After describing geometric characteristics of a PDC drill bit’s waterway surfaces, an approach for collision-free trajectory generation are proposed. The trajectory is planned by an iso-parametric method firstly, while the tool orientations are determined by visibility cones, which are the bounded regions between the opposite surfaces of neighboring blade wing pairs. Tool orientations are produced by calculations of critical points and interpolations between them. Furthermore, the criterion of whether tool orientations pass through the constraint surface and the linear interpolation formula of tool orientations are given. The research has created conditions for the success machining of PDC drill bits, and related machining enterprises of impellers and propellers will also be benefited.