Sharpening a Ceramic Knife

[RickKrung]

There is not much info on our forum about whether to or how to sharpen a ceramic knife.  I did a search and didn't find much.  I have the full complement of grinding wheels, SG, SB, SJ, and all three diamond wheels.  I assume it would be best to use the diamonds, but has anyone actually done this and if so, how did it go? 

I'm back at a farmers market today and last week one customer said they would be bringing in two ceramic knives for me to sharpen.  I realize it is last minute and I have not do my homework, but if anyone has any suggestions (other than telling him to come back when I know more, which I am likely to do at this point), I would greatly appreciate it. 

Thanks,

Rick

[cbwx34]

There is not much info on our forum about whether to or how to sharpen a ceramic knife.  I did a search and didn't find much.  I have the full complement of grinding wheels, SG, SB, SJ, and all three diamond wheels.  I assume it would be best to use the diamonds, but has anyone actually done this and if so, how did it go? 

I'm back at a farmers market today and last week one customer said they would be bringing in two ceramic knives for me to sharpen.  I realize it is last minute and I have not do my homework, but if anyone has any suggestions (other than telling him to come back when I know more, which I am likely to do at this point), I would greatly appreciate it. 

Thanks,

Rick

My .02.... use only the finest diamond wheel, match the edge already on there, and make alternating passes until it's sharp (or at least sharper).  Supposedly the SB stone graded fine will also work, but haven't tried it.

Ceramic knives can be very prone to chipping... which is why I suggest only the finest wheel.  Coarser wheels can chip it, and it's hard to fix.  And you probably know that no burr is created, so no need to "debur".  Wouldn't bother with SJ or SG stone.  If you have any type of fine diamond compound you could hone with that, but not necessary.

I also know that there's different grades/level/quality of ceramic... the cheaper ones don't seem to get particularly sharp... but can take a decent slicing edge.

All i got, at the moment anyway... 

[Fernando]

There is not much info on our forum about whether to or how to sharpen a ceramic knife.  I did a search and didn't find much.  I have the full complement of grinding wheels, SG, SB, SJ, and all three diamond wheels.  I assume it would be best to use the diamonds, but has anyone actually done this and if so, how did it go? 

I'm back at a farmers market today and last week one customer said they would be bringing in two ceramic knives for me to sharpen.  I realize it is last minute and I have not do my homework, but if anyone has any suggestions (other than telling him to come back when I know more, which I am likely to do at this point), I would greatly appreciate it. 

Thanks,

Rick

Some time ago someone talked about the diamond wheels in ceramics knives in another thread.
I also did my own tests on the SG-250 wheel

https://forum.tormek.com/index.php?topic=3686.0

[RickKrung]

Yes, I saw that thread.  Cyrano talked about three slow, light pressure passes on the DE diamond wheel producing a nice looking edge, but one that was not very sharp (600 BESS) that cut copy paper with difficulty.  He had some extremely good photos to show why also. 

Following that info and CB's, I "intended" to do similarly.  By mistake, I put on the DF wheel and proceeded as above.  I wondered why it was "ticking" on each revolution of the wheel (mentioned in my post about a chip on the edge of the DF wheel making noise).  Once I realized I had the DF on instead of the DE, I quickly changed it and carried on with it.  It did produce a nice looking edge to the eye, but when I examined the edge at 60x hand scope, I saw some very fine micro-chipping.  When I had examined the knife before doing anything, it had multiple chips of varying sizes, but I did not notice (as I was looking the large ones) any micro-chipping.  I had at least gotten rid of the larger chips    BESS score averaged 410 and the knife cleanly push cut phone book paper at the tip, less cleanly in the middle but did so roughly near the handle, which was in line with the three individual scores, 320, 405 and 504.  Still, it was not a satisfying sharpening. 

In talking with the customer before I started, he asked me to sharpen one of the two ceramic knives that he brought in.  Afterward, he said he would take the one home and see how he liked it and if he did, he would bring the other one back next week.  We'll see.  To be sure, I'll take more care if there is a next time and take better notes. 

Rick

[wootz]

Hi Rick,

I've detailed our sharpening of ceramic knives on our website http://knifegrinders.com.au/06Procedures_ceramic.htm

Can only add that in the Kyocera video we see them finishing ceramic knives on a felt buffer with what looks like a Green Rouge compound. Technically, chromium and aluminium oxide cannot grind ceramic, but obviously they know what they do at Kyocera.
https://www.youtube.com/watch?v=Oqn7vcByIgo

[kwakster]

This is how i do it:

https://www.bladeforums.com/threads/forever-sc-16wb-ceramic-knife.1206014/

https://www.bladeforums.com/threads/sharpening-a-black-ceramic-kitchen-knife.1088417/#post-12446725

[cbwx34]

I ran across this interesting... How Ceramic Knives are Made... video... doesn't really give any info on how they're sharpened (more of a TV documentary type show)... but thought it was a bit interesting...

https://youtu.be/JFnT5INymiY

BTW... didn't mention it before, (cause I knew it wouldn't help at the Farmer's Market)... but the best edge I've been able to get on a ceramic knife is with WorkSharp's setup for their belt sharpener.  (Still not an edge I would brag about... but does get it to cut decently).

[Fernando]

Hi Rick,

I've detailed our sharpening of ceramic knives on our website http://knifegrinders.com.au/06Procedures_ceramic.htm

Can only add that in the Kyocera video we see them finishing ceramic knives on a felt buffer with what looks like a Green Rouge compound. Technically, chromium and aluminium oxide cannot grind ceramic, but obviously they know what they do at Kyocera.
https://www.youtube.com/watch?v=Oqn7vcByIgo

Very good information

Although I must admit that later I went to see the good results of the repairs of the knives. 

http://knifegrinders.com.au/03Repairs.htm

[Plekter]

if anyone has any suggestions (other than telling him to come back when I know more, which I am likely to do at this point), I would greatly appreciate it. 

Thanks,

Rick

Hi Rick

Without owning any of the diamond-stones - I have this method.

And remember  - if you are too violent on the edge of a ceramic knive, then the small crystals it is built up by, will jump off from the edge instead of being sharpened - and then expose a new crystal with some sharp corners.

It is also the reason a ceramic knife stays sharp longer than metalknives...actually the edge just breaks off and expose some new crystals in a not very beautiful edge.

And it is also hard to cut with a ceramic by just pushing down. It has to be sawing forward/backward to cut good because of that way it performs.

So back to my method:
First use the SB-stone - made as slick as possible - and with low pressure on the stone -  to make an acceptable edge - removing visible dents etcetera, and try to follow the same angle as it had before. When it is as good as it can be - then go to a fine wet whetstone - I use a pretty hard 16000 grit shapton glass-stone. It is so fine that it can actually grind the side of the crystals on the edge, instead of just making the crystals bounce away as they would do with a grittier stone.

The result will be worth to brag about - but will take a little extra time.

And never try to use a sharpening rod/ceramic rod to maintain the edge on a ceramic - it will just make a lot of the crystals disappear.

Joergen

[RickKrung]

...snip...
So back to my method:
First use the SB-stone - made as slick as possible -
...snip...

Oh, great.  I just trued my SB stone   It had gotten quite glazed.  Guess I'll have to wait a bit. 

And I just bought a couple of cheap ceramic knives at BiMart to use for practice. 

But, I really appreciate the information and method.

Rick

[Plekter]

@Rick
Looking forward to hear how it will work for you :-)

[RickKrung]

@Rick
Looking forward to hear how it will work for you :-)

I am looking forward to exploring the world of sharpening ceramic knives.  I've put together a small spreadsheet with all the steps mentioned/used by others so that I can compare and hopefully decide on a process.  So far the most consistent element is the use of the SB stone for establishing and/or finishing the grinding process.  Wootz is the only one I've found who uses a progression of finer grinding (CBN or diamonds) after the coarsest (which includes the the SB).  He and Kwakster then use a progression of finer diamonds on paper wheels and you used a 16K grit glass stone for honing/polishing. 

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

[cbwx34]

Keep in mind that some ceramic knife makers will resharpen for free.

[RickKrung]

Keep in mind that some ceramic knife makers will resharpen for free.

Yes, Shun being one.  I'm not concerned about that.  Anyone with a knife from a maker that sharpens for free should do that.  I am thinking more about those that don't have that option, but also, just for my own edification.  I bought a couple cheapies for practice and the fellow who brought the two to my booth could not send them anywhere, let alone for free. 

I hope NOT to be doing any farmers markets after this season ends (after two more Weds.).  I started doing it to help my daughter's market.  Doing the markets is okay when there, but I do not enjoy bringing things home to sharpen and apparently I'm not fast enough to do it all while at the markets.  Also, even if I was faster, there just isn't enough money in it at $5/blade to make it attractive enough for me to continue. 

Rick

Edit to add:  I don't know that Shun does ceramic, just that they sharpen their knives for free IF they don't have damage such as chips along the bevel and broken tips, something some of their knives are vary prone to do if their use protocols are not strictly followed.  If that is the case for ceramic knife makers, which I wouldn't be surprised as ceramic is prone to chipping also, then the free sharpening may not be as available as it might seem. 

[kwakster]

Also keep in mind that there are many different qualities of ceramic knives, just as there are with steel knives.
Cheapies in general aren't worth it to resharpen them, best to tell the owner to simply buy a new one.
I've stopped sharpening these category completely.

Even the two best edge takers & holders among ceramic knives i've encountered thus far (Forever and Kyocera) differ quite a bit.
With an SB stone you can easily grind Forever ceramic knives to repair & set completely new edge bevels, while the same stone takes a lot more time on Kyocera knives.
For those i'm sure a CBN or diamond wheel would work faster and probably better, but currently i don own one.
After grinding you have to polish the bevels, both to get the sharpest apex as well as the best edge holding.
Toothy edges are a no-no on ceramic knives.
Imo the Forever knives do a bit better in the edge holding department than Kyocera knives as the material seems more resilient/tougher, it chips less in use, and when it does chip those chips are noticeably smaller.