Abrasive Mixing Valve: The abrasive mixing valve is used to meter the amount of abrasive entering the abrasive delivery hose. A properly adjusted abrasive mixing valve will eliminate all abrasive delivery surge and also allow re-adjustment when changing abrasive sizes. Machines without mixing valves or machines without quality mixing valves will never be capable of the fine adjustment required for the wide variety of abrasive sizes in the industry today.