Ok, yet another Japanese natural review, with an Atoma diamond plate review tacked on the end.
First, the Asagi.
It was bought from So at japan-tool.com. I feel lucky to get hold of this stone. So asks a lot of questions to try to match stone to user and uses. Being in Australia, I saved a bit on shipping and exchange rate fees too. This stone cost 60 JPY per gram. So showed me several Asagi that he had, and recommended this one as being, quality-wise, second only to his "miracle stone".
The stone is a fairly uniform blue colour with very little skin, and came unmarked (no visible stamps). So tells me Asagi can be scratchy, but this one is as smooth as silk. It is also extremely hard, so much so that I purchased the Atoma 1200 grit diamond lapping plate in order to generate slurry. It is also, as I found out (and So warned me about), a very fast and strong cutter.
First use of this stone was on a couple of NOS full hollow Dorkos for a fellow member. I did perhaps 20 laps on each after getting an edge off the Shapton 16K. Overhoned. Well, there's a theory going around that it wasn't technically overhoned as in a wire edge, but rather the edge produced was too fine for the steel and so died halfway through the shave. Whatever, the end result was the same. Valuable lesson learned.
Next, I tried it on an old Boker King Cutter. Very carefully this time, 5 laps at a time between testing. The edge produced was very, very nice after two sets of 5 laps. Wonderfully smooth shave, and the edge held up.
I've since used it on two JR wedges, and an A. Leon Wedge. Good Lord! This thing loves the wedges, or the wedges love it, I can't tell. Superb shaves.
As to it's grit - finer than a 16K is all I can say with certainty. So hinted that it would give finer edges than a 30K Shapton, but I've never shaved off a 30K Shapton, so I don't know for sure. I also have never used Chrome Oxide or diamond pastes, so again I have nothing to compare to there.
Because of its speed, I've been using it straight off the 6K Narutaki I have, and once straight from the 4K Norton.
So, to summarize. Very hard, very smooth, very fine, very fast and, in my opinion, very beautiful stone. Three thumbs up. Highly recommended. Perfect. 10+.
On to the Atoma. I bought this on So's recommendation, although to be fair he did say that a Nagura would do as well, and was a cheaper option. However, I decided that a 1200 grit diamond plate would come in handy for other things too, moreso than a Nagura, so I got it instead.
It cost 110AUD and was shipped from Japan.
It is a diamond plate mounted on a hollow metal base. I haven't measured it, but it's about 1/2 inch longer and exactly the same width as my Norton 4/8K. It needed to be sealed around the seam where the diamond plate sits on the metal base - I used epoxy glue - to stop water getting inside the base and rusting from the inside out.
So far I have only used it to generate a slurry on the Asagi. Works well for that purpose. Seems a well made, solid piece of kit, and as long as you are aware of the rusting issue and seal it, pretty trouble-free. Time will tell on the diamond plate itself, I guess, although So assures me it is good quality for the price.
I'm very happy with it. But again, I have nothing to compare it to (specifically, the DMT range).
James.