Grinding is an abrasive machining process that uses a grinding wheel as the cutting tool. A grinding wheel is a precision tool with thousands of cutting points on its surface - abrasive grains that are held in place by a bond matrix (hence these are known as bonded abrasives) and separated by pores. When the wheel is in use, the abrasive grains cut into the material that is being ground, removing the unwanted surface material in small chips.
There are various grades of grinding wheels available in the market and every grinding wheel has its grade written on it. But have we ever thought what these grades mean? We will decode the grade of the grinding wheel in this article.
When selecting the perfect wheel for your project, it is important to know the grade of that grinding wheel. Every grinding wheel is marked by the manufacturer with a stencil or a small tag. The manufacturers have worked out a standard system of markings as shown in the figure below. For example use a wheel marked A36-L5-V23. The A refers to the abrasive which is aluminum oxide. The 36 represents the grain size. The L shows the grade or degree of hardness, which is medium. The 5 refers to the structure of the wheel and the V refers to the bond type.
ABRASIVE TYPE:
There are 4 main types of abrasive grains available for grinding wheels, these are Ceramic Aluminium Oxide, Silicon Carbide, Zirconia Alumina, Aluminium Oxide.
ABRASIVE GRAIN SIZE:
Abrasive grains are selected according to the mesh of a sieve through which they are sorted. For example, grain number 40 indicates that the abrasive grain passes through a sieve having approximately 40 meshes to the linear inch. A grinding wheel is designated coarse, medium, or fine according to the size of the individual abrasive grains making up the wheel.
GRADES OF HARDNESS:
The grade of a grinding wheel designates the hardness of the bonded material. Listed below are examples of those grades:
A soft wheel is one on which the cutting particles break away rapidly while a hard wheel is one on which the bond successfully opposes this breaking away of the abrasive grain.
STRUCTURE:
Bond strength of a grinding wheel is not wholly dependent upon the grade of hardness but depends equally on the structure of the wheel, that is, the spacing of the grain or its density. The structure or spacing is measured in number of grains per cubic inch of wheel volume.
BOND TYPE:
This means how the wheel holds the abrasives; affects finish, coolant, and minimum/maximum wheel speed.
So, now you know how to read the grade of grinding wheel. Thank you for reading this article.
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