In grinding, the heat generated is removed from the area of contact by conduction into the workpiece, conduction into the grinding wheel grains, convection with the material removed and convection to the fluid. The partition ratios in surface grinding were estimated from the measured temperatures using a thermocouple technique. A theoretical model for predicting the partition ratio at the grain level is presented. The theoretical model was correlated with measured results to validate the model and establish the effective thermal conductivity of cubic boron nitride (CBN) and aluminium oxide abrasives. The effective thermal conductivity of CBN was found to be considerably lower than the reported theoretical value albeit much higher than the thermal conductivity of aluminium oxide. The findings provide the basis for improved prediction of workpiece temperatures in grinding.