# Torsion Box Core Material?



## Sirnanigans (Apr 3, 2014)

Yes, yes, torsion boxes are EVERYWHERE on the internet. I even found nearly a dozen resources for building them myself. There's still one particularly vague and variable detail though, and that's the material for the core of the box.

I am building a torsion box for a table, probably a 6'x3'6" table. The table is going to be stationary but not fixed, like a dining room table, so I want it to be somewhat lightweight but it's not a priority. My highest priority is price. Building a whole table for less than $250 means pinching pennies, and here's where I want to pinch them.

So I ask this: *What kind of wood should I look for to construct a ~1.5" tall torsion box web on the cheap?* It should be high enough quality to really make an impression and last forever when used as a gaming table.

Thanks for reading, these forums are always extremely helpful.

_EDIT: I should mention that I don't have a table saw to make straight cuts from sheets. I have a crosscut handsaw (and wish I had a rip saw, too) for that job, so cutting plywood or MDF is going to be a major time sink complete with planing and squaring afterwards. I do have a router table and flush cut bits, but the router isn't powerful or expensive enough to trust as a real workhorse._


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## PhilBa (Jun 30, 2014)

Well, you are going to need to cut the braces but cross cutting is not that hard on a TS - use a miter gauge, make a cross cut jig or for sheet good just treat it as multiple rips.

MDF will probably not meet your weight requirements. Plywood might but you'll risk splitting the braces without pre-drilling. Frankly, I'd use plywood for the skins and some sort of pine/fir/hemlock for the braces and stringers. 

One other thing 1.5" tall is not going to give you much of a brace height - that's where the strength comes from. I'd look at 2x1 for stringers with 1/2" ply skins for a total of about 2.5".


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## Sirnanigans (Apr 3, 2014)

Aha. Sawing jigs may very well work. I hate MDF, so I am glad to hear that it's not the top pick.

Many of the boards I can find where I work are warped, and I don't trust any of them. Perhaps playwood is the way to go, as I am willing to pre-drill and expend gratuitous amounts of glue onto this. 

The 1.5" was the core only, so it should be the same as a 2x1, right? I was thinking 1/4" bottom and possibly top as well (gaming isn't too abusive), for my total of 2".


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## Sirnanigans (Apr 3, 2014)

Is pine, fur, or hemlock characteristically straighter, or do 1x2 boards need to be planed flat?


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## PhilBa (Jun 30, 2014)

Generally, it's dimensional meaning they were finished to a pretty close tolerance. Pick boards from the same batch just to make sure and select only boards that are straight for your stringers. You could use plywood for the stringers/braces, just make sure to glue, drill and screw. 

By the way, make sure your assembly surface is dead flat or you will build the box warped. Use shins to tweak to level.

1/4" top may be ok depending on how far it has to span. Also, think about some one pounding the table or dropping something heavy on it. You might want to consider 3/8".


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## Sirnanigans (Apr 3, 2014)

PhilBa said:


> Generally, it's dimensional meaning they were finished to a pretty close tolerance. Pick boards from the same batch just to make sure and select only boards that are straight for your stringers. You could use plywood for the stringers/braces, just make sure to glue, drill and screw.
> 
> By the way, make sure your assembly surface is dead flat or you will build the box warped. Use shins to tweak to level.
> 
> 1/4" top may be ok depending on how far it has to span. Also, think about some one pounding the table or dropping something heavy on it. You might want to consider 3/8".


Unfortunately my supplier is my employer - a home improvement store. Our selection of wood is... less than exemplary. I will select straight boards and take a plan to problem areas, I suppose. I found some that would likely need only a few strokes to straighten.

I am a fairly savvy guy with math and geometry and the like. I would imagine that two straight support beams and a level will make a perfectly flat plane, as long as the level is at the same mark at either end of the beams. Short of that, I can just build a triangle or X large enough to get things started. Gotta love triangles, they simply can't be warped (assuming the sides are straight).

Pounding on the table with hands and elbows is the worst I am worried about. I suppose the VERY worst is dropping my new gaming grid with its sharp corners onto it, which is made with a white oak frame and weighs 8 pounds with the tile background in it. I am the only one who handles that magnificent creation though, and I trust myself. Most importantly, there will be a nice felt surface to the plywood that should help pad the more acute strikes. I personally feel like 1/4 will be fine, but enough advice against it might change my mind.

Speaking of triangles, why not? A crossed pair of straight stringers (as an X) connected dead center with an accurate cross-halving joint is automatically flat. Toss a frame around it by simply lining up the boards with your X and the geometry guarantees perfection. Follow up with some braces wherever appropriate, and you could build the thing on a bean bag chair and still end up perfect. Right?


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