A custom bearing generator, prints fully assembled!. Use it to produce a tapered roller bearing of any size.
For common bearing sizes try here or here.
Updated to include a section feature, use it to inspect the inside of the bearing.
Full Disclosure:I have had trouble printing this purely due to the first layer. No matter how I tweak or remove things like skirt, brim and first layer height the first layer always sticks to itself. Once the print is finished I've then attempted to separate the components while still painfully hot.