Thermal Aspects of Grinding with CBN Wheels

When grinding with CBN wheels, thermal damage is unlikely at the removal rates normally used in production. This decreased thermal damage with CBN wheels as compared with aluminum oxide wheels is usually attributed to the lower specific energies with CBN. Another contributing factor is the very high thermal conductivity of CBN, which enhances conduction into the grains. This beneficial effect may be offset by the sharpness of the CBN grains, which lowers the area over which conduct ion occurs. This paper presents a model of the thermal aspects of grinding which predicts the critical removal rate at which workpiece burn occurs. The effects of specific grinding energy, grain thermal conductivity, and wear flat area are explored. The model suggests that conduction into the CBN grains has the potential to increase the critical removal rate by a factor of 20 or more.