Torsion Box Design

I am obsessing over torsion boxes while I await my Journeyman. I watched several build videos and found it rather difficult to find recommendations on dimensions for the web, so I set about doing some math and settled on a top that will measure 47" x 67.5" x 4" when finished and will sit on top of a Kreg 44" x 66" frame. I drew it up in Sketchup Make 2017 to better visualize it.

  • All made from .5" MDF
  • All parts 3" high
  • Each row of short ribs is offset by .5" from the one next to it, so I can more easily brad nail the ends of all the ribs. That’s why some of the rows have equal dimension cells and some have slightly different sizes on each end.
  • Web will go between 47" x 67.5" x .5" MDF skins, cut a little proud and flush trimmed for final

So someone else doesn’t have to spend the time I did, here is a flat image of the design. I’m a new sign up, so I can’t upload the Sketchup file as an attachment. When I can I will add it. DM me and I’ll happily email it to you.


Beautiful plan but to play devil’s advocate, you don’t really need it! Onefinity is different than most machines. If you set it up correctly the a torsion box is overkill. I have the Journeyman X50 and it’s on 3/4 plywood and MDF in a 2x4 frame with some supports. Started as a woodworker then I added 2 feet to one side. My machine is super accurate and once I trimmed nothing has needed adjustment. I have a QCW and have never installed because I keep waiting for a reason, has not been one! My advice, go simple and if you have a need for more, retrofit or upgrade. Same goes for routers vs spindles. Just my opinion.


Thats great! No joke, almost exactly what I built for mine. Only I used half inch plywood instead of mdf for the torsion Box. I assume you will be putting some real wood under MDF so that your machine has something to bite down into?

Love it!


Thanks for the input on stability. I was on the fence about building it. I decided to go with it mainly because I’ve never built one and I have several more weeks before the Journeyman arrives so it’s also an exploratory project. Let’s just say I tend to over do it :grinning: My fall back position will be the double sheet of plywood move.

Great point on the MDF accepting screws as well as plywood. I’ll put a plywood top skin on it. I think it would be fine for screwing down the CNC. It’s t track and spoilboard attachment that are problematic long term for strength I think.

I need an assembly table so maybe I do MDF for that with what I have and re-think using plywood for the 1F.

Seriously thanks guys. I can see an aw crap moment avoided when it comes to screwing things down.


Working on a torsion box similar to yours. I think I see pocket hole screws; did you use them just on the perimeter or on the interior webbing as well? Did you use brad nails at all? How did the regular wood glue work out on the plywood edges; I’m using plywood but am considering PLA glue. Appreciate any input.

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No screws anywhere. Just brad nails and glue. I staggered the short ribs so I can Brad nail the ends rather than toe nail them. Wood glue should be fine for the whole thing.

The real picture is the table @gsatt built and does have pocket screws. Mine is the drawing. I don’t have anything against pocket screws, I just chose not to use them on this project.


Yeah, so for the one I built i did use pocket screws just as an easy way to hold the cross-sections down to the bottom. All joints were half inch dado cut halfway through the material to fit together snugly. Everything was glued with wood glue. For the top piece I then covered everything in wood glue and put the top on and just clamps and brad nails.
In each corner where the onefinity would line up I glued up some thicker pieces of wood inside for the mounting hardware to sink into.

It was almost definitely overkill but it made me happy.

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Being happy is what it’s all about LOL. I admit to spending way too much money and time on things but it makes me happy and that’s all that matters to me. This is all a great mental challenge and puzzle for me. Hoping it keeps the grey cells sharp for years to come.

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Thoughts on sticking with MDF for the top and putting 1/4” plywood underneath for the screws to grab or reinforce the spots under the MDF where the 1F base will screw in? Mainly I don’t want to spend money on a sheet of Baltic birch when I have all the MDF cut and ready to rock.

Thanks guys. I’m going to give it a try this weekend.

I am just a little worried about MDF plus 1/4 inch ply… It may be fine but MDF holes may be easily stripped… Have you considered doubling up some 1/2 inch or 3/4 inch ply pieces under each location screws would attach? Maybe 8x8 inch squares would be good to line up?

This is what I did on mine using my sketchup model to demonstrate… I have 1 inch of plywood for the onefinity to secure to… the top layer is 1/2 inch mdf.

That’s the move. 3/4” ply reinforcements in the corners. Where can I get the journeyman 3D model? I’ll add that in on mine to figure out the placement for the left rail.

I like the grommets for the the cables. Nice touch.

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Hey Terry,
There is a Onefinity model on Grabcad. Not sure if it is a Journeyman.



Why not just put some blocking/backing at the connection points. Cut down a 2x6 or a couple 2x4. For those unfamiliar with the term.

“Blocking, often called backing or sometimes grounds, also refers to pieces of wood or other material that run between wall studs in order to provide support and attachment sites for mounted hardware or trim such as cabinets, shelving, handrails, vanity tops without a cabinet underneath, bathroom towel bars, mouldings”

You can see it in this time-lapse of my build. Login • Instagram

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Thanks! I found it in the 3d warehouse… i think i just searched cnc and tabbed over to models . I’ll see if I can find it again and share a link.
I had to make a few adjustments to it because I think the model was for the woodworker

Watched the time lapse. See what you mean by blocking. Easy enough to add that on the corners. Plenty of scrap 2x4 laying around. Thanks for pointing me at that.

My love for consistent and accurate cuts is in full bloom today. :grinning: Box frame, long ribs and short ribs all done. Cut plenty of extras to account for eventual slip ups.


I’m awaiting my Jman but concerned with the MDF “bite” as well - considering through bolts(through the full torsion top), fastened below with adequate washers and lock nuts.

One cool thing I did to my tension table is add electrical plugs on all four sides. it made it a lot easier to manage power.


I made my torsion box from 1/2" poplar ply because that’s what I had lying around. I made mine 52" x 52" x 7" high with the ribs spaced approximately 6" apart. Some of the spacing got thrown off a bit because I made a 28"x 18" deep removable panel to accomodate vertical milling. This had to be made slightly off center because the CNC isn’t centered either.

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