Oil vs Water-Based Coolant for Gun Drilling: What Works, What Does Not, and Why
I have run gun drilling with both oil-based and water-based coolants across hundreds of jobs. The choice between them is not about which is better in general — it is about what matters more for your specific work: tool life and finish, or cost and cleanliness. Here is what I have found. The Core Difference: Lubrication vs Cooling Oil lubricates. Water cools. That simple distinction drives every other difference. A gun drill cutting edge needs lubrication to reduce friction between the tool and the workpiece. Oil does this naturally. Water-based coolants need chemical additives to approach the same level of lubricity. ...