Sharpening Stainless Steel and Japanese High Speed Tool Steel
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Clay would you please post your stone progression and medium types used. Thanks
I’ve only used the 1500# diamonds and the 9 micron films. The scratches that the 1500# diamonds leave are right around 3 microns, nearly identical to the original grind of the edge from Spyderco. The first time I touched it up, I only used the 1500# stones and the second time, I used them again but added some strokes with the 9 micron films because the stones cut more deeply than the films and the films are quick at knocking off the higher ridges from the stones. So I still have scratches that are roughly 3 microns wide but aren’t very deep.
Clay can you be specific with your sharpening technique? I am still battling a couple of chef’s knives, (a ZDP-189 and a R2/SG2) that are proving difficult to sharpen. What direction stroke did you employ? Edge trailing, or edge leading, heel to tip, or tip to heel? Was your stroke more perpendicular to the edge or more horizontal or longitudinal? The specifics give me a technique to copy to see if it improves my results with my chef’s knives.
It sounds like you left it toothy, didn’t strop and didn’t apply a micro-bevel. Is that correct? I would hope to expect an expensive knife made of these Japanese Super Steels to out perform the older more typical steels. I’m finding that’s not necessarily the case. Thanks for the specifics in advance.
Marc
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I used edge leading strokes, alternating side to side on each stroke, just a little off of perpendicular from the edge. I just realized that I should have stropped it and that I’ve deviate from the factory edge a little. When I first examined the edge, I found that it had been sharpened at 15.5 degrees and had been stropped enough to make the edge angle 16.5 degrees. I should have looked up my settings instead of relying on my memory. So now I’ll re-profile it a little back to 15.5 degrees and then strop it at 16.5 degrees.
-Clay
I’m becoming a little less enamored with my ZDP-189 Stretch. I used it to cut a batch of cardboard up this last week and was surprised to see a number of chips along the edge when I looked at it with my ‘scope. I had been sharpening to 17 dps with a 20 dps microbevel until recently, but switched to a straight 20 dps bevel a while back when I seemed to be getting quite a few chips. Apparently 20 dps isn’t the answer for me. At Rc64, the edges of these knives don’t deform like softer steels, but they are subject to fracturing. They do get dull eventually, but you don’t see the dents and dings you get with softer steels. Unfortunately, the chips can be quite deep, requiring the removal of quite a bit of steel and being as hard as it is, sharpening can take a while longer. I think I’m going to try a serious convex edge to see if it can mitigate some of the chipping.
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In our testing, there is a very slight performance gain in sharpness when using edge leading strokes. To test sharpness, we measure the force, in grams, required to cut through a material. To start, we sharpen a sample blade to a specified grit level and at a specified angle and then measure the sharpness. In the case of stroke direction, we’ll sharpen two sample blades to the same grit level and at the same angle, but use edge leading strokes on one and edge trailing strokes on the other. A blade done with edge leading strokes to 1000# at 20 DPS might require 150 grams to cut the material. Its counterpart done with the same settings and edge trailing strokes might need 153 grams to cut the material. So it’s a slight improvement, only a couple of grams, but maybe worth the effort.
-Clay
Clay, was the sharpness test done after only these two stroke directions of sharpening strokes, that is no stropping to finish or smooth either of the sharpened bevels?
By chance, did you follow up that performance comparison by stroke direction with the HHT also by the same stroke direction? I’m guessing the opposite results would be the case with the HHT.
Marc
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Well, it looks that Clay got his 2 cents worth in before me. I’m a “hunt ‘n pecker” typist.
Clay, what is the advantage of edge-leading sharpening? I often do that too, but I also often use the kind-of semi-horizontal movement that my girlfriend calls the “Clay movement” (you often show it in your videos) and sometime edge-trailing.
We probably ought to move this to a more specific thread, as many ask this question. I don’t mean to step in ahead of Clay on this, but I’d like to get my 2 cents in before I leave for the evening.
I had suspected for some time that when sharpening with relatively low grits stones, there was a tendency to break off pieces of the apex and that this seemed to be much worse when using trailing edge strokes. About a year ago (maybe a bit less) Clay showed us some microphotos of edges he was working on (I don’t recall the original purpose of his tests) and it appeared that leading edge strokes left a more uniform edge than when using trailing edge strokes.
What I’m leading up to here is the fact that diamond abrasives are a form of machining – they don’t polish, they scratch. And when the grit is low and the steel is relatively fragile, pieces may break off. While this seems obvious at low grits, we don’t know at which grit level the breakage stops, or at least becomes insignificant.
After Clay’s photos, I started to go leading edge only. Up to a point. Above 400 grit, I’ll resort to scrubbing strokes, but I try to keep the up-strokes at a lower pressure. Of course, when you go to film, you are obliged to use trailing-edge strokes to avoid slicing the film. Hopefully, the grit at that point is so fine that edge breakage isn’t a factor. Or is it?
I recall some years back hearing that there was a faction of older sharpeners who complained that diamond abrasives were inferior when compared to other media. This is similar to the stereophiles’ complaints that digital music (CDs) was inferior to pure analog systems (meaning LPs and vacuum tube systems). Yeah, there maybe was an audible difference if you had really, really good ears, but you couldn’t buy a stick of gum on the difference. Well, maybe there’s a difference in a diamond-produced edge, and maybe this is the stropping advantage.
I’m becoming a little less enamored with my ZDP-189 Stretch. I used it to cut a batch of cardboard up this last week and was surprised to see a number of chips along the edge when I looked at it with my ‘scope. I had been sharpening to 17 dps with a 20 dps microbevel until recently, but switched to a straight 20 dps bevel a while back when I seemed to be getting quite a few chips. Apparently 20 dps isn’t the answer for me.
Tom what type/direction stroke have you employed? Tom how close or far off of perpendicular to the edge are you applying your scratch patterns? I’m honing in on a method or technique, (pun intended), that gives me results without too much effort and resulting failure. It’s been a long slow process to try different things without removing too much steel. Plus, whatever edge I apply, whether I like it’s feel or not lasts a long time because the steels are so dang tough. I believe I don’t see the failure rate you are because I’m using longer kitchen knives compared to your shorter folding knives. The wear I place on the steel is spread out over a wider area and the cellulose and coarse material in fresh food is far less dense and coarse than that in cardboard and paper products, you’re cutting.
Marc
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I recall some years back hearing that there was a faction of older sharpeners who complained that diamond abrasives were inferior when compared to other media. This is similar to the stereophiles’ complaints that digital music (CDs) was inferior to pure analog systems (meaning LPs and vacuum tube systems). Yeah, there maybe was an audible difference if you had really, really good ears, but you couldn’t buy a stick of gum on the difference. Well, maybe there’s a difference in a diamond-produced edge, and maybe this is the stropping advantage.
For what it’s worth, the guy in the video that I posted was not using diamond abrasives. He’s sharpens with the Edge Pro products and he was observing the same problems that Marc has seen with the Shapton glass stones and high hardness steels.
I’m becoming a little less enamored with my ZDP-189 Stretch. I used it to cut a batch of cardboard up this last week and was surprised to see a number of chips along the edge when I looked at it with my ‘scope. I had been sharpening to 17 dps with a 20 dps microbevel until recently, but switched to a straight 20 dps bevel a while back when I seemed to be getting quite a few chips. Apparently 20 dps isn’t the answer for me.
Tom what type/direction stroke have you employed? Tom how close or far off of perpendicular to the edge are you applying your scratch patterns? I’m honing in on a method or technique, (pun intended), that gives me results without too much effort and resulting failure. It’s been a long slow process to try different things without removing too much steel. Plus, whatever edge I apply, whether I like it’s feel or not lasts a long time because the steels are so dang tough. I believe I don’t see the failure rate you are because I’m using longer kitchen knives compared to your shorter folding knives. The wear I place on the steel is spread out over a wider area and the cellulose and coarse material in fresh food is far less dense and coarse than that in cardboard and paper products, you’re cutting.
I’ve settled in on a fixed pattern for each grit. 400 is down and toward me; 600 is down and away from me; 800 is down and toward me; 1000 is down and away from me, etc. If I decide at some point to pursue a mirror finish, I can tell pretty well which grits I need to concentrate my efforts with by the scratch patterns. If I need to concentrate on a specific area to remove more steel, I will use more vertical strokes, taking care to blend the steel removal with the rest of the edge. Often – especially with longer blades – instead of a single long diagonal stroke, I will use a series of shorter, diagonal strokes – imagine a saw-tooth pattern – to finish a particular bevel. Where I expect to need to remove a lot of steel, I may use a series of ten or fifteen diagonal strokes for each two inches of blade length. I’ll overlap those series of strokes to average out the scratch patterns. Whatever floats yer boat… or trips yer trigger…
MarcH, What is your conclusion with sharpening hard steels? Maybe they are not meant to be sharpened / polished to high grit? Does it retain sharpness if you make it toothy at lower grit? You mentioned that knife was sharpened at quite low grit from the original Japanese manufacturer. If you have more ideas, please continue to post. I’m all ears. Thank you for bringing this topic up and posting your experience.
I wouldn’t bring Maxamet to this discussion since reports about them are pretty contradictory and most likely something was messed up with them. Would be more interesting to further investigate Japanese kitchen knives.
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Clay, was the sharpness test done after only these two stroke directions of sharpening strokes, that is no stropping to finish or smooth either of the sharpened bevels? By chance, did you follow up that performance comparison by stroke direction with the HHT also by the same stroke direction? I’m guessing the opposite results would be the case with the HHT.
We’ve done all sorts of testing with stroke direction, stropped, not stropped etc.., and we’ve often gone on to HHT after the other tests. I’ve got most the results buried here in the forum somewhere. %‑)
It’s hard to get a blade to a high level of HHT with no stropping except at very low angles and it helps to finish with a few light edge trailing stokes at a high grit because it stretches the apex into a foil edge that is very thin.
One of the things I hope to accomplish with the new grit chart is to include the sharpness results. We will probably have a some sort of legend which will indicate if a knife finished with that grit at n° will:
- Cut Paper
- Copy Paper
- News Print
- Tissue
- Rough Shave
- Medium Shave
- Smooth Shave
- HHT
- 1
- 2
- 3
- 4
- 5
It will also list the grams of force required to cut through the medium in the sharpness machine. So it might look like:
P-NP, MS, HHT3, 175g which would indicate that it cuts paper smoothly up to news print, provides a medium shave, passes HHT 3 and requires 175 grams to cut the medium.
This is still a ways off and awaiting a new intern here at the office.
-Clay
Thanks for your interest, dulledge.
Super Steels, why it chips, or what makes it chip, seems like a simply explanation; it’s brittle. Learning how to sharpen it while avoiding the chipping was where this Forum Post originated. We are trying to learn how best to sharpen newly named and newly formulated steels. The same steels can differ from knife maker to knife maker depending on how it has been handled and how it has been hardened and from batch to batch when made and handled by the same knife maker, also. If we had a standardized steel with standardized hardening maybe it would be easier to learn which sharpening method or technique to employ to give the best results. Then we still have the issue, what in your opinion may be the best edge may differ from my opinion of the best edge. Thus for me, it’s an on going study.
I think that the Maxamet steel does fit right in with the subject. We really don’t have anyway of knowing if it’s a badly handled batch affecting the Maxamet dilemma or not. Unless we gathered every knife example out there and put them under standardized tests, there’s really no way to know.
Data from past experience with different known steel recipes drives this desire to create these new “Super Steels”. (Oh, and goofy people like me that think harder is better so we’ll buy it). We have the physical aspect of the metallurgy soup that’s made, heated, mixed, dissolved, cooled and hardened with different known precise percentages of components and we also have the electrochemical aspect of the metal elements affecting the steel. Who really knows how changing even a minute percentage of any one component or the time or heat level involved when simmering the steel soup or how it’s cooled will affect the final product. Then when they make the knives and turn them loose for use to play with, we get to figure out how to make them work best, or work better and maintain them. It’s fun for me, being part of those trying to figure this out. Frustrating also, but still fun.
Marc
(MarcH's Rack-Its) - Cut Paper
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