Zero's Build Log - My slow descent into insanity...

Ok,

Thanks for coming to take a look. Not sure if I'll ever reach the end, but I'll at least give it a very good try.

Tiny bit of background... about 6 years ago I decided that building a CNC would be a good idea. After a couple of months, a friend sold me on the idea that I'd get better use out of a CO2 laser. The appeal was instant and the fact that the machine didn't need to be anywhere near as robust helped greatly. It was a pretty big affair, I'd designed it so it could take 1/3 of standard sheet of ply or mdf, and took up a sizable chunk of my garage. It got good use.
Jump forward 6 years and the novelty of my laser has long worn off and I'm now back on the CNC path.

I'm not too sure of the cutting area size I'm after just yet, and that will be decided over the next couple of weeks.

Anyway, I've probably forgotten most of the research I did all those years ago... but it's slowly coming back, please bear with me if I ask inane questions.

Talking of which... 2 To be starting off with.

1. Up to what sort of size machine is it considered OK to use a SFU1204 for the Z axis ballscrew?

2. What are the general feelings on linear rail spacing on the gantry? I've read somewhere that you should be looking for a minimum of 150mm, which seems quite a lot to be honest, well for a smallish machine anyway. Looking at some of the other build logs, specifically the ones that use 9045 extrusions in an L configuration, I can see that that spacing is impossible. So is it just a case of whatever the maximum you can achieve given the design you go for?

Cheers

Chris