Diamond Impregnated Sharpening "Stones"...Whats with the negative opinions?

Discussion in 'Cooking Knife Reviews' started by jeremy r, May 30, 2014.

  1. jeremy r

    jeremy r

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    First time post here!

    Im curious why people hold the opinion that the diamond "stones" made by companies such as DMT are inferior to whetstones and/or damaging to knives. I've heard mention that they will scratch your knives and possibly ruin them but I dont see a difference compared to a whetstone. They both use abrasives to remove steel from the edge of your blade...

    If I can use them in tandem with a strop and get my knifes sharpenough to shave forearm hair than is there really and reason not to use them?

    I ask this because I really like the eas of use ie: no soaking in water, no flattening, lasts for a very very long time.

    Thoughts?

    Jeremy R
     
  2. grande

    grande

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    All right, I'll bite.
    Diamond has a reputation for being much more aggresive than 'conventional' sharpening methods; thus scratching your knife surface, eating steel more quickly, and compounding rapidly any minor errors in edge geometry.
    Diamond steels have a decidedly iffy reputation, although they definately have their devotees. Personally i wont let them touch my knives.
    If you like them, who's to stop you? Most people, i think, kind of cobble together their sharpening kit, rather than buying it all at once.
    I cant answer for how they work for super fine sharpening, i've never actually heard anything against the "diamond stones" just the steels.
     
  3. jeremy r

    jeremy r

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    This is exactly what confuses me.  I thought that the aggressiveness of a stone was measured by its grit.  Therefore I have trouble understanding why a 1,000 grit whetstone and a 1,000 grit diamond stone would be any different...
     
  4. knifesavers

    knifesavers

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    Grit is about the abrasive particle size and not the way it will cut metal or break down as it does. 

    Grit is a part of how a given abrasive will work but not all.

    Arkansas stones for example have no grit rating. They are graded by density , soft hard, black, and translucent and all act different.

    Jim
     
    Last edited: May 30, 2014
  5. phatch

    phatch Moderator Staff Member

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    Diamond stones are very good for certain things. Thinning or reprofiling, they're the best tool for the job. I don't mind them as a step in my sharpening arsenal, but as noted, ,they tend to amplify poor sharpening technique and the widely available grits aren't well matched to lots of routine kitchen type sharpening. 

    It's much easier to keep a sharp knife sharp with touch up maintenance than it is to go through the whole gamut of grits every time further limiting their usefulness. 

    I've used a heavily swarfed diamond stone for a lot of years in my kitchen sharpening arsenal. I've drifted away from it the last year or so as I'm finding it less and less useful for routine sharpening tasks. 
     
  6. rick alan

    rick alan

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    If you have a cheap set of German knives ridiculously thick all around what difference does it make really, except your diamond hone won't last very long.  Even DMT's have a problem here.  The nickel typically use to bond them isn't very strong, and the harder the steel the easier they rip out.  This is greatly exaggerated with a round hone because of the extra pressure exerted at the smaller point of contact.

    I had a 1x3" fine diamond hone that I used for 25 years, but I only used it to finish sharpen a very thin and soft 9" stainless blade.  Actually I went from a course (relatively speaking) India stone (an unnecessary step really but at the time I thought you were suppose to always start with a fresh edge), to the diamond, and finished on a soft Arkansas.  I hadn't used it for a while when one day I pulled it out to see what I could do with a cheap ceramic parer I'd picked up.  It tore out most of what was left in the hone just touching up the edge.

    Atoma diamond hones are bonded with a different process and are much more durable than DMT's, and some pro sharpeners do use them for thinning, but never finishing, unless they're hacks.

    If you want real fast cutting and great finish both then cubic boron nitride (CBN) is the way, but at this time it is only available in slurry and compound form for stropping and lapping, no one is making stones with it to my knowledge, and it does have a problem in that it reacts with certain metals which can quickly reduce its effectiveness, so you probably won't see it in whetstone form.

    Rick
     
    Last edited: Jun 1, 2014
  7. foodpump

    foodpump

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    Whoa, hold on there.

    There are diamond "stones" like 8" x 3" or larger, and there are hones, and then there are diamond "steels".  I don't like the diamond "steels" because it is an abrasive and a steel was never designed to abrade metal, only to straighten out the edge or to burnish an edge.  A diamond "steel" will abrade a fresh edge, but I have never gotten a consistent bevel with this contraption.

    You can get diamond stones in a wide variety of "grits", and DMT makes them as fine as 12000.  They work very well, and the finer diamond stones will put a mirror polish on every steel I've come across.

    Eh.. whatever floats your boat when it comes to abrasives for sharpening, as long as it works.
     
  8. jeremy r

    jeremy r

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    I'm referring to the 3x8 inch diamond stones that serve the same purpose as a whetstone.

    I'm surprised to hear someone mention that they wear out quickly seeing as how they are made of steel and diamonds as opposed to rock.
     
  9. phatch

    phatch Moderator Staff Member

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    The diamonds don't wear out, but they come unbonded from the substrate. A diamond free to move will not benefit you in sharpening. 
     
  10. mike9

    mike9

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    The diamond stones like DMT are great from coarse to XXX-Fine.  There is a time and place for a diamond steel, but it's not an everyday kind of thing.  It's more like an emergency repair kit when you're edge is gone and you don't have stones on hand.  Like the fishing boat, or camp.
     
  11. foodpump

    foodpump

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    Mmmm... Well that's something to think about.

    Then again, I know a lot of woodworkers who use diamond paste (diamond particles suspended in mineral oil) as their sharpening medium. Some spread a drop on a cast iron surface, some on a hunk of mdf or plywood.  Places like Lee Valley have been selling this stuff for years now, so it is well respected in the woodworking and metalworking trades.
     
  12. phatch

    phatch Moderator Staff Member

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    The paste does restrict motion some. And you can sand with loose sand. But it's more efficient in more structured formats. The past provides some structure, but it's more a slow refining thing than aggressive.
     
  13. rick alan

    rick alan

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    I mentioned much earlier about diamond bonding and the problems.  Apparently other things need spelling out also.  Lapping is the use of an abrasive that is imbedded in a hard substrate, but a substrate which is much softer than the abrasive, and also softer than the material being cut.  In stropping a very soft substrate is used, limiting the application in many ways but having it's own advantages.  Pastes and oil-based slurries are typically used in lapping on metal and even plastic surfaces, while water-based slurries are typically applied to strops of leather, balsa, felt, paper, etc, though waxes are also used here.

    I did not know that DMT has a 12K stone now.  True it will leave a polished sheen but, by the nature of diamonds cutting characteristic, the edge will typically not be as durable, nor possibly cut so well, as what is produced by other abrassives.  Diamond gouges/scratches, whereas other abrasives  tend to more smoothly skive off material.

    Rick
     
  14. foodpump

    foodpump

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    O.K. ...

    Truth be told, I've never tried out the pastes, but I do like my diamond stones.  I don't know about "wearing out", but diamonds do fracture and break down.  Ask any jeweler and they can confirm that just knocking a diamond ring against a cement wall can fracture and chip a diamond.  Same with the stones, they eventually fracture, break down, and fall out of their bonding.  Still, for the courser stones I like diamond stones because they cut very aggresively don't make as much a mess as water stones, and don't need flattening.  But for the finer grits I like water stones.
     
  15. lennyd

    lennyd

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    One thing I learned from years experience using and selling abrasives in both auto collision and industrial use is that any abrasive is as abrasive as it's largest particles and these are often of a larger size than the micron or grit ratings we use to determine how coarse or fine the abrasive is.

    On wet sand paper it was not unusual for the micron size of a larger particle in a fine paper to be nearly large enough to have been used on 1-2 sizes more coarse paper.

    It's the manufacturers ability to hold close tolerance of the rogue particles being kept to a minimum that sets the better makers apart. And it's not always the big names that do the best job of keeping grit sizes uniform.

    When first learning about whetstone's etc I found it very interesting that there are similarities and also differences from the sand paper standards I was previously familiar with.

    There is still different standards used (jis etc) by the various brands and though like many products the Japanese and western European made products just seem to hold the tolerance of particle size a bit tighter etc.

    The computer I have all the links to the information on is of course down at the moment, but it's all on the net and a simple search of sharpening stone or sand paper grits, tolerances, and standards should get you going.

    I bring this up because I was told (but never confirmed or refuted because it didn't apply to the products I was involved with) that there are some issues with diamond abrasives holding tolerance due to the much higher costs for the raw materials except for the highest priced brands. That would make sense, but it's a broad statement without any substantiation or proof, but the rep I got it from had nothing to gain from it either.

    Maybe someone else can expand etc.