Tests on a precision surface grinder compared constant-stiffness and constant-natural-frequency isolators. The graphic shows relative vibration amplitudes between the grinding wheel and machined surface with the machine installed on five CS isolators with natural frequency fvz = 15 Hz and on five CNF isolators, fvz = 20 Hz. Relative vibrations are about 30% lower when the machine mounts on stiffer CNF isolators.