I'm considering getting a medium grit natural stone. The ones I might be interested in are tajima and atago, but I haven't found much information about the atago and I don't know if it's worth (besides size difference). What are the differences between them, and would there be better options? I'm new to naturals.
I haven't used an Atagoyama, however (and I can confirm this if you wish) I suspect it is not a very precise classification of a stone since Mount Atago is the mountain that many mines are located on, so it may simply mean an unspecified mine. I may be wrong on this point, but it's my suspicion. This is similar to calling a stone a Honyama or even shouhonyama, which is leaving the mine unspecified, so you will expect a great deal of variability between stones. Where there is the use of the term Atagoyama (yama is simply a suffix meaning 'mountain') it is referring to a polishing stone (awasedo) rather than a mid grit stone like the Tajima.
Among the medium grit or nakado stones, the Tajima is one of my favorites. I am expecting some in very shortly - next couple of days. My supply was sold out shortly after doing this video. Send me a PM or better yet email me at firstname.lastname@example.org , since my PM box overflows regularly. They are brick sized stones and work quite nicely. Among the other nakado are the Igarashi, Binsui, and several other rarer stones , eg ebisu. Although the Aoto are often of a similar grit range, strictly speaking they are not considered nakado, but more of a parallel grouping.
While I'm not sure exactly what your specific application is or your other stones, here is a Tajima video demonstrating how it works on an Aogami super carbon steel.
Note that the specific stone in the video is one damaged in shipment to me that I repaired so the ones I get won't have the burgundy or red around the sides of the stone.
I have no experience with the Tajima, but I recently got the Atagoyama mid-grit stone from Mark and I can write a little bit about it. It's a big and heavy stone. It's also very smooth and is quite hard - it wont generate very much slurry on its own. Once you get some slurry going (via some nagura or diamond plate) it cuts moderately fast, and leaves a pretty nice even polish as long as I apply very light pressure. On my stone, I found the grit to be much finer than the 1000-2000 as described. I found it to be AT LEAST 2000 (compared to my naniwa green brick), but probably more likely in the 4000-5000 range.
About the mines, I'm pretty sure there was a specific mine named Atago. I've seen some really nice stones from that mine from other vendors including coarse akapin stones all the way up onto very large and attractive final polishers.
Also - one more thing that I'm learning. If you are just sharpening the edge of a double-bevel blade, just about any stone will remove metal and refine your edge, and a natural will by nature leave somewhat of a toothy finish compared to a synthetic. They'll vary on feel/softness, and cutting speed, but you'll get your edge refined. If you're talking about polishing a single bevel or the wide bevels of a double bevel knife, then you'll have to more carefully select your stones so you end up getting a nice even polish on the blade road or wide bevel.
Still trying to get a definitive answer on this. Mount Atago has a number of mines on it, as well as a temple near it's top, so I'm not clear about if it truly is a single mine or a more generic term. This is not without precedent as you will often see 'Narutaki' stones. Here it refers to a district or region and within that area are a couple of mines. Indeed in the past the term Narutaki was even more broadly used (erroneously) to include a variety of mines, sometimes even outside the Narutaki region. Usually the Akapin layers are the more superficial layers, and therefore are softer stones than the deeper layers that have been compressed more.
To squeeze a bit more performance out of a stone (finer slurry) rather than using a diamond plate - even a 1200, use a tomonagura. The diamond carves chunks of the stone out leaving larger particles in the slurry that need to break down further to achieve the level of fineness that a tomonagura achieves directly.
I cant comment on the stones you listed, but you mentioned other choices so......
I got this to try in the progression slot of a Bestor 1.2K and so far its been great. I really haven't used the Bestor much at all since getting the Aoto.
Relative to the Bestor, the Aono Aoto is softer and muddier. In use it feels smoother and depending on how much pressure you use and how refined you run the mud, its feels to have more range as far as the type of edge you end up with.
Speed wise, it is a little slower on the AS steel I have by maybe 10%, but given that I'm not looking for my mid grits to be bevel setters, and given how much I enjoy using it, thats a plus for me
Overall I like naturals for the smell, the ancient feel of them, and the range of edge options you can get from each stone.
Thank you all for your repplies; Branwell, I agree with you and many others, to me sharpening with natural stones is like going back to the human origins. If you are efficient with them, I don't think there are more steps to follow in the sharpening process (but that's just my opinion, at least now; maybe in the future it changes). Ken, thank you very much for your clarifying answers here and to other threads. Maybe I'll contact you during this week. I've read you say Aotos are a category on their own, can you explain it?.