Opinel Inox Fast Edge Fade?

[pinnah]

I think I suffered a sharpening technique fail and would like some guidance and thoughts.


I've been using an Opinel Inox for the month or so. It's made with Sandvik 12C27, which from what I gather from prior discussions is somewhat close to 420HC (I have a lot of experience with) and 440A (some experience with).

I was shocked with how fast the edge on the Opinel faded. It dropped off really fast.

I don't have a jeweler's loop, so I can't confirm this but this is what I *think* is happening and I'm hoping that those of you with more experience can correct or guide.

I sharpened the Opinel on my Lansky rod system. I put a 17 degree back bevel on it followed by a 20 degree primary bevel. On my Carbone Opinels, which are hardened to 56Rc, I've noticed that hard use will end up with dented edges, so I additionally put a 25 degree final cutting bevel on those and get reasonably good edge retention when doing that. But, knowing that the Inox is supposed to be up in the Rc 58 range, I thought I would get away with 20 degrees.

One of the big differences I notice in sharpening carbon to this set "kind of" stainless is that when not hardened, it has a tendency to retain a wire edge or burr during the honing. The Victorinox Inox is the worst I've felt. Case SS (420HC) is a bit better. Buck's 420HC though hasn't been a problem and the Schrade 440A is only a tick worse in this regard. Both are hardened in the 58Rc range though.

So, I was really hoping that the Opinel Inox would, like Buck's 420HC not have much of wire edge issue.

Never-the-less, I'm suspecting that when I honed the Opinel Inox, all I did was manage to get a thin wire edge that stood up straight and felt sharp initially but that folded over quickly in use. I knew things were bad when cutting summer sausage on a backpacking trip was less than super easy.

Perhaps the heat treat is just a bit softer than 58? Perhaps I rushed the honing?

Question 1: Does it sound like I'm the right track in understanding why the edge faded so fast?

Question 2: Is honing the blade at a slightly higher final edge angle (say, 25 degrees in this case) the best way to deal with a stubborn wire edge or are there other suggestions?

Thanks,

 

[OHALLUM]

In my experience, the Inox on the Opinel's work best with a more obtuse angle than a thin one. (at least on the #8 and the #6) Have not had an issue with a stubborn wire edge. When mine are sharpened, they have an almost non existent visible grind on them, pretty much like they came from the factory. Does that make sense? You can only see a thin line of polished edge when done. I have not had any problem with the edges degrading from normal use. I don't baby them, but do carve some wood and cut small branches without any problem. They are push cutting paper and arm hair shaving sharp when done sharpening.

Blessings,

Omar

 

[Obsessed with Edges]

It's got to be a wire edge, assuming there wasn't some sort of mistake in heat treat. My INOX Opinel has been impressively durable, especially as compared to the 'carbone' Opi. I've thinned both of mine, to zero-grind at the edge. The 'carbone', as you mentioned, is pretty delicate and easily dents if bumped into something hard. The INOX has been noticeably tougher, and has surprised me accordingly, considering how thin I've ground it (easily inside 15°/side, more likely less than 12°/side).

I thinned & honed both of mine with wet/dry sandpaper (convexing), and almost exclusively maintain those edges on strops, using either/both of 600-grit SiC and green compound (on balsa; seems to work best). Over time, both knives have a near-mirror finish all the way to the cutting edge. Part of what's impressed me with the INOX is, it still seems to retain some aggressive 'microtoothy' character, even as I've continued to strop it to higher polish.

Sandvik specs 12c27Mod up to 59 RC. Based on how mine has held up, I'd bet Opinel took advantage of that, or very nearly so.


David

 

[pinnah]

Thanks guys!

Spent some time stropping on 800 grit wet/dry over the leather strop board with edge trailin strokes. Still not very confident about going to a full convex bevel but we'll see. Hair runs off my arm when I reach for the knife but we'll have to see how it hold up.

David, I should have mentioned that by time it dulled, I could feel the burr if I was careful. Am I right that stainless of this ilk just requires a tad more attention during honing?

 

[Obsessed with Edges]

Thanks guys!

Spent some time stropping on 800 grit wet/dry over the leather strop board with edge trailin strokes. Still not very confident about going to a full convex bevel but we'll see. Hair runs off my arm when I reach for the knife but we'll have to see how it hold up.

David, I should have mentioned that by time it dulled, I could feel the burr if I was careful. Am I right that stainless of this ilk just requires a tad more attention during honing?

Yes, that's almost exactly the impression I had of the difference between the INOX and the carbone, when I thinned & sharpened both of mine. I was impressed that the INOX could take an edge nearly as fine as the other, but it just took a little more time. It was also a good indoctrination to trailing-edge sharpening with the wet/dry paper, for me. I've come to like the method, because I haven't had nearly the same troubles with burrs & wires when finishing up. That includes sharpening 420HC and VG-10, which previously were at the top of my 'PITA burr-makers' list of steels. Really opened my eyes.


David

 

[pinnah]

Some advice then...

If I sharpen using stones and edge leading strokes and form a burr,

1) would it be best to hone and deburr on wet/dry with edge trailing strokes or would it best to attempt to hone and deburr on the stones first, thereby risking just standing up a straight wire edge?

2) when honing on wet/dry with edge trailing strokes, do you use a slightly more obtuse edge angle than the primary to take off the wire or burr? Something like a micro-bevel or micro-convex just at the apex?

 

[me2]

Edge trailing strokes will enhance burr formation. Increased angle, short travel in sections, and edge leading strokes will help remove burrs. I've not used Opinels yet, but 12c27 is generally nice and easy to deal with w/r to burrs.

 

[Chris "Anagarika"]

David,

Your method of burr removal almost opposite to edge leading theory, as discussed in bluntcut's apex thread .. I'm interested to learn what is different or perhaps other factors that might contribute to the success?

I recalled, in the microbevel burr removal thread, we all agree that it requires just enough pressure to make the abrasive cut the burr, but less than needed to reform an opposite burr.

 

[Obsessed with Edges]

David,

Your method of burr removal almost opposite to edge leading theory, as discussed in bluntcut's apex thread .. I'm interested to learn what is different or perhaps other factors that might contribute to the success?

I recalled, in the microbevel burr removal thread, we all agree that it requires just enough pressure to make the abrasive cut the burr, but less than needed to reform an opposite burr.

I'm firmly convinced it's all about pressure, when either creating burrs, or removing them. Some find it easier to remove burrs using edge-leading technique, and others (myself) have become most comfortable doing it with edge-trailing technique. When I started doing all of my maintenance sharpening with sandpaper in edge-trailing strokes, the difference in burr creation was night & day, compared to when I was using edge-leading. Early on, when first learning to use the sandpaper, I did lean into it a bit too hard, and the burrs were still an issue. Everything changed when I started treating the sandpaper exactly as I used a strop: with very light pressure and conservatively low angle.

If you think about it, when you consider basic stropping technique, most will agree that at least part of the goal of stropping is to minimize and remove/clean up burrs. If the edge-trailing stroke is best for that on a strop, why should it be any different at somewhat coarser grit? Pressure is what will make the most difference, so far as I'm concerned, and the direction of the stroke is almost moot to me. Choice of abrasives and substrate can make a big (HUGE) difference as well. Both of those factors will be further influenced by the pressure exerted.


David

 

[Obsessed with Edges]

Some advice then...

If I sharpen using stones and edge leading strokes and form a burr,

1) would it be best to hone and deburr on wet/dry with edge trailing strokes or would it best to attempt to hone and deburr on the stones first, thereby risking just standing up a straight wire edge?

Do as much burr-refining as you're comfortable with on the stones. The sandpaper can further help with burr removal, but (as emphasized in my just-posted reply to Chris), how you use it (pressure applied) can either make or break it. If you use sandpaper exactly as you would use a strop, with very light pressure and conservatively low angle, it can work very well in removing burrs. Or, at the very least, making them so small and thin as to be easily removed on the strops later.

2) when honing on wet/dry with edge trailing strokes, do you use a slightly more obtuse edge angle than the primary to take off the wire or burr? Something like a micro-bevel or micro-convex just at the apex?

Keep the angle conservatively low, on sandpaper. In other words, use it exactly like a softish leather strop that would tend to form around the edge, when pressure is applied. Taking the angle any higher than used for honing will round the apex, on any surface that has any give to it.


David

 

[fsatsil]

I had a stainless Opinel 8 a while back and it would roll its edge very easily. I think its a combination of the thin edge and soft steel(I've heard 55-56rc). Next time it gets dull try touching it up on a sharpening steel, that's what worked for me. 12c27 is a great steel but edge holding is not one of its strong points.

 

[Obsessed with Edges]

I had a stainless Opinel 8 a while back and it would roll its edge very easily. I think its a combination of the thin edge and soft steel(I've heard 55-56rc). Next time it gets dull try touching it up on a sharpening steel, that's what worked for me. 12c27 is a great steel but edge holding is not one of its strong points.

I'll just say (respectfully, and I mean this) I flatly disagree with that. Somehow I think I'm not alone.

Depending how old your stainless Opinel was, it might not've been 12c27 anyway. Opinel switched away from another stainless some years ago (maybe in the '90s/early 2000s), though I don't remember what type it was. I have one of the older ones, in a fillet knife pattern from Opinel (purchased back in early '80s), and it's stainless hasn't impressed me either. But that wasn't the Sandvik 12c27Mod that they're using now.


David

 

[pinnah]

I had a stainless Opinel 8 a while back and it would roll its edge very easily. I think its a combination of the thin edge and soft steel(I've heard 55-56rc). Next time it gets dull try touching it up on a sharpening steel, that's what worked for me. 12c27 is a great steel but edge holding is not one of its strong points.

It might be that you and I are experiencing the same problem. Sandvik makes a lot of press about fine grained steels like 12C27 being "tough" by which they mean able to be deformed without breaking and chipping. They also claim 58Rc in terms of hardness, as does Opinel.

One possible explanation for both of us is that the "toughness" (or some other feature of stainlesses of this ilk) allows them to form wire edges. If honed but not removed, this will feel sharp for short while and then will fold over to a burr under use. Like you, my edge more or less recovered when I steeled it on a ceramic rod, but it faded quickly again. My sense is that all I was doing with the steel was resetting the burr and standing it back up as a straight wire edge without really removing it.

That's my theory anyhow.

FWIW, my understanding is that Opinel's Carbone is hardened in the 56Rc range and with that, I've definitely found edge retention better at 25 degrees. Double FWIW, I've also found that I punch my Opinels through stuff I wouldn't do to other knives, so maybe that's an argument for me needing a more obtuse angle regardless!!! Rented mule comes to mind.

 

[Chris "Anagarika"]

David,

Thanks for response. If the sandpaper has some 'give' depending on the backing, edge leading with same pressure will have more burr than edge trailing?

Perhaps we can discuss more on this on a separate thread?

Pinnah, sorry for OT.

 

[Obsessed with Edges]

David,

Thanks for response. If the sandpaper has some 'give' depending on the backing, edge leading with same pressure will have more burr than edge trailing?

Perhaps we can discuss more on this on a separate thread?

Pinnah, sorry for OT.

The main reason I prefer edge-trailing over edge-leading, on sandpaper, is to avoid issues of the edge digging in, if the angle gets a little too high, or if the 'give' under the paper allows the paper to roll around the edge, and subsequently snag or bunch up against the edge. That creates problems of it's own, and burring may or may not be part of that. Rounding or blunting of the edge is my bigger concern there. On harder backing, any 'digging in' of the edge into the surface is going to magnify pressure anyway, if only momentarily. For me, that is when it's more likely I'll have additional burrs to fix or clean up. This all goes back to the primary issue of pressure exerted into or lateral to the edge, which I feel is what creates burrs, or makes them larger.

I tend to relate a lot of this back to the burrs created on a tool like a Sharpmaker, if pressure is just a hair too heavy against the corners of the rods, while making an edge-leading stroke down the rod, to the base. I noticed some time back, it's more difficult to do the same, if the edge is moved UP the rod, in trailing fashion. Pressure exerted laterally into the edge by the rod seems noticeably lighter, and burrs don't form nearly as easily in that direction. Obviously, a tool like the Sharpmaker wouldn't work as efficiently that way, because pressure is significantly lighter. But the difference in burrs formed in each direction made me think a bit about the effect of edge-trailing strokes on more aggressive grit surfaces.

It's sort of late for me now, and this stuff can tend to process my brain when I start to overthink it (I usually try to avoid this anyway). But maybe it is a good topic for discussion in it's own right.


David

 

[pinnah]

Guys, I don't consider it OT so please continue. If you move to another thread, just point me there.

I think the more general question (now that I'm on the right track) is how to best hone steels like 12C27, 420HC, 440A, Aus8 so as to avoid new burr formation (assuming a fixed angle apex as David describes, which makes sense to me in practical terms).

David, I'm a bit confused about your advice to take a conservatively low angle while honing on sandpaper. I *think* I understand you to mean that you want the paper to reach the apex but just barely in a sneak-up-on-it manner. Otherwise, it wouldn't remove the burr at the apex, right?

The other approach I've used/attempted/not too well with is using a slightly *larger* angle with light pressure and edge leading strokes.

This approach has worked fine for carbon steel, but I suspect that this approach just "stood up" a wire edge with no detectable burr to one side or other (until it was used.

This I think is my real question. With steels of this sort that smear easily and that are fairly tough and pliable (burrs don't snap off), how does one knock off that wire edge without dulling the apex?

 

[Obsessed with Edges]

Guys, I don't consider it OT so please continue. If you move to another thread, just point me there.

I think the more general question (now that I'm on the right track) is how to best hone steels like 12C27, 420HC, 440A, Aus8 so as to avoid new burr formation (assuming a fixed angle apex as David describes, which makes sense to me in practical terms).

David, I'm a bit confused about your advice to take a conservatively low angle while honing on sandpaper. I *think* I understand you to mean that you want the paper to reach the apex but just barely in a sneak-up-on-it manner. Otherwise, it wouldn't remove the burr at the apex, right?

You understand my meaning perfectly. In fact, I've described it in the past in exactly those terms ('sneak up' on it). :thumbup:

The other approach I've used/attempted/not too well with is using a slightly *larger* angle with light pressure and edge leading strokes.

This approach has worked fine for carbon steel, but I suspect that this approach just "stood up" a wire edge with no detectable burr to one side or other (until it was used.

This I think is my real question. With steels of this sort that smear easily and that are fairly tough and pliable (burrs don't snap off), how does one knock off that wire edge without dulling the apex?

This is what I've been aiming at before, when emphasizing how burrs like these need to be gently abraded away, as opposed to trying to break them off. That 'sneak-up-on-the-apex' concept is how I get that done, and doing so in progressively finer grits also helps. It's easier when you've noticed the burr is folded to one side or the other, and you can slowly and very lightly file it down from that side, using edge-trailing strokes. If done lightly, tenaciously ductile steels like 420HC and VG-10 won't even flip the burr to the opposite side, and that makes filing it down that much easier. It's sort of amazing to me at times, how tough a seemingly small burr or wire edge can be, on steels like these.


David