would vastly prefer the ~1 micron edge to the 25 micron edge, the only thing is now it takes me more than 10X as long. But of course again for just normal use you don't really care if there is a bit of low grit finish left on the edge.
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 03, 2014 01:53AM
Quote
CliffStamp
As an aside, if I could sharpen them at the same speed, I would vastly prefer the ~1 micron edge to the 25 micron edge, the only thing is now it takes me more than 10X as long. But of course again for just normal use you don't really care if there is a bit of low grit finish left on the edge.

Why is that? Would you not miss the edge retention from the increased coarseness in day to day use?

_______________________________________________________________________________________________

Always in search of a good choppa'
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 03, 2014 02:17AM
Quote
CliffStamp
As an aside, if I could sharpen them at the same speed, I would vastly prefer the ~1 micron edge to the 25 micron edge, the only thing is now it takes me more than 10X as long. But of course again for just normal use you don't really care if there is a bit of low grit finish left on the edge.

Well, outside of this particular set of comparisons, it shouldn't take that much longer to achieve a ~1 micron polish edge given that you can use a stone progression and avoid waterstones. It takes me about 5 minutes to re-apex through a DMT XC, DMT F, Spyderco M, F, UF progression and well under 5 minutes to set the micro-bevel on a Spyderco M, F, UF progression. Certainly this is much slower than how fast you, specifically, can set a coarser edge, but it isn't that long. I guess the question is how long is too long in your eyes?
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 03, 2014 02:04PM
Quote
Steel_Drake

Well, outside of this particular set of comparisons, it shouldn't take that much longer to achieve a ~1 micron polish edge given that you can use a stone progression and avoid waterstones.

It is going to depend on the knife/geometry, but in any case it is going to be multiple times as long. At a base level you are looking at something similar to for a basic steel :

-320 Suehiro 'Chemical', 30s to 1 minute, edge
-600 DMT, 5-10 s, apex

The micro-bevel time is instant, and there is only one stone for maintenance. The total time is ~30 second to a minute. For a low grindability steel this can easily double.

Now if you jig sharpen then you can just start layering this, but if you don't you can easily run into layered bevels and if you don't err on the side of increasing angle then the time/passes will increase dramatically. At a minimum on a basic knife I would be doing something like :

-320 Suehiro 'Chemical', 30s to 1 minute, edge
-400 Naniwa Superstone, 30 s, edge
-1000 King, 30 s, edge
-2000 Naniwa Aotoshi, 30 s, edge
-3000 Henckels, 60 s, edge
-8000 Henckels, 60 s, apex

This is five times as long and requires soaking/maintenance of six stones, many of which are soakers and they all have to be kept very flat or else the bevels won't over lay properly. If you look at steels with a low grindability this can push the time to 10-15 minutes.

Now of course you can just do this :

-320 Suehiro 'Chemical', 30s to 1 minute, edge
-MXF DMT, 10 -20 s, apex

Which is very close and will basically have 60-80% of the edge at the finish of the DMT with the remaining having some hold over from the Suehiro.
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 03, 2014 02:13PM
Quote
C Amber

Why is that?

The cutting ability in general tends to be higher even on slicing work. On the 1/2 hemp for example, while both apexes will make a cut with 4-5 lbs, the one with the very high polish has practically no horizontal component. In extreme contrast, you can readily feel the force required to pull the 120 Sigma Power through the cord. This is one of the nagging reasons I don't really like the way I currently measure slicing sharpness or cutting ability as it ignores that component of the force. However in general it is always going to be less than the vertical component so it is a small correction generally, especially for worn edges.

The reason most people think this isn't true and polished edges don't cut well on slicing is that all the polished edges they have seen have no slicing aggression, you can slide your finger along them without harm. Note the guy selling traditional slip joints who even opened the blade by pressing his thumb against the apex and when I commented on it in his YT video he noted the knife in question was among the sharpest of modern manufactured blades. The entire perception of performance has been warped by the over use of buffing.

Quote

Would you not miss the edge retention from the increased coarseness in day to day use?

Consider this :

-3Cr13, < 55 HRC, still does ~50 cuts in 1/2" hemp with a two inch draw and slices newsprint

In general, it isn't common for me to do that much of that style of cutting in a day unless I am doing something specific to that, some kind of reno/gardening project. In general most kitchen work benefits from a high polish for peeling, chopping and most paring and similar for a lot of utility work (paper, string, plastics) and then all wood work as well.
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 03, 2014 03:46PM
For reference, just take a scan through these :

-[www.bladeforums.com]

-[www.kitchenknifeforums.com]

-[www.ar15.com]

-[forums.scrapyardknives.com]

-[www.spyderco.com]

In short, the claims made vary significantly and you can find complete opposite and contradictory claims being made. These are in general all due to the same two basics problems :

-people are not being descriptive enough about what they mean

There is a large difference between push cutting and slicing, and initial cutting performance and edge retention for example.

-they are using not properly sharpened knives

When people say things like "Well the coarse edge doesn't shave, but it is sharp." or "The polished edge doesn't bite into rope but it is sharp." they are just using poorly sharpened blades in both cases.

This is the real problem when you try to figure things out by that kind of general polling because of the tendency of most people to refuse to say they don't know and be vastly over confident in their perspectives based on very limited use.
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 03, 2014 04:38PM
Quote
CliffStamp
The reason most people think this isn't true and polished edges don't cut well on slicing is that all the polished edges they have seen have no slicing aggression, you can slide your finger along them without harm. Note the guy selling traditional slip joints who even opened the blade by pressing his thumb against the apex and when I commented on it in his YT video he noted the knife in question was among the sharpest of modern manufactured blades. The entire perception of performance has been warped by the over use of buffing.

I am not sure I am understanding you Cliff... are you saying that a 10k grit stone finished edge will have equal cutting aggression/ability as a 1k diamond stone? The 10k waterstone edge is MUUUCH less agressive than a 1k diamond and is much less efficient at most everything in my experience, except for shaving or something requiring push cutting.
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 03, 2014 04:39PM
Quote
CliffStamp
Now of course you can just do this :

-320 Suehiro 'Chemical', 30s to 1 minute, edge
-MXF DMT, 10 -20 s, apex

Which is very close and will basically have 60-80% of the edge at the finish of the DMT with the remaining having some hold over from the Suehiro.

So basically, as I suspected, the issue is that it takes more than 2 minutes (even if only 3 minutes more)! This makes me laugh because I only wish I could use solid benchstones as quickly as you can use wetstones.

Quote

There is a large difference between push cutting and slicing, and initial cutting performance and edge retention for example.

This is something I'm really hoping to see you do some testing on eventually, there are a whole bunch of questions I'd like to see data on in this area since it would be of practical relevance for me:

1) Influence of highly-polished edges on push-cutting edge retention and cuttting performance, and if there any significant comparative differences in push-cutting edge-retention between steels (in particular, if and to what extent finer-grained steels outperform less fine-grained steels).

2) How much of an influence, if any, does how fine-grained a steel is have on obtainable initial push-cutting sharpness. This one in particular has been on my mind recently since, anecdotally, I'm seeing similar initial push-cutting performance on Spyderco 8Cr13Mov and Spyderco Aogami Super in similar geometries.

3) Push cutting edge-retention vs. slicing edge-retention (i.e. am I better off push cutting through cardboard or slicing given a highly-polished edge finish)?

Now obviously, I hardly expect you to shift the balance of your knife testing work to satisfying my personal curiosities that I'm too lazy to try and test for myself, however I do think testing some of these questions certainly bears on whether fine-grained steels significantly outperform others in these kinds of applications, and to what extent that is true, which goes to a lot of what you have been saying for some time.
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 03, 2014 04:52PM
Quote
razoredgeknives
... are you saying that a 10k grit stone finished edge will have equal cutting aggression/ability as a 1k diamond stone?

Essentially yes, though in many cases it may dull faster.

I would suggest this simple experiment :

-take a piece of 1/2 hemp (or any rope)
-sharpen with a coarse edge
-measure the lowest force you can apply and cut the rope with a 2" draw

Now if you sharpen to a high polish that force should not increase, in fact it should decrease slightly and the cutting mechanics will change because as soon as you press on the knife it will smoothly sink right into the rope but a coarse edge will bind strongly at pretty much the depth of the teeth it has.

I looked at this in detail years ago with the South Fork, look at the sharpening section here :

- [www.cliffstamp.com]

If you have to apply more force, if the polished edge slips on the rope, it simply isn't sharp. A lot of them are not, for example look at the video I did on the XM-18 from Hinderer. It had a fully polished edge and it was very dull, but they don't have to be that way.



Edited 1 time(s). Last edit at 11/03/2014 04:53PM by CliffStamp.
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 03, 2014 05:43PM
Quote
CliffStamp
For reference, just take a scan through these :

-[www.bladeforums.com]

-[www.kitchenknifeforums.com]

-[www.ar15.com]

-[forums.scrapyardknives.com]

-[www.spyderco.com]

In short, the claims made vary significantly and you can find complete opposite and contradictory claims being made. These are in general all due to the same two basics problems :

-people are not being descriptive enough about what they mean

There is a large difference between push cutting and slicing, and initial cutting performance and edge retention for example.

-they are using not properly sharpened knives

When people say things like "Well the coarse edge doesn't shave, but it is sharp." or "The polished edge doesn't bite into rope but it is sharp." they are just using poorly sharpened blades in both cases.

This is the real problem when you try to figure things out by that kind of general polling because of the tendency of most people to refuse to say they don't know and be vastly over confident in their perspectives based on very limited use.

Good references. Thank you

I wasn't actually questioning a polished edge being sharp though...I was just curious, based on your recent experimentation why you would want to give up the edge retention of the coarser edge. However, I was under the mistaken assumption that you did more abrasive cutting on a regular basis, which you clarified you do not in the answer to my orignal question.

_______________________________________________________________________________________________

Always in search of a good choppa'
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 03, 2014 05:58PM
I was just posting them as a general reference rather than a specific answer.

I do a lot of abrasive cutting, but even there the initial performance will be higher with the polished edge, and it takes a long time before the knife gets dull. The interesting thing is that if you look at the finish I normally use (600 DMT) it isn't that much higher than the ultra-polish, but the DMT is dominated by the 120 Sigma.

Again now, to be clear some of these data points only have two runs. At this stage this is more for dicussion, you really can't make any kind of stone vs stone until they all have at least 3-5 runs which they may never have as this is more of a "what is the general pattern" type of work vs "what is the performance of a particular stone".
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 03, 2014 07:22PM
Here is an obvious question - when (if) I repeat this with push cutting, the push cuts only dull a 1/2" section of edge, the slices currently dull 2". I can do four push cuts for the same length of edge. If you look at the 8000 grit hemp cuts which are starting to be a push almost and multiply it by 4 then it maybe counters the "low grit = higher edge retention" argument if you look at just doing push cuts on different sections of edge and adding them all up.
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 03, 2014 07:57PM
Quote
razoredgeknives
are you saying that a 10k grit stone finished edge will have equal cutting aggression/ability as a 1k diamond stone?

This is directly born out in the graphs, right (assuming "aggression" refers to slicing sharpness)? The sharpness trend does not decrease as grit finish increases, and in many cases increases (the sharpness reported in these graphs is slicing sharpness, correct?).

Here's a video of very high push-cutting ability:

[youtu.be]

I think it's pretty clear from that why a very good push-cutter can slice as well as a coarse edge.
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 03, 2014 09:32PM
Quote
CliffStamp
Here is an obvious question - when (if) I repeat this with push cutting, the push cuts only dull a 1/2" section of edge, the slices currently dull 2". I can do four push cuts for the same length of edge. If you look at the 8000 grit hemp cuts which are starting to be a push almost and multiply it by 4 then it maybe counters the "low grit = higher edge retention" argument if you look at just doing push cuts on different sections of edge and adding them all up.

That's a very interesting idea.

Now when we say a coarse edge would have lower edge retention in push cutting, are we assuming that the teeth will break down more quickly on a push and thus dull more quickly? Seems hard to believe it would substantially break down on soft materials like hemp on a push. Conversely does this mean the even worn edge of a polished edge will cut longer on a push just like the jagged worn edge of the coarse edge will on a slice?

Or are we assuming a coarse edge will simply start from a lower standard of push cutting sharpeness and so automatically be at that low end cut forever range of sharpness?

Sorry, your comment got me thinking something, but I can't put my finger on it. I'm not sure what it is.

_______________________________________________________________________________________________

Always in search of a good choppa'
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 03, 2014 11:42PM
Quote
CliffStamp
-take a piece of 1/2 hemp (or any rope)
-sharpen with a coarse edge
-measure the lowest force you can apply and cut the rope with a 2" draw

how to I measure the force? I do have a postal scale...

I am wondering how it affects the edge on steeper angles (your test was on 9-11 dps)... I know the polished edge is maximized on efficiency on low angles... will be interesting
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 04, 2014 12:25AM
Quote
CliffStamp

[...]
I am getting the hang of setting the apex with these waterstones and looking forward to trying the Bester and Suehiro again to see if I can get them to decent sharpness.

Ok, I can do it but is is just stupid/silly, what you have to do is something like this :

-get the stone really wet and then spray to flush off loose grit
-tilt the stone to let everything drip off
-let the stone dry and then sharpen with it just at the point it has a minimum amount of water

The ideal state is just enough to let the stone cut freely but not form swarf. If I do this than most of the edge can be very sharp like the edge off the 600 DMT but it only takes a little of that coarse slurry to grate along the edge and reduce the sharpness to ~25 %. This may be why Carter advocates edge trailing method for his final passes. I don't like that though for the tendency to create a burr however it should eliminate the slurry grating against the edge problem which John Juranitch alway argued was problematic hence he argued for dry honing.

Quote
razoredgeknives

how to I measure the force? I do have a postal scale...

A bathroom scale would be enough, a postal scale would be more precise but you want one which can stand fairly high weights.

Quote
C Amber

Now when we say a coarse edge would have lower edge retention in push cutting, are we assuming that the teeth will break down more quickly on a push and thus dull more quickly? Seems hard to believe it would substantially break down on soft materials like hemp on a push.

I have not done extended/detailed push cutting trials on hemp with coarse edges as they perform poorly initially. I have done them on wood though. While hemp is soft/weak it is easily possible for thick hemp to be stronger than thin steel. For example if you grind a very thin knife down to zero and it has a low angle, say 1.5 dps you can break the edge right off trying to cut hemp. The "teeth" on a coarse edge at a low angle are very thin at the base, ~5 microns or so thick. It isn't unreasonable they could bend that that thickness when the force is all compressive, on a slice the forces are much lower. It may be the case though that the very coarse edges are actually thick enough at the base of the teeth to resist being deformed and that the maximum rate of deformation, or worse rate of wear would be at some medium finish.

Quote

Conversely does this mean the even worn edge of a polished edge will cut longer on a push just like the jagged worn edge of the coarse edge will on a slice?

I am not sure what you mean by worn here, at some point the polished edge will blunt so much it will no longer be as push cutting sharp as the coarse edge is initially.

Quote

Or are we assuming a coarse edge will simply start from a lower standard of push cutting sharpeness and so automatically be at that low end cut forever range of sharpness?

This will be true, it will have no where near the push cutting sharpness, you can even see it on wood. I guarantee no matter how sharp you set a plane blade with a 100 grit stone Mark would immediately be able to tell it apart from a polished edge as soon as he tried to use it and he would even be able to tell from the surface of the wood if you used it.
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 04, 2014 02:23AM
I have been playing around with some of the fine finishes and prep and the secret to minimizing the work is basically this :



You have to use the stones really muddy not so much to increase the speed of grinding against the sides of the edge, but once you have the coarse shaping done you want that mud to keep the apex line free of irregularity and as crisp and straight as you can.

This steel is a bit problematic as it tends to form small burrs even with a muddy stone, just take a look at the little bits which hang on the edge even with a very muddy 3000-Henckels :



However they don't really matter because the micro-bevel with the 8000-Henckels will cut that off, the main thing is to keep the apex line crisp/straight and so once the shaping is done, keep the stone pretty muddy.

Interestingly enough this doesn't produce a very sharp apex, even off the 3000-henckels it does a newsprint push cut at just 1/4" from the point of hold.
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 04, 2014 10:37PM
On an amusing note this is the most high polish work I have done in a long time and I can readily see now why people get so fond of those edges. If I didn't use my knives as often/frequent as I do, or I enjoyed sharpening in and of itself, or I could put that edge on much faster - well I would likely use it.

I did another couple of runs with the 8000-henckels and the edge was easily carving hair, and then a little more work and it would cleanly just cut a hair pressed against an edge, this is long past arm shaving or even push cutting newsprint. With this edge the knife just falls through rope, cardboard, foods, and you really don't want to try to do any kind of skin contact as it just goes right into it as it will easily push cut a tomato.

This steel doesn't tend to hold that high sharpness very long though, but still if you only do a little work, and it isn't like it goes duller faster on the low sharpness levels.

--

I tried a few experiments to see if I could get there faster or reduce the part which requires any attention. One method was to bring the edge bevel right up to 3000-Henckels and then just micro-bevel with the 8000-henckels. This doesn't reduce the total time, but the edge work is just shaping, I don't really pay attention to it and it can be done (and should be) with a very muddy stone. This is the most efficient from a focused-time perspective but I discovered that if I just micro-bevel with the 8000-henckels and ironically do a really good job then the edge is prone to premature collapse.

If I do the first few passes, say 10-20 perfectly then the knife can have the micro-bevel ready to go off of the 8000-henckels. I figured out how to do that as noted in the above by finding the exact balance of wetness on the stone. But the problem is with that few passes the micro-bevel is too small as the abrasion of this stone is so weak and it leaves is literally microns thick and it can just crack off because you are essentially cutting the hemp with the edge bevel.

I found that I need about 50-100 passes on this stone to generate a micro-bevel wide enough so that it won't just crack off (20 microns deep, so about 10 microns thick). Now that is a lot of passes so it is more efficient to do something like :

-Suehiro 'Chemical' + Naniwa Aotoshi + 1000 King + 2000 Naniwa Aotoshi

all on the edge bevel and then switch to :

-3000-henckels + 8000-henckels on the micro-bevel

The 3000 cuts fast enough so that 20-30 passes here allows 20-30 passes on the 8000 and the micro-bevel is now stable.

--

For practical purposes, it is hard to argue this is useful because of the much more massive time + number of stones but a lot of people like sharpening. However for just use / function, this gets very close to the push cutting (aside from extremes) and is much faster :

-Suehiro 'Chemical' + 1000 King, on the edge
-MXF DMT, micro-bevel

If the steel starts to get really low grindability then you may have to insert other stones or use a better inbetween than the King 1000.
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 05, 2014 09:09PM
Quote
CliffStamp


This steel doesn't tend to hold that high sharpness very long though, but still if you only do a little work, and it isn't like it goes duller faster on the low sharpness levels.
.
so what steel would hold that high sharpness? your research has shown Rex121, S35V, HAP40 and other high alloy steels have too coarse a carbide structure to get this sharp.
for stainless would AEB-L or 13C26 be good candidates? i can't heat treat them currently as my kiln does not get hot enough.
for plain steel, maybe O1, O2, 1.2519 or 52100? 1095 might work, but other forums have discussed issues with the steel batch to batch and from different sources. the sacred Blue or White steels are hard to find, expensive, and usually used as a sliver sandwiched between wrought iron or stainless. the O2 i have is basically 1095 with 1.5%manganese and 0.3%moly.
i have ten or so blades(4 each of O1 and 1.2519, 2 of O2) almost ready for heat treat and am looking for some guidelines. my idea would be 15 to 20 degree total angle, grind to 220 before hardening, harden and temper to Rc62-64, wet grind to 400 or so post heat treat, then start the stones? my finest stone is 750, could i then continue with 1000 then 2000 grit wet/dry paper? any and all suggestions welcome. no "Pictures at 11", but should have them done by monday.
scott
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 05, 2014 09:57PM
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oldsailorsknives

..
O1, O2, 1.2519 or 52100?

Yes, pretty much exactly.
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 06, 2014 07:48PM
as an interesting test, do you think the difference between say the 120 power sigma and the 2000 Atoshi to make 3Cr13 have better edge retention (for this kind of work) than say... M4 or S30V?

Actually I wonder how far you can go with that comparisson? Just to be able to put the 3Cr13 at a much lower edge angle and coarser finish and claim that "All high carbide steel promotion is crap! Look, no name chinese 3Cr13 has better edge retention! WHAT THE KNIFE COMPANIES DON'T WANT YOU TO KNOW!!!"

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Coffee and Blood
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 06, 2014 10:17PM
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Shurdi3
as an interesting test, do you think the difference between say the 120 power sigma and the 2000 Atoshi to make 3Cr13 have better edge retention (for this kind of work) than say... M4 or S30V?

Easily, the grit alone is enough to make much more of a difference than steels.

As loose rules :

-if you pick a steel like VG-10 and you go up/down by 2:1 you cover steels from 420j2 to 490V

However grit and apex angle easily make 10:1 differences themselves.
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 07, 2014 03:00AM
I am starting some data collection on the push cuts but there are a few immediate problems and the main one is the cutting ability is really different.

Slicing is WAY easier than push cutting, so much so it becomes really obvious that push cutting, especially with coarse finishes is kind of really stupid. As one example, with the same stone, same finish, same angle, same semi-blunt state :

-2" draw, makes a cut in 10-15 lbs

-straight push, makes a cut in 50-60 lbs

In a really blunt state :

-2" draw, makes a cut in 15-20 lbs

-straight push, not practical at all in any sense of the word

This difference is so dramatic that for example with the no name coarse stone I can do a slice at the end of a run when the knife is really blunt with less force than I can do a push cut when the knife fully sharpened. It is only going to get worse at the more coarse finishes.

I am not sure really how to meld the two charts because of the massive difference in cutting ability. The problem is when the edge is at a coarse finish or polished one, both of them when sharp make a slice with about 4-5 lbs and both of them when dull make a slice with < 20 lbs. However the coarse edges have a really low push cutting sharpness and so the push cutting ability is really low and thus it isn't obvious what kind of statistic best represents it in a meaningful manner.

The one thing which is obvious is that a very polished edge can still slice well (if not for as long), but a coarse edge can't push cut well at all and thus if you are doing any kind of mix of the two you are going to prefer a very fine finish. Now before anyone starts saying all hail high finishes, Boye (and others like Swaim) argued that in general it is usually more efficient to slice and in many cases this is true so this comparison is maybe a moot point.
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 07, 2014 10:33AM
That makes a lot of sense. I can get "cut" a cardboard box with a butter knife if I slice away at it long enough, but if I try to push cut it, it just smashes.

As for representing it, it seems a line graph, showing initial force and how it changes over time would make the point. If you put sharpness on the x and volume cut on the why, the very short lines from the coarse stones would be pretty clear, no?

Sorry, I don't even know if that makes sense, my description that is. And even if it does it doesn't really combine the two sets of information well.

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Always in search of a good choppa'
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 07, 2014 01:52PM
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C Amber

[...]
And even if it does it doesn't really combine the two sets of information well.

The basic problem is a bit mathematical. I will get a few more measurements as I think for now it is a matter of scale/units.
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 07, 2014 06:17PM
My question is why are you doing push cutting on rope? That's just bound to get you frustrated.

Though are there really any good alternatives for when you're measuring the forces used? Hard stuff like plastics and cardboard depend on the angle at which you cut, and you'll always have some variance there, and wood is way too inconsistent to have a proper look

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Coffee and Blood
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 07, 2014 06:20PM
Gotcha. Sometimes I just feel bad not really contributing anything, so I tried to, lol.

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Always in search of a good choppa'
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 07, 2014 06:45PM
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Shurdi3
My question is why are you doing push cutting on rope?

A number of reasons, I am curious as to what way the totals will combine and I want to look at the edge retention in coarse vs very high polishes and at some point I want to look at the apex influence again because I think it might reverse in push cutting (higher apex angles give better edge retention).

Note there is a popular argument being made now, Jim created it but others are starting to circulate it that the reason that Busse and Fikes could do push cuts with simple steels is because push cutting is very easy on a knife edge vs slicing. This is completely contrary to actual science and is argued for no other reason than Jim and others argued for years that ~100 cuts on small ropes was a sign of high edge retention and when it was noted that Fikes and Busse could do ~1000 cuts on larger ropes then they suddenly had super steels being outperformed by 1084.

The reality is that all that is being seen is the influence of :

-geometry
-edge finish
-nonlinear nature of blunting

Hence why Boye could do 3000 slicing cuts on 1" ropes with 440C with a blade well ground/sharpened to do it and be willing to cut with a not very sharp knife.

Quote

Though are there really any good alternatives for when you're measuring the forces used?

Materials? The main thing you have to keep in mind is cost and waste. It isn't at all sensible to suggest a material when generating a chart like the above costs $1000 and produces a pile of garbage. I use recycled materials which are either going to a landfill already or for which I can put to some other use.