What are Arato, Naka-to and Awasedo stones?

The japanese natural stones They are traditionally grouped into three fundamental categories: Aratus, Naka-to and Awasedo. Each one fulfills a precise function in the sharpening process: extracting material, defining the bevel or polishing to the maximum level of fineness. Understanding the difference between them helps you choose the proper sequence for repairing, sharpening, and finishing any edge.

Arato, Naka-to and Awasedo stones are the three main categories of sharpening stones Japanese natural blades (Jnats), classified according to their grain and the stage of the sharpening process for which they are used. These stones are valued for their ability to extract, shape, sharpen and polish cutting tools with great precision.

Overview: What sets each category apart

In the practice of sharpening with natural Japanese stones (known as Tennen Toishi or JNATS), the three categories can be understood like this:

• Arato (荒砥 / Aratoishi): coarse-grained stones, intended for roughing and repair.
• Naka-to (中砥 / Nakatoishi): medium grain stones that refine and stabilize the angle of the bevel.
• Awasedo (合わせ砥): stones of finishing that polish and raise the edge to maximum performance.

Why is a natural stone considered valuable?

• It must be harder than steel worked and release abrasive particles in a controlled manner.
• Its internal structure must be homogeneous, to avoid irregular marks.
• It must operate with water (lubrication) and produce a slurry that provides control and abrasive action.

Arato: the rapid elimination stage

Aratus They are stones designed to remove a lot of material in a short time. Its main utility is:

• Repair nicks depths and edge deformations.
• Reprofile the bevel when you want to change the angle or recover damaged geometry.
• Prepare the blade for the finer stages.

Technically they are usually sandstones or larger grain sedimentary rocks; Its behavior can approach low grain synthetics (approximately sub-1000 in variable equivalence). Its use produces a thick slurry and requires re-leveling the stone more frequently.

Naka-to: the bridge between strength and precision

Naka-to It acts as a transition: it softens the marks left by the Arato and begins to give practical sharpness to the edge. Features:

• Refine deep scratches without needing the time of an Awasedo.
• Provides a usable edge for everyday work.
• Approximate equivalence with medium synthetic grain (1000–3000, very indicative).

Naka-to are extracted from shales, tuffs or fine volcanic rocks. For many professionals this is the most used stone, because it offers a balance between speed and finish.

Awasedo: polishing and maximum performance

Awasedo group the stones finishing. Its goal is to produce an extremely fine edge and, in many cases, a mirror finish. Key details:

• Typical materials: ganister and silica shale, rich in silica and very homogeneous.
• Capable of very high synthetic equivalences (6000–8000+), and in certain specimens the sensation approaches 10,000 or more.
• They allow aggressiveness to be adjusted by nagura (auxiliary stones) that generate slurry to vary between cutting and polishing.

A correct Awasedo delivers a feedback soft touch, produces a fine scratch pattern and can improve edge retention due to the random nature of the natural abrasive.

How to use them together: a practical sequence

• Arato → Naka-to → Awasedo: complete sequence when the leaf is badly damaged.
• Naka-to → Awasedo: enough for regular sharpening without severe damage.
• Only Naka-to: practical option for heavy-duty tools or when you are not looking for a mirror finish.

Practical tips

• Evaluate the edge before starting: it is not always necessary to start with Arato.
• Use water and control the slurry: vary the sensation and the final result.
• Level the stones periodically to maintain an even bevel.

Geology and provenance: why Kyoto matters

Classical quarries around Kyoto (Shohonyama area) supply many Arato, Naka-to and Awasedo prized for their uniformity and silica content. Names like Nakayama, Atagoyama or Okudo They identify specific strata whose sharpening behavior has been valued for centuries.

Knowing the function and origin of each type of stone allows you to plan a more effective sharpening: from correcting severe damage to achieving a razor-sharp, visually impeccable edge.

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