Tomo Nagura 101

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Some thoughts on Tomo Nagura


Tomo Nagura are rubbing/slurry stones; smaller pieces of finishing-quality stone that are used to raise abrasive slurry on the Honzan. The general idea is this; the Tomo generates very fine slurry that breaks down even finer when worked. The resulting edge would then be finished, or possibly enhanced further by a session of water-only laps on the Awasedo. The word ‘Nagura’ translates to ‘correcting stone’; another purpose of the Tomo is to help keep the surface of the Awase flat and prepared for use. 

On occasion, someone will cut a Tomo from their Awase in an attempt to create the ‘perfect’ Tomo/Awase combination. This concept assumes that the host stone’s own slurry will produce the finest result possible. While this reads well ‘on paper’, in actual use it seems to fall short. While the exclusive use of the base-stone’s slurry ‘may’ allow a glimpse of an overall understanding of the stone, I’ve found that it’s maximum potential will remain hidden until a well-matched Tomo Nagura is employed. There are no rules though, whatever works is what works. 

While the Honzan’s slurry may yield a finer result than one particular Tomo, employing a totally different Tomo can yield even greater refinement.  How two different abrasive particles can work together to produce a finer result than either can on their own is a concept that is challenging to understand, but one that has proven itself repeatedly and consistently. Experimenting with different Tomos is a huge part of owning and using Japanese natural whetstones. 

 A Diamond Nagura can substitute for a ‘real’ Tomo, in a pinch, but care must be taken when doing so. They can shed diamond bits that will destroy and edge. Having ruined 3-hr of hard work on a teensy weensy diamond-dust pebble that was hiding in the slurry – I can tell you that it’s not a fun time. 

Another DN distraction is that when used on the hardest Tennen Toishi, the metallic substrate can be stripped off into the slurry. This also seems to interfere with edge-refinement and I believe it weakens the backing, which allows for the diamonds to shed. After ruining several edges as well as a few small diamond plates, I’ve decided that using a traditional Tomo Nagura is a better path most of the time. 


Some say the Tomo must be harder than the Awase, others say softer. To me this is a ‘whatever works best, is what works best’ thing. Harder or softer – the end results are what matter. A very hard Tomo may scratch, or it may not. A very soft Tomo may provide slurry that is perfect, or slurry that doesn’t refine well.  

I’ve read that the Tomo should be from the same layer as the Awase. This is not important. What matters is if the Tomo works. Mixing and matching strata are fine. I’ve employed Aisa Tomos on Tomae stones and they work as well as or better than some Tomae Tomos. If getting a Tomae stone is important, then I think a good one can be found. I just don’t think it’s a rule to live by. 

Size and Shape

Mostly, I find concerns about size and shape to be a purely superficial concern. Tactically – a larger more rectangular Tomo can be used for flattening the Awase more easily than one shaped like a ball – but past that, I’m not convinced that any one particular shape or size matters. 


I do seal Tomo Nagura – not all of them though. Eventually I may seal every one but at present I only seal those that have irregular sides or problem areas that might dissolve from getting wet. I use nail polish most of the time but any good enamel or lacquer will work. Traditionally – Cashew lacquer was used but it’s very hard to get and extremely difficult to work with. There is a synthetic Cashew lacquer that is reported to be a good substitute but I’ve not had the opportunity to use it. 

Cutting grooves in the Tomo 

It’s my opinion that cutting grooves in the slurrying-surface is a short cut that can, and probably will, cause issues. When I first started using Jnats, I had a very hard Kiita with a matching Tomo that kept sticking to the stone. I cut two grooves in it, and that allowed me to make slurry without having the Tomo stick to the top of the stone. After a few weeks, I found a small chip in the slurry when I has finishing a razor. A 4x loupe revealed that the corner of the groove was flaking; no doubt this was caused by repeated wet/dry cycles during use. I took a small file and rounded the corners off, and in a few weeks I found another stone bit in my finishing slurry. What I think is this – cutting those grooves can cause stresses that result in small fissures in the stone.  

After discussing this with a few long-term Jnat users, the general consensus seems to be that the working surface of the Tomo should be rounded and not scored. Since then, I’ve been lapping a slight curve into the top or sides of my Tomo Nagura; this stops the stone from sticking, and I don’t have to be concerned with small bits of stone flaking off into my slurry.


The Kawa, or skin, on Jnats will scratch an edge badly. If it gets into the slurry it can ruin a lot of hard work. My normal treatment is to lap off all of the skin. I’ve even cut complete edges off of skin-laden Tomo Nagura to reveal clear stone. Sealing with lacquer can stabilize the Kawa but I find it best to just get rid of it.  


© Keith V Johnson 2014 - 2018