The Stovebolt Site Forums The Shop Area The Tool Chest Plywood for a toolbox

Planning on building a tool box/chest for the back of the truck. Plan is to weld up a light weight metal frame and skin with 3/8 plywood that’s sealed with low gloss polyurethane or spar varnish. Any suggestions on the exact plywood to buy. I was thinking marine grade but not available locally. Have considered a cabinet grade but don’t know if it’s upto the occasional rain event even with the appropriate coating.

Use will be to carry small suitcases, tools, truck fluids, etc when on the rare road-trip.

Thanks for any and all input.

RonR

Ron,
Since you are building the frame, have you thought about covering the box with aluminum or fiberglass sheets?
You could add additional ribbing to increase the backing for the material.
Harold

Harold, I have considered both of the good options you suggest. Sadly I just prefer the arguably less appropriate wood and like the look of dinged, weathered plywood. That new furniture look will be fine, but in a couple years it’ll be better.

The regular pressure treated plywood should work very well, it lasts for many years out in my neck of the woods with full exposure to a lot of rain and snow. Without paint. If you don't care for the greenish tinge, some paint will cure that. I don't know how that stacks up to "marine grade" but it's got to be just as good (without being directly covered in salt water).

When I did my boat floor I used exterior grade plywood . Exterior grade is close to marine grade from my understanding marine grade has the inner ply’s with no voids being the difference .

When I was building houses (some time ago) here in S.C. I used a tongue and grove flooring underlayment and it is some tough stuff. Back at that time, 2016 they gave me some additional incentive to try it. Dang tough stuff but can't remember the name. I had it rained on for days and never no problem. I even stood a piece of it up at a 45 degree angle against my shop and it was a loooong time before it even begin to sway. You may want to check in on what local builders are sub flooring with??? Just a thought.

Marine Grade means all of the plies are knot/void free and it was assembled using waterproof glue...with that said it will still rot if left to the weather.

Any exterior grade plywood should work just fine for a tool box that's going to have paint or urethane put on it.

You could make the entire box out of wood and use brass screws to fasten it together so they don't stain the wood over time like steel would.

Mike B

Also bronze screws are available that are harder than brass. Good boat building websites and online catalogs sell materials and have discussion forums on material selection, finishes, sealants and hardware.

There is an exterior plywood called MDO that I used to build my truck dog carrier when I ran sled dogs that has a resin soaked fiber facing on it. It is rugged, holds up well, designed for exterior signs, and has a clean look….the local lumber yard can order it or it migh be available at a chain building g materials store.

It was a nice flat sheet better than pressure treated or thinner underlayment or exterior plywoods that seem to warp and twist.

Here is a link - good description:

https://www.hunker.com/12316947/what-is-mdo-plywood

I designed the box with aluminum angle for the corners and infilled with this MDO ply. It looked great, the box held up after years of rain, sleet and snow, and I applied a marine grade finish.

Excellent suggestions and exactly what I was hoping for. Still in the thinking stage and I do have a habit of over thinking things.

RonR

Whatever you decide to use for your box just insure it doesn't set flat on the bead as water will collect underneath. You could use some short legs or blocks from dense plastic or composite deck material.