Sharpening of Ceramic Blades

L

langchop

Joined
Jun 16, 2007
Messages
301
Hi Guys,

I have always proudly worked on getting a hair popping sharp edge on my blades.

I recently bought a ceramic kitchen knife (but have no experience with ceramic knife, so technically a ceramic virgin)

Ignorantly thinking it cant be that different to steel wrt sharpening, I hauled it out of the drawer, and tried to sharpen up the edge with my, admittedly cheap, Rolson diamond sharpener. I pretty much wrecked the edge and got it sharp as broken brick! Appeared to have brittle chips along the edge.

I have since given it a bit more attention with my finer grade DMT diamond sharpener and improved it, but it is still not a keen edge and still not even at the level of sharpness as the knief was out the box.

Does anyone have experience sharpening ceramic knives and can you offer me any advise on technique etc.:D

Thanks, much appreciated.

Lang
 
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Two basic things -edge angle has to be greater than for a steel blade.
edge has to be finely polished as scratches can initiate cracks !!
 
My personal experience is that ceramic blades are never very sharp, they are kinda sharp and stay that way for a long time. I bought one a few years ago to test and see what all the mess was about and it was never hair poping sharp, but worked well and now 2-3 years later probably works as well as new. I would worry that ceramic when honed to a fine edge would just break.
 
If you're chipping the edge while sharpening, I'd try it again with lighter pressure. ...no experience with the ceramic you're using, but a lot of miles with tungsten carbide...

I wonder if you could strop it with diamond paste? The paste isn't particularly expensive.
 
Just remember the fracture toughness of ceramics is about 1/10 that of steel. This is not the impact toughness as measured by Charpy tests, but a test of a materials sensitivity to flaws, like scratches and inclusions. A rough edge on a ceramic knife will chip. A polished edge is not just a sharpening option, but the only way they will work. I'd recommend biting the bullet and sending it back to be sharpened by the manufacturer. They have the fine diamond polishing equipment to do it in a reasonable amount of time.
 
Ceramic stones should sharpen ceramic, albeit slowly. Diamond paste on a cast iron lap should work for finishing the edge.
This is all theory, BTW.
 
2 cents:
Get the fine diamond lapidary lap. Something about 1500-3000 grit. Light pressure, water and some patience will do the trick. The finer grit the better edge, but slower the process. You choose.
 
Thanks for the feedback guys.
The original angle looked somewhere between 20 & 25 degrees. The edge I have put on now is 25 degrees (by holding my diamond 'stone' against the stone of my lansky system to keep the angle.)
It was quite a cheap knife (just want to get to know the characteristics of ceramic) so in this case I dont reckon its worth sending it in for sharpening.
From your advices I think I will try increasing the angle to 30 with my diamond stone then patiently polish it up with fine SiC paper (using the Lansky to keep the angle throughout)
Will report back on how that turns out!
 
My Bicker cam hair popping sharp, but once dull, I just had to try to do it myself. Very fine diamond hones= jagged edge. It's gonna take lapidary equipment!

Mike
Maker
The Loveless Connection Knives
 
Report Back...
I am actually very impressed with these two cheapskate knives I got. I learnt that the black blades are tempered for better toughness, and the knife that I didnt wreck the edge on is actually as sharp as any steel hair popping edge I have ever felt.

I exercised some patience and gently honed down the surface with diamond then progressing to 1200 grit SiC paper. Stuck with the 25 deg angle that I accurately measured on the other knife. Got sharpish, but still nowhere near the uncorrupted knifes edge.

So now it is officially the kitchen chopper. Will use this knife to get a feel for how much abuse a ceramic knife can handle!:D
 
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