How To Maintain an edge on super steel knives

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maximus83

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Nov 7, 2011
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How do you maintain an edge on super steel knives? In cases where you are not reprofiling or fixing edge damage, but simply maintaining an edge that has light to moderate wear.

For this thread, define 'super steel' loosely as modern PM steels that have high vanadium carbide content. Popular suspects: S30v, S35vn, S90v, S110v, Elmax, M390, 20CV, CPM 3V, and similar.

Interested to hear:
  • What method you use, and why. Stropping on X, edge-leading strokes on a high-grit stone, etc.
  • What type of abrasives you use, and why. I've heard all kinds of responses here in the forum on this. Everything from plain strop/no compound (what material?), strop with compound (diamond, cbn, ???), fine ceramics (mildly controversial, but a number of accomplished sharpeners here do this), belt sander, or using coarse, fine, or high-grit stones.

What I've been trying:
  • A few light edge-leading strokes on DMT fine diamond. Finally found a great use for my DMT fine plate: maintenance of super steels! It's just right, fine enough to not remove too much metal, but still coarse enough to not destroy my coarse scratch pattern that I normally sharpen with. Also tried DMT EF, since it removes less metal, but didn't like how much this overground the coarse scratch pattern and reduced slicing aggression. Assume the same logic would apply to DMT EEF, but maybe I'm missing something.
  • A few stropping passes on wood strop with CBN 1 micron compound to remove any fine burr. Works but is a bit slow, I have some 4 micron CBN to try next.
 
3FBBD6FD-2B86-49D8-A2ED-1DF55608AB05.jpeg I use Naniwa high grit (3000 & 6000) bonded Diamond “stones”, edge leading, with water, over the pond, using my home made jig. The stone in the picture is a Shapton, but the Naniwas are the same size. You forgot S-125-V on your list.
 
tiguy7 said:
high grit (3000 & 6000) bonded Diamond “stones”, edge leading
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Just as Tiguy7 said ^

For the alloys you mentioned diamonds are going to give the best overall results I would think.
For touch up I go as high as 8000, because I happen to have one that I bought to complete the set long ago, and just free hand it holding the stone in one hand and the knife in the other. I also do some edge trailing to kind of burnish and refine the edge further but it takes some fairly high magnification in a jeweler's visor . . . for me any way.

PS: I forgot to post the "Why"
I see you enjoy toothy so you will be forgetting about the 8000 etc.
I use it because I do a lot of push cutting for trimming and even when I think "slice" or "slicey" I still prefer polished edges and blade bevels because it has less drag in the cut and so, I feel, more control.

Separate from the trimming comment above . . .the other day I sharpened a box knife with just 120 Shapton Pro and then stropped with 600 diamond. It cut OK but I could feel just all kinds of drag so there is a limit to toothy . . . hahahah . . . and I found it.
 
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So it sounds like both of you are fans of using high-grit stones for maintenance. Is that a general-purpose approach, you use it for most of your blades folder/fixed/kitchen? Also, if you were doing what I do in sharpening most of your knives at a coarser grit to retain toothiness, would that change your maintenance approach at all?
 
maximus83 said:
So it sounds like both of you are fans of using high-grit stones for maintenance. Is that a general-purpose approach, you use it for most of your blades folder/fixed/kitchen? Also, if you were doing what I do in sharpening most of your knives at a coarser grit to retain toothiness, would that change your maintenance approach at all?
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Well I just have this aversion to stropping; I hate everything about it from futzing with the caky goop to all the tons of strokes it can take to effect a change in the edge.
So . . .
If I had to strop toothy blades I would get a Tormek or use a similar leather wheel. The speed of the wheel can melt the hard sticks with the buffing compounds and the high surface feet per minute can geeeeeeterdone quick. Depending on how picky you are not to round the edge you may want to lean toward a thinner and harder strop material than the Tormek comes with (that was just the first example that sprung to mind and we all know what a Tormek is).

My philosophy, from lots of experience sharpening lesser steels like A2, is if I can't do it in six to ten strokes per grit grade, per side, I am using the wrong grit material. The realm of 60 or 150 strokes to refine an edge with one grit on a strop etc., to me, sounds preposterous.

Just a few strokes ONCE A BLADE EDGE IS APEXED on each grit should be all that is required.
 
To repair & tune my s90v blade I use a fine diamond. I use mine w/ this steel and they will degrade and curl after use. Like when pruning fruit trees or when cutting hard fiber plants like sugar cane. When I feel the edge curled or a burr I take it the fine diamond w/ soapy water applied
and back hone it. 3-4 or 5-6 strokes seems to fix it. I'll examine the edge w/ my 7X head set and this leaves a good edge ready for use. DM
 
Wowbagger said:
My philosophy, from lots of experience sharpening lesser steels like A2, is if I can't do it in six to ten strokes per grit grade, per side, I am using the wrong grit material. The realm of 60 or 150 strokes to refine an edge with one grit on a strop etc., to me, sounds preposterous.

Just a few strokes ONCE A BLADE EDGE IS APEXED on each grit should be all that is required.
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I hear you on the desire to minimize needless sharpening process and steps, and especially stropping. I think over time I'm gravitating closer to your approach of at least reducing, if not skipping, the traditional stropping process. In my post about the chisel grind, I didn't even strop the edge on that blade at all.

David Martin said:
To repair & tune my s90v blade I use a fine diamond. I use mine w/ this steel and they will degrade and curl after use. Like when pruning fruit trees or when cutting hard fiber plants like sugar cane. When I feel the edge curled or a burr I take it the fine diamond w/ soapy water applied
and back hone it. 3-4 or 5-6 strokes seems to fix it. I'll examine the edge w/ my 7X head set and this leaves a good edge ready for use. DM
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Thanks David, that's really helpful. Curious to know: Have you tried maintaining with a higher grit, then dropped back to the fine diamond as the best middle ground? I tried the higher grits for maintenance, where the goal was "remove less metal", but just couldn't get results I was satisfied with.
 
I take a few edge leading passes from the last stone I used or go back to the one before that if needed - currently that is the Venev 400 and 800 stones.

I just can’t get the hang of stropping.
 
I was talking tune up on high VC blades. If I want a quick tune up, I use the sides of a TiAlN coated blade at 92 HRC to steel the edge (edge leading). The VC’s in a blade are 82 HRC.
Most of my non VC knives are sharpened to 2000 on the Shaptons. They can be “steeled” on a ceramic blade or the coated steel blade. If I perceive that an edge is rolled, I will steel the knife edge trailing to align the roll, and then steel edge leading.
To steel with coated blades you need to know the pecking order. Blade and tool coatings- TDLC=72 HRC. WC=72 HRC. TiN= 82HRC. ZrN=85 HRC. TiCN= 88HRC TiAlN= 92HRC. Blade inclusions- see Vickers chart. WC can be an inclusion and/or a coating. TDLC is WC (Tungsten Carbide). So WC is 72 HRC or 2400 Vickers, and VC is 82HRC or 2800 Vickers.
Disregard the HRa scale. It’s not the same as HRC. You will notice 7D1677A9-54C3-4C9C-8989-71C1BB433B47.jpeg F5D3360A-E16F-4DED-BA19-FF52E624783B.jpeg some discrepancies in hardness between the 2 charts.
The second chart shows the relative hardness of various abrasives. You can see that Al2O3 and SiC are softer than VC but harder than WC.
 
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I just use my sharpmaker ultra fines like crock sticks knife in one hand uf rod in the other.

For just maintaining an edge that works great for me.
 
83, I think I understand what your saying. The knife w/ s90v steel came sharpened on a coarse diamond. (comparing edges until I found the same scratch pattern). I liked this edge so, when it needed maintenance I took it to the fine diamond because like you I was looking to save metal. It worked and I camped there. Most knife steels will curl or develop burrs when cutting hard materials. Not so w/ card board. DM
 
I normally sharpen these steels a little rough and strop on diamond/Silicon carbide blend compound, on paper over hard backing.

Even if I run them to a finer finish microbevel (3micron DMT) I will normally touch up on the hard strop. Another option is to backhone on diamond lapping film. Backhoning on a resin bonded diamond grit stone also works well.
 
If I'm wanting to maintain the same edge finish, as well as general sharpness, it's simple: I just use a few very light passes on the same tool with which I finished the new edge in the first place. This is generally what I do with any of my knives, whether 'super steel' or not. If I stay on top of not letting it ever get too dull in the first place, it's never going to be an issue with removing a lot of steel to keep it in good shape, even when maintained on a stone. Just have to stay ahead of it.

If maintaining the same exact edge finish isn't that important, and sharpness is the top priority, any minimal stropping that can be done is what I'll do first. Usually that'll be on something like bare leather, or paper over a stone, for the sake of straightening or aligning the edge. If that still doesn't quite get it back to where I want it, sharpness-wise, then it's back to the first method described above. Truthfully, in my uses, that's almost always where I'll circle back to anyway. Most of the 'super steels' I've used aren't very prone to burring, which means if I use a strop at all with them, it's going to be with the goal of polishing the finish, and not so much for deburring.

The only reason I'll deliberately favor any kind of compounded stropping anymore, for the most part, is if the edge I'm working on already has a more polished finish that I want to maintain. For example, I use an inexpensive santoku in the kitchen that I've thinned a lot and polished to a very thinly convexed, mirrored finish; it works GREAT for the kitchen uses I give it. Most of the time, I just use a polished kitchen steel to keep the edge aligned. But if or when it needs more, I'll remove the weakened steel at the edge and reset it on a stone, then refinish to the same polish on a denim strop with compound. That's about the only exception, with my knives. Otherwise, I'm generally going to favor the added edge crispness and 'tooth' afforded by doing all of the touching up on the hones.
 
I did not pull this into my OP, but there's a relevant point about stropping as part of the maintenance routine, from @ToddS ScienceOfSharp site. Comes from the pages The Pasted Strop part 1, and part 2, I've always been interested in seeing if this proves useful in knife sharpening maintenance (as well as straight razors, which Todd ran his tests and SEM photos on).

Couple of interesting quotes about the role of stropping with compound from the above linked docs:
The primary goal of stropping is to reduce the edge width by increasing the bevel angle near the apex (micro-convexity). Abrasive particles (paste, spray, etc) are applied to the strop to increase the rate of abrasion.
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And...
The example above was chosen to illustrate the goal of pasted stropping; to increase keenness (reduced edge width) by introducing convexity to the the last few microns of the apex. This effect is distinct from producing a convex bevel; in this case the bevel was shown to remain triangular other than those last few microns. I will use the term “micro-convexity” to describe this effect.
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Provided you have a hard strop (so you don't convex the main bevel), provided you have a compound that can abrade your super steel, and provided you use good stropping technique, it seems plausible that this micro-convexing occurs when you strop a super steel knife correctly. I don't always strop these as above--because it isn't always necessary as others noted, and also because sometimes, if your form isn't good, you can actually degrade the edge sharpness a bit. But when I do my part, I have noticed that on super steel blades, stropping with diamond or cbn compound gives a small but significant boost in cutting performance, I assume because of this 'micro-convexity' effect that is created right at the edge as you abrade the steel there, slightly increase the angle, and slightly reduce edge width. I don't have an SEM to prove any of that :p, but it seems really plausible based on Todd's photos and what I've seen in blade performance.

As a practical matter, I'm gravitating like others are towards mostly just using the stones/plates. But when I want to wring out that last little bit of sharpness, I can see the case that Todd made for still stropping on compound. I'm convinced it's doing a bit more than merely polishing my edge.
 
A few edge leading strokes on a 600 or 1200 grit eze lap diamond plate to refresh the microbevel. Great for toothy edge, and you remove enough metal to don't degrade edge retention (as you would by using a fine ceramic f.e.).
 
Lately I’ve been setting back bevels with 220 grit stone on an edge pro, creating a micro with medium spyderco rods in a sharpmaker, and mainting that micro with spyderco fine rods. This seems to work well with S30V and M4, but my S110V edges don’t seem to last as long as I feel like they should.
 
83, I can kind of see what he's saying. Realize he must have straight razors in mind. When I strop my double edge razor blade (& knife) I'm not trying to convex the edge. It just happens. 2) Nor am I trying to reduce the edge width. Which may happen naturally. I'm after increasing keeness, straightening the edge and removing any burrs. DM
 
From my experience with M390, I go Medium, Fine, Ultra, and a clean (emphasis on clean) smooth leather strop from tandy. But M390 is the golden child for sharpening, and my virgin XHP cold steels (as in still having factory edge, not unused) just get a woodstock extra fine compound (~450-600 grit) on corrugated cardboard. Actually, before my sharpmaker everything got woodstock with cardboard, and it worked well to maintain a toothy edge.
Footnote: I made a whole post about the cardboard thing before and I'm just waiting on stropman to get better.
 
maximus83 said:
I did not pull this into my OP, but there's a relevant point about stropping as part of the maintenance routine, from @ToddS ScienceOfSharp site. Comes from the pages The Pasted Strop part 1, and part 2, I've always been interested in seeing if this proves useful in knife sharpening maintenance (as well as straight razors, which Todd ran his tests and SEM photos on).

Couple of interesting quotes about the role of stropping with compound from the above linked docs:

And...


Provided you have a hard strop (so you don't convex the main bevel), provided you have a compound that can abrade your super steel, and provided you use good stropping technique, it seems plausible that this micro-convexing occurs when you strop a super steel knife correctly. I don't always strop these as above--because it isn't always necessary as others noted, and also because sometimes, if your form isn't good, you can actually degrade the edge sharpness a bit. But when I do my part, I have noticed that on super steel blades, stropping with diamond or cbn compound gives a small but significant boost in cutting performance, I assume because of this 'micro-convexity' effect that is created right at the edge as you abrade the steel there, slightly increase the angle, and slightly reduce edge width. I don't have an SEM to prove any of that :p, but it seems really plausible based on Todd's photos and what I've seen in blade performance.

As a practical matter, I'm gravitating like others are towards mostly just using the stones/plates. But when I want to wring out that last little bit of sharpness, I can see the case that Todd made for still stropping on compound. I'm convinced it's doing a bit more than merely polishing my edge.
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There are a number of variables at play when it comes to stropping. I've also seen Todd's SEM images following backhoning on a king 6k, they showed no convexity. It will depend a great deal on how hard the strop is for certain. Also the abrasive in question, size, texture of the strop surface.

At any rate, even microbeveling will convex the edge somewhat with a few repeated passes from the variation in manual accuracy. If the edge is set good and low (as it should be anyway and even more so with a "super steel"), a few degrees off the top will probably only help with retention and have little or no negative effect on cutting performance - a slight bump in pressure cutting bias maybe.
 
^So HH, do you think then that the application of Todd's findings from straight razors to knife sharpening are either "small" at best, or "unproven" at worst? Been looking into that a bit lately, as I observe some small improved performance from stropping a well sharpened blade, but the difference is definitely small and certainly does not prove that the micro-convexity thing is the cause.
 
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