I first saw ZDP at the Blade Show in Atlanta in 2000. Two guys from Japan had a small table and had a few high end folders in the $450+ range with -3" blades. I can't remember, who these guys were, but they just stood there and cut cardboard over and over again and passed out the blades to let people try the knives. I never saw these blades even stropped and I was so jazzed by ZDP that when Spyderco came out with the Endura, I snagged one immediately. The chemistry of this steel content has Carbon = 3% and Chromium = 20%, this steel can be hardened up to the 67 Rc range. Not sure what the Spyderco Rc is.
I was very dissappointed by the OTB sharpness. This steel just laughed at anything, but diamond stones. I found the edge geometry to be way to thick behind the edge. I have several 8x3" diamond stones. I started with a
140 grit to try to thin out the area behind the edge for an area of about 1/8" approximately. This took a lot longer than I thought it would. I progressed up through 300, 600 and 1000 grits. I even took it up to a Chosera 2000 grit waterstone and a 4000 grit on a Shapton Japanese Waterstone and finishing on .5 micron Green chromium oxide leather strop. I found the steel to have a very brittle texture and the burr was bitch to get rid of, but I finally got the blade where I wanted it.
The way I test a knife's sharpness is not to shave arm hair or slice through paper, but rather do what I call a, 'push cut". My push cut consists of laying the knife edge on a piece of paper, i.e.: copy paper, and using no sawing motion and not changing the part of the knife on the paper at any time, I just push the edge area that I've chosen to test straight down. The knife starts out in direct contact on the paper, no starting 1/4" above. Just lay the edge on the paper and push. If you really want to test you knife's edge, try this with a piece of receipt paper. This test, I think separates sharpness from what can be a sharp burr that will shave arm hair and cut paper.
Anyway, the ZDP-189 was able to pass the test with flying colors. However, after a fairly short period of time and not doing anything crazy or out of the ordinary the edge started getting microchips and the edge began to flunk the push test. I'm not sure what the problem is with this steel. I freehand sharpen some pretty high tech steels, like the Hitachi White #2 and the Aogami Blue #2 and Aogami Super. Aogami Super can be hardened up to 65 Rc in my opinion ZDP can't compare to these other Hitachi, (as I'm sure everyone knows Hitachi makes ZDP-189). The only thing I can think of is that Spyderco blew the heat treatment or the one I got slipped through, but then the edge geometry was not right as well. I know Spyderco makes great knives and has good quality control, so I just don't think this is one of Hitachi's better steels. I'm willing to take the extra care a carbon steel knife requires, just like I am willing to wipe down a good rifle, as needed. I still really like W2, 1095, 52100 and the Hitachi White and their Blue Aogami series. These last Hitachi steels are usually found on high quality Japanese kitchen knives, but you can find them in San Mai configurations on higher end Japanese hunting knives, also. In fact, my next hunting knife will be Japanese Blue Steel fixed blade knife.
