Let’s see what the abrasives commonly used for sharpening are based on and their grits.

This technical topic is very important for a maker because the last phase, the sharpening phase, is complex and it is not easy to achieve 100% satisfactory results.

Grain refers to the degree of roughness of the stone , and is an indicator of greater or lesser aggressiveness and as with the abrasive belts of the sander or the common sandpaper that you use for finishing, the lower the number indicated, the more it abrades.

Now, however, it is not necessarily true that an aggressive grit in sharpening stones must necessarily abrade faster, since this is determined not only by the grit but also by other factors, such as:

• the hardness in HRC ,
• the composition,
• etc.

For example, diamond stones, for example, abrade faster with the same grit.

Sharpening Stones: The 5 Main Macrogroups

In the world of sharpening, sharpening stones are indispensable tools for maintaining or restoring the edge of knives, tools and blades of all kinds. To choose the right one, it is essential to understand the different types available and their characteristics.

Stones are divided into 5 main macro groups , each with specific materials, methods of use and purposes. From traditional oil stones to modern diamond stones, each group offers advantages and disadvantages based on the needs of the user and the type of blade to be treated.

In this guide we will explore the 5 main groups of sharpening stones:

1. Oil Stones: Traditional and versatile, ideal for precision finishing.
2. Japanese Water Stones: Perfect for quick sharpening and shiny edges.
3. Diamond Stones: Powerful and long-lasting, ideal for very hard steels.
4. Ceramic Stones: Focused on polishing and extreme finishing.
5. Synthetic Stones: Economical and practical, suitable for beginners and general use.

Each group has unique characteristics that make it suitable for specific sharpening jobs. Let’s find out together which one to choose for your needs!

Oil Sharpening Stones

Oil stones are one of the most traditional and versatile types, known for their ability to work on hard steels and produce sharp, durable edges. These stones can be either natural or synthetic and are designed to be used with oil as a lubricant, which reduces friction and prevents clogging of the surface.

Types of Oil Stones

1. Natural Stones:
   • Arkansas (Novaculite):
     • High quality American stones, mainly used for the final stage of sharpening.
     • They offer excellent edge polishing and are particularly hard and resistant.
     • Ideal for obtaining a smooth and shiny thread.
   • European coticule and Belgian Blue:
     • European stones with high silica content, perfect for precision sharpening.
     • Rare and expensive, but they offer a unique experience for those looking for a high-end natural finish.
2. Synthetic Stones:
   • Aluminium Oxide (e.g. Norton India):
     • Suitable for a wide range of applications, they offer a sharp and precise edge.
     • Versatile and usable for kitchen knives, outdoor knives and work tools.
   • Silicon Carbide (e.g. Norton Crystolon):
     • Very hard material, slightly harder than diamond.
     • Ideal for rapid roughing and for sharpening very hard steels (HRC up to 64).

Classification of Oil Stones by Use

Characteristics of Oil Stones

1. Available Grits:
   Oil stones cover a range of grits, from coarse for roughing to fine for polishing:
   • Grits 220-400: For roughing and repairing damaged threads.
   • Grits 800-1200: For general sharpening.
   • Grits above 3000: For precision polishing and finishing.
2. Use with Oil:
   Oil acts as a lubricant, improving the knife’s glide across the stone and reducing the build-up of metal residue.
   • Type of oil: Light oil specifically for sharpening, never use oils that are too thick or unsuitable.
3. Maintenance:
   • With use, they will wear down and may require grinding to maintain a uniform surface.

Benefits of Oil Stones

1. Durability: Natural stones, such as Arkansas, last for years with proper maintenance.
2. Affordable Cost: Synthetic stones made of aluminum oxide or silicon carbide are generally inexpensive.
3. Versatility: They can be used on a wide range of knives and steels, including those with high HRC.
4. Precise Finish: Natural oil stones provide a high-end polish, perfect for that finishing touch.

Defects of Oil Stones

1. Slowness: Abrasion is slower than other types of stones, such as diamond or water stones.
2. Using Oil: While effective, it requires more maintenance than using water, and oil may be less practical to handle.
3. Grinding Required: Stones must be grinded regularly to ensure a flat, even surface.

When to Choose Oil Stones

• Traditional Sharpening: If you are looking for a traditional and precise experience, especially for finishing work.
• Hard Steels: Perfect for resistant steels, thanks to their ability to work at fine grains.
• Professional Finish: Suitable for polishing and perfecting the edge on high quality knives.

Oil stones are a versatile and traditional choice for those who want to sharpen and polish with precision. While they are slower and require more maintenance than other types, their affordability and durability make them a reliable solution, especially for finishing. Perfect for those who want maximum control when sharpening and appreciate a classic approach.

Japanese Water Sharpening Stones

Japanese water stones are among the most popular in the sharpening world due to their ability to quickly abrade and polish the edge impeccably. Although today they are mainly synthetic, they faithfully reproduce the characteristics of natural Japanese stones, making them indispensable for those who want high-precision sharpening.

Composition and Operation

• Material:
  Composed of silica particles (usually aluminum oxide) mixed with a clay matrix.
• Soft Structure:
  The softness of the stones allows the abrasive particles to continuously renew themselves during use, creating a sort of dough with the water ( slurry ), which helps polish the edge as it sharpens.

Main Features

1. Available Grits:
   Japanese water stones cover a wide range of grits, from coarse for roughing to ultra-fine for polishing.
   • 240-400: For roughing and repairing damaged threads.
   • 800-1000: For sharpening and sharpening the edge.
   • 3000-6000: For polishing and refining the edge.
   • 8000+: For extreme polishing, ideal for high quality Japanese razors or knives.
2. Use with Water:
   They should be soaked in water for 5-10 minutes before use and kept moist during sharpening. This facilitates abrasion and prevents clogging of the stone.
3. Grinding Required:
   Being soft, they wear quickly and must be grinded regularly to maintain a flat surface.

Advantages of Japanese Water Stones

1. Speed: They abrade faster than oil stones, saving time when sharpening.
2. Polishing the Wire: The mixture formed with the water allows you to obtain a smooth and shiny wire.
3. Tradition and Precision: Used for centuries by Japanese master sharpeners , they deliver exceptional results, particularly on Japanese kitchen knives and high-quality blades.
4. Ease of Use: Water is cheaper and easier to handle than oil.

Defects of Japanese Water Stones

1. High Cost: Higher quality stones can be expensive, especially fine grained ones.
2. Quick Wear: The soft structure makes them more subject to wear than other stones.
3. Frequent Maintenance: Require regular grinding to maintain an even surface.

When to Use Japanese Water Stones

• Japanese Kitchen Knives: Perfect for sharpening and polishing knives with narrow cutting angles (12-15°).
• Precision Razors and Blades: Ideal for achieving a mirror finish and a surgical cut.
• High Quality Sharpening: Recommended for fine knives and high-hardness steels (HRC 58+).

Tips for Use

1. Soaking: Soak the stone in water for at least 5-10 minutes before use. Make sure the water completely penetrates the stone (no air bubbles).
2. Keep It Moist: While sharpening, spray water regularly to keep the surface lubricated.
3. Grinding: Use a leveling stone or abrasive surface to grind it down after a few sessions.
4. Grain Progression: Follow a logical sequence (e.g. 1000 → 3000 → 6000) to get the best results.

Japanese water stones are the gold standard for high-quality sharpening. While they require an initial investment and regular maintenance, they offer unmatched results in terms of precision and polishing. If you are a keen sharpener or work with fine knives, these stones are a must!

Dry Diamond Sharpening Stones

Diamond stones represent the pinnacle of sharpening because they can work on any steel, even the hardest. Made of metal plates with diamond particles glued to the surface, they offer superior speed and efficiency compared to other stones, making them ideal for difficult and intensive work.

Main Features

1. Material:
   • They use diamond, the hardest material in the world, for fast and effective abrasion.
   • Suitable for sharpening steels with high HRC (60+), such as high quality stainless or carbon steels.
2. Available Grains:
   • From Extra-Coarse (220) to Extra-Fine (1200), they cover all stages of sharpening.
3. Dry Use:
   • They can be used without lubrication, making them extremely practical. Alternatively, a light spray of water can help remove metal residue.
4. Duration:
   • They do not wear out like traditional stones, since the metal does not deform and diamonds maintain their effectiveness for a long time.

Advantages of Diamond Stones

1. Suitable for All Steels: There is no steel that cannot be worked with a diamond stone, even the hardest ones like D2, S30V or advanced stainless steels.
2. Speed: Abrasion is much faster than traditional stones, making them ideal for repairing damaged edges or for roughing out.
3. Durability and Stability: No deformation and no grinding required, saving time and effort.
4. Versatility: Available in many grits, they can do everything from roughing to light polishing.

Defects of Diamond Stones

1. Cost: Quality diamond stones are more expensive than natural or synthetic ones.
2. Particle Loss: In some low-quality stones, diamond particles can detach from the backing, compromising their effectiveness.
3. Limited Feel: Compared to natural stones, they offer less tactile feedback, which can make sharpening less intuitive.
4. Abrasiveness: If used incorrectly, they can damage the edge, creating deep scratches or removing too much material.

When to Use Diamond Stones

• Repair: Perfect for knives with badly damaged edges or nicks.
• Sharpening of Very Hard Steels: Essential for modern steels with high carbon content or complex alloys.
• Precision and Speed: Ideal for those looking for speed and professional results without compromise.

Tips for Use

1. Light Pressure: Let the diamonds do the work. Too much pressure can damage the wire or detach the particles from the backing.
2. Cleaning: After each use, remove metal residues with a soft brush or damp cloth.
3. Progression: Follow a sequence of steps, for example:
   • 220-325 for roughing and repairing.
   • 600-1200 for sharpening and light polishing.

Diamond stones are indispensable tools for those who work with hard steels or for those who want speed and efficiency. Although they are more expensive and have a different feel than natural stones, their durability and versatility make them an indispensable investment for experienced sharpeners and professionals.

Ceramic Sharpening Stones

Ceramic sharpening stones are high-precision tools, primarily used for the final stage of sharpening . Thanks to the extremely hard material and very fine grits, these stones are ideal for achieving a smooth, mirror-like finish on the edge of the knife. Their durability and practicality make them a popular choice among the most demanding users.

Main Features

1. Fine and Ultra-Fine Grits:
   • Ceramic stones are mainly available in grits above 1000, perfect for polishing the edge.
   • Ideal for precision work on high quality knives or professional tools.
2. Hard and Durable Material:
   • Ceramic is extremely wear-resistant and maintains its effectiveness for a long time.
   • It does not require frequent adjustments like water or synthetic stones.
3. Serrated Blade Stick:
   • Also available in stick form, designed to effectively sharpen serrated blades, which are difficult to sharpen with other types of stones.
4. Dry Use:
   • They do not require lubrication with water or oil, making the sharpening process easier and quicker.

Advantages of Ceramic Stones

1. Precision: They allow you to obtain a perfectly polished and sharp edge, ideal for kitchen knives, razors and precision instruments.
2. Durability: Due to their resistance, they wear out very slowly compared to other stones.
3. Ease of Maintenance: They require no immersion or lubrication, nor frequent adjustments.
4. Suitable for Serrated Blades: Ceramic sticks offer a practical solution for these types of blades.

Disadvantages

1. High Cost: Compared to other types, ceramic stones can be more expensive.
2. Lack of Versatility: They are not ideal for roughing out or repairing damaged threads.
3. Limited Feedback: They offer less tactile sensation than natural stones or water, which can make them less intuitive for beginners.

When to Use Ceramic Stones

• Final Stage: Use as the last step after working with water, diamond or synthetic stones to obtain an extremely sharp and shiny edge.
• Precision Knives: Perfect for razors, Japanese knives or tools that require a high level of finish.
• Serrated Blades: Ceramic sticks are essential for effectively sharpening the teeth of these blades.

Tips for Use

1. Cleaning: After use, clean the stone with a soft brush and water to remove metal residue.
2. Light Pressure: Use gentle movements to avoid damaging the edge or the surface of the stone.
3. Progression: Move to a ceramic stone only after working the edge with a medium grit stone (e.g. 1000-3000).

Ceramic stones are indispensable tools for those who want maximum precision and durability in their sharpening process. Although they are best suited to expert users, with a little practice they can offer professional results even to beginners.

Synthetic Sharpening Stones

Synthetic sharpening stones are a versatile and economical solution, often used in small sharpening kits. Due to their artificial composition, they are designed to adapt to a variety of needs, from restoring the edge to general sharpening. They are a popular choice for beginners and users looking for convenience.

Main Materials

1. Tungsten Carbide:
   • Features: Extremely hard material, ideal for very hard steels.
   • Use: Perfect for quick abrasive sanding, but leaves a rather coarse finish.
   • Typical application: Quick repairs and outdoor or work knives.
2. Aluminum Oxide:
   • Features: Common material in synthetic stones, versatile and suitable for a wide range of knives.
   • Use: Ideal for sharpening kitchen knives and for regular maintenance.
   • Advantage: Suitable for both beginners and intermediate users.
3. Silicon Carbide:
   • Characteristics: Very hard material, just a little harder than diamond.
   • Use: Perfect for roughing out and repairing badly damaged threads.
   • Typical application: Hunting knives, outdoor knives and high HRC steels.

How to Use

• Dry:
  • Often used dry for convenience, especially in portable kits.
• With Oil:
  • In some cases, they may be lubricated with oil to improve smoothness and reduce the accumulation of metal residue.

Advantages of Synthetic Stones

1. Versatility: Available in a wide range of grits to tackle different stages of sharpening.
2. Affordable Cost: Often cheaper than natural or diamond stones.
3. Durability: Durable materials that tolerate heavy use.
4. Suitable for Beginners: The ease of use makes them perfect for those who are new to sharpening.

Disadvantages

1. Coarse Finish: More aggressive grits may leave noticeable marks on the edge, requiring additional polishing steps.
2. Maintenance: May require frequent sanding to maintain a flat surface.
3. Touch Sensation: Compared to natural stones, they may offer less “feedback” while sharpening.

When to Choose Synthetic Stones

Synthetic stones are ideal if:

• You need an economical option for general use.
• Do you want a practical tool for sharpening work or kitchen knives?
• Looking for a portable solution for sharpening or repairing damaged knives?

With proper use and proper grit progression, these stones offer solid performance for a wide range of applications.

Strop and Compound: Final Polishing of the Edge

Strops and compounds are essential tools for perfecting your sharpening and achieving a flawless finish. While they are not abrasive stones, they are used for the same purpose: to improve the knife’s edge and polish it, removing microscopic burrs.

What Are Strops and Compounds?

• Stroke:
  • It is a strip of natural or synthetic leather used to polish the thread.
  • It serves as the final stage after sharpening, to obtain an extremely sharp and mirror-like edge.
• Compound:
  • They are abrasive pastes applied to the strop to improve the effectiveness of the polishing.
  • Each compound has a specific degree of abrasiveness, indicated by color.

Alternatives to Strops

• Sandpaper: Some crafters use very fine grit sandpaper (e.g. 2000+) taped to a flat surface, such as a ceramic tile, to polish the edge.
  • It is an economical and versatile solution, but does not offer the same experience and durability as a leather strop.

Benefits of Using Strop and Compound

1. Burr Removal: Removes microscopic residue left after sharpening with stones.
2. Extreme Polishing: Makes the edge mirror-like, improving cutting ability.
3. Easy Maintenance: Can be used regularly to maintain the sharp edge without having to repeat the entire sharpening process.
4. Professional finishing: It is the last step to obtain a perfect knife, both aesthetically and functionally.

How to Use Strop and Compound

1. Preparation:
   • If the strop is new, apply a small amount of compound to the surface. Spread evenly with your fingers or a cloth.
2. Positioning:
   • Keep the strop on a stable surface or use a strop with a non-slip base.
3. Polishing:
   • Rest the knife with the edge facing away from the strop.
   • Use light, even movements, pulling the blade backwards (never push, to avoid cutting the leather).
   • Run both sides of the thread 10-15 times or until you achieve the desired shine.

When to Use Strops and Compounds

• After completing sharpening with stones (e.g. 1000 grit or higher).
• To maintain an already sharpened edge without having to refine it with stones.
• To obtain a mirrored effect, essential for high-quality razors and knives.

Although they are “intruders” in the world of stones, strops and compounds are indispensable tools for those seeking a flawless finish. Whether you choose natural leather or alternatives like sandpaper, including them in your sharpening process will transform your edge from merely sharp to flawless. Try them to see the difference!

Sharpening Stone Grits: How to Choose the Right One

The grit of a sharpening stone is one of the most important factors to consider in order to obtain an effective sharpening that suits your needs. It indicates the level of abrasiveness of the stone and directly influences the type of work you can do: from roughing to repair a damaged edge to polishing to obtain a surgical cut.

In this guide, you’ll learn how to interpret different grits, which ones to choose based on the condition of your knife, and how to use them correctly to achieve flawless results. Whether you’re a beginner or an expert, understanding stone grits will help you turn sharpening into an art.

If you are confused by numbers, microns and mesh, don’t worry: here you will find a clear and practical guide to orient yourself in the world of sharpening stones!

Natural Stone Grit Summary

Natural stones, prized for their delicacy and precision, offer a range of grits ideal for different stages of sharpening. Here is a practical overview to choose the right grit based on the condition of the knife and the desired result:

Important Notes

1. Over 6,000:
   • Grits above 6,000 are dedicated to extreme polishing, such as for razors or sushi knives, and require great manual skill.
   • These levels are considered “paranoid” when applied to knives that are not of the highest quality, as the practical difference in everyday use may be minimal.
2. Steel quality:
   • Only high-quality steels can benefit from very fine grits (over 4,000). Softer steels cannot maintain an extremely sharp edge for long.
3. Regular maintenance:
   • For frequently used knives, maintaining an edge with medium grits (800-1,000) is more than sufficient. Reserve fine polishing for specific occasions.

Practical Advice

• Standard kitchen knives: Maintain a sharpening routine with grits of 800-1,000.
• Japanese or high precision knives: Complete sharpening with a 4,000-6,000 grit stone for a flawless edge.
• Damaged Knives: Always start with 240-400 grit to repair the edge, then progress to finer grits to refine it.

Natural stones offer a unique sharpening experience, but require attention and knowledge of the grits to get the most out of them. Follow the indicated progression to achieve the right balance between functionality and precision, remembering that the level of sharpness also depends on the quality of the knife steel.

Diamond Stone Grits: DMT Nomenclature

Diamond stones are known for their ability to sharpen quickly and with great precision. DMT, one of the most reputable brands, uses a standard classification that also applies to many other brands of diamond stones. Here is a guide to understanding grits, microns and their uses:

When and How to Use Each Grain

1. Extra-Coarse Diamond (60 micron / 220 grit):
   • When to use it:
     • For repairing knives with damaged edges, deep scratches or completely dulled edges.
     • Perfect for quick roughing on very hard steels.
   • Recommended time: 5-10 minutes to restore the shape of the thread.
2. Coarse Diamond (45 micron / 325 grit):
   • When to use it:
     • After roughing to start defining the thread.
     • Ideal for sharpening work or outdoor knives that require a strong edge.
   • Recommended time: 5 minutes for preliminary sharpening.
3. Fine Diamond (25 microns / 600 grit):
   • When to use it:
     • For sharpening kitchen, outdoor or hunting knives.
     • Ideal as a final step for functional knives, leaving a sharp, long-lasting edge.
   • Recommended time: 5-10 minutes to obtain a well-defined thread.
4. Extra-Fine Diamond (9 microns / 1,200 grit):
   • When to use it:
     • For a more refined finish, suitable for precision knives or carving tools.
     • Great for high quality kitchen knives or Japanese blades.
   • Recommended time: 3-5 minutes to perfect the thread.

Advantages of Diamond Stones

• Speed: Rapid abrasion on any type of steel, including high HRC steels.
• Durability: Diamond particles do not wear out easily and the stone maintains its effectiveness over time.
• Versatility: Suitable for roughing, sharpening and light polishing jobs.

Tips for Use

• Lubrication: DMT diamond stones work best dry or with a light spray of water.
• Pressure: Use light pressure to avoid damaging the wire or detaching diamond particles from the backing.
• Progression: Follow a grit progression (example: 220 → 325 → 600 → 1,200) for optimal results.

Diamond stones, like those from DMT, are essential tools for those who work with hard steels or want speed and precision in sharpening. Choose the right grit based on the condition of the edge and the desired result to obtain a perfectly sharp knife!

Compound in Syringe for Strop

In addition to classic compounds, there are syringe versions, particularly appreciated for their precision and ease of application. These compounds contain abrasive particles of size measured in microns and are ideal for advanced sharpening and extreme polishing.

When to Use Syringe Compounds

1. Copper (6 microns / 4,000 mesh):
   • Use it after a water or ceramic stone with a grit between 1000 and 3000.
   • Great for kitchen or outdoor knives that require a precise, functional edge.
2. Yellow (3 micron / 8,000 mesh):
   • Apply after using 4000-6000 grit stones.
   • Ideal for improving the edge and starting the advanced polishing process.
3. Gray (1 micron / 15,000 mesh):
   • Perfect for the final polishing of fine knives or razors.
   • Use on already perfectly sharpened wires to obtain a mirrored effect.

How to Apply Compounds in Syringe

1. Prepare the strop:
   • Make sure the leather or strop backing is clean and dry.
2. Apply the compound:
   • Squeeze a small amount of compound directly onto the surface of the leather.
   • Spread it evenly with your fingers or a soft cloth.
3. Polishing the thread:
   • Use light, even movements, always with the wire away from the leather, to avoid damaging the support.

Tips for an Optimal Result

• Progression: Gradually move from the more abrasive compounds (copper) to the finer ones (yellow and grey) to obtain maximum precision.
• Maintenance: Clean the strop between compounds to avoid contamination.
• Limited Use: Syringe compounds are highly concentrated, so you only need a small amount per session.

These compounds are ideal for those who want to take their sharpening work to the next level, achieving professional results on knives, razors and precision tools.

Ps. A special mention goes to the DiaSpray spray, which is equivalent to 0.5 microns, or about 30,000 grit, water and diamond particles, are we in science fiction!?

Classic Compounds for the Strop

Strop compounds are abrasive pastes that are applied to the leather to refine and polish the knife’s edge after sharpening. Each color indicates a different level of abrasiveness, ranging from roughing to fine polishing. Here’s an overview of the most common compounds and their uses:

How to Use Compounds on the Strop

1. Preparing the strop: Make sure the leather is clean and dry.
2. Applying the compound: Rub the chosen compound onto the strop until the surface is evenly covered.
3. Crush the knife:
   • Keep the knife with the edge away from the leather to avoid cutting the backing.
   • Use light, even strokes, following the entire length of the thread.

When to Use Each Compound

• Black Compound: After rough sharpening to remove cutting residue and burrs.
• White Compound: For finishing the edge after a medium grit or for general use.
• Green Compound: For polishing the edge after sharpening with fine grits (e.g. 3000-6000).
• Compound Red: For extreme polishing and mirror-like effect. Ideal for display razors or knives.

Use the compounds progressively, starting from the most abrasive ones (black or white) and moving on to the finer ones (green or red) to obtain the best result. In this way, the knife edge will be extremely sharp and shiny.