Choosing a Sketch Plane

[JillAW]

Another question re: Inventor 2011
I've attached a part file-- a simple cylinder. I am trying to use one end of the cylinder (the end without the external threads) as a sketch plane upon which I create a new 2D sketch. Inventor does not allow me to select this face as a sketch plane...
Question is: Why not?

I understand that I can get around this by creating a work plane on this face.
But why can't I use the face directly as a sketch plane?

[JD Mather]

It is not planar. The original sketch is garbage at a slight angle to horizontal and vertical. Where did you get this sketch geometry? AutoCAD?
The revolve results in conic faces since the line that creates that face isn't perpendicular the axis of revolution.
I recommend you read this document http://home.pct.edu/~jmather/skillsusa%20university.pdf

I recommend you dimension your sketches - in which case the problem becomes rather obvious.

[dshowalt]

As JD would say your sketch is way too complicated with much line segments. And not comstrained fully. Simplify the sketch geometry and fully constrain the sketch.
OOPS JD beat me to it