Changes of torque during foundry bentonite granulation in disk granulators were studied. Variable parameters were the diameter and inclination angle of the granulator disk and filling of the disk with granular material. The bed of loose material was wetted drop-wise during tumbling, at a constant volumetric liquid flow, by a sprinkler that ensured uniform supply of the wetting liquid. In every trial the instantaneous values of net torque were measured. The effect of the disk diameter, its angle of inclination, filling with raw material and moisture content of the granulated bed on torque changes was assessed. A correlation equations was proposed to describe the effect of the above parameters on the reduced torque change.