EDIT: I entered this in the Metalworking contest - if you dig it, please give me a vote!

After moving into our new (old) house, it went unnoticed that the mailbox had seen better days until the mail started arriving lol.

I realize next to nothing useful comes thru the mail anymore (save for the odd, small package once in a while) - but I see it as an opportunity to add a little personality to the curb appeal.

For this effort I used the following:

8" Round Duct (Came as a 5' length) [Home Depot]
(2) 8" Duct Caps [Home Depot]
Small Cabinet Hinge [Home Depot]
Spray Paint [Home Depot]
Cabinet Knob (Resin copy of a shotgun shell base) [Amazon]
Silicone Sealant [Home Depot]
Mail Flag [Home Depot]
Universal Mounting Plate [Home Depot]

Step 1: Measure and Cut

The 8" diameter is close to the same area opening as a regular mailbox so I chose an 8" steel duct to make the mailbox. 22" - 24" is close to the length of them as well, so I chose to cut the duct to 24", using a steel cutoff wheel in an angle grinder. It cuts like butter - but the operator isn't always as steady as he wishes!

The duct caps fit over the crimped end just fine, but the uncrimped end is too large to simply slip the cap on. By taking pliers and bending in slightly around the perimeter, the resulting reduced diameter allows the cap fit on this end as well.

I put the cap on all the way (on the end I modified), then with a rubber mallet hammered the edges down as best I could. Lastly, I put a bead of sealant around the inside joint to help keep the weather out.

Step 2: Fabricating a Door

This part I'm not particularly satisfied with. Living in Arizona I don't have much weather to really worry about save for occasional summer rain storms, so that's all I'm trying to minimize intrusion against.

I laid out the end cap and where I thought the hinge should go. I wanted it off center, so the knob that replicates the primer could still be fitted to the center as well as allowing plenty of room for hands and mail to get in easily. I scored the line, marked and drilled the holes for the hinge screws, and then cut the cap with the cut off blade again.

This is where I got a helpful surprise: the flat circular end piece is only crimped to the round side piece. I was assuming it was one welded piece, and I would have to tweak the door side to open and close - dragging the side ring with it. Now the door simply "pops" over the bead in the round part, keeping it closed, but opening with a gentle tug.

I again took the silicone sealant and laid a thick bead inside the bottom part of the cap, then clamped it and left it overnight to set up.

Step 3: Painting the "Shell"

I took a sample shell to the hardware store and matched up the red and brass to some spray paint as best I could.

While the door end sealant was curing, I went ahead and wiped down the tube/cap assembly with acetone and laid on several thin coats of the red and left it to cure overnight as well.

The next morning I put on a "mail pick up" flag to make it look more official.

Step 4: Finishing Up the Door

After the silicone set up overnight, I first attached the fixed side of the hinge. I put a "L" brace behind the hinge, with a liberal application of Liquid Nails for good measure to stiffen the area behind the hinge.

On the door, I first drilled a 1-1/8" hole for the primer. It's not really to scale, but I think it makes the "brass" end as acceptable as possible. (It was installed last, after the door assembly was painted.) Behind the hinge and the door itself also needed stiffening, so I picked up a large "T" brace and cut it down to fit tightly to the door. I positioned it as low as I could so the gap was covered as much as possible. It got a good shmear of Liquid Nails as well.

At this point it was ready to paint, so it got a few thin coats of a metallic brass-colored paint.

Step 5: Finishing and Mounting

Jumping a little out of order (letting paint dry) I decided it was a good time to figure out how I was going to mount it to the existing post. This is how I did it for my situation - but there are so many post possibilities that you'll just have to figure out what works best for your situation.

As far as I can tell, these "universal" mailbox mounting plates work with most mailboxes and poles. Mine is welded steel with rails that snugly grab both sides of the plate. The duct is flexible enough that i took a spare steel plate laying around, drilled it to fit the mounting holes in the center of the universal plate, and with the plate on the inside and the adapter underneath - bolted it all together securely.

I applied sealant around the tube end, and installed the door assembly with several small screws to secure it well. I pushed the primer/knob into the center hole and took it out to install to the pole. There are 4 screws that secure the adapter plate to the pole mount and it feels very secure.

(I did trim all those pointy screws poking into the door opening after I took the pics - the mailman will not be injured!)