The current state of technological standards mean that it is possible to roll good-quality gear teeth with cylindrical dies up to a modulus of m = 1.5. When the modulus increases, the kinematic conditions involved in rolling mean that spacing, flank shape and symmetry defects occur to a degree which has a substantial effect on the performance of the workpieces when in use. Profile rolling machines using the cylindrical rolling method are basically designed with either two or three dies. The design used most often in rolling gear teeth profiles is a machine design following the proven two-roll principle (Figure 6.23) with two moving roller slides.