There is disclosed a crusher for crushing material into finer particulates, the crusher including a housing that encloses a crushing head mounted on a shaft. The housing supports an outer crushing shell, while the crushing head supports an inner crushing shell. The two crushing shells cooperate to form a crushing gap therebetween. The crusher further includes a drive mechanism joined to the shaft for generating movement of the inner crushing shell relative to the outer crushing shell. The drive mechanism includes at least three drive units joined to the shaft and configured to impart a pulling force on the shaft. Also disclosed is a method of operating the crusher, wherein each of the drive units are selectively activated and deactivated to selectively generate orbital or gyratory movement of the crushing head relative to the outer housing.