How To make a casing for bearings.
Step 1: First Off
First of all, measure the diameter of the axle you want to use, the diameter of the bearings and an ambiguous size of houseing (bigger than the first two dimensions obviously).
Step 2: Laser Cutting
Using a laser cutter, cut out 5 plastic cylinders, three with holes the size of your axle, two with holes the size of your bearing diameter. The former must also be the thickness of your bearings. These are stuck together using plastic glue in order so the ones with the bearing diameter are separated by the three others. The bearings are placed in like shown.
Step 3: Washer
A washer the size of the bearings is placed in and the casing sealed by further cylinders.
Step 4: Axle
Your casing is sealed and an axle can be placed through.