Carbon vs Bearing vs Stainless steel

Hi, I am building my own printer based on the Wilson II design. Does anyone know the difference between Carbon and Bearing steel? Also out of the following which should I pick for my linear shafts; Carbon (not hardened), Bearing steel, or Stainless steel (I know stainless doesn't rust as fast, but I don't really expect that to be a problem)? Lastly, is it worth the money to get hardened shafts instead of non-hardened?

If you're going to use ball bushings, you need hardened rails. Ball bearings will cut grooves into plain/carbon steel rails.
Since you're early in the design process, I suggest you consider using linear guides instead of round rails and bushings. They cost a little more but the performance is MUCH better and it will be evident in your print quality.

Here's a deal on a quality linear guide: [www.ebay.com]

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Will ball bearings cut grooves into carbon steel rails that have a hardened chrome finish? I have a friend who said he didn't have hardened shafts (only hard chrome finish), and he doesn't have any grooves in his rails. He is also using ball bearings (has been for the past year).

The hardened finish (like your friend has) is what you need for ball bushings.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Okay, good! Is there difference if the shafts are not heat treated, with the hard chrome finish, and the shafts that are heat treated with no surface finish (which would work better)?

If I am not mistaken hard chrome shafts are hardened steel that are then chrome plated. That is the best shaft for linear bearings.