Replies

1. 
   pzaxtl | Jan 27, 2009 07:05am | #1

   Standard hollow core doors, common in many homes throughout North America are built with hardboard, which is essentially the same as MDF, so MDF is definitely an option.

   Why not make a frame and panel door and glue the MDF panel in place?  With a glued-in panel, the door would be plenty strong, even if the frame is built with stub tenons.  You could also use veneer core plywood for the panel if MDF doesn't appeal to you.

2. 
   terrylee86 | Jan 27, 2009 05:15pm | #2

   MDF is not your best option.  MDF is wood flour and glue, though very stable, is not very strong.  A better option in your design would be particle board because it has larger wood chips is stronger and is still stable.  Solid core interior and exterior doors are made of particle board(chipcore) solid wood frames(stiles and rails) and a verneer face glued up in a press.  They are very stable,but quite heavy.  You would have to rig up some kind of press to assure maximum flatness and bonding strength.

3. 
   acornw | Jan 28, 2009 01:20am | #3

   I (we) have built hundreds of plank doors with a 3/4" hardwood - same species as the faces - ladder frame. It is the mortise and tenon joints in such a frame that gives the door its rigidity to prevent sagging. The fact that it is real, tree-grown hardwood gives it the torsional rigidity that such a door needs and keeps it flat. Man-made materials cannot do this. We then do planks on both sides.

   The doors do end up at 2-1/4" thick if you use 3/4" T&G faces. Since these doors mimic the high security doors of the middle ages, that is not a problem. You will not find any historical examples of these doors at less than 1-3/4". Indeed, you can get 1-3/4" by making 1/2" faces with a shiplap joint.

   I do not believe one can 'improve' on these doors by substituting man-made or 'engineered' materials. The door is a real thing, not a facsimile, so it is only proper to follow suit with real materials and methods throughout. I have never regretted it, nor have my customers.

   Just my opinion, though.

   Dave S
   http://www.acornwoodworks.com

1. 
   JohnCujie | Jan 28, 2009 01:31am | #4

   Thanks Dave. I made my ladder frame with two intermediate pieces so I had three equal spaces. I glued the T&G face pieces at the perimeter of the frame and across the four horizontal pieces (top, bottom, and 2 center pieces). Is this correct? I am unclear on wood movement on this type of door as opposed to a floating panel.I like your philosophy, John

   Edited 1/27/2009 7:31 pm ET by JohnCujie

1. 
   acornw | Jan 28, 2009 04:33pm | #5

   I think you have it right. By gluing each board in place, with a small gap between boards, each board can move in its place without affecting others or the flatness of the door. 4" to 5" wide boards, even flat sawn Oak, don't move that much -like a 36" board would.Older doors (hide glue) used plugged screw holes and screws to fasten the boards, with two screws across the width, dividing the board into thirds. This meant that only one-third the width of the board would move under the screw restriction. Minimal movement at worst. Dave S

   Edited 1/28/2009 8:35 am ET by acornw

1. 
   brad805 | Jan 28, 2009 08:21pm | #6

   I have not noticed too many posts from you lately.  Always interesting to read your replies here and on the Woodweb.  Hopefully you keep notes for that Door book:) 

   Brad 

1. 
   acornw | Jan 28, 2009 10:23pm | #7

   Actually, we have been so busy it has been hard to find time to do much else but quote work, then draw it and schedule it into the shop. Our area has always been somewhat immune from the economic ups and downs, and here we are busy. Other shops and the rest of the local industry is down. The book is far down the list currently. If I could just get that publishing agent that Laura Bush and Sarah Palin use, maybe I could get a nice 7 figure advance.Dave S