So I had my first proper welding lesson today, so much fun! Keeping in mind that I had about an hours practice (taking it in
turns between 4 of us) I don't think I did too terrible a job welding the frame together. It's not pretty, but it seems rigid and the frame is pretty damn square so I'm happy with it. I'll grind down the welds next week to make a nice smooth surface or mounting the rails to. I've welded up the bottom frame, and two feet/legs for the gantry. Very satisfying work, and I was really getting the hang of it by the end.
Also been thinking more about the toolchain I want to use with this thing. Some of the features of LinuxCNC are very tempting – particularly the addons that allow proper use of a height probe. I'm just not convinced by having to use a desktop PC with a parallel port to control it all. Putting a force air cooled PC in a milling environment just doesn't seem that sensible, although I am considering a sound-reducing enclosure for the mill so we'll see. I think I'm going to push ahead with GRBL to start with, and move over to LinuxCNC once I've enclosed the mill.