Tsuboman - Atoma Diamond Plate - #400

Brand: Imanishi 今西製砥
Product Type: Flattening Stone
Size: 208 x 68 x 33mm
Weight: 847g

For all of your stone flattening needs!

One of our most trusted sources handpicks these stones from the famed Imanishi in Kyoto for us, spending hours testing dozens and dozens and selecting only the best of the best at a variety of price points. These tennen toishi represent some of the best value you will find on the market for natural stones.

These stones are so impressive that they often make you feel like you are "cheating", so to speak - they provide outstanding results at a speed seemingly found only in stones that cost many times more, all while being fun and easy to use - they make it seem as if you have learned years of polishing in a matter of minutes. Combining these gems with the correct steel, you will come to understand the beautiful harmony skilled polishers sometimes have difficulty describing - working on natural stones with well-made knives truly ties the whole subject together.

We are proud to provide such wonderful pieces to you!

Brand: Komon-picked Imanishi
Producing Area: 
Appearance: Near-pure white with the faintest tint of green; a few goma speckled in 
Size: 205mm x 60mm x 38mm
Weight: 901g
~Grit Range: 1500-3000

1-5 Scale: 1 = Less, 5 = More
Hardness Level: 3.5
Scratch Depth: 2.5
Speed: 4
Wear Rate: 2
Self Slurry: 2
Thirst: 2
Consistency: 4.5
Feedback: 2.5
Ease of Use: 3.5

Notes: Koma Nagura stones are a staple in traditional sword polishing progressions—and are often used in razor and fine tool sharpening as well. Pure, high-quality examples like this are increasingly rare, and we’re fortunate to have sourced one. Typically used after Chu Nagura and before Uchigumori, Koma plays a crucial role in refining the foundation polish, allowing Uchigumori stones to fully express their potential. This particular stone is fast-cutting, with black slurry forming in seconds, and it effortlessly removes scratches even from stones more than half its grit level–a polisher dream!

It finishes with a warm, frosty kasumi that’s both beautiful and distinct. Working the jigane for just a few minutes can start to reveal banding, offering exceptional visual depth. Initial feedback has a bit of texture and grip, which quickly smooths out as slurry builds. It’s also hard enough to handle push-cut tools and even Ura on single bevel knives. Obviously effective on knife edges, but given its rarity it is advised that it be mostly reserved for polishing or wide bevel applications. For faster cutting and more even feedback, using a nagura, preferably a tomo nagura, could help. 

Simply put, this is an incredible find for anyone building a premium polishing progression—or a collector seeking something truly special.

Recommended Usage: Pre polisher, frosty kasumi, gnarly edges, push cut tools

Disclaimer: Given the natural aspect of these stones, all graded characteristics are our own subjective thoughts which may vary from your expectations and assessment. The images shown and characteristics described may be from a previous, random example, or when first measured before being tested numerous times. If purchased, yours may differ slightly in appearance and qualities. All stone sales are final.

One of our most trusted sources handpicks these stones from the famed Imanishi in Kyoto for us, spending hours testing dozens and dozens and selecting only the best of the best at a variety of price points. These tennen toishi represent some of the best value you will find on the market for natural stones.

These stones are so impressive that they often make you feel like you are "cheating", so to speak - they provide outstanding results at a speed seemingly found only in stones that cost many times more, all while being fun and easy to use - they make it seem as if you have learned years of polishing in a matter of minutes. Combining these gems with the correct steel, you will come to understand the beautiful harmony skilled polishers sometimes have difficulty describing - working on natural stones with well-made knives truly ties the whole subject together.

We are proud to provide such wonderful pieces to you!

Brand: Komon-picked Imanishi
Producing Area: Kyoto - Japan
Mine: Monzen
Appearance: A mix of Asagi and Yake, peppered with Aka Renge and subtle Iromono at play when wet
Size: 227mm x 87mm x 35mm
Weight: 1728g
~Grit Range: 3000-4000

1-5 Scale: 1 = Less, 5 = More
Hardness Level: 3.5
Scratch Depth: 1.5
Speed: 5
Wear Rate: 1.5
Self Slurry: 3.5
Thirst: 2
Consistency: 5
Feedback: 2.5
Ease of Use: 5

Notes: Wow, this is an INCREDIBLE stone! Not only does it have a larger than usual surface area (and will last many years), it is extremely fast, easy to use, and gives stellar results. It will awesome for knives, but it is perfect for push cut tools thanks to its firmness, fineness, and size. It is extremely consistent in feedback and its entire surface. This is a "true" Monzen and very difficult to find vs. others that are much coarser and very soft and muddy which typically come from higher, easier to access strata. Perfect for both beginners and high level professionals.

Recommended Usage: General wide bevel work; frosty Kasumi; mid sequence polisher; crisp edges; push cut tools.

Disclaimer: Given the natural aspect of these stones, all graded characteristics are our own subjective thoughts which may vary from your expectations and assessment. The images shown and characteristics described may be from a previous, random example, or when first measured before being tested numerous times. If purchased, yours may differ slightly in appearance and qualities. All stone sales are final.

One of our most trusted sources handpicks these stones from the famed Imanishi in Kyoto for us, spending hours testing dozens and dozens and selecting only the best of the best at a variety of price points. These tennen toishi represent some of the best value you will find on the market for natural stones.

These stones are so impressive that they often make you feel like you are "cheating", so to speak - they provide outstanding results at a speed seemingly found only in stones that cost many times more, all while being fun and easy to use - they make it seem as if you have learned years of polishing in a matter of minutes. Combining these gems with the correct steel, you will come to understand the beautiful harmony skilled polishers sometimes have difficulty describing - working on natural stones with well-made knives truly ties the whole subject together.

We are proud to provide such wonderful pieces to you!

Brand: Komon-picked Imanishi
Producing Area: Kyoto - Japan
Strata: Suita
Appearance: Stunning white and light-gray surface with some small Aka Renge. A large number of visible Su. Some, only one can be very faintly felt but has no negative effects.
Size: 212mm x 80mm x 40mm
Weight: 1614g
~Grit Range: 2500-4000

1-5 Scale: 1 = Less, 5 = More
Hardness Level: 2.5
Scratch Depth: 2
Speed: 4
Wear Rate: 2
Self Slurry: 3.5
Thirst: 2.5
Consistency: 4
Feedback: 2
Ease of Use: 4

Notes: A beautiful stone both aesthetically and for polishing results - great coloring effects, leaves a soft transition at the cladding line. A very consistent, easy to use, and very, very fast stone. A very fine black slurry forms pretty much immediately, and a gray slurry when working the whitter spots, and working the slurry further creates an incredibly smooth feedback. Scratches are incredibly uniform and pretty shallow. You could finish on this for a frosty kasumi, or has a really fast pre polisher for something brighter. Pretty much an ideal stone for wide bevels. It feels almost pillowy-soft and has a slightly chalky feedback almost akin to working a Nagura, in fact you could largely substitute one for another. Given its ease of use intermediate users could quickly benefit, but you would certainly find this in a professional polishers arsenal.

Recommended Usage: Pre-polishing, final polish, super refined edges. Could be used for push cuts if used with light pressure. 

Disclaimer: Given the natural aspect of these stones, all graded characteristics are our own subjective thoughts which may vary from your expectations and assessment. The images shown and characteristics described may be from a previous, random example, or when first measured before being tested numerous times. If purchased, yours may differ slightly in appearance and qualities. All stone sales are final.

One of our most trusted sources handpicks these stones from the famed Imanishi in Kyoto for us, spending hours testing dozens and dozens and selecting only the best of the best at a variety of price points. These tennen toishi represent some of the best value you will find on the market for natural stones.

These stones are so impressive that they often make you feel like you are "cheating", so to speak - they provide outstanding results at a speed seemingly found only in stones that cost many times more, all while being fun and easy to use - they make it seem as if you have learned years of polishing in a matter of minutes. Combining these gems with the correct steel, you will come to understand the beautiful harmony skilled polishers sometimes have difficulty describing - working on natural stones with well-made knives truly ties the whole subject together.

We are proud to provide such wonderful pieces to you!

Brand: Komon-picked Imanishi
Producing Area: Kyoto 
Mine: Hideriyama 
Strata: Suita
Appearance: Asagi green with streaks of Namazu
Size: 2,567g
Weight: 238mm x 75mm x 73mm
~Grit Range: 3000-5000

1-5 Scale: 1 = Less, 5 = More
Hardness Level: 2.5
Scratch Depth: 2.5
Speed: 4
Wear Rate: 3
Self Slurry: 4
Thirst: 3.5
Consistency: 5
Feedback: 3
Ease of Use: 4

Notes: An extremely rare vintage Hideriyama Suita, especially in this large format. A true pleasure to use — it offers silky feedback with a slurry that develops quickly and yields an exceptionally consistent scratch pattern. The resulting kasumi finish is warm and rich and can be achieved with ease and speed. Depending on your approach, you can stop early for a hazy-to-frosty kasumi, or continue on in your polishing sequence for a brighter finish.

Thanks to its generous surface area and substantial thickness, this stone will provide years of use. However, as it’s not particularly hard (though not overly soft either), it’s important to work the surface evenly to avoid localized dishing. It’s likely too soft for push-cut tools, but perfect for wide bevel polishing, even convex grinds.

This is an outstanding stone for collectors due to its rarity, quality, and vintage provenance. While best suited for intermediate to advanced users, its forgiving nature also makes it accessible to mindful beginners.

Recommended Usage: Hazy to frost kasumi, pre or pre pre polisher, convex grinds, refined but textured edges.

Disclaimer: Given the natural aspect of these stones, all graded characteristics are our own subjective thoughts which may vary from your expectations and assessment. The images shown and characteristics described may be from a previous, random example, or when first measured before being tested numerous times. If purchased, yours may differ slightly in appearance and qualities. All stone sales are final.

Please Note: These pictures and measurements are examples. Your specific product may differ slightly in appearance and measurements.