Nubatama Ume #25 (XXXC Black Aratae) HARD

Why You Need This Stone: The #25 grit HARD variant is designed for maximum dish-resistance during extreme metal removal and heavy edge repair. Built in a substantial 50mm "brick" profile for exceptional lifespan under heavy shop use, this extra-extra-extra coarse (XXXC) stone allows you to reshape damaged blades, grind out major chips, and thin heavy stock rapidly without the surface rounding or dishing out under firm pressure.

Buy This Stone If:

• You need an extremely aggressive, fast-cutting coarse stone that maintains flat surface geometry during heavy grinding.
• You want the massive height and long working life of a 50mm brick profile for high-volume shop work.
• You are performing extensive thinning or chip repair where point-pressure would cause softer coarse stones to dish quickly.

Specifications

• Brand: Nubatama
• Grit: #25 (Extra-Extra-Extra Coarse / XXXC)
• Series: Ume (Black Aratae)
• Type: Soaking / Semi-Soaking
• Dimensions / Profile: 210 x 75 x 50mm Brick
• Binder Hardness: Hard
• Provenance: Ken Schwartz Estate

Notes & Usage

• Common Tasks:
  • Grinding out deep edge chips, broken tips, and major bevel damage.
  • Aggressive thinning behind the edge on thick tool steel, heavy kitchen cutlery, or outdoor blades.
  • Establishing initial primary bevels on raw forged blanks or severely out-of-spec edges.
• Cutting Action & Speed: Uses large, coarse silicon carbide particles locked in a firm, wear-resistant binder. It cuts rapidly while releasing minimal surface mud, keeping the contact face flat under heavy hand pressure.
• Surface Feedback: Provides a crisp, firm, and highly tactile feel. The hard bond gives immediate resistance feedback, making it easier to keep primary bevel lines straight.
• Steel Compatibility: Works effectively across all steel types, including hard carbon steels, high-alloy tool steels, and wear-resistant stainless.

Progression Ideas

• Preceding Step (Lower Grit): None (this represents the coarsest bench stone step for heavy manual grinding).
• Following Step (Higher Grit): Nubatama Ume #120 or Bamboo #150 (to refine the aggressive #25 deep scratch pattern before moving into medium repair grits).

Also Consider

• For a Softer / More Slurrying Feel: If you prefer a stone that generates a rich, dark slurry more readily for wide-bevel blending, consider the Nubatama Ume #25 Standard.
• Essential Maintenance: Pair with an extra-coarse diamond flattening plate (e.g., 140 grit) to keep the hard surface dressed and clean during intensive grinding sessions.

Condition

New in original factory box and packaging. Due to long-term storage (5+ years), outer boxes and paper wrapping may show minor shelf wear or scuffing.

Note: Photos represent our stock inventory for this stone; individual box wear or color tone may vary slightly from the unit pictured. Reference objects (rulers, coins) are for scale only and are not included.