Sharpening Stones - A Complete Guide

Sharpening stones, also known as whetstones, are a simple, longstanding tool used to sharpen blades by grinding them against an abrasive surface. This process is known as ‘honing’.

They are made from a variety of natural and artificial materials with different levels of abrasion. Some sharpening stones, made from artificial abrasive, feature two sides - a coarser side for heavier work and a finer side for finishing.

Blade sharpening stones form part of a larger category of manual sanding and sharpening tools, which also includes abrasive blocks and hand pads.

What are They Used to Sharpen?

Sharpening stones are principally used with bladed steel tools. Examples include:

• Kitchen knives
• Scissors
• Reusable razors
• Chisels
• Plane blades

As we saw above, whetstones are made from a number of different materials, each of which produces differing finishes on the surface to which they are applied.

Here are some of the most common categories:

Water Stones

The broad term ‘water stone’ refers to sharpening stones that work best with water as a lubricant for the sharpening process. Both artificial and natural stones fall into this category.

Japanese Sharpening Stones

Japanese sharpening stones are regarded as the highest quality natural stones available. They are made in the eponymous country from exceptionally fine silica-rich stone and have hundreds of years of craftsmanship behind them. As it is conventional to immerse them in water for up to an hour before use, they are often referred to as ‘Japanese water stones’.

Arkansas Stones

Arkansas stones are a variety of natural sharpening stone, made from novaculite, a variety of quartz with a high silicon dioxide content. These stones are typically mined in the Ouachita Mountains in the US state of Arkansas, hence their name.

Dry Sharpening Stones

Honing generates heat through abrasion, so it is common to lubricate sharpening stones prior to application. Lubrication accelerates the honing process and removes the fine debris produced by sharpening, known as ‘swarf’, preventing later scratches. However, lubrication is not essential and most sharpening stones can be used either wet or dry. Some types of sharpening stone - for example, ceramic and those made from industrial diamond - are typically used with no lubrication.

Sharpening stones are graded according to the size of their grit - the rough particles embedded within the stone.

There are five grades:

• Coarse
• Coarse/Fine
• Medium
• Fine
• Super Fine

As you might expect, coarser stones are used for heavier work, such as reshaping damaged or nicked blades, while medium stones are better for pure sharpening work. Finer stones, meanwhile, are used to polish the blade after the more vigorous stages of the sharpening process have been completed.

As indicated above, some sharpening stones made from synthetic materials are provided with both a coarse and a finer side for maximum utility. The former can be used for dull, badly worn blades, before turning the stone for the polishing and finishing stages.

The grit size of different stones is indicated by a range of printed numbers, which are intended to indicate how smooth a finish they will produce; the lower the number, the coarser the finish. It’s worth noting that as a general rule, coarser stones are typically more brittle than finer ones.

However, you should also be aware that these numbers are only approximations and they do not have a clear relationship to the actual size of the embedded particles. The smoothness of the finish will depend on additional factors other than the size of the particles, including their shape, how exposed they are, their resistance to pressure, and their overall strength.

Some of the most common sizes are compared in the following chart, from the coarsest to the highest grit numbers:

Sharpening stones come in four basic shapes:

• Rectangular
• Round
• Square
• Triangular

Rectangular is the most common and is ideal for working broad, flat edges. Square stones are a good choice for fine finishes and small implements like keys. Triangular stones are best for fine work with small recesses, while round sharpening stones provide a curved surface for sharpening rounded tools like gouges and smoothing other fine blades with a curved shape.

Oil Stone vs Water Stone

These two conventional terms suggest that certain stones are best used with oil as a lubricating medium while others perform better with water. However, this is not the case as all sharpening stones can be used with either lubricant - or none. Of course, the use of water or oil can be beneficial, and lubrication helps to prolong the life of very fine, expensive varieties like Japanese water stones.

Natural Sharpening Stones vs Synthetic

Natural vs synthetic whetstones is perhaps the biggest binary when it comes to blade sharpening.

The natural sharpening properties of hard minerals like quartz have been known and appreciated for many years, but nowadays, the available options have been considerably expanded by the addition of artificial bonded abrasives like carborundum (silicon carbide) or corundum (aluminium oxide). These can cut more quickly than the natural alternatives but do not typically include very fine grits.

India Stone vs Arkansas Stone

India Stone is a widely used medium honing stone made from aluminium oxide. The term is actually a brand name owned by the Norton Adhesive Company. These whetstones have a distinctive orange and tan colouring.

Arkansas stone, by contrast, is a natural sharpening stone made from a variety of quartz, as explained above.

Ceramic Sharpening Stones vs Water Stones

As the name suggests, ceramic sharpening stones are an artificial variety made from a fused block of ceramic material like silicon carbide (ceramics are hard materials made via heating, which contain no metallic or organic material). Ceramic sharpening stones are very hard-wearing and are normally used dry with no lubrication. They are typically available with medium and fine grit sizes.

By contrast, water stones can be both artificial and natural in origin. As discussed above, water can be used for lubrication when sharpening with these stones and it will make the process easier, but it is not essential in most cases.