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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 22, 2014 01:01AM
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C Amber
You are a tease...what is rolling a critical?

I dice roll almost all of the standard cutting I do to add elements of surprise/reward to it, it keeps it from getting boring. A critical changes depending on what rules, but usually is the maximum of a large sided die, often it is a 20, so it is a 5%.


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Is it possible those "teeth" would be more fragile in a negative way at a lower angle?

Yes, I doubt that a random choice of 15 dps hit the optimal peak though.


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Could one not still argue that a HCV steel would still do better ...

Yes, but I would make a few points :

-will you sharpen that kind of knife in that manner

I mean can you imagine the reactions if I suggested sharpening the K2/Farid with a 36 grit belt glued to a piece of hardwood flooring.

-is it a practical benefit

When is the last time you did ~2000 cuts into new hemp or similar clean material. It is similar to large knives and blunting on wood, it is trivial to get enough edge retention that almost always blunts on accidental impacts long before then.


and :

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Although of course they couldn't take advantage of the low apex angle like this steel could.

Indeed.
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 22, 2014 11:51AM
Thank you for the explanation on the die.

And good points on the other questions. I was just mainly curious. And in particular, when asking about the HCV steels, I was just thinking it is the kind of argument fans would resort too, even though as you point out, the improvement is likely impractical in real world terms.

_______________________________________________________________________________________________

Always in search of a good choppa'
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 22, 2014 05:33PM
Doesn't a steel like this tend to wear much smoother than High Carbon Vanadium steels? Isn't it possible if you used say... S35VN or similar relatively high carbon vanadium steel, to a point where the peaks on the "serrations" wouldn't wear smoothly, but instead you'd have chipping to make mini "teeth" going on the peaks? You'd essentially be having micro serrations on the mini serrations that are caused by the 36 grit belt

_______________
Coffee and Blood
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 22, 2014 06:29PM
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Shurdi3
Doesn't a steel like this tend to wear much smoother than High Carbon Vanadium steels?

Yes, especially if it has a high polish.

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Isn't it possible if you used say... S35VN or similar relatively high carbon vanadium steel, to a point where the peaks on the "serrations" wouldn't wear smoothly, but instead you'd have chipping to make mini "teeth" going on the peaks?

Possibly, and likely the teeth wear would itself be significantly reduced. The only argument I would make is one of practical advantage. It is fairly easy to check though, all I would have to do is just do the same thing with the Farid/K2 and see what would happen. The problem is just one of time/cost to check. I should be getting some used fishing line shortly, if I get it I will likely try a few similar runs.
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 23, 2014 01:55AM
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jasonstone20
Maybe these results, with a cheaper, softer knife/steel, is showing the sorce of the idea that you can get you knife 'too sharp' and it will go dull. Also, there seems to be a general consensus that for cheap/soft knife/steels, the best advice is to have a semi-coarse finish on the edge. I am only a quarter of the way of reading this thread, and I read the Spyderco thread, so this is a preliminary view.

Sorry I should have been more clear. The first statement I was looking for the source of the knife myth that you can get a knife too sharp that it dulls. The second statement, to me more exact, is a DMT Diamond Fine edge finish.
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 23, 2014 07:09PM
This is a good example if the knife myth I am talking about. He starts to mentions it at 6:15.
Knife myth coarse edge fine edge
And this is the 'unbiased' and 'scientific' test. Note my comments.

Toothy edge vs. Mirror Polished

Odd, my comments are gone. I had a short back and forth discussion about the testing technique.
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 23, 2014 08:11PM
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jasonstone20
This is a good example if the knife myth I am talking about.

He seems to be a fairly nice fellow, but he says some odd things like he knows how his knives perform even though he doesn't test them and his comments on metallurgy are a bit odd such as his knives are as hard as high carbon steels can be at 58/60 HRC.

In regards to edge retention, you just have to be much more specific than he does to make true statements. For example you can find butchers who prefer a high polish and butchers who prefer a coarse finish. They use the same knives, cut the same things -but- they use two very different method, one uses a draw and one more of a push.


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Odd, my comments are gone. I had a short back and forth discussion about the testing technique.

I think they are still there, did you ask about switching the knives/finish? YT does odd things with comments.

He is comparing two very different geometries as his polished edge is heavier/thicker by his own description and you can see on the initial cutting he does on the fruit that he has rounded the apex and over buffed it and it doesn't cut into the skin well. This is why he makes the comment that the polished edge doesn't cut as well.
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 23, 2014 08:54PM
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CliffStamp
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jasonstone20
This is a good example if the knife myth I am talking about.




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Odd, my comments are gone. I had a short back and forth discussion about the testing technique.

I think they are still there, did you ask about switching the knives/finish? YT kdoes odd things with comments.

He is comparing two very different geometries as his polished edge is heavier/thicker by his own description and you can see on the initial cutting he does on the fruit that he has rounded the apex and over buffed it and it doesn't cut into the skin well. This is why he makes the comment that the polished edge doesn't cut as well.

Yes, that was me.

WC also makes some interesting knives. I have only seen pictures and youtube videos, but from what I saw I like his work. It is just that he used the semi-ambiguos language with elements of truth based on opinion, perspective, and relativity to this or that, that is so common in knife myths, so I thought it was a good example of what I was initally refering to.



Edited 1 time(s). Last edit at 11/23/2014 09:00PM by jasonstone20.
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 23, 2014 11:23PM
Just as a quick check to see if the 36-grit ghetto stone works on anything other than hemp I cut up a few dirty mats a friend just gave me. These were left outside for a few weeks so they had visible dirt on them as in mud-clay, not just general inside house dust and light debris. They were also partially frozen as the temperature here has been dipping below zero off and on. I initially intended to do a rough run where I cut until I could not slice a piece of paper but that didn't work as the 36-grit edge really doesn't ever want to not do that.

I used the Bushman from Cold Steel (SK-5 / 54 HRC) which in general is a really nice knife for this kind of work, assuming you can use the handle which is slick and very conductive. It is trivial to grind and sharpen even with simple abrasives, very resistant to fracture and has a decent cutting geometry for a blade which can be used for chopping. However you would want to avoid very knotty woods as you can buckle the hollow primary grind.

I compared the 36-grit edge to a 600 DMT bevel both ground at 15 dps on an edge bevel which is < 10 dps. There was no comparison at all, you would not need to measure anything to notice these differences :

-the 600 DMT edge blunts at a fairly rapid rate from an initial high sharpness and you can feel it getting smoother immediately

-the 36-grit belt edge does not cut as well initially, but takes almost no change initially and only very slowly changes in use

I measured the sharpness as normal and stopped when the sharpness went under 1% :

-600 DMT : 110 to 130 slices

-36 grit : 380-400

The difference would just increase if the stopping point was moved even lower because the blunting rates are not at all comparable. I wanted to cut until they could not slice photocopy paper but the first run with the 36-grit finish showed that even getting past the point of cutting newsprint would make me run out of mats with just one round (I did two rounds with each finish).

There is simply no comparison in the way they blunt and the choice is obvious :

-if I was doing just a few cuts, use the 600 DMT finish as it cuts better initially (would want another stone to reset the edge)

-if I had to do a lot of cuts, use the 36-grit belt finish as even on dirty carpet it it takes forever to kill the edge

If I only had one abrasive then use the 36-grit belt as it will reset the edge in just a few passes and could grind the primary, edge and apex all just as readily.
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 24, 2014 12:42AM
That is impressive. I wonder if there is someway with these lower grit stones to minamize the possible damage to the apex from the grit itself. Maybe loading the stone with a higher grit stone to create a slurry?



Edited 1 time(s). Last edit at 11/24/2014 12:48AM by jasonstone20.
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 24, 2014 02:00AM
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jasonstone20
I wonder if there is someway with these lower grit stones to minamize the possible damage to the apex from the grit itself.

The damage is essentially what produces the edge retention. This is the initial apex :



This is it at the end, it is worn sure, but still has lots of aggression :



Here is the 600 DMT apex at the start :



Yes it is much finer, less "damaged", but that is essentially why it goes dull much faster.
me2
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 24, 2014 02:33AM
Just to be clear, these are all for slicing cuts, and are somewhat specialized for cutting abrasive materials that are relatively soft on a slice? For general utility that might require a finer edge, these finishes (the 120 and 36 grit ones specifically) are not optimal.
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 24, 2014 02:45AM
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me2
Just to be clear, these are all for slicing cuts, and are somewhat specialized for cutting abrasive materials that are relatively soft on a slice?

Yes, I am getting some hard material to slice up, the problem is that most hard material to cut isn't at all abrasive and you can cut a LOT of it without doing anything to the edge. However the large trials I ran were with 600 DMT and similar edges, not ultra-coarse ones. That is a very valid point/concern.

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For general utility that might require a finer edge, these finishes (the 120 and 36 grit ones specifically) are not optimal.

Yes, as I noted in the above, trying to do push cuts was a horrible failure. The force requirement can be so high the edge (not apex) will collapse. I don't think Mark would appreciate if I reset all his chisels, planes and even gouges to a 36-grit belt finish.
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 24, 2014 02:53AM
That is an interesting thought. I wonder what the lowest grit I could use and still get satisfactory results would be. Similar to your TCE charts would it make my sharpening more efficient and work if I stopped at 320 instead of 1500 sic paper? I will have to look into that.

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Re: Edge retention with different grit finishes on 3Cr13 stainless
November 24, 2014 04:24AM
I see. I was thinking it would be better if the pattern was more uniform, but the photo you just displayed more what I had in mind, since some of the earlier images had huge, long chunks out of the apex.
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 24, 2014 02:24PM
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jasonstone20
... since some of the earlier images had huge, long chunks out of the apex.

Keep in mind that those shots are of very high magnification, they only show a very tiny portion of the edge. As the grit gets larger the consistency is reduced. It is the deep irregular gouges which give the high edge retention in this application.

Now there is an interesting question, is it possible to get a finish this coarse but still have high sharpness, as that is the only real weakness of the finish.
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 24, 2014 03:17PM
Wouldn't that be the much criticized buffed edge?

_______________________________________________________________________________________________

Always in search of a good choppa'
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 24, 2014 03:53PM
You mean take a buffer to it, that just reduces the coarseness of the finish and I suspect would just lower the edge retention significantly assume you didn't over heat it as well.

What I would like to do is make an edge this coarse but the apex was still very thin. Imagine if you had the same apex width as a polished edge which just rode up/along that very coarse finish.

I know a few ways to do it, but they are simply not at all practical, one for example is just to use an extremely fine file to make a micro-serrated pattern, the time though isn't sensible.

I think the very coarse Atoma's might do it because of the way they make their plates and the very precise layout and structure of the abrasives.
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 24, 2014 06:41PM
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CliffStamp
You mean take a buffer to it, that just reduces the coarseness of the finish and I suspect would just lower the edge retention significantly assume you didn't over heat it as well.

What I would like to do is make an edge this coarse but the apex was still very thin. Imagine if you had the same apex width as a polished edge which just rode up/along that very coarse finish.

I know a few ways to do it, but they are simply not at all practical, one for example is just to use an extremely fine file to make a micro-serrated pattern, the time though isn't sensible.

I think the very coarse Atoma's might do it because of the way they make their plates and the very precise layout and structure of the abrasives.

That is why I suggested loading it with maybe the cheap hardware stone, anything of a higher grit, that might smooth it out a little, but not to much.
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 24, 2014 07:25PM
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jasonstone20


That is why I suggested loading it with maybe the cheap hardware stone, anything of a higher grit, that might smooth it out a little, but not to much.

Yes you can, but all that will do is trade off edge retention. You could simply just use the fine side, or make a few passes on the fine side but not enough to completely rebevel if you wanted an inbetween sort of finish.
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 24, 2014 09:17PM
Ok, I think I am getting a better picture or what is going on. I think I will go back to the beginning of this post and read it again to see the direction this is heading and if I missed something.
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 24, 2014 10:35PM
I have some 180 grit SiC mesh 'professional abrasive cloth'. Is this the same stuff as the drywall screen? By the way, I found it slow cutting last time I used it, which suprised me because of the grit and that it was SiC.



Edited 1 time(s). Last edit at 03/24/2015 11:50PM by CliffStamp.
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 24, 2014 10:41PM
Drywall sanding mesh is pretty much exactly what it sounds like, it is a open mesh which is coated on both sides :

-Lowes : [www.lowes.ca]

The reason why it is a mesh is because plaster dust will fill a sandpaper quite rapidly and it will stop cutting, the mesh allows you to sand longer without having to knock the plaster dust loose.

By the way, you can just hit reply, you don't need to quote a post just to respond to it.
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 25, 2014 04:00PM
Couldn't you potentially use a really thin rod (of a higher finish), which makes very small contact pressure, at a bit of a higher angle to refine the edge?

_______________
Coffee and Blood
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 25, 2014 04:08PM
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Shurdi3
Couldn't you potentially use a really thin rod (of a higher finish), which makes very small contact pressure, at a bit of a higher angle to refine the edge?

Yes and it would increase the polish and reduce the edge retention on a slice, just move it along the graph to the right.
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 25, 2014 05:06PM
Thank you for the reply trick. It doesn't always work on all forums, so I got out the habit of using it. What I have is similar to the mesh, but it comes on a roll, like a roll of tape. I think it is meant for use on pipes and things that are hard to reach. I will try it out again, see if the results are different as far as cutting speed, the knife I was using it on was pretty dull and made of cheap stainless. I'll try some carbon steel on a already profiled blade and see if there is a difference.
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 25, 2014 05:46PM
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CliffStamp

[...]

Now again I need to repeat this again with this knife/steel, just to bound the results.

That wasn't terribly exciting, but a second round produced the same type of performance, this one was about 5% higher for the long term edge retention and I spent a little more time on the initial sharpness. It is possible to get it to shave but you would want skin like Uvogin to say it is even tolerable as you have to use a decent amount of force and it scapes your first layer of skin off as it cuts the hair. If you lather / wet your arm it is a little more tolerable, but it would be a real stretch to call it shaving sharp.
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 28, 2014 01:35AM
I have two Soft Arkansas Pocket stones, and they are absolutely fantastic. The finish they put on a knife egde is easily mistaken for a mirror finish, and it will easily tree-top hair and whittle-beard hair.
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 28, 2014 01:46AM
I tried the 180# mesh tape on the small blade of a SAK, it cut fast and left a scraping sharp edge. After aligning the grit pattern and stropping 2 to 3 pps on Enkay Green on MFB, it shaved easily. I have done any more cutting tests.
Re: Edge retention with different grit finishes on 3Cr13 stainless
November 28, 2014 03:01AM
As a quick check on overlaying grits I finished an edge with the CBN rods and then did 5 pps with the medium rods. There was a marked improvement in sharpness on both the slice and the push cut - however the edge retention on a slice decreased by the same amount as expected.



I only did two runs, I would want at least two more to even have light confidence but there is nothing unexpected about the result. It just moves the performance from the CBN towards the Medium rods. I suspect that as you do more passes it would simply move closer.

However if you find the CBN too coarse and the Medium too fine then just apex on the CBN and do a few passes on the Medium to make an effective grit which is between them. A curious question would be if you used the fine rods would they make a larger difference or smaller one?

Note that the difference in performance in this graph from left to right is 50X, that is fifty times higher edge retention and this isn't even the limit of the performance. I think the 36 grit is a little low as I only used it a few times to sharpen so I don't have the technique down yet - plus to be frank once the cuts go over 1000 I tend to be a little sloppy so the performance is likely biased towards a lower number.

Plus of course I am not confident that 36 grit is actually the highest performance one, I am going to try some 24 grit (not really looking forward to that if it is better) as that is a common sharpening abrasive. I have seen very low grits but they tend to be used for grinding granite not steel and I suspect the abrasive crystals are a different shape to make them stronger but less sharp.

In any case, if you combine this effect with the apex angle effect it looks like the influence of grit+apex angle on edge retention on a slice is much more than 100:1. If this doesn't make you see how small an influence steel is compared to geometry and sharpening, well, you definately are not a redneck.

--

Note that if you click on the image it takes you to a page in PB where you can click on it to magnify it significantly.