Sharpening stone

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An oil stone Sharpeningstone1.jpg
An oil stone

Sharpening stones, or whetstones, are used to sharpen the edges of steel tools such as knives through grinding and honing.

Contents

Such stones come in a wide range of shapes, sizes, and material compositions. They may be flat, for working flat edges, or shaped for more complex edges, such as those associated with some wood carving or woodturning tools. They may be composed of natural quarried material or from man-made material. They come in various grades, which refer to the grit size of the abrasive particles in the stone. (Grit size is given as a number, which indicates the spatial density of the particles; a higher number denotes a higher density and therefore smaller particles, which give a finer finish to the surface of the sharpened object.) Stones intended for use on a workbench are called bench stones, while small, portable ones, whose size makes it hard to draw large blades uniformly over them, especially "in the field", are called pocket stones.

Often whetstones are used with a cutting fluid to enhance sharpening and carry away swarf. Those used with water for this purpose are often called water stones or waterstones, those used with oil sometimes oil stones or oilstones.

Whetstones will wear away with use, typically in the middle. Tools sharpened in this groove will develop undesirable curves on the blade. In order to prevent this, a whetstone may be levelled out with sandpaper or a levelling or flattening stone. [1]

Terminology

Though "whetstone" is often mistaken[ by whom? ] as a reference to the water sometimes used to lubricate such stones, the term is based on the word "whet", which means to sharpen a blade, [2] [3] not on the word "wet". The verb nowadays to describe the process of using a sharpening stone for a knife is simply to sharpen, but the older term to whet is still sometimes used, though so rare in this sense that it is no longer mentioned in, for example, the Oxford Living Dictionaries. [4] [5]

Natural stones

Natural whetstones are typically formed of quartz, such as novaculite. The Ouachita Mountains in Arkansas are noted as a source for these. Novaculite and other stone formations are found around the world such as in Eastern Crete which produces a stone known as the Turkish Stone, mined in the Elounda mountain but sold all throughout the Levant (hence its name) since antiquity. [6]

Similar stones have been in use since antiquity. The Roman historian Pliny described use of several naturally occurring stones for sharpening in his Natural History. He describes the use of both oil and water stones and gives the locations of several ancient sources for these stones. [7]

One of the most well-regarded natural whetstones is the yellow-gray "Belgian Coticule", which has been legendary for the edge it can give to blades since Roman times, and has been quarried for centuries from the Ardennes. The slightly coarser and more plentiful "Belgian Blue" whetstone is found naturally with the yellow coticule in adjacent strata; hence two-sided whetstones are available, with a naturally occurring seam between the yellow and blue layers. These are highly prized for their natural elegance and beauty, and for providing both a fast-cutting surface for establishing a bevel and a finer surface for refining it. Different veins of this stone are suitable for knives, tools, and razors respectively. Certain versions (such as La Veinette) are very sought after for razor honing. [8]

The hard stone of Charnwood Forest in northwest Leicestershire, England, has been quarried for centuries, [9] and was a source of whetstones and quern-stones.

Natural stones are often prized for their natural beauty as stones and their rarity, adding value as collectors' items. Furthermore, each natural stone is different, and there are rare natural stones that contain abrasive particles with different properties than are currently available in artificial stones. [10] Two common stones in the UK are the Water of Ayr stone and the speckled Tam'o Shanter stone, both forms of slate used as razor oilstones. [6]

Artificial (synthetic) stones

Artificial stones usually come in the form of a bonded abrasive composed of a ceramic such as silicon carbide (carborundum) or aluminium oxide (corundum). Bonded abrasives provide a faster cutting action than natural stones. They are commonly available as a double-sided block with a coarse grit on one side and a fine grit on the other enabling one stone to satisfy the basic requirements of sharpening. Some shapes are designed for specific purposes such as sharpening scythes, drills or serrations. [11]

Modern synthetic stones are generally of equal quality to natural stones, and are often considered superior in sharpening performance because of consistency of particle size and control over the properties of the stones. For example, the proportional content of abrasive particles as opposed to base or "binder" materials can be controlled to make the stone cut faster or more slowly, as desired. [12]

The use of natural stone for sharpening has diminished with the widespread availability of high-quality artificial stones with consistent particle size. As a result, the legendary Honyama mines in Kyoto, Japan, have been closed since 1967. Belgium currently has only a single mine that is still quarrying Coticules and their Belgian Blue Whetstone counterparts. [13]

Japanese natural and synthetic waterstones

Two Japanese waterstones Waterstones.jpg
Two Japanese waterstones

The Japanese traditionally use natural sharpening stones (referred to as tennen toishi [14] ) wetted with water, as using oil on such a stone reduces its effectiveness. The geology of Japan provided a type of stone which consists of fine silicate particles in a clay matrix, somewhat softer than novaculite. [15] Besides this clay mineral, some sedimentary rock was used by the Japanese for whetstones, the most famous being typically mined in the Narutaki District just north of Kyoto along the Hon-kuchi Naori stratum. [16] There were many individual mines which produced stone from one of the three stratums in the region, many sought after for specific reputations such as Ohira Uchigumori, Hakka Tomae, and Nakayama stones. [17]

Historically, there are three broad grades of Japanese toishi (sharpening stones): the ara-to, or "rough stone", the naka-to or "middle/medium stone" and the shiage-to or "finishing stone". There is a fourth type of stone, the nagura, which is not used directly. Rather, it is used to form a cutting slurry on the shiage-to (early finishing stone) or awasedo (late finishing stone), which are often too hard to create the necessary slurry. Converting these names to absolute grit size is difficult as the classes are broad and natural stones have no inherent "grit number". As an indication, ara-to is probably (using a non-Japanese system of grading grit size) 500–1000 grit. The naka-to is probably 3000–5000 grit and the shiage-to is likely 7000–10000 grit. Current synthetic grit values range from extremely coarse, such as 120 grit, through extremely fine, such as 30,000 grit (less than half a micrometer abrasive particle size).[ citation needed ]

Diamond plate

A diamond plate Diamondstone.jpg
A diamond plate

A diamond plate is a steel plate, sometimes mounted on a plastic or resin base, coated with diamond grit, an abrasive that will grind metal. When they are mounted they are sometimes known as diamond stones. [18] The plate may have a series of holes cut in it that capture the swarf cast off as grinding takes place, and cuts costs by reducing the amount of abrasive surface area on each plate. Diamond plates can serve many purposes including sharpening steel tools, and for maintaining the flatness of man-made waterstones, which can become grooved or hollowed in use. Truing (flattening a stone whose shape has been changed as it wears away) is widely considered essential to the sharpening process but some hand sharpening techniques utilise the high points of a non-true stone. As the only part of a diamond plate to wear away is a very thin coating of grit and adhesive, and in a good diamond plate this wear is minimal due to diamond's hardness, a diamond plate retains its flatness. Rubbing the diamond plate on a whetstone to true (flatten) the whetstone is a modern alternative to more traditional truing methods. [19]

Diamond plates are available in various plate sizes (from credit card to bench plate size) and grades of grit. A coarser grit is used to remove larger amounts of metal more rapidly, such as when forming an edge or restoring a damaged edge. A finer grit is used to remove the scratches of larger grits and to refine an edge. There are two-sided plates with each side coated with a different grit. [20]

The highest quality diamond sharpeners use monocrystalline diamonds, single structures which will not break, giving them an excellent lifespan. These diamonds are bonded onto a precision ground surface, set in nickel, and electroplated. This process locks the diamonds in place. [20]

Hobby microscope view of a 220 grit diamond sharpening stone. Tiny diamonds are electroplated to a perforated metal carrier strip and bonded to a plastic backing. The feature identified with the red line across it measures about 0.08 mm across. The dark area at upper left is a void designed to allow for swarf created during sharpening to be cleared from the diamonds. This relatively coarse stone would be used to reshape a damaged blade edge which would be refined by finer grit stones. DMT Black 220 Label.jpg
Hobby microscope view of a 220 grit diamond sharpening stone. Tiny diamonds are electroplated to a perforated metal carrier strip and bonded to a plastic backing. The feature identified with the red line across it measures about 0.08 mm across. The dark area at upper left is a void designed to allow for swarf created during sharpening to be cleared from the diamonds. This relatively coarse stone would be used to reshape a damaged blade edge which would be refined by finer grit stones.

Grit size

There is no dominant standard for the relationship between "grit size" and particle diameter. Part of the difficulty is that "grit size" is used to refer to the smoothness of the finish produced by a sharpening stone, and not just the actual size of the grit particles. Other factors apart from particle diameter that affect the finish (and thus the "grit size" rating) are:

In synthetic stones, the grit size is related to the mesh size used to select the particles to be included in the abrasive. Sandpaper also uses a similar system.

Comparison of grit size standards Comparison of grit size standards.svg
Comparison of grit size standards

Here are some typical sharpening stone grit sizes and their uses when sharpening steel knives:

Grit sizeApproximate particle diameterTypical use [25] [26]
20080 μmRemoving chips from a damaged blade
50030 μmRoughly sharpening a blunt edge
10008 μmSmoothing a rough edge into a medium edge
4,0004 μmSmoothing a medium edge into a sharp edge for cutting meat
8,0002 μmFurther smoothing a sharp edge for cutting fish or vegetables (sinews in meat will bend an edge this sharp)
30,0000.5 μmPolishing an edge to a mirror-smooth (but possibly fragile) finish.

Standards for grit size measurements include JIS, CAMI, ANSI, FEPA-P (for sandpaper), FEPA-F (for metal abrasives), and various trademarked standards for individual company product ranges.

See also

Related Research Articles

<span class="mw-page-title-main">Lapidary</span> Shaping of gemstones for jewelry

Lapidary is the practice of shaping stone, minerals, or gemstones into decorative items such as cabochons, engraved gems, and faceted designs. A person who practices lapidary is known as a lapidarist. A lapidarist uses the lapidary techniques of cutting, grinding, and polishing. Hardstone carving requires specialized carving techniques.

A saw is a tool consisting of a tough blade, wire, or chain with a hard toothed edge used to cut through material. Various terms are used to describe toothed and abrasive saws.

<span class="mw-page-title-main">Blade</span> Sharp cutting part of a weapon or tool

A blade is the portion of a tool, weapon, or machine with an edge that is designed to puncture, chop, slice or scrape surfaces or materials. Blades are typically made from materials that are harder than those they are to be used on. Historically, humans have made blades from flaking stones such as flint or obsidian, and from various metal such as copper, bronze, and iron. Modern blades are often made of steel or ceramic. Blades are one of humanity's oldest tools, and continue to be used for combat, food preparation, and other purposes.

An abrasive is a material, often a mineral, that is used to shape or finish a workpiece through rubbing which leads to part of the workpiece being worn away by friction. While finishing a material often means polishing it to gain a smooth, reflective surface, the process can also involve roughening as in satin, matte or beaded finishes. In short, the ceramics which are used to cut, grind and polish other softer materials are known as abrasives.

<span class="mw-page-title-main">Sandpaper</span> Abrasive material used for smoothing softer materials

Sandpaper, also known as glasspaper or as coated abrasive, is a type of material that consists of sheets of paper or cloth with an abrasive substance glued to one face. In the modern manufacture of these products, sand and glass have been replaced by other abrasives such as aluminium oxide or silicon carbide. It is common to use the name of the abrasive when describing the paper, e.g. "aluminium oxide paper", or "silicon carbide paper".

<span class="mw-page-title-main">Razor strop</span> Device for straightening and polishing blades

A razor strop or simply a strop is a flexible strip of leather, canvas, denim fabric, balsa wood, or other soft material, used to straighten and polish the blade of a straight razor, a knife, or a woodworking tool such as a chisel. In many cases stropping re-aligns parts of the blade edge that have been bent out of alignment. In other cases, especially when abrasive polishing compound is used, stropping may remove a small amount of metal. Stropping can also burnish the blade.

<span class="mw-page-title-main">Grinding wheel</span> Abrasive cutting tool for grinders

Grinding wheels are wheels that contain abrasive compounds for grinding and abrasive machining operations. Such wheels are also used in grinding machines.

A grinding dresser or wheel dresser is a tool to dress the surface of a grinding wheel. Grinding dressers are used to return a wheel to its original round shape, to expose fresh grains for renewed cutting action, or to make a different profile on the wheel's edge. Utilizing pre-determined dressing parameters will allow the wheel to be conditioned for optimum grinding performance while truing and restoring the form simultaneously.

<span class="mw-page-title-main">Straight razor</span> Knife used to remove body hair

A straight razor is a razor with a blade that can fold into its handle. They are also called open razors and cut-throat razors. The predecessors of the modern straight razors include bronze razors, with cutting edges and fixed handles, produced by craftsmen from Ancient Egypt during the New Kingdom. Solid gold and copper razors were also found in Ancient Egyptian tombs dating back to the 4th millennium BC.

<span class="mw-page-title-main">Novaculite</span> Type of rock

Novaculite, also called Arkansas Stone, is a microcrystalline to cryptocrystalline rock type that consists of silica in the form of chert or flint. It is commonly white to grey or black in color, with a specific gravity that ranges from 2.2 to 2.5. It is used in the production of sharpening stones. It occurs in parts of Arkansas, Oklahoma, and Texas, as well as in Japan and parts of the Middle East. The name novaculite is derived from the Latin word novacula, meaning a sharp knife, dagger, or razor, in reference to its use in sharpening. The first recorded use of the term whetstone was in reference to a honing stone from Arkansas.

<span class="mw-page-title-main">Sharpening jig</span> Tool used to sharpen woodworking tools

A sharpening jig is often used when sharpening woodworking tools. Many of the tools used in woodworking have steel blades which are sharpened to a fine edge. A cutting edge is created on the blade at the point at which two surfaces of the blade meet. To create this cutting edge a bevel is formed on the blade, usually by grinding. This bevel is subsequently refined by honing until a satisfactorily sharp edge is created.

<span class="mw-page-title-main">Marking knife</span> Woodworking layout tool

A marking knife or striking knife is a woodworking layout tool used for accurately marking workpieces. It is used to cut a visible line, which can then be used to guide a hand saw, chisel or plane when making woodworking joints and other operations. They are generally used when marking across the grain of the wood, with scratch awls better suited for marking with the grain.

<span class="mw-page-title-main">Sharpening</span> Creating or refining the edge of a cutting tool

Sharpening is the process of creating or refining the edge joining two non-coplanar faces into a converging apex, thereby creating an edge of appropriate shape on a tool or implement designed for cutting. Sharpening is done by removing material on an implement with an abrasive substance harder than the material of the implement, followed sometimes by processes to polish/hone the sharp surface to increase smoothness.

<span class="mw-page-title-main">Knife making</span> Process of manufacturing a knife

Knife making is the process of manufacturing a knife by any one or a combination of processes: stock removal, forging to shape, welded lamination or investment cast. Typical metals used come from the carbon steel, tool, or stainless steel families. Primitive knives have been made from bronze, copper, brass, iron, obsidian, and flint.

<span class="mw-page-title-main">Knife sharpening</span>

Knife sharpening is the process of making a knife or similar tool sharp by grinding against a hard, rough surface, typically a stone, or a flexible surface with hard particles, such as sandpaper. Additionally, a leather razor strop, or strop, is often used to straighten and polish an edge.

<span class="mw-page-title-main">Diamond tool</span>

A diamond tool is a cutting tool with diamond grains fixed on the functional parts of the tool via a bonding material or another method. As diamond is a superhard material, diamond tools have many advantages as compared with tools made with common abrasives such as corundum and silicon carbide.

<span class="mw-page-title-main">Diamond blade</span> Saw blade with diamond grit bonded to the cutting surface

A diamond blade is a saw blade which has diamonds fixed on its edge for cutting hard or abrasive materials. There are many types of diamond blade, and they have many uses, including cutting stone, concrete, asphalt, bricks, coal balls, glass, and ceramics in the construction industry; cutting semiconductor materials in the semiconductor industry; and cutting gemstones, including diamonds, in the gem industry.

<span class="mw-page-title-main">Honing steel</span> Rod of steel used to restore keenness to dulled blades

A honing steel, sometimes referred to as a sharpening steel, whet steel, sharpening stick, sharpening rod, butcher's steel, and chef's steel, is a rod of steel, ceramic or diamond-coated steel used to restore keenness to dulled blade edges. They are flat, oval, or round in cross-section and up to 30 centimetres (1 ft) long. The steel and ceramic honing steels may have longitudinal ridges, whereas the diamond-coated steels are smooth but embedded with abrasive diamond particles.

Abrasive machining is a machining process where material is removed from a workpiece using a multitude of small abrasive particles. Common examples include grinding, honing, and polishing. Abrasive processes are usually expensive, but capable of tighter tolerances and better surface finish than other machining processes

<span class="mw-page-title-main">Japanese sword polishing</span>

Sword polishing is part of Japanese swordsmithing where a blade is polished after forging. It gives the shining appearance and beauty to the sword.

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