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  1. #1
    Canyonman is offline Hot Rolled
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    Default OT: Can a Ceramic Knife Be Sharpened?

    Hi All,

    Just a quick question, can a Ceramic knife be sharpened? If so, How?

    I picked one up for Cooking, the blade is sharp sort of. It seems to be a thick blade with a rather blunt bevel to the edge.

    Thanks, Ken

  2. #2
    gwilson's Avatar
    gwilson is online now Diamond
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    I don't see why it can't be sharpened on a diamond stone. I've examined so called sharp ceramic knives where there was a flat spot for an edge near the tip,no sharper than a butter knife.

  3. #3
    adama is online now Diamond
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    Yep std diamond wet stone, hand or powered but try not to let it get hot, if it does just let it air cool, dont quench. I read some were theres a optimum grit for kitchen knives, needs some tooth to cut fiburous things, too smooth - sharp isnt as effective.

  4. #4
    kevin johnson's Avatar
    kevin johnson is offline Cast Iron
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    I carry a small Boker ceramic. Boker will sharpen mine for a small fee. Mostly shipping to Colorado and back I seem to recall.

    Boker does not want the owner to attempt to sharpen these knives. I would not buy another as the edge is very brittle. I got several nicks in it dressing a young turkey.

    I have carried it maybe 4 or 5 years and a good sharping would really be in order. Do not carry it in the same pocket as change either. One of these days I will retire it and carry a good steel blade again.

    Hope the kitchen knives are better. I would stay away from bones with one.

  5. #5
    Granite is offline Aluminum
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    For all the high tech, It still comes down to hand sharpening.


    http://www.youtube.com/watch?v=JFnT5INymiY

  6. #6
    mixdenny is offline Cast Iron
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    Quote Originally Posted by kevin johnson View Post
    Hope the kitchen knives are better. I would stay away from bones with one.
    I have a black Kyocera chef's knife. I finally sent it back for resharpening after 7 years of use! They charge $10 for handling and shipping. I love it and use it for everything, even carving turkeys. The black ones last much longer than their white versions.

    Dennis

  7. #7
    gwilson's Avatar
    gwilson is online now Diamond
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    I'm sure your average guy would not have the means to sharpen them. Most of us machinists would. I can't see why a diamond bench stone wouldn't work. If too much time is involved,I'd use a carbide grinder with diamond wheels.

  8. #8
    tomwalz's Avatar
    tomwalz is offline Stainless
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    The ceramics used in these knives are typically much slicker than metal. They cut easily with a blunter edge because there is less drag through the material being cut.

    You need an aggressive diamond shape so that it can grab the material during sharpening.

    You want to leave a blunter edge as the material is often susceptible to spalling or flaking as referenced above.

    The knife material has very low thermal conductivity. If you get the outside hot it will grow. Because the thermal conductivity is so poor the outside (hot) layer will grow faster than the heat can spread through the material to compensate. The can cause crazing and / or flaking on the surface.

  9. #9
    Racer Al's Avatar
    Racer Al is offline Stainless
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    Thanks for posting this, I've had the same question in mind for a while.

    IMHO, I'd get some $12 Horrible Freight diamond sharpeners, I'd hate to hurt my nice DMT bench stones.

    I did a google search for "sharpen ceramic knives", and there is mention of using a stacked paper buffing wheel to put a final hone on the edge with silicon carbide abrasive. Kind of like stropping a steel knife, I assume.

  10. #10
    adama is online now Diamond
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    Diamonds are diamonds even from horrible! Personaly most of the advice i have seen suggests ceramics for cutting softer things, fish, veg and fruit. Not as a carving knive or cleaver!

  11. #11
    tomwalz's Avatar
    tomwalz is offline Stainless
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    Sure diamonds are diamonds but they come in different sizes with different fracture properties. Some wear down to round and some fracture to leave a sharp edge. They can be coated which changes the properties. How they are bonded together makes a big difference as well.

    Pretty fascinating stuff and much of it recently developed.

  12. #12
    Racer Al's Avatar
    Racer Al is offline Stainless
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    Well, that didn't turn out so well.

    I used my older "retired to the shop" DMT bench stones which started out as 300 grit and 600 grit. That's usually enough to put an acceptable edge on steel-based tools.

    The ceramic knife is now dull as dish water. I'm pretty skilled at getting and maintaining an edge on a metal knife, and I used the same technique and angles. Maybe I'm not using the right shape.

    One of my 'back burner' projects is to make stands for my steel and carbide grinders so they are usable. Once that's done, I'll report back if a green wheel for carbide will result in a sharp ceramic knife.

  13. #13
    5thwheel is offline Stainless
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    Get a piece of antler and chip it like an arrow head.

  14. #14
    Randy in Atlanta is offline Aluminum
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    I also have a small Boker that has been back to the factory.
    The knife has an open back and coins that enter will chip
    the blade.

    Bottom line I am not inpressed.

    Does someone else have better luck?

    Randy

  15. #15
    eKretz is offline Titanium
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    Ceramic knives are tricky to sharpen, I have done a couple. Forgive my asking Al, but you say you are fairly good at sharpening steel knives...how sharp are you getting the knives? Can you shave with a steel knife you've sharpened? If not, you're probably not getting the knives sharpened properly. It's not as easy as it might seem. Most of the time when someone uses one of my knives, their eyes tend to open widely in surprise at the ease of cutting, as they tend to slip right thru whatever is being cut. One quick test is to stick a knife into a piece of paper from a page of phone book or similar. When you are holding the handle at the end farthest from the blade in one hand and the paper at the top of the page in the other, a small pocket knife with maybe a 3" long blade should be able to cut down through the paper with its own weight.

    P.S. what angles were you shooting for and what technique were you using?

  16. #16
    boslab is offline Hot Rolled
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    how about diamond paste, like the blue one is 5 micron, and the grey is 1.5, could work?
    mark

  17. #17
    rke[pler's Avatar
    rke[pler is offline Diamond
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    I used to sharpen my Boker carbide knife on a diamond wheel. I have a new Kyocera ceramic blade that I expect to be able to sharpen on diamond as well, but it's going to be a while before it needs it. I bought it in a set with e ceramic vegetable peeler - just wanted the peeler, really, but the knife came with it.

    Racer Al - if you want you can send your ceramic here and I'll take a stab at sharpening it. I've got rotary diamond stuff for grinding carbide tooling, I ought to be able to do something with a zirconium oxide blade. But I understand that Kyocera will do it for $10, might be a better deal with a known result.

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