Sturdy and Fast all Steel CNC , my first build

[Neale]

Well, that's an obvious way to set up the epoxy on the gantry. You know, the kind of "obvious" that's only obvious when someone else says it!

I've been kicking ideas around in my head for the last week or two about how to align the Y rails for "constant spacing" if I put them on the top and bottom of the gantry bars for my new design. Easy enough to lay the gantry on its back and use epoxy to level the Y rails on the front face, but I couldn't work out how to do it where the fixing faces for the rails were not in the same plane. Easy enough if you have an accurate level surface to put the gantry on and do one rail at the time but how do you generate that initial level surface in a home workshop? So use one of the level surfaces you created when you used epoxy to set up the X rails! As I say, it's obvious once someone else has pointed it out...

In practice, any idea of how much out of true a typical length of, say, 50x50 or 80x80 steel tube would be? Are we talking about a mm or two, or significantly less than that? How much does the epoxy thickness vary, in other words?