ceramic knives with the S G

[iSharpen]

This surprised me. Thoughts?

https://youtu.be/u1mMoXjHWcQ?si=gAGpWFrQJulJnGBt

Ken

Only just found this. Don't worry, it surprised me too! Here's a bit more info.

I had a long discussion with the owner of the knife before he let me try. I set the SG to to about 960 grit (the fine setting) using the 320 grit diamond plate and started VERY gently as I was aware of the chipping issue. I was very surprised when I saw that the knife seemed to be accepting the grind so I continued ever so carefully and gingerly. I was using a super soft touch, expecting the knife to explode but nope. I was able to take a fairly chipped edge and turn it into a decent edge by treating it like a normal knife.

I didn't deburr as I couldn't detect a burr and it seemed to slice paper where as before it was tearing it and was useless as a fine slicer. It wasn't razor sharp though and he was happy to take it away vastly improved. The chips (damage) weren't large but there we very visible and numerous. I wish I'd take a video before I started but I really didn't expect it to work and just started grinding it as he was there watching. It was only after I had achieved a result that I knew I had to share it on YouTube. The edge as presented resembled a misused global edge if that makes sense.

I assure you all there was no trickery and my surprise (although slightly bombastic and cringey) was genuine. I caught some flack in the comments but I can assure you it worked. My advise, start with a smooth wheel and push down only just enough to maintain contacts on the wheel but yes, the SG wheel can "sharpen" ceramic knives. I love the SG wheel.

A little info about the knife would help.

It was a Kyocera INNOVATIONblack® Knife similar to this although I don't remember a soft handle.
https://cutlery.kyocera.com/innovation-soft-grip-3-ceramic-paring-knife-black-z212-blade

[tgbto]

I sharpened the same knife this a.m. on a SB stone (edge leading)... and while I didn't spend a lot of time on it, I'm pretty sure I got a better edge... at least slicing thru some ad paper.

I don't know much about the physical properties of SG and SB. But I haven't yet had to true the SB, and in its current state I would say the surface is more even than the surface of my (several-times-trued) SG. Ie the RMS of the indentations is smaller. So you are using a harder, smoother medium than the SG, and it is logical that the blade would chip less. If you are abrading rather than microchipping on a smaller scale remains to be seen, and will depend on the relative hardness of this ceramic and silicon carbide.

[tgbto]

[Damn I messed up with the edits/post buttons]

I sharpened the same knife this a.m. on a SB stone (edge leading)... and while I didn't spend a lot of time on it, I'm pretty sure I got a better edge... at least slicing thru some ad paper.

I don't know much about the physical properties of SG and SB. But I haven't yet had to true the SB, and in its current state I would say the surface is more even than the surface of my (several-times-trued) SG. Ie the RMS height of the indentations is smaller. So you are using a harder, smoother medium than the SG, and it is logical that the blade would chip less. If you are abrading rather than microchipping on a smaller scale remains to be seen, and will depend on the relative hardness of this ceramic and silicon carbide.

[cbwx34]

The particles seem quite coarse. So it looks more like the edge is somehow getting microchipped away. It would be interesting if you could somehow get a microscope shot of the edge and the particles.

Today I dug out a 1200g CBN wheel and tried that.  Noticeable  difference in sharpness and edge smoothness, even vs. the SB wheel, and way better than the SG wheel.  And the water was cloudy with very fine particles in the bottom.  (Ignore the bigger "pieces" that's towel.)

You cannot view this attachment.

I'd say, from what you've posted, that this is actually the difference of abrading vs. microchipping the edge away?  Certainly a different result.

[3D Anvil]

Today I dug out a 1200g CBN wheel and tried that.  Noticeable  difference in sharpness and edge smoothness, even vs. the SB wheel, and way better than the SG wheel.  And the water was cloudy with very fine particles in the bottom.  (Ignore the bigger "pieces" that's towel.)

Interesting.  Did you sharpen edge leading or trailing?

[cbwx34]

Interesting.  Did you sharpen edge leading or trailing?

Edge leading.

[3D Anvil]

Do you happen to remember what your edge angle was, CB?  Outdoors55 from Youtube recently posted a video about sharpening ceramics on resin-bonded diamond stones.  He had many unsuccessful attempts using various stones, but eventually concluded that the key was to use a more obtuse edge angle. 

https://www.youtube.com/watch?v=FFEgg7OWsUk&t=508s

I found that curious, since my two Kyocera ceramic knives came with factory angles of 13 and 14 dps.  I wonder how they sharpen them at the factory....  They measured at 100 and 110 BESS, which is waaay sharper than any factory edge I've gotten on a steel knife.

[cbwx34]

Do you happen to remember what your edge angle was, CB? 
...

It was 20dps.  (I think I tried 15dps on one of them a while back and I saw a lot of chipping.)

[HaioPaio]

I believe this is an interesting read at
ScienceOfSharp.

It states that aluminum oxide abrasives are sufficient, however a much finer grit than the SG-250 is suggested.

[3D Anvil]

I believe this is an interesting read at
ScienceOfSharp.

It states that aluminum oxide abrasives are sufficient, however a much finer grit than the SG-250 is suggested.

Very interesting. It seems Kyocera has improved their sharpening process since that was posted in 2018.  My examples easily push cut paper.

[tgbto]

I believe this is an interesting read at
ScienceOfSharp.

It states that aluminum oxide abrasives are sufficient, however a much finer grit than the SG-250 is suggested.

Nice find, this site really is a trove of useful information. In a pinch, it says that you have to use reasonably hard, but very fine material so you chip on a sub-micron scale. Which requires a blade made of material that can separate on a sub micron scale. Using a glass substrate makes for a hard, smooth support that ensures that the "angle of attack" of the hard particles wrt the blade remains constant and controlled.

It also confirms that the initial "sharpening" of the blade with the sg was probably more of a roughing-up of the shoulders of the apex, resulting in two fine hacksaws.

[kwakster]

For me Paper Wheels used with diamond compounds completely solved the problem of sharpening ceramic knives to a very keen edge.
I only sharpen what i know to be good quality ceramic, and most ceramic edges i polish up to 6,0 micron diamond compound..
For an even keener edge i refine up to 1,0 micron diamond compound.

Some examples i did about 10 years ago:

https://www.youtube.com/watch?v=q4YGGHltloU

https://www.youtube.com/watch?v=dP6fNB_obN4

https://www.youtube.com/watch?v=dP6fNB_obN4

https://www.youtube.com/watch?v=hUkKfwGFogY

https://www.youtube.com/watch?v=RSkxPA9BK8E

[3D Anvil]

Nice, Kwakster!  I've never gotten along with paper wheels, personally, but your results speak for themselves.

[John_B]

For me Paper Wheels used with diamond compounds completely solved the problem of sharpening ceramic knives to a very keen edge.
I only sharpen what i know to be good quality ceramic, and most ceramic edges i polish up to 6,0 micron diamond compound..
For an even keener edge i refine up to 1,0 micron diamond compound.

Some examples i did about 10 years ago:

https://www.youtube.com/watch?v=q4YGGHltloU

https://www.youtube.com/watch?v=dP6fNB_obN4

https://www.youtube.com/watch?v=dP6fNB_obN4

https://www.youtube.com/watch?v=hUkKfwGFogY

https://www.youtube.com/watch?v=RSkxPA9BK8E

How prone to chipping are ceramic knives that are made very sharp with your method?

[kwakster]

In general ceramic knives are still more chippy when compared to steel knives, but due to the much higher polishing process i have found the resulting edges to be less chippy when compared to factory sharpened ceramic knife edges.
They are also noticeably keener.

With ceramic knives polishing the edges to certain degrees greatly improves their edge retention, and an edge polished up to 1.0 micron diamond compound lasts longer than that same knife polished only to 6.0 micron, all else being equal.

The downside is of course that i need to do 2 more polishing steps (with 3.0 micron and 1.0 micron, all on dedicated Paper Wheels)
Through testing and feedback i have found 6.0 micron to be a good compromise between edge holding and time spent polishing.