OK - no answers - so I will pitch in.
If you are buying a length of threaded stock, you will need to cut it to the length you need - so you need a hacksaw. Go to Sears or your local Home Depot ot Lowes - they will hook you up. Buy a good one - the price usually reflects the quality, but not always - I would not buy the $0.98 special they have in the bargain bin. Get a few 24 tooth or 32 tooth blades for metal cutting and remember that the blade is directional - put it in the frame with the teeth facing away from the handle. It will only cut in the push direction. As you push the blade, apply a bit of downward pressure, then kind of drag it back to help remove the small chips from the teeth. Once it is cut (after you take a break) you will be left with a somewhat ragged edge - hence the need for a file. I would skip the file and buy a 4.5" grinder annd use a flap disc (on the grinder) to flatten the end of the shaft and remove the ragged edges. A flap disc looks like a bunch of pieces of sandpaper glued to a disc (that's pretty much what it is) and they are very controllable and cut smoother and cooler than a grinding disc although they are a bit slower to remove large amounts of material.
Now - there you have a length of threaded shaft that is the length you wanted, but you will need to be able to turn the end down to fit your support bearings, right? This is where you need access to a lathe. Got any buddies that have a lathe?
Is this the kind of answers you were looking for?