Table Base & gantry initial assembly.
W6x16's used for rails.
Gantry is trussed made of 0.75"sch40 pipe, 1/2" round bar, 3/8" round bar diagonals, 1.25"sch40 for the main horizontals which have a 3/4x3/4x1/8 angle welded on for the track for the Y carriage.
Horizontal truss of gantry is bolted to the verticals to allow for fine adjustment, leveling, and for removal if required to move the machine.
Bearings are inexpensive route, 3/8idx1.125x3/8 bolted to plasma cut brackets & they ride on the bottom flange of the W6 (dust sweep should really be in order here, I figured the top flange should protect it somewhat, at least from direct contamination & then with a sweep & cover attached, it should do ok.)
The gantry is pretty stiff, deflecting about .029 under a direct 50# load on the spindle tip. It's a little more than I wanted, but in order to get it down much more, the gantry would have to get to heavy to drive it with the inexpensive steppers . . . I'm trying not to blow the budget here.