[Tomthegiant]

I have tompson 1" linear pillow block bearings. They run on round shafts. What is the best shaft to use? I have been told 3 different things by 3 different people? I'm comfused! My X axis rail is going to be 54" long. What material will have the proper runout? I was also told not to go too soft on the rail? HELP!!

[schbrownie]

You really only have one option: Steel shafting (I'm assuming that you don't need corrosion resistance)

Here are the main types of shafting:

1.) Feather Shafting (Ceramic Coated Aluminum) - ONLY for use with plane bearings (i.e. Pacific Bearing's "Simplicity" bearings). Think of this shafting as an "M&M" it has a relatively thin coating which gives it a nice hard shell which works great for plane bearings, but not for ball bearings.
2.) Steel Shafting - your general purpose shafting used in most applications. You'll want somethign that is "case hardened". If the shaft isn't hardened, then the balls will wear little tracks in the shafting... esentially ruining it.
3.) Chrome-plated Steel - Same benefit as steel shafting, but with added corrosion resistance... most companies are going away from this issue because of ROHS issues.
4.) Stainless - Same benefit as steel shafting, but with added corrosion resistance.

There are other types of shafting.... but the above 4 should cover any do-it-yourself project.

As for where to get it...
If you stick with brand name shafting from a reputable company (I usually get either QuickShafts from Thomson or Rc60 shafting from Pacific Bearing), you'll be just fine. You can either get the shafts directly from the company or through your local Motion/Applied/Kaman branch. I've also had some luck going through a catalog house like Grainger/McMaster-Carr/Misumi. Misumi is great if you want something done to each end of the shaft (threaded, drilled & tapped, stepped down, etc..)

Good Luck,

~Jon