I want to start a sketch on the end of the fat end of the attached part.  It's a flex part and I guess this is part of the problem. The part is exactly 1/4 of a full diameter so the two ends are at 90 deg to each other.

I also tried to setup a plane off this face, I thought that might work but no joy.

Maybe I have created the flex part incorrectly or what I am trying to do it just not possible.

Help appreciated and happy New Year.

Thanks, Daniel.