Can I get a better definition of a torsion box?

Sorry for the late reply. We have bailed out the basement and now the dehumidifier is working overtime.

What @RyanPowell said is true - 4x4’s are a PITA to work and it’s just cheaper / easier to use 2x4 studs. That said, here is a file showing an exploded view of what I built - use it - don’t use it - use it for inspiration - circular file it. Whatever, but I thought it might help!

CNC Table Exploded.pdf (368.7 KB)


Sorry to bring this back up but I bought 3/4 inch mdf, I was hoping to cut it in half since they would both be 49 inchesx48 inches but because of the xcontroller I got to add 10 inches so I’ll land up needing two sheets. Anyways I bought 2x2s to make the torsion box, I don’t have a table saw, so I was wondering is it really necessary to trim them? Will It be bad If I don’t?

may I ask how you did the spray foam? did you sandwich a board on top and spray each cell? or just sprayed it in and cut level? how many cans did it take?

I just sprayed it and cut it level with a regular hand saw. It might have taken 3-4 cans… I had one or two on hand and I think that one of them didn’t work thus my uncertainty of how many I did use.


Thank you for the info! One more question did you just glue the top mdf on or also screwed it on?

I screwed the hell out of it. :grinning:

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good to know! I wasn’t sure if it was bad to screw the top down and have all the countersunk holes. I guess I will do the same! Thank you!

I have a piece of thick (1/2"?) black rubber matting on the surface that covers the countersunk holes and also offers more grip for the X-Carve to sit on.

Damn this was the whole 1 can… you sure it was only 4? XD

Your mileage may vary! But oy - that does suck! You could always get some solid foam, cut it to fit the openings and then use a much smaller amount of spray foam just to keep the foam pieces in place?

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If using solid foam block cut to shape, one glue that work very well is Polyurethane wood glue. It foam slightly if misted with water and glue really well. Since it foam a little you dont have to have super precise foam inserts to begin with.
Its sticky as hell to scrape off btw… :wink:

The main purpose of a torsion box “innards” is to lock the top & bottom surface together and minimising the chance of them move/bend relative to each other. Same principle applies to a wing spar or an I-beam.

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I used 3/4" Birch Plywood on either side of the framing. Even made a few drawers for the bits… This table is incredibly heavy…I had to lag 2x4’s to the wall to support the sides and just needed 1 2x4 to on the outermost leg. Its incredibly strong, easy to make. I get great accuracy, …___ good enough by my book.

After 6 cans and multiple hours of trimming and sanding

With nice jig! I’m sure glad mine is all done!


Who, hoo! Looks great!

Thank you soooo much for your kindness and willingness to help me out and sharing your experience! It really helped me out! I only wish I had a local Ikea that helmer unit looks really good! :slight_smile:

I am glad that I could pay it forward and help somebody else. I have had so much help from others in this forum - especially in the last three days when I was ready to pull my hair out and quit!

Happy carving!