Dead flat light work table?

Resolving this to its most basic properties you want

That leads me directly to polystyrene or polyisocyanurate foam.

What you skin it with is another matter.

Polyiso is much ,more resistant to (celluelose) solvent attack, but is much more expensive.

I've used smaller boards very successfully for building model aircraft on. it stays flat really well

Measure it with a straight stick in every direction, don't need a level. There is a very simple solution: a small pallet. It'll need sanding to get it dead level. Having used one with an added vice as a small workbench I much preferred it to a gapless sheet worktop.

NT

Cement board is pretty weather-proof. Ideal if you are going to build a shower later and use it for your work table in the meantime.

Define what you mean by dead flat, btw.

Interesting idea - thanks :)

Any non flatness will transfer to anything made on it.

A flush door? They are light and stiff and cheap.

But not particularly strong. I was going to suggest a length of kitchen worktop (which can always be left outside if you get caught out by a shower). But the door gives you more width and won't sag much even if supported near the ends.

Depends a bit on what you might be doing. Door would be OK for a lot of carpentry, not so good if you were stripping an engine.

Rather than adjustable trestles, another option is a couple of cheap workmates. Then clamp suitable offcuts of 18 mm ply or whatever in them to provide two straight horizontal edges at the same height on which you can rest your worktop.

My FIL had a small slab path with a couple of dwarf walls at right angles, he made a clever adaptor resting on them which supported his table saw firmly, level, and at the correct height.

Polyiso is being used in new houses nearby. The sheets are laid on the base and the men are walking all over them and using heavily laden barrows. I don't know if the sheets are those 'structural' ones, but some were in over the void a couple of hours after I first went past and there couldn't have been much time to put in any over(under?)all support.

Yup, torsion box design - 1/2" WBP ply would probably be ok. You can make the frame with ply braces as well if you want.

You can use a long straight edge to test for flatness in two axis, then make a set of winding stick you check that the surface really is all in one plane.

See

Yup, sounds doable... or even a side mount jig that hooks onto an edge.

There are also ready made options to do this kind of stuff:

These with a couple of 4x2s will give you a decent surface - but not always coplaner:

Ready made torsion box:

That's actually a rather good idea... I could still face it with ply to get a machinable surface to take track. But you're right - very stiff and very likely dead flat.

Cheers!

Also a great idea. Why did I not think of that...

This is carpentry - I've been inspired by a series of american woodworkers - most have massive workshops, but one guy specialises in using home made benches that have running tracks flushed in to act as a table saw, router table and stuff. If I had a workshop, I'd do the 4x2" laminated to make a 4" thick top (after truing with a planer) - but for now I need portable.

I might even try to make it up as 2 4x4' or 4x3' tops that can be dowelled together when needed.

With my ground, even 4 feet won't sit right...

:)

Thanks :)

Thanks John. I have never heard of these.

I did have something like that in mind for the legs - really like the look of those...

I wonder if that is water resistant - but it gives me some ideas...

Recycled plastic sheets.

If you spin the workmate about the vertical axis as well as moving it from side to side and back and forward (if you see what I mean) you can usually find a secure point, if the surface is not too bad. I used to have to do this on my old and very irregular patio.

If it is really bad, you could modify a cheap workmate by removing the bottom of two legs, and adding a third foot in between them (and still have a system which would fold for storage). On one of mine, each pair of legs is fitted to a cross beam about 4 inches above the ground. You could screw a triangle of 18 mm ply to this, using the "point" of the triangle as the ground contact point. Rounded off a bit, of course. Or a bit of chequer plate if you have some.

Paul has some videos on you tube on their use....

The basic idea is that they allow you to sight one over the top of the other and easily see any twist in what they are sat on.

You can also do the same trick with a couple of parallel battens on the surface and running tight fine thread corner to corner - the threads should just touch but not bend around each other.

I suppose you could make up an ali framed box, and just bolt your ply surface down to it. The wood could be sacrificial anyway - just replace it when it gets too knackered.

Do you have a wall which could act as one side of the work table? You could screw battens or something else such as metal angle to the wall and ensure that is dead level, effectively removing the need for two legs of the table. The other two legs could be adjusted to whatever height gives a completely level surface. The work table would be removable, just resting on the battens (or using temporary fixtures to assist with stability). No reason why a removable panel couldn't be used for your sawing and router work, or maybe use the same idea with wall-fixed battens to take the weight of one side of the saw/router.

I just put a couple of spirit level across. I can even put the digital angle gauge on the levels and get an accurate measure if needed.

My late FIL who was a very fine carpenter did something essentially like that in his last home. Doesn't sound like an option for the OP, but certainly an idea I shall never forget.

here they laid 6" thick polystrene blocks between concrete beams and then covered that with another 6" of poly that they tagged the UFH pipes to.

Then they chucked about 4" of concrete over the lot.

Its very strong is polystyrene of reasonable density.