Coolant should always be used to cool and lubricate the drill. The most frequent cause of diamond drill damage is drilling without enough coolant. Never run a diamond drill dry?coolant should always be used to cool and lubricate the drill and to flush out abrasive particles formed while drilling. When used without coolant diamonds turn into carbon under high temperature. This is known as the reverse osmosis process. Water is the most frequently used coolant because it typically provides excellent Proformance at a minimal cost.