Sharpening a Ceramic Knife

[Plekter]

Just for fun...I tried another method today with a Kyocera knife.

First the SB-stone (it can be hard not to get marks on the edge - if the knife tilts occasionally so it grinds on the corner of the stone- then marks appear almost instantly - so be careful).

After that I went to the 4000 grit SJ-stone. And it actually went quite good also - and faster than a handworked weatstone.

I could at least cut paper with it afterwards - not the absolut smoothest feeling, but quite okay.

Joergen

[RickKrung]

...snip...
It hasn't come up here, but elsewhere I have been very frustrated by my inability to take good photos of knife bevels and other sharpened edges (and the diamond wheel defect), using cameras and a dissecting microscope.  I have just ordered a Dino-Lite USB microscope that does focus stacking, among other things.  I hope and expect that will greatly improve the photos I'm able to produce.  I'm holding off on attacking the two cheap Farberware ceramic knives I bought at BiMart until I can document their initial bevel condition so I can compare what happens with sharpening. 

Rick

The camera has arrived.  I initially ordered and received a model that had a longer working distance and max. magnification of 145X.  I didn't care for it and returned it for the closer range model with a max. mag. of 220X.  I am much happier.  Both are USB with focus stacking and other features.  I am waiting on some paper wheels to use with the diamond pastes that arrived, but I can begin with the grinding. 

Here I am simply going to document the starting point. 

Very cheap Farberware ceramic knife purchased from BiMart. 5" blade.


As measured by BESS scores, it isn't all that sharp, average of 388 (314, 421, 429).  It doesn't push cut copy paper very well, but does push cut phone book paper relatively easy, which causes me some doubt about using it to demonstrate my sharpened blades. 

Using the new microscope, I took a photo of the bevel, showing the grind pattern and the edge condition. 


Measurements indicate the bevel is 0.45mm wide.  Grind pattern is diagonal with grind density of about 0.01mm.  The apex appears to consist of connected microchips of about <0.01-0.02mm, similar to the grind pattern density.

I hope to be able to compare these as I work through the grinding process on the Tormek and honing.  Following what others generally are using, I plan on using the SB stone to start with, followed by the DF and DE diamond wheels and then probably the diamond paste steps that Wootz uses, of 5 micron and a mixture of 0.25/0.05 micron as it requires just two paper wheels.  I have a second Farberware ceramic knife and am thinking of using the SJ wheel between the DE and diamond pastes.

Rick

[cbwx34]

...
As measured by BESS scores, it isn't all that sharp, average of 388 (314, 421, 429).  It doesn't push cut copy paper very well, but does push cut phone book paper relatively easy, which causes me some doubt about using it to demonstrate my sharpened blades. 
...

Bit of a sidebar about phone book paper... most have a well defined "grain" making them fairly easy to cut in one direction, but rotate it 90° and it is much more difficult.  (So one way will impress, the other way tells you if it really is sharp).

[RickKrung]

...
As measured by BESS scores, it isn't all that sharp, average of 388 (314, 421, 429).  It doesn't push cut copy paper very well, but does push cut phone book paper relatively easy, which causes me some doubt about using it to demonstrate my sharpened blades. 
...

Bit of a sidebar about phone book paper... most have a well defined "grain" making them fairly easy to cut in one direction, but rotate it 90° and it is much more difficult.  (So one way will impress, the other way tells you if it really is sharp).

Yes, I have noticed that, but have not dealt with it yet.  I was using it because I thought it a better gage than copy paper, but that seems to be not so true.  I was using the phone book paper as it seemed to correlate with the BESS scores and was cheaper and more redily available than copy paper.  I'll have to reevaluate. 

Rick

[Serhij]

The problem with sharpening ceramic knives is that ceramic blades are very brittle. Ceramic has a hardness of 9.5 (as opposed to steel with a hardness of 6.5). If you apply too much pressure to the side of the blade, it could easily snap. Also, the only material hard enough to sharpen ceramic is diamond, with a hardness of 10.
What about just buying a new knife, jeez... they are inexpensive compared to "real" knives, e.g. Henckles..I know we live in a "throw-a-way" world, but the sharpness level on my ceramics is insurmountable compared to everything