Found: the Ultimate Waterstone

by Mathieu

It was a bit cruel to end the previous post without revealing the actual stone. Without further ado, here it is.

Suzuki-ya original #4000 waterstone

Tadaaaa.. It is the Suzuki-ya original #4000 water stone. In case you are wondering why it doesn’t look all shiny & brand new, that’s because I have been using it almost daily for the last six months. He has been jaded and enslaved, put to hard work in a high stress environment. I can say he has held up very well, Mr.4000 has removed a lot of steel, he has also shrunk by 8mm in thickness and sharpened not only my own but many tools of fellow daiku.

Lets take a look at the different criteria which I think are important when we judge the performance of a stone.



I make a living as a carpenter and I am not willing to spend a lot of time sharpening during my work and I am even less willing to compromise in edge quality or sharpness. It is bad practice and simply unprofessional, I was always taught that our clients do not pay us to play with our tools. In my free time I often end up sharpening for hours but that is irrelevant and is more a way of relaxation more than anything else. High speed is what I expect from a stone.


This is related to the previous point in regard that I dislike wasting time on flattening my stones constantly. More importantly, I like stones that remain flat since the stones flatness is your reference and during the sharpening process your are actually transferring the shape of your stone to your blade. A stone which remains flat longer will thus give you a better reference. For an ultimately sharp edge a flat bevel is helpful and therefore requires a flat stone.


The hardness or wear resistance will determine how long it remains reasonably flat. It also influences it’s feel. A hard stone may also require a more precise technique to achieve optimal results since harder stones may have the tendency to make the blade vibrate or ‘rock’ over the surface.


This aspect may be completely subjective but in the long run it is the most important aspect of any sharpening stone to me. If it doesn’t feel good I will not continue to use it no matter how good it’s performance may be. I love to sharpen and I want it to be enjoyable, if the stone is a struggle it will remain on the shelf.


The amount of time it takes before the pores of a stone fill up with loose metal particles, the stone turns black and it’s efficiency might be decreased.

The Tools Used

Yamahiro, White Steel#1, oire nomi

Kiyohisa, unknown steel, oire nomi

Veritas PM-V11 Blade


All tools where sharpened to a keen edge on a very fine natural finish stone. This sharp edge was set as the reference to start the test with.

The stones where dressed flat with a Atoma diamond plate and checked with a straight edge to verify their flatness.

The Test

I was not able (or willing) to test these stones with all available tool steels. Instead I have used the tools that I use daily and tried to conduct a test which reflect my sharpening method. This test is thus a ‘real life test’, we can’t label it scientific but it closely relates to daily shop practice. The results may remain open to discusion but not to any extend that I doubt them or my conclusions. How my tools perform with these stones is the only thing that really matters to me. I think it is fair to assume that you will have very similar results whatever tool you may use. Especially if you mainly use hand forged Japanese tools.

Assesment Method

The amount of strokes was counted to acquire an even burr along the whole edge. This number of strokes required to produce the burr indicates the speed of the stone.

After each sharpening session or surface flattening, the thickness of the stone was measured at 6 locations. The average of these measurements indicate the amount of wear after sharpening or flattening the stone. It tells us how long the stones remains flat in relation to the amount of strokes used.

It is good to notice that the results are considerably influenced by the freehand technique I use and also by the feel of every specific stone! The blade moves in a different way on either type of stone and thus influences the effectiveness. For example on a specific stone you might have to use more force to hold the bevel steady. Using more downward pressure could influence the amount of abraded steel with every stroke. This means that the results could be different if the same test was performed holding the tool in a jig where almost the exact same movement or pressure can be applied on each stone.


I am aware that the test could be improved in many aspects and therefore I am happy to accept critique. But on the other hand I have no acces to an electron microscope or other high-tech measuring devices and for now the workshop-environment-real-life-test was sufficient.

The Results


The number in the table represents the amount of strokes required to create a burr. The Yamahiro nomi is 30mm wide and the numbers in that row are the actual strokes that were needed to create the burr. For the other tools the number was recalculated since the bevel surface was larger. The numbers in the table represent the number of strokes as if it where tools with the exact same bevel surface area.

In relation to the values, the lower the number the better.



  • Suzuki-ya 4000 is the fastest stone
  • the Shapton 5000 is much slower then I thought
  • my Aoto stone is faster then I thought (except with the PM-V11)
  • Japenese hand forged tools sharpen faster then PM-V11

It is very interesting to notice how the tools are abraded differently by either stone. The statement that ‘every tool has it’s ideal sharpening stone’ is not a myth!


Again lower values represent better performance.



  • Suzuki-ya 4000 wears slightly faster then the Shapton 5000
  • there is a clear relation between the speed and stone-wear
  • my Aoto stone wears relatively fast
  • PM-V11 doesn’t work well with my Aoto


Self explanatory. I didn’t need any measuring devices to asses this criterion. Although that the Suzuki-ya stone is very hard and wear-resistant it has no tendency to make the tool vibrate or rock. It feels as if it was a very soft stone, easy to use and to maintain precise movement and control. You can really concentrate on how the edge is abraded and the stone gives a lot of feedback. Only my Aoto compares to it but this natural stone is more difficult to use.



None of the stones that where tested had any significant amount of imbedded metal particles in it’s surface after one sharpening session. Ceramic stones in general hardly suffer from this aspect but I was surprised by how clean the Suzuki-ya remained. Below a comparison after 150 strokes.


When the picture was taken some of the metal particles had oxidized already, they appear a bit brown. Clogging is certainly not an issue with any of these stones.

The Source

Below are the specs as I received them from Suzuki-san from Suzuki Tool who supplied the stones to me.

-Our man-made or synthetic sharpening stones (waterstones) come from the stone maker directly. They are produced by “vitrification” – a method by which both the ceramic binder and abrasive material are blended under pressure and then baked for 36 hours at an unusually high 1300 degrees celcius (over 2,300 degrees fahrenheit). Stones made in this way are superior not only regarding sharpening speed, but also regarding their durability. The bound particles interact with microscopic air bubbles to create the sense of a brand new stone with every use (time you flatten it) hence the resembling feeling of a natural stone. Because of “vitrification”, they cut faster, stay flat and last longer than others.

-The stone maker’s name: They requested me not to share their name with the public since they usually do business with the middlemen, but not a retail store in Japan.

The main problem I had with these stones is that they are too good. I ended up testing other stones from the same factory a #1000, #1500 and #2000 and decided to buy them all since they all performed superior compared to any of my other synthetic stones. Both my teacher and some colleagues immediately got there own after they had tried mine.

Will I trow away all my other stones? Certainly not and I will keep using them for specific purposes but for everyday fast and reliable sharpening I now have a set of stones that I am truly happy with.

The stones are unique both in performance and availability since only Suzuki-ya sells them. Let me assure you that I have no personal economic interest with this store but I also have no problem directing some attention to it. Her service is simply very professional, she has a lot of experience thanks to her close and ongoing relationship with both the blacksmiths and professional carpenters.

She doesn’t carry a huge stock but is able to get anything you are looking for. It is nice just talking to her because she knows just as much about tools as any daiku does. Convenient shopping they say.

For example, she found us a certain type of Japanese plaster which we thought was discontinued. A few days later we had exactly what we needed and could make our client happy.

It would be nice to do more tests under all kind of circumstances with a decent setup and accurate measuring devices. But even the amateurish test I described here took quite some time and it would need a whole gang of sharpening nerds to get some work done in an acceptable timeframe. Planting a little seed.

Ideally we would have an international standard of testing stone performance. A test everyone could conduct themselves with minimal equipment required. You could then publish your results in a database and over time we would know exactly how stones would perform on any type of given steel. Both Natural and Synthetic.

!Wanted Volunteers for Stone Test Project!