You can find in this folders, 3 useful bearings for the usual rod of 2, 4 and 6 mm, tested and perfectly working. The external diameter is always 25 mm and fit very well without backlash. The thickness of the bearing is 10mm

*MiniBearing 2x25x10mm
*MiniBearing 4x25x10mm
*MiniBearing 6x25x10mm

Don't rescale you will lose the tolerance between the different parts.
Print with surpport easily removable.
For a good printing try with this minimum settings :
 - speed : 60mm/s
 - layers : 0.1mm
You can find steel rod on ebay.
Enjoy!