MDO for torsion box face?

[Jon Endres]

I'm starting a build of an assembly/outfeed table using the "Paulk" design as some inspiration. I have a sheet of 3/4" 2-faced MDO that I am considering using as a top, with a regular sheet of either birch or radiata pine plywood as the bottom of the torsion box. Should I have any concerns about using the MDO?

[Brian Tymchak]

Not familiar with the "Paulk" design. Generally, no concerns about using MDO but 3/4" material for torsion skins is way overkill for your stated application. 1/4" BB skins would be sufficient.

[Frank Pratt]

Yes, what Brian said. A torsion box a few inches thick with 1/4" skins is incredibly strong & easily would stand up to any loads that assembly or outfeed would put on it.

[Paul F Franklin]

Agree that 3/4 is overkill...unless you are going to put dog holes in it; then you need 3/4. I use a lot of MDO in the shop for jigs and fixtures and even my bench top and am a big fan. You can get it in 1/2" thick too, but I haven't seen it in 1/4, at least not as a stock item.

[Jim Becker]

I'm with Paul...normally, .75" thick material is way overkill for a torsion box structure, but for dog holes and clamp slots a la Paulk, it can be appropriate. Be aware that the paper surface on the MDO can scratch quite easily in my personal experience. It's used a lot for signs because it has a very nice, flat, paintable surface, but it's still a thin surface in most cases. I wouldn't use it for this application without, um...application...of a good film finish to help reduce risk of that damage.

[Brian Tymchak]

Ah, so now that I've learned a bit about Paulk workbenches, my first comment is totally irrelevant. Should've done some minimal research before replying. Interesting construction.

[Phillip Mitchell]

You definitely want a 3/4” thick for a Paulk workbench top. Anything thinner and the dog holes type clamps may not be compatible. I can’t imagine doing any sort of pounding, clamping (to the top itself) or heavier type work on top of a 1/4” thick top, even on a torsion box. 3/4” mdo would be my preferred material for this application...just wish I could get it locally easily.

[Thomas Wilson]

I use the outfeed table as a large work surface. I clamp to it and drive in drywall screws to attach alignment blocks and other temporary setups. 3/4 plywood works best for me.