Great 'proof of concept' 3D print... this amazes everyone not familiar to 3D printing!
This needle roller bearing prints as one piece. It has 12 rollers and prints (on a Replicator 2) so the designed in support can be removed in next to no time to leave an easy to spin needle roller bearing.
At the time of uploading I couldn't find anything similar on Thigiverse. The key to it working is the clearances within the design and the designed in support.
TIP: Spray inside from each side with a small squirt of silicone spray to make it spin really well.
Easy print... something to fascinate people with.
On a Replicator 2 print use Raft with 4 shells and 35% fill... don't scale down or the clearances will reduce and it could become a solid block.
When finished remove the support and the designed in support on the underside (that support the rollers) should be quick and easy to remove as they are all attached to a single 'support ring'.