The grinding stones are represented by a sandstone rock, they have a sharp grain that allows turning of metal cutting tools. In order for a stone to have efficiency, its grains should not be reliably connected, this is due to the fact that the located sharp corners on top are erased and become smooth, while they are separated and the sharp corners of the grains protrude on the upper layer.
Varieties of grinding stones and bars.
For this reason, in practice, for various purposes, stones of various characteristics and origin are used.
Arkansas stone is based on traditional crystalline silica, in other words, quartz. However, the structure of this material is special. Among the first characteristics, it is possible to single out the fact that this rock acts as the most pure of all quartz. So, SiO2 it contains 99.5%. If you make a comparison with rock crystal, then even in it there are much more extraneous inclusions. The second feature of Arkansas is expressed in the fact that it possesses a homogeneous rock with crystalline quartz: it has the smallest graininess, so, the grain size is equal to the limit of 1-6 microns. The last thing you should pay attention to is the strength of the bonds between the factions, which is very strong. This is due to the implication structure, which is expressed by the fact that the jagged borders of the fractions are as if intertwined with each other. This material is very rare, the only place in the world where its deposit is found, the Arkansas River Basin, which flows in America. It was she who gave the name to the stone.
Figure 1. Arkansas, Vashita, and India Grit Tables.
In ancient times, the rock lay in areas of massive strata, but eventually people began to produce intensive development, which made the deposits more scarce. Today, this material has the danger of being reckoned as a gemstone. The comparison will make it possible to understand how rare this material is. Even diamond is mined in several dozen places. The described rock, as Siberian charoite, may well completely disappear without a trace. With a larger grain size of Arkansas, its porosity is greater, which indicates that the rock in this case does not have such significant hardness. It is represented by various varieties, among them: solid, medium, and also soft; the breed lies in separate, often adjacent layers.Back to table of contents
The above stone is often accompanied by another, but it is most common and can be represented by several colors, among them: gray, brown or black. It is called "washita". The mentioned breed is only a variation of soft Arkansas.
Vashita has a larger grain, if you make a comparison with the main stone, in addition, its composition contains a greater number of various impurities.
But this does not make your wash a lower-quality grindstone. In fig. 1, you can see a comparison chart of the approximate grit of Arkansas, Washit and India stones.Back to table of contents
Japanese water stones
Figure 2. Marking and dimensions of grinding stones.
Japanese stones of natural origin have long been recognized throughout the world, moreover, they have the status of stones that occupy one of the first positions in their class. For many years, these stones, especially those that are mined near the quarries located near Kyoto, act as a subject of lust. This results from the fact that the mentioned materials have incomparable abrasive characteristics.
On the territory around Kyoto, you can find a huge number of stone quarries, which are engaged in the production of excellent grinding stones, but in terms of cost and quality characteristics all stones can be divided into two large groups, the first of which is Oriental things, which in Japanese means 東 物; and Western things, translated into Japanese - 西 物. At the same time Oriental materials have a much higher cost, in addition, they are more valuable and respected. The group of Oriental stones includes some varieties, including: Nakayama, Oozuku, Narutaki, Shoubudani, Okudo. If we compare these stones, then Nakayama has great fame among the rest.Back to table of contents
Among grinding stones in the general sense it is impossible not to mention abrasive artificial materials, which are also called bars. Mainly in their composition are grains of electrocorundum, the last of which is represented by an extremely hard material created on the basis of aluminum oxide, which has the following designation in the table: Al2O3.
Figure 3. Table of the application of Japanese grinding stones.
The base may contain silicon carbide, the technical name of which is carborundum; whereas the chemical composition is represented by the designation SiC, the composition may also contain a binder material. The quality characteristics of the bar depend on the quality of the latter and the equal size of the fractions. If it is intended to sharpen a tool using an artificial abrasive stone, then a lubricant should be used, which can be water or a soap solution. Otherwise, the base will soon become covered with steel dust. In fig. 2 you can see the grinding artificial stones, made on the basis of silicon carbide with the addition of a ceramic ligament.Back to table of contents
Artificial water stones
Artificial Japanese water stones are the result of labor, at the time of need a less expensive alternative, because the natural reserves of high quality stones are currently being depleted. This entails that the value on them grows relentlessly. Thus, the price of natural stone, the dimensions of which are equivalent to the size of masonry bricks, can vary within a few thousand dollars. However, an artificial stone, represented by synthetic aquatic material, will have a guaranteed uniform grain size throughout the structure, which cannot be counted on in any case with natural material. Japanese grinding stones, which are of natural origin, are usually used by private craftsmen, as well as by those who consider themselves lovers of grinding work in the traditional sense.
In fig. 3 you can see a table in which the main features of grinding Japanese water stones are presented, among which are not only grain indicators, but application, as well as abrasive material at the base.Back to table of contents
Table of abrasive materials.
Diamond bars can also have different degrees of granularity, thus, the material contains in the composition of different size fractions of diamond chips. Due to the fact that diamond is the hardest material, it is possible to sharpen a knife with the diamond bar as soon as possible. The diamond abrasive forms a rather aggressive cutting edge, which has a second name, the micro-saw, but it crumbles away soon enough, which causes the cutting edge to become blunt. While water stones with an abrasive grain of a small size form a much smoother base edge, it is much slower to crumble. This means that the cutting edge does not become dull over a long period of operation. Single crystals and polycrystals that are present in diamonds are not so susceptible to chipping.Back to table of contents
Ukrainian grinding stones
Grinding stones are also produced in Ukraine. They are designed specifically for sharpening knives. Such a mission is extremely important, since the requirements for such a stone differ from those needed for industrial machining. Due to the fact that the production of stones is carried out from their own raw materials, their price is much lower than their foreign counterparts. The advantages of such a material are not only availability, but also the characteristics expressed by the optimal qualities of the binder, which is able to provide the most appropriate ratio of wear resistance and renewability of the grain. These stones are available in a large assortment of sizes.
Grinding stone marking scheme.
In the development of this stone were tested all sorts of recipes. Each was tested for suitability to the sharpening process, where the comfort of the work was taken into account. One of the options had to be rejected due to the fact that the work was accompanied by a significant drawback, the formation of an excessive amount of dirt. Despite the fact that the masters are ready to endure such an inconvenience in the implementation of manual sharpening, they did not produce a grinder with a similar recipe, because when using this abrasive in the Apex sharpener system, the dirt is unnecessary.
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South African Zulu Gray Grinding Stones
These stones got their name because of the area in which they are mined in the province of Kwa Zulu-Natal. Despite the excellent quality characteristics, these stones are not so common among domestic sharpeners, because they do not have a century of history, in addition, the material has a very high cost, these factors do not contribute to their rapid spread.
For a razor to produce bringing the working surface of the stone and the side is recommended without fail. When using such stones do not emit a suspension, but if you use another one, then perhaps it will appear. In the work of such material manifests itself quite well. Some masters in advance make a soak in order to achieve a more comfortable work. As a rule, this is done for about half an hour or a little more, but there is no particular difference with the described stone when performing such procedures.
Table of grain markings according to different standards.
The material works perfectly with soapy water, and with the one that does not have additives. With a wide feed closer to the completion of work and the use of water razor begins to stick a little.
Often, oil is used in tandem with the Arkansas. If you apply the described material with him, the result will be excellent. Beforehand it is necessary to drop oil, having rubbed it, by means of a napkin it is possible to get rid of an excess amount. Masters say good and pleasant tactile sensations, the material feels velvety to the touch. No matter what razors are used, the surface reveals itself to be fine with them all.
Specialists who use Zulu Gray stones for sharpening, notice that the tool cuts freely after and meets all the requirements of sharpness.
If you intend to sharpen a razor with such a stone, then at the end of the finishing it is necessary to slightly raise the angle, and you need to do about 30-50 passes for each side of the tool, making such pressure that does not exceed the weight of the razor.
Experts note that they do not use razors, which have been restored, but when testing the described stone and finishing the razors of different production, the results were good and revealing.
Ways of sharpening on water stones.
Some argue that the South African stones can be considered the leading finishing among all others, including a comparison with Coticule and Guangxi and Thuringian slate. It is recommended to use oil, however, water manifests itself as a lubricant just as good. In this case, the price is the only negative, but if it is operated very carefully and for its own needs, it will prove to be very economical. It copes well with bringing extremely hard blades that are beyond the power of some other stones. The grain of the stone is enough for this kind of work.
Before you acquire a grinding surface of natural or artificial origin, you should decide for what purposes and with what intensity you will use it.
If earlier you didn’t have experience with stones intended for turning, and later you plan to use them less frequently, it’s better not to buy expensive material, but to use the help of a specialist.
Factors you should pay attention to when choosing a stone:
- area of use;
- intensity of use;
Stone production Coticule
Table of abrasive ability of materials.
Belgian stones are known for their history, which began 140 years ago. The quarry has the following dimensions: 300x100 m, and the extraction is made at a depth ranging from 50 to 60 m. In order to obtain 1 kg of the above material, it is necessary to mine about 2 tons of rock.
The production of grinding stones involves cutting into individual plates, which are 7-14 mm thick. Due to the fact that the natural material is highly brittle, black Brazilian or Portuguese slate is used as its base. This allows you to get a strong grinding stone. At the last stage is grinding the bars. These works are made by hand, in the process it uses a diamond stone. Each side is polished, and the edges are rounded. In the end, it is possible to get stones of different quality and grade and size.
The dimensions of the pieces are determined by the master, in the process of which the size table is used. Each Coticule stone is the result of exclusively handmade work, which indicates that each product is one of a kind.
There is also the Belgian Blue Stone, the production of which is completely identical to the previous one, but the last stage of gluing is an exception.