Sharpening stones,
water stones or
whetstones are used to
grindThe grind of a blade refers to the shape of the cross-section of the blade. It is distinct from the type of blade , though different tools and blades may have lent their name to a particular grind.Grinding involves removing significant portions of metal from the blade and is thus distinct from...
and
honeA hone is a machine tool used in the manufacture of precision bores to improve the geometry, surface finish and dimensional control of the finished part. This process is called honing....
the edges of steel tools and implements. Examples of items that may be
sharpenedSharpening is the process of creating or refining a sharp edge of appropriate shape on a tool or implement designed for cutting. Sharpening is done by grinding away material on the implement with an abrasive substance harder than the material of the implement, followed sometimes by processes to...
with a sharpening stone include scissors,
knivesA knife is any cutting edge or blade, handheld or otherwise, with or without a handle. Knives were used at least two-and-a-half million years ago, as evidenced by the Oldowan tools. Originally made of rock, flint, and obsidian; knives have evolved in construction as technology has with blades...
,
razorsA straight razor is a razor with a blade that can fold into its handle. They are also called open razors and cut-throat razors.Although straight razors were once the principal method of manual shaving, they have been largely overshadowed by the safety razor, incorporating a disposable blade...
and tools such as
chiselA chisel is a tool with a characteristically shaped cutting edge of blade on its end, for carving or cutting a hard material such as wood, stone, or metal...
s and
planeA plane is a tool for shaping wood. Planes are used to flatten, reduce the thickness of, and impart a smooth surface to a rough piece of lumber or timber. Planing is used to produce horizontal, vertical, or inclined flat surfaces on workpieces usually too large for shaping...
blades. Though it is sometimes mistaken as a reference to the water often used to lubricate such stones, the word "whetstone" is a compound word formed with the word "whet," which means to sharpen a blade, not the word "wet."
Sharpening stones come in a wide range of shapes, sizes and material compositions. Stones may be flat, for working flat edges, or shaped for more complex edges, such as those associated with some
wood carvingWood carving is a form of working wood by means of a cutting tool held in the hand , resulting in a wooden figure or figurine or in the sculptural ornamentation of a wooden object...
or
woodturningWoodturning is a form of woodworking that is used to create wooden objects on a lathe. Woodturning differs from most other forms of woodworking in that the wood is moving while a stationary tool is used to cut and shape it. Many intricate shapes and designs can be made by turning wood.There are two...
tools. They may be composed of natural quarried material, or from man-made material.
Stones are usually available in various grades, which refers to the
gritMesh material is often used in determining the particle size distribution of a granular material. For example, a sample from a truckload of peanuts may be placed atop a mesh with 5 mm openings. When the mesh is shaken, small broken pieces and dust pass through the mesh while whole peanuts are...
size of the particles in the stone. Generally, the finer the grit, the denser the material, which leads to a finer finish of the surface of the tool. Finer grits cut slower because they remove less material. Grits are often given as a number, which indicates the density of the particles with a higher number denoting higher density and therefore smaller particles.
Natural versus artificial stones
Although there is a certain amount of romance associated with using stone which is found naturally, there are also some drawbacks. First, over hundreds of years, the best quarries have given up much of their best stone. This scarcity causes high prices for a good quality consistent stone. Lesser quality stones have problems of consistency and may have occasional larger pieces of grit or soft spots. With this in mind, and with modern technologies, artificial stones came to the market. There have been a variety of formulations over the years and the quality of artificial stones continues to improve, so much so that many carpenters have converted to synthetic stones altogether. Sword polishing is still most commonly performed with extremely costly and rare natural polishing stones, as the visual results of polising on a synthetic stone tend to produce a mirror-like surface, rather than the grain revealing polish of the natural stones.
One of the most revered natural whetstones is the yellow-gray Belgian coticule, which has been quarried for centuries from the
ArdennesThe Ardennes is a region of extensive forests, rolling hills and old mountains formed on the Givetian Ardennes mountains, primarily in Belgium and Luxembourg, but stretching into France , and geologically into the Eifel...
. 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, as well as for providing both a fast-cutting surface for establishing a bevel and a higher-grit surface for refining it.
The hard stone of
Charnwood ForestCharnwood Forest is an upland tract in north-western Leicestershire, England, bounded by Leicester, Loughborough, and Coalville. It is undulating, rocky, picturesque, with barren areas, and some extensive tracts of woodland; its elevation is generally 600 ft and upwards, the area exceeding this...
has been quarried for centuries, and was a source of whetstones and
Quern-stoneQuern-stones are a pair of stone tools for hand grinding a wide variety of materials. The lower, stationary, stone is called a quern, whilst the upper, mobile, stone is called a handstone...
s.
For most users artificial stones offer many improvements over the natural stones of the past. The high cost and difficulty of obtaining quality natural stones make them impractical for most.
Whetstones and oilstones
Whetstones may be natural or artificial stones. Artificial stones usually come in the form of a
bonded abrasiveAn 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...
composed of a
ceramicA ceramic is an inorganic, non-metallic solid prepared by the action of heat and subsequent cooling. Ceramic materials may have a crystalline or partly crystalline structure, or may be amorphous...
such as
silicon carbideSilicon carbide , also known as carborundum, is a compound of silicon and carbon with a chemical formula SiC. It occurs in nature as the extremely rare mineral moissanite. Silicon carbide powder has been mass-produced since 1893 for use as an abrasive...
(carborundum) or of
aluminium oxideAluminium oxide is an amphoteric oxide of aluminium with the chemical formula
23. It is also commonly referred to as alumina, corundum, sapphire, ruby or aloxite in the mining, ceramic and materials science communities. It is produced by the Bayer process from bauxite...
(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.
When the block is intended for installation on a bench it is called a bench stone. Small, portable stones (commonly made of bonded abrasive) are called pocket stones. Being smaller they are more portable than bench stones but difficulty in maintaining a consistent angle and pressure when drawing the stone along larger blades can make them harder to use. However, they are still very capable of forming a good edge. Frequently, fine grained pocket stones are used for honing, especially "in the field". Despite being a
homophoneA homophone is a word that is pronounced the same as another word but differs in meaning. The words may be spelled the same, such as rose and rose , or differently, such as carat, caret, and carrot, or to, two and too. Homophones that are spelled the same are also both homographs and homonyms...
with
wet, whetstones need not be lubricated with oil or water though it is very common that one of these is used. Lubrication aids the cutting action and carries away
swarfSwarf, also known as turnings, chips, or filings, are shavings and chippings of metal — the debris or waste resulting from metalworking operations. It can usually be recycled, and this is the preferred method of disposal due to the environmental concerns regarding potential contamination with...
.
Finer grades of whetstones intended for use with oil (though, again, water can also be used) are called oilstones. Oilstones usually come in the form of bench stones. One of the natural minerals commonly used in oilstones is
NovaculiteNovaculite is a form of chert or flint found in the Ouachita Mountains of Arkansas and Oklahoma and in the Marathon Uplift of Texas. Novaculite is considered to be highly siliceous sediments and may be a product of the low-grade metamorphism of chert beds...
. Examples of stones made from this material include
Arkansas, Ouachita or
Washita stones from the
Ouachita MountainsThe Ouachita Mountains are a mountain range located in west central Arkansas, southeastern Oklahoma and north-east Texas. The range's subterranean roots may extend as far as central Texas, or beyond it to the current location of the Marathon Uplift...
in
ArkansasArkansas is a state located in the southern region of the United States. Its name is an Algonquin name of the Quapaw Indians. Arkansas shares a border with six states, with its eastern border largely defined by the Mississippi River. Its diverse geography ranges from the mountainous regions of the...
. These come in various grades and colors, with the finer stones being denominated "surgical black" or "pink translucent". Novaculite is from the Devonian and Mississippian periods. It is a sedimentary rock composed mostly of microcrystalline
quartzQuartz is the second most abundant mineral in the Earth's continental crust . It is made up of a continuous framework of SiO
4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO
2.There are many different varieties of...
and is basically a recrystallized variety of
chertChert is a fine-grained silica-rich microcrystalline, cryptocrystalline or microfibrous sedimentary rock that may contain small fossils. It varies greatly in color , but most often manifests as gray, brown, grayish brown and light green to rusty red; its color is an expression of trace elements...
. It is also the primary material in
Charnley Forest and
Turkey oilstones.
Extremely fine grades of stone that remove very little metal may be called polishing stones.
Japanese waterstones
The Japanese have traditionally used sharpening stones which are lubricated with water to sharpen their metal tools (using oil on a waterstone is deleterious to the stone). As they have been doing this for many hundreds of years, it is obvious that the first stones were those which were found occurring naturally. The geology of Japan provided a type of stone which consists of fine silicate particles in a clay matrix. This is somewhat softer than
NovaculiteNovaculite is a form of chert or flint found in the Ouachita Mountains of Arkansas and Oklahoma and in the Marathon Uplift of Texas. Novaculite is considered to be highly siliceous sediments and may be a product of the low-grade metamorphism of chert beds...
.
Japanese stones are also sedimentary. The most famous are typically mined in the Narutaki District just north of
Kyotois a city in the central part of the island of Honshū, Japan. It has a population close to 1.5 million. Formerly the imperial capital of Japan, it is now the capital of Kyoto Prefecture, as well as a major part of the Osaka-Kobe-Kyoto metropolitan area....
.
Advantages and disadvantages
These softer Japanese stones have a few advantages over harder stones. First, because they are softer they do not become glazed or loaded with the material they are sharpening. New particles are constantly exposed as you work with them and thus they continue to cut consistently. Second, they can be lubricated effectively with water (rather than oil, which can ruin the stone) so nothing but water is required. Finally, because they are soft, the worn material and the water form a slurry which in conjunction with the stone, sharpens and polishes the blade.
The disadvantage is that they wear out faster than other types of sharpening stone, although this makes them easier to flatten.
Grades of waterstones
Historically, there are three broad grades of Japanese 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, which is 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 micron abrasive particle size).
Diamond plate
A diamond plate is a steel plate sometimes with a plastic or resin base. The plate is coated with diamond
gritMesh material is often used in determining the particle size distribution of a granular material. For example, a sample from a truckload of peanuts may be placed atop a mesh with 5 mm openings. When the mesh is shaken, small broken pieces and dust pass through the mesh while whole peanuts are...
, an abrasive that will grind material. The plate may have a series of holes cut in it which are designed to capture the
swarfSwarf, also known as turnings, chips, or filings, are shavings and chippings of metal — the debris or waste resulting from metalworking operations. It can usually be recycled, and this is the preferred method of disposal due to the environmental concerns regarding potential contamination with...
that is cast off as grinding takes place. Diamond plates can serve two purposes. First they are used as a stand-alone alternative to stones for sharpening steel edge tools, but plates can also be used for maintaining the flatness of man-made waterstones, which can become grooved or hollowed in use. Flattening deformed waterstones is considered essential to the sharpening process. Diamond plates can be used to flatten these stones and are considered an alternative to more traditional methods.
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 an edge which is damaged. A finer grit is used to remove the scratches of larger grits and to refine an edge. Two-sided plates exist where each side is covered by a different grit.
Unlike stones which can become rounded—decreasing their effectiveness—diamond plates remain flat. They do not require the use of a lubricant.
Diamond plates, being made from diamond—even though of industrial grade—tend to be more expensive than stones.
Sharpening stones in legend
The giant
HrungnirHrungnir was a jötunn in Norse mythology, slain by the god Thor with his hammer Mjölnir. The account is documented in the Skáldskaparmál, in the Prose Edda by Snorri Sturluson....
used a whetstone as a weapon in his combat with the god
ThorThor is the red-haired and bearded god of thunder in Germanic mythology and Germanic paganism, and its subsets: Norse paganism, Anglo-Saxon paganism and Continental Germanic paganism....
.
See also
- Sharpening
Sharpening is the process of creating or refining a sharp edge of appropriate shape on a tool or implement designed for cutting. Sharpening is done by grinding away material on the implement with an abrasive substance harder than the material of the implement, followed sometimes by processes to...
- Knife sharpening
Knives are sharpened by grinding against a hard rough surface, typically stone, or a soft surface with hard particles, such as sandpaper. For finer sharpening, a leather razor strop, or strop, is often used. The smaller the angle between the blade and stone, the sharper the knife will be, but the...
- Razor strop
A razor strap is a flexible strip of leather or canvas used to sharpen a thin blade such as a straight razor.Unlike honing a blade, in which a whetstone removes metal bent out of alignment from the blade's edge, stropping the blade re-aligns the indentations without removing any material.The strop...
- Sharpening jig
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...
- Scary sharp
Scary sharp is a method of sharpening woodworking tools with sandpaper instead of conventional methods of oilstone or waterstone sharpening. The sandpaper is glued to plate glass or another hard, flat substrate to create the sharpening surface....
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