[hagemeyp]

I am building my X axis for a fixed gantry/moving table design. The base is 40"x36", with the linear rails running on the 36" length side.

I have two rails, what is the optimum spacing, that is distance apart to prevent racking and to support the moving table most efficiently?

This will be for soft metals and woods, planning on using a Bosch 1HP spindle. Frame is 100% 80/20 15 series extrusion.

I suspect the answer may differ based upon the flex of my table if any. Currently I'm planning for a homemade ply/mdf spoil board with T-slot rails.

[ger21]

What kind of bearings? Do you have an image of the design?
Lots of variables involved here, but generally, the farther apart the better.
Are you driving the gantry from both sides, or from the center.