If you are going back to ground up, consider grabbing the QCW for your machine. I think that could solve your issues, but comes at yet another expense.
Seriously considering that. With the cost of plywood it may not be that far fetched financially.
A solid foundation is always best practice. But if cost is a serious concern, I would argue that your original table top may not need to be scrapped. It’s more important that the top be stable (resistant to bending, warping, movement, etc.) than flat. If it is stable, all you really need to do is shim the feet of the CNC to get them all on the same flat plane. Then, flattening the spoil board will take care of the rest and no one will be the wiser as to your imperfect table top.
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Torsion box is all 3/4” MDF on the faces and 1/2” MDF for the ribs on an all steel Kreg frame. I get that stability is more important and this thing is a behemoth of stability. Problem is I think I didn’t build my reference surface flat and level enough to produce a flat top. Looking at the fishing line there’s a diagonal bow that’s close to 1/8” height difference center to corner. I must have built in slight twist and I just can’t trust that top anymore.
I want to build a dead flat torsion box for the challenge of it alone but the next one will be for an assembly and outfeed table for my table saw. I need to get up and running with the CNC soon to fulfill some orders. To that end I decided to stop chasing these gremlins and ordered the QCW with leveling feet. It’s a chunk of change but with my work schedule and hours it will take me as long to complete a new box as it will to get the QCW.
I’m gonna keep the 3/4” Baltic birch I cut for a top and put some leftover 3/4” MDF on top of that. Get it as flat and level as I can and put the QCW on that. I’ll bet I can get that flat enough to not need the QCW but this is going to buy me peace of mind and take a lot of environment and climate factors out of the equation.
Thank you all for the suggestions and jumping in. This is a truly great community and I owe you all a virtual drink.
Hey Terry,
that is always an important thing when assembling a torsion box.
The other day we were discussing how to ensure that the table top you glue/screw together will not be twisted, and what I suggested was:
You may still use a torsion box that is twisted by mounting the Onefinity on it, making sure the feet are all in one plane e.g. by using shims (I would use metal sheets cut out to match the machine’s feet including the holes), and then surface the entire workarea. If you eliminated the twist in the machine by using the shims, you will get a non-twisted workarea, and for the remaining area outside of it, which will remain twisted, you could either leave it this way or remove the material with a hand tool and by using a long straight edge, with the non-twisted workarea as reference.
Another thing I thought of that you can find on some CNC machines, is to mount one of the machine’s feet on a base with adjustable height. Since three points are always in one plane, it’s always only one foot that remains to need to be adjusted.
The QCW Frame
The QCW Frame meets the demand to have a machine that when assembled is immediately ready to use. With the separately available adjustable feet¹, an existing table may be twisted or uneven and if you do not have a table at all, you can also set up and operate the machine on the floor.
However, the QCW frame is rather expensive, and the target audience for a Onefinity is actually people who can build a base for the machine themselves as desired and needed, and therefore do not necessarily need the QCW Frame. For example, many people here want a machine base that allows vertical clamping. And if you think of the money that the QCW Frame costs, there are many things that you could find more urgent to buy, for example a professional dust collector or a vacuum table.
1.) The Any Surface Leveling System provides these inserts with threads that are not part of QCW Frame:
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Thanks for all the tips fellas. I will keep all this in mind for the next one I build. I think the QCW will simplify a lot of this and be one less thing on my mind.
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My QCW frame just sits on my cabinet that I built. One corner, of the QCW, did not touch my cabinet top, so I just shimmed it with a wooden wedge until all was solid. I then did the fishing line test and all looked good.
I put some anchor blocks to stop the frame from moving.
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Thanks for all the input. I appreciate the detail you go into. You have me thinking twice about the QCW. Reading more posts I am wondering how rigid that QCW is and maybe I am trading one problem for another. I was assuming it was ultra rigid but if it can go out of coplanar I am right back to my root cause … a coplanar and level base that stays that way.
I have the Kreg table base, so getting that square, coplanar and level, adding crossbars of 2x4 for extra rigidity, that would give me the platform to construct a new box. Perfecting the reference platform to build on is the bigger challenge …. At least for me.
If I were to make another go at the torsion box, what specs have worked well for people? Plywood vs MDF? 1/2” vs 3/4”? Rib spacing?
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A few of my thoughts on torsion box design and building, I am sure that some will laugh and tell me I am wrong and will be along shortly, but I can only say what worked for me
My woodworker is mounted on a homemade torsion box the torsion box is supported on wall brackets on the rear and left-hand side, there is a support leg made of steel box section bolted to the underside of the torsion box on the front right-hand corner with an adjustable foot at its base, steel being used instead of wood or aluminium as more stable
In my opinion the best material for a torsion box is moisture resistant MDF the best quality that you can find. Plywood is not stable enough it’s a natural product that is prone to warping.
For my base I used 25mm MR MDF when you buy the base check it with a straight edge as if you start off with a bow or warp you will never get it bang on lay the bottom of the box down on some trestles and leave it for a day or so MDF does not move much but everything you can do to help makes for a better outcome, don’t be tempted to lean or stand the top on its edge.
Decide on the height of the torsion part of the box I am sure there may be a calculation that you can do to optimise this my logic says that less is best, so I settled on 100mm
I used the same thickness of MR MDF for the outer and also the torsion grids the strips of MDF need to be cut as consistent as possible if they are more than about .25mm out then they are no good, I had mine cut by a local mill who use a CNC table saw, if you have to store these or move them try to keep them stood up as they will be in the completed box.
Next is torsion grid size I went for twice the height of the grid i.e., 200mm centre line
I assembled the grid using Titebond 3 and pocket hole screws using full length strips for the X axis direction of the grid.
With regards to the Y axis direction cut the length of the noggin’s as accurately as you can and secure them in an offset pattern with the next row of them set halfway between the previous row similar to a brick wall pattern again secure using glue and pocket hole screws
You now have an open box.
Check for flatness and take some time to sand any minor high spots and any glue squeeze
For the top I again used 25mm MR MDF having checked it for flatness and treated it the same as the base I took the decision not to glue the top down onto the torsion box but to only secure it with screws I drilled and countersunk clearance holes for the screws along both the X and Y axis at 100mm centres and secured it down, I mounted the OneFinity checking for level and squareness and spindle tramming.
I secured down a 18mm MDF (not MR as our MR MDF has a layer on each side) sacrificial waste board and the entire cutting area cleaned up with a 0.2mm cut in a single pass which I took as being fairly flat
I have replaced the sacrificial board twice since the reason being a lot of my work is multiple components profile cut so I am a bit hard on spoil boards and I am happy to say no issues with regards to flatness squareness or tramming.
As I say on a lot of my posts, my way may not be the best, it may not be textbook it may not work for everyone, but it’s worked for me, and it’s done with what I consider to be logic and good practice even if it is my logic!!!
D
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Thanks for the detailed response.
I am a classically trained overthinker and and overworrier. That’s a bigger issue than my level and coplanar table 
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You have to appreciate all the options that OneFinity gives us. My set up is in my garage, and I needed a solution that allows me to break it down and move it out of the way if I need to do something else in the garage (like putting up hurricane shutters!). The rolling folding stand with the QCW was as perfect as it comes, and I think only OF had that option when I ordered. I assembled my entire system in less than an hour. To me, that was worth every penny.
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just beware that the qcw frame has an off center work area. there will be 9 inches of waste board in the back you cant reach to machine and 0 inches in the front. this causes clamping issues using the t tracks. its a design flaw. I found out the hard way I didnt recognize this when I purchsed my qcw frame. nice frame but has issues. when you surface the waste board you cant tile your projects unless you use another piece of mdf etc to raise the work piece up or it will not lay flat due to the 9 inches of waste board that is in the rear of the qcw frame that will be raised higher than the surfaced work area of the spoil board. I think the frame is a great option other than these issues i have ran into using mine.
Im gonna machine some new aluminum blocks to offset my rails 4.5 inches to get full use of the t tracks and work surface area. still will have to use an extra piece of mdf under my material to tile projects. or there will be a gap under the material. best i can explain it without use of photos
The monting locations of the y rails needs offset approx 4.5 inches to the rear to center spindle to the work area of the qcw frame.
before I threw away the table you made id shim under my rail mounts or something to get the same affect.
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It’s not a flaw, it’s a user option. Some people want that raised area for more usable table. Some don’t as they may tile and do not want the raised lip. If not, simply cut your mdf at the raised transition 
The choice is the users to best decide how they’d like to use the machine.
how can i use the t trak clamps in the front if my material is say 32 inches square? i cant use none in the front only the rear.
i guess i could repostion my mdf and buy some t track and install the t track under the spoilboard after movie it more to the front but it wont be supported by the frame.
Not messing around this time. Level and coplanar platform to build the new torsion box on. I cancelled the QCW order and accepted the challenge of the torsion box LOL.
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Whoa!! Laser level! We’re getting serious now.
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@terry156 Don’t forget to check for level in an X across the middle. It’s possible to have all four sides level with each other and have a bow in the center. Very disconcerting. One of many lessons learned the hard way.