How to rotate an object from a single vertex sub-object

There is a particular setup you need to rotate from a subobject.

Note: this is for modeling use only and does not work with Autokey on.

Make a 1x1x1 segment box ... don’t go into the subobject... and FREEZE the selection. The reason has to do with something called relative snap, but this first exercise will work without it.

Set up rotation to use transform coordinate center and set snap to vertex. Open Axis constraints.

Hover over the vertex. Do not go to the sub-object level vertex, just hover over the corners. Watch for the little blue cross.

 

when you rotate max will prefer one axis over another.

use axis constraints to select the axis you want to rotate from. You can rotate from any single vertex without changing the locked selection.

  

This is how to rotate multiple sub-objects from a single vertex

Select vertices and lock selection.

Turn on snap to vertices.

Set rotation to use selection center

 

Pick any vertex you want to rotate from, iow, using it as a pivot point.