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Grinding Wheel Application
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The Grinding wheel is nothing but a multipoint and multilayered cutting tool where a number of abrasive particles, which are bonded together to form a solid mass, cut definite chips from the material being worked upon.
The grinding wheel essentially consists of two main constituents. |
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Abrasive grains |
They form approximately 80% of the mass of the grinding wheel. |
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Bond |
It binds the grains to a definite shape and strength. |
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Abrasives
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| They are the set of materials which do the actual cutting. They are basically of two types:- |
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Natural |
Natural abrasives are Diamond, Flint, Quartz, Emery, Garnet etc. They are not used in the manufacture of grinding wheels as their physical characteristics vary from sources to source as well as from within the same source. Thus grinding wheels, if manufactured with these abrasives, will be inconsistent in their performance, which goes against the mass manufacturing techniques and expectation of repeat performances from the manufacturing tools.
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Synthetic |
As the name suggests, they are man made abrasives and are imparted the desired properties of hardness, toughness, cleavage lines etc. These properties can be maintained and duplicated within desired tolerances.
From a raw material having uniform properties we can expect to manufacture a grinding tool which can be consistent in its performances within a set of given identical conditions. The synthetic grains used for the manufacture of grinding tools are
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From the above types the most commonly used varieties are :-
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Aluminium Oxide |
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Silicon Carbide |
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These can be further broadly classified into the following categories which are most commonly used:-
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Aluminium Oxide |
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(a)
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Brown Aluminium Oxide |
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(b)
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White Aluminium Oxide |
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(c)
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Pink Aluminium Oxide |
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Silicon Carbide |
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(a)
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Black Silicon Carbide
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(b)
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Green Silicon Carbide
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BONDS
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They are the set of materials used to bind the grains to one another to get a solid mass of desired shape, hardness etc. Thus the name given to grinding wheels and other grinding tools is Bonded Abrasives.
Bonds are of the following types,
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Vitrified |
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Resinoid |
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Rubber |
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Shallac |
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Magnestie / Oxychloride |
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Metallic |
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Of the above mentioned bonds the first two are most commonly and widely used. Whereas the other types find only limited use, and that too for specific operations and conditions.
In order to manufacture a grinding wheel for use in a given set of conditions giving optimum efficiency we will have to select first a suitable abrasive for the job.
Selection of the type of abrasives is guided by the type of material, its hardness, grinding operation and its severity etc. The general guide lines are
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Aluminium Oxides are best suited for steels and ferrous metals of high tensile strength. |
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Silicon Carbides are ideal for grinding cast iron, non ferrous metals and non metals, in short materials having low tensile strength.
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Following figure gives the general idea of efficiency of A type of abrasives and C type of abrasives with the increase of tensile strength of the material to be ground.
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