Which steels would you NOT use diamond stones on and why?

J

jalapeno

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My question is based on posts in another thread I didn't want to hijack.

For example, what is the issue with using diamond stones on steels like VG-10?
Is this a widely-held belief or are there special circumstances?
 
Not so much particular steels (though in some cases, yes), but the hardness and geometry. High hardness, thin kitchen knives is where I personally don't use diamonds, except at the stropping stage where I do use 1-micron diamond compound on a balsa strop. Some of those blades can be a little chip-prone so I don't like to introduce deep scratches into the blade edge while sharpening.

High hardness fine-grain carbons, like Hitachi white and blue steels, don't need the aggressiveness of diamonds and you'd spend some time polishing the scratches out.

I would not have a problem using diamonds on a Spyderco Delica in VG10, for example. Different edge geometry and I am not going for a super thin edge.

I use diamonds on my Elmax steel ZT folders, but not with my SG2 Shun Kaji/Fuji kitchen knives, even though both are PM steels. The ZT is a thicker blade with a different purpose.

That may or may not be a legitimate concern. I don't work in a sharpening test lab, so I haven't tested every possible variation. I just want sharp knives at home. I have a set of water stones that I use for kitchen knives. They work for me. If you want to use diamonds, give it a shot and examine the edges using a good magnification to see how it plays out.
 
I'm similar to jc. I don't use diamond stones on kitchen knives or knives with steels up around 440c. As it's not needed to cut these steels. Plus, I like the edge oil stones leave (SiC & India). When sharpening steels containing vanadium, is where I'll start considering a diamond stone. And I normally bring only the xcoarse and coarse. So, if someone is picky about taking an edge to a higher grit I'll use a 4-500 grit SiC that I'll finish on. DM
 
I use my diamond stones all the time on all the steels. I do not use them only on the cheap soft steels as I have witnessed diamond pull off from the matrix. VG10 is a decent steel, a little bit on the chippy side, especially if it is around HRC 61. I see no problems here. Everything is in the technic
 
I use diamond on high carbide steels and that's pretty much it. On occasion I will use them on some tool steels but primarily it is high carbide steels like s90v
 
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I carry diamond 'credit card' hones in my pocket as the default, go-to sharpener for anything I happen to have or use, if I don't otherwise have convenient access to my other sharpening gear. So, I don't have any issues using them on any steel I do have. With some steels at very high hardness that may be a little more prone to chipping, I'd just make sure to keep the touch light and rely more on finer grit (F/EF/EEF), to minimize the possible chipping risks brought by deeper-cutting, coarser-grit diamond. I generally take the same, finer-grit approach on softer, low-wear steels which wouldn't otherwise actually need diamond; but I don't exclude using a diamond hone on those, if it happens to be what I have on hand at a given moment, when I need it. It's not like they're going to be damaged by it, even if diamond isn't necessary for it.

I do understand that other stone types would likely be more optimal for very hard & thin, chip-prone steels that don't actually need diamond. But, if something like diamond were always prone to damaging such steels via chipping, I'd likely not use such a fragile steel in the first place, as it'd be more trouble than is worthwhile, to me. I'd prefer a little more chip-resistant toughness in a steel, over extreme edge-holding, any day.


David
 
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The only time I'll use diamond plates is when I have a significant amount of sharpening to do on a knife. That usually means repairing the edge, thinning the knife, or re-profiling the edge. I then take coarse bonded water stones and work all the scratches out from the diamonds then work my way up to finer grits this way I don't have any deep scratches from the diamonds. I also use diamond paste on my strops anywhere from 3 micron to .25 micron.
 
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Haven't seen rigorous tests on the idea implied in your OP: that although diamonds can sharpen every steel type, some steels will have less issues or will sharpen better with other abrasives. If anybody's aware of such testing, please share a link.

In my usage, which is not as a professional sharpener: diamonds sharpen fast and effectively, they're a universal abrasive and work on VG-10 as well as every other steel type. Like others, I prefer the sharpening feedback I get from actual sharpening stones made of natural or synthetic materials versus diamond plates. Also, depending on what abrasive you use, the edge finish can have a different quality to it. I am not doing fancy edge finishing of high-end kitchen knives, with 15K or 30K polished abrasives, etc., so I have no idea of what differences you might see if working at that level. But from doing ordinary home sharpening of utility knives, folders, large and kitchen knives, I definitely 'prefer' using other stone types besides diamonds when I have the option to do so. But I can't honestly say that the other stones I have actually get my knives any sharper, based on the simple sharpness/usage tests that I do after sharpening. If a person wanted to have just one small-ish set of stones that could sharpen every type of steel you have, you'd be hard pressed to find a better option than a set of diamond plates in 3 or 4 common grits, say 200, 300/400, and 1200.
 
I use diamond hones for 99% of my sharpening, as they work well on all steels, and are necessary for today's new generation of high carbide powder steels. Once in a while I'll haul out a big Black Arkansas bench stone that I inherited from a great-uncle and touch up my high carbon steel blades; it produces a hair-topping edge on those steels (52100, 50100, 1095, 1070).
 
Answer is complicated. I understand most of the time people just want a simple answer but I prefer not to describe an elephant by finger tip at one spot :p

Our mind is amazing at situational-auto-adaption, practicality often driven-unawared by $ + availability. Sharpening analytically for 99+% of steels...

An ideal abrader = High density as sharp as possible cutting/shaping bit supports sharpening unit of operation on steel.

==* Let's look at a few avail budget base options *==

Print $
10x3x3 stones - similar to Shapton Glass Professional line with diamond/cbn instead of ceramic. This series would sharpen 99% of steels, just make sure only sharpen using fresh abrasives (release via sharpening and or induce). Hey, stop thinking about wasting printed $ on high cost per operation situations - just print some more OK :rolleyes:

Invest well, cry once
Get multiple lines of SiC, AlO, Ceramic, diamond, cbn stones & plates. Sharpen with abrasive well matched for steel attributes. I.E. basically use sharpest abrasive per stroke. e.g. between Shapton 5K and DMT EEF, well non-glazed shapton has sharper abrasive than broken-in DMT EE, hence use shapton. This is applicable to whole range of steels regardless of hardness.

Smarty can afford it when wanted to
A complete grit range of high density ceramic stones. Large+Cheap+ready-to-release-grit for grit 60-400 and combination of sigma & shapton pro or glass (depend on preference of stone hardness). Overlap with diamond plates for grit/mesh smaller than 12 microns, use these for apex refinement (no more than 1-2mm wedge). It is a given that 'refinement' = low pressure gentle touch, right? yes.

Shoe Box Racer
$14 240/800 - Alumina waterstone
$19 2K/6K - Alumina ws
$17 - 1K & 3K 6.5x3" plates
Race you!

==**==

In general, I would avoid using diamond/cbn plate to sharpen steels with hardness below 58rc because abrasive may dig/penetrate too deep and swarf could dislodge abrasive from plate nickel substrate. To mitigate this, you can certainly use diamond with appropriate pressure for proper/sustainable abrading depth to avoid stripping abrasives away from plate. 'Mitigate' means reduce dislodge rate - from wear faster than normal (avg) rate.
 
Probably 95% or more of the blades I DO sharpen with diamond are at/below 58 HRC. This likely includes even my CRK Sebenza in S30V (they've sometimes been criticized for being 'too low' in hardness, too prone to edge-rolling damage), for which it's carbide content warrants using a diamond hone over other stone/abrasive types.

I'm convinced now, after using diamond hones so often on my softer steel blades, that the issue of diamonds being pulled out of the nickel plate by softer steels is more an issue of defective plating/bond and/or really bad use of pressure (much too heavy), and is nonexistent otherwise. My diamond plates, even the cheap ones I've used from Harbor Freight, still look like they've never even touched softer steels after I've used them on Case & Victorinox blades, as well as other simple stainless kitchen knives, all of which are in the HRC 55-57 range. I've used Fine/EF/EEF diamond on the Victorinox blades almost exclusively, because their stainless responds so well to an aggressive, biting diamond-grit finish. I think the more carbide-heavy steels I've sharpened, like S30V, D2 or ZDP-189 have likely produced more visible wear, in the form of scratches in the nickel. But even that's been relatively minor.

And assuming pressure used is part or all of the problem:
On softer steels, calibrating the 'touch' used for grinding/rebevelling pressure is pretty easy. Take a low-alloy stainless blade (inexpensive kitchen knife will do) with polished bevels (makes it easier to see how scratch pattern will change), and lubricate the hone with oil or water (my preference is mineral oil). Lay the bevel flush to the hone, and put the pad of one fingertip immediately behind the bevel in the portion making contact on the hone. Grip the butt end of the knife's handle with only the tips of your fingers (not a 'full-fisted' grip), maintaining just enough hold to control it's movement and stabilize it. This ensures it'll be difficult or impossible to press too hard, from either end of the knife, with either hand. Make ONE pass across the hone, applying just enough pressure with the fingertip behind the bevel to keep the bevel flush, and no more. Then take a look at the scratch pattern on the bevel, and it should be immediately obvious how it's changed from polished to a finish matching the grit of the hone used. Having seen that, it becomes apparent how little pressure is needed to deeply cut & scratch the steel, even for rebevelling tasks. Anything heavier than that won't increase working speed, and will likely clog the hone at least, especially if it's used dry. A clogged & dry diamond hone is an inducement to press harder, for most of us; so don't let it get clogged in the first place (this is why I like mineral oil on them). A lighter touch also goes a long way toward reducing burring issues, on any stone, whether diamond or not.


David
 
I would avoid using too course diamond stones on soft steel that doesn't have vanadium or other hard carbides.

Because it will be like sharpening butter.

SiC is going to work with a majority of steel types but wears out fast and needs to be flattened often. It's probably better than using diamonds for most steel. Plenty of other stones that will work foe soft steel also.
 
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Mo2 said:
I would avoid using too course diamond stones on soft steel that doesn't have vanadium or other hard carbides.

Because it will be like sharpening butter.

SiC is going to work with a majority of steel types but wears out fast and needs to be flattened often. It's probably better than using diamonds for most steel. Plenty of other stones that will work foe soft steel also.
Click to expand...

I agree with you about SiC. I think they are a great all-around stone that works well for most steels out there. I had always used diamond on my very very dull blades but i am starting to like the way SiC works. I have just never really liked diamond too much but i do like them when a lot of steel needs to be removed. But once i get in range of a finished blade, i switch over to medium or fine spyderco ceramics. For me sharpening is all about control of the knife and the stone. The more precise, the better. So that is why i don't like using diamonds unless knife is so dull that i know it would take a lot of sharpening to get to a near finished product. But i just recently got my first SiC and it seems to be a nice middle ground between diamond and ceramic. I occasionally think to myself what stones would i buy if i could only have one or two or had a very tight budget. In that scenario, i may go with a dual grit SiC 6 inch stone for about $10 and a single spyderco sharpmaker fine rod for about $10. With those two i could keep all of my knives razor sharp including serrations. Then i could make a homemade strop for about $10, which i have actually already done.
 
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How do you guys judge the hardness with any precision (and in a non-destructive way)? For example if you have a knife with no markings, not even a model number to try and look it up, what do you do?

But even if it is marked with the steel type, or you have a way to cross-reference it via model number, doesn't the hardness vary quite a bit with different batches, or different maker using steel of the same name?
 
... this is probably backwards from most who sharpen...

If I want to hog off metal or set bevels using heavy pressure, it's SiC all the way... but for finishing, I get better edges with diamond, on any steel. Don't know why, but suspect it cuts better, with least pressure, than anything else.
 
jalapeno said:
How do you guys judge the hardness with any precision (and in a non-destructive way)? For example if you have a knife with no markings, not even a model number to try and look it up, what do you do?

But even if it is marked with the steel type, or you have a way to cross-reference it via model number, doesn't the hardness vary quite a bit with different batches, or different maker using steel of the same name?
Click to expand...

You're right. For the most part, unless the maker of the blade specifies the target hardness value for their knives, there's no surefire way to tell, short of actually having it tested on a calibrated hardness tester. But it's generally safe to assume that most mainstream knives from known & reputable manufacturers will fall somewhere in a range from mid-50s - high-50s HRC. When makers do publish such values in catalogs or whatever, you'll see an awful lot of them in the RC 55-58 range, give or take. And after using and sharpening such knives over time, it gets easier to tell when a particular knife might be somewhere outside that range, either too soft (HRC 54 and lower) or very hard (60+ HRC). The softer ones will tend to show a lot of burring issues (burrs very easily; the burrs will be very ductile and flimsy, but they still hold on), and very hard ones will tend to burr very little (harder, brittler, breaking away much more easily), OR sometimes their burrs will be very noticeably strong, very stiff, tough and tenacious to bend or remove by the usual means.

High-end knives in supersteels really should come with published hardness values, else the appeal of the supersteels used in them is somewhat moot, and the maker might lose sales as a result. Same could be said with custom knives, which might vary all over the place with special steels and 'custom' heat treats.

Makers like Case, Buck and Victorinox have all published hardness values in one way or another, over time. All of them will be in that HRC 55-58 range (maybe 56-59), for the most part.


David
 
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