Finishing grit for skinning knives?

[Eli Chaps]

The toothy microbevel is supposed to be about 4 or 5 degrees wider than the polished edge.

I don't want to speak for @samuraistuart but I think what he's saying is, that if you micro bevel at 600 grit, then your actual cutting edge is 600 grit. So why bother with an 8000 grit polished bevel above that? What would be the benefit of that? Just curious what you're pondering there.

 

[000Robert]

I don't want to speak for @samuraistuart but I think what he's saying is, that if you micro bevel at 600 grit, then your actual cutting edge is 600 grit. So why bother with an 8000 grit polished bevel above that? What would be the benefit of that? Just curious what you're pondering there.

Just to have both - a toothy edge and a gorgeous polished edge.

 

[Eli Chaps]

Just to have both - a toothy edge and a gorgeous polished edge.

Okay so just an aesthetic thing then. I suppose if that's what you want.

I don't mess with micro bevels but there might be a question about longevity. I don't know if a courser true micro bevel would would wear faster than a full edge bevel of the same grit.

 

[000Robert]

Okay so just an aesthetic thing then. I suppose if that's what you want.

I don't mess with micro bevels but there might be a question about longevity. I don't know if a courser true micro bevel would would wear faster than a full edge bevel of the same grit.

Ok. Thanks for the help.

 

[Eli Chaps]

Ok. Thanks for the help.

Not sure I was any help.

 

[wootzblade]

Does anyone have experience specifically with skinning? I tried to skin a hog with my spyderco sage because it was in my pocket at the time, but it had a fairly polished edge (6k, stropped with flitz polish) and didn't work as well as the cheap butcher knives lying around the skinning rack.They seemed to have coarse edges and the guy I was skinning with used a steel to bring the edge back a couple times (hog skin is quite tough).

I have a Spyderco Gayle Bradley that I want to set up for skinning. I'm thinking about putting either a 320 or 1000 grit edge on it with my shapton glass/suehiro waterstones. Does that sound right for a skinning knife? What do you guys do?

This thread has taken a wrong direction.
The problem is not in that your edge is polished, the problem is that neither S30V in your Spyderco Sage, nor M4 in the Spyderco Gayle Bradley should be honed on regular stones or stropped with Flitz and alike aluminium-oxide based compounds.

These knife steels must be sharpened with CBN or diamonds, and honed with diamonds.

Have a look at SEM images of the premium knife blade on this website:
https://scienceofsharp.com/2019/11/03/carbides-in-maxamet/

The above SEM images clearly show that when we sharpen a wear-resistant knife steel using anything but diamonds and CBN, it is not possible to polish those wear resistant carbides sharp, as we only abrade the steel matrix around them, burnishing it to the edge, and eventually getting a sharp strip of steel lacking in wear-resistant carbides that won't last long. As we start cutting with this edge, the sharp steel apex quickly turns into a relatively dull edge made of big unpolished carbides.

This is the only reason why your Spyderco Sage in S30V performed worse than a mainstream s/s knife.
A dull knife has over 1 micron edge, and the unpolished vanadium carbides average 1-2 microns in the best CPM knife steels.

Wear-resistant knives have special sharpening requirements. Sharpen them with CBN and diamonds and they will take a razor edge that will outperform a mainstream knife by x 10s times.

 

[Mr.Wizard]

wootzblade In your testing at what percentage of vanadium does the above apply?

 

[nutsforknives]

This thread has taken a wrong direction.
The problem is not in that your edge is polished, the problem is that neither S30V in your Spyderco Sage, nor M4 in the Spyderco Gayle Bradley should be honed on regular stones or stropped with Flitz and alike aluminium-oxide based compounds.

These knife steels must be sharpened with CBN or diamonds, and honed with diamonds.

Have a look at SEM images of the premium knife blade on this website:
https://scienceofsharp.com/2019/11/03/carbides-in-maxamet/

The above SEM images clearly show that when we sharpen a wear-resistant knife steel using anything but diamonds and CBN, it is not possible to polish those wear resistant carbides sharp, as we only abrade the steel matrix around them, burnishing it to the edge, and eventually getting a sharp strip of steel lacking in wear-resistant carbides that won't last long. As we start cutting with this edge, the sharp steel apex quickly turns into a relatively dull edge made of big unpolished carbides.

This is the only reason why your Spyderco Sage in S30V performed worse than a mainstream s/s knife.
A dull knife has over 1 micron edge, and the unpolished vanadium carbides average 1-2 microns in the best CPM knife steels.

Wear-resistant knives have special sharpening requirements. Sharpen them with CBN and diamonds and they will take a razor edge that will outperform a mainstream knife by x 10s times.

Interesting. I don't know what the abrasive is on my suehiro cerax and rika stones, but it seems to put extremely fine edges on whatever steel I throw at it, it just takes time. I guess that might be kinda deceptive if the carbides have been ripped out of the edge. Since my initial post, I picked up a new strop from chefknivestogo. Actually, 1 magnetic strop base and a few magnet backed pieces of leather, as well as some 1 micron and 0.5 micron diamond paste. Do you think that stropping for a while with diamond paste will be good enough to avoid the issue?

 

[Rhinoknives1]

About 40 years ago, I stopped using regular knives for skinning and bought a dedicated skinning knife. Even though it's an "El Cheapo" Chicago Cutlery, it's made all the difference in the world.
View attachment 1341778

It’s the curve of the belly If a knife that does the cutting while skinning. Straight blades no matter how sharp just don’t have the finesse ...

 

[nutsforknives]

wootzblade actually I gave that article a closer look, and it confused me a bit. It seems to be saying that knives actually cut better with the carbides exposed. He finished his edge on an 8k shapton glass stone. I use a comparable stone from Suehiro, the Rika 8k.

from the article: "Some time ago, I was asked a question by Stefan Pusch about an observation discussed at http://kochmalscharf.freeforums.net/ regarding an observed improvement in edge retention for high carbide steels when finished with a JNat hone. Below, I show that a JNat has the same effect as the Shapton Glass 8k, to expose the carbides near the apex."

He seems to be drawing a different conclusion, that high carbide steels perform best finished on something other than diamond that will expose the carbides.

 

[wootzblade]

Nutsforknives, You are not taking this "carbide exposing" step out of the context, are you?
Todd describes the sharpening process for that wear resistant knife in the paragraph above:
"The blade was easily sharpened with diamond stones (200,600,1200) at 17 degrees per side and the apex polished with 1 micron diamond lapping film"

The "carbide exposing" step is optional, to increase the slicing aggression. You can do without this 8K step, but you cannot do without sharpening wear-resistant steel with diamonds (or CBN).

M Mr.Wizard - in our tests, that are in line with observations of many sharpeners, from 3% Vanadium sharpening on CBN/diamonds is a must, but even those with 1-2% benefit from that and show better edge retention.

 

[eveled]

For skinning you need a thin knife with a curved belly. All you are cutting is the fat layer that attaches the hide to the body.

By nature your skinning blade is not the right blade for the opening cuts through the skin. Down the legs around the ankles etc.

Using the right tool for the job makes it easier.

 

[David Martin]

Ankersons tests do not agree with this ^ as he sharpens with SiC to 400 grit on steels like S90V and gets great edge retention.
I also do similar cutting tests and find the coarse sharpened edge cuts much longer. Sharpened around 200 grit on cutting sisal rope. DM

 

[Mr.Wizard]

David Martin

If they're aluminum oxide or silicon carbide then they'll work fine on any steel, including high-vanadium steels, up to about 400 ANSI grit (~700 JIS). Vanadium carbides are only about 3µ in size, and when the abrasive grains are large enough they just gouge out the carbides along with the steel. If the stone is VERY hard then you can still glaze the stone if you're using anything short of oil or similarly lubricating fluid (glycerin, for instance) to reduce wear from friction, and high pressure, but usually glazing is a sign of using insufficient pressure to dislodge worn particles and/or not lubricating the stone sufficiently. If it happens only after a decent span of time, then just re-dress the surface to manually shed the worn surface grains.

Aluminum oxide and silicon carbide will effectively cut almost any steel, including high-vanadium steels, up to about 400 ANSI grit. Diamonds and other super-abrasives are only a requirement for high vanadium steels at grits in excess of 400 ANSI. And those high-vanadium steels generally give the greatest performance with a toothy edge, anyhow, because the biggest advantage to highly wear-resistant steels is usually in slicing tasks in dirty environments, not in push-cuts.

A good rule of thumb is that if a steel has over ~3.5% vanadium content you'll want to use diamonds or CBN abrasives for grit ratings above ~400 ANSI/~360 FEPA F/~700 JIS. At or below that grit rating silicon carbide and aluminum oxide abrasives will scoop the fine vanadium carbides out along with the steel matrix, but above that grit rating the size of the abrasive vs. carbides gets too close to do that anymore. Pretty much anything outside of that scope can be handled by conventional synthetic abrasives, though.

ANSI 400 grit is about the highest grit that still works well on vanadium carbide steels due to the difference in size of the abrasive vs. the carbides. Imagine using a shovel to move different sized stones. As you progress from fine sand to pea gravel, to crushed rock, and then to small cobbles, past a certain size the shovel no longer penetrates into the medium well and you have to move to using a stone fork instead. It's very similar with aluminum oxide and silicon carbide abrasives vs. vanadium carbide. Fortunately, vanadium carbides are very tiny, averaging typically around 3µm in size, and so ANSI 400 grit is still able to gouge them out of the steel substrate without too much trouble, but that's the limit of where it's still actually effective. Finer than that and that's where you'd want to make the switch to diamond/CBN.

 

[HeavyHanded]

Personally I believe the larger abrasives are capable not only of excavating the carbides but also fracturing them.

Any sharp edge is sub-micron across the apex, so the carbides are either scooped out whole with the ones left being aligned with a narrow part of the carbide exposed, or some of them break off at the impact site.

But yeah, about 400 grit, maybe 600 for lower % carbide.

 

[ToddS]

My preliminary look seems to show that the carbides are either "scooped out" whole or "pushed in" and the ones "pushed in" eventually become crushed into many smaller bits. I need to look at a few more cases, but at the moment I don't see any good reason to sharpen Maxamet or S110V into a fine edge.

 

[David Martin]

Here we go again, off topic on this vanadium carbide issue. Many here have said that it requires an XX fine diamond grit to begin shaping the VC . Many of us sharpeners don't go that fine and still get very good edge retention with the vanadium steels. DM

 

[nutsforknives]

Nutsforknives, You are not taking this "carbide exposing" step out of the context, are you?
Todd describes the sharpening process for that wear resistant knife in the paragraph above:
"The blade was easily sharpened with diamond stones (200,600,1200) at 17 degrees per side and the apex polished with 1 micron diamond lapping film"

The "carbide exposing" step is optional, to increase the slicing aggression. You can do without this 8K step, but you cannot do without sharpening wear-resistant steel with diamonds (or CBN).

M Mr.Wizard - in our tests, that are in line with observations of many sharpeners, from 3% Vanadium sharpening on CBN/diamonds is a must, but even those with 1-2% benefit from that and show better edge retention.

I am wondering, if you can finish the edge on a softer abrasive to get maximum aggression and edge retention, why can't you use a softer abrasive all the way through? I completely reprofiled and convexed my s30v benchmade 940 using my synthetic Japanese waterstones. I had no trouble working up a burr, deburring, polishing etc and ended up with a fairly aggressive edge that is fine enough to whittle hairs. Finished by stropping on an 8k stone, deburring with a strong pull through wood. Maybe there is a mismatch between what performs well vs what looks good under a microscope or something? I'm just not understanding. I don't use diamonds, yet I can get results as good or better than when I sharpen low alloy carbon steel. Either my cut tests deceive me and the edge won't last, or you don't actually need diamonds to put a good edge on S30V. I haven't noticed any premature dulling on my 940, so I think it might be the latter. Am I missing some information?

 

[wootzblade]

Sure mate, stones can do a lot to high vanadium steels, but please keep in mind that what they do, they do chiefly to the steel matrix between the carbides, not to the vanadium carbides themselves. In the S30V the matrix is near 90%, so of course you see a lot of change to the steel sharpened on the stones.

Todd has shown on his website and in posts on this forum that silicon carbide and aluminium oxide can somewhat abrade wear-resistant carbides, but far from what diamonds do to them.

By sharpening your S30V on stones, you get an edge of steel lacking in wear-resistant carbides. It is relatively easy to strop this edge to hair-splitting razor strip of steel.
As you start cutting, this edge, even though stronger than anything we see in mainstream knives, wears quickly until there are sufficient carbides to slow the wear of the edge.
But because the stones cannot sufficiently grind the hard carbides, they are never as sharp as you get on CBN or diamonds. When we reach the vanadium carbides sharpened on stones, we perceive this moment as our premium knife has turned dull quicker than a mainstream knife. This is exactly what you describe in your experience with skinning the hog in the start of this thread.

The real power of the premium edge is in the wear-resistant carbides, and we unleash this power with CBN or diamonds. Sharpened with CBN and diamonds, they take a razor edge that outperforms a mainstream knife by x 10s times.

 

[nutsforknives]

Sure mate, stones can do a lot to high vanadium steels, but please keep in mind that what they do, they do chiefly to the steel matrix between the carbides, not to the vanadium carbides themselves. In the S30V the matrix is near 90%, so of course you see a lot of change to the steel sharpened on the stones.

Todd has shown on his website and in posts on this forum that silicon carbide and aluminium oxide can somewhat abrade wear-resistant carbides, but far from what diamonds do to them.

By sharpening your S30V on stones, you get an edge of steel lacking in wear-resistant carbides. It is relatively easy to strop this edge to hair-splitting razor strip of steel.
As you start cutting, this edge, even though stronger than anything we see in mainstream knives, wears quickly until there are sufficient carbides to slow the wear of the edge.
But because the stones cannot sufficiently grind the hard carbides, they are never as sharp as you get on CBN or diamonds. When we reach the vanadium carbides sharpened on stones, we perceive this moment as our premium knife has turned dull quicker than a mainstream knife. This is exactly what you describe in your experience with skinning the hog in the start of this thread.

The real power of the premium edge is in the wear-resistant carbides, and we unleash this power with CBN or diamonds. Sharpened with CBN and diamonds, they take a razor edge that outperforms a mainstream knife by x 10s times.

Do you think stropping with diamond paste after using japanese whetstones would do the trick, or would I need to use diamonds all the way through? I already have a 140 grit diamond plate, but my 320,1k,5k and 8k are all Japanese stones. I do have a couple leather strops loaded with 1 micron and 0.5 micron diamond paste. What equipment/procedure would you suggest for putting a proper edge on high vanadium knives? I would consider buying a high grit diamond plate for finishing the edge. Would a DMT Dia-sharp EF or EEF do it?