Finalized Linear Bearing Plan

Ok, I have been thinking, and overthinking, the linear bearings. I have been unhappy with the ones that I have tested out before and finally have figured out what I want to do. I have not been happy with the idea of running hardened steel bearings on aluminum. I didn't want to mess with steel angle tracks because it is not as easy to work. I also wanted to keep the cost down. Here is the cheapest and easiest to work with plan that I have been able to develop.

This design uses 3/4" steel electrical conduit (EMT) for the rails.. It is straight and not expensive. It will also wear much better than the aluminum. A 10 foot piece was $4.33.  The 5 foot pieces I bought today are under $3 a piece at the borg. I could have gotten cheaper but I didn't want to mess with putting full 10 foot pieces in my car or driving around shopping.  If I were going with a more powerful router, I might consider using a thicker wall pipe or larger diameter tubing but I can't see it for a small router.

The bearings will be mounted on 3/4 in aluminum angle. This could be modified with larger angle to accommodate larger diameter tubing but I already have plenty of 3/4 in.  I ordered the screws today also. For the ones between the angles, I figure that 40mm will be plenty long and 25mm for the ones that stick out on top and bottom. I went with M8 screws. They are the right size for the 608 skate bearings without slop and will be stronger than smaller screws.  I also ordered lots of washers so I can shim the bearings to ride centered on the rails. I might put more bearings on each carriage mainly to make it more solid in case the angle starts flexing. I will see how it works once it is put together. I am also going to think about adding a shield around the bearings to keep it clean. Maybe some wipers on the ends.

The rails here are drawn to scale. The 3/4 in conduit is 0.931 in. OD. I plan on attaching it to the conduit with screws every 3 or 4 inches to tie the rails and support together. I might notch the support rail for the conduit to rest in but I will probably just add an epoxy fillet to secure and support the rail.  This rail assembly will have a wider backing plate behind it for adjustment.

If you would like the model for SketchUp, here is a link.