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
Quote from: RickKrung on October 10, 2018, 07:01:40 PM
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... ::)
Quote from: RickKrung on October 10, 2018, 07:01:40 PM
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 (https://forum.tormek.com/index.php?topic=3686.0)
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 (https://forum.tormek.com/index.php?topic=3768.msg25000#msg25000) 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 :o 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
Hi Rick,
I've detailed our sharpening of ceramic knives on our website http://knifegrinders.com.au/06Procedures_ceramic.htm (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 (https://www.youtube.com/watch?v=Oqn7vcByIgo)
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
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 (https://www.worksharptools.com/ceramic-knife-sharpening-and-repair-kit-x-12.html) for their belt sharpener. (Still not an edge I would brag about... but does get it to cut decently).
Quote from: wootz on October 11, 2018, 08:19:04 AM
Hi Rick,
I've detailed our sharpening of ceramic knives on our website http://knifegrinders.com.au/06Procedures_ceramic.htm (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 (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. :o ;D
http://knifegrinders.com.au/03Repairs.htm (http://knifegrinders.com.au/03Repairs.htm)
Quote from: RickKrung on October 10, 2018, 07:01:40 PM
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
Quote from: Plekter on October 13, 2018, 09:53:56 PM
...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 :o 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
@Rick
Looking forward to hear how it will work for you :-)
Quote from: Plekter on October 15, 2018, 04:59:08 PM
@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
Keep in mind that some ceramic knife makers will resharpen for free. ;)
Quote from: cbwx34 on October 15, 2018, 05:59:58 PM
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.
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.
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
Quote from: RickKrung link=topic=3769.msg25071#msg25071
...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.
(https://forum.tormek.com/index.php?action=dlattach;topic=3769.0;attach=2807)
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.
(https://forum.tormek.com/index.php?action=dlattach;topic=3769.0;attach=2809)
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
Quote from: RickKrung on October 24, 2018, 01:09:24 AM
...
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). ;)
Quote from: cbwx34 on October 24, 2018, 01:35:47 PM
Quote from: RickKrung on October 24, 2018, 01:09:24 AM
...
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
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