Sharpening Ceramic Blades?

J

JD Spydo

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Nov 20, 2004
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We have a discussion going over at the other Forum ( Spyderco.com) about ceramic knives and there has been some talk on the difficulty and uncertainty about sharpening them. I've personally only owned one ceramic knife and personally I didn't like it all that well. But I thought I would raise the question to maybe learn more about ceramic knives and what are some of the better ways to sharpen and maintain them.

So what do you guys use to keep ceramic blades sharp? I do know that "diamond" tools are about the only abrasives you can successfully use to sharpen a ceramic blade. So which diamond sharpening tools would you all recommend? I've heard that DMT has some good benchstones for ceramic blades. Any other companies make sharpening tools for ceramic blades?

Also while we are on the subject I'm also wondering who makes the better quality ceramic blades? I've heard that Boker makes some good ones but I'm sure that there are other players in the game at this point. Also I'm wondering what the manufacturers recommend for sharpening their ceramic blades?
 
I have one Kyocera ceramic paring knife, the $15 model off Amazon, it was an impulse buy. I have found that Sic will rough it quite well but you need diamond to take it any farther. What I use are the EP Matrix resin bond diamond stones, disclaimer- I make them. The advantage of resin bond with ceramic is the bond is not aggressive, which should help reduce the tendency of microchipping. When properly dressed the diamonds should just poke out of the resin limiting the depth of the scratches. With a good brazed bond the diamonds can be 70% proud of the bond, which is why they are so aggressive. I also have found that edge trailing strokes are very important to reduce or eliminate microchipping and that micro bevels are to be avoided like the plague, again because of microchipping. I have only sharpened this knife with my guided sharpener set at 21 degrees and inspect what is happening with a microscope, I don't think I would want sharpen it at any less of an angle. Once you are properly set up and have a little experience I find that ceramic is much faster to sharpen than steel, the diamonds cut it real well, magnitudes better than steel.
 
Well thank you for your quick reply "Diemaker" :thumbsup: I'll definitely have to check out this EP Matrix resin bond you speak of. But I have a couple of questions right off>> first of all what do the manufacturer's of ceramic knives recommend for sharpening the blades they make? Also are well known companies like DMT trying to market anything at this time that would be made specifically for ceramic knives? You would think that as long as ceramic knives have been on the market place that by now some company would try to fill that void.

Now this EP Matrix set up you speak of >> is that something you concocted just for ceramic blades or is that something that could be used on a wide range of applications? Also I don't know if tungsten carbide is harder than most ceramics or not. If not then I guess diamond is the only thing that will work to sharpen ceramic knives?
 
Diamond is what works for ceramic really, really well. Diamonds love ceramic, way more than steel, and will last much longer cutting ceramic than steel. Any diamond plates or stones will work, there is nothing special for ceramic knives, other than a less aggressive bond is preferred. If you are doing enough ceramic and using plated diamonds then I would dedicate new ones to ceramic blades only, they will work much better if they never cut anything else, especially steel.

I am only aware of ceramic knife companies saying to send the knife back to them for sharpening. I figure much of this is because of microchipping, which really is a big deal and happens easily. I saw a Youtube video of a company, I think Kyocera, showing how they sharpen customers knives. They just used 18" ish rotating diamond plates with a little water and freehanded it in a 2 grit progression.

I concocted the resin bond diamond to polish the radiused edges of my custom stone, quartz, and ceramic switchplates about 15 years ago. Over the years I ocasionally heard from EP that the polishing tapes were a PITA because they didn't last very long and often failed because the knife cut into them. So I prototyped a bunch of "stones" using what loose abrasives I had on hand, diamond, Alox, and Sic. This is where the new one piece machined polishing tape holders came to be as well, I wanted some for myself when testing the polishing tapes against my resin stones. After EP got my stones and tested them they said they were not really interested, but they really loved the machined tape holders. After a few months of the stones sitting around EP found they actually kind of liked the diamond resin stones and started ordering them. So in a way they were developed for ceramic but we found out they work on any hard material. For softer steel, rc50ish and less, the diamonds are really no better, or don't work as well, than Alox stones.

Since microchipping is such a big deal I think diamond is several levels better than anything else for sharpening ceramic knives. You want the hardest, sharpest abrasive for ceramic and that is diamond. Since it is so sharp it cuts more freely, putting less pressure on what it is cutting.
 
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So, on ceramic knives put a 20-21* angle on it and use low pressure when creating the bevel. DM
 
Just a few passes on the Ken Onion Worksharp with the diamond belts, and me ceramic knives are good to go. 3-4 minutes at most.



Stitchawl
 
stitchawl said:
Just a few passes on the Ken Onion Worksharp with the diamond belts, and me ceramic knives are good to go. 3-4 minutes at most.



Stitchawl
Click to expand...

Yes. I have a cheap harbor freight ceramic paring knife that was never very sharp out of the box. A few minutes on the Worksharp with the diamond belts, and it was cutting hairs.
 
David Martin said:
So, on ceramic knives put a 20-21* angle on it and use low pressure when creating the bevel. DM
Click to expand...
If using the same stones on the same blade material they yes. I think I have read that the physical charceristics of ceramics can vary more than steels, so just saying ceramic can have a very wide meaning. I too am very interested in hearing how much of a difference there is in the ceramic of different ceramic blades. I know Kyocera makes at least two ceramics for knives with large differences in price between them. They also make ceramic inserts for cutting hard steel in conditions where sintered carbide fails. There are also solid ceramic end mills for very narrow applications.

If you are going to sharpen ceramic knives it is my opinion that you have to inspect the apex with a good microscope to see what is happening. I have formed this opinion by thinking I have done a great job sharpening my ceramic knife and found horrible microchipping under the microscope, lots of chips .001"-.002" back from the apex.
 
One of the problems with sharpening ceramic blades is the fact that they don’t drag a burr. So you don’t when your ground bevel is extending to the apex. I have a Kyocera battery powered ceramic knife sharpener. It doesn’t work worth a sh*t. Hundreds of passes on the Diamond wheels yield no results. The technical hot line is worthless.
I finally sent the knives in for sharpening. They (Kyocera) do a good job on sharpening.
 
Then sharpening ceramic blades leaves most of us out as I don't have a decent microscope to examine the edges. DM
 
J JD Spydo
For polishing ceramic knives i use Paper Wheels with diamond compounds.
With these you can get edges that are hair whittling from root to tip, which is noticeably sharper than straight from factory.
Best ceramic knives i have found so far are made by Forever and Kyocera.
 
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