Creating datum plane based on some face but attached to Origin datum plane?

[PedjaS]

It is very tempting to create datum plane by simply clicking some face and then creating datum plane. That is not reccomended due to potential topological naming issues.

But in practice it is often needed to create datum plane that is based on specific face. Now, user has to create datum plane attached to some origin datum plane and then manipulate it to get it to place it where he needs it. That may be laborious task to do.

It would be great to have an option to create datum plane aligned to selected face but attached to appropriate datum plane of the origin. It would not end up not attached to face but to origin plane, thus avoiding topological naming problem.

[drmacro]

I've been using FreeCAD for years...the only time I used Datum planes was when learning how to use them.

For most cases, you can the sketch placement (Part workbench) or attachment (Part Design workbench) properties.

For a single sketch, a datum plane is redundant and superfluous.

[chrisb]

It would be great to have an option to create datum plane aligned to selected face but attached to appropriate datum plane of the origin. It would not end up not attached to face but to origin plane, thus avoiding topological naming problem.

You would loose THE big advantage of FreeCAD: parametric dependencies. Nevertheless it is easily possible: Attach the DatumPlane to get the placement, and then detach it to keep it in this position.

[freedman]

What chrisb said, go to Map Mode and Deactivate it, you can also reactivate it and it will reattach (as long as you haven't had a topo-naming error). You can also do the same with a sketch as said.
Datum planes can be good for visualization, applying multiple sketches to a surface and moving sketches at angles.