DIAMOND GRIT SIZES

Grit size determines to a large extent the performance of a diamond tool regarding grinding efficiency and ground surface quality. In order to get desired results accurate grit sorting is needed by sieving and sedimentations operations thoroughly carried out.

DIAMOND CONCENTRATION

Concentration is the ratio between the weight of diamond in carats (0.2 g) and a cubic centimeter of bond. In accordance with FEPA standards, concentration 100 relates to a diamond content of 4,4 carats in a bond volume of one cubic centimeter; all other concentrations are proportional. The diamond concentration has a considerable influence on the cutting qualities and price of diamond tool. The below table 6.1 lists some of the usual values for concentration.

BOND

Among other factors, the bond determine to a large extent diamond tool performance and the quality of grinding operations. That is why the choice of the bond is very important and in the same time quite difficult, seeing that there in a great variety of diamond grains. It is therefore necessary to devise specific bonds with the view of achieving the best bond-diamond grain combination vs. processing material conditions.

In addition to this, in order to select adequate bond, it should be taken into consideration other important parameters such as:

• the material and depth of cut;

• working conditions;

• processing efficiency;

• diamond layer size

• concentration of diamond grain.

On the bond type (hard or soft) depends whether a diamond performs:

• short durability, rapid grinding, without heating up and without developing high processing force or;

• extended durability, slower grinding, developing higher pressing force.

A hard bond is suitable for:

• small diamond layers or cutting surfaces;

• rough diamond grains;

• high diamond concentration;

• necessity to maintain for a longer time the cutting profile;

• wet grinding.

A soft bond is suitable for:

• large abrasive layers or cutting surfaces;

• fine diamond grains;

• low diamond concentration;

• parts sensitive to heating and edge wear;

• dry grinding.

The durability of diamond tool depends to a large extent on the wear bond, but the best solution is not that of minimum one. It should be chosen a bond with the most economical chip discharge expressed by wear ratio (“G” ratio)

G = quantity of removed material (cm³) / quantity of consumed diamond layer (cm³)

The G ratio is not a constant of the grinding wheel: with a linear increase in the volume of metal removed per unit of time, wheel wear increases exponentially.