ウェブサイトとは何ですか？

Japanese Natural whetstone

ホーム
日本
Yokohama, Kanagawa
Japanese Natural whetstone

I sell Japanese natural whetstones. I have a track record of trading over 4000

07/09/2026

If you are interested in this Nakayama Suita, please send me a direct message.

102mm×87mm×26mm
568g

03/09/2026

This is truly beautiful.

03/09/2026

If you are interested in this Nakayama Suita, please send me a direct message.

01/09/2026

● Ohira Mine Suita Renge
● Yellowish Suita from Ohira Mine
● Old Nakayama Mine Suita with a Nashiji (pear-skin) texture

It’s interesting to compare these three stones and see how differently they perform during sharpening.

29/08/2026

This is a rare Karasu from Nakayama Mine.

It is an impressive size, and pieces like this are extremely difficult to find.

The stone offers an exceptionally fine finish, approximately 8,000〜30,000 grit.

A beautiful piece of Japanese natural sharpening stone, ready to be enjoyed at the sharpening bench.

Enjoy the sharpening. 🇯🇵

28/08/2026

The black patterns look like plant fossils.
However, they are not fossils, but dendrites (branch-like crystal formations) formed by manganese oxides.
A beautiful natural pattern unique to natural whetstones.

27/08/2026

This is a Kiita from the Nakayama mine, with a rare Enmaki pattern on the back side.

The hardness is also quite unusual. The front side is around medium hardness, perhaps slightly on the softer side, and I think it would be very good for kitchen knives.

I haven’t flattened the back side, so I can’t say for sure about its hardness, but it may be harder than medium.

I think this stone would be particularly well suited for kitchen knives and woodworking tools.

27/08/2026

This natural stone is on the softer side and doesn’t have much polishing power. It’s a natural stone that’s well suited for kasumi finishing.

26/08/2026

Why is Diamond Not Ideal for Grinding Iron?

Diamond is an extremely hard abrasive, but it is not well suited for grinding iron.

Grinding heat can cause iron to adhere to the diamond grains, leading to loading, increased heat, and reduced cutting performance.

In contrast, CBN is highly suitable for hardened steel and other ferrous materials, and remains stable at high temperatures.

👉 CBN for steel. Diamond for carbide, ceramics, glass, and non-ferrous materials.

⸻

なぜダイヤモンド砥石は鉄の研削が苦手なのか？

ダイヤモンドは非常に硬い砥粒ですが、鉄との相性は良くありません。

研削熱によって鉄がダイヤモンド砥粒に付着しやすく、目詰まり・発熱・切れ味低下につながります。

一方、CBNは焼入れ鋼などの鉄系材料に適しており、高温でも安定しています。

👉 鉄鋼材料にはCBN、超硬・セラミックス・ガラス・非鉄金属にはダイヤモンド。

25/08/2026

同じ「 #1000」でも、面粗さは同じではないです。

研削工作機械と手研ぎでは、砥石の使われ方が大きく異なります。

機械研削では、砥石が高速回転し、CBNやダイヤモンドなどの砥粒が連続的に切削します。
一方、手研ぎでは低速で、砥石・刃物・手の圧力などの影響を受けながら研磨されます。

さらに、砥粒の種類、ボンド（結合剤）の強さ、砥粒の突出量、切込み、送り、冷却条件などによっても仕上がりは変わります。

つまり、

「番手が同じ＝同じ面粗さ」ではない。

特に、機械研削用の人造砥石と手研ぎの人造砥石・天然砥石の「 #1000」を単純に比較することはできません。

砥石の番手は、あくまで仕上がりを決める要素の一つです。

⸻

Even the same “ #1000 grit” does NOT necessarily produce the same surface finish.

Machine grinding and hand sharpening use abrasive stones in very different ways.

In machine grinding, the wheel rotates at high speed, and abrasives such as CBN or diamond continuously cut the workpiece.

Hand sharpening, on the other hand, is performed at very low speed, and the result is strongly affected by the stone, blade, hand pressure, and sharpening technique.

Surface roughness also depends on factors such as abrasive type, bond strength, grain protrusion, depth of cut, feed rate, and coolant conditions.

In other words:

“Same grit number ≠ same surface roughness.”

A #1000 machine grinding wheel and a #1000 natural sharpening stone should not be simply compared by their grit numbers alone.

The grit number is only one of many factors that determine the final surface finish.

住所

Yokohama, Kanagawa
2440003