H1 Idler upgrade

A very simple upgrade for the SeemeCnc H1 printer is replacing the idlers for the belts with ball bearings. Using the stock bolts this means we need a sleeve to go from the 1/4" cap screw to the 8mm ID of the bearing.

The bearings are cheap readily available skateboard bearings. Also known as 608 size. Measurements:
22mm OD
8mm ID
7mm height

This is quite possibly the second simplest STL on thingiverse after a cal cube!