Hard board is like MDF with a polished smooth side.
I agree with Bill also, he has a good point.
Alden, You have given new life to the Teak slat idea, I’ll get on my band saw and custom cut them out. And drop the Z Gantry.
I will probably need longer bolts, however. Bill is right. I’ll pick up the 5/16’s at Lowes
I think you made a wise choice. I have often wondered what I would do if mine started rubbing. There isn’t much space there. When you bolt it down use washers under the table and check it frequently for tightness.
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Yep, thank you so much for all your advice, this goes for all forum contributors. Where would we be without the helping hand of our peers. So just cut out my teak risers, now I will need some longer fasteners. Will post pics after the facts.
Thanks again! 
JENN
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I think in the long run adding something better than MDF for the table top would benefit you. You would then put the MDF spoilboard on top of it. I’m still two weeks or so out so I haven’t actually assembled my table yet but my plan is to use 1 1/8" Advantech subfloor. It’s designed to shed water and moisture. The 1 1/8" might be over kill, 3/4" is the standard used around here for building houses. The MDF spoilboard would go inside the 1F so you can flatten all of it with a spoilboard bit.
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Don’t know if it helps but, locally we call that material “Masonite”.
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Ahaaa! I knew that “B” had a name: Masonite
WikiPedia… Masonite is a type of hardboard, a kind of engineered wood, which is made of steam-cooked and pressure-molded wood fibers in a process patented by William H. Mason. It is also called Quartrboard, Isorel, hernit, karlit, torex, treetex, and pressboard.
Thanks Phil. 
How thick is your tabletop? It looks to be 1" mdf? That will most definitely flex and bow. My mdf tortion box is not long for this world for the same reasons as it is not well supported.
Sorry to hijack your post Jenn…
BJ, I also have a MDF torsion box and mine seems to be holding up okay so far. Do I need to start worrying?
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Mine is 3" thick but I am not supporting the power for all the way around which is why it domes on the middle
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Hi,
I don’t think so. But the torsion box would need to have nearly the size of the whole table top then. If the corners are not supported by the torsion box, a MDF table top may have its corners dragged down by the weight of the machine, exactly where it has its feet. MDF is dense, heavy, expensive, but not rigid.
Thanks,
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Hi,
it may be that if you put something under the feet of the cnc in order to raise it, you do not eleminate the cause of the problem. You may just remove a symptom.
It seems that either your table top is sagging: the corners seem to be dragged down. The corners have to bear the weight of the whole machine since it’s where the feet of the cnc are positioned.
MDF is more dense than plywood, hardwood or particle board. But MDF is not very rigid. It is definetely not as rigid as hardwood or plywood.
I would not use it as a table top unless you have a very sturdy construction under it, and the latter would need to support all(!) the surface of the table top, including the corners, in order to prevent them from being dragged down by the weight of the cnc’s feet.
A torsion box below would need to have nearly the size of the whole table top then.
Question is, do you have such or anything wide and sturdy under the table top; at least the pictures here do not show it.
Generally if your table top is sagging and the corners are dragged down, you will deteriorate the attainable accuracy that your cnc offers, since you cannot calculate how this dragging and sagging falsifies your results. A reliable and flat surface is always part of a reliable cnc machine (even if you can buy the OneFinity CNC without one). And I mean the overall mounting surface, not just the workarea surface.
On the other hand your MDF table top could have soaked humidity and this may have caused the surface raising. MDF is very susceptible to swelling. Wood is also, but not to the same degree in every direction, because of grain direction and also of wood type.
So if this is a swelling issue because of moisture, I would temporarily remove the cnc and make the table top flat again. And maybe seal it then.
Thanks,
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Yeah, it is 1" MDF. I hope the risers do the trick.
JENN
Therein lies the beauty of the QCW frame. The machine sits ON the table rather than being integrated INTO the table.
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Yes, or better, therein lies the beauty of the Onefinity cnc. You do not necessarily have to mount it on a flat frame or tabletop.
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Yep! And that opens up a whole world of possibilities. Think about someone with a laser attachment having the ability to do custom laser work on large restaurant tables.
I am definitely gonna have to switch out my TableTop (MDF), should I opt for Plywood, or what might be a better replacement for the MDF. Needs to be available in 4’ x 8’ sheets.
Thanks!
JENN
Jenn,
I agree with @Aiph5u. It looks like you have a decent amount of overhang around the outside of your table top which has “Potato Chipped” under the weight of the machine over time. Blocking it up may temporarily solve the issue, as it may come back again in the future with more sagging.
If it were me, I would switch over to a plywood top as the laminations would give rigidity in the plane of the weight of the machine. I would also use my 1F to mill out some cool looking brackets out of 3/4" (or thicker) ply to add to the corners to help reduce the possibility of the sag coming back and give the top a little more rigidity where the machine mounts land.
Adding spacers wouldn’t be a terrible idea either as I have thought of this as well. The tight area under the axis sketches me out some times when I notice it when the machine is running as it could be a pinch hazard or a place where parts/tools could get jammed into. The reason it sketches me out is that I used to maintain CNC lathes/mills and while rebuilding one, I ended up getting a finger caught in a spindle while running a breaking program. It only took 30+ stitches and a skin graft to repair the damage. Luckily enough I have 95% use and feeling of the finger.
I’m sure you will research and implement the best solution for your problem and I look forward to seeing your resolution.
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Always referred to masonite as beaver board.