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Diamonds No Good For Steel?

Discussion in 'Maintenance, Tinkering & Embellishment' started by ejames13, Nov 1, 2017.

  1. FortyTwoBlades

    FortyTwoBlades Baryonyx walkeri Dealer / Materials Provider

    Mar 8, 2008
    After all, metal-bonded diamond is used for grinding aluminum oxide and silicon carbide stones, like mounted grinding points, for shaping them. CBN in the same kind of bond is used for ferrous alloys all the time, and it's not even as hard as diamond is. If that kind of degradation occurred so easily then they wouldn't be worth the expense.
  2. Subwoofer_CPF


    Oct 2, 2014
    Very interesting discussion and those links to the electron microscope images quite enlightening.

    It matches exactly what I find with new and worn in diamond stones. It becomes very obvious when working through grits (especially with new stones) that some of the lower grits still leave some bigger scratches. Eventually those stones improve and work much better.

    With the wear that was visible in the electron microscope images, the grit of each stone becomes finer as the diamonds themselves lose their 'teeth' and smooth out. There is definitely a sweet spot in their life when diamond stones work at their best.

    I would not be without diamond stones, I find them essential and nothing cuts like them. Even the hardest of steels (which other stones don't even touch) will submit to the will of diamond. For re-profiling, it is either the power sander, or a diamond stone.

    As long as you keep the pressure gentle but firm, diamond grit will stay put and cut well. Press too hard and you can lose the surface in a few strokes.
    DeadboxHero likes this.
  3. cbwx34


    Dec 27, 2004
    That's not exactly true either. If you read the history page on EP's site... Ben started as a commercial knife sharpener, and came up with the Edge Pro because "working by hand was too slow". If you ever watch a video where he sharpens a knife, he's very quick. All the "precision" stuff we see now, has come about waaaaay after the EP came along. (Totally a different era in knife sharpening....). o_O
    Med21 likes this.
  4. I actually think that's part of what's gone wrong, in attempting really fast grinding with a full-fisted, shoulder-driven grip on the stone holder. With such a grip and working speed, on a holder which inverts the stone held over the blade (add the weight of the stone and holder, to pressure exerted on the blade's edge), the working pressure of the hone on the steel has got to be way higher than what's best for a diamond hone. That type of setup is part of what felt completely wrong to me, when I was attempting a similar approach with my guided setups; it biases the whole operation toward putting too much force into it, from the shoulder down. Compare that approach to working a knife edge on a bench hone (or any hone laying on a table, of any size) with just light fingertip pressure applied behind the shoulder of the bevel to keep it flush, of which the pressure is much, much lighter on the hone itself. I think that is what diamond hones were meant for, and it's all they need, to work efficiently and quickly.

    danbot and FortyTwoBlades like this.
  5. cbwx34


    Dec 27, 2004
    Sorry, but I think you're grasping at straws here. Go watch some of his videos... it'll refute pretty much all this. :rolleyes:
    annr likes this.
  6. scott.livesey


    Nov 10, 2011
    look, if i sell fords i will find something bad to say about hondas. same sorta stuff
  7. bluntcut

    bluntcut KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Apr 28, 2012
    My takes on Ben's(founder of ApexProInc) statement/assertions in video

    1. Steel can pull out dug-in diamond from substrate/plate.

    True. Basically any type of fixed abrasive types can be pull out. Per psi, deeper penetrating abrasive bit translate to larger torque+pull on cutter, bye bye grit when extraction force is greater than binding force. Actually stones (abrasive in binder) count on this behavior to release abrasive (thereby expose new/sharper abrasives from below). Unfortunately this behavior doesn't end well for non-renewable grit in diamond plate.

    2. Diamond should only be use to sharpen carbide(cemented); ceramic(composite) blades/tools.
    False. The implicit 'true' part - diamond is excellent for shaping carbide & ceramic. This statement contradict itself by excluded/'only' steels with non-zero of hard carbide volume%, thereby invalidate this statement.

    Ben generalized conclusion is unfounded via deductive reasoning of public high volume sharpening (100+ knives a day). A faulty conclusion because conditions on #1 must be met before pull-out occur. Hidden (or implicit) within 100+ knives/day - certain % knives have hardness below 55rc and while using same pressure, diamond will penetrates too deep, lead to diamond pull out.

    Skilled sharpeners would quickly (from feedback) cognizant of low hardness and adjust pressure appropriately - thus avoid #1. Yeah wisdom... newb sharpeners shouldn't offers public sharpening service - it would be comical to see these sharpeners (w/o diamond/cbn) try to sharpening bcmw 69+rc knives.

    Please keep in mind the difference between instances and generalization. For examples, metal hogging scenarios/instances where high pressure (i.e. deep digging) is a given = abrasive consumption is very fast, so diamond offers low value due to higher material cost compare to other abrasive, such as ceramic/AlO/SiC. See - even within these instances - beside cost/value we also need to assess functional effectiveness.

    ApexPro sharpening contraption (I've one) is prone excessive pressure in sharpening stroke because minimum down force = weight of apex arm + stone; normalforce = minforce + humanforce. psi = force/bevel area, so sharpener need to adjust optimal(at least working = non-destructive) psi per edge geometry and steel attributes (CV & hardness).
    Chris "Anagarika" and maximus83 like this.
  8. danbot

    danbot Gold Member Gold Member

    Oct 31, 2009
    My takeaway from all this:
    Diamond hones should not be used on guided sharpening systems unless you are consciously using the lightest pressure possible throughout the sharpening process, or damage to the hones may occur.
    Gottcha! :thumbsup:
  9. scott.livesey


    Nov 10, 2011
    diamond stones are tools and need to be used properly. SiC and AlOx stones have issues also if not used properly. the Norton stones I own even vary one to another as far as how much force to use, how much oil or water to use, how often to refresh or flatten. I have issues when I try to sharpen store bought knives as they are a lot softer than the ones I make and the steel behaves so much differently.
  10. HeavyHanded


    Jun 4, 2010
    "Over 100 knives a day" with any manual method those folks would have repetitive use injuries. In a ten hour day that's a knife every 6 minutes including QC. If using an EP I'm assuming the knife in question is too high a value to use a belt system, 6 minutes is blazing as a daily average on higher dollar knives. Your conventional stones wouldn't be staying flat and your diamond hones would (maybe) be worn out rapidly - like the John Henry of sharpening:

    John Henry said to the captain

    A man ain’t nothing but a man

    Before I let that powered grinder beat me

    I will die with a stone in my hand
  11. FortyTwoBlades

    FortyTwoBlades Baryonyx walkeri Dealer / Materials Provider

    Mar 8, 2008
    That's where things like Tormek-style wet grinders come into the equation. Faster than manual, cooler than dry-grinding.
    Mo2 likes this.
  12. cbwx34


    Dec 27, 2004
    I'll say what I said before... I think you're looking at it thru the lens of today. He was sharpening knives on a commercial route... not knives that were of high value, and came up with the EP as a "faster than hand sharpening" method. The EP Pro was specifically designed to eliminate "dishing"... allowing the whole stone to be used and remain flat. It could be done quickly because he sharpened at a common angle... one or two stones, and quick debur (see videos). Light pressure, minimal effort, designed for comfort... all part of the package.

    Today we have the view of: high dollar knives... must tape up.... carefully set angle... 1/2 dozen stones process (minimum)... OMG one side is 1/2 deg. wider than the other, must start over.... :cool:

    As for the... too much pressure caused by the setup, mentioned in the other threads... then, if this were true, if I took a knife and made a tip repair (no EP)... putting a spine or edge 90 deg. on a diamond stone (very small surface)... can I not control the pressure to prevent destroying the stone?
  13. HeavyHanded


    Jun 4, 2010
    It looks like the EP pro uses waterstones too, or ceramic as an option? I can see where you might blast through some knives with a down and dirty approach, but wouldn't it still be faster freehand if top end results aren't an issue? Working a 10" stone with two hands and a need for speed will leave you with less wear and tear maybe. No getting around the smaller stones and shorter pass of these guided units. I guess I just need to watch one or two videos.

    Definitely getting off topic here...
  14. Diemaker

    Diemaker KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Apr 28, 2017
    From what I have learned in the last 20 years diamond cuts steel just fine if you can control the heat, which is not an issue hand sharpening. If the diamond is pulling out of the bond then it was poorly bonded. The diamond crystals will sheer off before pulling out with a proper bond. Diamond crystals are like anything else, there is cheap low quality diamond and expensive high quality diamond, there are also differences in tougher vs harder diamond crystals. The high quality stuff is far superior and costs around $1-$2 a gram. A 1"x6" plate would have less than a gram of diamond. If my supplier did 1"x6" single layer plated bars they would charge me around $100 each in quantity, with me supplying the blanks.

    Other than cheap poorly bonded diamond being the problem then I would guess it would be too much pressure for the amount of surface area being ground. The most dangerous time for the diamond would be grinding a fine edge, such as just starting a new bevel at a different angle, be real gentle at first. This advice applies for any grinding medium, be gentle until you have some surface area to distribute the load to minimize wear on the abrasive.

    The last thing I would like to add is that I am pretty sure Ben did not form his opinion about diamonds sharpening knives using high quality diamond abrasives.
  15. maximus83


    Nov 7, 2011
    From what I've seen here on BF, and in firearm forums I participate in, and in my work in a software company where I talk to customers: there's a tendency for folks to draw firm conclusions based on insufficient evidence. Example: some guy buys a Glock 19, has extraction problems with it, brass to the face. He gets a replacement, same problem (this is known to occur with *some* Glocks, it's not a fake issue). Then based on his sample of 2, he makes a huge leap and trumpets it all over the Internet: all Glocks have unreliable extraction.

    So if the guy in the video had a bad experience sharpening with diamonds in a very specific type of setup, he concludes ALL diamonds must be bad for sharpening. That conclusion is not necessarily warranted unless he does extensive testing with different diamond abrasives, a variety of sharpening setups, etc.
    danbot and FortyTwoBlades like this.
  16. adamlau


    Oct 13, 2002
    ^ I disagree. Diamonds are bad. Very bad :thumbsdown: . And Glocks have unreliable extraction. Super unreliable :thumbsdown: . lol...It's Friday :thumbsup: . Diamonds are fine by me. Else, I would not be looking towards a bonded diamond stone as my next accessory buy.
    Mo2 likes this.
  17. wvdavidr


    Mar 21, 2007
    Ben did say (and has told me) that he tried every diamond plate in the business. I asked him for suggestions on DMT vs. Atoma. He said both failed his testing. He said something that made sense to me: He has customers who sharpen hundreds of knives per day. He can't charge $50+ for a diamond plate that won't last until lunch. I don't think he drew his conclusions from those plates that HF Tools sells.
  18. adamlau


    Oct 13, 2002
    What? Hundreds of knives per day on the EP o_O ?
    HeavyHanded likes this.
  19. HeavyHanded


    Jun 4, 2010
    This is where I need more info. At hundreds of knives/day, any abrasive is going to take a poop. Waterstones will dish, diamonds fall out, ceramics and vitreous stones glaze and/or dish. If you were doing hundreds of units in a shift on a modern ceramic belt, one belt wouldn't make it to your lunch break.

    Has anyone done 100 units in day (let alone multiples) with any of the stones offered as a package? Not trying to sound like a wiener here, but these numbers as a daily on a durable surface just don't add up with exception of waterstones which would require too much periodic flattening to keep pace with the output numbers. You'd need a support team to stage your knives and keep you in good supply of conditioned stones, whatever the composition. I can't get the image of John Henry out of my head, and that's just one day, not the challenge of a lifetime...
  20. maximus83


    Nov 7, 2011
    A famous statement popularized by Carl Sagan but really just synthesizing the idea from earlier scientists: Extraordinary claims require extraordinary proof.

    Some key statements from the video:

    Based on this, he's making two rather extraordinary claims:

    1. Diamond abrasives should never be used on steel, at all, of any type.
    2. Everyone in the USA who sells diamond abrasives for sharpening believes item (1) to be true, and is lying about it in order to sell diamond abrasive products.

    I'm still waiting for the part where we get the extraordinary proof. If he had limited his comments to something like, Every type of diamond abrasive I tried with my sharpening gadget failed, then no problem. That would be believable, and we could drill into that. Maybe there's something about the device itself, the way it's used as David suggested, which impacts on how the diamonds work. But because he's being so universal with his claim--diamonds don't work on any steel, at all, and everybody who sells them is being misleading--he's going to need to offer extraordinary proof. There are a lot of reputable companies selling diamond abrasives for years all over the world, DMT is just one. And a lot of commercial and retail customers (including myself) who believe based on firsthand usage that diamonds sharpen steel quite effectively. The burden of proof is on him, since he's making this broad brush claim. I would want to see lists of all the diamond abrasives he has tried: which brands, what grits, what sharpening methodology he used, which steels he used them on, how many knives he sharpened, photos of the blades and the stones after the alleged tear-out of the abrasive occurred, etc. Did he test them only on his machine, or did he test using other sharpening methodologies, etc? We have none of that information here. All we have is some untestable and unconfirmed statements...."Ben said....Ben told me....I've tried every diamond in the US." From the guy who wants us to buy his gadget. Proof please.

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