Surface tension and viscosity are viewed as important, intrinsic, properties of a metalworking fluid (MWF) for temperature reduction and lubrication. In this paper the link between these fluid properties and the functionality of the MWF is examined in terms of cutting forces and machining temperature. Testing was carried out on an instrumented drilling test-bed to evaluate the effect of surface tension and viscosity on cutting temperatures and forces. The findings confirm that surface tension and viscosity of a cutting fluid play important roles in cooling and lubrication of the drilling process. A lower surface tension, independent of the type of chemical used to lower it, provided better cooling and resulted in lower temperatures during machining. Separate experiments with varying viscosities showed that as the viscosity of a solution increased, the machining forces and temperatures decreased. This implies that hydrodynamic lubrication is an important contributor to MWF functionality.