Adding child repositions parent tranform

I am currently working on building an animated door which can be reused through a scene. Based on the tutorials I've watched, in order to get a door to animate properly, I need to first have an empty game object ("hinge") positioned along the edge of the door I want to rotate around. With that in place, I then add the door mesh I want to use (in this instance, an imported .fbx) as a child of the Hinge object. The theory is that I will rotate the hinge and that will rotate the door mesh around the correct point.

The problem I'm having is that, after creating the Hinge object and positioning it where I need it, I go to add the mesh and it repositions the transform of the hinge object to be located at the center of the door panel; then, when I try to move the hinge transform, it moves the whole door (which is what I'm going for, except with the hinge at the door's edge rather than the door's center point.)

Has anyone else run into this problem?