Originally Posted by
coherent
Forget about any cnc router for steel unless you spend big big money to buy or build it. You can cnc steel with a plasma cutter, mill or laser but not a router setup. It sounds like you are fairly new here and your question is kind of basic and your budget is pretty small for anything very large. If I were you, I would search the forum and do a lot of reading. Find a router or plans that fit your needs, capability, cost etc, then go from there with something that has been tested and proven. Engineering a machine from scratch and trying to determine how ridged it will be depends on many factors based on each component and material. If you were a structural engineer then I don't think you'd be asking the questions you asked, so research here and elsewhere on the web and copy or buy something that you know will work.