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 Post subject: Re: Sharpening a black ceramic kitchen knife
PostPosted: Wed Aug 14, 2013 8:26 pm 

Joined: Thu Aug 01, 2013 4:02 pm
Posts: 9
Basically i start out with a new uncoated & unslotted Paper Wheel and coat the surface with a layer of light oil with tackifier in it, then let dry for at least 12 hours or until the surface looks dry.
Then i coat the surface with a thin layer of 3M diamond paste and immediately after with another layer of oil, rub it in & mix with a clean finger, then again let dry for at least 12 hours or until the surface looks dry.
I repeat the process regularly after several knives, as not all of this mixture stays on the wheel indefinitely.
After several layers of oil & diamond paste as well as sharpening with it the surface of the wheel develops a tacky dark grey layer which will hold the diamond particles noticeably better than in the beginning.

The diamond paste i use is made by 3M for the electronics industry (chip production) and consists of a light grey colored oily clay base mixed with diamond particles.
The mixing oil i currently use is a specialty grade used in the audio industry for turntables (certain types of thin chainsaw oil work as well), but it seems you can also buy tackifier separately and add it to your choice of light machine oil.
I haven't done this yet but plan to.
Both the tackifier and the drying of the oil help to keep it on the wheel, while the oil itself holds the diamond particles.

A Wheel with 15 micron diamond compound lets you sharpen ceramic knives that are just plain blunt or have only minor chipping.
I use this wheel also as a finisher on folders and smaller fixed blades with various wear-resistant steels like S30V, S90V, ZDP-189, CPM-M4 and M390, and it produces only a very tiny burr which is easily stropped off (i use the Tormek leather wheel)
For the removal of larger chips and the setting of completely new bevels on ceramic knives however you will need heavy machinery like for instance a Tormek T7 fitted with a SB-250 Black Silicon stone like i do.

A Wheel with 6 micron diamond compound lets you refine the edge on ceramic knives and gives you a very good sharpness, edge quality as well as bite.
I also use this wheel to finish certain larger bladed steel knives like for instance kitchen knives made from wear-resistant steels.
For what it's worth i never had a better edge on my early '60's Gerber kitchen knives which use hard chromed M2 high speed steel, and which can be notoriously difficult to sharpen by other means.

BTW: the best quality ceramic knives i have found to date are the black ones made by Kyocera: the Revolution series if you're on a budget, and the Kyotop series if you want to spend more.
As the black knives are also tougher than the white ones they can be made with thinner edges, which not only cut noticeably better but are also more easy to resharpen since you have less material to remove.
Reprofiling a rather thick white ceramic knife can take up to several hours, while a black knife reprofiles in about 30 to 45 minutes, both done with the Tormek T7 fitted with an SB-250 Black Silicon stone.


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