If you really want to take advantage of manipulating the projected curve --where the surface is a cylinder, or something that will result in two projected curves -- just copy the surface (solid) to one side, cut it in half (eliminating the back side), project and manipulate the curve until you have what you want, then move that curve back onto the original surface. Remember to set the endpoints.

after reading your last note that is exactly what i have been doing thanks again....ps i have spent more than 4 hours trying to make this tap in an intelligent way...fail after fail...with imperfect surfaces.