Minimum spacing to support MDF (table top)

what material for the stringers would be my question

do you have access to a thickness planer or drum sander? I put my supports every 6 inches but I used particle board and not mdf for my surface.

The thing to look out for is consistency in the milling of big box store boards. You might even look for a local cabinet shop and see if they will take a few bucks to plane your lumber.

I used my x-carve frame thickness to plane down some red oak to the exact thickness and then cut a bunch of 2"x2" blocks and spaced them out under the waste board. So thinking back on it, that would be 4 inches between the blocks if on 6 inch centers.

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It’s a little sturdier and harder.

From web searching, MDF and particle board appear to be close to the same strength, but both will sag if unsupported. I don’t think you are going to have issues with what you are planning. I built mine on about a 12" square with 1/2" thick MDF and have seen no issues over the 4 months since I built it, and really don’t expect to ever have an issue. One thing I did though is glue the MDF to the supports to create a torsion box structure.

In reality the MDF doesn’t have to support much weight. The frame of the XCarve will span your supports and hold it up. So if the MDF sags even 0.001" the weight pushing down on it will be relieved and it will be carried by your structural supports. I would recommend making half lap joints where things cross, rather than long boards going in the X axis (for example) and then a bunch of short boards in Y.

Hope that helps.

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Just a thought,

Here at Inventables and available elsewhere some 20mm x 20mm x 500mm extruded aluminum.
inventables is $4.50. Its aluminum, straight, and should be what you have already in place.

You can cut it to size with a chop saw or hack saw.

Most of all, its water proof, and straight.

Again, just a thought.

I am only suggesting that you use the aluminum extrusions for the support that match what the machine has supporting the 1/2" MDF board now. They sell 500mm,1000mm and 1500mm.

If you were to order the 1500mm length then you could cut this on your chop saw or with a hacksaw.

Then you would not need to cut and plane the 1 x 4 wood to make it flat.

Its not susceptible to warping because of moisture, and it keeps the base of the machine the same height.

That’s all.

I have a 1000 x 1800 shapeoko 2 with a 3/4" MDF supported by the edges and 3 locations in the center.

Hope that helps.

I understand now.

Your just making a workbench not increasing the size of the X-Carve.

Sorry for the confusion.

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Another option, depending on your woodworking tools/expertise, is a torsion box.
I made mine from 2 sheets of 9mm MDF with dividers of 18mm MDF. Flat and strong.

…and another option, this one being cheap and deadens the noise somewhat: Making 500mm X-Carve more "solid"

I might have to try something like that too. While my table top doesn’t flex, the spoil board does. I think it (spoilboard) needs bolting directly to the table top rather than just the 3 aluminium extrusions. (1000mm X-Carve)

I removed the spoil board and supports entirely from my machine. I bolted the Y rails directly to the table top. My Current table top is a modified version of a torsion box and does not and will not sag overtime.

I highly recommend GeoffSteer’s design. As long as the table is built flat, the. It should remain flat.

The biggest problem with MDF is moisture. This season and the next, your spoil board may be fine, but if you get large fluctuations in RH the MDF will quickly start to deform and sag, more and more over time. So support the MDF well (especially if using 1/2") and seal all of the exposed edges/sides of the MDF to help reduce the amount of moisture the MDF can absorb through the atmosphere. This will help keep the table Dimensions stable.

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Personally, I would just stick with the MDF Torsion Box. As long as it is built correctly, you should have no issues.

The other two processes could be a little messy and there is still no guarantee that the outcome will be any flatter than a sealed MDF Torsion box that was properly built.

But that’s my opinion.

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@PhilJohnson I tried to find some info online that discussed the optimal spacing for a torsion box but could find nothing. I ended up setting the spacing to suit my nail gun. All dividers are glued and brad nailed.
The most important thing is building it on a flat surface as any imperfections will be impossible to fix once that second skin goes on.
A few coats of polyurethane will help with any moisture issues.

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If you take care making the torsion box, it will be flat and that’s the importatnt part. Level will depnd on how you mount the torsion box and is less critical. My table is within about 0.3mm of being flat over its entire 1200x1200mm surface but due to an uneven floor, is not completely level.

My stand is not as substantial as yours. Just 90x45 (4x2) all round.
It now has a shelf underneath but needs a drawer or two.

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Thanks for Sharing. I liked her Swan Pushstick. It looks just like a toy my grandfather built for us when we were toddlers. Brought back a lot of good memories.

Personally I would not use her design. IMO I do not believe the wasteboard will be properly supported and will eventually start to sag, especially in humid environments. I did not order the wasteboard and completely redesigned this aspect of my machine. I did not use any of the original base in my design. I placed my machine on a modified torsion box and mounted everything directly to it. Now the Torsion box is the “waste board” more or less.

For your pool table, is it a slate top? If the top is Slate, then it should be nearly perfectly flat. If your machine is rocking on it, then I would assume that the base is out of square. Building the machine on top of the pool table should give you a flat surface to register off of. Even if the top is not slate it should be fairly flat if the table is still a functioning pool table. But i would still verify that the table is flat and possibly reinforce it from underneath as well, this is bc plywood pool tables are not built to support weight on the surface.

Another option is to bolt another piece of MDF to the bottom of the Xcarve making a sandwhich. This will help give you a more sturdy base that is less likely to bow. If you use this method, install some spacer boards (or more extrusion) that will go between the new bottom and the original wasteboard. This should really stiffen up the base and keep it from sagging especially if it is sitting on a flat surface.

How about a Granite top XCarve CNC work table

She seems like a great builder. Not sure why she went with the sides of the machine off the side unsupported. Not the best idea, nor was the musical interlude.

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skip it. There is no way you can control a .25 sheet of aluminum. It will conform to whatever surface you put it on.