What do I need to build an re hydraulic excavator?

[Rimrock]

Concerning tools, it's often a typical situation that first time buyers purchase too small lathe and mill with the intend to save money. But it's not a good deal to end up with equipment that are not usable. I would recommend to not go any smaller than the size of the Sherline lathe (long model) and mill.
I've had a TIG welder earlier, but used it not often enough to really get the hang of it, it's quite demanding to operate compared to other methods IMO. Now I just got my MIG and the thinnest wire, use it for spot welding of steel.