I think of rotation about any axis as if I inserted into the object a skewer along that axis, and rotated the skewer. For example, rotating an object laying on the desk is achieved by rotating about the Z axis, since the "skewer" is pointing up along Z axis.

This works well in OpenSCAD and I just saw that Slic3r displays a handy arrow in the 3D preview when you focus the text box that controls the rotation

> May I ask a stupid question, can you explain how rotation works in any of those? All three axes...

What type of rotation you mean? (part rotating/posing or "spinner"/"rotor" animation)

Just turning the object on zx or zy axis (for freecad or bricscad - same issue - probably some bad ux copied from autocad). Rotation, as simple as that, center axis or any selected point. Lightwave modeler with its 4 views was understandable (always rotating on xy axis for current view) but freecad (and bricscad) is making me problems understanding how this actually functions in same manner as initial orientation of set object, i just cant figure out the logic.

(Doing 3d printed speaker stand for 3d and I am workarounding this "issue" in sweat and tears ;) )

Your question still is unclear.

> Just turning the object on zx or zy axis

There are no such type of axis, because "XY", "ZX", "ZY" — are planes formed by two crossed axis combination ("XY" plane formed by crossed "X" and "Y" axis, etc.).

> Doing 3d printed speaker stand for 3d and I am workarounding this "issue" in sweat and tears

If you mean that you need just rotate solid object from horizontal to vertical (for 3D printing) — there are few ways.

Well sorry cant explain it better (i lack the terminology, just started playing with) but looks like UCS is involved... Thank you anyway will try to figure it out on my own.

Can you draw the problem? (give some schematic image of the task)