A few days ago Chef Patrick brought me the two knives, and this morning he came by to collect his own knife again.
These first two pics show Patrick's own Sakai Takayuki santoku in cladded VG10 steel together with the reground diamond titanium santoku.
Patricks knife has already been resharpened again in the pics since he needed it back asap, as it is his main workhorse (bought new over 5 years ago)
I've sharpened this knife many times already and find the VG10 very well heat treated, imo comparable to Tojiro's.
All pics show the Diamond Titanium knife just as i received it from Patrick, only cleaned with a soft toothbrush and some mild detergent, but not resharpened yet.
The Diamond Titanium knife does indeed still cut better than Patrick's Sakai Takayuki, but that is mostly because of the thinner blade coupled with the thinner edge angle (20 degrees inclusive versus 25 degrees inclusive)
Where the used edge on the Sakai Takayuki was nearly worn smooth, the used edge on the diamond titanium blade has become coarser and it's apex has widened.
The remaining sharpness is such that with a little effort it will still slice a piece of copy paper, but it snags a bit here and there on a few microchips (these are visible in the pics).
Patrick's santoku could not slice the same copy paper, no matter how i tried.
When seen through my Victorinox loupe using daylight the entire apex of the diamond titanium knife looks a bit rough, and this has the effect of micro or even nano serrations.
Thickness behind the current edge (measured about a millimeter behind the actual apex) hovers between 0.25 and 0.3 mm.
Tomorrow i hope to test the knife myself on a few tomato's, just to see if the edge will still cut these or not.
For Patrick anyway the current sharpness is no longer sufficient for his kitchen use.
What surprised both myself as well as Patrick the most is that the knife held up so well with it's reground blade and it's low edge angle of just 20 degrees inclusive, the very apex of which had been sharpened on a DMT Red (about 750 grit) with a bit of WD40 as a lubricant.
Patrick said that he estimated the amount of food that he had cut with the knife during those two months would be comparable to what a standard family could eat in more than a year (easily).
He also told me that he didn't use the knife on hard pumpkins because he was afraid that he might damage the thin blade, but for the rest used it on everything, just like his own knife.
During the time that Patrick had the knife i found that the manufacturer recommended diamond sharpening device has a grit rating of 1200, so in the mean time i've bough 3 cheap Chinese diamond plates on E-Bay in grits 1200, 2000, and 3000, and on the second (also reground) Diamond Titanium santoku that i use in our home kitchen the apex is only sharpened with the 3000 grit diamond plate.
To be continued.