Shapton Kuromaku Sharpening Stone - #320 Blue/Black
Whetstone — ToishiThe Shapton Kuromaku #320 Blue/Black is the coarsest stone in the Kuromaku series and handles the "restoration" phase of the sharpening process. The Blue/Black color combination defines the most aggressive stone in the series. This stone comes into play for bringing broken, deeply chipped, or incorrectly angled knives back to life; or for giving a new knife a different edge geometry.
Kuromaku #320: The Strongest Link in the Series
The Kuromaku series is generally known for its fineness and precision; however, the #320 shows a different side of this series. Its resin binder technology provides controlled and predictable metal removal even at this coarse grit level. A common problem encountered with coarse stones from other brands – uneven wear of the stone and rapid degradation of the surface – is minimized in Kuromaku's formulation. The Blue/Black color code is the code for the #320 grit within Kuromaku.
#320 Grit: When to Use It?
This stone is not used in every sharpening session. The situations in which it is used are:
- There are chips or deep nicks on the knife's edge
- The knife's edge has been sharpened at the wrong angle and needs to be completely reset
- Knives that have been used for a long time and are excessively dull
- A new knife needs a different edge angle (e.g., from 20° to 15°)
- A traditional double-beveled (symmetric) knife is to be converted to a single-beveled (asymmetric) geometry
After #320, the chain of #1000 → #3000 → #5000 → #8000 must be followed. This stone alone will never provide sufficient sharpness; its purpose is to shape the edge and repair damage.
Technical Specifications
- Grit: #320
- Color code: Blue/Black (Kuromaku's coarsest stone)
- Binder: Shapton patented resin (vitrified bond)
- Abrasive: Aluminum oxide
- Water requirement: A few drops – no pre-soaking needed
- Metal removal: Very high
- Function: Restoration / reshaping / angle change
- Compatibility: All steel types
Who is it suitable for?
It is designed for knifemakers, enthusiasts interested in restoring second-hand knives, kitchen equipment repairers, and advanced users who want to fundamentally renew their knives. For home users, this stone is also extremely useful during the annual "major maintenance" of knives – especially for compensating for accumulated neglect.
Usage Tips
- You can apply more pressure to this stone – coarse grit can handle it
- Do not switch to the other side before completely finishing one side; observe burr formation along the edge
- Regularly check the flatness of the stone – coarse stones dish faster
- Before moving from #320 to #1000, examine the coarse scratches on the edge under light; all nicks should be gone
- Use the stone with plenty of water – if too much metal dust accumulates, efficiency decreases
Care and Storage
Coarse stones are the ones that accumulate the most metal dust. Clean and rinse thoroughly with a brush after each use. Regularly flatten the stone's surface with coarse lapping powder – the #320 dishes faster than other stones. A clean and flat #320 stone can handle the toughest restoration tasks for decades.
Shipping Information
Orders placed by 2 PM are shipped the same day. Free shipping on orders over ₺1,000. Sharpening stones are sent in special protective foam packaging.
Returns & Exchanges
30-day unconditional return guarantee. The product must be in its original packaging and unused. If a manufacturing defect is found in the stone, an exchange will be made without a time limit.
Stone Care
After use, wash the stone with warm water and allow it to air dry. If the stone surface becomes uneven (dishing), correct it with a flattening stone. Protect the stone from direct sunlight and frost.
What is Grit? Which Stone Should I Choose?
Grit number indicates the abrasive grain density of the stone. A low number means coarser (fast material removal), and a high number means finer (polishing and finishing).
Technical
How to Know?
Sharpening with a Japanese whetstone involves 5 fundamental steps. When you correctly follow each step, your knife will return to its factory sharpness.
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Name 1Soak the Stone
FloodedSubmerge the stone in clean water and wait until air bubbles completely stop. This can take between 5-15 minutes, depending on the type of stone.
Tip: Important: Do not soak splash-and-go type stones (like Shapton Pro) in water — just wet the surface. -
Name 2Adjust the Angle
Angle SettingPlace the knife against the stone at approximately a 15° angle. Hold the knife steady by applying light pressure to the blade surface with your index and middle fingers.
Tip: Easy method: Lay the knife flat on the stone, then lift the spine by the thickness of two coins — this is approximately 15°. -
Name 3Sharpen
To honeSlide the blade back and forth along the stone. Divide the blade into 3 sections from tip to heel and apply 20-30 strokes to each section.
Tip: Pressure: Light pressure on the forward stroke, no pressure on the backward stroke. The stone's own abrasiveness is sufficient. -
Name 4Finishing & Washing
Clean up the burrs on both sides with a few light strokes. Wash the blade with warm water and dry it. Also wash the stone and let it air dry.
Tip: Test: Hold a sheet of paper in the air and cut it — if it cuts cleanly and smoothly, the sharpening was successful.
Which knives is it used on?
Steel Types
- VG-10 (Stainless)The most common Japanese steel — excellent conformity
- Aogami Super (Carbon)High carbon — fast and effective sharpening
- SG2/R2 (Powder Metallurgy)Hard steel requires patient grinding
- German Steel (X50CrMoV15)Mild steel — sharpens very quickly
- Ceramic KnifeDiamond requires a stone — aquamarine is not suitable
Types of Knives
- Gyuto (Chef's Knife)210mm and above — fully compatible
- Santoku170mm — this is the ideal size for this stone
- Nakiri (Vegetable)Straight edge — easy sharpening
- Petty (Theft)Small knife — precise sharpening
- Serrated Bread KnifeIt can't be sharpened with a flat stone — it needs a special rod-shaped stone.
Suggested Sharpening Angles
- 10-12° Yanagiba / Sashimi
- 15° Japanese KnivesÖnerilen
- 20° Western / German Knives
Give Your Knives the Care They Deserve
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Frequently Asked Questions
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Is this a Splash & Go stone, or does it require soaking?
The Shapton Kuromaku series is a Splash & Go type. Just sprinkle water on its surface before use; there's no need to immerse it in water. Ensure the surface remains moist during sharpening. This feature offers great convenience compared to traditional stones — you can start using it immediately.
My whetstone has dished, what should I do?
Use a flattening stone. Sharpening stones wear down and become concave over time. This distorts the sharpening angle and prevents even sharpening. Flatten the stone by moving the flattening stone back and forth on a wet surface. Draw a pencil grid — when the lines are completely erased, the stone is flat. Check out our flattening stones.
Is one stone enough, or should I buy a set?
A #1000 grit stone is sufficient to start. For weekly sharpening in a home kitchen, a #1000 grit stone will get the job done. However, if you want to get maximum performance from your kitchen knife, we recommend a #1000 + #3000 grit double set — the first sharpens, the second polishes. For professional use, the #320 + #1000 + #5000 triple set is ideal.
Can this stone also be used with German/Western knives?
Yes, it can be used on all metal knives. It also perfectly sharpens Western knives such as Wüsthof, Zwilling, and Victorinox. The only difference is the sharpening angle: use 15° for Japanese knives and 20° for Western knives. Since German steel is softer, the sharpening time will be shorter.
How should I store and care for the stone?
Wash after use and allow to air dry. Never store the stone wet in a closed box — it may develop mold. Protect from direct sunlight and frost. Shapton Kuromaku stones can be stored in their own plastic cases (the case also doubles as a stone holder). If not to be used for a long time, store in a dry and cool place.
Is a stone holder necessary?
We strongly recommend it for safety. A whetstone slipping during sharpening is both dangerous and reduces the quality of the sharpening. The silicone stone holder keeps the stone stable and protects your countertop from scratches. The plastic case of the Shapton Kuromaku can also be used as a basic holder, but the professional silicone holder provides a much more stable sharpening experience.
Give Your Knives a New Life
Centuries of Japanese waterstone technology, in your hands. More than a stone — an investment in every knife in your kitchen.
Add to Cart — 3,300.00TL