Im worried that the torsion box i build wont be precise enough. Im getting the aprts cut at a local woodwork shop, but to save costs im doing the lap joints and assembly myself. Im going to be careful, but once its all glued.. If its not flat enough.. (what is considered flat enough?). I was thinking a backup plan would be to use some self levelling epoxy on it.. As far as i can tell, from reading online then it would be Flat with a capital F.. However most of the discussion re. Epoxy online seems to be regarding levelling beams to attach rails.. Given its not cheap for circa 10kg of epoxy, and if it goes wrong ive got a huge mess.., is it a valid solution to a slightly inprecise torsion box? How do people generally check flatness and/ or fix imperfections? Ive not got a workshop of tools, or a reference table to build on, just a digital level, a circular saw and a hand sander. Table will be 120cm x 170cm. Advice most appreciated before i start gluing!
Levelling epoxy will get you to +0.003/-0" across any given size surface. It's a great option. A better option would be to only put epoxy where rails are gonna go, and only use 15% of the quantity! You may not even need it though. Depends on how level you can get your Y rails to each other. At that point, the machine frame and everything else doesn't matter- you tram your axes to each other and surface your spoilboard to where you get your axes. The only thing that matters is two parallel Y rails. Also, a 1500mm 2040 piece of V-Slot is actually about +/-0.0015", maybe a hair less. You can use it as a pretty good straight edge for shimming, planing, sanding, whatever.
How flat is your dining room floor? That was the flattest surface I could find when I built mine so I did it there and used myself and some landscape pavers as a weight while the glue dried. In the end, I had about a 0.5 mm crown over the 1500mm length.
Our house is a stone one with a very old tiled floor, its super wobbly. Ive got a pair of saw horses, so ill level something up on that.. Maybe in the neighbours garage, i think that is flatter than anything in our house..
