@thomthom said:

No - I wondered if it preserved it.

I wanted to only move and rotate the object to a new plane. I wondered if this method would be an option as oppose to combining a translation and two rotation transformations.

Well, first you have to determine which axis gets priority (because the angles between the axes in the original transformation may not be the same as the angles between the axes the user picked) then measure the angles between the prioritized axis and the other two, and apply the angles to the user axes (including face normal).

I'm pretty sure that doesn't make sense but I can't think of how else to describe it.

If you have any specific questions, I might be able to help a bit more.