For a solid door (probably work with foam core):
You will need
- Rockler Self Centering Doweling Jig
- 1/2" x 18"OAL HSS Extra Long Drill Bit, Straight Shank
- 1" to 3" Timber Framers' Slick ( A slick is a mortising chisel with a real long handle, maybe 24")
- Small piece of 2 x 6 and plywood to build jig
- A lot of patients
For hollow core doors:
- Use the 2 x 6 and plywood to build a jig to hold the bit straight. The regular dowling jig is not sturdy enoug to hold straight for a 12 in depth. The plywood sides should go down at least 18 inches to be self supporting.
- Use the 1/2" bit to create the hole in the jig. Probably want to create more than one, because you will eventually enlarge the hole after a few passes.
- Slowly drill a series of holes across the top
- Use the slick to straighten the sides. Leave the end rounded. Slowly taking 1/8 slivers.
- Mibro 366291 Ultimate Door Lock and Hinge Installation Kit for Wood Doors
- 1/2" Mortise Chisel
- 1/2" thick x 1" wood
- 1/8 hardwood plywood, hardboard or polycarbonate sheets
- Use the small hole saw and jig from Mibro kit to drill series of holes in the top of the door. It should make it to the hollow core
- Use the mortise chisel to square up the box. Also mortise out 1/2 deep about 2 inches each side of the opening.
- Build a box out of the wood and or polycarbonate. The top of the box extends 2 inches past each side. The back should be solid and the top 1/4 of the front should be open for access.
I make no guarantee about the integrity of the door. Congratulations you have now spent about $300 to gain 50 cubic inches of storage.