These are files for a prototype 3d printable replica of the commercial IGUS brand RJM-01-08 8mm plastic linear bearings / bushings. These are still a work in progress. I have had one prototype run of the 8mm hole version in bridge nylon, but they were a little to tight. I have heard reports that PLA might work, but they also might stick. A material with a low coefficient of friction is best. IGUS now has an iglide tribo filament that is designed for this purpose, so it probably would work well. But i have not tried it yet. EDIT 7-9-16: I just received a sample pack of the IGUS Tribo filament so i will print some soon!
I have used solidworks to create an 8.1 and 8.2 inside diameter hole instead of the standard 8. I just printed one in PLA at 8.1 ID and it came out great tolerance wise! Each printer may have differences in accuracy.
I designed these as an experiment in a lower cost bearing solution for my homebuilt lulzbot mini project. Currently i am using 6 of these prototypes quite well underneath the build plate for the y-axis. You can check out the lulzbot forum or visit my blog (see my profile for a link to my blog). I have also designed modified lulzbot mini parts to be able to use LM8UU ball bearings instead. I will upload those files as a new "thing" soon.
I have also uploaded a new 8.1 and 8.2 file with the filleted / beveled edges removed so you can have more surface area on your printer bed. I figured it was a good idea for a part this small, the more surface area on the bed the better. The Igus iglide tribo filament seems to print a little extra (.3mm) in every direction. Thus i have created a tribo adjusted STL file for you to print in the white I180 iglide filament. I found the yellow J260 tribo filament too finicky to work with.
also a note for anyone who does not know. RJM-01-08 size bearings are NOT a drop in replacement for the LM8UU bearings. There is a slight difference in diameter. the LM8UU bearings i believe have a 15mm diameter and the RJM-01-08 have a 16mm diameter. doesn't sound like much, but it is a big difference for a 3d printer.