Flow on a rotating cone with an apex angle of 15 degrees is studied through flake visualizations, both in still fluid and with axial flow. From recorded movies, the reflective light intensity at generating lines is extracted and its development is evaluated in space and time. The results show that increasing axial flow moves transition downstream, whereas increasing rotational speed has the opposite effect. We found that the transition process can be scaled by the von Kármán viscous length scale and a globally defined axial velocity.