Part Modeling > Datum Features > Datum Planes > About Creating a Datum Plane Tangent to a Surface
  
About Creating a Datum Plane Tangent to a Surface
You can create a datum plane that is tangent to a surface and that passes through one of these references: a datum point, a vertex, or an endpoint of an edge. In the Datum Plane dialog box, set the constraint next to the surface reference to Tangent.
The datum plane can be tangent to these surfaces:
Conical surfaces
Cylindrical surfaces