I screwed down the linear shaft and im a little more encouraged by the alignment.  Round shafts have a tendency to turn and will cause racking problems.  Shafts need to be fastened down, or held.  I just screwed a metal screw through the side.

I have decided to change gears slightly and focus on a fixed gantry build similar to a microcarve cnc or sienci mill one.  I like the box aspect but the construction was terrible.  The millright m3 also suffers from poor construction.  

Panels need to be fastened VERY SECURELY.  Avid cnc uses barrel nuts, and microcarve uses a plate bushing.  A 3d plate bushing could work.  Perhaps for ease of use keep outside profile rectangle and just mill a pocket to receive it.  Either 3d printed or cnc wood plate.  Idea is more pocket depth/ interference fit, plate inside and outside?  Microcarve has EXCELLENT construction and I want to merge that with the sienci box idea.  

The other idea is to use c-beam or other v-slot as the main gantry for the cnc box.  Print NC has shows tapping/ prepping 2x3 steel beam isn't so bad but with a novel 3d printed marker/jig it can be manipulated intelligently.  

In terms of keeping this cheap the ideas I to pursue: 

- 1/2" conduit pipe with pex bearings

- 1/2" round steel tubing with bronze bushing

   This is probably the most sure fire, cheap build.  

Goal is 100ipm in aluminum at 1/8" depth and 1/4" bit.

Will either be 8mm lead screw, or belts, nothing nicer.

3d printed bearing blocks.

Aside, the Root cnc looks cool.  Classic v-bearing formation using a nice 3d printed chassis.  Square tubing is the way to go.  I was wondering if mini v wheels, or just the bearings would be a good option on square tubing.  The problem now is, its a very slippery slope to Chinese mgn rail.