Joining aluminium extrusion lengthways

[EddyCurrent]

Done. Holes drilled right through, 8mm rod with dome nuts at the end and captive channel nuts in the 45deg extrusion.
Counterbores to allow a socket to be placed over the dome nuts was cut on the cnc router, it cut it like butter.
I was going to put 6mm aluminium top on it but to keep cost down I found some spare 10mm waterproof melamine faced plywood.
Also after using supported rail for the first time I can safely say that even though it works great for this application I would not use it myself for building a cnc machine.