Diamond powders are the abrasive base of diamond stones. They consist of natural or synthetic diamonds and are divided into two groups: grinding powders and micropowders. Grinding powders are usually used in the manufacture of diamond tools, while micropowders are used for pastes and suspensions. In the Russian diamond industry, for organic bonded stones (intended for sharpening tools), two types of grinding powders are mainly used:
1) AC4. From synthetic diamonds, grains of which are represented by aggregates and aggregates.
2) AC6. Synthetic diamonds, the grains of which are represented by individual crystals with a developed surface, aggregates and intergrowths.
A high quality diamond bar has an inherently higher aggressiveness of cutting precisely because of the grains that protrude excessively above the working surface. In the course of work, these grains either break off or chip out of the bond, and after a short period of initial use, the stone reaches its nominal cut and should last a very long time in this condition.
The organic binder itself consists of phenol formaldehyde resins and various compositions based on them. During hot pressing, the compositions are bakelized into a hard and sufficiently strong substance that holds the cutting grains in the working layer of the tool. At the same time such a bond will be strong enough and ductile enough, but not stiff enough.
The concentration of diamond powder is an important factor in the effectiveness of such a bond. For AC4 and AC6 grinding powders, this concentration leaves 50% or 100%. It is the concentration of diamond in the powder that determines its cutting ability, performance, service life and cost. The choice of concentration depends on the type of tool, the shape and size of the working surface, the grain size of the diamond powder, the wear resistance of the bond, and the machining conditions. To prevent such a bond from being too soft and ineffective on materials with high hardness, additional abrasive grinding powders, such as boron carbide, are added to it.
However, for sharpening the cutting edge of a knife, the bond can be even softer than for a specialized tool without losing effectiveness. For this purpose, the most advanced technology, used, for example, in the production of the Venevsky Diamond Tool Factory, are bars on a new modernized OSB bond. It is based not on grinding powder, but on ACM micro powder made of synthetic diamonds of normal abrasiveness.
What makes OSB bonding different from others is that it does not use boron carbide. In addition, the abrasive layer on it is not sintered, but glued to the body of the metal plate. At the same time the concentration of diamonds in these bars is 100% and already out of the box they are ready to work and do not require leveling on silicon carbide powder. OSB is ideal for hard steels at small angles. You can work on this bond with both soapy water and oil. While the manufacturer himself recommends working with either water or soapy water, working with oil gives an excellent result in terms of cleanliness of the process itself, without leaving such a large amount of water slurry.