The beginnings of my fixed gantry router/mill. 40 hours of fabrication in the books since last Friday. Most tubes and hollows to be filled with epoxy granite after stress relief and machining. Still need to do the columns, but pretty close to done with the welding. Proud of my baby 110V welder for surviving with this super heavy wall steel-- greatly aided by a 300-400 degree F preheat, though. Low power makes it hard to weld over the tacks and keep it looking nice, but overall I think good for minimizing heat, and penetration is enough for this stiffness-critical machine. I started out doing a lot of stitch welding to minimize heat, but after working on the frame and feeling vibrations move through the structure, I decided to fully weld everything except the long, heavy rail mount bars, but using more narrow stringer beads than weaves where possible. Preheating thick steel plus proper weld sequence makes this take about 10x longer than it would otherwise!
Tip: granite countertop scraps are readily available at the used building materials stores. $5, and flatter than about anything short of a blanchard ground top or actual surface plate.
Thanks for all the help so far; great forum.