The grinding stone is generally determined by JIS (Japanese Industrial Standard) to display the following.
JIS is a national standard established based on the Industrial Standardization (1949) for the purpose of promoting industrial standardization in Japan, and the scope is wide, and all industrial products have standards for unifying the shape, quality, performance, production method, test method, etc. nationwide.
|Shape||Edge type||Size (outer diameter x thickness x hole diameter)||Abrasive grain||Grain size||Binding degree||Tissue||Binder||Subdivision symbol||circumferential speed|
It is universal except for abrasive grains and subdivision symbol. (For abrasive grain, general abrasive grain (other than mixed abrasive grains) is common).
Edge type…A ~ P
Abrasive grain…Coarse-grain to fine-grain
Binding degree…Soft to hard
The tissue…Dense to coarse
There are two main types of general abrasive grains. One is alumina-based abrasive grains (alundum) and the other is silicon carbide-based abrasive grains (Carborandam).
Alumina-based abrasive grains include brown alumina-based (A), white alumina-based (WA), and single crystal alumina-based (HA). It is mainly used to shave iron-based materials such as steel and hardened steel. Abrasive grains become harder in the order of brown < white < single crystal, and the cut also improves. There are many types of abrasive grains, and they are often used.
Silicon carbide based abrasive grains include black silicon carbide-based (C) and green silicon carbide-based (GC). It is mainly used to shave hard and fragile materials such as stone and cast iron. The hardness of the abrasive grains itself is almost the same for both C and GC, and on the other hand it is harder than alumina-based abrasive grains, but there is no stickiness, and it is used when cutting non-ferrous metals such as aluminum and copper, cemented carbide, because there is a drawback that wear is quickened by reaction when cutting iron, and the grinding surface becomes cloudy. When comparing C and GC, the abrasive grain shape of C is sharp and GC is blocky, so choose it according to the application.
There are other zirconia alumina abrasive grains (Z). It is very sticky and used for resin-bonded grinding stone for heavy grinding. In addition, mixed abrasive grains of alumina and silicon carbide are often used in resin-bonded grinding stone, but in the case of vitrified grinding stone, it is easy to be broken due to the difference in the thermal expansion coefficient between the two. Be careful when using it.
Super abrasive grains include diamond and CBN. Diamond is harder than silicon carbide, CBN is harder than alumina. When actually using it, please use several finer grained grains than general abrasive grains.
Abrasive grain has roughness, and its criterion is grain size. Generally, coarse ones are used for deburring, cutting, etc., and are used for finishing as they become finer. Grain sizes up to 220 are called general abrasive grains, and finer ones are called fine powder.
Generally,when used in equivalent usage, vitrified grinding stone tend to have a rougher grinding surface than resin-bonded grinding stone. For this reason, resin-bonded grinding stones are often used for final polishing. In addition, super abrasive wheels tend to have a rougher grinding surface than general grinding stone. For this reason, it seems that super abrasive wheels often use finer details than grinding stone.
When used in free grinding, compared to sandpaper, etc., the count sold in general seems to be very rough, but due to the small amount of abrasive grains and the high speed of machine operation, etc., it becomes a finer surface than expected.
The ideal grinding depth when used in precision grinding is said to be about 1/10 or less of the average abrasive grain. Also, when grinding in the same way, it seems that a grinding stone with a large outer diameter often chooses a little rough because the contact area is larger than a small grinding stone.
The hardness of the grinding stone is called binding degree. A is the softest, and the closer you get to Z, the harder it becomes.
If the grinding stone is too hard, it will cause glazing, clogging, burning, cracking, distortion and so on. On the other hand, if it is too soft, it will cause overlooking, vibration, biting, tataki, flying, and destruction of the grinding stone.
Generally, hard grinding stone is used for soft workpieces, and soft grinding stone is used for hard workpieces. In general, small and hard grinding stones are made stronger.
The percentage of abrasive grains in the grinding stone varies from one to another. You can see this figure by how much abrasive grain is contained in the grinding stone. At 50%, the tissue is "6", with 2% abrasive grains increasing, the tissue decreases by "1", and with 2% abrasive grains decreasing, the tissue increases by "1". In general, the tissue "7-8" is used for grinding.
In addition, a grinding stone whose tissue exceeds "10" and has large stomata is called a porous grinding stone. It cannot be used at high speed, but it is effective for clogging and burning. In Teiken, the Dolce series and the PT series correspond to this.
I mentioned in the three elements of the grinding stone that there is a binder (bond) in the thing that forms the grinding stone, but there are various kinds of binders.
Vitrified (V)…feldspar, frit etc. (Ceramic)
Resin-bonded (R)…Pasphenol resin and other synthetic resin
Resin-bonded reinforcement (BF) … Containing a reinforcing material such as glass fiber in a resin-bonded grinding stone
Rubber (R)…Natural and synthetic rubber
Silicate (S) …Soda silicate (water glass)
Magnesia (Mg) … Magnesia oxychloride (magnesia cement)
Shellac (E) …Shellac (Natural resin)
Currently, Teiken mainly produces vitrified and resin-bonded grinding stones. We also produce epo grinding stones as a substitute for magnesia grinding stones. The indication of this grinding stone is "E" for convenience, but it is actually a kind of resin-bonded grinding stones.
In addition to the above, there are also grinding stones using PVA (polyvinyl alcohol) and urethane, and in the case of super abrasive grains, wheels (metal bond wheels) using metal as a binder.
Currently, there are two types of notation for the circumferential speed display. One is m/ min (minute speed display) and the other is m / s (second speed display). Currently, there is a movement to unify the latter, and JIS standard has become the latter in recent years, but since the display of the machine may be the former, both may be described.
Each other's numbers can be converted by 60 m/min = 1 m/s.
Also, the peripheral speed and the number of revolutions are different.
Circumferential speed (m/s) = diameter of grinding stone (m) x 3.14 x number of revolutions (rpm) ÷ 1000 ÷ 60.
The circumferential speed indicated on the grinding stone is the maximum used circumferential speed and should never be used beyond this speed. Although it is safe to use it at a slower peripheral speed, normal grinding stones are manufactured on the premise that they will be used at 16 m/s (1000 m/min) or higher, so if the peripheral speed is too slow, the efficiency may be extremely low.
In general, if the circumferential speed of the grinding stone is fast, it will hit hard, and if it is slow, it will hit softly.
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