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Abrasives Basic Knowledge

Abrasives wheels knowledges

It's will help you do much better cutting and grinding works if know some basic knowledge of abrasives Wheels.  Normally the abrasives wheels can be classified two kinds - Bonded Abrasives and Coated Abrasives. 


The bonded abrasive is composed of an abrasive material contained within a matrix, although very fine aluminium oxide abrasive may comprise sintered material. The matrix is called a binder can be clay, resin, glass or rubber. The mixture of binder and abrasive is typically shaped into blocks, sticks, or wheels. For BLUESHARK Abrasives, the bonded abrasives mainly refer to resin bonded cutting and grinding wheels.

a) Main Abrasives Grain


The most abrasive materials used is Aluminum Oxide , White Aluminum Oxide and Silicon Carbide. 

* Aluminum Oxide : The most common of all abrasives and mainly used for heavy-duty, general-purpose work.

* White Aluminium Oxide: The high friability of this grain bring the characteristic of sharp and cooling cutting performance, used for light grinding of steels and specially for stainless steel.

* Zirconia Aluminium Oxide: High performance grinding and extra long life. Excellent on ferrous metals, castings and stainless steel.

* Silicon Carbide: Mainly using for grinding masonry, concrete, stone, and non-ferrous metals.

* BLUESHARK innovative mixed Green Ceramic Oxide: High self-sharpness performance and extra long life and specially for make " All in One " superthin cutting discs.

b) Bonded Abrasives Making System

Type of Abrasives                        Grit Size                       Hardness Grade                       Type of Bond                

A= Aluminum Oxide                   Coarse 16~24                   Soft - N,O,P                    B=Bakelite/Resinoid Bond

C= Silicon Carbide Oxide            Medium 30~60                  Medium - Q,R,S              BF= Resin and Fiber Bond
Z= Zirconia Oxide                       Fine 80~100                     Hard - T,U,V

For example:  A30 T BF - means the discs made from Aluminum Oxide and grit size is 30# ( or maybe mixed grit size and mainly is 30# ), The bonded hardness is "T" ( hard style ) and bonded by resin and fiber reinforce nets.

c) Shape System

Depressed center grinding wheels and normally thickness from 4~8mm and out diameter from 50~230mm. 


Flat cut-off wheels and normally thickness from 0.8~3.0mm and out diameter from 75~400mm.

Center depressed cut off wheels and normally thickness from 2.5~3.2mm and out diameter from 100~230mm.



Coated abrasive comprises an abrasive fixed to a backing material such as cloth, paper, rubber, polyester.etc,  many of which with "flexible" performance such like Sanding Paper .  In fact . coated abrasives are commonly using the same minerals which  used for bonded abrasives. For BLUESHARK Abrasives wheels, the coated abrasives refer to Abrasives Flap Discs, Fiber Discs, Velcro Discs, Flap Wheels.etc. 

Coated abrasives are manufactured with the following components.
*Backings – Carrier for which the abrasive grain is adhered to.
*Coating & Bond – The adhesives that holds the grain onto the backing.
*Abrasives Grain – The type of abrasive used for the particular material being produced.

 a) Backings

There are multitudes of different backings that can be used in coated abrasives. The most common types are paper and cloth. The film and fiber also can be used for certain applications.Paper backings is used for a variety of operations from hand sanding to mechanical sanding . Paper backings weights include A, B, C, D, E and F and suitable for produce different coated abrasives.

Paper Type              A               B               C               D                E                F
Weight (g/m2)      75~89       90~119      120~149     150~199      200~250        >250
Cloth backings are identified by weight . Cloth backings are filled or “finished” with a variety of materials such like glues or resins, There are three basic weights of cloth: J, X , Y. 
J - Cotton cloth with medieum weight
J-Flex - Cotton cloth with light weight and very flexible
X - Cotton cloth with heavy weight
X-Flex- Cotton cloth with heavy weight and flexible
YY - Polyester cloth with extra heavy weight
YX - Polyester cloth with heavy weight          

b) Bond type

An adhesive bond system is required to secure the abrasive grain to the backing .Glue, urea resin, and phenolic resin are the three basic bonding agents most commonly used. Also there are many coating combinations such as glue over glue, urea over glue, and resin over resin   
All coated abrasive products are made with two-stage bonding process .

1) Coat making -The first layer of bond applied to the backings and provide the adhesive base between the abrasive and the backing .
2) Size Coating - Applied over the abrasives and make coat to anchor the grains and provide the desired physical strength of the finished product .

c) Coating type
There are two types of abrasive coatings used in the manufacturing of coated abrasives: open coat and closed coat.

coated abrasives coating type

Open Coat - With an open coat, 50% to 75% of the coated abrasive surface is covered by abrasive grain . There are evenly spaced voids between the particles of grains.

Close Coat
With a closed coat, the entire coated abrasive surface is covered with abrasive grain, with no voids between the particles .   

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