Cylindrical gears with circularly curved tooth trace, and particularly the type(s) that have a constant transverse pressure angle across the face width, are of four degrees of freedom; the unidirectional drive meshing deprives the pair only of asynchronous rotation and axial mobility. The gear pair is thus of (quasi-) exact constraint design. And this is what imparts this gearing dynamibility, when compared with all other known types of parallel-axis gearing. The fundamental types of gears with circularly curved tooth trace are described and the problems and limitations pertaining to their operation and/or manufacture are pointed out. It is shown how one particular type lends itself to a novel, hitherto unknown generating cutting method that avoids all the shortcomings. Full details of the generating kinematic process for these gears and of the suggested machine tool configuration required to perform such are given. The same could be used for electro-chemical generating grinding of the gears.