Using a whetstone is the best way to sharpen your knife: Stones allow for control and precision when sharpening, providing a razor-like edge with minimal steel removed.
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What is a Whetstone, Exactly?
Whetstones are abrasive stones made from natural rock or powdered media. Like sandpaper, whetstones vary in grit: Coarse stones reshape a blade by removing metal to repair chipped edges. Finer stones are for sharpening, polishing, and maintaining your edge.
Oil stones
Oil stones provide hard and long-wearing sharpening with very coarse and very fine grits. That makes them ideal for removing metal, repairing chips, and honing and polishing. India and Carborundum stones are formed by binding abrasive media together with a vitrified (glass-like) bonding agent. Arkansas stones are made by quarrying quartz and cutting it to shape, or by crushing the rock and binding it together.
These stones are semi-porous and must be coated with oil before sharpening. The oil protects the blade and stone from damage, while helping to capture the swarf (metal debris) produced by sharpening. A thin oil like mineral oil works best. Thick oils can interfere with the sharpening action of the stone.
There are three types of oil stones used in sharpening:
India Stone (Aluminum Oxide)
Available in Coarse, Medium, and fine, India Stones sharpen at a modest rate and produce a uniform, polished edge with little effort. The aluminum oxide used to create these stones gives them a deep orange, tan, or brown hue. India Stones can be single- or double-sided, with one side Coarse (150 grit) and the other Medium (240 grit) or Fine (400 grit). These stones are quite hard, with an average Mohs Hardness of 9 (pure diamond has a Mohs Hardness of 10).
Arkansas Stone (Novaculite)
Arkansas Stones are made of Novaculite, a sedimentary rock found exclusively in the Ouachita Mountains of Arkansas and Oklahoma. Novaculite is quartz composed of up to 99% crystalline silicon dioxide. It appears white, gray, solid black, or translucent black in color. Arkansas Stones are graded by hardness. The softer the stone, the coarser it is.
Of the types of three oil stones, Arkansas Stones provide the finest finish for obtaining the sharpest cutting edge. Soft stones have a grit-equivalent of 2000, while the hardest stones (Translucent Blacks) equate to 3500 to 4000 grit.
Silicon Carbide Stone (Carborundum)
The fastest cutting oil stones, Silicon Carbide Stones are also the hardest, with a Mohs hardness of 9 to 10. Like India Stones, these stones are Coarse (120 grit), Medium (180 grit), and Fine (320 grit). They’re man-made from powdered media and are matte gray in color.
Oil Stone Pros and Cons
- Economical: Oil stones are affordable and long-lasting. Combination stones cost as little as $30. Obtaining three grits costs well under $100.
- Consistent: Oil stones feature highly uniform sharpening surfaces and produce consistent, sharp edges.
- Wide grit range: Oil stones provide every grit needed for repair, sharpening, and finishing/polishing.
- Can Require Lapping: Soft stones can lose their flat surface. When this happens, they must be lapped with a flattening stone.
- Not the sharpest: Oil stones produce an extremely sharp edge, but other whetstones with even higher grits (10,000+) are required to obtain the sharpest edge possible with a mirror polish.
- Slow: At higher grits, oil stones sharpen the slowest and require the most passes to fix a dull blade.
Water Stones
Water stones are natural or man-made. They get their name from the act of soaking and lubricating the stones with water before sharpening. This technique was developed by Japanese bladesmiths centuries ago.
Natural Water Stones
Two popular natural water stones are Coticule, measuring 8000 grit, and Belgian Blue Stone, measuring 4000 grit. Both stones are quarried in Belgium and they’re great for honing a very fine edge. Natural Japanese water stones are mined in Kyoto. These stones are highly sought after and range in grits from 500 to over 10,000.
Synthetic Water Stones
Like India stones, synthetic water stones are man-made from powdered abrasives held together with bonding agents. Some are made with aluminum oxide, while others are made of ceramic. Instead of using a vitrified bonding agent, water stones use softer resins to hold their abrasives together.
Softer bonding agents produce faster-wearing but faster-cutting stones. Synthetic water stones can provide grits of up to 30,000. Such high grit counts are used to hone the sharpest cutting edge possible.
Water Stone Pros and Cons
- Efficient: Compared to oil stones, sharpening with water stones takes less time.
- Consistent: Like oil stones, water stones produce dependable, repeatable results.
- Wide grit range: Water stones provide the widest grit range of any whetstone, ranging from 80 to 30,000 grit.
- Easy to clean: Water stones are easier to rinse and clean than oil stones.
- Requires lapping: Water stones are the softest whetstones. They will require lapping after extensive use, especially if you’re frequently sharpening blades with high Rockwell Hardness ratings.
- Expensive: A single-grit water stone can cost $40 or more. A high-end Japanese 5-stone set from Naniwa costs nearly $300.
Diamond Stones
Diamond stones are man-made. They provide the hardest surface and sharpen quicker than any other whetstone. They’re formed by bonding mono- or poly-crystalline diamonds to a metal backing. Unlike oil stones and water stones, diamond stones require no maintenance: They’ll always remain perfectly flat and never require lapping.
Diamond stones typically range between 220 and 1200 grit, though some can hone an edge at 4000 and 8000 grit. For frequent sharpening of EDC knives, DMT-brand stones like the Duo-Sharp and Dia-Sharp have become the most popular whetstones among enthusiasts. Lubrication is entirely optional. These stones can be used dry, but wetting them can help prolong their lifespan. Lubrication should be provided by water or Krud Cutter.
Diamond Stone Pros and Cons
- Fastest: Diamond stones sharpen quicker than other whetstones.
- Best for hard blades: Diamond stones are the hardest; they’re best for blades with high C Ratings.
- Cost-effective: Their incredible lifespan and price make make diamond stones the best overall value.
- No maintenance: Diamond stones will never require lapping before sharpening.
- Best for regular use: Their hardness, reliability, convenience, and speed make diamond stones the best choice for frequent sharpening.
Whetstone Recap
We covered a lot of info, so here’s all the important stuff to remember about whetstones:
Oil Stones:
- Made from natural stone or bonded abrasives w/ vitrified agents
- Material: Novaculite, aluminum oxide, silicon carbide
- Lubricated with mineral oil
- Grit range: 120 to 4,000
- Typical Cost Per Stone: $25 to $55
Water Stones:
- Made from natural stone or bonded abrasives w/ resin agents
- Material: Ceramic, magnesium, aluminum oxide, silicon carbide
- Lubricated with water
- Grit range: 80 to 30,000
- Typical Cost Per Stone: “Budget” $20 to $30; “Super” $40 to $100, “Pro” $65 to $240
Diamond Stones:
- Made from bonded abrasive with metal backing
- Material: Mono- or poly-crystalline diamond powder
- Lubricated with water or Krud Cutter (optional)
- Grit Range: 220 to 8,000
- Typical Cost Per Stone: $50 to $190
Stones are no good if you don’t know how to freehand sharpen! Read our guide.
