You can not use anything but hardened rod for linear bearings, sorry. You can do a search on it and read up for info, or just trust me that people have tried it and the balls always dig into the shaft on anything but hardened shaft.
For what it's worth, your machine is far too big to be thinking of milling aluminum like you are talking about. Cuts will take forever and the machine will flex a lot. Machining marks will be ugly and chatter will be everywhere. A CNC mill like the X3 can be had for a couple grand now and will do the job you want it for. Check out Syil, they have ads here on cnczone.
I am not trying to pop your bubble here, but I think it is important that you hear this so you dont make a big mistake.
colin |