Rotation without loosing diameter?

[micheus]

Hi, is it possible to rotate the top area of a cylinder around x for example without loosing the diameter of the cylinder?
In the standard way the rotation of the top area deform the cylinder into a (partially) oval...

It always help if you put an image, but I think you are rotating the top of a cylinder with only the top and bottom faces - no segments (edge loop) in the middle.
If that is the case, you will need to create some edge loops in the middle of it (>= four segments - cut 4) and instead of use the Rotate command you should to select the entire object and in Vertes mode [V] use the context menu Deform->Twist->X and twist the vertices as you need.


OBS: This kind of question should be post in the Interface & Usage session - I'm moving it to there.