Sorry about the new thread, but I marked the thread as read and then decided to reply. In a previous home, I had a 42" doorway 8' tall between a storage room and my garage. I wanted the large opening to move equipment in and out easily and had no intention to pay "whatever" a commercial door would cost. I made my own door using 2 sheets of birch faced high density board, together with a single sheet of MDO in the middle. The door was thus
2-1/4" thick. For interest, I routed in, using a 3/8" veining bit, detail that simulated a 5-panel door.
My concern was the strength of the particle board material when it came to holding the hinges I felt I needed. To solve this, I stood the door upright on my table saw and my neighbor and I used the blade fully extended to cut a kerf in the center of the hinge edge of the door. I centered the kerf and inserted a full length piece of 3" wide, 1/8" thick steel, screwing it fast from the store room side in probably 20 locations along the door. Then, I used overlay (gate-type) hinges to hang the door, bolting through the door and its steel insert.
The rest was just typical addition of hardware, using an extended rod between the knobs.
Nonny