I am in the planning stages of a homemade cnc mill/router. I heard somewhere that, during ww2, concrete was used as a substitute for cast iron due to a shortage of metals and a demand for machines. I have also seen a few plans for milling machines with concrete beds. So I am planning to cast a steel reinforced concrete bed for my gantry type mill. I plan on using 40*10 cold rolled steel for slideways and nylon blocks with backlash adjustment. Planning for travel as followws, x-2000mm, y-900mm, z-400mm. Spindle is to be driven by 650-2500 rpm bench drill press. I have extensive cnc programming experience but zero electronics. So far im planning on using a stepper motor kit available online. The motors have 200 oz-in holding torque but im not sure that will be strong enough. Most of the rest of the construction will be steel and alu angle and rectangular tubing. Will try and attach a rough design but im not sure if my cellphone browser will be able to do it. There is a lot of gusseting and cross bracing still to add to the design and the spindle has yet to be figured out but the outline is there. any feedback would be greatly appreciated.