Differences between diamond stones and Arkansas stones

T

That_Knife_Guy

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I have been looking at buying the KME sharpening system and seen that the deluxe is by far the better option to get even without the arkansas stones. However this had me wondering... are Arkansas stones better for certain steels or do they have overall advantages?
 
Arkansas stones cut more slowly and leave a finer finish than diamond stones. In general. The most coarse Arkansas stone, the "soft" leaves a finish that's roughly like 600 grit ANSI. It cuts much more slowly than man made stones like Aluminum Oxide or Silicon Carbide.

Conversely a "fine" diamond stone is rated at roughly 600 grit, but leaves a finish that's much, much more coarse than a soft Arkansas. But don't confuse the finish "look" with sharpness. The edge from a fine diamond stone can be hair popping sharp.

In my not so humble opinion, Arkansas stones are only good for a few things:
1. Nostalgia.
2. They are all unique specimens of stone, and might be interesting to look at, and be beautiful and/or collectable to some people.
3. They produce good edges on high carbon steel, or steels with very few carbides. They are slow on almost any kind of stainless steel, especially if the steel is fairly hard.

I still think there are way better choices for carbon steel. But the combination of nostalgia, looks, and them being known to work (albeit slowly) on carbon steels, might make it fun or interesting to own and use them.

I personally have no use for them and consider them to have harmed my sharpening journey due to them being so incredibly slow.

Brian.
 
Well "BGentry" what you've said about Arkansas Stones ( novaculite) I'm in total agreement with you. I've owned over the years and stilll own a few of the "Blue-Black" grade and the "opaque" grade which both are about the hardest Arkansas Stones you can get. And I find them to be only good for fine tuning an already super sharp edge>> you've hit the nail on the head as far as Novaculite being a very slow abrasive to work with. Also it's just not hard enough or aggressive enough to take on some of these newer/better supersteels.

Now I have heard some good things about the higher grades of the Belgium Razor Stones ( coticules) but they are also mainly recommended as a finishing stone or a stone that enhances an edge that's already considered sharp.

In the past two years or so I've pretty much only used Spyderco's ceramic stones and diamond stones made by three different companies i.e. 3M, DMT, & Norton. Because many of the newer steels I've been playing with it seems like diamond is the only thing that will reprofile it or remove hard use dings as good as it does. Some of these newer/better blade steels are so tough and hard that unless you use ceramic or diamond you're just wasting your time IMO. But I have no problems using natural stones for fine finish work.
 
I used Arkansas stones for many years, but would not opt for them in a sharpening system like a KME.

However, they are good as fine finishing stones for certain steels. I've been considering getting another for finishing some carbon steel blades and simple stainless blades I have.
 
I've liked Arkansas stones for finishing tasks at medium to polishing grit finishes on simpler steels like 1095, CV or 420HC, all of which fall into that minimal/no hard carbide category. If the steel contains very much of the harder carbides, like chromium carbide, tungsten carbide or especially vanadium carbide, Arkansas stones will work very, very slowly, if at all. All of these carbides are essentially 2X - 3.5X as hard as the natural abrasive (novaculite) in Arkansas stones, which itself is only marginally harder than the most basic of carbide-free cutlery steels anyway. Think of 440C as being at the threshold of the carbide-laden group, with a fairly significant amount of chromium carbide; some makers' versions of 440C will make sharpening difficult for Arkansas stones.

I've not liked Arkansas stones for heavy grinding or rebevelling tasks on most any steel; they're just too slow for that, and many other manmade stone/abrasive types can handle that task much more effectively, such as aluminum oxide, silicon carbide and diamond stones.

Per the thread title specifically, the most relevant difference between diamond stones and Arkansas stones comes down to this:
  • Diamond hardness = 7000 (Knoop scale)
  • Arkansas (novaculite) hardness = 825 Knoop
That means diamond is ~ 8.5X as hard as the natural abrasive in Arkansas stones.

And most cutlery steels lacking hard carbides won't be very far below the hardness of novaculite, with many in the 600-800 Knoop range. Hence, still relatively slow-grinding on even the simpler steels, though still useable enough at lighter maintenance & upkeep sharpening of those simpler steels.

As for the carbides in popular wear-resistant steels:
  • Chromium carbide (440C, 154CM/CPM-154, ATS-34, D2, ZDP-189) = ~ 1700-1800 Knoop
  • Molybdenum carbide = ~ 1800 Knoop
  • Tungsten carbide = ~ 1800-1900 Knoop
  • Vanadium carbide (S30V/90V/110V, etc.) = ~ 2600-2800 Knoop


David
 
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if you have any D2, or other high carbide steel, stick with the diamonds (or SiC). the softer steel will work fine with Arkansas.
 
In almost any steel, there is no advantage to Arkansas stones, unless you own a quarry and are trying to sell them.

Synthetic silicon carbide, Cubic Boron Nitride, and synthetic diamonds have surpassed them in hardness, economy, speed of sharpening, and availability ever since there discovery and subsequent use.

In the fur trade back in 1823 or so, if you had an Arkansas stone, you were pretty hot manure compared to the other fur traders with files though.

Also, while the KME does a good job at sharpening half a knife, you may consider the Wicked Edge, which sharpens the whole knife at once, as well as steeper, more sliceable angles -15DPS or less (owned both, sold KME, kept and still use Wicked Edge). May have to buy low angle adapter though (I think another $75 or so) to get those angles. Hope this helps a bit.
 
I have some older knives that might fancy my Arkansas stones, but I realize I probably need to move on from the system that taught me how to sharpen knives. I recently bought a Sharpmaker that I'm learning, but I'm keeping my oil stones around. I think the stock Sharpmaker is ceramic but it seems I might need to find some diamond to help me out.
 
I still use Arkansas stones cause they work with my Old Timer Knifes and I have man made options for anything else.
 
The most coarse grade Arkansas is not the soft. It is the Washita at 500 grit. I have applied diamond slurry to this stone and it boost the
cutting ability slightly. Not anything close to a fine India. I think keeping a coating of 200 grit SiC paste on one side of this stone would bring out it's best performance. Still, not the level of a India but about as close as you could get, if you wanted to use just this type stone. Still, as
some have stated these stones are for simple steels & simple stainless. Think kitchen knives. Then the very hardest grades work well for straight razors and double edge blades. DM
 
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