Sharpening a Ceramic Kitchen Knife

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stitchawl

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Jul 26, 2008
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Title says it all... I'm about to try refreshing the edge of my first ceramic blade, an 8" kitchen knife. I won the knife on an E-bay auction for 80 cents, so no great loss if it doesn't work, but I think it will be an interesting experiment.

I'm going to spread 0.5 micron diamond paste on a 8"x14" rectangle of VERY compressed water buffalo hide. I chose this substrate because it feels as dense as MDF (you can just barely bend this leather,) yet the diamonds should still be able to get a purchase in its surface. A few hundred edge-trailing strokes, then I'll switch to 0.25 micron paste for a few hundred more. I'm going to control the angle using a DMT aligner clamp running along side of the leather, set to a 15 degree angle. I'd like to go more shallow but I'm afraid of edge chipping in use.

Whaddayathink?


Stitchawl
 
I just touched one of my cheapo ceramics up with the underside of a coffee cup, worked like a charm. I haven't used a ceramic belt on my 1x30, but I might try that next time it needs touched up and see what it does, if anything.

A few hundred??? You have way more time and patience than I do. :p
 
stitchawl said:
Title says it all... I'm about to try refreshing the edge of my first ceramic blade, an 8" kitchen knife. I won the knife on an E-bay auction for 80 cents, so no great loss if it doesn't work, but I think it will be an interesting experiment.

I'm going to spread 0.5 micron diamond paste on a 8"x14" rectangle of VERY compressed water buffalo hide. I chose this substrate because it feels as dense as MDF (you can just barely bend this leather,) yet the diamonds should still be able to get a purchase in its surface. A few hundred edge-trailing strokes, then I'll switch to 0.25 micron paste for a few hundred more. I'm going to control the angle using a DMT aligner clamp running along side of the leather, set to a 15 degree angle. I'd like to go more shallow but I'm afraid of edge chipping in use.

Whaddayathink?


Stitchawl
Click to expand...

Here is a link to some good info
https://www.bladeforums.com/threads/forever-sc-16wb-ceramic-knife.1206014/

Also see the yellow stickies at the top of the Tinkering forum here about sharpening with paper wheels.
I don't have much experience sharpening ceramic. It seems very light pressure and a lot of surface feet per minute (powered paper wheel with diamond grit) is the way to go.
 
View attachment 839405 View attachment 839406 View attachment 839407 I have a Kyocera ceramic knife sharpener. I doesn’t work worth a shyt. From what I have read, you’re supposed to sharpen the ceramic edge on a fast coarse wheel. Hand sharpening is a pain because the edge doesn’t drag a burr. The material just falls away. You never know how you are doing especially on a black blade.
Blades from the factory tend to be a little obtuse because a blunter blade is less prone to chipping. I have been happy with Kyocera’s sharpening service, but they don’t do it themselves. They farm it out. I sent them a folding Boker, and they did an excellent job. They even reduced the included angle.
I use my ceramic blades as finishing steels for metal blades. They are as hard as a rock and as smooth as glass. If I cut an apple with a ceramic blade that has been used as a steel, it will turn brown because of the iron residue left on the blade.
 
Give a try and let us know how it works. I've used a guide and sharpened cheaper ceramic knives on silicon carbide stone, wet/dry, diamond plate, diamond lapping film.

Have been able to get a paper slicing edge that would barely shave some arm hair, but not much better than that.
 
HeavyHanded said:
Have been able to get a paper slicing edge that would barely shave some arm hair, but not much better than that.
Click to expand...

I'm starting with an edge that will slice copy paper, but it doesn't feel smooth. I have another small ceramic knife, made by Kyocera, that arrived sharper than most other knives I've bought, and stayed that way for several months of daily use. Now, it too will only slice paper, and it is because of this knife that I decided to try to sharpen the other one... first. If I notice marked improvement, I'll put it to the block too.

EDIT: I just reread what I wrote, and could only shake my head in amazement. What kind of KnifeKnuts are we, that we think cleanly slicing paper is a dull knife! LOL!


Stitchawl
 
I agree with using edge trailing strokes and use very light pressure. The last time I sharpened my cheapie Kyocera paring knife I stopped at 8 micron because my 5 micron diamond "stone" left some chipping on the edge, while inspecting with the microscope. I think the sharpener was set at 21 degrees. It still makes it hair popping sharp, enough to consider a new Kyocera dull. Ceramic being so hard you don't need to go so fine on the abrasive, the diamond won't scratch as deep as it does with steel.
 
Please let us know how it works. I haven’t been successful with using DMT C, F, EF, scrubbing. Probably need to be patient & edge trailing only with barely a touch.
 
Chris "Anagarika" said:
Please let us know how it works. I haven’t been successful with using DMT C, F, EF, scrubbing. Probably need to be patient & edge trailing only with barely a touch.
Click to expand...

Will do. I've just ordered some fresh diamond compounds, so won't begin until they arrive.


Stitchawl
 
Another option to sharpen ceramic knives, and a question:

I have a Worksharo ken onion, and ordered their diamond belts kit. I have an old harbor freight ceramic paring knife that was never very sharp out of the box. I used the coarse belt first, made several (5x) passes at 20 degrees per side, then went to the fine belt. The knife is now sharp enough to shave hairs on my arm (though not nearly as well as the video above).

One thing I noticed- cutting through an apple still takes a bit more effort than one of my Victorinox paring knives, which are sharpened at 15 degrees per side and are much thinner. Is this likely due to the angle, or is it just the nature of ceramic knives? Can you sharpen a ceramic knife at 15 degrees per side, or is that too thin and likely to cause breakage of the ceramic?
 
F308gt4 said:
(...) One thing I noticed- cutting through an apple still takes a bit more effort than one of my Victorinox paring knives, which are sharpened at 15 degrees per side and are much thinner. Is this likely due to the angle, or is it just the nature of ceramic knives? Can you sharpen a ceramic knife at 15 degrees per side, or is that too thin and likely to cause breakage of the ceramic?
Click to expand...

I've noticed apples are a great test subject for evaluating cutting geometry. A lot of that is due to an apple's tendency to clamp down on, or pinch, the blade while cutting. I eat a lot more apples than I used to, simply because (well, mainly because) I've learned so much in cutting them with different knives. I have a lot of fun trying out different knives with them, so I try to eat an apple every day.

The Victorinox paring knives are awesome with apples, in their own right, and I've even thinned mine some more, likely down to less than 12.5° per side at least, at the edge, with some thinning behind the edge as well. Without a doubt now, I'm convinced the thinness of the blade makes the greatest difference. Secondarily, I've also noticed the finish (coarse or polished) on the blade and bevels will help also, in reducing (or increasing) friction in the apple, while cutting it. The shape of the edge (v-bevel or convex) makes some difference too. Very crisp shoulders on a V-bevel can dig in and get bound up as the apple pinches the blade (I've noticed this in cutting cardboard as well). A polished & very thin convex, on the other hand, will glide right through it with ease.
 
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UPDATE: It's a win!
I received my diamond pastes... just cheap stuff from E-bay, and applied them to compressed leather bench strops. (Note: I chose leather because I have lots of it at hand, and didn't feel like taking a trip to the Home Center for MDF boards.)
I started with 2.5 micron paste and stropped an 8" unbranded ceramic kitchen knife for about 4-5 minutes. Nothing really excessive. I then switched to 1 micron paste and repeated the process. Then I loaded up a strop with 0.5 micron paste and gave it two dozen passes.
This knife is far sharper than it was when it arrived, and can now fall through a tomato under its own weight when held between two fingers at the end of the handle and pulled back. I don't need a kitchen knife to be any sharper than that.
Nice experiment... Each little jar of diamond compound cost $2.95 US, and should be enough to pass down to my great-grandchildren. Perhaps if I spent $29.95 for the compound it 'may' have worked better... but I doubt it. Probably the scratch pattern would 'look' better under a microscope, but I don't cut tomatoes under a microscope, so I'm satisfied. At a tenth of the price, I'm REALLY satisfied.


Stitchawl
 
Update to the update: I have a small ceramic paring knife that I had been using until it got too dull. I dug it out of the drawer and looked at it under a glass and discovered that it was covered with micro-chips, some fairly deep. I hadn't noticed them before, but trying to cut a piece of copy paper felt like I was using a saw!

So... in the name of Science, and being too lazy to try just stropping them out, I dug out a DMT aligner and diamond stones. BIM! BAM! BOOM! 30 minutes later I had a ceramic paring knife that would smoothly slice paper. (Using Fine, Ex-fine, and Ex-Ex-fine DMT stones.) Tomorrow, I'll do some stropping to it, and bring it to a nice edge. I like this experiment!


Stitchawl
 
Obsessed with Edges said:
I've noticed apples are a great test subject for evaluating cutting geometry. [snip]. Very crisp shoulders on a V-bevel can dig in and get bound up as the apple pinches the blade (I've noticed this in cutting cardboard as well). A polished & very thin convex, on the other hand, will glide right through it with ease.
Click to expand...

Amen to that. Convexed the edge on a mora knocking the shoulders off, could not believe the difference that makes cutting wedges out of an apple.
 
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