Have finally found some time to put into a table.

I saw a slat top welding table using RHS, 30 years ago, walking past an open doorway of Uni Adelaide workshop one afternoon, and thought to myself, 'self: I gotta build me one like that one day' (thinking of the clamping possibilities), and not having to move a steel plate which in my current situation of limited access down and around the narrow side of the house and up 6 or 7 steps, would be a serious issue.

I got the trolley base complete with wheels for $30 at a factory auction about 3 years ago. It had a couple of triangle frames on top, and was used for moving chipboard/melamine sheets. It's open C , 4mm wall, plenty good enough for the purpose at hand, given the cost and it being an existing construction; otherwise RHS would be the go. Two of the ends were cut down lower than the other for reasons unknown. So I had welded the offcuts back on a few months ago.

Today I levelled the floor with some offcuts, using a laser, 1 mm discrimination was no problem. Wanted to have a level starting point, to then reasonably establish equal heights on the 4 corners. Ended up with 0deg in all directions including diagonals, using the Stabila electronic spirit level, so good enough, particularly over only 1.2m length. 0deg is nice to see of course, but alway have to bear in mind the inherent precision/error, so always a good idea to swap the level around 180 deg to cross-check. 0.1 degree over 1.2m is 2.094mm, so '0 deg' is of course an 'estimate'.


So I then used the laser to establish tops for the 4 corner posts, and angle grinder action to trim down. The laser worked really well, often it was easy to get the line breaking over the very top of the leg, and the square when checking the 'shadowed' side ( see pic).

The important flatness will be the co-planarity of the top RHS rails - for which I have a 'cunning plan'. As there will be some inherent amount of not true flat in the heights of the 4 corner post tops, despite the measured degree of level, I plan to make a 3 layer sandwich, consisting of the 2 main side to side rails , the main surface members, then 2 more side to side rails on top of those, clamped up for tacking, it should be reasonably flat.

Cut some 90x8mm flat bar to act as supports on top of the legs. These will completely cover/close the leg tops. I was thinking of bolting down the 2 main RHS to these plates, so that the whole top could be taken off , if I ever need to move it somewhere else/fit through a doorway/ or if I bowed it )... But unless I change the spacing, a top (front to back) RHS rail will cover the access hole I was planning to put in the side to side support rails. So welded it will be.

I have some RHS is 75x50x3mm offcuts from my shed build ( as per pic) for the top rails, but I am thinking I may as well go 4mm as I have to get more anyway (14 top rails in all).
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