Re: Where to start? 3040 parts upgrade
If you can decide on how to control the machine the rest of the pieces of the puzzle will begin to fit together. If the budget is limited I'd go Linuxcnc. Well actually I'd go Linuxcnc regardless but that's based on my own prejudices and lack of experience with the other options Options are many, even Centroid has a hobby market offering these days.
I like the idea of having a standalone CNC controller so I don't need to have a computer set up in my workshop
A Google search for "offline cnc control(ler}" will turn up some interesting things. Reliable documentation for these type of controls seems to be a bit hard to find and help from other users will be even harder to find. Interesting but probably not the best choice for getting your feet wet.
The spindles normally available to fit that mount are bit high on the rpm and low on torque for metals but people make it work.
btw: I run Grbl occasionally. It has limitations but I don't find it truly horrible. My implementation has stop/pause/resume and jog using a pc sender.
Anyone who says "It only goes together one way" has no imagination.