Assembly Table with Torsion Box

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Project by clin posted 12-30-2016 06:10 PM 11913 views 18 times favorited 10 comments Add to Favorites Watch

Here’s an assembly table I built earlier this year. There are two main points of interest. The table itself was built by laminating 3/4” Baltic birch plywood. The big advantage to this is you can create mortise and tenon joints just by leaving voids in the piece to create the mortises.

Similarly, you can oversize the lengths of internal piece to create tenons. It results in a very stiff structure. This table has no discernible flex in it at all. You raise one leg a fraction of an inch and another leg comes up the same amount.

The main point is the torsion box top. I was just looking to have a flat stable top. In my case I made it from 1/2” MDF. I created the webs by using half lap joints. This was very quick and easy to do using a dado stack. Note: these joints are NOT glued. Joints between webs on torsion boxes do not carry loads. The key to a torsion box is a good joint between the top and bottom skins and the webs.

In order to have a flat table, you have to have something flat to built it on. So what I did was joint a bunch of 2×4’s and then plane to thickness (on edge). So this gave me a bunch of 2×4’s that were very straight. I temporarily attached two short ones across the table frame and then laid long ones on those. I used winding sticks to get these flat. I also checked with a level.

Once I had a reference surface, I laid a sheet of MDF on it as the actual build surface.

I did mount a vise to this, so added blocking to support it. I recessed the vise so it wouldn’t sit too far below the top of the table and to put one face flush with the side of the table. I trimmed the table with maple, but added a second piece over the vise to act as a wood jaw. By recessing the vise, this piece runs the whole length.

I know there are other styles of vises that wouldn’t have require this effort, though for some reason, that escapes me now, I did want one of those.

I used a piece of hardboard as the top and recessed it below the maple edge. I would not do this again, the hardboard just isn’t heavy enough to lay perfectly flat, so I ended up screwing it down in a few places. This negates any advantage of the edge boards holding the hardboard in place. Also, no matter what, you just get places where the hardboard and edge board aren’t flush and sliding items off the table can catch on the maple edge board.

So, sometime I’ll remove this hardboard and trim the maple flush to the MDF top, then put a new sheet of hardboard on top that goes all the way to the edge.

One last point, my shop is a converted garage bay and there is a step in the concrete. To make use of this area, I needed the table to straddle this step. So two legs are shorter than the other. While a bit odd, it is actually kind of nice because I can effectively change the table height based on which side I stand on.

-- Clin

10 comments so far

View trevor7428's profile


266 posts in 1974 days

#1 posted 12-30-2016 07:01 PM

Very nice, I wish my torsion box turned out this nice

-- Thank You Trevor OBrion

View ohwoodeye's profile


2589 posts in 4166 days

#2 posted 12-30-2016 07:13 PM

Very nice….....should serve you well.

-- "Fine Woodworking" is the name given to a project that takes 3 times longer than normal to finish because you used hand tools instead of power tools. ----Mike, Waukesha, WI

View Rich's profile


6567 posts in 1602 days

#3 posted 12-30-2016 07:58 PM

That came out great. Nice work.

-- Half of what we read or hear about finishing is right. We just don’t know which half! — Bob Flexner

View pottz's profile


14928 posts in 1997 days

#4 posted 12-30-2016 08:56 PM

that’s a great looking bench and something every shop needs,nothing more frustrating than trying to build on a uneven table,enjoy it.

-- working with my hands is a joy,it gives me a sense of fulfillment,somthing so many seek and so few find.-SAM MALOOF.

View LittleBlackDuck's profile


6560 posts in 1833 days

#5 posted 12-31-2016 12:27 AM

Great use of the torsion-box concept, clin. You will/should find that the top will be ”as solid” as any heavy/hardwood timber.

I think torsion-box use is grossly underrated and have found that even 3mm MDF will provide a light but solid performing piece of construction.

-- If your first cut is too short... Take the second cut from the longer end... LBD

View clin's profile


1128 posts in 2009 days

#6 posted 12-31-2016 12:57 AM

Great use of the torsion-box concept, clin. You will/should find that the top will be ”as solid” as any heavy/hardwood timber.

I think torsion-box use is grossly underrated and have found that even 3mm MDF will provide a light but solid performing piece of construction.

- LittleBlackDuck

It is certainly nearly as stiff as a solid top. But you wouldn’t want to beat on it with a sledge hammer. Being MDF skins, you could break through. And while a torsion box is lighter than the equivalent solid material, this is still quite heavy. I think the top alone is about 150 lbs. But an equivalent thickness of solid material would be 500 lbs or more.

I do agree that a torsion box is seemingly magical in how stiff they are. Though if you understand the engineering behind it, it all makes sense.

In this case, lighter wasn’t the goal, it was flatness I was after. Being able to rip the webs to a very accurate width allowed for building something very flat. It actually took more time to make the build surface from the jointed 2×4’s than it did to make the actual box. But, now that I have this table, I have a nice flat surface for building on in the future.

-- Clin

View oldrivers's profile


2469 posts in 2579 days

#7 posted 12-31-2016 01:15 AM

nice table looks great.

-- Soli Deo gloria!

View JimWestbrook's profile


2 posts in 1524 days

#8 posted 12-31-2016 11:34 AM

Wow! This table looks perfect! Great work Clin!

View Timthemailman's profile


336 posts in 3789 days

#9 posted 01-03-2017 02:23 AM

Did you say assembly table or dinning table. Very Nice

View Woodknack's profile


13550 posts in 3393 days

#10 posted 02-10-2017 08:47 AM

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